Current Status, Knowledge 

Gaps, and Research Needs 

Pertaining to Firefighter 

Radio Communication 

Systems 

September 2003
Current Status, Knowledge 

Gaps, and Research Needs 

Pertaining to Firefighter 

Radio Communication 

Systems 

FINAL REPORT 

September 2003 

Prepared for: 

National Institute for Occupational Safety and Health 

1095 Willowdale Road 

Morgantown, WV 26505 

Prepared by: 

TriData Corporation 

1000 Wilson Boulevard, 30th Floor 

Arlington, Virginia 22209 

Patricia Frazier, Project Leader 

Robert Hooper 

Brian Orgen 

Nicole Hankin 

James Williams
NIOSH Firefighter Radio Communications 

TriData Corporation i September 2003 

TABLE OF CONTENTS 

ACKNOWLEDGEMENTS ...................................................................................III

EXECUTIVE SUMMARY .................................................................................... VI

Introduction.................................................................................................................... vi 

Methodology.................................................................................................................. vi

Communication Issues.................................................................................................viii 

Technology Summary..................................................................................................viii 

Conclusion ................................................................................................................... xiv 

CHAPTER I: INTRODUCTION.............................................................................1

Scope of Work ................................................................................................................ 1 

Types of Radio Systems ................................................................................................. 1 

Communications from Inside a Structure to the Outside or Vice Versa ........................ 3 

Firefighter Radio Communications Problems ................................................................ 4 

Organization for the Report ............................................................................................ 5 

CHAPTER II: METHODOLOGY...........................................................................6

Determination of Critical Areas of Interest .................................................................... 6 

Literature Review ........................................................................................................... 7 

Fire Department Communication Issues Review ........................................................... 9 

Knowledge Gaps Analysis.............................................................................................. 9 

Recommendations......................................................................................................... 10 

CHAPTER III: FIREFIGHTER COMMUNICATION ISSUES ..............................11

Technical Issues............................................................................................................ 11 

Human Factors.............................................................................................................. 16 

Applicable Standards and Regulations ......................................................................... 18 

Experiences From the Field .......................................................................................... 19 

Communications Problems in Firefighter Fatalities ..................................................... 27 

CHAPTER IV: STRUCTURE COMMUNICATIONS ISSUES .............................29

Communication Problems Inherent in Structures......................................................... 29 

Risk to Firefighters ....................................................................................................... 35 

Radio Spectrum Considerations.................................................................................... 36 

CHAPTER V: CURRENT TECHNOLOGY STATUS, KNOWLEDGE GAPS, AND 

RESEARCH NEEDS ..........................................................................................43

Ultra Wideband............................................................................................................. 43 

Mobile Area Networks.................................................................................................. 50 

Channel Coding, Interleaving, and Encryption ............................................................ 57 

Power Line Communications........................................................................................ 59 

RF Distribution in Buildings Using Heating and Ventilation Ducts ............................ 65 

Alternative Frequency Bands........................................................................................ 67 

Electronic Status and Firefighter Location ................................................................... 71 
NIOSH Firefighter Radio Communications Table of Contents 

TriData Corporation ii September 2003 

Bi-directional Amplifiers.............................................................................................. 71 

Smart Antennas............................................................................................................. 73 

Spread Spectrum........................................................................................................... 75 

Other Technologies....................................................................................................... 76 

General Recommendations........................................................................................... 77 

Summary of Recommendations.................................................................................... 79 

APPENDIX A: PRIORITIZED PROJECT ISSUES .............................................82

APPENDIX B: FIRE DEPARTMENT COMMUNICATIONS – EXPERIENCES 

FROM THE FIELD..............................................................................................86

Austin, TX .................................................................................................................... 87 

Bellingham, WA ........................................................................................................... 88 

Boston, MA................................................................................................................... 89

Boulder, CO Rural Fire Department............................................................................. 90 

Brighton, CO................................................................................................................. 91

Charlotte, NC................................................................................................................ 91

Chicago, IL ................................................................................................................... 92 

Clark County, NV......................................................................................................... 93 

Dallas, TX..................................................................................................................... 94 

Detroit, MI .................................................................................................................... 95 

Everett, WA .................................................................................................................. 95

Fairfax County, VA ...................................................................................................... 96 

Gettysburg, OH............................................................................................................. 97 

Los Angeles, CA........................................................................................................... 98 

Milwaukee, WI ............................................................................................................. 99 

Phoenix, AZ.................................................................................................................. 99

Pittsburgh, PA............................................................................................................. 100 

Portland, OR ............................................................................................................... 101 

San Antonio, TX......................................................................................................... 102 

San Diego, CA ............................................................................................................ 103 

San Francisco, CA ...................................................................................................... 103 

Schaumburg, IL .......................................................................................................... 104 

Springfield, NJ............................................................................................................ 105 

Wichita, KS................................................................................................................. 106

GLOSSARY OF TERMS AND ABBREVIATIONS...........................................107

Terms........................................................................................................................... 107 

Abbreviations and Acronyms ....................................................................................... 108 

MASTER REFERENCE LIST...........................................................................111

BIBLIOGRAPHIC REFERENCES BY SUBJECT AREA.................................140
NIOSH Firefighter Radio Communications 

TriData Corporation iii September 2003 

ACKNOWLEDGEMENTS 

TriData Corporation acknowledges the invaluable contributions of the following 

individuals in the preparation of this report. This document would not have been possible 

without the assistance of the many technology experts. We thank them for their 

knowledge, insights, and contribution to this study. 

Contact / Contributor Company 

Vincent Coli Vice President of Sales, Æther Wire 

Louis Hanson President, LH Enterprises 

Patrick Houghton CEO, Æther Wire 

Jack Jarboe Vice President, Product Development, Grace Industries 

Brian Kibler Senior Account Manager, Motorola 

Dr. Peter H. Krawarik Independent Management Consultant 

Nader Moayeri NIST Information Technology Laboratory 

Richard C. Meyers Director of Communication Networks, 

System Planning Corporation 

Santiago Moreno Vice President, Portico Architects 

Dr. John Newbury Power Communications Research Group, 

Open University, Manchester, England 

Dr. John Orr Professor of Electrical Engineering, 

Worcester Polytechnic Institute 

Winston Rice Consultant, RF Engineering 

Lance Rosen President, Plexeon 

Dr. Robert Scholtz Professor of Electrical Engineering, University of Southern 

California 

Dr. William C. Stone Leader, Construction Metrology and Automation Group, 

NIST Building and Fire Research Laboratory 

Hal Walls Vice President of Sales, Transtek 

Mike Worthington Corporate Vice President and General Manager, Motorola 
NIOSH Firefighter Radio Communications Acknowledgements 

TriData Corporation iv September 2003 

In addition, we thank the fire-rescue personnel and communications experts throughout 

the country who were willing to respond to technical and operational questions and 

requests for information. We thank them for their time, their candor, and their insight. 

Contact / Contributor Affiliation

Reade Bush Firefighter/Paramedic, Cherrydale Volunteer Fire Department 

Arlington County, Virginia 

Gary Wilks Communications Technologist, Austin Fire Department 

Austin, Texas 

Frank Snyder Assistant Chief of Operations, Baltimore Fire Department 

Baltimore, Maryland 

Bill Boyd Assistant Chief, Bellingham Fire Department 

Bellingham, Washington 

Ken Gustafson Division Chief, Communications, Bellingham Fire Department 

Bellingham, Washington 

Peter O'Rourke Superintendent of Fire Alarm office, Boston Fire Department 

Boston, Massachusetts 

Jeff Webb Assistant Fire Chief, Boulder Rural Fire Department 

Boulder, Colorado 

Bob Parker Fire Chief, Greater Brighton Fire Protection District 

Brighton, Colorado 

John Schildknecht Assistant Chief, Broward County Fire Rescue 

Broward County, Florida 

Jeff Stern Battalion Chief, Castle Rock Fire and Rescue Department 

Castle Rock, Colorado 

James Burke Deputy Chief, Charlotte Fire Department 

Charlotte, North Carolina 

William Carter Supervisor, Office of Communications 

Chicago, Illinois 

Jim Wilson 

 Communications System Manager, 

Southern Nevada Area Communications Council 

Clark County, Nevada. 

David Kinney Captain, Fire Dispatch, Dallas Fire Department 

Dallas, Texas 

D.L. Millaway Assistant Chief of Operations, Dallas Fire Department 

Dallas, Texas 

Abner Garrett Chief of Communications, Detroit Fire Department 

Detroit, Michigan 

Bill Harp 

 Firefighter/Driver, Detroit Fire Department 

Vice-President, Detroit Firefighters Association Local 344 

Detroit, Michigan 

Jeff Coffman Deputy Chief, Support Services, Fairfax County Fire Rescue 

Fairfax County, Virginia 

Wes Rogers Lieutenant, Communications, Fairfax County Fire Rescue 

Fairfax County, Virginia 
NIOSH Firefighter Radio Communications Acknowledgements 

TriData Corporation v September 2003 

Contact / Contributor Affiliation

Daniel Shoup Firefighter/EMT, Gettysburg (OH) Rural Fire Department 

Gettysburg, Ohio 

Tom Jones Chief, Glen Echo Fire Department 

Bethesda, Maryland 

Lou Amell Chief of Communications, Las Vegas Fire Department 

Las Vegas, Nevada 

Martin Enriquez Captain, Communications, Los Angeles Fire Department 

Los Angeles, California 

Matthew Partlow Deputy Chief, Support Services, Loudoun County Fire Rescue 

Loudoun County, Virginia 

CJ Walker Communications Manager, Memphis Fire Department 

Memphis, Tennessee 

Douglas Holton Division Chief of Operations, Milwaukee Fire Department 

Milwaukee, Wisconsin 

Steve Souder Director, Emergency Communications Center 

Montgomery County, Maryland 

Bob Oliver 

 Deputy Chief, Dispatch and Deployment, 

Phoenix Fire Department 

Phoenix, Arizona 

Leif Anderson Captain, Deployment, Phoenix Fire Department 

Phoenix, Arizona 

Peter Micheli Fire Chief, Pittsburgh Fire Department 

Pittsburgh, Pennsylvania 

Dave Sprando 

 Assistant Fire Chief, Emergency Operations, 

Portland Fire Department 

Portland, Oregon 

Mike Schmidt Battalion Chief, Portland Fire Department 

Portland, Oregon 

Alfred Castro District Chief, Communications, San Antonio Fire Department 

San Antonio, Texas 

Rodney Hitzfelder Deputy Chief of Operations, San Antonio Fire Department 

San Antonio, Texas 

Susan Harris Communications Manager, San Diego Fire-Rescue Department 

San Diego, California 

Bruce Cartelli Division Chief of Operations, San Diego Fire-Rescue 

San Diego, California 

Paul Chin Chief of Communications, San Francisco Fire Department 

San Francisco, California 

Richard Sheola Township Administrator, Springfield Township 

Springfield, New Jersey 

Roger Sutherland Deputy Director, Stafford County Fire Rescue 

Stafford County, Virginia 

Mike Rudd Deputy Chief of Operations, Wichita Fire Department 

Wichita, Kansas 
NIOSH Firefighter Radio Communications 

TriData Corporation vi September 2003 

EXECUTIVE SUMMARY 

The National Institute for Occupational Safety and Health (NIOSH) commissioned this 

study to identify and address specific deficiencies in firefighter radio communications 

and to identify technologies that may address these deficiencies. Specifically to be 

addressed were current and emerging technologies that improve, or hold promise to 

improve, firefighter radio communications and provide firefighter location in structures. 

Introduction 

One of the most significant problems facing firefighters within a structure on the 

fireground is the ability to communicate reliably between the firefighters themselves and 

between the firefighters and the command post or communications center. In an ideal 

world, firefighters would be able to communicate with one another and the command 

post at all times, regardless of where they are or what they are doing. However, this is not 

the case. Firefighter radio communications to, from and within structures can be 

unreliable, thereby compromising the safety of firefighters on the fireground. 

Over the past decade, incidents involving firefighter injuries and fatalities have 

demonstrated that, despite technological advances in two-way radio communications, 

important information is not always adequately communicated on the fireground or 

emergency incident scene. Also, the events of September 11, 2001, and other emergency 

situations in recent years have highlighted the need not only to improve firefighter radio 

communications, but also the communication systems available to law enforcement 

personnel, emergency management officials, and other public-safety responders. 

The continued incidence of firefighter fatalities where communications are cited as a 

contributing factor as well as the industry-wide lack of consensus on the appropriate 

frequencies to use in fireground communications have prompted NIOSH to more 

thoroughly investigate fire communications and the problems associated with 

communications within, as well as into and from, structures. 

Methodology 

To begin the project, the team members compiled a comprehensive set of 

communications issues that affect radio communications in the fire service from several 

sources – an initial literature survey, knowledge of the project team members, and 

discussions with fire service leaders, NIOSH project team, engineers, and others. Team 

members refined this comprehensive set of issues with NIOSH project personnel to 

identify critical issues that could be addressed by improvements in radio 

communications. A prioritized list of communication and personnel location problem 

areas was developed. In general, the primary focus was clarified to be the identification, 

status, and research recommendations for technologies that could improve in-building 

communications or provide firefighter location within structures. Furthermore, the effort 

was to focus on the radio communications and radio location problems found in large 

structures such as high-rises to include radio transmissions into and out of the structure to 

the command post. Buildings such as these present the most difficult communication 
NIOSH Firefighter Radio Communications Executive Summary 

TriData Corporation vii September 2003 

problems because of their floors both high above the ground as well as basement levels. 

The list of the high priority topics is shown in Table 1. 

TABLE 1: PRIORITY TECHNICAL AREAS AND RELATED TOPICS ADDRESSED IN STUDY

Area Example Issues 

Accountability 

• Integrating Personal Accountability Systems (PAS) with 

communications 

• Electronic accountability 

• Automatic vehicle location 

• Electronic command boards 

Communication Planning and 

Coordination 

• Through building (into/out of) 

• Underground 

• In building 

Monitoring Firefighter Welfare 

and Location On-Scene 

• Role/responsibility of dispatchers 

• Use of field communications units and communications 

coordinators 

• Remote monitoring 

• Vital signs 

• Location 

Reliability 

• Line-of-sight limitations 

• Underground (subways, parking garages) 

• Confined space rescue 

• Communication into and out of buildings (especially high rises)

• Intermittence 

• Communication coverage/dead spots 

Interference 

• Building construction and materials (such as concrete, metal, 

and Lexan) 

• Radio propagation through fire, heat, and smoke 

• Cell phone towers (e.g., Nextel) 

• Terrain 

Unsuitable Equipment • Frequency band unsuitable for structure/ground penetration 

The first phase of the project was an extensive literature search for research and product 

information. The literature search covered a wide variety of government, engineering, 

and scientific databases. The Internet was also used to identify current products as well as 

the abundance of unpublished research posted by various companies and universities. 

The next phase of the project included two areas: identifying communication problems 

experienced by fire departments and investigating the current state of technology research 

and development. This research was used in the third phase of the project to identify gaps 

between the problems and issues of firefighter communications and the technologies to 

address these issues. 

In final phase of the project, recommendations were made for areas of research, which if 

completed, could lead to improved firefighter communications in structures. The 

technologies identified in this phase included current applications, potential applications, 

and how these potential applications could be relevant to firefighter communications. 
NIOSH Firefighter Radio Communications Executive Summary 

TriData Corporation viii September 2003 

This phase is addressed in Chapter V, “Current Technology Status, Knowledge Gaps, and 

Research Needs”. Past and current research is described as well as important issues 

remaining to be overcome if the technology area is to be feasible for firefighters. 

Communication Issues 

Communication problems commonly encountered by firefighters (and others) can be 

broadly divided into two categories. First are mechanical or technical issues related to 

unsuitable equipment, system design, inadequate system capacity (too much radio 

traffic), and building construction, among others. The second category of problems 

relates to human factors. 

Fire departments consistently have problems maintaining effective communications while 

operating in large structures, such as high-rise office buildings and apartments, and 

warehouses. Similar issues exist in structures with a large number of windows (or areas 

of glass) with reflective coatings. Communications from areas below grade (e.g., 

basements, parking garages, subway systems, tunnels) tend to be uneven. For the typical 

home, communications are generally not a problem. The technical issues associated with 

the physical structures themselves (building materials, height, etc.) are discussed further 

in the body of the report. Communications problems encountered by fire departments are 

discussed further in the body of the report. Solutions currently used by fire departments 

range from increasing the number of repeaters to migrating to trunked communications 

systems. 

Human factors, such as radio discipline, training, and tactical decisionmaking, also affect 

firefighter radio communications. These factors, while not technical issues themselves, 

adversely affect communications, especially when combined with technical and 

equipment issues. These issues, while not under the scope of this report, are discussed as 

background in the body of the report. 

Technology Summary 

The literature search identified a number of technologies that could contribute to solving 

firefighter communications problems. Some of these technologies can be used as 

standalone technologies while others are technologies that enhance performance of 

wireless links. Mobile area networks (MANet), ultra wideband (UWB), bi-directional 

amplifiers (BDAs), power line communications (PLC), medium frequency (MF), very 

low frequency (VLF), and radio frequency over heating and ventilation materials (RF 

over HVAC) all can be used standalone to build a communications system. Smart 

antennas, spread spectrum modulations, channel coding and interleaving, and automated 

electronic status systems are enhancing technologies. 

The ideal technology would provide robust in-building firefighter communications 

without equipment setup or equipment beyond personal communication devices (e.g., a 

handheld radio, personal tag, or the like). For providing a practical communications 

system, this technology does not yet exist. Current firefighter communications suffer 

from inconsistent in-building performance and may require additional equipment such as 
NIOSH Firefighter Radio Communications Executive Summary 

TriData Corporation ix September 2003 

repeaters. Untapped technologies provide other opportunities, but have limitations as 

well. VLF signals have been used to penetrate hundreds of feet through the earth in 

mining applications but the band is so narrow it can carry only one analog voice channel. 

MF through-the-air-signaling was tested in England as a means of communicating with 

firefighters in high-rises. This application used antennas that were looped around the 

entire building, making the antenna size a serious drawback. Furthermore, neither VLF 

nor MF has spectrum allocated for this use. A MANet does not require any infrastructure, 

but it does require that a firefighter always be with in range of a sufficient number of 

other firefighters who act as a network of repeaters. In practice, this may be impossible as 

firefighters may be out-of-range of each other in high-rise stairwells or building 

basements. Other technologies have similar issues. 

The next best choice to provide robust in-building fire communications would be one that 

couples personal communication devices with standard infrastructure found throughout a 

building (e.g., ac power lines and telephone lines) and little or no portable infrastructure 

(e.g., repeaters). Such a system would require some setup to interface the personal 

communication devices with the infrastructure. Using a PLC system would require the 

firefighters to plug a wire access point (WAP) into the building ac outlets to connect to 

the building’s ac power lines. It may also require a portable range extender to placed as 

needed. A MANet may require additional fixed wireless nodes (similar to a repeater) to 

enhance its range. 

Another choice would be one that couples the personal communication devices with 

specially engineered, permanently installed building infrastructure. BDAs and RF over 

HVAC are examples. If these systems are in place and designed correctly to give the 

firefighters the coverage required at the frequencies required, they work well. 

Using these criteria, the top technologies potentially suitable for firefighter 

communications are shown below in Table 2. A summary of each of these technologies 

follows. A complete discussion of these and other technologies investigated is presented 

in Chapter V. 

TABLE 2: SUMMARY OF STANDALONE TECHNOLOGIES WITH POTENTIAL TO IMPROVE INBUILDING RADIO COMMUNICATIONS

Existing Structure 

Technology Built-in 

Infrastructure 

Required 

Modifications 

Required 

Portable Add-on 

Equipment for 

System 

Enhancement 

Limitations 

Potentially 

Applicable 

Enhancing 

Technologies 

MANet — — 

• Fixed wireless 

nodes 

• PLC wireless 

access point 

(hybrid system) 

• Network size 

(number of radios) 

• Wireless range 

• Smart Antenna 

• Spread Spectrum 

• Channel Coding 

• Elec. Status 

UWB — — 

• To be determined 

based on outcome 

of FCC final 

rulings 

• Current FCC 

restrictions 

• Smart Antenna 

• Spread Spectrum 

• Channel Coding 

• Elec. Status 
NIOSH Firefighter Radio Communications Executive Summary 

TriData Corporation x September 2003 

Existing Structure 

Technology Built-in 

Infrastructure 

Required 

Modifications 

Required 

Portable Add-on 

Equipment for 

System 

Enhancement 

Limitations 

Potentially 

Applicable 

Enhancing 

Technologies 

PLC • Uses existing 

ac power lines — • Range extender • Range 

• Smart Antenna 

• Spread Spectrum 

• Channel Coding 

• Elec. Status 

MF 

• Uses existing 

telephone 

• Uses existing 

ac power lines 

— • Undetermined 

• Limited research on 

in-building 

propagation 

• Spread Spectrum 

• Channel Coding 

• Elec. Status 

BDA • Cable, 

antennas 

• Installation of 

cable, 

antennas if 

not built-in 

— 

• Pre-installation 

required 

• Frequency must 

match that of fire 

department 

• Smart Antenna 

• Elec. Status 

VLF — — — 

• Narrow frequency 

band limits 

usefulness 

• Channel Coding 

• Elec. Status 

RF on 

HVAC • HVAC ducts 

• Modification 

to existing 

HVAC 

— 

• Pre-installation or 

modifications 

required 

• Duct size must 

accommodate/pass 

frequency used by 

fire department 

• Elec. Status 

STANDALONE TECHNOLOGIES

MANet 

Mobile area networks could provide firefighters with voice and data communications as 

well as supporting radio location technology. MANets for commercial applications is a 

field of intensive research and product development. 

In a MANet, each firefighter carries a networked radio. As soon as two radios are within 

range of each other they form a network over which voice and data can be sent and 

received. As more radios move with in range they automatically join, too. If two radios 

are out of range of each other but on the same network, the networked radios between 

them relay the voice and data from one radio to another until the destination is reached. 

National Institute of Standards and Technology (NIST) has demonstrated this networked 

radio approach to communication and location on its first responder test bed. [189] A 

MANet can also include the use of wireless access points to a local area network (LAN) 

such as the HomePlug LAN (described below) to provide range extension into especially 

difficult coverage areas. 
NIOSH Firefighter Radio Communications Executive Summary 

TriData Corporation xi September 2003 

There are no regulatory issues with MANet but there are technical areas to be addressed. 

Currently, quality of service measures (e.g., the time delay from source to destination) 

and communications capacity degrade rapidly as the network adds radios. Extensive 

research is needed to improve routing protocols to address this and other issues. 

Ultra Wide Band (UWB) Communications 

UWB technology addresses in-building communications and locations needs. UWB can 

propagate better through materials and is degraded less by multipath than narrower band 

communications techniques. 

This is a field of intensive research because of its in-building propagation characteristics 

and the high data rates that can be achieved. For communications, the majority of the 

research is directed at using UWB as the wireless link technology in LANs such as 

MANets. 

The major barrier to this field is regulatory. The FCC has restricted both the band and 

transmitted power level resulting in severely reduced range and data transmission rates. 

The fire service should evaluate this technology, develop requirements, and encourage 

the FCC to implement rules so that fire services needs can be met. Despite this barrier, 

UWB holds much promise. 

Power Line Communications (PLC) 

A PLC communication system could provide improved firefighter communications 

wherever power lines run. There are two types of PLC, HomePlug and Access PLC. Both 

use standard ac power lines for propagating high frequency (HF) signals. HomePlug is 

the only power line LAN standard used within structures and products are widely 

available in stores. There are several proprietary Access PLC standards in the trial stage 

competing to deliver Internet service to end-users. 

Standard HomePlug devices provide the ability to quickly setup a fully functional LAN. 

One available device of particular interest is a wireless-access-point-to-HomePlug 

interface. In this type of application, the HomePlug network is used for range extension 

of a wireless network. Firefighters equipped with a MANet communication system could 

carry these devices into a building with them and plug them into ac receptacles as needed 

to provide coverage in areas where they are out of range of the MANet. Their radio 

communications would be carried by the ac lines to other identical wireless-to-HomePlug 

interfaces plugged into other areas of the building and where firefighter MANet radios 

would be able to receive and relay the communications. 

HomePlug devices do not have regulatory issues, as HomePlug is an accepted standard. 

There are technical issues, however. The ability of these devices to provide range 

extension for a wireless communications system such as a MANet needs further study. 

Studies to-date have been technology demonstrations for home use. These have found 

that a percentage of the ac receptacles do not support adequate network performance. 
NIOSH Firefighter Radio Communications Executive Summary 

TriData Corporation xii September 2003 

This effort needs to be expanded to cover additional structure types and their ac 

distribution schemes. 

Alternative Frequencies (MF and VLF) 

These frequencies are not currently used for firefighter communications but are used in 

underground mines for voice communications because of their unique propagation 

characteristics. 

The MF band has been used in underground mines because of its ability to couple with 

conductors in tunnels and propagate for several miles on the conductors. In this system a 

base station takes exterior communications (e.g., a phone system), converts it to an MF 

radio frequency signal and couples it onto a conductor such as the ac power lines. Miners 

use portable radios and wear portable antennas built into a vest or worn bandolier style to 

receive and send voice communications. 

Frequencies in the VLF band can propagate through hundreds of feet of earth. The entire 

VHF band is about the same bandwidth as a single trunk radio channel, which severely 

limits the capacity for voice and data communications. One practical use of VLF is as a 

one-way emergency evacuation pager to miners. The transmitter and antenna can be 

located on the surface and still reach miners equipped with portable emergency receivers. 

VLF based systems have been used to locate miners below ground as well but the 

inherent lack of location accuracy may not provide performance sufficient for firefighter 

applications. 

These technologies’ applicability to firefighter communications and location need to be 

tested as their use has been limited to underground mines where the propagation is 

heavily dependent on the tunnel characteristics. In addition, commercial developments in 

this area appear to be at a very low level as the bulk of the research and testing was 

performed over 10 years ago. There may be spectrum regulatory issues as these bands are 

currently allocated for other uses. 

TECHNOLOGIES USING BUILDING INFRASTRUCTURE

Bi-directional Amplifiers (BDA) 

BDAs provide improved in-building communications. This approach installs cable and 

interior antennas for distributing radio signal throughout a building to provide extended 

in-building coverage. They are difficult to retrofit into existing buildings, costly to retrofit 

or include in new construction, and require special RF engineering expertise when 

designing each installation, as each installation will be unique. BDAs also require 

periodic maintenance to ensure the system continues to function as designed. 

These systems have been installed in a large number of buildings and face no technical or 

regulatory issues. Use of them as a standard firefighting tool has been resisted because of 
NIOSH Firefighter Radio Communications Executive Summary 

TriData Corporation xiii September 2003 

implementation costs. Local jurisdictions are reluctant to require them by code, as they 

must compete with other areas for business. A nationwide or regional approach should be 

investigated requiring these systems in new construction. 

RF Distribution Using HVAC Ducts 

This approach could provide better in-building communications. It takes advantage of 

existing heating and ventilation ducts as RF waveguides for distributing radio signal 

throughout a building. It would potentially provide a low cost method for distributing 

radio communications analogous to BDAs. 

For this approach to work, the ventilation system must be modified to enable RF signals 

to bend around obstacles, such as fans and dampers, found in ducts. Also, room vents 

would need to be replaced with ones that would be RF-friendly. Very little research is 

being pursued in this area and has attracted little commercial interest as well. This 

technology should be monitored; if commercial interest develops it could provide a lower 

cost alternative to BDAs. 

ENHANCING TECHNOLOGIES

The following four technologies can also be used to enhance the function of existing 

digital communications system regardless of the system architecture. All are being 

intensively researched and all should be considered for inclusion in firefighter 

communication systems. Smart antenna technology can be applied to both analog and 

digital systems. 

Smart Antennas 

Smart antennas are under intensive research for many communications applications, 

including use in wireless LANs such as MANets and commercial cellular systems. They 

promise to significantly extend the range and data rate that wireless links support. This 

may help address the data rate shortcomings in MANets as radios are added to the 

network. Smart antennas products have been announced for inclusion in wireless access 

points. 

Channel Coding, Interleaving and Encryption 

These techniques are present in almost all digital communications systems. Systems 

using these techniques function well indoor as they are less susceptible to conditions, 

such as multipath and interference, that cause errors. Firefighter radio systems cannot be 

retrofitted with these techniques and new radio systems would need to be developed. 
NIOSH Firefighter Radio Communications Executive Summary 

TriData Corporation xiv September 2003 

Spread Spectrum Modulation 

Spread spectrum modulations provide improved communications because they can 

mitigate reception problems caused by multipath and interference from narrow band 

radios. Again, firefighter radio systems cannot be retrofitted with this and new systems 

would need to be developed. 

Electronic Status Systems 

The newly announced electronic status systems automatically track firefighter status to 

address the difficulty faced by Incident Commanders in tracking personnel on the 

fireground. Radio channels are assigned to incident command sectors and the system 

tracks them and displays status on a laptop. Future enhancements will include the ability 

to poll individual firefighter radios to determine if they are in a coverage area. If they are 

out of coverage for too long a warning will be displayed. If the ability to determine radio 

location were integrated, it could further enhance firefighter safety. 

Conclusion 

Current firefighter communications systems were chosen more for mobility or 

availability of spectrum than for suitability to the job of providing robust, reliable 

communications into, from, and within structures. It is not surprising that they can fail to 

provide adequate communications in buildings, which are the most challenging of radio 

communication environments. 

The technologies discussed in this report offer the possibility to significantly improve 

radio communications in large structures as well as in basement and other below grade 

areas. But it also appears that one technology alone will not be sufficient. Combining 

technologies together to make a hybrid system may be necessary. A MANet system 

provides the firefighter the mobility he needs; when coupled with a PLC or MF 

communications system, a MANet system may provide coverage even into difficult areas 

where radio waves cannot penetrate. Enhancing technologies can be integrated into this 

hybrid system to give even further improvements. 

Many of the technologies considered in this report are undergoing commercial 

development at a fast pace. This promises to keep the underlying cost of the technology 

reasonable, although the special requirements of the fire service may impose additional 

costs. Commercial development should be encouraged, as the benefits of these 

technologies will improve fireground communications. 
NIOSH Firefighter Radio Communications 

TriData Corporation 1 September 2003 

CHAPTER I: INTRODUCTION 

One of the most significant problems facing firefighters within a structure on the 

fireground is the ability to communicate reliably between the firefighters themselves and 

between the firefighters and the command post or communications center. In an ideal 

world, firefighters would be able to communicate with one another and the command 

post at all times, regardless of where they are or what they are doing. However, this is not 

the case. 

Over the past decade, incidents involving firefighter injuries and fatalities have 

demonstrated that, despite technological advances in two-way radio communications, 

important information is not always adequately communicated on the fireground or 

emergency incident scene. Also, the events of September 11, 2001, and other emergency 

situations in recent years have highlighted the need not only to improve firefighter radio 

communications, but also the communication systems available to law enforcement 

personnel, emergency management officials, and other public-safety responders. Equally 

important is the interoperability of all of these systems. 

The continued incidence of firefighter fatalities where communications are cited as a 

contributing factor as well as the industry-wide lack of consensus on the appropriate 

frequencies to use in fireground communications have prompted NIOSH to more 

thoroughly investigate fire department communications and its problems. 

Scope of Work 

This study seeks to identify and address specific deficiencies in firefighter radio 

communications by researching the types of radio communication systems currently in 

use by the fire service and identifying what problems exist with them; identifying current 

technologies of interest to firefighter communications; identifying knowledge gaps 

regarding the effectiveness of such technologies; and finally, make recommending future 

research to improve firefighter radio communication and personnel location. In particular, 

this study focuses on communications problems caused by inadequate radio frequency 

(RF) signal propagation within a structure during firefighting operations and to and from 

the structure to the incident command post (ICP) or dispatch center. 

The scope of work is described in more detail in Chapter II, “Methodology.” 

Types of Radio Systems 

Currently, most fire departments in the United States use conventional analog or digital 

mobile two-way radio technology operating in the 30–50-MHz band (VHF, low band), 

150–160-MHz band (VHF, high band), 450–470-MHz band (UHF), and more recently 

the 800-MHz band. [77,314] Which type of system a fire department uses has both 

historical and technological reasons. Historically, the communication systems were first 

available in the lower bands. In terms of technology, communications systems have been 

chosen according to atmospheric propagation characteristics and to a lesser extent by 
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structure propagation characteristics. For example, the lower bands propagate further 

through the air than do the higher. In a rural area, this is a plus as it allows coverage from 

a base over a much longer range, which keeps costs and complexity down. In an urban 

area the long range can be a minus as the radio environment has many more users within 

range and interference is a big problem. 

