NTIA Report 06-440 

FEDERAL LAND MOBILE OPERATIONS 

 IN THE 162-174 MHz BAND 

 IN THE WASHINGTON, D.C. AREA 

Phase 1: STUDY OF AGENCY OPERATIONS 

Report Series

August 2006 

U.S. DEPARTMENT OF COMMERCE 

Carlos M. Guiterrez, Secretary 

John M.R. Kneuer 

 Acting Assistant Secretary 

For Communications and Information 
PROJECT MANAGEMENT 

Fredrick R. Wentland 

Associate Administrator 

Office of Spectrum Management 

Edward F. Drocella 

Chief, Spectrum Engineering and Analysis Division 

TEAM LEADER 

Gary Patrick 

REPORT AUTHORS 

Charles Hoffman 

Robert Matheson 

Fred Najmy 

Robert Wilson 
ACKNOWLEDGEMENTS 

The authors would like to thank the following National Telecommunications and 

Information Administration (NTIA) personnel for their review and contributions to this report: 

Gerald Hurt, Spectrum Engineering and Analysis Division (SEAD); Thomas Sullivan, SEAD; 

Edward Drocella, SEAD; Cecilia Tucker, SEAD; Marianne Wiler, Information Technology 

Division; Margaret Luebs, Institute for Telecommunications Sciences, Boulder, Colorado; and 

Suzette Williams, Spectrum Services Division. 

 The authors are especially grateful to the representatives from the various federal 

agencies that took the time to provided valuable information on their current operations and 

future plans. 
i 

TABLE OF CONTENTS 

LIST OF TABLES.............................................................................................................iii

LIST OF FIGURES ........................................................................................................... iv

GLOSSARY ..................................................................................................................... vii

EXECUTIVE SUMMARY ............................................................................................... ix

SECTION 1 INTRODUCTION ......................................................................................1-1 

1.1 Background.............................................................................................. 1-1 

1.2 Scope of Work .........................................................................................1-5 

1.2.1 Overall Objective.....................................................................................1-5 

1.2.2 Specific Objectives ..................................................................................1-5 

1.2.3 Other Related Work .................................................................................1-6

SECTION 2 PHASE 1 OVERVIEW............................................................................... 2-1 

2.1 General..................................................................................................... 2-1 

2.2 Concept of the Signal Capacity Analysis Program (SCAP) ....................2-2 

2.3 Selection of 162-174 MHz Band in the Washington, D.C. area..............2-3 

2.4 Sources of Current Usage Data................................................................2-3

SECTION 3 CHARACTERISTICS OF MOBILE RADIO SYSTEMS ......................... 3-1 

3.1 General..................................................................................................... 3-1 

3.1.1 Simplex Radio Systems ...........................................................................3-1 

3.1.2 Radio Repeater Systems ..........................................................................3-2 

3.1.3 Mobile Talk-Around Mode......................................................................3-3 

3.1.4 Multi-Site Repeater Systems....................................................................3-3 

3.1.5 Half-Duplex Radio Systems ....................................................................3-4 

3.1.6 Multi-Site Duplex Systems...................................................................... 3-5 

3.1.7 Receive-Only Sites................................................................................... 3-6 

3.1.8 Simulcast Radio Systems.........................................................................3-7 

3.1.9 Trunked Radio Systems ...........................................................................3-8 

3.2 Summary.................................................................................................. 3-9

SECTION 4 FEDERAL OPERATIONS IN THE 162-174 MHz BAND.......................4-1 

4.1 General..................................................................................................... 4-1 

4.2 Allocation................................................................................................. 4-1 

4.2.1 Use of the 162-174 MHz Band ................................................................ 4-3 

4.3 Operational Description of Each Agency’s LMR Operations ............... 4-10 

4.3.1 United States Department of Agriculture (USDA)................................ 4-10 

4.3.2 United States Department of Commerce (DOC) ...................................4-11 

4.3.3 United States Coast Guard (USCG).......................................................4-13 

4.3.4 United States Department of Defense (DOD) .......................................4-14 

4.3.5 United States Department of Energy (DOE) .........................................4-15 
ii 

4.3.6 Federal Aviation Administration (FAA)................................................4-16 

4.3.7 United States Department of Homeland Security (DHS) ...................... 4-17 

4.3.8 United States Department of Interior (DOI) .......................................... 4-18 

4.3.9 United States Department of Justice (DOJ)...........................................4-19 

4.3.10 United States Department of the Treasury (Treasury)...........................4-20 

4.3.11 United States Capital Police (USCP).....................................................4-21 

4.3.12 United States Postal Service (USPS) .....................................................4-23 

4.3.13 United States Department of Veteran’s Affairs (VA)............................ 4-24 

4.3.14 Other Agencies or Bureaus .................................................................... 4-25 

4.4 Summary................................................................................................ 4-26

SECTION 5 OTHER FEDERAL GOVERNMENT EFFORTS ..................................... 5-1 

5.1 General..................................................................................................... 5-1 

5.2 Migration to Narrowband Technology .................................................... 5-1 

5.3 Technical Performance Standards............................................................5-2 

5.3.1 Trunking Technology............................................................................... 5-3 

5.3.2 162-174 MHz Band Restructuring...........................................................5-3 

5.3.3 Frequency Reuse...................................................................................... 5-3 

5.4 Initiatives And Spectrum Efficiency Improving Programs ....................5-4 

5.4.1 NTIA Spectrum Summit.......................................................................... 5-4 

5.4.2 Federal Communication Commission’s Spectrum Policy Task Force ....5-5 

5.4.3 Government Accounting Office Reports ................................................. 5-5 

5.4.4 Presidential Initiative to Develop, Implement Spectrum Policy for the 21st 

Century..................................................................................................... 5-6 

5.4.5 SAFECOM Program Office.....................................................................5-7 

5.4.6 1COMMWIRELESS (Formerly FEDSMR)............................................ 5-7 

5.4.7 Integrated Wireless Network (IWN)........................................................5-8 

5.4.8 United States Department of Defense Trunked Network ........................5-9

SECTION 6 THE SIGNAL CAPACITY ANALYSIS PROGRAM (SCAP)................. 6-1 

6.1 General..................................................................................................... 6-1 

6.2 Definition of Signal Capacity ..................................................................6-1 

6.3 Basic SCAP Analysis...............................................................................6-3 

6.3.1 Peak and Average Signal Capacity Maps ................................................ 6-4 

6.3.2 The Use of Function Codes to define Signal Capacity of Networks .......6-7 

SECTION 7 FEDERAL AGENCY SIGNAL CAPACITY MAPS ................................ 7-1 

7.1 General..................................................................................................... 7-1 

7.2 Technical parameters for Signal Capacity Maps .....................................7-1 

7.3 Interpreting the Signal Capacity Maps .................................................... 7-2 

7.4 Signal Capacity Maps for Federal Agencies............................................7-7 

7.4.1 United States Department of Agriculture (USDA)................................ 7-10 

7.4.2 United States Coast Guard (USCG).......................................................7-12 

7.4.3 United States Department of Commerce (DOC) ...................................7-14 

7.4.4 United States Department of Defense (DOD) .......................................7-16 

7.4.5 United States Department of Energy (DOE) .........................................7-18 
iii 

7.4.6 Federal Aviation Administration (FAA)................................................7-20 

7.4.7 United States Department of Interior (DOI) .......................................... 7-22 

7.4.8 United States Department of Justice (DOJ)...........................................7-24 

7.4.9 United States Capitol Police (USCP).....................................................7-26 

7.4.10 United States Postal Service (USPS) .....................................................7-28 

7.4.11 United States Department of Treasury (Treasury).................................7-30 

7.4.12 United States Department of Veteran’s Affairs (VA)............................ 7-32 

7.4.13 Other Agencies....................................................................................... 7-34 

7.4.14 All Federal Agencies..............................................................................7-36 

7.4.15 Integrated Wireless Network (IWN) (Departments of Justice, Treasury and 

Homeland Security) ...............................................................................7-38 