Very high frequency (VHF) is the part of the radio spectrum from 30 to 300 MHz. VHF 

radio systems, either low band or high band, are simplex systems—messages are sent 

only one-way at a time. The low band provides relatively long-range coverage from base 

to mobile units but suffers from skip interference caused by distant low band signal 

skipping off the ionosphere and interfering with local radio transmissions. The high band 

also has problems with interference from mobiles up to 50 miles away and can only give 

reliable hand-held-to-hand-held communications for about 3⁄4 of a mile unless the radio is 

elevated more than 5 feet above the ground. High-band VHF systems typically need to 

use repeaters to provide area coverage. Although, VHF has superior structure penetration 

in comparison to UHF [77], VHF’s susceptibility to interference makes it a poor choice 

for urban use. Many rural systems use VHF radios because of their range, and because 

their relatively uncrowded RF environment does not cause unacceptable interference.

Ultra high frequency is the part of the spectrum from 300 to 3000 MHz. These ultra high 

frequency channels do not have the range of the low or high band frequencies of the 

VHF, and typically require the use of repeaters to have the same coverage as low or high 

band VHF frequencies [84]. Conversely, because of the shorter range and the lack of skip 

propagation, they do not suffer from the interference problems of the VHF bands. 

VHF and UHF, except 800 MHz, are conventional radio systems. In a conventional 

system, a group of radios share one fixed channel or frequency. If that channel is in use 

by one user in the workgroup, service is not available to others. 

The FCC has designated parts of the 800-MHz to 900-MHz radio frequency (RF) band as 

public safety radio frequencies for use in public safety trunking radio systems. Trunked 

systems, which are usually computerized, allow more efficient use of frequencies. In a 

trunked system a set of radio channels (a trunk) is assigned under computer control. 

When a firefighter transmits, a computer automatically assigns the firefighter to an open 

frequency. When the firefighter ends the transmission, the frequency is automatically 

made available to the next firefighter transmitting [315]. The operator does not have to 

manually select a frequency. Because these systems have multiple frequencies and they 

are only assigned while a radio is actively transmitting, they provide higher capacity than 

conventional VHF and UHF radios. This helps prevent radio system congestion. The high 

capacity of these systems and low interference from other users of the public safety 

trunking band make these systems appropriate for use in congested areas. 

No band of frequencies is perfect; many frequencies work well. The selection of 

frequency is dependent on a variety of factors, including “frequency availability, area to 

be covered, type of terrain, number of radio units required, frequencies used by bordering 

fire [or public safety] districts, mutual-aid agreements, type of operation, and use of 

emergency medical radios.”[315] 
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Communications from Inside a Structure to the Outside or Vice Versa 

Fireground communication has significantly changed over the past decade with the 

proliferation of the portable radio. In the fire departments reviewed, each firefighter team 

of two will typically carry a small portable radio. In some fire departments each 

firefighter has their own radio. The increase in number of portable radios coupled with 

the multitude of communication systems has prompted many fire departments to 

reexamine their radio procedures, and develop new fireground communication protocols 

to aid in controlling radio traffic. 

The focal point of all fireground communications is the command post. Typically, the 

command post will be positioned as close to the incident as safely possible to facilitate 

the communication process. The type of fire and the type of structure involved dictates 

the location of the command post. Structures such as high-rise buildings, tunnels, and 

sub-basements may disturb the effectiveness of portable radios and communications. In 

these situations, some fire departments may position the command post inside the 

structure to compensate for the portable radios’ weak RF output. For example, on fires 

located on the upper levels of a high-rise structure the command post may be established 

several floors below the fire (as opposed to the street level) to help improve 

communication. 

In the fire departments reviewed, each department had more than one tactical radio 

channel for fire operations. Typically, once the command post has been established, fire 

ground units are switched off of the main dispatch channel to a tactical fire ground 

channel. These channels usually have a restricted range that permits fire ground units to 

communicate independently of the main dispatch channel, and also prevent the bleedover 

of other radio traffic from other fire units operating in the vicinity. 

Firefighters operate as a team consisting of two or more personnel. Each interior team 

can have one or more portable radios. To help control traffic, all radio communications 

with command post is normally made by the unit officer or the senior team leader. 

However, if fire conditions restrict visibility, team members may have to communicate 

with each other by radio, which can substantially increase radio traffic. Some 

departments restrict the use of individual portable radios to only emergency situations 

where firefighter may become separated or trapped. 

The operation modes commonly used in fire department communication systems include 

simplex, duplex, and trunked. 

The simplex mode requires both a transmitter and receiver at each end of the 

communications path. In simplex mode, only one end (i.e., the transmitter or the receiver) 

may operate at a time. It requires only one frequency. Only one firefighter may transmit a 

message on a portable radio while using a simplex channel, all others must receive. 

During interior fire department operations, firefighters may switch to a simplex channel 

because their low-powered radios cannot transmit outside the building. Simplex channels 
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do not require the use of repeaters or towers. Rather, the portable radios themselves act as 

the transmitter and receiver sites. 

Duplex mode uses two frequencies that allow both ends to communicate simultaneously. 

Thus, one user may interrupt another to facilitate discussion. Repeaters may be used in a 

duplex system. Repeaters, typically located in a high place such as a mountaintop or tall 

building, receive a transmission from a radio (in the system) on one frequency and 

retransmits (or “repeats”) on another. Repeaters can also be located in fire apparatus and 

command vehicles for use on particular incidents where communications are problematic. 

All radios with proximate distance will receive the transmission from the receiver. 

Repeaters are used to augment the range of the radio system. 

Repeaters also allow a low-power portable radio to hear other radio messages (to, from, 

and within a structure) when obstructions may normally hinder communications. 

Sometimes, even in the presence of a repeater, obstructions are too great and will prevent 

a radio signal from being transmitted. 

A trunked system, which may include a single user or different workgroups, uses a group 

of radio frequencies (a trunk). The system is dynamically controlled by a computer, 

which directs a transmission to an available channel or frequency. 

Firefighter Radio Communications Problems 

Communication problems encountered by firefighters (and others) can be broadly divided 

into two categories. First are mechanical or technical issues related to unsuitable 

equipment, radio malfunction, system design, inadequate system capacity (too much 

radio traffic), and failure due to extreme environmental conditions (e.g., fire, heat). Poor 

and mottled radio communications in large structures have also been a persistent 

problem. Another technical issue is interoperability, or the ability for various departments 

(e.g., fire, police, public works) to communicate with each other or another neighboring 

jurisdiction. The second category of problems relates to human factors. 

In many instances, a variety of mechanical and technical issues such as RF attenuation, 

fading, and building construction can prevent the system from maintaining sufficient link 

quality for reliable communications. In large multistory structures, for example, the 

frequency may bounce of the walls and windows with reflective coverings, or simply be 

absorbed from the construction of the building. Some of these cases involve situations 

where a firefighter is in danger and most in need of communications. As a result, this lack 

of reliable communication could severely compromise the effectiveness, the safety, and 

even the life of the first responder. 

Human factor include radio discipline, training, tactical decisionmaking as well as others. 

These factors combine with technical and equipment issues to adversely affect firefighter 

radio communications. As such, these factors are considered as a component of the 

overall analysis. 
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One of the most interesting comments about radio communications noted during this 

research is: "Our [the fire service] radio systems aren't failing, but rather we can't get the 

signal throughout buildings with 100 percent accuracy . . . this is affected by building 

construction, windows, elevator shafts, the output strength of the system, and the 

[strategic design and implementation of infrastructure such as the] presence of 

repeaters."1

Organization for the Report 

The remainder of this report is divided into five major sections, each addressing one 

aspect of the study. The first section, Chapter II, reviews the study research methodology. 

The second section, Chapter III, discusses the overall firefighter communication 

problems, both technical issues and human factors. It also presents an overview of these 

communication issues as well as a review of communications issues that affect fire 

departments everyday. The third section, Chapter IV, examines the communication 

problems inherent in structures, and the risk to firefighters. The fourth section, Chapter 

V, discusses the results of the research and includes descriptions of available 

technologies of interest, their current applications, potential applications, limitations, and 

areas needing further investigation. 

The report has two appendices. Appendix A is a tabulation of prioritized project issues, 

and Appendix B details the communications problems of 24 jurisdictions, both large and 

small. A Glossary of Terms and Abbreviation follows the appendices. The report 

concludes with a Master Reference List containing more than 350 citations used in the 

preparation of this report. 

 

1

 Telephone conversation with Deputy Chief Jeff Coffman, Fairfax (VA) County Fire and Rescue 

Department. 
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CHAPTER II: METHODOLOGY 

The project was divided into two primary tasks: to identify fire service communication 

problems and solutions and to research and analyze the potential solutions to the 

technical RF issues involved in resolving and improving these communications problems. 

From the outset, the project was further refined to focus on communications problems 

within as well as to and from structures, to include high-rise buildings, tunnels, 

basements, underground parking garages, and subway systems. 

Determination of Critical Areas of Interest 

To begin the project, the team members compiled a comprehensive set of 

communications issues that affect radio communications in the fire service from several 

sources – an initial literature survey, knowledge of the project team members, and 

discussions with fire service leaders, NIOSH project team, engineers, and others. Team 

members refined this comprehensive set of issues with NIOSH project personnel to 

identify critical issues that could be addressed by improvements in radio 

communications. A prioritized list of communication and personnel location problem 

areas was developed. In general, the primary focus was clarified to be the identification, 

status, and research recommendations for technologies that could improve 

communications or provide firefighter location within structures. The list of the high 

priority topics is shown in Table 3 below. The full list of ranked topics is attached as 

Appendix A with ‘10’ being a highly ranked problem and ‘1’ the lowest. 

TABLE 3: PRIORITY TECHNICAL AREAS AND RELATED TOPICS ADDRESSED IN STUDY

Ranking Area Example Issues 

10 

Accountability (Integrating 

Personal Accountability 

Systems (PAS) with 

Communications) 

• Integrating PAS with communications 

• Electronic accountability 

• Automatic vehicle location 

• Electronic command boards 

10 Communication Planning and 

Coordination 

• Through building (into/out of) 

• Underground 

• In building 

10 Monitoring Firefighter Welfare 

and Location On-Scene 

• Role/responsibility of dispatchers. 

• Use of field communications units and 

communications coordinators 

• Remote monitoring 

• Vital signs 

• Location 

10 Reliability 

• Line-of-sight limitations 

• Underground (subways, parking garages) 

• Confined space rescue 

• Communication into and out of buildings 

(especially high rises) 

• Intermittence 

• Communication coverage/dead spots 
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Ranking Area Example Issues 

10 Interference 

• Building construction and materials (such 

as concrete, metal, and Lexan) 

• Radio propagation through fire, heat, and 

smoke 

• Cell phone towers (e.g., Nextel) 

• Terrain 

10 Unsuitable Equipment • Frequency band unsuitable for 

structure/ground penetration 

Information on and about grants to pursue these technology areas was originally ranked 

as one of the priority issues. Because grants are not within the scope of the technical 

nature of this project, this topic was not pursued. Grants, however, are available through 

the United States Fire Administration (USFA), National Institute of Standards and 

Technology (NIST), and other sources as well. The USFA, through its Assistance to 

Firefighters Grant Program, has awarded funds to many fire departments to purchase 

communications systems and other equipment. Money is also available from NIST for 

research and development. 

Literature Review 

Based on this prioritized set of topics, the study team conducted a comprehensive 

literature review to research the radio communication technology in use by firefighters, 

what problems exist with communications, and on relevant research/evaluations of 

existing or proposed technology. The team searched a variety of bibliographic databases 

including the following: 

Engineering Index – The Engineering Index contains abstracted information from 

the worldwide significant engineering and technological literature. It covers 

approximately 4,100 journals and selected government reports and books from 1970 

to the present. Over 480,000 records of significant published proceedings of 

engineering and technical information are also included. 

INSPEC – INSPEC is a database containing bibliographic citations to items in 

Physics Abstracts, Electrical and Electronic Abstracts, and Computing and Control 

Abstracts. Over 4,100 journals and serials are scanned from 1969 to the present. 

Included are papers, journal articles, conference proceedings, books, reports, and 

dissertations. 

PubMed – PubMed is the National Library of Medicine's (NLM) search service that 

provides access to over 11 million citations in MEDLINE, PreMEDLINE, and other 

related sources journals. MEDLINE is NLM’s premier bibliographic database and 

contains over 12 million citations from the mid 1960s to the present. PreMEDLINE 

is the in-process database for MEDLINE, containing details of very recently 

published articles. The journals primarily fall within the general science and 

chemistry field. MEDLINE contains bibliographic citations and author abstracts 
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from more than 4,600 biomedical journals published in the United States and 70 

other countries. 

Nerac –Nerac began operating in 1966 as the New England Research Application 

Center, an experimental collaboration between the University of Connecticut and 

the National Aeronautics and Space Administration (NASA). Nerac provides peerreviewed literature from a collection of over 250 million abstracts, citations and 

full-text articles. Nerac locates published articles from international resources to 

bring information that is typically unavailable through Web-based search engines. 

Its databases include information on journal articles, patents, conference papers, 

theses, business and financial reports, manuscripts, and government regulations. 

Nerac searches can be applied to 128 separate databases of which 57 are in the 

engineering fields. The databases that were accessed most heavily for this project 

were: 

• Aerospace Database 

• DTIC – Defense Technical Information 

• Inspec – Electronics and Physics 

• Dissertation Abstracts 

• Inside Conferences 

• Conference Papers Index 

• U.S. Patent Applications 

CiteSeer (Research Index) – CiteSeer is a scientific literature digital library that 

indexes Postscript and PDF research articles on the Web. Developed by NEC 

(formerly Nippon Electric Company), it allows the user to quickly track how 

research has been used and what recent developments have occurred in the research 

area. The automated indexing system not only indexes research articles by crawling 

journal websites on a regular basis, but will also index each article's citations, which 

can be viewed in the context of the article. This context enables the reader to judge 

the links between studies and the citations noted in the research. 

National Technical Information Service(NTIS) – NTIS is a database of the U.S. 

government agencies containing only unclassified literature, some state and local 

governments, and some non-U.S. governments. Coverage is from 1964 to the 

present; included are reports, bibliographies, conferences, symposia, government 

documents, journal articles, patents, standards, and translations. 

Firedoc – Database of the National Institute of Standards and Technology’s 

Building and Fire Research Laboratory (BFRL). It contains publications from the 

BFRL staff, its contractors and grantees from the early 20th century. Over 60,000 

bibliographic records and indexing are in English from the BFRL staff and for fire 

research and fire engineering organizations and fire departments worldwide 

regardless of language. Reports, journal articles, conference proceedings, contractor 

and grantee reports, and audio-visual materials are included. 
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USFA/FEMA Online Catalog – This online catalogue is a database of the U.S. Fire 

Administration/ Federal Emergency Management Agency. It contains bibliographic 

citations (and abstracts Executive Management Institute’s papers) to over 100,000 

books, reports, periodicals, and audio-visual materials on their collection. 

InfoTrac OneFile – InfoTrac OneFile provides access to periodical and news 

information on a diverse set of topics, including humanities, education, business, 

science, current events, art, politics, economics, social science, law, health care, 

computers, technology, environmental issues, and general interest topics. InfoTrac 

OneFile has access to nearly 32 million articles in a wide variety of periodicals. 

In addition, the team searched for information from other federal agencies, such as the 

National Aeronautical and Space Administration and the Federal Communications 

Commission. Private industry sources were also explored, from the National Fire 

Protection Association to the Association of Public-Safety Communications 

Professionals, among others. The Internet was used to access current trends and products. 

The results of the literature review included a variety of published materials, including 

technical reports, trade journals, academic research papers, CD-ROM collections, 

government reports, open-source material available on the Internet, media reports, 

international studies/reports, and manufacturer/vendor literature. 

Fire Department Communication Issues Review 

Once the technical literature review was well underway, the study team gathered and 

reviewed fire service communications literature and studies. The information was 

gathered from a variety of sources: much of the information comes from fire department 

management studies previously undertaken by TriData Corporation. Some information 

comes from individual fire department annual reports, websites, or other fire department 

literature. Wherever possible, the information from these studies was verified with the 

fire department to ensure that the most current data was reflected in this report. The 

reviews focused on actual communications problems experienced by various jurisdictions 

and the solutions implemented to mitigate them. 

The technical literature review yielded a number of promising technology areas. During 

the course of this research, the study team contacted experts in these areas to determine 

whether the new products and research had potential to improve firefighter 

communications. These contacts were conducted primarily by telephone and email. 

Knowledge Gaps Analysis 

Based on the information collected through the literature search and discussions, a review 

was conducted of the available knowledge and research related to radio communication 

systems. We identified the gaps between what current technology yields for firefighter 

radio communication and what would be necessary to address the firefighter location 

issues and more effective communications within structures. We also determined what 

technologies and solutions are available bridge these gaps; and addressed future 
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technologies or products that could improve overall firefighter communication and 

safety. 

The analysis approached the knowledge gap problem from three angles. First, we 

examined the gap between the current technical knowledge of the problems and current 

proposed solutions. Second, we assessed the gap between available published material 

and the material actually needed to fully address the issue. Finally, we considered the gap 

between the available technology and the implementation of that technology in the fire 

service. 

Recommendations 

The final step in the study process was to develop a series of recommendations for areas 

of future research to improve firefighter communications. Where possible, specific 

vendors, agencies, and other resources are identified as avenues to complete this research. 
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CHAPTER III: FIREFIGHTER COMMUNICATION ISSUES 

Communication problems commonly encountered by firefighters (and others) can be 

broadly divided into two categories. First are mechanical or technical issues related to 

unsuitable equipment, system design, inadequate system capacity (too much radio 

traffic), and building construction, among others. 

The second category includes human factors such as radio discipline, training, and 

tactical decisionmaking. These factors, while not technical issues themselves, adversely 

affect firefighter radio communications, especially when combined with technical and 

equipment issues. 

This chapter presents an overview of these communication issues as well as a review of 

communications issues that affect fire departments every day. 

Technical Issues 

Fire departments consistently have problems maintaining effective communications while 

operating in large structures, such as high-rise office buildings and apartments, and 

warehouses. Similar issues exist in structures with a large number of windows (or areas 

of glass) with reflective coatings. Communications from areas below grade (e.g., 

basements, parking garages, subway systems, tunnels) tend to be uneven. For the typical 

home, communications are generally not a problem. The technical issues associated with 

the physical structures themselves (building materials, height, etc.) are discussed further 

in Chapter IV. 

Below is a discussion of the technical issues that are commonly associated with fire 

department radio communication difficulties. 

EQUIPMENT

In general, the most common communication problem encountered by firefighters is the 

inability to effectively communicate while wearing self-contained breathing apparatus 

(SCBA). In addition, it is difficult to operate most portable radios while wearing full 

personal protective gear (PPE). Thick fire suppression gloves make it difficult to turn 

knobs or push buttons, and low-light and smoke conditions coupled with wearing an 

SCBA facepiece make it hard to see the LCD display on a radio (if so equipped). 

Another common problem is the equipment’s tolerance to hazardous environmental 

conditions, such as high heat, prolonged exposure to water, and rough handling. While 

radios are water resistant, not all models are waterproof. This is more of a problem with 

older radios, however, as newer models are more water resistant if not completely 

waterproof. 
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Many radio systems are highly dependent on computer technology. In the event such 

technology fails (e.g., the trunking software becomes inoperable), the entire radio system 

can be disabled.2

 To prevent complete failure of the radio communication system, most 

jurisdictions employ backup analog frequencies to maintain critical communications 

(e.g., dispatch and contact with units). Reliability and sustainability are key components 

of any sophisticated system. 

The usefulness of a portable radio is dependent on the life of its battery. Some older 

radios require batteries to be “conditioned” or otherwise use special chargers for optimal 

battery life. This requires users to be especially diligent about maintaining radios and 

their batteries, which can be challenging for departments already busy with emergency 

response and apparatus maintenance. 

SYSTEM DESIGN

Perhaps one of the most critical technical issues related to radio communications is the 

design of the system itself. Whether a department uses low band, high band, analog, or 

digital technology, an adequately funded, carefully thought out, strategically designed 

system (i.e., the number and placement of tower sites and repeaters) will perform better 

than one that was not carefully planned. 

The lack of frequencies available to public safety agencies has made it difficult for some 

jurisdictions to modernize their radio communications systems. Public safety departments 

are limited to VHF low band, VHF high band, UHF 450 MHz, and UHF 800 and 900 

MHz. Instead of transitioning to a completely new system, many jurisdictions are 

exploring the possibility of applying new technology to enhance their existing system’s 

capability with only a modest expenditure of fire department budget. 

There are common design problems for most systems. An inadequate number of tower 

sites and repeaters typically result in “dead spots” – areas where radio communications 

are difficult or impossible. Buildings and terrain, among other factors, can cause dead 

spots. Similarly, a system might be designed with too little signal output to reach all areas 

of the jurisdiction (in some areas, for example, the radio system output is limited due to 

proximity to an airport or the Canadian or Mexican borders). 

As discussed later in this chapter, fire departments cannot always separate dispatch and 

tactical operations channels. This is a critical function, as the combination of dispatch and 

incident operations can overwhelm a single radio channel, causing critical messages to go 

unheard. Some experts also argue that large-scale incidents (e.g., high-rise fires) should 

 

2

 In a trunked radio network or system, a large number of workgroups (or users) share fewer channels 

because the trunking equipment dynamically allocates an available channel when users key their radio. A 

computer manages the system. When a user (e.g., firefighter) has a message to transmit, the computer 

assigns an available trunk. “The advantage of this type of system is that it uses a group of available 

frequencies more efficiently by utilizing the capabilities of the computer to manage the radio traffic on each 

frequency. Thus, more radio traffic can be handled on the available frequencies, without causing congestion 

and interference.” [314] 
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use multiple tactical channels to separate key functions, such as fire attack, search, 

emergency medical services, command, etc. 

SYSTEM CAPACITY

In general, fire departments throughout the country are responding to a higher number of 

calls for service than ever before and call volume will continue to rise. The majority of 

these calls are for EMS, which is a national trend. While EMS calls do not typically 

require a tactical channel, the associated radio traffic (e.g., dispatch, response, ER 

consults) may add to the system traffic. A dramatic increase in call volume and increased 

frequency of use may cause the system to reach capacity. As a result, existing 

communications may lack the capacity to handle the associated rise in radio traffic. 

A large-scale event such as natural or other disaster (i.e., terrorist event) is also likely to 

dramatically increase system traffic. In such cases, multiple city agencies or departments 

are likely to be at the scene of the incident, each using its respective communication 

system, possibly causing the radio system to reach capacity. 

Trunked systems provide more capacity than conventional VHF and UHF radio systems 

because a computer assigns a frequency only while a firefighter is actively transmitting, 

and then automatically takes it back when the transmission ends so the signal is 

immediately available for another transmission. 

INTERIOR (STRUCTURE) COMMUNICATIONS

It is critical for firefighters to communicate with one another within a structure and with 

units operating outside the structure, regardless of the building construction. The inability 

to communicate from buildings, below grade, basements, garages, tunnels, etc., is a 

persistent problem in the fire service. 

The construction of a structure can contribute to communications problems. Residential 

buildings are typically constructed of wood and other materials easily penetrable by radio 

waves. Commercial structures, however, are typically built with large amounts of steel 

and concrete that, to varying degrees, act as barriers to radio frequency waves. In 

addition, some types of glass and other window materials used in commercial 

construction inhibit radio frequencies. This topic is discussed in depth in Chapter IV. 

High-rise structures, warehouses, and underground structures such as tunnels and 

basements pose their own challenges to radio communications. In addition to the 

construction materials used to build them, the height of such structures can interfere with 

line-of-sight (LOS) access to repeaters and radio towers. 

Following the September 11, 2001, terrorist attacks, the Fire Department of New York 

(FDNY) contracted with McKinsey and Company to review its response and 

preparedness for future events. Based on interviews with firefighters, McKinsey reported 

that communication failures occur on a regular basis when transmitting from the inside to 

outside or vice versa from a high-rise building, tunnel, or subway system. Of the over 
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2,000 high-rise buildings in New York City, the FDNY feels that only a fraction allow 

reliable communications. [51] 

After-incident reviews of the World Trade Center collapse indicate that inadequate 

communications prevented personnel from receiving critical information about the 

impending collapse of the Towers. The reason cited was that FDNY portable radios do 

not work well in high-rise buildings and the signals from the radios were rebroadcast by a 

repeater system. Therefore, when critical information was relayed, it was sporadic or not 

fully received. 

McKinsey and Company notes that the communication failures can be corrected by 

deploying repeating infrastructure that “receives, amplifies, and retransmits radio 

communication signals to improve coverage.” The report observed that portable 

repeaters “may help mitigate in-building communication difficulties, but do not provide 

full coverage for high-rises,” and suggests that stationary repeating infrastructure is 

preferred, especially if it is “designed, installed and maintained properly.” [51] 

With an estimated cost of $0.30–$0.60 per square foot of high-rise space, McKinsey and 

Company estimates that FDNY would have to spend upwards of $250 million to install 

permanent repeater systems to ensure radio communications in the city’s high-rise 

structures. In the case of tunnels, McKinsey recommends that FDNY participate in the 

Police Radio System, which is funded by the Metropolitan Transportation Authority. The 

Police Radio System uses UHF radios to maintain two-way voice communication. 

Particularly with the vulnerability of a limited security subway system to a terrorist 

attack, FDNY and other fire departments with subway systems in their districts should 

ensure that communication systems are fully operational in these structures. 

POOR RECEPTION

Inadequate radio reception is the result of many factors. Most notable among these 

factors are low power, interference, and the terrain-and-built environment. 

There is a direct relationship between RF power output and transmitting range. The 

higher the RF output, the greater the transmitting ranges, and vice versa. Portable radios 

have a low RF output and, therefore, have a short operating range. On average, the RF 

output of portable radio range from 1 to 7 watts. [314] In comparison, mobile radios 

typically have an RF power output 20–100 watts. [314] Because mobile radios are not 

portable, they cannot provide on-scene communications or be carried into a large 

structure. As a result, firefighters must carry low-powered portable radios, which may not 

work very well in large structures. 

Atmospheric interference is uncontrollable. This natural occurrence results from solar 

disturbances on the surface of the Sun. These solar disturbances, also known as “solar 

flares,” emit large volumes of electromagnetic radiation and highly energized particles, 

which can affect satellite and radio communications on Earth. The highly energized 

charged particles pass through the ionosphere traveling at the speed of light and can 

affect radio signals over the entire frequency spectrum. 
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Electronic interference is also common. Many public safety radio systems often suffer 

destructive interference from a variety of sources, including commercial 800-MHz 

trunking antenna sites (Nextel, for example), interference with other public safety radio 

systems (e.g., neighboring jurisdictions), or other electronic devices. 

The environment – both topographic factors and the built-in environment (e.g., high-rise 

buildings) – is yet another cause of poor reception and solutions exist to help correct 

these reception problems. In some areas, additional antenna sites have reduced (or 

eliminated) interference caused by environmental factors. 

INTEROPERABILITY

Radio communications interoperability allows various departments (e.g., fire, police, 

public works) to communicate with each other or another neighboring jurisdiction. The 

objective is for these departments to exchange information when necessary (e.g., mutualaid call, mass casualty incident, special event). 

Throughout the country, adjacent jurisdictions or even agencies in the same jurisdiction 

use different radio communication systems. For example, while one county may use 

high-band frequencies (154.115–159.21 MHz), its neighboring jurisdictions might use an 

800-MHz trunked system. Or, a city’s police department could use an 800-MHz trunked 

system while the fire department uses a high-band system. 

Interoperability is not only critical in the case of a major emergency incident or disaster, 

but also important for the everyday types of calls where two or more departments are 

involved. 

While a significant problem in fire service communications, interoperability is outside the 

scope of this report and is not addressed in detail. 

DIGITAL VS. ANALOG 

Modern communication systems are evolving from analog to digital technologies. Digital 

systems offer better performance over a broader range of conditions, much greater 

flexibility, and more efficiency than analog at a lower cost. As with most alternatives, 

tradeoffs must be considered. Rarely does one find that all the pluses are on one side and 

that is the case with analog and digital communications. 

Performance 

The human ear corrects errors in analog communications systems. It can decode a wide 

range of hissing, crackling, volume changes, and other variations. As the signal to noise 

ratio (SNR) degrades, there comes a point where the transmission cannot be understood. 

But with digital communications, other error-correcting methods must be used. Digital 

communications allows for error-correcting codes that provide clear transmission over a 

much wider range of SNR than analog. However, at some point as the SNR drops, it falls 

so low that the digital system can no longer correct errors. When this happens, the signal 
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quality varies from perfect to gone. So, while digital schemes are capable of error-free 

transmission while analog ones are not, it is not uncommon to find radio users who prefer 

to let their ear decide when the transmission is indecipherable rather than have the signal 

just go away. 

Flexibility 

Digital communication systems can transmit analog signals obtained by analog-to-digital 

conversion, plus information such as computer data. Any signal that can be sent by 

analog means can be sent digitally. But an analog system cannot send everything that a 

digital system can. Video can be sent by analog means (standard television), but better 

performance is obtained using digital (HDTV). In addition to the ability to transmit a 

wider variety of signals than analog systems, digital communications can be organized 

into area-wide communications systems such as computer networks. These digital 

networks can be local, wide area, or even global and provide efficient and flexible data 

transmission not remotely feasible using analog means. 

Security 

Digital communications can be encrypted to provide robust security while analog cannot 

be protected nearly as well. 

Efficiency 

With digital communications, signal structure can achieve a much more efficient 

communication system via digital compression techniques. Digital communications are 

efficient enough to send more information per user to allow more users to occupy a given 

number of radio spectrum or channels. In analog communication, the only parameters of 

interest are message bandwidth and amplitude. 

Consequently, with the increased speed of digital computers, the development of 

increasingly efficient digital communications algorithms, and the ability to interconnect 

computers to form a communications network, digital communication is now the choice 

for many situations. 

Human Factors 

Even with the most technologically advanced radio communication system, the success 

and failure of radio communications depend on the person who transmits the radio 

message as well as the one to whom the message is transmitted. For example, location of 

the microphone in relation to the mouth and SCBA when transmitting can be important 

with some radio systems. The clarity with which the transmitting person speaks, coupled 

with the volume of the transmission, will drive the audibility of the message at the 

receiving end. It is also incumbent on firefighters to know when to transmit over the radio 

and when not to transmit a message. 
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MESSAGE TRANSMISSION

Well thought-out, clear, and concise messages are important characteristics for 

firefighters to employ during their radio transmissions. On the fire scene, when 

firefighters are excited or are panicked, radio transmissions can be loud and uncontrolled. 

Messages of this nature are difficult to understand. Discipline requires firefighters to 

exercise discretion in messages transmitted over the radio. Noncritical messages increase 

the radio traffic and may prevent emergency messages, such as a Mayday event or 

impending building collapse, from being transmitted. 

Over the years, radio codes and other phonetic techniques have been developed to make 

communications understandable, both for the sake of clarity and to compensate for poor 

radio links. These include the widely known phonetic alphabet (Alpha, Bravo, ..., 

Yankee, Zulu). Such alphabets, used for spelling things out over voice links, are 

variously known as phonetic radio spelling telephone alphabets and analogy alphabets. In 

addition, codes are commonly used by police and other agencies to provide succinct 

communication. These may be “10:4” or other numeric based messages that in some 

cases describe a response or situation. In spite of these techniques, clear and 

understandable radio communication is still a common problem. Firefighters must learn 

any terminology used in their jurisdiction. 

To counter problems with distortion and inaudible radio communications while wearing 

SCBA, some equipment manufacturers have designed integrated microphone and speaker 

systems into SCBA. Depending on the manufacturer, some of these systems use a bone 

microphone worn by the firefighter or a microphone integrated into the SCBA facepiece. 

Speakers are often a modified headset that fits in the firefighter’s ear, under their SCBA 

face piece and other protective gear. Most include a large, easy to operate push-to-talk 

button for use while wearing firefighting gloves. These systems increase the clarity of 

radio transmissions, reduce the amount of feedback from radios being too close to one 

another, and increase the likelihood that the transmission will be heard and understood. 

DIFFICULTY OPERATING RADIOS

As mentioned previously, the use of full PPE and SCBA makes it difficult to use a 

portable radio effectively. While the push-to-talk button is generally easy to use with 

gloves, the knobs and other buttons can be much more difficult. To overcome this, some 

departments are programming their radios so that the first and last position on the channel 

selector will automatically direct the firefighter to a channel monitored by the dispatch 

center. In the event of an emergency, the firefighter can turn the dial all the way in either 

direction and reach someone to alert them of the emergency. 

INADEQUATE TRAINING

Though firefighters receive hundreds of hours of training on emergency response, radio 

communications do not typically receive the same amount of attention. As such, 

firefighters may not be aware of proper radio usage. Examples include how to use the 
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radio in general, how to use the radio while wearing SCBA, and how radio 

communications are affected by a Mayday event. 

FIRE SERVICE CULTURE

Firefighters are, by their nature, problem solvers and independent. It is difficult to 

convince firefighters that they need to call for help quickly in the event that they become 

lost, trapped, or incapacitated. Waiting to call for help delays rescue efforts. And when a 

firefighter’s Mayday calls are not initially heard, rescue efforts can be delayed even 

longer. 

Applicable Standards and Regulations 

Standards have been developed to address communications systems, but, by and large, 

such standards are mute on identifying the best system for fire service communications. 

Thus each jurisdiction has the challenge of designing and building a radio communication 

system that meets its current and anticipated future needs. 

NFPA 

The National Fire Protection Association (NFPA) is a national nonprofit organization that 

develops consensus based codes and standards for the fire service. The NFPA has 

developed NFPA Standard 1221, Standard for the Installation, Maintenance, and Use of 

Emergency Services Communications Systems, 2002 Edition. This standard does not 

make specific recommendations on the types of radio system or frequency ranges that 

should be used by fire departments for emergency incident communications. Rather, it 

addresses construction, layout, staffing, and emergency backup components of the 

communication center. 

The nineteenth edition of the NFPA’s Fire Protection Handbook references radio 

frequency selection, but only shows that fire departments use VHF low band, VHF high 

band, UHF 450 MHz, and UHF 800 MHz and 900 MHz. It does state that, “each band of 

frequencies has its advantages and disadvantages, and the selection of a particular band 

will depend on factors such as frequency availability, area to be covered, type of terrain, 

number of radio units required, frequencies used by bordering fire districts, mutual aid 

agreements, type of operation, and use of emergency medical radios.”[314] The 

handbook also describes Simplex, Two-Frequency Half Duplex, Two-Frequency Full 

Duplex, Two-Frequency Repeater Systems, Trunked Systems, Tone-Coded Squelch, and 

Radio Paging Systems, but does not take a stance or recommend one type of system or 

frequency over another. 

FCC 

The Federal Communications Commission (FCC) is an independent United States 

government agency, directly responsible to Congress. The FCC was established by the 

Communications Act of 1934 and is charged with regulating interstate and international 
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communications by radio, television, wire, satellite and cable. The FCC's jurisdiction 

covers the 50 states, the District of Columbia, and U.S. possessions. 

Recent FCC activity of interest to the firefighting community includes: 

• Permitted use of UWB devices in restricted bands and restricted transmit power. 

• Removal of 50 MHz of government frequency allocation from 4840–4990 GHz 

with reallocation to public safety use. This band permits broadband services in 

support of public safety. 

• Allocation of 764–776 MHz and 794–806 MHz for public safety use. 

• Development and promotion of broadband services to compete with local 

broadband service from cable and telephone companies. As part of this effort, the 

FCC strongly supports development of Access PLC, which uses the medium 

voltage power grid to deliver broadband service to homes and offices. 

PSWAC 

Congress empowered the Public Safety Wireless Advisory Committee (PSWAC) in June 

1995 to address issues relating to spectrum needs and uses for the public safety 

community. The PSWAC identified an immediate need for 2.5 MHz more of spectrum, 

and a longer term need for an additional 25 MHz of spectrum for public safety use. 

PSWAC found that 70 MHz more of spectrum must be allocated if the public safety 

agencies and emergency responders were to use modern technologies, many of which 

require additional spectrum. 

Experiences From the Field 

This section summarizes the communications problems — mechanical and technical 

issues, as well as human factors — that are commonly encountered by jurisdictions 

throughout the country and the solutions implemented to mitigate them. Below are 

highlights of the actual communications problems experienced by these jurisdictions; a 

more comprehensive writeup is found in Appendix B. 

The departments reviewed were mostly all-career fire departments, large and small, in 

mostly urban or suburban areas as the information on these departments was more readily 

available. A small group of volunteer departments and jurisdictions in rural areas was 

also reviewed. In some instances, urban fire departments also provide fire or EMS 

services to rural areas. 

In all, information from 24 fire departments is included in this report. Of these, 18 are allcareer fire departments, 5 are combination, and 1 is an all-volunteer fire department. 

Table 4 summarizes the departments reviewed. 

The jurisdictions ranged in population from a high of 3.7 million in Los Angeles to a low 

of 3,700 in Gettysburg, OH. The service land areas also varied widely (as does the 

physical characteristics — terrain and topography — of each area). Land area protected, 
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as measured in square miles, ranged from 15 square miles in Springfield, NJ to 8,000 

square miles in Clark County, NV. 

Communication and radio system priorities differed somewhat in urban and rural 

departments. In urban settings, fire departments contended with a larger variety of 

structures such as high-rise buildings, multilevel residential structures, basements, 

tunnels, and underground transportation systems (e.g., subways). The rural areas, 

typically residential in nature, had fewer large buildings and generally no underground 

transportation systems. 

TABLE 4: SUMMARY OF FIRE DEPARTMENTS REVIEWED

Jurisdiction 

Resident 

Population3

Land 

Coverage area 

(square miles) Land Area 

Fire 

Department 

Type 

Austin, TX 656,562 252 Urban Career 

Bellingham, WA 67,171 32 Urban/Suburban Career 

Boston, MA 589,141 48 Urban Career 

Boulder, CO Rural Fire 

Department 18,000 25 Suburban/Rural Combination 

Brighton, CO 20,905 17 Suburban/Rural Combination 

Charlotte, NC 540,828 242 Urban Career 

Chicago, IL 2,896,016 227 Urban Career 

Clark County, NV 1,375,675 8,000 Urban/Rural Combination 

Dallas, TX 1,188,580 385 Urban Career 

Detroit, MI 951,270 139 Urban Career 

Everett, WA 91,488 48 Urban/Suburban Career 

Fairfax County, VA 969,749 395 Urban/Suburban Combination 

Gettysburg, OH 3,700 60 Rural Volunteer 

Los Angeles, CA 3,694,820 469 Urban Career 

Milwaukee, WI 596,974 96 Urban Career 

Phoenix, AZ 1,321,045 475 Urban Career 

Pittsburgh, PA 334,563 56 Urban Career 

Portland, OR 529,121 134 Urban Career 

San Antonio, TX 1,144,646 412 Urban Career 

San Diego, CA 1,223,400 324 Urban Career 

San Francisco, CA 776,773 49 Urban Career 

Schaumburg, IL 75,386 19 Suburban Career 

Springfield, NJ 14,429 15 Suburban Combination 

Wichita, KS 344,284 136 Urban Career 

In addition, urban systems experienced higher service volumes and increased radio 

traffic. Urban areas had a higher propensity for radio congestion. Fire departments in 

urban areas were mostly career, sometimes supplemented with volunteers, whereas rural 

systems have more volunteer providers. 

 

3

 Data from U.S. Census 2000 is used for consistency and comparison. Data may not agree with that 

reported by the jurisdiction. 
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Topography and terrain in both urban and rural areas varied widely. Typically, rural 

systems covered larger land areas that are more spread out and not as densely populated. 

Natural elements such as mountains, hills, and other potential interfering terrain were 

present in both urban and rural systems, depending on the area. 

More often than not, the urban departments have the resources to provide a 

communications system with the necessary hardware that meets the needs of the area. 

The urban areas had a greater population and tax base. In many departments, the fire 

department operating budget comes directly from property taxes. Properties in urban 

areas generally have a higher assessed valuation than an equal property in a rural area, 

and therefore will raise more tax dollars. 

Table 5 summarizes radio communications issues commonly experienced by the fire 

departments reviewed for this study. 

TABLE 5: SUMMARY OF FIRE DEPARTMENT RADIO COMMUNICATION ISSUES

Topic Area Issue 

Physical environment • Canadian & Mexican borders 

• Topography and terrain Poor Reception 

Interference • Neighboring jurisdictions 

• Wireless communications 

High-rise and other structures • Poor communications 

Interior Communications Tunnels and underground 

structures • Poor communications 

Hazardous conditions • Water exposure 

• Visibility Unsuitable Equipment 

Personal protective equipment • Self-Contained Breathing 

Apparatus 

System Design Inadequate infrastructure 

• Lack of repeaters and tower 

sites 

• Lack of channels and 

frequencies 

System Capacity System capacity • Inadequate capacity 

Mutual aid • Cannot communicate 

Interoperability Other city departments • Cannot communicate 

POOR RECEPTION

International Border 

• Problems – Departments located on or near the Canadian and Mexican borders of 

the United States often experience problems with signal strength and interference. 

Along the Canadian border, some localities have limited frequency space because 

Canada is reclaiming some of the VHF frequencies and essentially narrowing the 
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available bandwidth. Localities located on the Mexican border are often plagued 

with interference from sources across the border. 

• Solutions –The cities of Bellingham and Everett, WA, which experience radio 

communications difficulties because of their proximity to the Canadian border, 

are upgrading to an 800-MHz radio system. San Diego, CA, which experienced 

interference because of its location on the Mexican border, upgraded to an 800-

MHz radio system in the early 1990s. 

Topography and Terrain 

• Problems – Hills, canyons, mountains, and forests can often cause interference 

and dead spots, and the shadowing from mountains also poses similar signal 

disturbances. 

• Solutions – The City of Los Angeles encompasses 470 square miles that include 

hills, canyons, and mountains. Its fire department often experiences coverage 

issues because of this diverse topography. To overcome these challenges, Los 

Angeles has worked carefully on the strategic design and placement of radio 

system infrastructure (such as towers and repeaters). The Boulder Rural Fire 

Department even uses “human repeaters” when necessary. The City of Portland, 

OR, located behind the West Hills and close to volcanoes Mount Hood and Mount 

Saint Helens, experiences similar dead spots and communications difficulties. To 

combat these obstacles, Portland constructed a large antenna above the West 

Hills. 

Neighboring Jurisdictions 

• Problems – The radio systems of neighboring jurisdictions sometimes cause 

interference for fire departments. This occurs when adjacent towns operate on 

similar frequencies, and can sometimes prevent one department from sending or 

receiving messages. One jurisdiction may be at a higher elevation than the other 

and have higher towers. 

• Solutions – The Springfield, NJ Fire Department has taken steps to solve their 

interference problems with local jurisdictions and discussions are underway to 

investigate the feasibility of trunking the current radio system. This may prove an 

effective alternative to upgrading; in Springfield, there are not enough frequencies 

available for the department to transition to an 800- or 900-MHz system. 

Gettysburg, a rural city in Ohio, would like to upgrade it current radio system too, 

but does not have the funds to do so. 
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Wireless Communications 

• Problems – Many jurisdictions experience problems with the Nextel cellular 

phone system. The Nextel system, which operates on the 800-MHz band, seems 

to be incompatible with the pre-existing radio communication systems also in the 

800-MHz band. 

• Solutions – Fairfax County, VA’s public safety system is experiencing system 

coverage degradation from Nextel (interference), and has proposed moving 

Nextel out of the 800-MHz band. The county has developed this plan as a means 

of avoiding reorganization or restructuring of its public safety radio system. 

Portland, OR, which experiences similar problems, had Nextel and the fire 

department swap frequencies to solve the problem. The fire department gave up a 

channel on the end of their radio spectrum for Nextel’s channel in the middle of 

the city’s band. 

Clark County, NV is awaiting final approval between the FCC and Nextel on a 

plan that addresses interference to public safety communications in the 800-MHz 

band. This plan is known as the Joint Commentor’s Consensus Plan. 

INTERIOR COMMUNICATIONS – LARGE STRUCTURES

High-Rise and Other Structures 

• Problems – One of the most significant problems facing firefighters inside a 

high-rise structure is the ability to communicate reliably among firefighters and 

with the command post. Portable radios often do not have the RF power output 

necessary to communicate through the barriers inside the structure and reach the 

outside. Many of the cities reviewed have problems communicating during highrise operations. 

• Solutions – Jurisdictions have managed this problem in different ways, depending 

on the specific nature of the communication challenge. Pittsburgh, which uses a 

centralized UHF communications system for all city services, encounters most of 

its problems in large and high-rise structures, especially sub-ground or tunnel 

areas. The city solves communications problems with a talk-around system that 

uses two-way radios for a 1⁄2-mile communications radius. 

Dallas, TX and San Diego, CA solve their high-rise and structural communication 

problems by relaying messages via “runners” through egress stairwells. For 

special events, such as the 2003 Super Bowl and events at the San Diego 

Convention Center, the San Diego Fire Department uses a Mobile COW (Cellular 

on Wheels), which acts as a mobile antenna to repeat communications outside a 

building. 
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In Charlotte, NC the fire department is testing a mobile repeater and has reported 

some success in overcoming communications difficulties during interior 

operations, where the department uses simplex mode—radio to radio—to 

communicate. A mobile repeater adds signal strength to the interior of the 

structure, allowing firefighters to better communicate. 

Schaumburg, IL has a new 800-MHz system with four antenna sites. Fire 

department officials have reported dramatically improved communications during 

structural firefighting events. Before the new system, the fire department 

experienced dead spots throughout the village and problems in high-rise 

structures, typically constructed of concrete and Lexan glass. Additionally, new 

building codes required installation of signal boosters during construction for 

certain types of buildings. 

Phoenix, AZ uses a conventional direct radio communication system in VHF. 

Two tower sites and diversity receivers comprise the primary infrastructure. The 

receivers allow the department to communicate without talk-around channels or 

runners. The diversity receiver operates like small radio towers and accepts the 

emitted radio signal on several antennas with a radius of 2 square miles. The 

department operates 24 VHF channels, and there are 36 diversity receivers per 

channel. This system works well in high-rise and other large structures. However, 

it does have its drawbacks. The two most common challenges are fade and 

feedback. 

Many new buildings in Boston, MA, Clark County, NV, and Fairfax County, VA 

are installing bi-directional amplifiers. Bi-directional amplifiers, commonly 

known as BDAs, are used for improving/correcting portable radio 

communications to, from, and within large structures. These BDAs let fire 

departments operate their fire department channels within a building. 

Tunnels and Underground Structures 

• Problems – Road tunnels, often constructed with massive amounts of concrete 

and steel, create a manmade barrier to radio communications and pose a serious 

threat to firefighters. Other underground structures yield similar problems. 

• Solutions – The City of Boston is attempting to preempt communications 

difficulties while it constructs a major underground expressway. The city reported 

success with using a “leaky cable” device in its Ted Williams Tunnel, and plans 

to install the same device in the new expressway. This leaky cable is a “byproduct 

of conventional coaxial cable with small slits cut through its layers that allow RF 

signal to seep out in amounts strong enough to cover small areas of square 

footage.” [296] 
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UNSUITABLE EQUIPMENT

Water Exposure 

• Problems – Prolonged exposure to water can decrease the effectiveness of 

portable radios. If a radio system is antiquated, water exposure can cause serious 

equipment damage and endanger firefighters.

• Solutions – The straightforward solution to water exposure problems is to 

purchase new, waterproof equipment. The Milwaukee, WI Fire Department has 

reported no problems with its new portable radios; they are specially designed to 

be submerged in water without damage. 

Self-Contained Breathing Apparatus 

• Problems – Many firefighters struggle with the portable radio and the ease of 

using it in a zero-visibility environment while wearing bulky fire department 

gloves. 

• Solutions – The Schaumburg, IL Fire Department alleviates this problem by 

programming the extremes of the channel selector on the portable radio (selector 

turned all the way left or right) to the same, recognizable channel (usually 

dispatch) regardless of zone selection. So, if the firefighters operating in a zerovisibility environment accidentally change the radio from the tactical operations 

channel and cannot find it again, they can turn the selector all the way in either 

direction and still talk to a dispatcher in the event they need help. 

SYSTEM DESIGN

Lack of Repeaters and Tower Sites 

• Problems – Some of the fire departments reviewed experienced problems with 

radio communications due to a lack of essential infrastructure, such as repeaters 

and towers. In most cases, system infrastructures were insufficient. In other cases, 

poor system design and placement of infrastructure were the problem. 

• Solutions – San Francisco alleviated problems by switching from a 400-MHz 

radio system to an 800-MHz radio system 8 years ago. The newer system 

accommodates more working channels (16, with three controlled for dispatch and 

one for each of the 10 battalions) and interoperability. The department has also 

added more towers and repeaters and is currently upgrading the system with 

portable repeaters, as well as moving repeaters to higher elevations to prevent 

interference from high-rise buildings. 
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Similarly, the Wichita, KS Fire Department solved communication difficulties by 

switching to an 800-MHz trunked system 10 years ago. Each company officer has 

a portable radio. 

Chicago has solved communication problems by deploying a diverse multisimulcast radio system and 10 transmitter sites (per channel). The system has up 

to 32 receivers within any area it serves (12 square miles). Because of this, 

communications with dispatch via portable radios have highly improved. 

Los Angeles’s problems from the city’ size and diverse terrain and topography 

have been alleviated by incorporating backup repeater sites in these areas. The 

city has solved communication problems in subways and tunnels by wiring them 

with underground cables, which carry a signal for four or five of the fire 

department channels. 

Lack of Frequencies or Channels 

• Problems – Some fire departments have a limited number of tactical channels on 

their radio systems. These departments are vulnerable to communications 

problems when multiple incidents occur at the same time. 

• Solutions – Everett, WA accesses a single dispatch channel and a single tactical 

channel, which can complicate communications during fire incidents. To alleviate 

concerns, the department is upgrading to an 800-MHz system. 

SYSTEM CAPACITY

Many cities reported no concerns with system capacity, including Austin and San 

Antonio, Phoenix, Charlotte, Los Angeles, and Portland. These departments have 

standard operating procedures designed to shut down various parts of the system (e.g., the 

private line function and interconnect system of an 800-MHz radio system) to ensure no 

overcapacity. 

INTEROPERABILITY

• Problems – Often departments do not have the capabilities to communicate with 

other emergency departments (e.g., fire, police, public works) or with another 

neighboring jurisdiction using their own communications system. This is essential 

for exchanging information in mutual-aid calls, mass casualty incidents, or special 

events. 

• Solutions – Many departments are currently in the process of upgrading its 

communication systems to 800-MHz, specifically for interoperability purposes. 

Others have used alternate technologies or methods to improve or create 

interoperability. Following are a few examples. 
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A Boston Fire Department chief, acting as the incident commander, is collocated 

with an incident commander from another department. 

In Charlotte, NC all mutual-aid partners and chief-level officers in other 

departments are provided with radios. Similarly, departments in Dallas and San 

Antonio communicate with the police department through a “patch” system. 

Dispatch will patch police and fire together, and they can talk directly to one 

another. 

Chicago is developing a permanent solution to its interoperability problems, 

which include an inability to talk directly with law enforcement and EMS, as 

those departments operate on a different radio system. Because the fire 

department and EMS respond together on most incidents, the fire department has 

access to the EMS radio system (VHF) and the police and EMS radio system 

(UHF). Additionally, the department deploys a command vehicle, outfitted with a 

suite of radios that allow communication with all departments, to every major 

incident. 

In San Diego, the fire department uses a Motorola 800-MHz system, which has 

been in place for 11 years. The operations units also carry VHF portables because 

neighboring departments (recipients of mutual aid) use this system (e.g., 

California Department of Forestry). 

Communications Problems in Firefighter Fatalities 

Fire department communications have been cited as a contributing factor to the death or 

serious injury of numerous firefighters. The deaths have not been directly attributed to 

failures in radio communications. Rather when communications issues are cited, they are 

frequently problems in transmissions, standard operating procedures, or unsuitable 

equipment. Even when such issues strand a firefighter, casualties are generally associated 

with the fire, and few records are kept on the issues with portable radios. But review of 

the various departments and of fire literature revealed some instances where failed radio 

communications were at issue. 

In Syracuse, NY, four firefighters perished in 1978 while fighting a fire in a three-story, 

wood-frame apartment building. Reports attributed the deaths to failed radio 

communications. While failed radio transmissions contributed to past casualties, 

Syracuse was of particular note due to the number of staff who died. 

The trapped firefighters, confined on the third floor by a rapidly spreading fire, made 

several calls for help which went unheeded by dispatch, but which were heard by an 

observer who immediately reported the transmission to a fire officer on the scene. Thirtyseven minutes into the incident, the first of the fatalities was found. [123] 

Five firefighters were killed at a fire in Hackensack, NJ when the bowstring roof of a car 

dealership collapsed. Due to changing fire conditions, a battalion chief ordered all 

personnel to evacuate the structure. This order was never acknowledged nor repeated by 
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TriData Corporation 28 September 2003 

the dispatch center. The roof fell before the personnel could exit the structure. [335]

Hackensack had only one radio channel for both dispatch and tactical operations. Heavy 

traffic overwhelmed the inadequate tactical channel, and the firefighters’ transmissions 

for help were overridden by transmissions from dispatchers. 

A similar situation occurred in Brackenridge, PA after the floor of a commercial structure 

collapsed. Heavy radio traffic led the crew to switch from the primary incident channel to 

an alternate tactical channel — effectively cutting them off from the incident commander 

and the rest of the crews on the scene. The Brackenridge casualties resulted from radio 

operational issues; with only one channel for dispatch and tactical operations, the system 

was overloaded and dispatchers overrode transmissions from the fire ground. [339]

Unsuitable equipment and product design resulted in the deaths of two firefighters and 

the injury of a third at the Indianapolis Athletic Club during 1992. The injured firefighter, 

a captain, reportedly activated the emergency button on his portable radio and made 

several unsuccessful attempts to radio for help. While the push-to-talk button on the radio 

was easy to engage with a gloved hand, he had to remove his glove to use the emergency 

button, and seriously burned his hand. [337] Insufficient training might have played a 

role in the casualties. The department had switched to an 800-MHz system two weeks 

before the fire. This switch could have been responsible for the delay in acknowledging 

and processing a request for a second alarm. 

Two firefighters were killed and two more injured while fighting a townhouse fire in 

Washington, DC in 1999. The firefighters were caught in a flashover while attempting to 

suppress a basement fire. Department personnel were using frequencies that were 15 kHz 

apart, as recommended by NFPA. But in the past they had experienced problems with 

interference or bleed over between channels. This interference may have affected the 

ability of personnel operating on the scene to hear messages from the incident 

commander. [338] 
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TriData Corporation 29 September 2003 

CHAPTER IV: STRUCTURE COMMUNICATIONS ISSUES 

Buildings and other structures pose difficult problems for wireless (radio) 

communications. Whether communication is via hand-held radio or personal cellular 

phone, communications to, from, and within structures can degrade depending on a 

variety of factors. These factors include multipath effects, reflection from coated exterior 

glass, non-line-of-sight path loss, and signal absorption in the building construction 

materials, among others. The communications problems may be compounded by lack of a 

repeater to amplify and retransmit the signal or by poor placement of the repeater. RF 

propagation in structures can be so poor that there may be areas where the signal is 

virtually nonexistent, rendering radio communication impossible. Those who design and 

select firefighter communications systems cannot dictate what building materials or 

methods are used in structures, but they can conduct research and select the radio system 

designs and deployments that provide significantly improved radio communications in 

this extremely difficult environment.4

Communication Problems Inherent in Structures 

MULTIPATH

Multipath fading and noise is a major cause of poor radio performance. Multipath is a 

phenomenon that results from the fact that a transmitted signal does not arrive at the 

receiver solely from a single straight line-of-sight path. Because there are obstacles in the 

path of a transmitted radio signal, the signal may be reflected multiple times and in 

multiple paths, and arrive at the receiver from various directions along various paths, 

with various signal strengths per path. In fact, a radio signal received by a firefighter 

within a building is rarely a signal that traveled directly by line of sight from the 

transmitter. In general, the radio signal received by a firefighter’s radio is the 

combination of a number of radio signals from different directions. This phenomenon can 

have the effect of nulling or canceling the signal of interest and result in a temporary loss 

of the radio link. The sources of these various component radio signals are: 

• Diffraction – occurs when radio signals hit the edge of an object causing the radio 

waves to bend around the object. 

• Reflections – occurs when radio signals hit an object that acts as a conductor, 

such as a metal post, or a dielectric; a perfect conductor reflects all RF signals 

while a perfect insulator reflects none.5

• Scattering – occurs when radio signals hit nearby small objects such as lighting 

fixtures or even bumps on a rough wall. 

The individual signals caused by reflection, diffraction, and scattering that arrive at the 

firefighters radio are collectively known as multipath signals. Multipath is a set of 

 

4

 It is, however, not inconceivable that building features affecting emergency communications might be a 

consideration in building design or even codes in the future. 

5

 Neither perfect conductors nor perfect insulators exist. In the real world, most materials act as dielectrics. 
NIOSH Firefighter Radio Communications Chapter IV 

TriData Corporation September 2003 30

reflections and direct waves, with each of these multipath signals traveling a different 

path to the radio. These paths will have different lengths and different number of 

reflections and are characterized by varying signal strengths caused by passing through 

materials that reflect (and absorb) differing amounts of energy. The results are 

unpredictable delays in transmission and increased attenuation and time dispersion, or a 

“smearing” or spreading out of the signal 

When these various signals combine in the receiving radio, the randomly phased signals 

add together (Figure 1).6 Depending on the exact phases the resulting radio signal can 

increase or essentially disappear. This effect is called multipath fading. Even in cases in 

which there is a strong signal and a direct line of sight to the receiver, it may be 

impossible to use a radio due to multipath fading. For example, radio wave propagation 

inside a building with materials that reflect RF energy efficiently (e.g., metallic materials) 

can have areas where the signal essentially disappears because the reflections are large 

enough to effectively cancel the direct radio signal. 

FIGURE 1: MULTIPATH REFLECTIONS COMBINE AT THE RECEIVER

Source: IEEE Internet Computing Online. 

http://www.computer.org/internet/v6n1/fig3.htm. 

Multipath signals (that is, reflection, scattering, and diffraction) also cause radio signal 

distortion (noise) as well as additional signal propagation losses (attenuation). Figure 2 

shows two key properties of multipath fading, amplitude and period. The fading 

amplitude is the amount of signal amplification or reduction and is a function of position. 

Fading period, the time between fades, is a function of speed (both the firefighters’ 

movement and the speed of moving objects, if any, from which multipath signals are 

reflecting). Because fading level varies by physical position, frequently a firefighter 

needs only move a few inches to get a 20-dB change in signal, for better or worse. [243] 

Advanced automatic gain control (AGC) techniques have been developed to compensate 

for this effect, thereby increasing the operational dynamic range of the receiver. Even 

 

6

 Radio waves are characterized as sine waves. When the signal is reflected off of a surface, it travels a 

longer path to its destination. As a result, the reflected radio wave may arrive at the receiver at a different 

point in the sine cycle. This cycle offset is referred to as phase. 
NIOSH Firefighter Radio Communications Chapter IV 

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these systems, however, usually operate with fixed time constants that cannot fully 

compensate for the effects when the signals vary quickly. 

On the other hand, because the firefighter is moving slowly and the objects around him 

remain stationary, the fading period can be long. In other words, a slowly moving 

firefighter can remain in a fade area. In digital communications, this situation can lead to 

periods of time where the error rates are too high to be corrected by error-correcting 

algorithms and result in unintelligible voices or lost communications. In analog systems, 

this fading phenomenon is exhibited in noise and static. The human brain acts as the 

correction algorithm in this case. But the brain tries to synthetically “fill in the gaps” 

based on contextual factors and, while it performs this error correction at a remarkable 

level, the listener may misconstrue messages. 

FIGURE 2: FADING RATE AND AMPLITUDE

Source: Georgia Institute of Technology, Smart Antenna Research Laboratory 

http://users.ece.gatech.edu/~mai/tutorial_multipath.htm 

It is impossible to find a building that does not have multipath reflections, diffraction 

around sharp edges, or scattering from wall, window, ceiling, or floor surfaces. As noted 

earlier, a perfect conductor reflects 100 percent of RF energy while a perfect insulator 

reflects none. In practice, most materials act like dielectrics that partially reflect (with a 

180-degree phase shift) and partially refract (transmits through the material and then 

bends) signals incident upon them. Metallic walls are the best reflectors in buildings, but 

in practice even insulating materials cause significant reflections. An all-wood or allfiberglass structure is better for radio propagation than the typical building, but it too will 

still have reflections, multipath, and other radio propagation disturbances that make 

communication worse than outdoors. 

Propagation effects also become worse in large buildings, such as high rises, or in other 

large, complex structures. As the number of obstacles the radio signal passes through 

increases, such as the successive floors of a high-rise building, the signal degrades from 

multipath reflection, diffraction, and scattering. The signal strength will vary 

considerably from position to position on a particular floor as a result of the changing 

phases and signal strengths of the various multipath signals from within the building and 
NIOSH Firefighter Radio Communications Chapter IV 

TriData Corporation September 2003 32

from nearby buildings. [290] Consider the transmission geometries as a signal propagates 

from ground level to a receiver located on the opposite side of a high-rise building. In this 

case, the signal strength will degrade significantly. Houses and other smaller residential 

structures are typically less problematical as they are constructed largely of insulators that 

reflect less efficiently, such as wood, and have fewer reflective surfaces (less floors, 

furniture, and walls). Unfortunately, it is presently impossible to effectively reduce 

multipath through building design. 

In general, multipath fading is a major contributor to inadequate radio operation inside 

buildings. 

NON-LINE-OF-SIGHT PATH LOSS

One of the largest causes of signal degradation is non-line-of-site (NLOS) path loss. As 

discussed above, it is common for communications in structures that no direct path exists 

from the transmitting radio to the receiving radio. Signals radiating from the transmitting 

antenna reach the receiving radio only by hitting obstacles and reflecting. In a simple 

structure such as a residential building, it may only take one or two reflections to reach 

the receiving radio. In a more complex building, the reflections can number orders of 

magnitude higher. The result of the reflections is an increase in distance that the signal 

travels between transmitter and receiver. In outdoors situations, the path losses are 

inversely proportional to the distance traveled raised to the fourth. Indoor path loss is 

higher.If the path traveled is doubled by reflections, the loss will be at least 16 times 

greater than if the direct path had existed. The NLOS path distance could easily be much 

more than twice the direct path in a high rise. 

ABSORPTION

Another source of poor radio performance can be signal absorption by building materials. 

NIST has performed extensive studies of electromagnetic signal attenuation in 

construction material from 0.5 to 8.0 GHz. [78,79,80] The results have shown that the 

majority of building materials are relatively transparent to electromagnetic signals for the 

application of using RF to survey through walls. For example, a 1-milliwatt (mW) 

broadband pulse (0.5 to 2.0 GHz) will penetrate slightly less than 2.5 feet of reinforced 

concrete and still be above the noise floor of a typical receiver. Wood or concrete block, 

with its hollow cores, absorbs much less signal than poured concrete and, therefore is 

easier to penetrate and causes less problems to radio communications. In general, signal 

attenuation from absorption increases with increasing frequency. Thus, lower frequencies 

such as very low frequency (VLF) and medium frequency (MF) bands will penetrate 

building material and even earth to a considerable distance, while 800-MHz ultra high 

frequencies (UHF) will not. Unfortunately, due to historical factors and spectrum use 

regulated by the FCC, firefighter radio communications generally operate at frequencies 

between 100 and 900 MHz. With these frequencies, cumulative signal attenuation can be 

a serious problem. 
NIOSH Firefighter Radio Communications Chapter IV 

TriData Corporation September 2003 33

BUILDING CONSTRUCTION

Modern construction methods and materials for large commercial buildings have changed 

quite substantially and can be a source of poor radio performance. Curtain-wall 

construction (today's approach for large high-rise buildings) means that the walls are 

“hung” from the structure (typically steel). The walls are generally glass, frequently 

reflective to radio signals. The glass material used in the windows themselves is RF 

friendly, but the windows usually contain tinting using a metallic-based composite 

embedded in the glass which can significantly shield and reflect radio signals. Even when 

pre-cast concrete panels are used as the “curtain,” there will be lots of “ribbon” window 

area. Steel or some other metal will be the superstructure. The steel may become a 

problem at frequencies where wavelengths are twice the distance between the structural 

beams or longer. The reflective coatings on the large window surfaces, usually metallic, 

are also culprits in poor radio performance. 

The large number of stories that modern construction methods allow also affects radio 

performance. Building height contributes several factors that degrade communication in 

structures: NLOS propagation to and from the exterior ground level; and propagation 

through more building materials (floors, walls, etc.) which increases the absorption, 

reflection, and refraction of the radio signals off and through these materials. These 

factors increase distances traveled by signals and exacerbate multipath fading conditions 

and create the need for repeaters (see below). 

By contrast, even though older buildings are usually thick-walled construction they often 

are more easily penetrated by radio waves because of the different materials used in their 

construction. Support for upper stories may also include a substructure separate from the 

walled construction, but not to the same extent as current high-rise construction. Many 

older buildings have thicker walls, because the walls are the primary support. However, 

buildings constructed in this manner usually are not tall, perhaps four or five stories. 

Older buildings with thick masonry walls, especially of concrete, can cause radio 

reception problems from absorption. But because their construction limits the number of 

stories, radio signals need only pass through a few floors to reach the firefighters within. 

On the surface, it would appear that transmission in older concrete-based buildings 

should not be a problem; however, many older buildings indeed are not conducive to 

radio communications. While each building is unique and requires careful modeling to 

fully understand the propagation characteristics, several common factors can impede 

radio transmission within these structures, including: 

• Many older buildings have replaced windows with newer tinted products. 

• Fiberglass insulation, even in wood structures, often has a metallic backing. 

• Older lead-based paints used on interior walls may still exist in the under-layers 

of paint. 