7.4.16 All Federal Agencies minus IWN..........................................................7-40

SECTION 8 SUMMARY OF FINDINGS ......................................................................8-1

APPENDIX A DESCRIPTION OF SIGNAL CAPACITY ANALYSIS PROGRAM A-1 

LIST OF TABLES 

Table 4-1. International and National Frequency Allocations and Footnotes for the 162-174 

MHz Band................................................................................................................4-2 

Table 4-2. Number of Frequency Assignments .............................................................4-3 

Table 4-3. Number of Frequency Assignments within a 100 Mile Radius of Washington, D.C. 

(162-174 MHz) ........................................................................................................4-5 

Table 4-4. Nationwide (US&P, USA, and US) and Statewide Assignments by Agency 

..................................................................................................................................4-9 

Table 7-1. Total Number of Assignments with Function Codes Included in SCAP ..... 7-7 

Table 7-2. Total Number of Assignments with Function Codes Not Included in SCAP Analysis

..................................................................................................................................7-8 

Table 7-3. U.S. Department of Agriculture Assignments and Function Codes..........7-11 

Table 7-4. U.S. Coast Guard Assignment and Function Codes..................................7-13 

Table 7-5. U.S. Department of Commerce Assignments and Function Codes...........7-15 

Table 7-6. U.S. Department of Defense Assignments and Function Codes...............7-17 

Table 7-7. U.S. Department of Energy Assignments and Function Codes................. 7-19 

Table 7-8. Federal Aviation Administration Assignment and Function Codes..........7-21 

Table 7-9. U.S. Department of Interior Number Assignments and Function Codes..7-23 

Table 7-10. U.S. Department of Justice Number Assignments and Function Codes ...7-25 

Table 7-11. U.S. Capitol Police Assignment and Function Codes ...............................7-27 

Table 7-12. U.S. Postal Service Assignments and Function Codes.............................. 7-29 

Table 7-13. U.S. Department of Treasury Assignments and Function Codes..............7-31 

Table 7-14. U.S. Department of Veteran’s Affairs Assignments and Function Codes 7-33 

Table 7-15. “Other Agencies” Assignments and Function Codes................................7-35 

Table 7-16. All Federal Agencies Assignments and Function Codes ..........................7-37 

Table 7-17. IWN Assignments and Function Codes .................................................... 7-39 

Table 7-18. Non-IWN Assignments and Function Codes ............................................ 7-41 

Table 8-1. Maximum Peak Signal Capacity and Included Transmitters ......................8-2 
iv 

LIST OF FIGURES 

Figure 3-1. Simplex Radio System ................................................................................. 3-1 

Figure 3-2. Repeater Architecture...................................................................................3-2 

Figure 3-3. Multi-Site Repeaters..................................................................................... 3-4 

Figure 3-4. Half-Duplex Radio System .......................................................................... 3-5 

Figure 3-5. Base Station Reception Augmented with Receive only sites.......................3-6 

Figure 3-6. Simulcast System .........................................................................................3-7 

Figure 4-1. Plot of all Agency Frequency Assignments within a 100 Mile Radius of 

Washington, D.C. in the 162-174 MHz band ..........................................................4-4 

Figure 4-2. Plot of USDA Frequency Assignments within a 100 Mile Radius of Washington, 

D.C. in the 162-174 MHz band..............................................................................4-11 

Figure 4-3. Plot of DOC Frequency Assignments within a 100 Mile Radius of Washington, 

D.C. in the 162-174 MHz band..............................................................................4-13 

Figure 4-4. Plot of USCG Frequency Assignments within a 100 Mile Radius of Washington, 

D.C. in the 162-174 MHz band..............................................................................4-14 

Figure 4-5. Plot of DOD Frequency Assignments within a 100 Mile Radius of Washington, 

D.C. in the 162-174 MHz band..............................................................................4-15 

Figure 4-6. Plot of DOE Frequency Assignments within a 100 Mile Radius of Washington, 

D.C. in the 162-174 MHz Band.............................................................................4-16 

Figure 4-7. Plot of FAA Frequency Assignments within a 100 Mile Radius of Washington, 

D.C. in the 162-174 MHz Band.............................................................................4-17 

Figure 4-8. Plot of DOI Frequency Assignments within a 100 Mile Radius of Washington, 

D.C. in the 162-174 MHz ......................................................................................4-18 

Figure 4-9. Plot of DOJ Frequency Assignments within a 100 Mile Radius of Washington, 

D.C., in the 162-174 MHz band.............................................................................4-20 

Figure 4-10. Plot of Treasury Frequency Assignments within a 100 Mile Radius of Washington, 

D.C., in the 162-174 MHz band.............................................................................4-21 

Figure 4-11. Plot of USCP Frequency Assignments within a 100 Mile Radius of Washington, 

D.C., in the 162-174 MHz Band............................................................................4-22 

Figure 4-12. Plot of USPS Frequency Assignments within a 100 Mile Radius of Washington, 

D.C., in the 162-174 MHz Band............................................................................4-24 

Figure 4-13. Plot of VA Frequency Assignments within a 100 Mile Radius of Washington, D.C. 

in the 162-174 MHz Band...................................................................................... 4-25 

Figure 4-14. Plot of Other Agency or Bureau Frequency Assignments within a 100 Mile Radius 

of Washington, D.C. in the 162-174 MHz Band. ..................................................4-26 

Figure 6-1. Peak Signal Capacity Coverage Map Examples ........................................6-4 

Figure 6-2. Average Signal Capacity Map Examples...................................................6-5 

Figure 6-3. PSC Map for Four Transmitters Analyzed as a Simulcast System............6-8 

Figure 6-4. PSC Map for Four Transmitters Analyzed as a Trunked System ..............6-8 

Figure 6-5. ASC Map for Four Transmitters Analyzed as a Simulcast radio System..6-9 

Figure 6-6. ASC Map for Four Transmitters Analyzed as a Trunked Radio System...6-9 

Figure 7-1. Peak Signal Capacity Map for Several Federal Radio Systems.................7-2 

Figure 7-2. Average Signal Capacity Map for Several Federal Radio Systems...........7-5 

Figure 7-3. Peak Signal Capacity Map for U.S. Department of Agriculture..............7-10 
v 

Figure 7-4. Average Signal Capacity Map for U.S. Department of Agriculture........7-11 

Figure 7-5. Peak Signal Capacity Map for U. S. Coast Guard ................................... 7-12 

Figure 7-6. Average Signal Capacity Map for U. S. Coast Guard..............................7-13 

Figure 7-7. Peak Signal Capacity Map for U.S. Department of Commerce...............7-14 

Figure 7-8. Average Signal Capacity Map for U.S. Department of Commerce.........7-15 

Figure 7-9. Peak Signal Capacity Map for U.S. Department of Defense ...................7-16 

Figure 7-10. Average Signal Capacity Map for U.S. Department of Defense .............7-17 

Figure 7-11. Peak Signal Capacity Map for U.S. Department of Energy.....................7-18 

Figure 7-12. Average Signal Capacity for U.S. Department of Energy .......................7-19 

Figure 7-13. Peak Signal Capacity for the Federal Aviation Administration...............7-20 

Figure 7-14. Average Signal Capacity for the Federal Aviation Administration.........7-21 

Figure 7-15. Peak Signal Capacity for U.S. Department of Interior.............................7-22 

Figure 7-16. Average Signal Capacity for U.S. Department of Interior.......................7-23 

Figure 7-17. Peak Signal Capacity Map for U.S. Department of Justice .....................7-24 

Figure 7-18. Average Signal Capacity Map for U.S. Department of Justice................7-25 

Figure 7-19. Peak Signal Capacity Map for U. S. Capitol Police.................................7-26 

Figure 7-20. Average Signal Capacity Map for U. S. Capitol Police...........................7-27 

Figure 7-21. Peak Signal Capacity for U.S. Postal Service..........................................7-28 

Figure 7-22. Average Signal Capacity for U.S. Postal Service ....................................7-29 

Figure 7-23. Peak Signal Capacity for U.S. Department of Treasury ..........................7-30 

Figure 7-24. Average Signal Capacity Map for U.S. Department of Treasury ............7-31 

Figure 7-25. Peak Signal Capacity Map for U.S. Department of Veteran’s Affairs ....7-32 

Figure 7-26. Average Signal Capacity Map for U.S. Department of Veteran’s Affairs7-33 

Figure 7-27. Peak Signal Capacity Map for “Other Agencies”.................................... 7-34 

Figure 7-28. Average Signal Capacity Map for “Other Agencies” ..............................7-35 

Figure 7-29. Peak Signal Capacity map for all Federal Agencies ................................7-36 

Figure 7-30. Average Signal Capacity map for all Federal Agencies ..........................7-37 

Figure 7-31. Peak Signal Capacity Map for IWN Agencies......................................... 7-38 

Figure 7-32. Average Signal Capacity Map for IWN Agencies...................................7-39 

Figure 7-33. Peak Signal Capacity for Non-IWN Agencies.........................................7-40 

Figure 7-34. Average Signal Capacity Map for Non-IWN Agencies...........................7-41 
vi 

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vii 

GLOSSARY 

ANSI American National Standards Institute 

APCO Association of Public-Safety Communications Officials 

International 

ASC Average Signal Capacity 

ATF Bureau of Alcohol, Tobacco, and Firearms 

BLM Bureau of Land Management 

BOP Bureau of Prisons 

C3 Command, Control, and Communications 

CTCSS Continuous Tone Coded Squelch System 

DEA Drug Enforcement Administration 

DES Data Encryption Standard 

DHS United States Department of Homeland Security 

DOC United States Department of Commerce 

DOD United States Department of Defense 

DOI United States Department of the Interior 

DOJ United States Department of Justice 

DOT United States Department of Transportation 

EMC Electromagnetic Compatibility 

FAA Federal Aviation Administration 

FBI Federal Bureau of Investigation 

FCC Federal Communications Commission 

FEDSMR Federal Specialized Mobile Radio System 

FLETC Federal Law Enforcement Training Center 

GAO United States General Accounting Office 

GMF Government Master File 

GPS Global Positioning System 

IP Internet Protocol 

IRAC Interdepartment Radio Advisory Committee 

ITS Institute for Telecommunications Sciences 

IWN Integrated Wireless Network 

JSMS Joint Spectrum Management System 

kHz Kilohertz 

LMR Land Mobile Radio 

MHz Megahertz 

NIST National Institute of Standards and Technology 

NOAA National Oceanic and Atmospheric Administration 

NOI Notice of Inquiry 

NPRM Notice of Proposed Rulemaking 

NRCS National Radio Communications System 

NTIA National Telecommunications and Information 

 Administration 

NWR NOAA Weather Radio 

NWS National Weather Service 
viii 

OTAR Over-The-Air Re-keying 

PCS Personal Communications Service 

PSC Peak Signal Capacity 

R-21 Rescue 21 

RSMS Radio Spectrum Measurement System 

RO Receive Only 

SAFECOM Public Safety Communications Interoperability Program 

SC Signal Capacity 

SCAP Signal Capacity Analysis Program 

S/I Signal-to-Interference Ratio 

TIA Telecommunications Industry Association 

Treasury United States Department of the Treasury 

UHF Ultra High Frequency 

USCG United States Coast Guard 

USCP United States Capitol Police 

USDA United States Department of Agriculture 

USFS United States Forest Service 

USPP United States Park Police 

USPS United States Postal Service 

USSS United States Secret Service 

VA Department of Veteran’s Affairs 

VHF Very High Frequency 

VoIP Voice over Internet Protocol 
ix 

EXECUTIVE SUMMARY 

The National Telecommunications and Information Administration (NTIA), an agency of 

the U.S. Department of Commerce, is responsible for managing federal agency use of the radio 

spectrum. The NTIA establishes policies concerning frequency assignment, allocation and use, 

and provides the various federal departments and agencies with guidance to ensure that their 

conduct of telecommunications activities is consistent with these policies. The NTIA also serves 

under the Executive Branch as the President's principal adviser on telecommunication policies 

pertaining to the nation's economic and technological advancements and to the regulation of the 

telecommunications industry. 

Since the radio frequency spectrum is a finite natural resource, the efficient use of this 

resource must be an important goal within the government sector (federal, state and local) and 

the private/commercial telecommunications sector. Historically, the efficient use of this 

spectrum by the federal government has primarily been a process of self-policing, peer review, 

and regulatory control. As demand for spectrum has increased, NTIA and the Federal 

Communications Commission (FCC) have continued to examine policies and regulations 

regarding the efficient use of the spectrum to ensure that there will be adequate spectrum for 

growth of existing services and available spectrum for new services. 

There are various methods to improve the spectrum efficiency of mobile radio systems

used by federal agencies. These methods include decreasing bandwidth, increasing geographical 

frequency reuse, increasing the number of users on a given frequency, and using trunked radio 

systems, among others. The federal government has expended considerable effort in the past to 

ensure that its use of the spectrum is as technically efficient as practicable by adopting various 

spectrum efficient technologies such as narrowbanding, sharing, overlaying, and applying more 

realistic spectrum distribution, analytical, and planning techniques. Although these methods are 

well-known in the federal land mobile user community and NTIA has encouraged their adoption, 

agencies have not applied them widely, since the methods also have substantial disadvantages. 

In most cases, the disadvantage is a higher cost (e.g., the requirement to buy new equipment to 

replace older, less-efficient systems), but sometimes it includes a decrease in functionality which 

could negatively affect the agency’s ability to perform its mission. 