• Metallic furniture is still in common use today. This furniture includes desks, 

shelving, and cabinets—virtually all office file cabinets are constructed from 

metal. 
NIOSH Firefighter Radio Communications Chapter IV 

TriData Corporation September 2003 34

• In addition to rebar, concrete reinforcing wire mesh may be used in older 

buildings to provide increased strength and to mitigate building damage from 

environmental hazards such as earthquakes. While the mesh in general may 

somewhat impede radio transmission, in some cases it may be worse than others 

depending on the size and geometry of the mesh patterns in relation to the 

wavelength of the radio transmission. 

• The majority of internal wall construction today in office buildings today use 

drywall-over-steel framing material. Internal office build-out in even the oldest 

buildings frequently changes with new tenants or new requirements. 

So even in structures where the inherent building properties may appear to be more RF 

friendly, multiple factors can affect transmission 

Studies have found that placement of repeaters that amplify and retransmit radio signals 

can have a large impact on coverage within a building. [244,290] For example, a repeater 

positioned such that the radio waves strike the building façade directly at a 90-degree 

angle results in very little energy reflecting from the surface. Except for the absorption 

characteristic of the material, the radio signal passes through to the building interior. 

Signals that graze the surface of a building have greater reflection off the façade and 

fewer signals entering the building. The result can be poor radio coverage even on a floor 

at the same height as the repeater. Experience has shown that placing a repeater on the 

roof of a building can provide the best coverage in many cases as the signal enters the 

building at a near 90-degree angle and avoids the typical coated, reflective glass on 

today’s modern office buildings. [244,290] 

RADIO SYSTEM CONSIDERATIONS

The problems inherent in radio communications into, from, and within structures should 

be addressed on several fronts whenever possible. Some of the options are: 

• Radio system design – Provide redundant paths for each receiver if at all possible. 

[308] 

• Antenna system design – Accommodate dual-diversity antennas used at each 

receiver at a minimum. Provide sufficient repeater antenna gain for hand-held 

radio transmissions to be received by the incident commander. Place repeater 

antennas properly. [308] 

• Signal/waveform design – Incorporate techniques that mitigate multipath, such as 

spread spectrum radio design with high signal-to-channel bandwidth ratio. 

Example spread spectrum waveforms currently in use to combat multipath are 

CDMA (common in cellular systems), ultra wideband (UWB) in development for 

robust in-building communications and “see-through walls” radar products, 

frequency hopping (available in emergency personnel evacuation paging 

systems), and OFDM (used for television broadcast applications and in-building 

radio location systems currently being developed). Other options include using 

narrowband multipath reduction digital signal processing algorithms, such as 
NIOSH Firefighter Radio Communications Chapter IV 

TriData Corporation September 2003 35

equalization. These algorithms essentially function as AGC circuits that are 

designed and implemented in digital signal processors. These algorithms (and 

circuits) can remove the deep amplitude notches that otherwise occur from 

fading.7

[308] 

• Building/environment design – Firefighters cannot dictate building methods or 

materials, but they may be able to influence modifications for their use. For 

example, leaky feeder cable could be built into structures for firefighters, HVAC 

systems could be specially modified to act as waveguides [164] for firefighter 

communications, or a method to communicate by coupling RF signals onto the ac 

power lines in a structure could be provided. [308] 

Signal absorption can be addressed directly if it is possible to select a radio frequency 

that has minimal absorption in construction materials or has other characteristics to allow 

penetration of structures. Medium frequency waves penetrate building materials more 

readily and can parasitically couple to building conductors such as telephone lines or ac 

power lines, both of which can act as a distributed antenna within the structure. [115, 

116,128,129,130,175,198,211,288] Another way to address signal absorption is to begin 

with more radio transmit power and higher gain antennas. A mobile repeater properly 

sited at a fire scene will help get signal into a building, but because the firefighters’ handheld radios have limited transmit power, the repeater needs to have a high-gain antennas 

to enhance the reception of communications from the firefighters within the structure. 

In general, the radio systems used by firefighters do not have the required features for 

operation in difficult indoor areas. 

Risk to Firefighters 

As a result of the radio communications problems inherent in structures, high-rise 

structures, as well as warehouses and other non-residential structures, pose the greatest 

challenges to firefighter radio communication. These buildings tend to be those where 

communication problems are of most concern. While fires are fewer in number in these 

properties than in typical one- and two-family dwellings, firefighters are at greatest risk 

in these buildings. As illustrated in Figure 3, basic industry, manufacturing, vacant 

buildings and construction sites, retail stores and commercial offices, storage facilities, 

and apartment buildings rank higher in risk of injury to firefighters than the typical home. 

 

7

 The AGC design and associated time constants need to be carefully selected as to not impair the signal-tonoise ratio of the signal or saturate components in the receiver chain. 
NIOSH Firefighter Radio Communications Chapter IV 

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FIGURE 3: FIREFIGHTER INJURY RATE IN STRUCTURES

Source: Fire in the United States 1989-1998, United States Fire Administration 

Radio Spectrum Considerations 

The radio spectrum is the lowest end of the larger electromagnetic spectrum. This energy 

spectrum ranges from radio waves to gamma rays. Radio waves, visible light, X-rays, and 

all the other parts of the electromagnetic spectrum are fundamentally the same thing. 

They are all electromagnetic radiation that travels and spreads out as it goes (called 

propagation) and can be expressed in terms of energy, wavelength, or frequency. 

RADIO FREQUENCY BANDS

The radio spectrum is segregated into frequency bands, each with propagation 

characteristics and regulated uses. The use of these frequencies bands in the U.S. is 

licensed and regulated by the Federal Communications Commission (FCC). The use of 

all radio frequencies (and equipment) is determined by the rules and regulations issued by 

the FCC in conjunction with the National Telecommunications and Information 

Administration (NTIA). All radio users must abide by them. Much of the current 

assignment of frequencies is founded on historical use and not necessarily on the 

optimum assignment of the spectrum, based on the physical properties of the spectrum, to 

specific applications. 
NIOSH Firefighter Radio Communications Chapter IV 

TriData Corporation September 2003 37

FIGURE 4: RADIO SPECTRUM

Source: Adapted from Allocation of Radio Spectrum in the United States, 

http://www.jneuhaus.com/fccindex/spectrum.html#table_of_contents 

Lower frequencies propagate further than higher frequencies, both through the air and 

into the ground. For propagation through the air, the spectrum can be divided into three 

sub-spectra by the type of propagation exhibited: 

• Surface: The longest electromagnetic waves, below 500 kHz, tend to follow the 

curvature of the Earth, guided between the Earth and the ionized layers of the 

upper atmosphere (i.e., the ionosphere). 

• Sky: High frequency waves, 3–30 MHz, are reflected by the ionosphere and are 

capable of propagation around the Earth. 

• Line-of-sight: Above 1 GHz, electromagnetic waves behave much like light 

propagating through a clear, reasonably uniform atmosphere. When originating 

from a point source, they propagate in all directions. 

The intermediate frequencies from 500 kHz to 3 MHz and 30 MHz to 1 GHz are 

transition bands where the propagation characteristics in the atmosphere are more 

complex. 

Despite the propagation advantages, a disadvantage of the lower frequency bands, 

however, is the limited amount of available spectrum. At very low frequency (VLF) the 

spectrum available for public safety radio is only 27 kHz. This is barely enough to pass a 

single analog voice channel. As a result, this band is primarily used for applications that 

only require low-speed data transmission. By contrast, the super high frequency (SHF) 

band has 27 GHz of spectrum, a million times the available spectrum at VLF, but it 

suffers from poor propagation characteristics. Also, radio equipment, particularly 

antennas, is frequently larger at lower frequencies. As a result, the equipment to support 

the use of these frequencies may be too cumbersome to be practical on the fireground. 

Table 6 shows some of the basic uses of the frequency bands and some of the more 

relevant propagation characteristics. 

ELF

 30 

km 

| 3 

km 

| 300 

m 

| 30

m

| 3

m

| 30

cm

| 3

cm

| 3 

mm 

| 

VLF LF MF HF VHF UHF SHF EHF Infrared Visible

Light

 | 

10 

kHz | 

100 

kHz | 

1 

MHz | 

10

MHz |

100

MHz |

1

GHz |

10

GHz | 

100 

GHz 

 Surface Waves Sky Waves Line-of-Sight Waves 
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TABLE 6: RADIO FREQUENCY BANDS

Band 

Frequency 

Range Wavelength General Applications 

Major Propagation 

Characteristics 

ELF 300–3000 Hz 100–1000 km 

Navigation, long distance 

communication with 

submarines 

Wave tube between 

Earth surface and the 

ionosphere 

VLF 3–30 kHz 10–100 km 

Navigation, long distance 

communication, emergency 

paging 

Ground propagation; 

stable 

LF 30–300 kHz 1–10 km Navigation, long distance 

communication with ships 

Ground propagation; 

stable 

MF 300–3000 kHz 100–1000 m 

AM broadcasting, radio 

navigation, powerline 

communications, mine 

voice communications 

Ground-wave, sky-wave 

propagation; fading 

HF 3–30 MHz 10–100 m 

Radio broadcasting, fixed 

point-to-point (around the 

world) 

Large perturbation, 

reflection in ionosphere 

VHF 30–300 MHz 1–10 m Radio & TV broadcasting, 

mobile services Diffraction 

UHF 300–3000 MHz 10–100 cm 

Cellular telephony (GSM, 

NMT, AMPS), fixed pointto-point, satellite, radar 

Shadowing by mountains 

and building 

SHF 3–30 GHz 1–10 cm 

Broadband indoor systems, 

microwave links, satellite 

communications 

Attenuation due to rain, 

snow, and fog 

EHF 30–300 GHz 1–10 mm LOS communication (short 

distance or satellite) 

Attenuation due to rain, 

snow, and gases 

Source: Adapted from http://www.s3.kth.se/radio/COURSES/RKBASIC_2E1511_2001/lecture_1.pdf. 

Satellites operate at ultra high frequency (UHF), super high frequency (SHF), and 

extremely high frequency (EHF). Table 7 shows the various frequencies and examples of 

some of the major satellites that operate in these bands. The frequencies represent typical 

uplink and downlink transmissions. 

TABLE 7: SATELLITE FREQUENCY BANDS

Band Frequency 

Range Bandwidth User Satellites 

 200 – 400 MHz 160 Hz Military FLTSAT, LEASAT UHF 

L 1.5 – 1.6 GHz 47 MHz Commercial MARISAT, INMARSAT 

C 6/4 GHz 800 MHz Commercial INTELSAT, DOMSATS, 

ANIK E 

X 8/7 GHz 500 MHz Military DSCS, SKYNET, NATO 

Ku 14/12 GHz 500 MHz Commercial INTELSAT, DOMSATS, 

ANIK E 

2500 MHz Commercial JCS 

SHF 

Ka 30/20 GHz 

1000 MHz Military DSCS IV 
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Band Frequency 

Range Bandwidth User Satellites 

Q 44/20 GHz 3500 MHz Military/DOT MILSTAR EHF 

V 64/59 GHz 5000 MHz Military CROSSLINKS 

The applications and potential applications of these frequencies are undergoing a rapid 

transformation with the growth of technological developments occurring in modern 

communications. Recent developments in digital signal processing algorithms and 

powerful, inexpensive, small hardware allow communication systems to be built that can 

use the spectrum in new ways. Systems can be built that use the narrow bands at the 

lower frequency end of the spectrum to transfer much more data or many more voice 

channels than previously possible. Another new technology, ultra wideband 

communications, uses broad swaths of the spectrum across more than one band. These 

new technologies are forcing the FCC to consider changes in spectrum allocations to 

accommodate the new spectrum users. In spite of the apparent abundance of spectrum for 

many applications, the lack of sufficient and appropriate spectrum remains a major issue. 

In June 1995, Congress empowered the Public Safety Wireless Advisory Committee 

(PSWAC) to specifically address issues relating to spectrum needs and uses for the public 

safety community. The PSWAC determined a short-term need for an additional 2.5 MHz 

of spectrum, and long-term need for an additional 25 MHz of spectrum for public safety 

use. The Balanced Budget Act of 1997 mandated the reallocation of 24 MHz of broadcast 

television spectrum by December 31, 2006, for public safety uses. However, this will not 

solve the frequency congestion issues in the near term as the Act includes provisions for 

extensions beyond 2006 if the penetration of digital television service in a given market is 

less than 85 percent. 

As a result, the uncertainty of when and if this spectrum will become available severely 

limits planning by the public safety sector and causes reluctance in manufacturers to 

invest in products and technologies for this spectrum. 

The current bands and primary allocated users are outlined below: 

Extremely Low Frequency (ELF) – The ELF band is primarily used by the Navy to 

contact submarines deep under water, depths that normal radio waves cannot penetrate. 

(Water absorbs high frequencies.) The low frequency, however, cannot broadcast much 

useful information. As such, the Navy only uses the ELF system to signal their 

submarines to come closer to the surface, and then broadcasts the actual message by other 

means. There has been some controversy about the human health effects of ELF. This is a 

relatively new band designation. 

Very Low Frequency (VLF) – The VLF band is very narrow, only 27 kHz, and currently 

allocated for uses such as low-data-rate power line communications by a power utility for 

general supervision of the power system and cable locating equipment. Radio waves in 

this band can propagate by surface waves over long distances in the air and ground waves 

penetrating long distances through the earth. At one time, these frequencies were used by 

commercial interests to transmit and receive the majority of “wireless” message traffic in 
NIOSH Firefighter Radio Communications Chapter IV 

TriData Corporation September 2003 40

a large network of stations, but today only a handful of military and government stations 

remain on the air on a regular basis. The narrowness of this band has limited the use of 

the VLF band for fireground communications to applications such as a one-way 

emergency evacuation paging system. 

Low Frequency (LF) – The LF band covers 270 kHz from 30 to 300 kHz and is currently 

used for applications such as marine and aviation navigation beacons, low-data-rate 

power line communications, and cable locating equipment. This band is also used by 

European broadcast radio for its ability to “hug the earth,” eliminating shadowing by 

mountains. 

Medium Frequency (MF) – The MF band is from 300 kHz to 3 MHz. This band currently 

includes AM radio (535 to 1605 kHz or almost half of the band), radio navigation, and 

various others. Land mobile public safety (fire, police, etc.) agencies are allocated several 

hundred kilohertz in this band. MF signals are useful in that they can propagate over 

fairly substantial distances (e.g., two mobile units could easily talk to one another with 

tens of miles of separation). However, the signals may have problems propagating 

through steel-reinforced structures. MF RF has been shown to have an ability to 

inductively or parasitically couple to conductors such as telephone and ac power lines or 

the steel tracks used for underground mining vehicles. [115,116,128,129,130,175,198, 

211,288] This type of coupling has been used to communicate for thousands of feet in 

underground mines. Miners and cave explorers have used MF for communications 

because of its ability to travel through the earth and solid rock. 

High Frequency (HF) – The HF band is used for long-distance communications because 

of its sky-wave propagation mode. The band is allocated in large part to maritime 

radiotelephone, amateur radio, and flight test stations. The new broadband power line 

communications products for in-house LAN use (e.g., HomePlug 1.0) and backhaul to the 

Internet, access power line communications (PLC), over the medium-voltage power grid 

operate in this band as well. Organizations such as the American Radio Relay League 

(ARRL) are fighting access PLC use of the HF band with the FCC. 

Very High Frequency (VHF) – Radio astronomy, cordless telephones, amateur radio, FM 

radio, television, aviation, and public/private land mobile make up a large portion of this 

band. 

Ultra High Frequency (UHF) – Radio location, new 700-MHz public safety band, 

television, satellite communications, military and other government communications, 

maritime communications, and public and private land mobile are some of the users of 

this band. 

Super High Frequency (SHF) – Radio location, radio navigation, point-to-point 

microwave, and satellites are users of this band. This band has unlicensed frequencies. 

Extremely High Frequency (EHF) – Specialized satellite. Much of this band is proposed 

for services but is not currently allocated. 
NIOSH Firefighter Radio Communications Chapter IV 

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PROPAGATION

For propagation through earth, building material, and structures, the picture is complex 

and not easily categorized. As noted under the discussion of absorption, a significant 

amount of work has been done by NIST on RF transmission through building materials 

for its program on RF surveying for construction automation. [78,79,80] In addition to 

work on signal attenuation through construction materials, the NIST study also 

characterized power attenuation in relation to material thickness, electrical permittivity, 

and dielectric constant as a function of frequency. These construction materials included 

various brick configurations, various mixtures and thicknesses of concrete, interior 

finishing materials, glass, and reinforced concrete. Measurements of the frequency 

dependency of the material dielectric and conductivity constants were curtailed due to 

funding cuts. A sample of the data taken is shown in Figure 5 for the transmission 

coefficient8 of a 102-mm-thick section of concrete vs. frequency. 

FIGURE 5: TRANSMISSION COEFFICIENT FOR CONCRETE MIXTURE #5 

Source: Adapted from NIST Construction Automation Program Report No. 3: Electromagnetic Signal 

Attenuation in Construction Materials, National Institute of Standards and Technology, 

Gaithersburg, MD. October 1997. 

The frequency dependency of RF transmissions in building material does not necessarily 

mean that the same is true for penetration into structures. Conductive screens with 

 

8

 The transmission coefficient is a measure of absorption. The higher the transmission coefficient, the lower 

the absorption in the material. 
NIOSH Firefighter Radio Communications Chapter IV 

TriData Corporation September 2003 42

openings of approximately one-half the RF wavelength or smaller attenuate the RF waves 

heavily. Typical examples of potential barriers to RF signals would be rebar grids in 

reinforced concrete or the steel support structures used in modern curtain wall buildings. 

An example of this effect is shown in Figure 6 for transmission through two different 

rebar grid patterns. [79] Both rebar grids are square patterns. Grid 1 had 140-mm spacing 

and grid 2 had 70-mm spacing. Looking at one frequency, 1.5 GHz, grid 1 is a little 

larger than a half wavelength (1/2 x 200 mm), but grid 2 is smaller. The figure shows that 

grid 1 is relatively transparent to this frequency but grid 2 attenuates it heavily, over 10 

dB more than the bigger grid. The figure also shows that the attenuation increases with 

frequency as expected. 

FIGURE 6: RF ATTENUATION THROUGH REBAR GRID

Source: Adapted from NIST Construction Automation Program Report No. 3: Electromagnetic Signal 

Attenuation in Construction Materials, National Institute of Standards and Technology, 

Gaithersburg, MD. October 1997. 
NIOSH Firefighter Radio Communications 

TriData Corporation 43 September 2003 

CHAPTER V: CURRENT TECHNOLOGY STATUS, 

KNOWLEDGE GAPS, AND RESEARCH NEEDS 

The literature search for technologies to solve firefighter communications and personnel 

location problems caused by poor RF signal propagation in structures identified several 

promising technologies, including ultra wideband (UWB), mobile area networks 

(MANet), other spread spectrum, and use of frequency bands that couple inductively/ 

parasitically to conductors, power line distribution, among others. This chapter discusses 

each of the promising technology areas identified during the literature search. Included in 

each technology section is a discussion of what the technology is, how it is applicable to 

firefighter communications or location problems, current status relative to firefighter 

communications including research to date, and, if applicable, products that demonstrate 

current or potential usefulness to the firefighter communication problem and knowledge 

gaps. Finally, for each technology, a series of recommendations are included which, if 

implemented, could lead to improved radio communications for firefighters on the 

fireground. 

Many of the areas of promise discussed in this section are state-of-the art and their 

descriptions very technical. While every attempt has been made to describe the 

technologies in a straightforward manner, to fully address the nuances of the concepts 

and to correctly describe the technology, the level of information and detail may exceed 

the interest of the casual reader. 

Ultra Wideband 

Ultra wideband (UWB) is not a truly new technology. Marconi employed the concept 

with his spark gap transmitter over 100 years ago. First fully developed in the 1960s for 

the U.S. military, the bulk of work was in the classified area for about three decades. The 

technology has been in use in radar systems for some time because the wide bandwidth 

results in very accurate timing and allows accurate ranging. [208,286] Recent advances in 

switching technology are driving the cost of UWB implementation lower, and many 

believe UWB is the potential next wave in commercial wireless communications. UWB 

offers the promise of: 

• Precision range/radio location systems 

• Robust communications in severe multipath environments such as buildings 

• Low-power systems with long battery life 

• Promises to provide a means to share spectrum without affecting current radio 

signals due to its very wide band, very low power emissions that appear as noise 

to other non-UWB receivers. [301] 

UWB technology has many applications including communications, precision 

geolocation, and radar. Its recent application to high-rate digital communications, 

particularly for use in urban environments where robust propagation in structures is 

required, is an innovative technique that combines the ability to transmit high-rate digital 

data at low power. Impulse radio is a form of UWB spread spectrum signaling with 
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multipath mitigation properties that make it particularly applicable for application in 

severe multipath environments (such as those found in urban settings and within 

structures). [152,210,282,287,305] UWB, requiring a fading margin of only 1.5 dB9

, has 

demonstrated the ability to transmit within structures where higher power narrow band 

signaling fails. [305] Many researchers and commercial companies have come to the 

conclusion that UWB technology is the most promising solution for communications and 

precision location of firefighters in urban areas and particularly in buildings where 

conventional Global Positioning System (GPS) or almost any communications using a 

sinusoidal-based waveform is subject to the issues of multipath fading. It remains to be 

seen whether UWB will emerge as a supplement or a replacement to cellular radio and 

other more traditional RF technologies. 

TECHNOLOGY DESCRIPTION

UWB is a general term for a class of signals that have much wider bandwidths than those 

found in traditional narrowband or wideband communication systems such as trunked 

radio (narrowband) and recently launched third-generation (3G) cellular (wideband). 

UWB is differentiated from these signal classes in two ways: communications bandwidth 

and the use of a carrier-less RF implementation. For communications bandwidth, the 

FCC is considering two definitions: (1) bandwidth greater than 25 percent of the center 

frequency at the –10-dB points or (2) RF bandwidth greater than 1 GHz. [292] This is in 

contrast to wideband 3G cellular, which occupies less than 4 MHz of spectrum, or 

narrowband trunked radio, which occupies 25 kHz. A UWB transceiver can function in a 

carrier-less fashion because it directly modulates an impulse with extremely sharp rise 

and fall times thereby generating a signal with a bandwidth on the order of several GHz. 

[142] Narrowband and wideband systems use an RF carrier to translate a baseband signal 

to the desired RF operations band. The transceiver is very simple for a UWB system 

because of the low power transmitted and the carrier-less implementation. Typically, the 

system will not need a power amplifier and will consist only of a pulse generator fed 

directly into an antenna. To demodulate the signal, a UWB receiver coherently detects 

the signal using a correlation receiver. No complex analog carrier circuitry is needed; 

hardware costs can be kept low once the UWB-based products become mature and 

produced in quantities. Currently, the prototype-based systems are still relatively larger 

and more expensive as the technology is still new. 

In a UWB system, a transmitter emits sequences of impulses that are detected by a 

corresponding receiver whose front-end amplifiers are synchronized and time-gated to 

the transmitted pulse sequences. Data information to be sent is modulated onto certain 

parameters of the transmitted impulse. Such parameters may include the pulse position, 

amplitude, or orientation. For example, using pulse position modulation, the transmitting 

system may time advance a pulse to indicate ‘1’ and time retard a pulse for a ‘0’. [281] A 

single bit of information is typically spread over many pulses, and the receiver system 

coherently sums up the correct number of pulses to determine the bit value. Depending 

on the system vendor and application, some UWB systems transmit many closely spaced 

 

9

 This fading margin is very low; a typical indoor cellular system is designed with 20 dB of fading margin. 
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short pulses, and others may transmit fewer pulses with larger interpulse spacing and 

some use amplitude modulation. [106] Coherent summing provides integration gain in 

the receiver. To allow a multiple access environment, each user would be assigned a 

unique pseudo noise (PN) code similar to conventional CDMA systems (such as the 

cellular service provided by Sprint or Verizon). This PN code would be used to generate 

a unique sequence of time shifts on a pulse train that allows pulses to be discriminated 

from one user to another. As each transmit-and-receive pair is active only for a very short 

period of time, many transmit-receive pairs, each with its own unique pulse sequences in 

time, can operate within the same area without causing mutual interference. 

One important advantage of spread spectrum communication techniques is the ability to 

mitigate multipath problems. Impulse radio technology has the ability to nearly eliminate 

the adverse effects of multipath fading. Typically, multipath signals result from 

reflections of the original signal. These multipath signals will, in general, travel different 

length paths to the receiver with the result being each will have a different phase. They 

add together and, depending on the phase, can increase or decrease the received signal 

magnitude. In UWB systems with very short pulses, the delayed, reflected pulses could 

be detected and ignored. Studies that tested fading performance in homes and office 

buildings found minimal multipath effects [282,287,293] Other researchers are working 

on a Rake receiver UWB implementation which will allow the combining of various 

multipath signals to improve receiver performance similar to cellular CDMA systems. 

[306] 

UWB also has important advantages in transmitting through building materials and 

structures. Generally, building materials show increasing attenuation of RF signals as 

frequency increases. For penetrating a building with an RF signal, a low frequency is 

generally better than a high frequency. UWB is carrier-less and, therefore, covers the 

spectrum from near dc (0 Hz) to the upper end of the signal bandwidth, which can be a 

few GHz. A UWB system essentially “adapts” to the attenuation characteristics of the 

material it is passing through. For a given bandwidth, the center frequency of the UWB 

signal is low which makes for better propagation through and lower absorption from 

materials. Nevertheless, in spite of these advantages UWB transmissions are still 

inherently RF signals and are fundamentally subject to the same absorption 

characteristics as other sinusoidal-based radio transmissions. In this regard, the center 

frequency and other parameters of a UWB-based system must be carefully selected to 

achieve optimum performance for a given application. 

APPLICATIONS

Communications and Networking 

Several technologies are competing for the high-data-rate, short-range market for which 

UWB is suited. These technologies include wireless LAN (IEEE 802.11a, IEEE 802.11b) 

and Bluetooth (Table 8). Figure 7 shows that none of these competing technologies 

provide nearly as much spatial capacity as UWB. [142] UWB has been demonstrated to 

rates over 100 Mbps with the potential to go to 500 Mbps. [306] 
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TABLE 8: COMPARISON OF UWB TO OTHER WIRELESS SYSTEMS 

Technology Data Rate Range Cost Power Spectrum Comments 

UWB 

50–100 Mbps 

(theoretically up 

to 500 Mbps) 

500 ft Low Low UWB 

Only high-data-rate 

WLAN in 300–500-ft 

range 

802.11 54 Mbps 90–100 ft High High 5.0 GHz Power, cost issues 

HyperLan 25 Mbps 100 ft High High 2.4 GHz 

European standard, 

same as 802.11b 

issues 

802.11b 11 Mbps 250–300 

ft Med Med 2.4 GHz Speed issues 

Home RF 11 Mbps 150 ft Med Med 2.4 GHz Lost Intel support, 

speed issues 

Bluetooth 1Mbps 30 ft Low Low 2.4 GHz Speed issues 

Source: [50] 

FIGURE 7: SPATIAL CAPACITY OF UWB 

0

100

200

300

400

500

600

700

800

900

1000

Spatial Capacity (kbps/m2)

IEEE 802.11b Bluetooth IEEE 802.11a Ultra

wideband

Source [142] 

The short pulses of UWB signaling are less susceptible to multipath fading and better 

able to penetrate building materials than competing technologies. These characteristics 

make UWB applicable to robust in-building communications. [145,284] Low-power 

transmissions will also extend battery life. Radio and radar systems could be developed 

that dynamically trade data rate, range, and power consumption/battery life. UWB is 

inherently secure as its low power, high bandwidth makes is appear to be noise to a noncoherent detection system. This makes it more difficult to intercept. 
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Imaging Systems 

Motion detection and radar are natural applications for this UWB technology. Similar to 

other radar systems, UWB radar measures the roundtrip time and angle of arrival of 

reflected pulses. Because of the multi-GHz bandwidth of the system, the resolution can 

be as accurate as 3 cm. [152] This type of application requires a directional antenna 

system to determine angle of arrival. This requirement is a problem as development of 

directional antennas with this bandwidth is difficult. 

Hand-held imaging devices with the ability to detect, range and sense motion of people or 

objects have been developed and commercially deployed for use by police departments. 

[206] An example of such a handheld radar device is Time Domain’s RadarVisionTM. The 

technology has also been used to develop ground penetrating radar systems for 

applications such as mine detection. 

Indoor Geolocation and Tracking 

Using four reference receivers provides three-dimension location of UWB transmitters to 

centimeter precision because of the short, well-defined timing of the UWB pulses. Short 

pulses allow the direct path pulse to be differentiated from multipath reflections that lag 

in time. The UWB transmitter could be a communications radio providing voice 

communications combined with location or a UWB tag used only for location. 

[152,284,327] Each firefighter equipped with a UWB radio or a tag automatically and 

continuously transmits unique data to a set of antennas located at strategic points around 

the building whose positions are precisely known. In this manner, the precise threedimensional location can be determined. These systems typically use either angle of 

arrival (AOA) or time difference of arrival (TDOA) techniques to determine the location. 

Conversely, the UWB transmissions can be picked up locally within the same room with 

a small antenna array mounted on the firefighter’s helmet. This would allow the 

firefighter to not only determine his approximate location and detect or “see” others with 

radios or tags in a smoke-filled room, but also the identity of the other firefighters in the 

vicinity. Furthermore, using this system, the firefighter may also be able to detect the 

location of other UWB-equipped firefighters in adjacent rooms or floors. Receivers 

outside could detect the location of the firefighters as well. As of September 2003, this 

technology has yet to be demonstrated in practice despite several firms’ work in this area. 

RESEARCH AND PRODUCT STATUS

Research and product development using UWB technology is an area of significant 

activity. Two players in the UWB arena are Time Domain Corporation and Multi 

Spectral Solutions, Inc. (MSSI). Time Domain has focused on large-scale 

commercialization of UWB and has taken an aggressive approach to their intellectual 

property development with a suite of pioneer patents in this area. MSSI has remained 

smaller and more focused on specialized applications for both government and 

commercial users including geolocation. [279,285] In addition, a myriad of smaller 

companies and universities have made advances in both technology and prototype 
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development of UWB-based systems, either independently or by teaming with one of the 

larger players. To date, commercial companies have shipped products using UWB 

technology to “see” through walls for use by police and firefighters as noted above. 

Æther Wire & Location, Inc., has demonstrated prototype devices for precise 3D 

location, and Intel has working prototypes of USB devices operating at 100 Mbps with 

predictions of 500 Mbps soon. These products operate in the unlicensed spectrum at 2.4 

GHz and 5 GHz. Worcester Polytechnic Institute (WPI) is also pursuing a location and 

communications system that uses a UWB technology based on a form of orthogonal 

frequency division multiplexing (OFDM). [188,235,298] The advantage of using OFDM 

is that it is spectrally shaped to reduce interference to other RF communications. WPI 

expects to have a proof-of-concept demonstration running late 2004.10 

Significant resources are being devoted to UWB research at universities, government 

agencies, and commercial companies. The most important research topics are: 

• Developing reliable channel models to predict performance and to allow 

optimized transmitter and receiver design. 

• Ongoing research in receiver design to take advantage of multipath reflections 

similar to the Rake receiver technology found in CDMA cellular systems to 

achieve signal processing gain. 

• Developing highly integrated silicon solutions to drive the cost of UWB systems 

down. Time Domain has a three-chip solution at this time. 

• Determining the effect UWB systems have on other communications systems 

such as cellular and GPS. 

ISSUES

Regulatory 

The FCC and NTIA jointly manage the radio spectrum in the United States. UWB 

devices cannot avoid emitting energy into both government and non-government 

spectrum; thus, FCC must coordinate rules with NTIA. UWB meets FCC Part 15 

constraints on incidental radiation but needs a waiver due to the intentional nature of the 

radiation. [143] Recently the FCC gave UWB companies clearance to market their 

devices commercially, but only in a limited range of frequencies and with limited power. 

[223] The ruling restricted operation of UWB communications systems to low-power 

hand-held devices in the 3.1- to 10.6-GHz frequency band. While this specification could 

provide for some communications applications, the limitations are not practical for 

geolocation or radar. However, this was a step forward for UWB proponents and was 

achieved despite objections from the Pentagon as well as GPS and cellular operators. 

Major regulatory issues remain. Usage and interference characteristics of UWB systems 

have become a heated argument in the telecommunications, broadcast, and navigation 

 

10 From a telephone conversation with Dr. John Orr, September 2, 2003. 
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communities. Numeric limits on UWB emissions and what techniques should be used to 

measure them are still being argued from both sides. 

Although the UWB power levels are essentially white noise for most applications, there 

are still concerns of cumulative interference from widespread use of UWB devices in the 

same spectrum as conventional radio communication devices, including emergency 

services, GPS, and cellular networks. [301] The regulatory agencies are looking 

particularly at bands that are used specifically for fire, police, rescue, and other critical 

services. In February 2002, the “Revision of Part 15 of the Commission’s Rules Regarding 

Ultra-Wideband Transmission Systems (ET Docket 98-153)” was adopted. This 

memorandum mentioned the public safety sector as candidates for some UWB 

applications, but it did not include provisions for the several uses of UWB for fire and 

rescue. Industry proponents objected and provided several petitions for reconsideration, 

one of which was through-wall imaging systems specifically for police, fire, and rescue. 