Therefore, an expanded “measure” for new mobile radio technologies has been 

consolidated under the title of “effectiveness.” Effectiveness includes spectrum efficiency, 

usability and cost factors. Usability factors include: equipment size and weight, power 

consumption, intelligibility, operational range, latency (i.e., delay time) between message input 

at the transmitter and message output at the receiver, interoperability with other users, 

complexity of operation, and requirements for special features like encryption and digital 

messages. 

Evaluating spectrum effectiveness often requires “comparing apples and oranges.” How 

much should a 25 percent improvement in spectrum efficiency weigh against a 60 percent 

increase in cost or a ten percent decrease in intelligibility? The effectiveness of a proposed 

change could be evaluated differently by various users who have developed their own value of 
x 

the relative benefits of various factors. Therefore, a single formula will not serve to calculate the 

relative effectiveness of a proposed change as seen by all federal users. For example, users 

competing for channels in a crowded urban environment will probably count spectrum efficiency 

as more valuable, compared to rural users, where unused spectrum is more plentiful. 

A study of effectiveness must consider broader questions about how the federal 

government is using the radio spectrum, including larger-scale structural and organizational 

changes, such as shared radio systems. Implementing a shared federal radio system would be a 

much more challenging project than switching to a more spectrum efficient radio technology. 

However, a shared federal radio system might favorably affect a large number of factors that are 

part of the “effectiveness” equation, including problems of interoperability between public safety 

agencies; spectrum efficiency; meeting the narrowbanding deadlines; improved radio capabilities 

(e.g., data, encryption, emergency capacity, greatly expanded wireless Internet systems, etc.); 

economies of scale; cost reduction; and complexity/robustness issues. 

Therefore, NTIA has embarked on a multi-phased study of spectrum efficiency and 

effectiveness within the federal government land mobile bands. The first phase of the study, 

described in this report, analyzes the present federal land mobile radio (LMR) use of the radio 

spectrum in the 162-174 MHz band within a 100-mile radius around Washington, D.C., by 

developing a quantitative model of the signal capacity (SC) of current federal use of the radio 

spectrum (described below). The second phase of the study will be based on the quantitative SC 

model results developed in the first phase and will investigate various alternatives for possible 

future federal mobile radio systems, including the possibility of radio systems shared among 

federal agencies. Phase 2 will also define the conditions under which improvements could be 

made, taking into account such elements as costs, schedules, missions, etc. Other phases of the 

overall study will review and evaluate frequency assignment techniques, equipment standards, 

and engineering practices used in the federal government. Since these additional studies will not 

be limited to the Washington, D.C. area, and the 162-174 MHz band, they will be conducted 

independently from the first two phases. 

When considering the possible advantages of replacing current radio systems with 

alternative radio system(s), spectrum users and managers must have realistic information on the 

services that current systems provide. Any proposed new system design could address many 

additional factors (e.g., projected growth, new digital services, etc.), but as a minimum, the new 

system must provide the same level of service associated with the current systems. 

The wide variety of federal mobile radio services needed to be reduced to a “lowest 

common denominator” under which all mobile services could be considered together and 

summarized in a simple way. The two most important factors in level of service are 

geographical availability of service and the number of users that can be simultaneously served. 

Other factors—like the availability of various advanced digital services – are also important, but 

at lesser level and were not considered in this analysis. The resulting signal capacity (SC) model 

counts the number of independent radio signals that could be received at a given location by a 

hypothetical mobile user and creates a map showing the number of receivable signals at various 

locations. The SC model itself is not a usable description of spectrum efficiency or 
xi 

effectiveness, though it contains an important part of the geographical functional requirements 

that alternative systems must meet. 

After considering various possible methods of obtaining a large amount of quantitative 

information on current federal mobile radio service levels, NTIA decided to calculate SC values 

by analyzing the data that is currently available in the Government Master File (GMF). When 

necessary, the existing GMF data was augmented using operational data provided by agency 

representatives. The SC Analysis Program (SCAP) processed data from the GMF, augmented 

with additional “function codes” describing each assignment, to create the SC maps used in this 

study. 

Any alternative future radio system needs to provide at least as much access to radio 

signals at each location as shown by these SC maps. The results of this modeling will help in 

quantifying the advantages and disadvantages involved in potential alternative radio system 

concepts, as well as providing insights about the best architectures and technologies to employ, 

and the circumstances under which maximum effectiveness could be achieved. 

 Ongoing federal agency initiatives are investigating the potential for substantially 

improving federal radio systems operations by moving from individual agency mobile radio 

systems to a single shared system that includes state-of-the-art technologies. For example, the 

Integrated Wireless Network (IWN) is a shared trunked system that is being jointly designed and 

built by several agencies within the U.S. Department of Justice, U.S. Department of the 

Treasury, and the U. S. Department of Homeland Security (DHS). 

This Phase 1 report contains a description of federal agencies with GMF assignments in 

the 162-174 MHz band, with emphasis on their LMR systems and their use in the Washington, 

D.C. area. It also describes many of the mobile radio technologies used by the agencies, and 

explains the SCAP algorithms used to convert the GMF data to SC maps. The overall objective 

of this portion of the study was to produce a data set and corresponding analysis as inputs to the 

Phase 2 work to design possible future federal mobile radio systems. Therefore, this initial 

report does not contain extensive recommendations or conclusions. 

This Phase 1 study identifies a wide variety of functions that federal agencies perform in 

the 162-174 MHz band in the Washington, D.C. area. These functions include law enforcement, 

transportation, natural resources management, and emergency and disaster relief. There are a 

total of 4,761 frequency assignments identified from the GMF within 100 miles of Washington, 

D.C. Of the 4,761 assignments, 2,816 do not have a local infrastructure associated with them 

(i.e. area-wide assignments). Lacking any specific transmitter location, these 2,816 assignments 

were excluded from the analysis since the SC model considers only transmitters. In addition, all 

assignments for receivers (including receive-only sites) were also excluded from the SCAP 

analysis, as were numerous special-purpose transmitters whose functions would not reasonably 

be included in a future system. The Phase 1 study considered GMF assignments as of November 

2002, which was when this study commenced. Any subsequent modified assignments related to 

the bureaus or agencies that have been incorporated into the DHS were not addressed, since the 

DHS was established after the start of this study. 
xii 

 The majority of federal LMR systems in the 162-174 MHz band use analog voice 

systems with 25 kHz channel bandwidth. Approximately half of those systems, including most 

of the rural systems that serve national parks and forests as well as less-populated land use areas, 

use a simple repeater technology to extend the range of mobile and portable radios. There is 

essentially no use of simulcast networks or trunked radio systems in this frequency band. Most 

federal use of trunked systems occurs in the 380-400 MHz and 406-420 MHz bands, where 

channel plans simplify the design of trunked systems and shared base stations. Urban use 

includes large numbers of receive-only base stations operating as voting receivers to provide for 

effective use of lower power portable radios inside buildings. However, the SCAP model 

developed for this study did not consider any aspects of receivers or the base station receiver 

networks. In addition, the SCAP model makes no distinction between various mobile 

technologies, such as wideband or narrowband, digital or analog, voice-only or advanced digital 

services, trunked or non-trunked, encrypted or un-encrypted, etc. 

The SCAP was developed for this study using a Longley-Rice terrain-based propagation 

model to predict the coverage of each appropriate transmitter in the GMF database. This 

assumes that “coverage” was defined for this report as all locations having predicted field 

strength of at least ten microvolts/meter, calculated at one-mile intervals. The coverage areas for 

each transmitter were combined into coverage areas for networks of transmitters, using different 

algorithms for different types of mobile radio technologies and architectures. Figure 1 shows an 

example of an SC map for a small number of transmitters for the U.S. Coast Guard. 

The various colors show geographic areas where between one and four different signals 

could be received by a mobile user. Maps for such networks can be combined with similar maps 

for other networks to produce SC maps for whole agencies. Individual maps for 12 of the larger 

Figure 1. Signal capacity map for U.S. Coast Guard 
xiii 

agencies are included in the report. The maps for individual agencies can also be combined to 

create maps for groups of agencies; maps for several combinations of agencies have also been 

included. The results of the SCAP model indicate there are 48 federal agencies operating in the 

100-mile radius circle from which GMF data was analyzed, using a total of 866 infrastructurebased transmitters to provide coverage to mobile/portable users. Out of the total coverage area 

for which SC results were calculated, 93 percent of the locations had coverage from at least one 

radio signal, counting the signals from all federal agencies. Ten percent of the locations had 

coverage from at least 100 independent radio signals, and approximately four percent of the 

locations had coverage from at least 200 independent radio signals. Figure 2 shows that mobile 

users at some locations near the center of Washington, D.C., could receive as many as 268 

independent signals. In practice, federal agencies typically use only the radio signals assigned to 

their own agencies, which results in far fewer available signals for most users. 

The presence of 268 independent signals in downtown Washington, D.C. can be related 

to overall levels of crowding by noting that the 162-174 MHz band contains about 960 singlefrequency channels (assuming 12.5 kHz channel spacing across 12 MHz of spectrum). However, 

most federal radio systems in this band are still using older 25-kHz channel technology (reducing 

the number of available frequencies to approximately 480). Many of the federal systems, 

including all repeater systems, require a pair of frequencies for normal operation of one channel. 

This would reduce the maximum number of independent channels to about 240. Thus, the 

presence of 268 independent signals in downtown Washington is made possible only because of 

some simplex-channel operations that require only a single frequency per channel and some 

agencies who have already switched to 12.5 kHz channel operation. This analysis shows that 

Figure 2. Peak signal capacity map for all Federal Agencies
xiv 

most of the available channels are already in use for specific functions. It does not mean that 

these assigned channels are actually carrying radio signals 100 percent of the time. Channel 

occupancy measurements by the NTIA Radio Spectrum Measurement System (RSMS) are 

planned for summer 2004. These measurements will provide detailed traffic statistics for many 

of these channels, as well as the total traffic loading that proposed future radio systems would 

need to support. 

The SC maps described above are actually called “peak signal capacity” (PSC) maps. 

The PSC maps will be accompanied by a corresponding set of “average signal capacity” (ASC) 

maps in this report. The ASC maps show information similar to the PSC maps, except that the 

ASC maps contain data on the number of independent users per square mile that could be served 

by the existing analyzed mobile radio systems. The ASC data is needed so that future alternative 

radio systems can be designed with base stations having a range of different coverage areas, 

where the required traffic carried by a given base station will scale proportionally to the coverage 

area. The Appendix of this report includes a detailed description of computing and interpreting 

ASC and PSC maps. 

The results obtained for the Phase 1 SC analysis provide a useful description of the 

coverage of current federal radio systems used in the 162-174 MHz band in the Washington, 

D.C. area. The data that is summarized in this report in the form of ASC and PSC maps and the 

channel occupancy data from the planned RSMS measurements will furnish an important part of 

the quantitative basis for the next phase of this initiative which considers the design of possible 

future shared radio systems 

In May 2003, President George W. Bush signed an Executive Memorandum to develop 

and implement a comprehensive United States Spectrum Policy for the 21st Century. The 

initiative was designed to foster economic growth, ensure national and homeland security, 

maintain U.S. global leadership in communications technology development and satisfy other 

vital U.S. needs such as public safety, scientific research, federal transportation infrastructure 

and law enforcement. The Secretary of Commerce then established a Federal Government Task 

Force and initiated a series of public meetings to address improvements in policies affecting 

spectrum use by the Federal Government, State, and local Governments, and public sector. The 

recommendations resulting from these activities were included in a two-part series of reports 

released by the Secretary of Commerce in June 2004, under the title Spectrum Policy for the 21st 

Century- The Presidents Spectrum Policy Initiative. These reports contain recommendations 

regarding the efficient use of the radio spectrum. Since the report contained within was 

underway prior to the release of the Spectrum Policy for the 21st Century- The Presidents 

Spectrum Policy Initiative, it may be necessary for NTIA to modify its activities under the policy 

initiative based on the recommendations made to the President. 
1-1

SECTION 1

INTRODUCTION 

1.1 BACKGROUND 

The National Telecommunications and Information Administration (NTIA), an agency of 

the U.S. Department of Commerce, is responsible for managing federal agency use of the radio 

spectrum. The NTIA establishes policies concerning frequency assignment, allocation and use, 

and provides the various federal departments and agencies with guidance to ensure that their 

conduct of telecommunications activities is consistent with these policies.

1 The NTIA also 

serves under the Executive Branch as the President's principal adviser on telecommunication 

policies pertaining to the nation's economic and technological advancements and to the 

regulation of the telecommunications industry.2

In support of these responsibilities, NTIA has undertaken numerous spectrum-related 

studies to: assess spectrum utilization; examine reallocating government spectrum or relocating 

federal government systems; identify existing or potential electromagnetic compatibility (EMC) 

problems between systems; provide recommendations for resolving EMC conflicts; recommend 

the changes to promote efficient and effective use of the radio spectrum; and improve the 

spectrum management process. 

Since the radio frequency spectrum is a finite natural resource, efficient use of this 

resource must be one of the primary goals of government, both within the government sector 

(i.e., federal, state and local) and within the private/commercial telecom sector. Historically, 

efficient use of this spectrum, in the federal government, has been a process of self-policing, peer 

review, and regulatory controls. As demand for spectrum has increased, NTIA and the Federal 

Communications Commission (FCC) have examined policies and regulations that require, 

promote or facilitate efficient use of the spectrum to ensure adequate spectrum resources for 

growth of existing services and available spectrum for new services. 

Spectrum efficiency is one of the cornerstones for obtaining maximum capacity from the 

limited frequency spectrum. Although spectrum efficiency can be defined in many ways, it 

remains difficult to balance theoretical efficiency with mission effectiveness, resource 

management and other important requirements. For example, the federal government uses 

mobile communications in support of congressionally mandated missions related to public safety 

and the welfare of life and property, military tactical services and operations associated with 

large, geographically dispersed organizations. Many of these services can and are being met 

through commercial service providers, where spectrum efficiency is inherently included as one 

of the aspects of a competitive market. The federal government places heavy reliance on the 

private sector in providing telecommunication service for it own use. In order to emphasize the 

 

1 National Telecommunications and Information Administration, U.S. Department of Commerce, Manual of 

Regulations and Procedures for Federal Radio Frequency Management, (May 2003 Ed.) (Revisions through 

January 2004), [hereinafter NTIA Manual], Chapter 1. 