In February 2003, the FCC published a revision to the 2002 docket. The memorandum 

includes several pages of discussion on the topic of firefighter and police safety. The 

proposed modification to the standards was adopted and somewhat relaxed the 

specifications for these applications. While this specifications relaxation was not a major 

technical concession, the acknowledgement of the importance and the shift in the FCC and 

NTIA to allow exceptions for UWB products for the public safety sector were steps 

forward for the UWB community. An excerpt from the FCC February 2003 memorandum 

opening the specification follows: 

We agree that any technology that increases the survivability of our police, 

emergency rescue personnel and firefighters should be encouraged. As a 

result of the factors discussed in the preceding paragraphs, we are 

amending our rules to permit the operation of a through-wall imaging 

system with a center frequency above 1990 MHz at the Part 15 general 

emission limits. However, we acknowledge the concerns expressed by the 

commenters and believe that some additional operational standards should 

be implemented to ensure that operation of this equipment does not result in 

harmful interference to other radio systems that may also be employed for 

public safety purposes. We do not believe that any of these standards will 

cause operational difficulties. [163] 

The FCC has stated its intention to continue evaluating the potential impact of UWB 

devices on other communications services to see if changes are needed to the UWB 

standards. [259] Traditionally, the FCC, NTIA, and wireless community have allocated a 

specific and separate spectrum for each use to avoid interference. This concept has been 

followed since the inception of wireless communications. As a result, the notion that 

UWB will occupy the same spectrum as many of the critical functions is a change in 

thinking for all parties involved. These issues are being addressed by the FCC, NTIA 

[201], and many commercial UWB proponents, but a significant amount of work and 

testing needs to be performed before UWB becomes mainstream. This process could take 

several years. For systems operating within the current limitations, the power restrictions 

limit either the data rates or the effective range of these devices to a degree that could 

potentially cripple this technology. [13] 
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Other 

UWB antenna development is lagging behind the remaining UWB system developments. 

UWB receivers have not reached the level of development to incorporate techniques such 

as Rake receiver design needed to provide truly robust communications in severe 

multipath environments. [280] 

There are some concerns about UWB’s susceptibility to jamming by narrowband signals 

within the UWB passband. [106] 

RECOMMENDATIONS

The public safety community should develop a position in regards to supporting UWB 

deployment and the minimum requirements needed for each firefighter application. If the 

fire community’s position is to support this technology, then minimum requirements 

should be developed for firefighter applications. An organization, such as PSWAC, 

NFPA, or Project MESA11 should be used to make the community’s position known to the 

spectrum-regulating organizations. 

The public safety community, using an organization such as PSWAC, NFPA, or Project 

MESA, should support antenna research and provide input on firefighter-specific 

antenna requirements. 

The public safety community, using an organization such as PSWAC, NFPA, or Project 

MESA, should support research and design of advanced receiver architectures such as 

the Rake receiver. 

Research into electromagnetic susceptibility and compatibility should be supported 

through organizations such as PSWAC, NFPA, or Project MESA. Ideally, power and 

frequency restrictions will be lessened to make UWB more widely applicable for public 

safety applications. 

Mobile Area Networks 

Advances in mobile ad hoc wireless network (MANet) communications techniques may 

make it possible for users to communicate more reliably than with a conventional radio 

system. Often, a user may be located inside a building where communication is possible 

with other neighboring radios also inside a building, but not with the tower or with radios 

located outside the building or in other areas of the building where the RF attenuation is 

too significant. This connectivity scenario brings rise to a new concept where each peer 

 

11 Project MESA is an international partnership producing globally applicable technical specifications for 

digital mobile broadband technology, aimed initially at the sectors of public safety and disaster response. 
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radio is capable of acting as a relay or router and provides a multiple hop communication 

relay chain. In this case, one user, deep inside a building, may be able to communicate 

with another radio closer to the building perimeter. The perimeter radio then acts as a 

relay between the first user and the tower to provide successful communications. 

Originally developed for military and commercial cellular applications, this concept is 

applicable for firefighters and other first responders. Commercially, this technology has 

been gaining increased popularity for wireless voice and data networks. For example, 

potentially large cost savings could be achieved for cellular operators if they could limit 

the number of base stations a tower would have. The concept has become so significant 

that it has inspired the forming of a new section of the Internet Engineering Task Force 

(IETF) on Mobile Ad hoc Networking. A MANet is useful wherever connectivity is 

temporary and on-demand such as a conference or meeting room, military team, sensor 

telemetry, and disaster or first response teams. 

TECHNOLOGY DESCRIPTION

An ad hoc network is a network that has no fixed infrastructure such as base stations. 

Nodes in the network that are mobile and connected by wireless links are called a mobile 

ad hoc network. [206] They are designed to be quickly and autonomously deployed 

without prior planning or preinstalled infrastructure. Whenever two or more nodes are 

within range of each other, a MANet will spontaneously form providing network 

functionality including voice-over IP, a technique for voice communications over a 

network. These nodes or routers are free to move randomly and organize themselves 

arbitrarily. As a result, the network's topology may change rapidly and unpredictably. 

[132] Multihop communications are used to communicate between nodes in the network. 

Multi-hop means that data from the originating node travels to the “best” nearby node, 

which then passes the data to its best nearby node until this series of hops gets the 

communication to the destination node. Each node acts as a router in cooperation with all 

the other nodes in the network. Because this networking approach is designed to form 

and maintain a network without user intervention or infrastructure, it would operate just 

like a traditional VHF or UHF radio from a firefighter’s point of view. He will not need 

to know or notice that when he speaks into his radio whether the communication reaches 

its destination via multiple hops or relays. 

The important features of a MANet are [302]: 

• Network topologies are dynamic. These nodes or routers are free to move 

randomly and organize themselves arbitrarily. Nodes can join or leave a network 

at any time. As a result, the network's topology may change rapidly and 

unpredictably. 

• The network must be able to function on battery power. The restriction of 

available battery power means that the network requirements and capabilities 

must be designed with energy consumption in mind. 

• Depending on the location of each node/radio the radio propagation conditions 

may be quite different. Thus the bandwidth of the wireless links is not consistent 

across the network. Links may drop and reconnect due to fading and other typical 

mobile communications effects. 
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• The physical security of ad hoc networks is lower than wired networks because of 

the use of wireless links and lack of infrastructure support. 

These characteristics of MANet are what drive the research and product development 

activities for this technology. Important areas for understanding the potential, issues, and 

risks of MANet are routing, security, quality of service, wireless link technology, and 

standardization efforts. 

The requirements imposed on MANet networks can be daunting as they include complex 

coordination and switching protocols, algorithms requiring high computational 

bandwidth, real-time handoff with other network nodes, sophisticated modulation 

technologies, and relatively high-date-rates (as compared with existing single-channel 

voice radios). Historically, communications architectures have tended toward pushing the 

network intelligence into a central hub. Since there are only a few hubs or one hub per 

system, it was cost-effective to have expensive RF components and computational 

elements. MANet-based systems push the networks “intelligence” into the handset. In 

spite of the added complexity, user demands still require small, durable packaged devices 

with long battery life. This remains a technical challenge. 

Routing technology is perhaps the most significant technical challenge for MANet 

systems. [136,137,156,157,270,272,273,274,275,276,277] Routing software development 

is driven by the constraints of link bandwidth, node power consumption, and the dynamic 

nature of the network topology. The protocols under consideration are able to form and 

maintain the network with minimal communications. This conserves link bandwidth for 

other services (voice over IP, for example) and extends battery life by limiting the time 

the node is transmitting. Because of the dynamic nature of the network, typical Internet 

routing protocols are not applicable. Most of the MANet protocols use distance vector 

algorithms, which only send routing tables to near neighbors rather than to everyone on 

the network, as do Internet routing protocols. 

Security becomes a difficult issue in a system such as this, since the nodes are mobile and 

can be connected dynamically in an arbitrary and random manner. A rogue mobile device 

could to wreak havoc in a network where each peer has autonomous capability and 

control. Eavesdropping is also a concern with wireless links. 

Quality of service in a MANet has more constraints than a wired network. These 

additional considerations are constant topology changes, bandwidth limitations, and 

limited memory and processing capabilities of network nodes tasked with routing 

communications. The limited memory and processing that each node has is a particular 

problem because of the dynamic topology. The routing protocols and tables require nodes 

to carry out complex calculations and store significant amounts of data about the routes 

including bandwidth. [271] 

There are several candidate wireless link technologies under consideration for mobile ad 

hoc LANs. These include IEEE 802.11 Wireless LAN, UWB, and HyperLAN/2. 
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Of these 802.11 is the most widely used and is suitable for relatively short distances. It 

provides up to 54 Mbps (802.11a or 802.11g) transmission rate and operates in the 2.4-

GHz band. This standard was not developed with mobility in mind and has some serious 

drawbacks. Studies have shown that it has poor scalability, as the throughput per node 

drops very quickly as the network grows. [307] It also has problems with handovers if the 

mobility of network nodes is high. These may not be problems for typical firefighter 

deployments with handheld radios. 

UWB is being used in some MANet projects. [283] It offers to provide high-date-rates at 

relatively low cost and link performance that is not adversely affected by multipath 

effects. A MANet using UWB signaling would combine the benefits of both 

technologies. The synergy between the excellent in-building propagation characteristics 

and the increased reliability offered by a peer-to-peer routing technology may offer a 

reliable in-building communications system. 

HyperLAN/2 is a standard developed by ETSI intended for wireless LANs. Its properties 

make it suitable for MANet applications. It provides high-speed data, 54 Mbps, efficient 

handovers for supporting mobility, and power-saving support. It also provides reasonable 

security by including authentication and encryption. It is relatively costly. 

Many of the technologies involved in wireless ad hoc networking are either established 

standards or have been submitted in draft form to standards bodies such as the IETF 

MANet Working Group. IEEE 802.11 and HyperLAN/2 are both established standards 

while most of the routing protocols are in draft status. Some areas are nowhere near 

having standards. Security and quality of service are areas with no near-term standards in 

progress. This lack of standards is an impediment to wide spread use of MANet. 

APPLICATIONS

Communications and Networking 

 This technique provides a wireless network approach analogous to the standard RF bidirectional amplifier approach that normally uses leaky feeder or coax and antennas for 

interior RF distribution. 

Although prototypes and demonstration projects exist using MANet approaches, no 

commercial systems suitable for firefighter use were found. Several commercial products 

exist that partially demonstrate MANet capabilities: 

• Vocera Communicator and Cisco IP Phone: These devices provide voice-over IP. 

Neither of these devices uses an ad hoc approach; instead they are implemented 

with infrastructure mode IEEE 802.11b using fixed wireless access points whose 

location must be determined by using standard RF planning techniques. They do 

demonstrate voice over IP on a wireless network. 

• Nokia RoofTop Wireless Router: This device acts as a wireless LAN access point 

for users within range and forms a fixed ad hoc network with other Nokia 
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RoofTop Wireless Routers to allow the network to function around obstructions 

such as buildings. It operates in the 2.4-GHz unlicensed band with a speed of 1–2 

Mbps. 

• Radiant Networks Meshworks: This product also forms a fixed wireless ad hoc 

network and acts as a wireless access router similar to Nokia’s but with data rates 

up to 25 Mbps duplex. 

• Mesh Networks Mesh-Enabled Architecture (MEA): MEA provides mobile 

Internet and geolocation in an ad hoc network. Mesh Networks uses a proprietary 

QDMA modulation for the 2.4-GHz-band radio link. The network supports 

multihop communications and fixed wireless routers. 

The U.S. Army and Marine Corp have deployed operational MANet systems. [302,309] 

The Army operates a system called Tactical Internet, which is a large MANet consisting 

of several thousand nodes. The nodes consist of man-portable and vehicle-mounted 

devices. The Marines have deployed a smaller MANet called in its Extending the Littoral 

Battlefield program. This network uses airborne relay nodes to which land and sea units 

connect using a Lucent WaveLan card that has been modified for longer range. Neither of 

these networks uses IETF MANet protocols and do not appear to support voice-level 

quality of service. Little detailed information is available on these implementations. 

Indoor Geolocation and Tracking 

One concept proposed to the National Institute of Standards and Technology (NIST) uses 

a MANet combined with the capability of UWB links to provide a fully integrated 

multifunction voice, data, and telematics system. This device would provide multiple 

critical functions including in-building location, local detection of colleagues, and 

multinodal communications. [206] The ultimate use of such a system could provide a 

unified fire safety network. The combination of a personnel location system with a GISbased floorplan of the building and fire-spread modeling software could become an 

essential tool in fire suppression operations. While some of these concepts may appear to 

be far fetched, most of the core technology is available in pieces to make a fire safety 

network a reality. 

Another approach proposed is to use “data bags” for MANet routing stations in addition 

to the carried handsets. These data bags are UWB transceivers that can act as relay points 

for the geolocation. In this architecture, the standard UWB transmitter tags carried by the 

firefighters would transmit at a power level in accordance with the existing FCC 

recommendations. This approach becomes feasible because the data bags act as mini-base 

stations inside the building, as opposed to other approaches that involve the use of 

antenna arrays located at points on the outside perimeter of the building. In this case the 

RF-shielding effect of the building can work to keep the radiation inside the structure and 

not to interfere with other communications and GPS used on the outside. In addition, the 

data bag also be used as a “sensor pack” to perform critical readings of temperature and 
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other data useful in suppressing a fire. This approach has the disadvantage of the data bag 

becoming expendable. 

RESEARCH AND PRODUCT STATUS

Mobile networking is an area of active research and product development by a number of 

organizations. NIST, for example, has three laboratories—Information Technology, 

Building and Fire Research, and Manufacturing Engineering—working together on a first 

responder testbed that uses an IEEE 802.11-based MANet to provide robust 

communications and radio location within an office building. [189] Recently, the testbed 

was used to demonstrate the ability of the MANet to accurately determine the location of 

each of the network communicators as well as voice communications. In September 

2002, Information Systems Laboratory (ISL) received SBIR funding to investigate the 

feasibility of a system called the Wireless Firefighter Lifeline to locate, track, and 

monitor firefighters inside of buildings to within 1 meter. [166] In addition to tracking 

firefighters, the proposed system also provides biometric data such as heartbeat and 

respiration as well as external temperature and air bottle level to the fire commanders. 

ISL will show the feasibility of the concept through a combined modeling and 

measurement program. Several other companies are developing applications that fuse a 

MANet with UWB. Among them are Æther Wire & Location, Inc., which is developing a 

networked location system under contract to DARPA, and WPI, which is developing a 

combined location and communications system. [300] Florian Wireless is investigating 

the data bag concept described above.12

Routing protocols are being intensely researched. [136,137,156,157,270,272,273,274, 

275,276,277] The routing algorithm faces unique challenges in a mobile environment. 

The most challenging aspects are the dynamic network topology, lack of centralization, 

potentially large networks both in numbers of radios and in area covered, the wireless 

links, and security considerations. Numerous algorithms have been proposed for 

application in ad hoc networks, each having a unique set of advantages and 

disadvantages. Requirements such as self-starting/self-organizing, scalability to large 

networks, computational complexity, routing reliability, link establishment, switchover 

time, blocking constraints, and queuing constraints are being assessed. Some top 

candidates are: [136,137,156,157] 

• Ad Hoc On-demand Distance Vector 

• Landmark Routing 

• Temporally Ordered Routing Algorithm 

• Dynamic Source Routing 

• Fisheye State Routing Protocol 

• Zone Routing Protocol 

• Optimized Link State Routing 

 

12 This information is based on verbal and email correspondence between Rich Meyers of System Planning 

Corporation and Florian Wireless personnel. 
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Architectural approaches being investigated include full autonomous peer-level routing, 

hybrid configurations using a combination of conventional point-to-point radio and ad 

hoc networking when required, and dynamic master–slave topologies. 

ISSUES

Mobile ad-hoc network routing protocols are designed to run on non-engineered, 

dynamic wireless networks. As a result, there are a number of issues in how to provide 

security and guarantee performance within the bandwidth, battery, processing, and 

memory constraints of mobile nodes communicating over radio links. These have to be 

addressed if MANets are to become commonplace. 

Performance 

Wireless Links: Relatively speaking, wireless links perform poorly compared to their 

wired counterparts. Their limited bandwidth and propagation problems, such as multipath 

fading, have a direct impact on routing and quality of service aspects, specifically 

latency, which is critical for applications such as voice. These links must function within 

the power constraints of the mobile nodes. Robust, low-power wireless links are 

essential. [302,307] 

Routing and Scalability: A routing protocol must maintain security and quality of service 

in a dynamic environment but function within the limits of the link bandwidth (constantly 

changing) and node battery life, processing ability, and memory capacity. As ad hoc 

networks grow beyond a few nodes, this becomes increasing difficult. Current routing 

protocols provide only a fair ability to add nodes (scalability). Networks with poor 

scalability may lose the ability to provide the data bandwidths required for voice, have 

increased latency (delay) affecting the ability to talk over a link, or suffer reduced battery 

life. [135,136] Experimental results show that the throughput per node drops by a factor 

of 10 if the network grows from 2 to 8 nodes. [307] As more nodes join the network, the 

total data bandwidth of the system increases until the maximum that can be supported is 

reached. This increase is because nodes must transmit their own user’s voice and data, 

but also be able to relay signals from other users. Once the maximum is reached the total 

rate remains fairly constant as more nodes join. Because the total data transfer cannot 

exceed the maximum, the data rate per node must drop as more nodes are added. Poor 

scalability can also lead to reduced battery life as complex routing algorithms require 

more complex, high-power consumption processors, Wireless links operating at full rate 

also require more power. Finally, if the routing algorithms are not optimized for voice 

properly, they may cause such delays (latency) that it is difficult to talk. 

Dynamic Location Modeling: In a large building fire, it is likely that one or more nodes 

or group of nodes will be unable to communicate with any other node or group of nodes 

because the node (the firefighter and his radio) are out of range, thereby losing 

communications with radios on the outside of the building. For this reason, it is important 

to understand the dynamics of where these nodes would be located during a fire. In 

addition, this requirement will be key in determining a methodology for the use of fixed 
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routing devices that would be strategically placed by the firefighter. The location 

distribution should be analyzed for several major building types, and this overlaid on a 

propagation model to determine the system-level constraints. [247] 

Security 

The two key security considerations for mobile ad hoc networks are (1) tampering or 

utilization of techniques to intentionally render the system inoperable, and (2) 

eavesdropping and surveillance. Security becomes a difficult issue in a system such as 

this, since the nodes are mobile and can be connected dynamically in an arbitrary and 

random manner. It is possible that an outside mobile device could be able to disrupt a 

network where each member has autonomous capability and control. There are also 

physical security risks compared to static operation networks because portable devices 

may be stolen. 

RECOMMENDATIONS

Research should be undertaken to determine the requirements and deployment guidelines 

for fixed MANet node deployment. 

Firefighter requirements for routing, scalability, and security should be established and 

coordinated through organizations such as PSWAC or Project MESA. 

Channel Coding, Interleaving, and Encryption 

An important aspect of radio communications under impaired conditions is known as 

Forward error correction (FEC) or channel coding. Channel coding uses mathematical 

techniques of digital signal processing to enhance data reliability by applying redundancy 

in a known structure to a sequence of data before its transmission. While FEC is nearly 

always used in conjunction with various complementary modulations schemes (e.g. 

TDMA, CDMA, UWB), it is an independent element in the communication chain. The 

structure used by the FEC allows a receiver to detect (and an increased chance to correct) 

errors. The decoder corrects errors without requesting retransmission of the original 

information as is done in many acknowledgements-based protocols; hence the word 

forward. However, FEC comes at a price. The additional structure or redundancy in the 

data stream results in an increase in the required transmission rate. 

TECHNOLOGY DESCRIPTION

Early advances in channel coding date back to Shannon in 1948 when he first published 

his concept of block coding or algebraic coding. Block coding is one of the simplest 

forms of FEC, where the coder inserts redundant bits in accordance with a specific 

algebraic algorithm. Several years later, convolutional coding was introduced which used 

a similar technique to block coding, but instead operated on the data in a continuous 

fashion instead of discrete blocks. In the late 1960s, Andrew Viterbi developed a coding 
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scheme that bears his name and is now the most prevalent technique in use today. Viterbi 

FEC uses a probabilistic technique of considering memory and determining the most 

likely sequence of bits. Other techniques combine a variety of coding techniques to 

achieve improved performance. For example, while convolutional or Viterbi performs 

well with random errors, other techniques may handle burst errors that are typical in radio 

communication channels. This technique is termed concatenated coding. Another 

technique called Reed-Solomon coding is commonly used behind a Viterbi FEC to form 

a concatenated codec. [333] 

Another technique that is frequently used in conjunction with FEC is interleaving. 

Interleaving is particularly effective in communication channels with burst errors. In 

virtually all digital communication channels, data are transmitted in a formatted frame or 

packet. These frames contain various fields such as an address or header, control words, 

and the actual traffic or payload data. In order for these frames to be properly detected, a 

synchronization method usually uses some predetermined sequence often referred to as a 

unique word. If this sequence is not properly detected, then the entire frame or burst of 

data could be lost. Also, certain protocols are more vulnerable to corruption of the control 

data and other critical fields that may occur when a burst error is encountered. Often a 

burst error in the wrong location of a frame will result in synchronization loss, and the 

receiver may require some time to regain synchronization, in which case a significant 

data loss may occur. [333] 

In addition to the inherent synchronization associated with standard digital data 

transmission, the encryption required for secure communication also poses a challenging 

problem. In many modern encryptions, a “crypto sync” is maintained in the decoders. If 

this crypto sync is lost, it may be seconds before the secure channel is reestablished. 

Interleaver technology mitigates this problem by effectively spreading the data over a 

larger period of time. This has the effect of being able to deal with the correction of 

Gaussian-like errors as opposed to the total data loss associated with burst errors. With 

this technique, a burst error on the radio channel may appear as random errors to the FEC 

algorithm. [333] 

In the early 1990s, a new coding scheme called turbo coding was developed in Europe. 

[334] Turbo coding is the most advanced channel-coding scheme developed, and its 

performance approaches the theoretical limit suggested by Shannon. It is a technique that 

uses a combination of other techniques, with multiple encoders and an internal interleaver 

as an integral part of the coding scheme. The major drawback of turbo coding is that is it 

computationally expensive. As a result, custom hardware was required to use this 

technology in systems, as opposed to Viterbi and other techniques that were readily 

capable of being implemented on the same DSP as the modem functions. This factor 

combined with the establishment of a standard for turbo coding and complex intellectual 

property and licensing issues have slowed the widespread use of turbo coding. However, 

an ever-increasing number of systems are being implemented with turbo coding. [323] 

FEC techniques are critical to improving radio communications. This technology is 

particularly important for radio communications inside buildings as it will allow more 
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reliable links in these structures. In addition, as spectrum utilization becomes more of an 

issue, more advanced coding schemes can maintain channel efficiency. 

APPLICATIONS

These techniques are commonly used in virtually all digital wireless communications. 

These include satellite, microwave, and radio communications. These are also used in 

many data storage systems, and even music CDs, to improve reliability of the storage 

mediums should the data become corrupted. 

RESEARCH

Continuous work is being done in this area to improve turbo coding and other 

interleaving technology. Much effort has been spent on computation reduction and 

practical implementation techniques. New interleaving technology is also being 

developed to work better with higher level protocols, such as IP and ATM. 

ISSUES

The major issue is assurance that the appropriate channel coding is used in the selected 

systems. 

RECOMMENDATIONS

Further understand the operation of various FEC and interleaving schemes as they relate 

to the channel error characterization of transmissions inside buildings. 

Investigate the implication of various coding schemes with other suggested areas such as 

MANets and UWB. 

Power Line Communications 

Power line communications (PLC), also referred to as broadband power line (BPL) uses 

existing power transmission networks to deliver communication services to any device 

plugged into an ac outlet and equipped with a PLC LAN interface. Using the power lines 

for communications is not a new concept. In the 1920s, AT&T was awarded PLC patents. 

In the 1950s, power utilities were using low frequencies (sub 1 kHz) to send control 

messages to equipment on the power grid. By the 1980s, bi-directional communications 

in the 5-to-500-kHz band were being used. Following these narrowband, low-data-rate 

PLC applications, broadband PLC started to develop and today commercialized products 

for LAN applications and Internet access are becoming more widely deployed. [265] 

Firefighter use of PLC has several attractive benefits. It promises to be low cost because 

it uses existing infrastructure that is available in every building. Commercial 

developments in this technology area appear to be growing, and firefighters should derive 

cost benefits from this as well. But perhaps the biggest attraction to this type of 
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communication is the ubiquity of power outlets. Not only are they found in every large 

structure, ac outlets are found in essentially every room, parking garage, and hallway. 

PLC data rates are sufficient for high-speed LAN applications including voice over IP 

and can be interfaced to the Internet. 

TECHNOLOGY DESCRIPTION

Power line communications can be divided into two independent systems, in-house PLC 

and Access PLC. In-house PLC conforms to the HomePlug 1.0 standard for LANs and 

operates on the low-voltage (LV) power lines in buildings. Access PLC, where available, 

can be used instead of DSL or cable for backhaul of HomePlug traffic over the medium 

voltage (MV) transmission lines to the Internet. HomePlug is the only power line 

protocol in use for broadband LANs in homes and offices. On the MV transmission grid, 

however, many different protocols are in use for Access PLC with little effort being 

expended to develop a single standard. 

Access PLC, currently in field trials with several power utilities, provides 45-Mbps rates 

over the MV power grid plus the low-voltage lines between the transformer and the 

electric meters of the premises connected to the transformer. The MV distribution 

network extends from the power distribution substation to the stepdown transformer. 

Some Access PLC systems have signaling that can pass through the transformer while 

others use a bypass technique. Typically, the bypass is accomplished by wireless or fiber 

optic connection as the utilities will not allow the LV lines any potential electrical 

connection to the MV grid for safety reasons. An Access PLC base unit is used to 

connect the Internet to the medium voltage line using inductive coupling rather than a 

direct connection. [248] 

The LV power lines extend from the stepdown transformer into the home or office. 

Several protocols are used for low-voltage PLC. Most of the protocols such as X–10, 

CEBus, and LonWorks are meant for home and office automation and security 

applications and are not sufficient for high-data-rate applications. HomePlug technology 

is meant for high-speed LAN applications with current technology built to the HomePlug 

1.0 standard [294] supporting data rates up to 14 Mbps, which is more than adequate for 

voice. HomePlug 1.0 data rates are compared with other broadband LAN types in Table 

9. HomePlug is able to coexist on the same power lines with the other standards because 

it uses a different frequency band. 

TABLE 9: NETWORK DATA RATE COMPARISON

Network Type Data Rate (Mbps) 

Ethernet/IEEE 802.3 10/100 

IEEE 802.11a 55 

HomePlug 1.0 14 

IEEE 802.11b 11 

HomePNA 2.0 10 

Source: [294] 
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HomePlug LAN Internet access is accomplished by having a gateway via cable, DSL, 

wireless, or router. An alternative is to use a PLC modem to couple the HomePlug LAN 

to the Access PLC backhaul network. The modem is connected to the HomePlug LAN 

inside of the meter, and is connected to the electric line outside of the meter. By emerging 

standards, there is a frequency separation between Access and in-house: Access is to use 

the RF frequency space below about 10 MHz, while HomePlug should use the RF 

frequency space from 10 to 20 MHz. 

Within a given HomePlug LAN, the network is self-configuring. The protocol supports 

devices joining or leaving the network at any time. If you plug in another module 

(ordinary node or gateway), then the network need only know how to address the node 

within the address space of the HomePlug LAN. A unique address must be set using a 

computer on the LAN or manually prior to inserting the device into an ac outlet. The 

addresses available on the network need to be known so as not use an address already in 

existence. If the address is not set manually, but by means of a computer, then the 

computer would need the information of the address space in the HomePlug LAN. The 

protocol included priority access with the intention of supporting high-date-rate and lowlatency applications such as voice and video. The standard calls for the range to be up to 

1,000 feet with throughputs as high as 14 Mbps. Real-world throughput is slower as 

shown in Table 10. 

TABLE 10: EXAMPLE REAL-WORLD POWERLINE DATA THROUGHPUT

Powerline 

Transmitter Receiver 

Distance 

Between 

Transmitter and 

Receiver (ft) 

WSFTP 

Throughput 

(Mbps) 

TTCP 

Throughput 

(Mbps) 

Laptop 

(Dining Room) 

Laptop 2 

(Dining Room) ~2 4.2 5.2 

Laptop 1 

(Den) 

Laptop 2 

(Dining Room) ~23 4.5 5.3 

Laptop 2 

(Office) 

Laptop 1 

(Kitchen) ~35 4.0 4.5 

Laptop 1 

(Kitchen) 

Laptop 2 

(Office) ~35 3.1 3.1 

Laptop 1 

(Children’s 

Room) 

Laptop 2 

(Office) ~70 1.9 1.8 

Laptop 2 

(Office) 

Laptop 1 

(Children’s 

Room) 

~70 4.1 3.9 

Laptop 1 

(Swimming Pool) 

Laptop 2 

(Office) ~60 2.0 1.6 

Laptop 2 

(Office) 

Laptop 1 

(Swimming 

Pool) 

~60 2.4 2.8 

Source: [294]
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APPLICATIONS

This technique could be used analogously to the standard RF bi-directional amplifier 

approach that normally uses leaky feeder or coax and antennas for interior RF 

distribution. 

Communications and Networking 

A variety of HomePlug devices are widely available in retail stores for setting up LANs 

in homes and offices. Siemens, for example, sells devices that provide interfaces to the 

power line including: 

• Wireless access point (IEEE802.11b) interface to HomePlug. Siemens sells this 

device to extend the range of a wireless network — an application very similar to 

what firefighters would like to do, extend the range of their hand-held radios. 

• Wireless router to HomePlug. 

• Wired router to HomePlug. 

These devices and the HomePlug standard are designed to make setup easy for the 

average consumer. According to product literature, it is possible to merely connect the 

devices to an ac outlet and have a working network; Siemens ships all its HomePlug 

products with the same default key for its built-in 56-bit DES encryption. These units are 

inexpensive with prices for devices in the $100 range. Access PLC is still in the field trial 

stage, and prospects for commercial success of this technology remain uncertain. 

The use of HomePlug LANs alone or in conjunction with Access PLC in homes and 

offices offers some possible applications for firefighters, including “intelligent buildings” 

and voice and video applications. A HomePlug LAN-equipped intelligent building has 

the potential to connect every electrical device to the LAN and in conjunction with 

Access PLC or alternatives in the same manner as DSL or cable modems connect to the 

Internet. This would allow firefighters to monitor HomePlug sensors (fire, smoke, and 

seismic could be developed) in buildings for fire location and progress and building 

stability before and after entering a burning structure. This ability could aid in developing 

firefighting plans and enhancing the safety of firefighters. It would even be possible to 

integrate this sensor data with fire prediction tools such as the Fire Dynamics Simulator 

and Smokeview visual tool under development by NIST. Even if firefighters did not have 

access to the intelligent building HomePlug LAN over the internet it may be possible to 

develop a first responder interface to a building’s HomePlug LAN (or LANs) that 

firefighters could connect to when arriving at the fire scene. 

A HomePlug LAN can also carry voice communications using voice over IP. In this 

application, the power lines could serve as range extenders for a new generation of radios 

such as the IEEE 802.11 mobile ad hoc network radios being demonstrated by NIST on 

its first responder test bed [189]. As firefighters enter a building, they would plug 

HomePlug to radio interface devices such as Siemens WAP/HomePlug into ac outlets as 

required to give radio coverage local to the HomePlug device. The HomePlug devices 
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autonomously establish a network as long as they have been preset to use the same DES 

encryption key. When a firefighter communicates, his voice would be carried in multiple 

hops either directly to the outside of the structure or if necessary to the WAP/HomePlug 

interface then over the ac power lines to other WAP/HomePlug devices in range of the 

fire personnel outside of the building. [217,250] Firefighters would also need a radio 

device to enable firefighters using 802.11 radios to communicate with personnel using 

the traditional UHF and VHF radios outside the building. Motorola’s ACU–1000 is a 

product that provides a similar type of interoperability for currently deployed radio 

systems that cannot interface directly. [2] 

Another less likely option would be to inductively couple an Access PLC network base 

unit on the stepdown transformer side of the building’s electrical meters. This approach 

has drawbacks. No devices such as those available for HomePlug are being developed, as 

this standard is intended as Internet backhaul rather than LAN applications. There are no 

standards for Access PLC, and two Access PLC networks cannot coexist, so firefighters 

could not set up their own network if one already existed. [248] Access PLC can coexist 

with HomePlug as each resides in a different frequency band. If Access PLC is used for 

Internet access, a conditioning unit will be installed in front of the electric meter. This 

unit has two outputs. The first output is the electrical line for the building, which passes 

through a low-pass filter to filter the Access PLC signal from the electrical lines entering 

the house. The second is the output for the PCL modem, which passes through a highpass filter to allow only the high-frequency PLC signaling to the PLC modem. 

RESEARCH AND PRODUCT STATUS

The HomePlug 1.0 standard is fully developed and devices built to this standard are 

widely available in retail stores. These products provide every conceivable type of 

network functionality likely to be needed in a LAN. 

The next-generation standard (HomePlug AV) will produce data rates above 100 Mbps to 

support high-definition television (HDTV) and standard-definition television (SDTV). 

The HomePlug AV standard release is expected in late 2004 or early 2005. 

Access PLC has reached the field trial stage. [248] Some of the companies involved in 

field trials of proprietary protocols are Ambient, Amperion, Current Technologies, and 

Main.net. A typical example of the many trials is one testing Ambient Corporation’s PLC 

solution operating in Santiago since March 2002. This trial, in which a group of 

volunteers has broadband Internet access and voice over IP service, is in a high-standard 

commercial neighborhood in Santiago. This trial uses the power distribution grid 

operated by Chilectra, an electric utility for broadband Internet access. Internet access 

data transmission rates reach up to symmetric up/down 10 Mbps to the customer premise. 

ISSUES

PLC has both technical and regulatory issues both for commercial applications and for 

firefighter applications. 
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Technical 

Using an Access PLC Network: Only one Access PLC network can exist on a power line 

at a time, but several Access PLC protocols are being tested with no sign of a movement 

to standardize. Firefighters will not know which, if any, Access PLC standard is in use or 

which buildings or parts of dwellings have PLC modems installed. Further, no devices 

are developing applications such as interfacing wireless to power line. 

Coexisting With or Joining a HomePlug: It needs to be confirmed that firefighterinstalled HomePlug devices will operate as needed. 

Setup and Use of a Firefighter PLC Network: It is not clear that the setup and operation 

of a PLC or PLC and wireless hybrid network, HomePlug or Access, can be made fast 

and straightforward enough for firefighters to accomplish in the limited time available to 

them on scene. A procedure would need to be established so firefighters know where to 

install HomePlug devices to relay voice over the power lines. An interface from the 

IEEE802.11 network to the firefighter’s UHF and VHF radios would need to be 

developed to allow the new radios to communicate with the older systems in use. 

Reliability: A test in 500 homes showed that 80 percent of outlet pairs supported more 

than 5 Mbps, and 98 percent were able to support more than 1 Mbps. [294] No testing 

was found in the literature search for real-world performance in structures other than 

homes. Two issues arise here: whether these results meet firefighter requirements and if 

these results hold true in wider testing, including office buildings and multidwelling 

units. 

Security: At least in concept, a technique could be developed to let firefighters access a 

building’s PLC network, but this could create security issues for the everyday users of 

these networks. 

Range: It is unclear whether the real-world range and data bandwidth are sufficient for 

application to structures other than homes. A related concern is the range between 

devices installed on separate low-voltage ac lines connected to separate electrical meters. 

The meters may provide some low-pass filtering and attenuate the signaling. 

Regulatory 

Although the FCC is strongly supporting finding competing technologies (facilities-based 

competition) that provide communications services to homes and offices via a “third 

wire,” opposition exists to Access PLC implementation. Access PLC uses the HF 

spectrum and has the potential to interfere with amateur radio, AM radio, military 

communications, radio astronomy, and distress frequencies. [265] The American 

Amateur Radio League is fighting Access PLC because of their concern that widespread 

implementation of Access PLC will interfere with the HF band and prevent reliable HF 

communications. [257] There is also some concern about interfering with differential 

GPS networks. [261] 
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RECOMMENDATIONS

A detailed study should be undertaken to determine the feasibility of using the HomePlug 

standard as an in-building repeater approach in large structures including those with 

electrical service via multiple electrical meters. Research is needed to determine what 

modifications are necessary to make HomePlug devices suitable for fire service 

communications and to determine if the distribution of ac outlets that work on the 

network is satisfactory. 

Access PLC should be given a very low priority for use in firefighter applications due to 

the numerous uncertainties. 

RF Distribution in Buildings Using Heating and Ventilation Ducts 

Work has been done evaluating the feasibility of a technique for in-building RF 

distribution that uses heating, ventilation, and air conditioner (HVAC) ducts as 

waveguides. [164] 

TECHNOLOGY DESCRIPTION

HVAC ducts in several configurations were used as waveguides for RF distribution. 

Depending on the frequency, good results were obtained with HVAC ducts and showed 

significantly lower losses than both direct propagation and leaky feeder cable techniques. 

Because an existing infrastructure is used, this approach has the potential to be low cost. 

APPLICATIONS

This technique could be used analogously to the standard RF bi-directional amplifier 

approach that normally uses leaky feeder or coax and antennas for interior RF 

distribution. 

One scenario for deploying an HVAC RF distribution system involves coupling RF into 

the ducts at a central point in the duct system. This could be near the central air handler in 

a typical HVAC installation. The coax to waveguide couplers, similar to those now used 

to couple to conventional waveguide, would be inserted into the duct. The RF would 

propagate via the duct, splitting at each branch or tee, which acts as waveguide power 

dividers. If RF obstructions are in the duct, the signal would be coupled around and 

special louvers would be installed in each room to radiate the signal. If the area to be 

covered was shielded from the duct then couplers could be used to feed a passive 

reradiator. Table 11 gives the duct sizes required for various bands. 
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TABLE 11: HVAC DUCT SIZE REQUIREMENTS TO SUPPORT COMMON WIRELESS BANDS

Band 

Lowest 

Frequency 

(MHz) 

Minimum 

Duct Width 

(rectangular) 

(cm) 

Minimum 

Duct Radius 

(circular) 

(cm) 

Cellular 824 18.20 10.70 

ISM 902 16.60 9.75 

PCS 1805 8.10 4.75 

ISM 2400 6.25 3.66 

U-NII 5150 2.91 1.71 

Source: [164] 

RESEARCH

Although providing in-building coverage for RF communications is an area of intense 

study, this technique is not being widely investigated, no buildings have been built or 

retrofitted to use this approach, and no commercial products are available. This is not a 

technique that can be adopted by firefighters prior to commercial companies using it as it 

requires the HVAC system to be specially built. If it were adopted in the future by 

companies providing commercial communications services (cellular, trunking, and PCS) 

it may be advantageous for firefighters to have equipment and the training to enable them 

to communicate via the building’s built-in system. 

ISSUES

Considerable research would be needed to go beyond the current technical feasibility 

study stage. Also, the business case for this type of application has not been put forth 

beyond the researchers feeling that using or reusing parts of existing infrastructures 

(HVAC ducts, etc.) should compare favorably with installation of leaky feeder and other 

current methods on in-building RF distribution. 

Areas for further study include: [164] 

• The waveguide characteristics of most HVAC ducts lead to multimode 

propagation. Added to this will be the effects of reflections from end caps, bends 

and junctions leading to delay spread. Delay spread and coherence bandwidth in 

this environment have not yet been developed. 

• Efficient couplers for getting RF signals into and out of HVAC ducts have not 

been developed. 

• Ducts are not manufactured as precision waveguides. Because of this, mode 

conversion from the dominant duct waveguide mode to orthogonally polarized 

modes is likely to occur at joints and other imperfections leading to signal loss. 

• Viable methods of controlling and determining power splitting at branches and 

tees to allow proper system design do not exist. 

• Current implementations of air dampers and fins in HVAC systems are likely to 

block RF signals propagating in the duct. New methods and materials that will 
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allow RF propagation while performing the necessary air handling have not been 

determined. 

• Many HVAC systems contain RF obstructions such as fans and coils. Methods for 

coupling around these obstructions have not been investigated. 

RECOMMENDATIONS

Further work should be supported to determine if an approach to providing BDA-type 

functionality is feasible. This work should include a study of the distribution of ductwork 

types in structures as well as research that addresses identified issues. Carnegie Mellon 

University has performed some of this research, but this area needs to be more fully 

explored. 

Alternative Frequency Bands 

It may be feasible to take advantage of the propagation characteristics of frequency bands 

outside of the normal VHF and UHF bands used in firefighter communications. The VLF 

and MF bands both provide improved propagation through earth (and by extension, 

building materials). The MF frequencies have been shown to efficiently couple to and 

propagate in mine tunnels over phone lines, ac lines, or even rails used for haulage 

vehicles to provide underground communications over distances of several thousand feet. 

TECHNOLOGY DESCRIPTION

Very Low Frequency Communications 

The VLF band is very narrow, only 27 kHz, and currently allocated for uses such as radio 

navigation. Radio waves in segments of this band can propagate long distances by the 

surface wave phenomenon, and the band is able to penetrate better into the ground than 

higher frequencies. [311] Voice communications in the VLF band would require the use 

of digital compression because of the limited bandwidth. 

Medium Frequency Communications 

The MF band is from 300 kHz to 3 MHz. This band currently includes AM radio (535 to 

1605 kHz or almost half of the band), radio navigation, and various others. Maritime and 

mobile distress, safety, and calling channels for public safety are allocated several 

hundred kHz in this band. MF signals are useful in that they can propagate over fairly 

substantial distances (e.g., two mobile units could easily talk to one another with tens of 

miles of separation). MF signals can propagate through solid material, even several 

hundred meters of rock under the proper conditions, do not attenuate as rapidly as higher 

frequencies when propagating around corners, and can propagate in conductive materials 

in the tunnels such as telephone and power lines. A widely available commercial 

application of MF is RF communications on power lines where it is used for LANs and 
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marketed under the HomePlug name. The HomePlug application was discussed in the 

“Power Line Communications” section. 

The U.S. Bureau of Mines and others [17,18,19,20,21,22,23,24] have studied MF 

propagation in mines in the United States, Canada, Australia, the United Kingdom, New 

Zealand, China, and South Africa. [115] These studies were able to measure and analyze 

the various RF propagation modes found in mines. The studies found that complex 

interactions occurred between MF radio waves and the environment as determined by the 

natural geology (rock composition, water content, etc.) and the man-made features 

(tunnel cross section, presence of conductors such as ac power lines, etc.). Of most 

interest to this report was the finding that when conductors, such as phone or power lines, 

were present propagation in the conductors (two or more conductors are required) 

completely dominates other underground propagation modes. [288] The studies found 

that, in effect, the existing conductors in the facility act as the antenna and transmission 

line for the communications system. 

Mining organizations and related government organizations have also conducted field 

trials of systems using inductive coupling of MF waves into and reradiating from existing 

conductors such as phone lines and ac power lines to provide communications between a 

base unit and mobiles in underground mines over distances exceeding 4,700 meters 

without repeaters. [204] In these installations, it was found that the attenuation rate in the 

conductor was 1 dB/1,000 feet at 100 kHz and 3 dB/1,000 feet at 300 kHz; at 450 MHz, 

the rate was 21 dB/1,000 feet of leaky feeder cable. [115] Others have developed 

propagation models for frequencies from MF to UHF based on extensive measurements 

done in many underground mines. [115,213] These low-loss propagation modes exist in 

circular and rectangular air-filled tunnels with containing conductors (ac power and 

telephone lines and rail tracks). The attenuation is dependent on the distance between the 

conductors and the tunnel rock wall. [211] 

The various MF communication installations used a number of approaches to antenna 

design. The designers had to make the antennas man-portable for the mobile radios. For 

the base station, the antennas could be larger as long as they fit within the tunnel 

dimensions. In either case, the antennas were much smaller than design rules would 

dictate for this frequency. Typically, antennas have dimensions on the order of one-half 

the signal wavelength, which for a 100 KHz signal would be 1500 meters, and obviously 

not practical. The man-portable radio typically used a loop antenna carried over the 

shoulder similar to a bandoleer [116,175] or integrated into a vest. [204] In one case 

[127] the base units used loop antennas that were 6 feet by 24 feet mounted along the 

tunnel wall, and in others used a single-line coupler placed around a bundle of phone 

lines similar to a current probe [204]. The portable antenna and both base station 

configurations performed well. 

APPLICATIONS

Most products and research using VLF and MF frequencies are aimed at underground 

mining operations. 
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Very Low Frequency 

VLF products have been introduced and are used as through-the-earth (TTE) emergency 

evacuation paging systems in place of stench gas [115,179]. Examples are Mine Site 

Technologies’ PED system and MRS’ FlexAlert system. [180] Both systems use large 

loop antennas to transmit to man-portable LF receivers. The man-portable systems 

typically build a VLF receiver and antenna into a miner’s vest. These types of emergency 

paging systems may be of use to firefighters, especially in structures where typical VHF 

or UHF radios provide inadequate coverage. 

Transtek has tested, but not commercially deployed, a VLF TTE communications system 

that allows two-way, real-time, voice communications. No published information is 

available on this system. 

Medium Frequency 

For communication applications, the predominant use of the MF is in underground mines, 

although in the 1970s fire departments in England used large MF loop antennas 

surrounding tall buildings to communicate with firefighters within the building. [115] 

The mine communication applications made use of propagation via the conductor 

transmission lines in tunnels and direct wireless radio-to-radio communications. A typical 

setup had a base station that provided an interface to the telephone system used at the 

mine and an MF loop antenna or line coupler. The telephone system provided 

communications with the outside world while the loop antenna provided communications 

with the underground areas of the mine. The loop antenna was hung on the tunnel wall 

where it parasitically coupled with the conductors (telephone, ac power, rail tracks) 

running through the mine. If the line coupler approach was used, it was clamped around a 

bundle of conductors, frequently telephone lines. Portable transceivers were mounted in 

vehicles or fitted into vests worn by miners. Loop antennas for the portable units were 

worn bandolier fashion. Repeaters were installed in the mine. These units coupled to the 

conductor transmission lines carrying the MF communications signal. If a miner wanted 

to talk to another miner, the communications was direct; communication was wireless to 

the other miner’s radio if he was local. If the other miner was out of direct wireless range, 

the repeater coupled the miner’s transmission onto the conductor and a repeater near the 

other miner retransmitted it. Miners could receive transmission from base unit via the 

conductor without a repeater as long as they were within 2 or 3 miles of the base unit and 

were standing within about 2 meters of the conductors. [211] They could also talk back to 

the base station over the same conditions. 

RESEARCH AND PRODUCT STATUS

There appears to be very little current research or development in the area of MF 

communications. Australia’s Commonwealth Scientific and Industrial Research 

Organisation has some activity in this area but generally it is a mix of public and private 

funding and information dissemination is limited. [17,18,19,21,22] 
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ISSUES

Mine Communications Applicability to Above-Ground Structures 

The research and trials in this area have been done in underground mines where MF 

waves propagate in either of two modes: using conductor pairs in tunnels as transmission 

lines for long distance communications or via direct, wireless radio-to-radio 

communications for shorter range communications. [288] The conductor-pair 

transmission line propagation uses the tunnel as part of the transmission media; this type 

of propagation may not occur in structures. To determine the practicality of direct, totally 

wireless radio-to-radio and power-line-coupled MF to radio, a measurement program 

needs to be designed and implemented that tests performance over a range of structure 

configurations. 

Frequency Allocations 

There are frequencies in the MF band for maritime and mobile distress channels for 

public safety use but not for MF structure communications. Also, there are potential 

interference problems between this and Access PLC or HomePlug networks. 

Commercial Development 

Based on the literature search, it appears little research or product development is 

ongoing in this area even for underground mining. This may make development time and 

cost prohibitive. 

RECOMMENDATIONS

A study should be undertaken to determine the system design and effectiveness of a VLF 

or MF emergency evacuation paging system for firefighter application in structures. 

Mine research used a conductor-in-tunnel waveguide. The applicability of this situation 

to structures should be investigated with empirical measurements in a range of structures 

and variety of conductors (power line, telephone, with and without direct coupling to 

conductors). All types of construction should be investigated, ranging from older 

buildings with predominantly load-bearing masonry walls to modern structures. 

Man-portable and vehicular-mounted antenna development should be supported 

particularly as it addresses firefighting requirements. 

Frequency allocation issues should be studied to determine the likelihood that this type of 

application would be approved. 
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Electronic Status and Firefighter Location 

Firefighter status boards that require firefighters to manually check in and out are in use 

today. These systems, however, are prone to human error and can result in placing a 

firefighter’s safety at risk when not used properly. Recently, systems have been tested 

that automatically track firefighter status to address the difficulties faced by incident 

commanders in tracking personnel on the fireground. 

TECHNOLOGY DESCRIPTION

One system, the Motorola Fireground Accountability System [185], uses the wireless 

signals from each firefighter radio to automatically identify firefighters by sector or 

working assignment. Each radio channel corresponds to an incident command sector, and 

identification information is automatically shown on the incident commander's laptop. 

This reduces the manual approach to status tracking, although the system still has to be 

set up to assign radio channels to sector and enter firefighter identification information. 

Improvements to the system are planned. An evacuation tone triggered by the incident 

commander that wirelessly transmits an evacuation signal to firefighter radios will be 

available. Also, to be added is the capability to poll firefighter radios to identify radios 

that are out of coverage range. The time elapsed since the radio was in coverage will be 

logged. [154] 

ISSUES

Although the system tracks radios to determine if they are out of coverage range and logs 

the elapsed time, it does not tell the incident commander the location of the firefighter. 

RECOMMENDATIONS

Any automated personnel monitoring systems should be integrated with a radio location 

system to provide 3D location of either the firefighter’s radio or an RF tag worn by the 

firefighter. 

Radio location setup and operational requirements should be developed to make the 

location system operable by firefighters. 

Bi-directional Amplifiers 

Bi-directional amplifiers (BDAs) are a technically straightforward technique for 

providing improved coverage in areas that are shadowed from RF communications. 

Unfortunately, there are cost/economic barriers to implementation. 

TECHNOLOGY DESCRIPTION

BDAs are used to boost an exterior signal reradiated in the interior of a structure or tunnel 

and boost the signal from the interior to the exterior. A typical installation uses an 
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exterior antenna called a donor antenna to receive the RF communications signal from 

the exterior source (e.g., a public safety trunking system and transmit signal from the 

interior to the same trunking system). Attached to the donor antenna is a signal boosting 

unit, the BDA. This device uses one frequency band for the talk in channel and a second 

for the talk out channel. Attached to the BDA is a network of cables for distributing the 

signal throughout the structure. The network can be leaky feeder cable that radiates the 

RF signal along its entire length or can be standard coaxial transmission line that has 

antennas and hybrid couplers attached where needed to provide the desired coverage. 

Proper functioning of a BDA system requires a significant amount of RF engineering 

design prior to installation and a significant amount of test and rework time after the 

system is installed. BDAs will not work with simplex radios. 

APPLICATIONS

Many companies provide the components (antennas, cable, etc.) and the engineering 

services needed to install BDA-type systems. 

ISSUES

While technically straightforward to implement, a bi-directional amplifier system is 

expensive to install. It requires the installation of an exterior donor antenna, a bidirectional amplifier unit, and multiple interior antennas and hybrid couplers fed by long 

lengths of coaxial transmission line or, alternatively, the use of leaky feeder cable run 

throughout the building. This is expensive to install in new buildings and even more 

expensive to retrofit to existing buildings. Commercial cellular and trunk radio operators 

see no economic incentive for the installation of such a system except in very limited 

cases where they are guaranteed an income stream for a sufficient time. Systems that 

have been installed are not likely to have been designed with firefighter requirements in 

mind and may not provide the coverage desired or the redundancy needed to provide 

satisfactory operation while sustaining damage during a fire. One answer to this is to 

force installation by building code requirements. This has met with resistance from local 

governments who do not want to put disincentives to businesses into the building code. 

RECOMMENDATIONS

Work with multiple local governments to establish regional adoption of building codes 

requiring installation of BDA systems in new high-rise buildings. The system 

requirements should address fail-safe features necessary to provide reliable 

communications even while sustaining fire damage. 

Investigate alternative implementations of the BDA concept such as power line 

communications, medium frequency coupling to conductors, or use of modified HVAC 

ducts. 
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Smart Antennas 

New-generation smart antennas may provide improved communications if integrated into 

firefighter repeaters, inside or outside a structure. 

Smart antennas have been in limited use for commercial CDMA cellular and other 

wireless applications for several years. These smart antennas are installed at the base 

stations where technical personnel manually program the combining circuitry phase and 

gain adjustments to produce the desired antenna gain, beam-width, and direction to 

reduce interference. In a CDMA network, reducing interference increases capacity. In 

general, the antennas are not automatically adaptable to changes in the RF environment 

or adapted too slowly to react to fast changes. Antenna setup requires an understanding of 

RF propagation, and in-building coverage improvement is not addressed. The antennas 

also are not portable and are expensive. 

TECHNOLOGY DESCRIPTION

A smart antenna consists of a set of antenna elements called an array connected to a 

combining circuit that adapts to the RF environment. The combining circuit adjusts the 

phase and gain of the each elements’ signal and then sums the signals together. This 

signal is fed to the receiver. Recently, product plans have been announced that are 

directed at the wireless LAN market. These developments promise significant benefits for 

wireless LANs: 

• Significant increase in wireless link range 

• Increased network data throughput 

• Reduced power consumption 

• Higher reception reliability 

In contrast to the smart antennas used in cellular base stations, these antennas are small 

and low cost enough to be integrated into home and office wireless access points. They 

have the ability to scan for signals coming from other wireless access points and mobile 

nodes and quickly adapt the smart antenna to point in the direction necessary to optimize 

the wireless link between the smart-antenna-equipped wireless access point and the 

mobile node or other wireless access point. The antenna pattern can be optimized to 

counter the effects of noise, interference, and multipath. [313] These antennas have 

multiple, independent antenna beams so they can produce multiple optimized antenna 

patterns to accommodate multiple wireless links simultaneously. 

Another type of smart antenna is called a MIMO, or multiple input, multiple output, 

system. In a MIMO implementation, both the transmitting and the receiving radio use 

antenna arrays. These systems have demonstrated the potential for very high capacities. If 

the number of antennas is the same at the transmitter and the receiver, the link capacity 

increases linearly with the number of antennas. [340] These types of antennas have been 

tested for hand-held radios as well. [339] In this case, because of the proximity of the 
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antenna array elements, pattern and polarization diversity was used in the MIMO 

processing. 

APPLICATIONS

The inclusion of smart antenna technology in portable repeaters and wireless access 

points could bring important benefits to firefighters. This technology, combined with a 

MANet for firefighters or with conventional UHF or VHF portable radios, would provide 

improved range in or out of buildings. Firefighters could set up a smart-antenna-equipped 

repeater on the building’s exterior and it would cover more of the interior. If the situation 

demanded, they could carry additional repeaters into the building that could communicate 

with the exterior repeater and the firefighter mobiles. One of the functions that could be 

designed into a smart antenna would be the ability to help the firefighter automatically 

locate a site for the repeater. It may be possible to design the smart-antenna-equipped 

repeater to guide firefighters in placing them for the best results. Because the smart 

antenna scans antenna beams to automatically optimize the wireless links to devices 

within its range, a firefighter could carry one into a building and by watching a simple 

display know if the signal strength back to the outside repeater is in the optimum range. 

Also, if firefighters deployed smart wireless access points through a building, they could 

use the same feature to know when they have reached the optimum distance from the last 

repeater. 

Several companies have announced products in development. Lumera Corporation has 

demonstrated an antenna design using a patch array technology to form multibeam 

patterns. The company says the antenna, measuring about 3 inches on a side and 1/4 inch 

height, can support low-power applications such as IEEE 802.11 LANs, as well as 

applications that require up to 10 watts. [321] A second company, Airgo Networks Inc., 

is developing a cost-effective smart antenna based on an OFDM three-antenna, four-chip 

design. Airgo claims it can double the throughput and quadruple the range of 802.11 

wireless LANs. [322] 

RESEARCH AND PRODUCT STATUS

This is an area of active research and product development. Several companies have 

announced products, but these still seem to be some time away from actual product 

deployment. Also, Project MESA has identified smart antennas as an area of interest for 

enhancing public safety communications. 

In general, the performance enhancements offered by the use of smart antennas in 

multihop ad hoc networks can be significant. Issues still remain due to the added 

complexity that smart antennas add to the protocols. [313] 

ISSUES

The effectiveness of smart antennas is closely linked to media access control (MAC) 

protocols. Various MAC protocols have been explored for use with smart antennas. The 

optimum antenna pattern is not obvious due to MAC protocol complexity in conjunction 
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with the functionality of multihop ad hoc networks. Until this is resolved, smart antennas 

may be of limited use. 

RECOMMENDATIONS

Smart antennas improve wireless LAN performance including mitigating multipath and 

should be considered for incorporation into both traditional repeaters and wireless 

access points for a firefighter-deployed MANet. 

Research is needed to develop protocols that optimize smart antenna performance in 

smart antenna applications. The MIMO architecture holds particular promise. 

Training for the use of smart antennas or simplification of the setup procedures should be 

pursued if smart antennas are to be easily used. 

Development of requirements for firefighter applications via an organization like Project 

MESA should be considered. 

Spread Spectrum 

The use of spread spectrum modulation techniques can provide significant multipath 

mitigation and result in improved communications within structures. [218,219] 

TECHNOLOGY DESCRIPTION

The two main types of spread spectrum modulations are frequency hopping and direct 

sequence. A third type is a hybrid of both. 

Direct sequence systems use a high-rate code sequence, along with the information being 

transmitted, to modulate their RF carrier. The high-speed sequence is used directly to 

modulate the carrier, setting the transmitted RF bandwidth. Binary code sequences from 

11 bits to 289–1 bits have been employed, at code rates up to several hundred megabits 

per second. CDMA cellular systems used in the United States are an example of a direct 

sequence spread spectrum system. 

A frequency hopping system covers a wideband frequency spectrum by hopping from 

frequency to frequency over a wide band. The sequence of frequencies occupied is 

determined by a code sequence, and the rate of hopping is a function of the information 

rate. 

Advantages of spread spectrum include: 

• Multipath mitigation 

• Rejection of narrowband interference. 

• Multipath access: number of users can access a common channel for 

communication. 
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• Random access: users can start their transmission at any arbitrary time. 

• Privacy due to unknown pseudo random codes: The applied codes are, in 

principle, unknown to a hostile user. This means that it is difficult to detect and 

monitor the message of another user. 

APPLICATIONS

The literature search found one non-UWB spread spectrum product intended for 

firefighter use, a frequency hopping two-way emergency pager called T PASS 3 

Evacuate. [197] This device is an NFPA compliant two-way PASS device that operates in 

the unlicensed band from 90–928 MHz. It can individually address up to 1,100 

firefighters or can page all at once. It has a companion repeater to provide extended range 

when necessary. In one field trial, two of the repeaters were required to provide coverage 

in a 75-story high rise. The pager is in use in the Las Vegas and Houston fire 

departments. 

ISSUES

Even though spread spectrum signals are immune to most narrow band interfering signals 

they can be interfered with under the right circumstances. When the interferer is strong 

enough to overcome the processing gain from signal spreading, a narrow band 

interference suppression algorithm is needed. An example of this type of interference was 

interference caused by old analog cell phones to newer CDMA cell phone base stations. 

RECOMMENDATIONS

New firefighter communications systems procurements should incorporate multipath 

mitigation as a basic requirement. Use of spread spectrum techniques with the ability to 

withstand narrow band interference is a key component in mitigating multipath. 

Other Technologies 

COMMERCIAL WIRELESS NETWORKS

Use of commercial cellular (800 MHz and 1900 MHz) radios were discussed at the 

preliminary project meeting and rated a low priority for inclusion in this report for the 

following reasons: 

• Propagation in structures similar to or worse than existing firefighter UHF radios. 

• Cellular network availability is not likely in emergencies either due to overuse or 

the system being down because of emergency. 

PROJECT 25 

Project 25, a joint effort of U.S. federal, state, and local government, is the approved 

narrowband interoperability voice and data standard for use in the 700 MHz band for 
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public safety wireless communications. Project 25 radios were discussed at the 

preliminary project meeting and rated a very low priority for inclusion in this report for 

the following reasons: 

• Project 25 standard radios share the same propagation limitations as other UHF 

radios. 

• Project 25 is intended to address other issues such as interoperability and security 

rather than improving in-building communications. 

BLUETOOTH

Bluetooth, a technology that is generally used to wirelessly connect devices, was also 

discussed at the preliminary project meeting and rated a low priority for inclusion in this 

report for the following reasons: 

• Range limited to about 10 m. 

• Data rate approximately 1 Mbps. 

• Intended for short-range use to replace cables. 

The literature search did not find anything to cause the priority of this technology to be 

raised as no applicable research or products were found relevant to this report’s focus on 

firefighter communications in structures. 

General Recommendations 

The following recommendations are given in addition to the detailed recommendations 

by technology area given above. They are generally applicable to the problem of 

firefighter communications in structures. 

The first set of general recommendations address critical deficiencies in the knowledge 

base of the propagation characteristics of radio waves in structures. The literature search 

revealed that while propagation studies have been performed on specific frequencies 

there has been no comprehensive study of propagation characteristics for the full 

frequency range of interest to fire and emergency communications. Nor is there a 

complete understanding of the effects of building materials on these propagation 

characteristics. This latter topic is one that should be ongoing as new materials and 

building techniques, especially those used in high-rise construction, are continually 

evolving. 

RF measurements by NIST [78,79] should be extended to cover from VLF to 10.6 GHz. 

Investigation of frequency dependency of the material dielectric and conductivity 

constants over these frequencies should also be funded. 

An RF propagation survey in structures from VLF to at least 10.6 GHz (upper end of 

band allowed for UWB) should be pursued. 
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The next set of recommendations address deficiencies that affect the determination of 

system specifications for structure communications. For example, 100 percent in-building 

communications coverage is not a realistically achievable goal; 30 percent coverage may 

currently be achieved and is insufficient. These guidelines and requirements need to be 

detailed so that system developers are aware of the acceptable performance parameters. 

Moreover, consideration must be given on how to merge new technology communication 

systems with existing fire department communication systems. 

Requirements should be developed for the minimum level of coverage necessary for inbuilding communications. This is a basic requirement and is independent of the 

communications technology. 

Guidelines for repeater placement for a variety of structures and fire scenarios should be 

developed. 

New technology communications systems should be interoperable, to some degree, with 

legacy systems. 

Current communications technology is a dynamic and evolving field. It is important that 

the technological community and communication system developers understand the 

needs of the fire service. Conversely, it is important the fire services understand the 

possibilities and the limitations of the technologies available. New systems will be more 

complex than the fire service has worked with in the past. Both the fire service and 

manufacturers will need to address the interface between user and developer. 

Establish and fund an organization to facilitate dialog between emergency responders 

and the technical and regulatory groups. 

Public workshops to address firefighter communications issues found in structures should 

be held on a routine basis. 

A newsletter, electronic bulletin board, web page, or other information sharing means 

should be developed specific to firefighter communications issues. 
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Summary of Recommendations 

Table 12 summarizes all of the detailed recommendations noted throughout this chapter. 

The recommendations are grouped by technology area. 

TABLE 12: SUMMARY OF RECOMMENDATIONS

Technology Area Recommendation Page 

The public safety community should develop a position in 

regards to supporting UWB deployment and the minimum 

requirements needed for each firefighter application. If the 

fire community’s position is to support this technology, 

then minimum requirements should be developed for 

firefighter applications. An organization, such as PSWAC, 

NFPA, or Project MESA should be used to make the 

community’s position known to the spectrum-regulating 

organizations. 

50 

The public safety community, using an organization such 

as PSWAC, NFPA, or Project MESA, should support 

antenna research and provide input on firefighter-specific 

antenna requirements. 

50 

The public safety community, using an organization such 

as PSWAC, NFPA, or Project MESA, should support 

research and design of advanced receiver architectures 

such as the Rake receiver. 

50 

Ultra Wideband 

Research into electromagnetic susceptibility and 

compatibility should be supported through organizations 

such as PSWAC, NFPA, or Project MESA. Ideally, power 

and frequency restrictions will be lessened to make UWB 

more widely applicable for public safety applications. 

50 

Research should be undertaken to determine the 

requirements and deployment guidelines for fixed MANet 

node deployment. 

57 

Mobile Area 

Networks Firefighter requirements for routing, scalability, and 

security should be established and coordinated through 

organizations such as PSWAC or Project MESA. 

57 

Further understand the operation of various FEC and 

interleaving schemes as they relate to the channel error 

characterization of transmissions inside buildings. 

Channel Coding, 59 

Interleaving, and 

Encryption Investigate the implication of various coding schemes with 

other suggested areas such as MANets and UWB. 59 

A detailed study should be undertaken to determine the 

feasibility of using the HomePlug standard as an inbuilding repeater approach in large structures including 

those with electrical service via multiple electrical meters. 

Research is needed to determine what modifications are 

necessary to make HomePlug devices suitable for fire 

service communications and to determine if the 

distribution of ac outlets that work on the network is 

satisfactory. 

65 Power Line 

Communications 

Access PLC should be given a very low priority for use in 

firefighter applications due to the numerous uncertainties. 65 
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Technology Area Recommendation Page 

RF Distribution in 

Buildings Using 

Heating and 

Ventilation Ducts 

Further work should be supported to determine if an 

approach to providing BDA-type functionality is feasible. 