2 Telecommunications Authorization Act of 1992 Act, 47 U.S.C. §§901-904 (2004) [hereinafter NTIA Act]. 
1-2

government’s proper role as a user, any proposal designed to provide needed telecommunication 

service, which requires the government to perform any of the “provider” functions, shall be 

adopted only if commercial service is: 

 

a. not available to the user during the time needed; 

b. not adequate from either a technical or operational standpoint; or 

c. significantly more costly. 

A non-commercial service approach is acceptable if it will result in significant savings over an 

otherwise acceptable commercial service offering.3

NTIA has an ongoing telecommunication policy regarding spectrum efficiency consistent 

with its goals to administer this resource wisely and stimulate the economic growth of the nation. 

Key national objectives are to ensure effective, efficient, and prudent use of the spectrum in the 

best interest of the nation, taking care to conserve it for uses where other means of 

communication are not available or feasible.4 In addition, the process by which NTIA manages 

the federal government’s use of the spectrum ensures that spectrum is used for the public benefit 

in support of the missions and tasks of the federal government. Although these processes stress 

efficient and effective use of the spectrum, NTIA relies heavily on each agency to implement 

similar policies and ensure that systems, in their use or by their design, are spectrum efficient. 

NTIA has not generally reviewed the details of these agency decisions, beyond a general review 

of new systems and the frequency coordination and assignment processes. The decision as to 

whether an application or technology uses too much spectrum, or why an application cannot use 

a commercial service or alternate technology that does not consume spectrum resources, is 

generally left up to the operating agency which must ensure the effectiveness of its operations. 

However, within the mobile service, specifically land mobile, NTIA has taken a more aggressive 

position regarding spectrum efficiency. 

In October 1992, Congress directed NTIA to implement a plan for federal agencies with 

existing mobile radio systems to use spectrum technologies that are at least as spectrum efficient 

and cost effective as readily available commercial mobile radio systems.5 NTIA submitted a 

plan to Congress in 1993 outlining the steps NTIA would take to ensure land mobile spectrum 

efficiency.6 The plan resulted in NTIA, with the advice of the Interdepartment Radio Advisory 

Committee (IRAC), developing policies and rules governing all users of the mobile bands 

allocated to the federal government on a primary basis. These rules included a transition to 

narrowband or equivalent technology, effectively doubling the number of channels available for 

future use. Federal agencies have been struggling through technology, budget and operational 

 

3 NTIA Manual, supra note 1, at part 2.3.3. 

4 Id., at part 2.1. 

5 NTIA Act, supra note 2, 47 U.S.C. at 903 (d)(3). 

6 National Telecommunications and Information Administration, U.S. Department of Commerce, NTIA Report 93-

300, Land Mobile Spectrum Efficiency: A Plan for Federal Government Agencies to use More Spectrum-Efficient 

Technologies (October 1993) [hereinafter NTIA Report 93-300]. 
1-3

issues in their attempts to implement these rules. One difficulty is the transition to new digital 

technology, which is not necessarily backward compatible with 25 kHz analog operations. 

A number of recent events and reports have highlighted the need to maintain a focus on 

spectrum efficiency. The results of these activities offer some insight into current thinking, 

historical references, and emerging initiatives concerning spectrum efficiency. These include, 

but are not limited to, the NTIA Spectrum Summit, the FCC Spectrum Policy Task Force, two 

General Accounting Office (GAO) reports on spectrum management, and a presidential initiative 

to move spectrum management into the twenty-first century. 

One of the common objectives expressed in these reports and events is maximizing 

spectrum efficiency, especially in the bands used for mobile communications. Many believe that 

federal government agencies have fewer mobile users per unit of spectrum than is true for 

business, state and local public safety related, or common-carrier (i.e., cellular phone and 

personal communications system (PCS)) applications. As a result, there are concerns that the 

federal agencies are not using the spectrum as efficiently as their private sector counterparts. For 

example, public safety users require high reliability and availability with frequency channels 

whose traffic loads change drastically with planned or unplanned events. As a result, since these 

operations are not in use all of the time, it could be perceived as inefficient use of the spectrum. 

In 1994, NTIA produced a report that enumerated the many well-known ways to improve 

the efficiency of mobile radio systems.7 These methods include, but are not limited to, 

decreasing bandwidth, increasing geographical frequency reuse and increasing the amount of 

time that a given frequency can be used by multiple users. The federal government has 

expended considerable effort to ensure that its use of the spectrum is efficient by adopting many 

spectrum efficient technologies including: narrowbanding, sharing, overlaying, and applying 

new spectrum planning techniques. Although these methods are well-known in the land mobile 

community and NTIA has encouraged their adoption, agencies have not applied them widely, 

because the methods may also have substantial disadvantages. Sometimes the disadvantage is a 

matter of higher cost stemming from a requirement to buy new equipment to replace older, lessefficient systems. Other possible disadvantages can include a decrease in performance or 

convenience, in addition to high cost and mission impact. 

Therefore, in this report, an important “measure” regarding new mobile radio 

technologies has been consolidated under the title of “effectiveness.” Effectiveness includes 

spectrum efficiency, usability and cost factors. Usability factors include: equipment size and 

weight, power consumption, intelligibility, operational range, latency (i.e., delay time) between 

message input at the transmitter and message output at the receiver, interoperability with other 

users, complexity of operation, and requirements for special features like encryption and digital 

messages. 

Evaluating spectrum effectiveness often requires “comparing apples and oranges.” How 

much should a 25 percent improvement in spectrum efficiency weigh against a 60 percent 

 

7 Institute for Telecommunication Sciences, National Telecommunications and Information Administration, U.S. 

Department of Commerce, NTIA Report 94-311, A Survey of Relative Spectrum Efficiency of Mobile Voice 

Communication Systems (July 1994). 
1-4

increase in cost or a ten percent decrease in intelligibility? The effectiveness of a proposed 

change could be evaluated differently by various users who have developed their own value of 

the relative benefits of various factors. Therefore, a single formula will not serve to calculate the 

relative effectiveness of a proposed change as seen by all federal users. For example, users 

competing for channels in a crowded urban environment will probably count spectrum efficiency 

as more valuable, compared to rural users, where unused spectrum is more plentiful. The 

problem however, is that rural locations do not have adequate coverage due to widely-spaced 

base stations. 

“Effectiveness” forces planners to evaluate proposed changes against a much broader and 

more complete set of criteria. Proposed changes that benefit a wider range of users are more 

likely to be adopted and implemented than those that benefit some users, but which place other 

users at a disadvantage. 

A study of effectiveness should consider broader questions about how the federal 

government is using the radio spectrum and consider whether larger-scale structural and 

organizational changes, such as shared radio systems, could improve both the technical 

efficiency and effectiveness of federal radio systems. Implementing a shared federal radio 

system would be a much more challenging project than switching to a more spectrum efficient 

radio technology. However, a large number of related factors are part of the “effectiveness” 

equation, including: large required expenditures to independently solve problems of 

interoperability between public safety agencies (e.g. the E-government Initiative on 

Interoperability. (Project SAFECOM); homeland security (e.g., the Department of Homeland 

Security (DHS) and the Integrated Wireless Network (IWN)); spectrum efficiency (e.g., meeting 

the narrowbanding deadlines); improved radio capabilities (e.g., data, encryption, emergency 

capacity, greatly expanded wireless Internet systems, etc.); and economies of scale and 

complexity arguments). 