This work should include a study of the distribution of 

ductwork types in structures as well as research that 

addresses identified issues. Carnegie Mellon University 

has performed some of this research, but this area needs 

to be more fully explored. 

67 

A study should be undertaken to determine the system 

design and effectiveness of a VLF or MF emergency 

evacuation paging system for firefighter application in 

structures. 

70 

Mine research used a conductor-in-tunnel waveguide. 

The applicability of this situation to structures should be 

investigated with empirical measurements in a range of 

structures and variety of conductors (power line, 

telephone, with and without direct coupling to conductors). 

All types of construction should be investigated, ranging 

from older buildings with predominantly load-bearing 

masonry walls to modern structures. 

70 

Man-portable and vehicular-mounted antenna 

development should be supported particularly as it 

addresses firefighting requirements. 

70 

Alternative 

Frequency Bands 

Frequency allocation issues should be studied to 

determine the likelihood that this type of application would 

be approved. 

70 

Any automated personnel monitoring systems should be 

integrated with a radio location system to provide 3D 

location of either the firefighter’s radio or an RF tag worn 

by the firefighter. 

71 

Electronic Status and 

Firefighter Location Radio location setup and operational requirements should 

be developed to make the location system operable by 

firefighters. 

71 

Work with multiple local governments to establish regional 

adoption of building codes requiring installation of BDA 

systems in new high-rise buildings. The system 

requirements should address fail-safe features necessary 

to provide reliable communications even while sustaining 

fire damage. 

72 

Bi-directional 

Amplifiers 

Investigate alternative implementations of the BDA 

concept such as power line communications, medium 

frequency coupling to conductors, or use of modified 

HVAC ducts. 

72 
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Technology Area Recommendation Page 

Smart antennas improve wireless LAN performance 

including mitigating multipath and should be considered 

for incorporation into both traditional repeaters and 

wireless access points for a firefighter-deployed MANet. 

75 

Research is needed to develop protocols that optimize 

smart antenna performance in smart antenna 

applications. The MIMO architecture holds particular 

promise. 

75 

Training for the use of smart antennas or simplification of 

the setup procedures should be pursued if smart 

antennas are to be easily used. 

75 

Smart Antennas 

Development of requirements for firefighter applications 

via an organization like Project MESA should be 

considered. 

75 

Spread Spectrum 

New firefighter communications systems procurements 

should incorporate multipath mitigation as a basic 

requirement. Use of spread spectrum techniques with the 

ability to withstand narrow band interference is a key 

component in mitigating multipath. 

76 

RF measurements by NIST [78,79] should be extended to 

cover from VLF to 10.6 GHz. Investigation of frequency 

dependency of the material dielectric and conductivity 

constants over these frequencies should also be funded. 

77 

An RF propagation survey in structures from VLF to at 

least 10.6 GHz (upper end of band allowed for UWB) 

should be pursued. 

77 

Requirements should be developed for the minimum level 

of coverage necessary for in-building communications. 

This is a basic requirement and is independent of the 

communications technology. 

78 

Guidelines for repeater placement for a variety of 

structures and fire scenarios should be developed. 78 

New technology communications systems should be 

interoperable, to some degree, with legacy systems. 78 

Establish and fund an organization to facilitate dialog 

between emergency responders and the technical and 

regulatory groups. 

78 

Public workshops to address firefighter communications 

issues found in structures should be held on a routine 

basis. 

78 

General 

Recommendations 

A newsletter, electronic bulletin board, web page, or other 

information sharing means should be developed specific 

to firefighter communications issues. 

78 
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APPENDIX A: PRIORITIZED PROJECT ISSUES 

Ranking Area Topic 

10 

Accountability (Integrating 

Personal Accountability 

Systems (PAS) with 

Communications) 

• Integrating PAS with communications • Electronic accountability • Automatic vehicle location • Electronic command boards 

10 Communication Planning and Coordination • Through building (into/out of) • Underground 

• In building 

10 Grants • Small business grants – who and what (if information available) 10 

Monitoring Firefighter 

Welfare and Location OnScene 

• Role/responsibility of dispatchers. • Use of field communications units and communications coordinato• Remote monitoring • Vital signs • Location 

10 Reliability Issues 

• Line-of-sight limitations • Underground (subways, parking garages) • Confined space rescue • Communication into and out of buildings (especially high-rises) • Intermittence • Communication coverage/dead spots 

10 Reliability Issues – Interference • Communicating into buildings • Radio propagation through fire, heat and smoke 10 Unsuitable Equipment • Frequency band unsuitable for structure/ground penetration 
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Ranking Area Topic 

2 Reliability Issues 

• Equipment Failure • Mechanical/technical issues (unstable equipment, radio malfunctio• Concerns about reliability of 800-MHz digital systems • Failure observability • Field testing prior to implementation • Radios introduced into fire stations without field testing • Interference • Atmospheric • Electronic • Built environment (tunnels, high-rise buildings, shipboard) • Jamming (terrorism) • Reliability of 800 MHZ digital technology/reliability of Motorola XTS • Repeater performance/repeater infrastructure • Environmental (hills, foliage, mountainous terrain, distance) 

• Acknowledgement of message 

2 Unsuitable Equipment • Most equipment adapted from other uses • Unable to communicate from inside using full personal protective e1 Communication Planning and Coordination 

• Coordination of ground-to-ground and air-to-ground communication• Lack of integrated communication planning (frequency coordination• Failure to use ICS correctly or at all 

• Inadequate ability to receive, disseminate, and analyze information • No backup data – command post destroyed as in World Trade Cen• Vehicle/unit tracking – geo-location • Intra- and interagency communications 

1 No Equipment • Some firefighters lack radios 
NIOSH Firefighter Radio Communications 

TriData Corporation 84 

Ranking Area Topic 

Not Investigated Ergonomics 

• Human factors receiving little attention • Develop additional skill sets • Stress-tempered communication skills • Survival simulator (similar to airline pilot virtual reality simulator) • Radio discipline • Cultural factors • Unwillingness to call for help • Inadequate training and personnel performance • Performance issues on complex multi-channel/multi-mode radio sy• New systems must be learnable/focus on learn-ability • Unfamiliarity with the use of new radio equipment • Ability to deploy and manage new technology • Resistance to new technology • Difficulty communicating while wearing SCBA • Current adaptations (speech ports, face piece integrated micropho

portable radio interfaces, throat mikes, bone mikes, etc) receive mixed 
NIOSH Firefighter Radio Communications 

TriData Corporation 85 

Ranking Area Topic 

Not Investigated Inadequate System Capacity 

• During complex, multi-alarm incidents with many operating units at• Number of frequencies available vs. number of people attempting t• Legal process to acquire • Lack of repeaters/repeating infrastructure • Opportunities to test and deploy portable, mobile, air-based and sta• Portable radios needed for all firefighters • Should be considered a critical item of personal protective equipme• Every firefighter (or two-person team) working in a hostile environm

portable radio with emergency distress feature 

• Radio spectrum deficiencies • Work at federal level to secure enough radio spectrum • Radio spectrum interoperability for public safety • Department of Defense report re. progress on 138-144-MHz band 

• Commercial applications (e.g., Nextel) • Cell phones • System capacity • ACU1000 – mixer – multiple frequencies patched (IC only use) 

Not Investigated Unsuitable Equipment 

• Firefighters must use SCBA and communicate effectively • Needed: a better portable radio specifically designed for the structu

environment 

• Physically robust system • Waterproof • Ruggedized/shock resistant • Able to withstand high heat environment • Designed to be easily operable with heavy gloves in a hostile envir• Observability of LCD displays in low light conditions • Concerns over triggering radio controlled bombs and terrorist devic• Black box recorder • Battery life, interchangeability 
NIOSH Firefighter Radio Communications 

TriData Corporation 86 September 2003 

APPENDIX B: FIRE DEPARTMENT COMMUNICATIONS – 

EXPERIENCES FROM THE FIELD 

The information contained in this appendix was gathered from a variety of sources. Much 

of the information comes from fire department management studies previously 

undertaken by TriData Corporation. Some information comes from individual fire 

department annual reports, websites, or other fire department literature. Wherever 

possible, the information from these studies was verified with the fire department to 

ensure that the most current data was reflected in this report. 

TABLE 1: EXPERIENCES FROM THE FIELD – DEPARTMENT OVERVIEW

Jurisdiction 

Resident 

Population 13

Land 

Area1

(sq. mi)

Land 

Area 

Protected

Fire 

Department 

Type 

Uniformed 

Employees 

Communications 

System 

Austin, TX 656,562 252 Urban Career 979 UHF (450 MHz) 

Bellingham, WA 67,171 32 Urban/ 

Suburban Career 140 VHF 

Boston, MA 589,141 48 Urban Career 1,600 UHF (483-MHz 

Conventional) 

Boulder, CO Rural 

Fire Department 18,000 25 Suburban/ Rural Combination 8 FTE; 35 Volunteer 

VHF 

(153–155-MHz) 

Brighton, CO 20,905 17 Suburban/ 

Rural Combination 9 FTE; 60 Volunteers 

UHF (400/800 MHz 

Trunked) 

Charlotte, NC 540,828 242 Urban Career 890 UHF (800 MHz 

Trunked) 

Chicago, IL 2,896,016 227 Urban Career 4,000 VHF (Conventional) 

Clark County, NV 1,375,675 8,000 Urban/ 

Rural Combination 1,300 Career; 400 Volunteer14 UHF (800 MHz 

Trunked) 

Dallas, TX 1,188,580 385 Urban Career 1,700 UHF (400 MHz) 

Detroit, MI 951,270 139 Urban Career 1,296 UHF (400 MHz) 

Everett, WA 91,488 48 Urban/ 

Suburban Career 158 VHF 

Fairfax County, VA 969,749 395 Urban/ 

Suburban Combination 1,166 UHF (460/800 MHz Trunked)) 

Gettysburg, OH 3,700 60 Rural Volunteer 50 Volunteers VHF (154-MHz) 

Los Angeles, CA 3,694,820 469 Urban Career 3,200 UHF (800 MHz 

Conventional) 

Milwaukee, WI 596,974 96 Urban Career 1,100 UHF (400 MHz) 

Phoenix, AZ 1,321,045 475 Urban Career 1,366 UHF (Conventional) 

Pittsburgh, PA 334,563 56 Urban Career 896 UHF 

Portland, OR 529,121 134 Urban Career 680 UHF (800 MHz) 

San Antonio, TX 1,144,646 412 Urban Career 1,018 UHF (800 MHz 

Trunked) 

San Diego, CA 1,223,400 324 Urban Career 1,100 UHF (800 MHz) 

 

13 Data from U.S. Census 2000 was used for consistency and comparison. Data may not agree with that 

reported by the jurisdiction. 

14 Many fire departments that operate within Clark County, NV including but not limited to Las Vegas, 

North Las Vegas, Henderson, and the Clark County Fire Departments. These numbers are estimates, based 

on information gathered from department websites. 
NIOSH Firefighter Radio Communications Appendix B 

TriData Corporation 87 September 2003 

Jurisdiction 

Resident 

Population 13

Land 

Area1

(sq. mi)

Land 

Area 

Protected

Fire 

Department 

Type 

Uniformed 

Employees 

Communications 

System 

San Francisco, CA 776,773 49 Urban Career 1,700 UHF (800 MHz) 

Schaumburg, IL 75,386 19 Suburban Career 138 UHF (800 MHz) 

Springfield, NJ 14,429 5 Suburban Combination 33 Career and 

Volunteer UHF (470 MHz) 

Wichita, KS 344,284 136 Urban Career 371 UHF (800 MHz 

Trunked) 

Austin, TX 

The all-career Austin Fire Department (AFD) serves a population of 663,000. Its nearly 

1,000 uniformed firefighters operate out of 39 fire stations strategically located 

throughout the department’s 234-square-mile response area. That area includes portions 

of two neighboring counties (Travis and Williamson) as well as Austin-Bergstrom 

International Airport.15 

Located in the Central Texas hill country, Austin is approximately 230 miles from 

Mexico and less than 200 miles from Dallas, Houston, and San Antonio. It is also the 

State Capital of Texas. 

Its downtown area has high-rise buildings (8 – 10 of which are over 20 stories), belowgrade structures such as tunnels (Capitol building), basements, and underground parking 

garages, and diverse terrain—all of which pose communication challenges. Austin is also 

home to many computer chip manufacturing plants. 

For the past 15 years, radio communications have been spread over six radio channels on 

the 450 UHF band. One channel is designated for dispatch, while the other five are 

devoted to tactical operations. Channels are assigned geographically, and each channel 

has a repeater. 

Communication problems are sometimes encountered by the fire department. Some are 

technical issues related to various structures (e.g., high-rise buildings, tunnels, concrete 

buildings, etc.) and others are related more to interoperability – where communications 

with other city departments or neighboring jurisdictions Is sometimes compromised. 

Overcapacity and training are not issues, as the department conducts training programs 

and employs standard operating procedures (SOPs). 

To remedy the interoperability problem, the Austin‘s public safety agencies are 

upgrading to an 800-MHz trunked system. Reconfiguration to the 800 MHz is expected 

to solve the interoperability problem. The improvement in interference may be achieved 

through a modified system design and infrastructure and should improve other 

interference caused within structures, as well. 

 

15 Austin Fire Department Fact Sheet (www.ci.austin.tx.us/fire/fdfacts.htm.). Data may not agree with that 

reported by the U.S Census 2000. 
NIOSH Firefighter Radio Communications Appendix B 

TriData Corporation 88 September 2003 

Bellingham, WA 

The Bellingham Fire Department (BFD) provides fire suppression as well as emergency 

medical services. Bellingham, Washington, is located in Whatcom County, which is the 

last county on the Washington coastline bordering British Columbia. Bellingham’s fulltime, career firefighters serve a population of approximately 78,000.16 This includes 

citizens of Bellingham and some fire protection districts in unincorporated Whatcom 

County. 

Bellingham is 90 miles north of Seattle and 50 miles south of Vancouver. To the east are 

the Cascade Mountains, and to the west is Puget Sound. The area covered by the BFD has 

a diverse topography with extremely mountainous areas to the east, and wide lowland 

floodplains near the marine shoreline. The BFD is the primary provider of emergency 

ambulance service throughout the county, and frequently responds to areas deep within 

the county where radio coverage is limited. 

Currently, the BFD uses a VHF radio system with relatively good coverage of their 

response area. However, the department reports various “dead spots” within the city 

where firefighters cannot communicate with dispatch or with one another. There is one 

particularly troublesome spot—a large mall in the City where firefighters cannot 

communicate using their portable radios and where pagers will not activate. For all 

incidents above a second alarm, the BFD uses mutual aid companies from nearby 

jurisdictions. All of these companies are dispatched by the same communications center, 

which facilitates communications prior to and during incidents. 

Like many departments, the BFD reports that communications from below grade are 

intermittent. In addition, communications with the Police Department are difficult, due to 

the lack of interoperability between the two agencies’ radio systems. 

With such close proximity to the Canadian border, there is a limit on the strength of the 

radio signals the BFD can use. A recent communications study for Whatcom County 

recommended transitioning all emergency service providers in the county to an 800 MHz 

system; the BFD is working with the county to identify possible sites for radio towers and 

repeaters. . In the interim, they are exploring the possibility of installing a repeater near 

the mall to improve communications in that part of the City. The Department also uses 

Nextel cellular phones. However, after an earthquake several years ago, they discovered 

that the radio system functioned, but the Nextel phones did not. 

In addition, BFD personnel reported difficulty using portable radios while wearing PPE 

(personal protection equipment), particularly gloves. To address this problem during 

emergency incidents, all BFD radios are programmed so that the first and last positions 

on the frequency dial are the same and are a channel that is always monitored by 

dispatch. With this scheme, if a firefighter becomes trapped or disoriented, etc., and 

 

16 The population served differs from the resident population as report by the U.S. Census 2000 because the 

Bellingham Fire Department protects citizens in parts of unincorporated Whatcom County. 
NIOSH Firefighter Radio Communications Appendix B 

TriData Corporation 89 September 2003 

cannot communicate with units on the scene, he can always communicate with the 

dispatch center. 

Boston, MA 

The Boston Fire Department (BFD) is one of the oldest career fire departments in the 

United States. Its 1,600 firefighters serve in 35 stations, protecting 575,000 people spread 

over 47 square miles.17

The fire department operates a conventional UHF 483 conventional system. One channel 

is dedicated to dispatch and four channels are for fire operations (all with repeaters). Each 

channel operates in duplex mode. There are 20 satellite receivers strategically placed 

throughout the city to support communications. The system has additional capabilities for 

use in tunnels and underground areas; special receivers and transmitters are dedicated to 

subterranean communications. 

Imperfections within the system design has led the department to upgrade or replace 

some of its communication system equipment – base stations, receivers, etc. Essentially 

the department now has a new infrastructure. 

Prior to the upgrade, BFD was plagued with unwanted signals out of the system. Like 

other cities, Boston experiences dead spots in high-rise buildings and basement or subbasement areas, as well as in some residential structures. The hilly terrain tends to cause 

dead spots in residential areas. To combat this problem, the BFD uses transmitter 

steering, which moves communications from one transmitter to another. 

Communications in underground structures also presents a problem. For more than a 

decade, the City of Boston has been undergoing major transportation changes. The plan is 

to eliminate the Central Artery, an elevated six-lane highway that runs through the center 

of downtown, with an underground expressway directly beneath the existing road. This 

project is known as “The Big Dig.” This new tunnel will present considerable challenges 

to the public safety departments of Boston, including the fire department. 

The walls of the tunnel create a man-made barrier to radio frequency signals that carry 

radio communications. In 1995, when the construction the Ted Williams Tunnel, which 

extends from Logan Airport to the Greater Boston area, was complete, the City 

implemented a state-of-the-art communication device (i.e. leaky cable) that could operate 

31 channels simultaneously. The city installed a leaky cable running along the roof of the 

tunnel. A leaky cable is a “by-product of conventional coaxial cable with small slits cut 

through its layers that allow RF signal to seep out in amounts strong enough to cover 

small areas of square footage.” [296] 

Many new buildings in Boston have bi-directional amplifiers incorporated within their 

structures. Bi-directional amplifiers, commonly known as BDAs, are used for 

 

17 Boston Fire Department Overview (www.cityofboston.gov/bfd/overview/overview.htm.). Data does not 

agree with U.S. Census residential population data. 
NIOSH Firefighter Radio Communications Appendix B 

TriData Corporation 90 September 2003 

improving/correcting portable radio communications to, from, and within (large) 

structures. These BDAs provide the fire department the ability to operate all four fire 

department channels within a building. 

Interoperability is another serious issue in Boston. Boston is part of a metro fire district 

that includes 34 other cities and towns. The district lacks a system for direct 

communication with all of the other departments. When a major incident occurs, a BFD 

chief, acting as the incident commander, will be collocated with an incident commander 

from another department. 

Boulder, CO Rural Fire Department 

Boulder Rural Fire Department is located to the north of the City of Boulder in 

unincorporated Boulder County, Colorado. It protects a population of approximately 

18,000, spread over 25 square miles. The region is suburban and rural, and includes 

mountains, heavily forested areas, as well as some light industrial areas. 

The Boulder Rural Fire Department is a combination department, with volunteer and 

career personnel. There are eight full-time paid staff and more than 35 volunteers who 

work out of two fire stations. 

The department operates on a VHF 153–155-MHz radio system. It is suitable to the local 

geography and terrain as its signals readily bend around obstacles. Each firefighter in the 

department carries a voice pager. Portable radios are located on each seat of the fire 

apparatus ensuring that each person staffing apparatus (e.g., fire engine) has a portable 

radio. 

The area is a mixture of mountains, valleys, and flat terrain. In the mountains, 

communications are sometimes limited, and in some cases, blocked out entirely. 

Both the shadowing of the mountains and limited numbers of repeaters often lead to these 

communication problems. Yet, the fire department reports that these pockets of limited 

radio communications are small enough to not cause serious problems. Most large ranges 

of dead spots are restricted to unpopulated areas. 

Where communications are problematic, the department uses “human repeaters.” That is, 

each portable radio carried by a firefighter rebroadcasts or radiates the signal. Mobile 

repeaters are never used. 

Another issue for the Boulder Rural Fire Department is interoperability. All of the 

surrounding counties use the 800 MHz radio systems. Therefore, firefighters from the 

Boulder Rural Fire Department are not capable of communicating directly with other 

firefighters working on an incident. 
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TriData Corporation 91 September 2003 

Brighton, CO 

Brighton, Colorado is located approximately 20 miles northeast of Denver. The 

combination Greater Brighton Fire Protection District (GBFPD) has nine career and 60 

volunteer uniformed personnel. The district is adjacent to Denver International Airport 

(DIA) and encompasses approximately 160 square miles of mostly rural Adams and 

Weld Counties, with a total population of 25,000.18

Recently, the GBFPD migrated from a 400 MHz radio system to an 800-MHz trunked 

system. However, due to the large number of volunteer personnel who rely on pagers, the 

District continues to simulcast its dispatch information on the 400-MHz band to activate 

those pagers. Nextel is gaining popularity in the region, particularly as more tower sites 

are added. 

The GBFPD is currently working out some coverage issues with the 800 MHz system. 

Additional radio towers have reduced the number of “dead spots,” but communications 

into and out of schools in the district remain a problem.. For interior operations, the 

district generally uses simplex mode, rather than the trunked system, to enhance 

communications. 

Interoperability in the region is also a struggle, as the high cost of 800MHz has deterred 

many city agencies and surrounding jurisdictions from adopting it. Several departments 

continue to use 400 MHz, while nearby Weld County remains on its 100 MHz system. 

Finally, the emergency activation feature of the radios is not enabled; the district is in the 

process of developing procedures for emergency radio communications, e.g., Mayday 

situations. 

Charlotte, NC 

The City of Charlotte, N.C. is home to over 500,000 people who live within the 242 

square miles of urban land area. It is surrounded by rolling hills. 

According to the Charlotte Convention and Visitors Bureau, nearly 300 Fortune 500 

companies have offices in Charlotte, as do 340 foreign firms.19 The downtown includes 

high-rise buildings and other large structures (e.g., convention center, football stadium, 

etc.). There are no underground tunnels or subway systems. 

The all-career Charlotte Fire Department provides services throughout the City of 

Charlotte and Mecklenburg County. It protects a population of over 600,000 and covers 

270 square miles. There are 890 uniformed personnel in the department. 

 

18 The City of Brighton has a resident population of 20,905. The remaining population served by the 

GBFPD is from Adams and Weld Counties. 

19 Charlotte Convention and Visitors Bureau (www.charlottecvb.org/visitor.cfm.) 
NIOSH Firefighter Radio Communications Appendix B 

TriData Corporation 92 September 2003 

For the past 14 years, the fire department has used an 800-MHz trunked system. The 

entire city government of over 11,000 people is on the network. The fire department 

operates on 28 channels, shared with the police department. Each firefighter has a 

portable radio. 

Like many fire departments around the nation, Charlotte reports problems with 

transmitting signals outside of a high-rise building or basement structure. It is testing a 

mobile repeater to alleviate this problem. To date, it has had some success with the 

mobile repeater. For interior operations, the department uses simplex mode – radio to 

radio – to communicate to, from, and within a building or structure. The mobile repeater 

has added robustness to the core of the structure, allowing better communications among 

firefighters on the simplex mode. Without the mobile repeater, the portable radios do not 

have the strength to reach the stationary repeaters. 

Interoperability between outlying counties is another problem. As a solution, the city has 

provided neighboring jurisdictions with Charlotte radios. 

The Charlotte Fire Department does not have overcapacity troubles. The department has 

standard operating procedures designed to shut down various parts of the system (i.e., 

private line on the radio, interconnect system, etc.) to ensure no overcapacity. 

Lastly, a proposal to improve fire communications in high-rise buildings by requiring a 

built-in communications infrastructure was defeated. 

Chicago, IL 

The Chicago Fire Department is one of the premier firefighting organizations in the 

world. It is one of the largest in the United States with nearly 4,000 uniformed personnel, 

protecting 3 million citizens over nearly 240 square miles. In addition, the department 

provides fire suppression services to one of the world’s busiest airports – O’Hare 

International. 

Communications are provided to the Chicago Fire Department by a separate department, 

the Office of Emergency Communications (OEC), otherwise known as the “9-1-1 

Center.” 

Chicago uses a conventional VHF system with two dispatch channels, one reaches 

citywide. Three simplex channels are used for fire operations and one command channel. 

Company officers all carry portable radios, and the department is in the process of issuing 

more – one radio for every two persons. 

As a whole, the Chicago Fire Department reports that it experiences few communication 

problems because it deploys a multi-simulcast radio system and 10 transmitter sites (per 

channel). The system has diversity: up to 32 receivers are within any 12 square miles 

area. Unlike many urban departments, Chicago has no plans to change its communication 

system to 800 MHz. Because of number of receivers around the city, communications 

with dispatch via portable radios functions well. 
NIOSH Firefighter Radio Communications Appendix B 

TriData Corporation 93 September 2003 

One challenge the department has is the inability of the fire department to talk directly 

with law enforcement and emergency medical services (EMS), which they operate on a 

different radio system (UHF). EMS and the fire department respond jointly on most 

incidents, so the fire department does have some access to the UHF system. A more 

permanent solution to this problem is being worked on, which will use technology to 

patch the systems together. The department deploys a command vehicle to every major 

incident. These vehicles have a suite of radios installed for communications by the 

incident commander with the various departments (e.g., fire, EMS, police, etc.). 

Considering the large number of high-rise buildings, the Chicago Fire Department is 

advocating built-in infrastructure within the structures. Currently, most in -building 

coverage is achieved with portable, simplex radios. There are occasional “dead spots” 

within some high-rise structures, basements, etc. These are considered “incident specific 

problems,” not system-wide. 

Subway communications are accomplished on a UHF frequency (same as law 

enforcement and EMS). As a result, the fire department cannot use its radios to 

communicate within the subways with the necessary authorities. In such instances, 

department personnel use EMS radios. 

Clark County, NV 

Clark County is located in southern Nevada. On a regional level it has a population of 

more than 1.5 million residents spanning an area of 8,000 square miles. Most of the 

population lives within the Las Vegas valley. Some of its incorporated areas are Las 

Vegas, North Las Vegas, and Henderson. The county includes both urban and rural areas. 

The Southern Nevada Area Communications Council, also known as SNACC, manages 

most fire department communications, including those for the City’s of Las Vegas, North 

Las Vegas, and Henderson and unincorporated Clark County. SNACC was created as a 

Joint Powers Authority by each of these jurisdictions. Each municipality buys into the 

system and pays annual operating costs. The communications network managed by 

SNACC covers approximately 4,000 square miles. 

Each department operates on an 800-MHz trunked radio system. There are a total of 20 

channels, with mobile radios are located in each piece of fire apparatus. Portable radios 

are located on each seat of the fire apparatus ensuring staffing personnel a means of 

communication. 

Despite its desert environment, Clark County has high mountains that make 

communications difficult. The tallest mountain is 12,000 feet. There are some others that 

reach heights of 9,000 feet. 

Casinos and other high-rise buildings present challenges. There are many in-building 

coverage issues. The size and construction of the buildings can shield RF signals, and, the 

Casinos are often very noisy (a combination of lots of people and slot machines), making 

it difficult for firefighters to hear radio communications. Interference from the Casino’s 
NIOSH Firefighter Radio Communications Appendix B 

TriData Corporation 94 September 2003 

own communication systems can disturb the fire department radio system. Lastly, each 

casino has at least one below ground level, in the basement. 

To manage the communication problems, SNACC and the local fire department 

sometimes post a firefighter in the security office of a casino to use both the fire 

department radio communications and the built-in communications system of the casino. 

Many of the casinos and other large buildings are wired with radio accessories, such bidirectional amplifiers. SNACC and the participating fire departments recently purchased 

mobile repeaters. They have not been tested. 

Like many other areas around the country, Clark County is experiencing interference 

with wireless communications towers, most notably Nextel. The county is awaiting final 

approval between the Federal Communication Commission and Nextel on a plan that 

addresses interference to public safety communications in the 800-MHz band. This plan 

is known as the Joint Commentors’ Consensus Plan. 

The goal is to eliminate interference to public safety communications on the 800-MHz 

band; to cause minimum disruption to existing services; and to provide sufficient 

spectrum for public safety users. It divides the 800-MHz band into two separate blocks of 

channels. The first is intended for public safety. The other block of channels would be 

used for Nextel and its wireless communications. 

Dallas, TX 

Dallas is one of the largest cities in the Southwest, and the seventh largest in the U.S. It is 

a major business and financial center, and also one of the top convention cities in the 

United States.20 It has numerous tall buildings, (with 25 buildings greater than 30 stories). 

The elevation of the city is between 450-750 feet, and there are many below ground 

structures, such as basements, sub-basements, and parking garages. 

Dallas Fire-Rescue (DFR) covers 378 square miles and a resident population of 

approximately 1.2 million. The department operates out of 55 fire stations, and currently 

has nearly 1,700 uniformed firefighters. 

DFR operates on a 400MHz UHF radio system. Each firefighter has a portable radio. 

There are four simplex channels for operations. The simplex channels are limited by 

distance. Interior fire operations sometimes create a communications problem. To 

communicate outside a structure, DFR sometimes has to relay the message via a runner 

through an egress stairwell. . 

Police and fire can communicate with each other, through a “patch system.” Dispatch 

will patch police and fire together, and they can talk directly to one another. 

 

20 The Dallas Convention and Visitors Bureau (www.dallascvb.com/visotrs/today.php.) 
NIOSH Firefighter Radio Communications Appendix B 

TriData Corporation 95 September 2003 

The department has done some investigative research and considered upgrading to an 800 

MHz radio system. However, the upgrade has not been pursued due to a lack of funding, 

and also because the department concluded that the 800 MHz radio system did not meet 

the needs of the city for 95 percent coverage. 

Detroit, MI 

Detroit has a residential population of over 950,000 across 139 square miles. The Detroit 

Fire Department (DFD) protects the city’s population with nearly 1,300 career 

firefighters. 

DFD uses a 400 MHz radio system, which has been in place for nearly 30 years. The 

Department is responsible for fire as well as EMS dispatching. Currently, DFD has one 

repeated channel for dispatch, four fire operations channels, and one channel for EMS. 

Some tactical fire operations channels are also repeated. 

Commanding officers for each fire company have portable radios. Personnel at or above 

the rank of Battalion Chief are also issued cell phones and pagers. 

Most communications problems are concentrated in the downtown area due to the high 

number of high-rise buildings, such as office buildings, apartment buildings, and other 

large structures. The Department has added repeaters to buildings and other areas of the 

City to alleviate these problems. Nonetheless, they still occur. There was an incident 

reported in which a firefighter used his cell phone to contact the command post outside. 

Firefighters also report equipment problems, notably that the portable radios are not 

waterproof. Also, they report that down tower sites and broken repeaters have hampered 

communications. 

The department is upgrading to an 800 MHz system at the end of 2003 to be able to 

communicate with all city departments (such as police, etc.). Some firefighters are 

opposed to the upgrade, as they fear that the new radio system will not work as well in 

sub-basements and other structures. 

Everett, WA 

The Everett, Washington Fire Department (EFD) is a full-time, career fire department 

that protects roughly 90,000 residents. Although the City boundaries encompass 41 

square miles, only 28 square miles are land, the other 14 are water. Everett is home to the 

USS Abraham Lincoln Aircraft Carrier Group, as well as other marine vessels. Everett’s 

coverage area includes a Boeing aircraft assembly plant, which is the largest enclosed 

structure in the world. Numerous warehouses and high-rise buildings complement the 

array of single-family homes throughout the city. 

The terrain includes hills throughout the City limits, with the northwest part of the city, 

along the waterfront, sitting considerably below the rest of the city. Everett is 80 miles 

south of the Canadian border. 
NIOSH Firefighter Radio Communications Appendix B 

TriData Corporation 96 September 2003 

EFD has used VHF radios with fairly good success. Problems with building penetration 

have been rare. With a portable radio, personnel can talk throughout half of the city. As a 

result of Canada reclaiming some of the VHF frequencies and essentially narrowing the 

available bandwidth, the EFD is implementing a new 800 MHz system in summer 2003, 

which will provide 95 percent coverage throughout the city limits. 

The communications problems encountered the current system are related to limited 

tactical channels and operation in a firefighting environment. Specifically, the EFD only 

has access to its dispatch channel and one tactical channel. When simultaneous incidents 

require a tactical channel, the incidents will need to share the one tactical channel or one 

will have the tactical channel while the second uses the dispatch channel for its 

operations. 

The EFD has experienced numerous problems due to use of full personal protective 

equipment (PPE) and SCBA. Members of the EFD have experienced difficulty operating 

the portable radio, especially the channel selector and volume control while wearing the 

bulky firefighting gloves that limit dexterity. Radio transmissions have been difficult to 

understand from the interior of a firefighting operation because voice distortion is created 

through the mask. Also mentioned by EFD staff is that voices are often difficult to 

understand because the interior firefighter transmitting is often out of breath. And lastly, 

since all firefighters have a portable radio when assigned to fire department apparatus, 

they do not cover their radio microphones or turn them off completely, a situation not 

recommended from both a safety and operational perspective. 

The EFD reports success during radio transmission in new buildings with leaky coaxial 

cables. The EFD is working diligently to have some older building retrofitted with this 

technology to further enhance the quality of radio transmissions. 

Fairfax County, VA 

Fairfax County, Virginia is located just outside Washington, D.C. The county 

encompasses nearly 400 square miles with a resident population of approximately 

970,000. The Fire and Rescue Department has 1,166 uniformed staff who responded to 

89,246 calls for service in FY2002. 

The county includes various structures, ranging from standard residential and commercial 

buildings to secure government installations (e.g., the Central Intelligence Agency’s 

Headquarters). 

The fire department currently uses an 800-MHz trunked digital system for 

communications with 20 available frequencies. Communications are simulcast on the 

department’s “old” 460 MHz channel as well. Dispatch and operations are separated; 

units are dispatched on one channel, while day-to-day operations are handled on another. 

Fairfax County is acquiring 20 additional analog channels, which will provide a back-up 

system should the digital system fail. 
NIOSH Firefighter Radio Communications Appendix B 

TriData Corporation 97 September 2003 

For working incidents, operations and command are assigned to additional channels to 

avoid impinging on tactical communications. The incident commander monitors the 

command and incident channels, as well as a talk-around channel for structures with 

communications problems. Fairfax uses two available talk-around channels, which are 

not repeated. In the event of communications problems during an incident, the incident 

commander can order all units on the incident to switch to the talk-around channel. 

Recently, the department purchased the Incident Commander Radio Interface (discussed 

in more detail in Chapter III) for use by the communications officer and to interface the 

talk around channels with operational channels. The department is developing Standard 

Operating Procedures for using the device. 

The department reports that there are a variety of dead spots in the county, particularly in 

and around a large regional mall as well as the local trauma center. To address these 

issues, the county is constructing three additional tower sites, for a total of 11 throughout 

the county. Also, a recent ordinance requires new buildings to maintain radio coverage 

throughout the structure. This has been accomplished in the county’s new jail, which has 

a combination of a bi-directional amplifier and leaky coaxial cable in the ceilings (see 

Chapter III for more details). 

Since transitioning to an 800 MHz system, Fairfax has had one failure, where the system 

entered “Failsoft” (a condition where specific channels are maintained, while the majority 

are offline). As a result, the dispatch center is preparing contingency plans to address 

such incidents in the future. More on such plans can be found in Chapter III 

Fairfax County’s public safety is experiencing system coverage degradation from Nextel 

(interference). The Nextel system, also operating on the 800-MHz band, appears to be 

incompatible with the pre-existing systems in the 800-MHz band. One proposed solution 

by the Department of Information Technology is to move Nextel out of the 800-MHz 

band. The county is opposed to reorganizing or restructuring its public safety radio 

system. 

The fire department, has issued some officers Nextel cellular phones. The department is 

in the process of purchasing these phones for all front-line suppression and EMS 

apparatus (medic units are already equipped with a conventional cellular phone for 

hospital communications). 

Gettysburg, OH 

The Gettysburg Rural Fire Department is a private, all-volunteer department. Located in 

Darke County, the department protects a population of approximately 3,700 over a 60 

square mile area. The department operates out of a single fire station. Total call volume is 

about 190 calls per year – 110 EMS calls and 80 fire calls. 

Mostly rural, and residential with some commercial structures, Gettysburg’s commercial 

structures are privately owned farmhouses. The tallest structure is about two stories. The 

geography and terrain of the area is mostly flat, with some hills. 
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The department operates on a UHF radio system (154-MHz) that includes four tactical 

operations channel and one dedicated dispatch center. 

The biggest challenge for fire department radio communications is interference. In 

Gettysburg, firefighters often encounter radio interference from the neighboring Miami 

County. Miami County, located to the east of Darke County, sits at a higher elevation and 

has higher towers. Although Miami County uses the 800 MHz radio system, it dispatches 

off of UHF. During its dispatches, it virtually blocks out communications to the 

Gettysburg Rural Fire Department. 

One solution is increased system design and infrastructure for Darke County. However, 

due to a shortage of money, the county cannot presently afford to add more system 

infrastructure. 

Los Angeles, CA 

The Los Angeles Fire Department (LAFD) protects approximately 3.7 million people 

who live in the second largest city in the United States. The department has over 3,200 

uniformed personnel, operating out of 103 fire stations, covering a land area over 470 

square miles. 

The LAFD uses a conventional 800 MHz system, which has been in place for the past 

decade. Every firefighter is issued a portable radio while on duty. There are 18 channels; 

three of which are dispatch channels broken down by Metro and Valley area. The city is 

divided into three regions, and each has a channel. There is also one command channel 

for the chiefs. 

The location of a Nextel tower is one challenge for the department. The Nextel operates 

on the same frequency and can cause radio interference. 

It is hard to maintain radio coverage for a city of this size and diverse topography, Hills 

and mountains present challenges. These general challenges do not regularly occur... 

Still, the LAFD has worked carefully on the strategic placement of towers and repeaters 

to address coverage concerns. And, in those are where dead spots are more frequent, the 

city has back-up repeater sites. . 

A common problem in many cities, communications in subways and tunnels present few 

challenges for the LAFD because the subways and tunnels are wired with underground 

cables, which carry a signal for four or five of the fire department channels. 

For major incidents, the LAFD reports no operational problems with the communication 

system per se; problems the department experiences are more of logistical issues. The 

system can handle the capacity, but since multiple channels may be used at the same 

time, firefighters are not always on the correct channel. 
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Interoperability is another difficulty for the fire department. Because the police and 

public works departments operate on a different radio system (500 MHz UHF band), the 

fire department cannot communicate directly with these departments. 

Milwaukee, WI 

The Milwaukee Fire Department protects a population of about 600,000 spread over 96 

square miles. There are 1,100 sworn personnel in the department. 

Currently, the Milwaukee Fire Department (MFD) uses a 400 MHz system with eight 

channels. Two channels are dedicated to dispatch; one is the main dispatch channel and 

the second is for the officers on the fireground to call dispatch. Five other channels are 

for fireground only. There is no interoperability with other city agencies. 

Overall, the communications system works about 98 percent of the time. The technology 

and equipment were not reported as issues. 

There are some spots (e.g., buildings and basement levels) where equipment does not 

work. For high-rise structure fires (anything over five stories), it is the department’s 

policy to put the command center in the lobby of the building (if it is safe to do so). 

Typically, there is good communication within the building. If they experience problems, 

they will use a runner. 

The single biggest problem the department has with communications is human error: 

firefighters do no know what channel they are on and do not communicate frequently 

with incident commander. The department considers this problem to be an issue of 

accountability and not a training problem. 

Phoenix, AZ 

The Phoenix Fire Department protects a population of nearly 1.4 million across 500 

square miles. It has over 1,366 sworn personnel that operate from 47 fire stations. In 

2002, the fire department responded to 133,519 calls – 104,635 EMS calls and 28,884 

fire and non-EMS calls. 

Currently, the fire department uses a conventional direct radio communication system in 

VHF. The primary infrastructure – two tower sites above the North Mountain and South 

Mountain and diversity receivers – does not use repeaters. The diversity receiver operates 

like a small radio tower and receives the emitted radio signal on several antennas. The 

department operates 24 VHF channels and there are 36 diversity receivers per channel. 

The department has had much success with this system. However, there are some 

challenges. High-rise buildings, basements, and any other structure with dense concrete 

may cause communication problems. With this system, the two major difficulties are fade 

and feedback. Where people are clustered together and one person transmits, there is lots 

of feedback. Fade is more related to the distance between one radio transmitting a signal 

and the other receiving it. The sound is usually muffled and difficult to understand. 
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Like many departments, Phoenix has problems using portable radios in a hostile 

environment, a working fire incident with zero visibility and wearing full personal 

protective equipment. The Phoenix Fire Department had a fire fatality a few years ago. 

The Department determined three factors the department needs to ensure firefighter 

safety – airway management, firefighter rescue techniques, and radio communications. 

The firefighter did issue a “mayday,” and was heard over the radios. The fire department 

could not locate and rescue the firefighter before his death. 

Dead spots are, for the most part, not a problem for the fire departments. The diversity 

receivers are strategically located throughout the City. There are a lot of them. Each 

receiver has the ability to receive a radio signal from within a 2-mile radius. 

The City of Phoenix is incorporating an 800 MHz digital trunked radio communications 

study. This is not the fire departments preference, but rather a recommendation that was 

made by a consultant for the police department. In addition, there is a big cost savings for 

the City to operate on the 800 MHz system. The City only has to operate and support one 

radio system. Also, there is less combined infrastructure. The system is being split by 

Phoenix and Mesa, Arizona. 

The conventional VHF radio system with diversity receivers has been successful. The fire 

department reports effective use on the fireground. While each channel on the 800-MHz 

trunked system is repeated, it must reach a tower to communicate. That is not the case for 

the current system. Even if simplex or talk-around channels are built in to the system 

(part conventional), firefighters wearing full PPE still have difficulty changing channels 

in a dark, hostile environment. 

The department reports that transitioning to the new communications system puts 

firefighters lives at greater risk. The Department must train each firefighter on the new 

system, whole changing current behaviors and adapting new ones for the current system. 

Training is to begin soon on the new system, before it is implemented in 2005. 

Pittsburgh, PA 

Pittsburgh, a mountainous city, covers 57 square miles. The Pittsburgh Fire Department 

serves a population of 360,000. The largest concentration of commercial activity is in the 

downtown area where there are numerous high-rise buildings. 

The fire department is part of a centralized UHF communications system for all city 

services—emergency, police, fire, etc, with a single, centralized dispatch. However, a 

single channel is dedicated to fire dispatch, another to fire ground communications, and 

then additional channels are available on demand, whenever necessary. This flexibility to 

use more or less channels has proved helpful for the department in the past. 

Large and high-rise structures, below grade structural areas, and tunnels areas pose the 

greatest communications problems for the Pittsburgh fire department. If the firefighter 

inside cannot communicate to the outside, the department bypasses the repeaters and goes 

to two-way radio talk around system for communications. The department uses these 
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radios in other situations as well, whenever the mountains interfere with reception on the 

larger system. Pittsburgh’s talk around radios have a 1⁄2-mile communications radius. Cell 

phones and pagers are used strictly for administrative purposes, although most of the 

firefighters carry one or the other. 

The communications system for the City of Pittsburgh seems to work well. Department 

staff have noted that an improvement it would be “portable radios with built-in repeaters” 

for the fireground.

Portland, OR 

Portland has a population of over 525,000 within city limits, and 1.8 million living within 

the metropolitan area. The city is approximately 130 square miles, situated 50 miles 

inland on the Columbia River midway between the Coast to the west and Cascade 

Mountain range to the east. The Columbia River is quite wide and Portland has one of the 

West Coast’s largest ports. The city is surrounded by the West Hills. Also in the vicinity 

of the City are Mount Hood and Mount Saint Helens, two volcanoes over 10,000 feet. 

Portland has a citywide consolidated communications system on an 800 MHz Motorola 

“Smart Zone” system. Set up in 1994, the system has had several software upgrades. 

There are 13-talk group channel and 1 administrative channel for the fire department. It is 

estimated that the system is running at 40 percent capacity. Each company has a mobile 

data terminal and three portable radios. The officer, the driver, and one two-person team 

have a radio (apparatus are staffed with four personnel). The city has four primary 

simulcast transmitter sites and 11 small repeaters. A fifth transmitter site has been 

planned, but has not been put into operation. 

The terrain surrounding Portland creates communication problems in shadowing and 

dead spots. To curb such difficulties within the central area, the city placed a large 

antenna above the West Hills. Coverage is still a problem in high-rise buildings, 

basements and sub-basements, and the light rail system underground tunnels. The tunnels 

have built-in antenna system, which alleviates most of the communication problems. 

In addition, the harbor provides significant communication problems. The fire department 

has many shipboard incidents and while the port also has antennas and other 

communication support equipment, communications are a problem below deck. 

To resolve some of its communication challenges, the department uses its simplex talk 

around channels in areas where communications are challenging. The department has 

created specific SOPs for such incidents, and trains on them as well. The Department is 

also in the process of acquiring mobile repeaters for chief vehicles. 

The city also experiences problems with the Nextel cellular phone system. As with other 

departments, the Nextel system, also operating on the 800-MHz band, is incompatible 

with the pre-existing systems in the 800-MHz band. To prevent major interference with 

fire department communications, Nextel and the fire department swapped frequencies to 
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resolve the problem. The fire department gave up a channel on the end of their radio band 

for Nextel’s channel in the middle of the city’s band. 

San Antonio, TX 

The City of San Antonio is the ninth largest city in the United States and third largest in 

the State of Texas. It has a population of over 1.1 million and a land area of more than 

400 square miles. The San Antonio Fire Department serves the City with more than 1,000 

uniformed firefighters operating out of 48 fire stations. 

San Antonio is large, so, the fire department often provides fire protection and response 

to its many high-rise buildings (some 30-40 stories) and other large structures such as the 

Alamo Dome, SBC Center, a Convention Center, Coliseum, etc. There are no 

underground tunnels or transportation systems. 

The San Antonio Fire Department uses a Motorola Simulcast System (UHF), with eight 

channels: one dedicated for dispatch, two for EMS, and the remainder for tactical fire 

operations. Each channel is repeated. 

The city is upgrading to an 800-MHz Trunked system by the end of this year. It is 

upgrading because the old system is antiquated. Some parts are no longer made for the 

radios and other equipment is outdated. The radios are also less resistant when exposed to 

hazardous conditions, such as water. 

There are no inadequate system capacity issues in the department. . However, there are 

some “dead spots” in the city, scattered about. There are also dead spots in some of the 

unincorporated type areas outside of the City (where the SAFD provides service). It is 

believed that the dead spots are generally caused by a lack of infrastructure – not enough 

repeaters, transmitters, etc. The department believes that adding new infrastructure (as 

part of the new 800 MHz upgrade) and strategically placing towers and repeaters, will 

resolve some of these issues. 

Interoperability is important communication problem for the department. The fire 

department cannot communicate with other city agencies or neighboring jurisdictions. In 

order to communicate with other city department, the dispatch center will “patch” the 

various departments together. 

The 800 MHz system has already been tested in the city, with 95 percent coverage. The 

All city agencies will be on the 800 MHz system, possibly the county’s sheriff’s office 

too. Other jurisdictions, if they choose, may also be on the city’s system (by leasing space 

from the city). The new system will have a lot of built-in infrastructure – 11 Tower sites. 

The city will own the entire infrastructure. Each firefighter will be issued a portable 

radio. 
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San Diego, CA 

The San Diego Fire-Rescue Department (SFRD) consists of 1,100 uniformed personnel 

who operate out of 44 stations and serves a population of 1.3 million people across 330 

square miles. The Department’s response area includes high-rise buildings, warehouses 

and other “typical” city hazards as well as miles of beach and shoreline. 

The department uses a Motorola 800 MHz system, which has been in place for 11 years. 

The operations units also carry VHF portables because neighboring departments (to 

which SFRD provides mutual aid) use this system. Dispatch and operations channels are 

separate; channels are assigned by geography. Each battalion (7 total) operates on its own 

channel. There is also one channel for all medical calls and one channel for all traffic 

incidents. Each channel has repeaters that are located throughout the City, either on 

mountaintops, high-rise buildings, etc. 

Until recently, SFRD used a VHF communications system. Unfortunately, the city was 

unsuccessful in eliminating VHF interference from Mexico and has since migrated to the 

800 MHz system. 

The 800 MHz system works, but the major challenge for the city is to train 1,000 

firefighters and 2,000 police officers to use it. The system is more complex than the one it 

replaces, and there are some in the department who are very good with the radios while 

others are not. 

To combat dead spots in structures, the department will use firefighters as mobile 

repeaters. In other words, a firefighter will stand at a stairwell support (within line of 

sight), another firefighter will be below him, etc. and the message is repeated to the 

outside. 

For the Super Bowl, the department used a Mobile C.O.W. (Cellular on wheels), which 

acts as a mobile antenna to allow communications to be repeated outside a building. This 

technology is also used for the San Diego Convention Center. The Mobile C.O.W. is run 

through an underground tunnel, beneath the convention center. 

Cruise ship fires also pose a challenge – ships have a radio on each deck at each door. 

The department typically needs to set up firefighters as mobile repeaters to facilitate 

communications. 

The department also uses cell phones and issues personnel alphanumeric pages. Senior 

staff is issued Blackberry wireless devices. 

San Francisco, CA 

San Francisco has a population of more than 775,00 spread over a small area, 49 square 

miles. The San Francisco Fire Department (SFFD) has more than 1,700 uniformed 

personnel operating out of 42 stations. 
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The city operates an 800 MHz radio system and has for the past eight years. Prior to that, 

the city was using an older Motorola 400 MHz system. The newer system allows the 

department to have more working channels and interoperability. There are 16 channels; 

three controlled for dispatch. Each battalion has an assigned channel. There are 10 

battalions. 

Despite the upgrade, the radio system is still limited inside high-rises. Dead spots still 

exist, but most have been eliminated. 

The department has added more towers and repeaters. It is currently upgrading the system 

with portable repeaters. The city is moving repeaters to higher areas of the city, to 

prevent interference from other high-rise buildings. 

BART, San Francisco’s underground public transportation system (subway), does pose 

some communication problems for the SFFD. Radios for BART are issued to fire stations 

located near subway stations. These radios are also carried by some Battalion Chiefs. 

There is no interference from the shipping channels. 

Schaumburg, IL 

The Schaumburg Fire Department (SFD) , a full-time career fire department, is located 

approximately 30 miles northwest of Chicago. Schaumburg has a resident population of 

approximately 75,000 people and encompasses roughly 20 square miles of mostly flat 

terrain. The SFD response district includes single-family residences, multi-story 

residential structures, including hotels, and high-rise commercial office buildings. 

The SFD has used 800 MHz technologies since 1988. Its initial 800 MHz system had one 

antenna site for the entire Village. A new system, which went on-line in April 2003, uses 

four antenna sites. Under its old system, the SFD experienced numerous dead spots 

throughout the Village where firefighters could not receive nor transmit radio traffic. 

Personnel of the SFD also had difficulty transmitting out of and into structures that used 

Lexan glass as windows or buildings that used significant amounts of concrete in 

construction. 

Most of the radio/communication problems the SFD experienced were in high-rise 

structures, which typically employ large amounts of concrete and Lexan glass during 

construction. The only reliable way the SFD could transmit out of high-rise structures 

was if the firefighter stood at the window. The SFD has experienced very few problems 

while operating at single-family residential structure fires. 

The SFD, which shares the 800 MHz system with Law Enforcement and Public Works, 

frequently experienced busy signals under the old system that utilized only three trunks. 

In its research for expanding its network of trunks, the SFD found from the FCC that few 

trunks are available; the SFD was able to purchase a trunk from a bus company in New 

Jersey that went out of business. 
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The new radio system and its new antenna sites have dramatically improved 

communications during structural firefighting events for the SFD. New building codes 

required signal boosters during construction for certain types of buildings. This has also 

helped improve communications for the SFD. 

Like many departments, the SFD struggles with the portable radio and the ease of using it 

in a zero-visibility environment, while wearing bulky fire department gloves. The only 

solutions that the SFD has come up with as a precautionary measure, as have other 

localities, is to program the extremes of the channel selector on the portable radio 

(selector turned all the way left or right) to the same, recognizable channel (usually 

dispatch) regardless of zone selection. If the firefighters operating in a zero-visibility 

environment accidentally change the radio from the tactical operations channel and are 

not able to find the appropriate channel, they can turn the selector all the way in either 

direction to ensure that they will be able to talk to a dispatcher in the event they need 

help. 

The SFD has enhanced radio interface and operability with its mutual aid neighbors by 

utilizing transponders on the apparatus and command vehicles that can convert VHF 

radio to 800 MHz and vice versa. This way, the SFD can continue to operate with only 

one radio system. 

Springfield, NJ 

Springfield, New Jersey is located about 23 miles southwest of New York City. The 

township encompasses 5.06 square miles of mostly flat terrain, which contains a 

combination of residential, commercial, and industrial structures. Springfield has a 

resident population of 14,250 and a daytime population of 30,000. 

The Springfield Fire Department (SFD) is a combination department, comprised of 

approximately 33 career and volunteer firefighters and officers. The SFD currently uses a 

high band radio system, at approximately 470 MHz. The Chief and Deputy Chief (as well 

as other senior Township officials) are issued also Nextel cellular phones to facilitate 

communication between these officials. 

Unlike many departments nationwide, the township reported that the SFD does not 

typically experience difficulties transmitting in and out of structures or from floor to 

floor. Instead, the department contends with radio interference from two neighboring 

jurisdictions that operate on similar frequencies. In both cases, the jurisdictions are at a 

higher elevation than Springfield and have higher radio towers. Depending on the 

weather and time of day, transmission from these departments “step on” SFD operations, 

making it difficult for units to transmit or receive messages from dispatch. 

To alleviate issues with neighboring jurisdictions, discussions are underway to study the 

feasibility of trunking the current radio system because there are not enough frequencies 

available for the SFD to completely modify their radio system (e.g., transition to 800 or 

900 MHz). 
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Wichita, KS 

The Wichita Fire Department (WFD) serves over 340,000 residents of Wichita. The city, 

located in Sedgwick County, has a diverse economy that includes agricultural services, 

aviation, and oil and gas production. The City serves a large hinterland in central Kansas. 

The Fire Department covers over 136 square miles of the City. The Department provides 

a full range of fire, rescue, hazardous materials, and other services. 

The Wichita Fire Department operates on an 800-MHz trunked system. This system has 

been operating for approximately 10 years. The fire department has one dispatch channel, 

one operations channel, seven tactical channels, one channel for Administration, and one 

command channel (for multi-agency use). Each company has a portable radio (company 

officers). 

Prior to the 800 MHz system, the city had an old 2-channel system. Even with additional 

repeaters and other modifications, problems stemmed from a lack of channels. 

All of the public safety departments within the City are connected to the 800 MHz 

system. 

Interacting with surrounding jurisdictions, also using an 800 MHz system, is problem for 

the WFD. Some of the surrounding jurisdictions are not tied into the Wichita system. 

The WFD also experiences problems communicating in elevators, large buildings, 

basements and sub-basements, and malls. There is often difficulty in transmitting a 

signal. The lower level of the mall has difficulty transmitting and receiving. To reduce 

the magnitude of the problem, firefighters must use the “talk around” channel, or simplex 

mode (radio to radio). 

The department has added repeaters in the past, with some success. The department 

knows which buildings have problems and do their best to work around them. There are 

relative few “dead spots” around the city. 

The WFD would like to try mobile vehicles, but does not have the financing. The city 

does not have any built-in radio ordinances for buildings. 
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GLOSSARY OF TERMS AND ABBREVIATIONS 

Terms 

Attenuation - The decrease in intensity of a signal, beam, or wave as a result of absorption of 

energy and of scattering out of the path to the detector, but not including the reduction due to 

geometric spreading. 

Diffraction - The deviation of an electromagnetic wavefront from the path predicted by 

geometric optics when the wavefront interacts with, i.e., is restricted by, a physical object 

such as an opening (aperture) or an edge. 

Duplex – A communications mode with the ability to transmit and receive radio traffic 

simultaneously through two different frequencies, one to transmit and one to receive.

Multipath – The propagation phenomena that results in radio signals’ reaching the antenna by 

two or more paths. Causes of multipath include atmospheric ducting, ionospheric reflection 

and refraction, and refraction from terrestrial objects such as mountains or buildings. 

Permittivity - A measure of the ability of a material to resist the formation of an electric field 

within it. Also called dielectric constant, relative permittivity. 

Project MESA – Project MESA is an international partnership producing globally applicable 

technical specifications for digital mobile broadband technology, aimed initially at the sectors 

of public safety and disaster response.

Rake Technique - A receiver technique that uses several baseband correlators to individually 

process several signal multipath components. The correlator outputs are combined to achieve 

improved communications reliability and performance. 

Reflection - The abrupt change in direction of a wavefront at an interface between two 

dissimilar media so that the wavefront returns into the medium from which it originated. 

Refraction - Retardation, and—in the general case—redirection, of a wavefront passing 

through (a) a boundary between two dissimilar media or (b) a medium having a refractive 

index that is a continuous function of position, e.g., a graded-index optical fiber. 

Repeater - An analog device that amplifies an input signal regardless of its nature, i.e., analog 

or digital. A digital device that amplifies, reshapes, retimes, or performs a combination of any 

of these functions on a digital input signal for retransmission. 

Scattering - Of a wave propagating in a material medium, a phenomenon in which the 

direction, frequency, or polarization of the wave is changed when the wave encounters 

discontinuities in the medium, or interacts with the material at the atomic or molecular level. 

Simplex – A communications mode with the ability to transmit or receive in one direction at a 

time. Simultaneous transmission cannot occur. 

Trunking – In radio in communications, it is a system that may include a single user of 

different workgroups, which uses a group of radio frequencies (a trunk). The system is 

dynamically controlled by a computer, which directs a transmission to an available channel 

or frequency. 
NIOSH Firefighter Radio Communications Glossary 

TriData Corporation September 2003 108

Wavefront - The surface defined by the locus of points that have the same phase, i.e., have 

the same path length from the source. 1. The wavefront is perpendicular to the ray that 

represents an electromagnetic wave. 2. The plane in which the electric and magnetic field 

vectors lie is tangential to the wavefront at every point. 3. The vector that represents the 

wavefront indicates the direction of propagation. 

Abbreviations and Acronyms 

3G third generation 

ac alternating current 

AGC automatic gain control 

AM amplitude modulation 

AMPS advanced mobile phone system (cellular system) 

AOA angle of arrival 

ARRL American Radio Relay League 

ATM asynchronous transfer mode 

AWGN additive white Gaussian noise 

BDA bi-directional amplifier 

BFRL Building and Fire Research Laboratory 

BPL broadband power line 

bps bits per second 

CDMA code division multiple access 

CFP contention-free period 

cm centimeter 

COW Cellular on Wheels 

CP contention period 

CSMA carrier sense multiple access 

DARPA Defense Advanced Research Projects Agency 

dB decibel 

dc direct current 

DCF distributed coordination function 

DES Data Encryption Standard 

DSL digital subscriber line 

DSP digital signal processor 

DTIC Defense Technical Information Center 

EDCF enhanced distributed coordination function 

EHF extremely high frequency 

ELF extremely low frequency 

EMS emergency medical service 

ETSI European Telecommunications Standards Institute 

FCC Federal Communications Commission 

FDNY Fire Department of New York 

FEC forward error correction 

FEMA Federal Emergency Management Agency 
NIOSH Firefighter Radio Communications Glossary 

TriData Corporation September 2003 109

FM frequency modulation 

FSK frequency shift keying 

GHz gigahertz 

GIS Geographic Information System 

GPS Global Positioning System 

GSM global system for mobile communication (cellular phone technology) 

HC hybrid coordinator 

HCF hybrid coordination function 

HDTV high-definition television 

HF high frequency 

HVAC heating, ventilation, and air conditioning 

Hz hertz 

IAL Intel Architecture Laboratories 

ICP incident command post 

IETF Internet Engineering Task Force 

IF intermediate frequency 

IP Internet protocol 

ISL Information Systems Laboratory 

ISM industrial, scientific, medical 

kHz kilohertz 

km kilometer 

LAN local area network 

LCD liquid crystal display 

LF low frequency 

LOS line of sight 

LV low voltage 

M mega 

m meter; milli 

MAC medium access control 

MANet mobile area network 

MEA mesh-enabled architecture 

MHz megahertz 

MIMO multiple input, multiple output 

MRS Mine Radio Systems Inc. 

MSSI Multi Spectral Solutions, Inc. 

MV medium voltage 

mW milliwatt 

NFPA National Fire Protection Association 

NIOSH National Institute for Occupational Safety and Health 

NIST National Institute of Standards and Technology 

NLM National Library of Medicine 

NLOS non-line of sight 

NOI notice of inquiry 

NPRM notice of proposed rule making 
NIOSH Firefighter Radio Communications Glossary 

TriData Corporation September 2003 110

NTIA National Telecommunications and Information Administration 

OFDM orthogonal frequency division multiplexing 

OOK on/off keying 

PAM pulse amplitude modulated 

PAN personal area network 

PAS personal accountability system 

PASS Personal Alarm Safety System 

PCF point coordination function 

PCS personal communications system 

PED personal emergency device 

PLC power line communication 

PLL phase-lock loop 

PN pseudo noise 

PPE personal protective gear 

PPM pulse position modulation 

PRF pulse repetition frequency 

PSWAC Public Safety Wireless Advisory Committee 

QDMA quadrature division multiple access 

QoS quality of service 

RF radio frequency 

SBIR small business innovation research 

SCBA self-contained breathing apparatus 

SDTV standard-definition television 

SHF super high frequency 

SNR signal-to-noise ratio 

TDMA time division multiple access 

TDOA time difference of arrival 

TTCP The Technical Cooperation Program] 

TTE through-the-earth 

UHF ultra high frequency 

USFA U.S. Fire Administration 

UWB ultra wideband 

VCO voltage-controlled oscillator 

VHF very high frequency 

VLF very low frequency 

WAP Wireless Application Protocol 

WLAN wireless local area network 

WPAN wireless personal area network 

WPI Worcester Polytechnic Institute
NIOSH Firefighter Radio Communications 

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MASTER REFERENCE LIST 

1. Adams, David S. and Tamar Granot. “A Description and Analysis of a Radio 

Station Operation During a Forest Fire.” Columbus, OH: Disaster Research Center, 

1974. 

2. “Initial Lessons Learned in Testing and Deploying the ACU-1000” (Technical 

Memorandum). AGILE (Advanced Generation of Interoperability for Law 

Enforcement) NLETC Project Team. 6 December 2002. 

http://www.agileprogram.org/documents/acu1000/acu1000memo.html.

3. “Allocation of the Radio Spectrum in the United States.” 10 January 2003. 

http://www.jneuhaus.com/fccindex/spectrum.html. 

4. “APCO Project 25 Standards for Public Safety Digital Radio.” 6 December 2002 

http://www.apcointl.org/frequency/project25/information.html. 

5. Bishop, Don. “700 MHz Monopoly?” Mobile Radio Technology November 2002: 

14-22. http://iwce-mrt.com/ar/radio_mhz_monopoly. 

6. Bishop, Don. “Improve FDNY Radio Communications.” Mobile Radio Technology

1 October 2002. 6 December 2002. http://iwcemrt.com/ar/radio_improve_fdny_radio/. 

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BIBLIOGRAPHIC REFERENCES BY SUBJECT AREA 

Underground/Below-Grade Communications 

15 17 18 19 20 21 22 23 33 41 104 105 115 116 127 128 129 130 173 174 

175 177 179 180 186 187 198 204 205 207 211 213 262 287 288 291 

MANet Ad Hoc 

24 44 97 133 134 135 136 137 138 139 156 157 158 165 168 169 171 

189 231 232 247 251 266 268 270 271 272 273 274 275 276 277 278 295 302 307 309 313 

341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 

Ultra Wideband 

13 50 106 113 114 131 140 141 142 144 145 146 147 148 149 150 151 152 159 

206 208 209 210 223 245 280 281 282 283 284 286 287 292 293 301 303 305 306 360 361 

362 363 

Power Line Communications 

199 202 234 248 249 250 252 253 254 255 256 258 259 260 260 261 263 264 265 294 357 

358 359 

Propagation 

78 79 80 181 182 203 212 214 215 216 218 219 220 221 222 237 239 241 

242 243 244 246 290 308 311 

Modulation 

71 74 170 172 220 324 328 

Location 

99 107 108 109 110 111 161 166 188 225 226 227 228 229 230 233 235 236 

238 240 279 285 298 299 300 327 329 

Regulatory 

3 5 25 32 39 66 72 82 94 95 96 98 118 125 143 163 190 191 193 196 

257 269 297 304 
NIOSH Firefighter Radio Communications Master Reference List 

TriData Corporation 141 September 2003 

Organizations 

8 60 61 62 63 64 65 88 91 167 

Fire Service Communications 

2 6 9 10 16 27 28 31 34 42 47 51 52 54 58 67 69 70 75 76 77 81 83 84 86 

87 90 101 117 119 120 121 122 123 124 126 132 153 154 155 160 162 178 183 

192 194 195 224 296 314 316 317 318 319 320 330 335 336 337 338 364 

Accountability Products 

85 176 184 185 

Repeaters 

100 102 103 

Miscellaneous Products 

73 197 200 201 332 339 340 325 326 340 

Medical Communications 

12 29 36 37 38 46 49 92 315 

Emergency Communications 

1 11 26 35 40 43 45 48 53 55 56 89 93 310 312 

Project 25 

4 30 59 

Bluetooth 

7 112 267 

High-Voltage Alternating Current 

164 
NIOSH Firefighter Radio Communications Master Reference List 

TriData Corporation 142 September 2003 

Miscellaneous 

14 57 68 

Channel Coding, Interleaving, and Encryption 

323 331 333 334 

Smart Antennas 

321 322