To better understand how the federal agencies use the spectrum and how to improve the 

effectiveness of this use, NTIA has undertaken a multi-phased study of spectrum effectiveness 

within the federal government land mobile bands. The first phase of the study, described in this 

report, analyzes the present federal use of the radio spectrum in the 162-174 MHz band in the 

vicinity of Washington, D.C. by developing a quantitative model of the “signal capacity” (SC) of 

current federal use of the radio frequency spectrum. The second phase will be based on the 

quantitative model results developed in the first phase and will explore various modern radio 

system alternatives to current federal systems such as shared federal systems.8 Depending on the 

apparent overall benefits (i.e., improved effectiveness) identified by the results of this phase, one 

or more concepts may be selected for further engineering and/or eventual large-scale or smallscale implementation (e.g., costs, requirements). Phase Two will also define the conditions 

under which the improvements could be made, taking into account items such as costs, 

schedules, and missions. Additional studies of the overall initiative will consider aspects such as 

frequency reuse criteria as it relates to spectrum management and the assignment process as well 

as spectrum standards to improve spectrum effectiveness. These additional studies will be 

conducted concurrently with Phase Two. 

 

8 The second phase of this study is on-going. 
1-5

1.2 SCOPE OF WORK 

1.2.1 Overall Objective 

The objective is to conduct a multi-phased study of spectrum effectiveness and 

efficiency, within a federal government land mobile band. This effect will determine the 

improvements or changes that could be made through technologies, frequency coordination and 

assignment practices, standards, policies, and reorganization of communication architectures and 

organizations that would increase the effectiveness of spectrum use and spectrum efficiency to 

satisfy the future spectrum requirements of the federal government. 

1.2.2 Specific Objectives 

Phase 1: 

a. Gather and develop information on current federal government land mobile requirements 

within the 162-174 MHz band within 100 miles of Washington, D.C. including: 

y frequency assignments in the Government Master File (GMF); 

y the type of radio communication networks (trunked, conventional, etc.); 

y the equipment characteristics (power, bandwidth, nature of and quantity of 

information transfer, etc.); 

y nature of mission, technical and operating requirements for each federal agency 

(voice, data, availability required, priority, etc.); 

y future plans and spectrum requirements; and 

y measure of SC of current federal mobile radio systems via development of a 

quantitative model. 

b. Calculate SC results of current federal mobile radio systems, using the information 

obtained in (a). 

Proposed Phase 2: 

y The NTIA Radio Spectrum Measurement System (RSMS) will make channel 

occupancy measurements for federal radio systems in the 162-174 MHz band during 

summer 2004. These measurements will be used to “calibrate” the geographical SC 

maps produced in Phase 1, producing similar maps expressed in Erlang per hour 

mobile radio traffic statistics. 

y Based on the quantitative SC results developed in Phase 1 and calibrated with RSMS 

traffic measurements, explore various modern radio system alternatives to the current 

federal systems. 

y Define the conditions under which the improvements could be made taking into 

account items such as costs, schedule of transition and mission. 
1-6

Other Related Work 

Other tasks will include: 

a. Review and evaluate the techniques, engineering practices, and related policies used in 

assigning spectrum for federal land mobile use, identifying and characterizing the various 

engineering techniques and procedures used in assigning spectrum for land mobile use; 

the improvements that could be made to these techniques and procedures to minimize 

spectrum use and maximize efficiency; and the changes required to the policy, 

procedures, and technical engineering (e.g., NTIA Manual, allotment strategies, standards 

and assignment nomination models (such as Spectrum XXI), Annex I (Procedure for 

Evaluating Frequency Proposals), Joint Spectrum Management System) necessary to 

make use of the spectrum more efficient and effective; 

b. Review of ongoing industry work in the area of land mobile standards to determine if the 

emission masks and receiver performance standards in Chapter 5 of the NTIA Manual 

need to be updated. 
2-1

SECTION 2

PHASE 1 OVERVIEW 

2.1 GENERAL 

When considering the possible advantages of replacing current smaller individual-agency 

radio systems with alternative future larger shared federal mobile radio system(s), spectrum users 

and managers must have realistic information on the services provided by the current systems. 

This information serves as a starting point for the design of any new system. Any system 

proposed to meet spectrum efficiency requirements must provide at least as much service as the 

existing systems and meet the mission requirements of the agencies. Any proposed alternative 

system may include many additional factors (e.g., projected growth), but as a minimum, 

spectrum users and managers must ensure these systems are designed with an awareness of what 

levels of service are provided by current systems. Otherwise, they cannot determine if any future 

alternative system would provide equivalent service. 

The first phase of this study provides quantitative information on current system 

operations. Many advanced radio systems provide relative advantages or disadvantages that 

depend substantially on certain economy of scale factors. This is especially true for trunked 

radio systems, but such results affect many aspects of calculating peak loading factors. To 

compare future alternative systems with current systems, some basic parameters must be known, 

such as how many channels are required for current systems. The following provides an 

overview of the Phase 1 study, including the information required on current radio systems. 

First, to develop a signal capacity analysis program (SCAP), NTIA sought to understand 

the mobile radio technologies currently being used by federal agencies. This SCAP includes SC 

algorithms to accurately analyze all of the pertinent radio technologies and architectures whose 

function could be included in future shared systems. Equally important was to identify the radio 

technologies or functions that could not be reasonably analyzed with the SCAP or included 

within future shared systems. The services of these systems will need to continue to be provided 

separate from the SCAP model and future shared systems. Typical LMR technologies used by 

federal agencies are described in Section 3. 

In addition to understanding the current radio technologies and architectures, the current 

agency missions and specific operational requirements must be understood to supplement the 

data used in the SCAP. For example, the SCAP specifically does not include any information on 

receivers or the need to use multiple receive-only sites. Similarly, the SCAP contains no 

information on agency requirements for encryption, nationwide coverage, advanced data 

services. However, all of those factors will be needed as auxiliary specifications in order to 

design future systems. Therefore, NTIA identified and summarized current agency operations 

and special characteristics needed to support those operations. Section 4 includes this summary 

of current agency operations and activities. 

Previous and ongoing federal studies and programs have mandated or have encouraged 

certain technologies and incentives promoting spectrum efficiency requirements to be used by 
2-2

various federal or non-federal public safety systems in many radio bands. Section 5 summarizes 

these various programs. 

The concept of the SCAP is discussed in more detail in Section 6. Section 7 provides the 

SC results for each federal agency and for certain combinations of federal agencies. Section 8 

provides a summary of the findings. The Appendix provides more specific details of the SCAP. 

2.2 CONCEPT OF THE SIGNAL CAPACITY ANALYSIS PROGRAM (SCAP) 

To study the current level of service that exists for federal radio systems, NTIA needed to 

reduce a wide variety of federal mobile radio services to a “lowest common denominator” under 

which all mobile services could be considered together and summarized. The SCAP counts the 

number of independent radio signals that could be received by a mobile user at a given location, 

summarizing these results in a map of SC for locations in the Washington, D.C. area. Any 

alternative future radio system then will need to provide at least as many radio signals to a 

mobile user at any location on the map as the current system does. This model should help to 

quantify the advantages and disadvantages involved in future radio system reorganization, as 

well as provide insights into the best architectures and technologies to be employed and the 

circumstances under which maximum effectiveness would be achieved. Ongoing federal agency 

programs (i.e., IWN) are investigating the potential of federal radio systems operations being 

substantially improved by moving from individual-agency mobile radio systems to single shared 

systems that include state-of-the-art technologies. 

Any model that is used to characterize the amount of service provided to federal users by 

current federal mobile radio systems in the 162-174 MHz band should reflect several 

characteristics. The model should: 1) calculate a quantity closely related to the service delivered 

to federal mobile radio users; 2) use only data available within the Government Master File 

(GMF); 3) be additive or otherwise allow easy manipulations to include different agencies or 

other user populations; 4) be transparent, in the sense that a given user can identify and verify its 

own contribution to the total results; 5) allow easy determination of anticipated results from 

prototype or proposed alternative radio systems, to facilitate comparisons between existing and 

alternative systems; and 6) require a minimum number of assumptions that could drastically 

change the model results. 

The SCAP developed for this study is appropriate for estimating the amount of service 

currently used by the federal agencies. In its simplest form, the SCAP assumes that most federal 

radio users operate in a mobile or portable environment and depend on a two-way voice channel 

created by a federally-owned base station. Therefore, service can be quantified by merely 

counting the number of independent voice channels available at any given geographical location, 

assuming that “available” means sufficient base station signal field strength to be received by a 

typical portable LMR radio. The presence of an available signal transmitted by a base station 

means that the base station will also have a receiver that is suitable to receive a signal transmitted 

by the mobile unit. The model, however, only counts the number of signals that the 

mobile/portable unit can receive. Section 6 provides a more detailed description of the SCAP. 
2-3

2.3 SELECTION OF 162-174 MHZ BAND IN THE WASHINGTON, D.C. AREA 

The 162-174 MHz band was selected for this study because this is the major band used 

for federal land mobile radio. The Washington, D.C. area was chosen because of the high 

concentration of federal users. Selection of the frequency band in the Washington, D.C. area 

provides an opportunity to: 1) investigate spectrum efficiency solutions in areas where those 

solutions are needed most; 2) realize economic savings due to economies of scale associated with 

potential solutions; 3) test solutions delivering required advanced technology capabilities like 

encryption and new digital services; and 4) consider a territory with maximum familiarity on the 

part of federal spectrum management personnel. The initial choice to include only the 162-174 

MHz band was intended to minimize the effort required to obtain initial results. 

2.4 SOURCES OF CURRENT USAGE DATA 

To support the development of the SCAP, NTIA considered various methods for 

obtaining the information needed to estimate the level of services for current systems. For 

example, a detailed survey could be submitted to federal users to obtain their estimates of current 

and projected levels of service from their radio networks. However, a survey of this type would 

be difficult and time consuming for many of the agencies, since agencies may have to survey 

each independent bureau and coordinate the results. Furthermore, the individual agencies would 

each have had to develop suitable models to describe their own current levels of service, and 

NTIA would then have to convert the results of those models to a common overall model. 

Another method would be using the NTIA/Institute for Telecommunication Sciences 

(ITS) Radio Spectrum Measurement System (RSMS) to conduct measurements within the 

Washington, D.C. area to determine the actual measured traffic occupancy for all frequencies in 

the band. A major concern with the RSMS data would be the time required to make and analyze 

such measurements at many sites over a wide geographical area. Measuring low power and 

intermittent applications would further complicate the measurements and the interpretation of 

their results. Furthermore, it would probably not be possible to collect and accurately interpret 

information on multi-site systems using the same frequencies. 

The GMF is another possible source of information. It contains records of the 

frequencies assigned to all federal government agencies in the United States. Although the 

information contained in the GMF is somewhat limited, it provides information on federal radios 

over a wide geographic range. 

After considering various possible methods of obtaining quantitative information on 

current federal mobile radio service levels, NTIA decided to estimate current levels of service by 

analyzing the data that is already available in the GMF, using computer modeling to generate 

maps showing SC. When necessary, the existing GMF data would be augmented using 

additional operational data provided by agency representatives. 

To obtain the additional data on agency operations, an informal IRAC committee was 

established to assist NTIA personnel in understanding some of the technical details of agency 

systems operating in the 162-174 MHz band within the vicinity of the Washington, D.C. area. 
2-4

 Page 2-4/Blank 

 

 

 
3-1

SECTION 3

CHARACTERISTICS OF MOBILE RADIO SYSTEMS 

3.1 GENERAL 

Many types of radio technologies are represented in the mix of LMR systems used by 

federal agencies in the 162-174 MHz band. These various radio technologies described in this 

section are to: 1) provide an understanding of the differences among the various technologies; 2) 

understand the specific algorithms used to incorporate each of these technologies into the SCAP; 

and 3) determine whether there are system features that cannot easily be incorporated in the 

SCAP. 

3.1.1 Simplex Radio Systems 

A simplex radio system is most likely the simplest type of radio system, as well as being 

the first type of system that was widely used by radio users. In simplex systems, the user 

transmits and receives on the same frequency. Figure 3-1 shows a typical simplex radio system, 

composed of various mobile radio users, M1-M6, and a base station, B. A typical user listens to 

the traffic, if any, transmitted by the other users, and the base station, as shown in Figure 3-1A. 

If a given mobile user wants to talk with any, or all, of the other users, the user waits until no 

other user is speaking, then presses the “push-to-talk” button on the microphone and talks. This 

causes the radio to shift from “receive” mode to “transmit” mode, and the transmitted signal is 

received by the other radios tuned to that frequency (e.g., M5 is shown transmitting in Figure 3-

1B). 

Figure 3-1. Simplex Radio System 
3-2

Within a simplex radio system base stations are functionally equal to any of the mobile 

stations, except that base stations are in fixed locations, and they typically have more transmitter 

power and a more advantageously-placed antenna (e.g., at the top of a high tower near the 

communications center). This often gives a high-power, high-elevation base station the ability to 

“talk” further than typical low-power, low elevation mobile stations. 

The situation is generally worse for communications between mobile users, where both 

the receiving and transmitting locations are lower and the radio paths between them are much 

more likely to be blocked by terrain and other obstacles. In Figure 3-1B, the signal from M5 is 

shown to not be received by M3, possibly because of terrain blockage between M3 and M5, or by 

M1, possibly because of excessive distance. Thus, the number of users that can participate in a 

conversation may depend greatly on the location of the specific user that is transmitting. This 

situation can cause various problems. For example, in Figure 3-1B, M3 and M5 may be 

transmitting at the same time, each unaware that their messages are interfering with each other in 

the receivers of other listeners. A given mobile talker may not know whether the transmitted 

message has been received by another mobile listener. A critical mobile-to-mobile message may 

need to be relayed to a distant mobile user by the base station or by an intervening mobile user. 

3.1.2 Radio Repeater Systems 

Repeater architecture, shown in Figure 3-2, is used especially to solve some of the 

problems associated with the limited and variable mobile-to-mobile communications range that 

is inherent in the simplex system. The high tower or mountaintop base station is called a 

“repeater” and is labeled with an “R” in Figure 3-2. There are two major changes from the 

simplex architecture. First, the repeater, unlike the base station, does not originate or terminate 

any messages. Second, the repeater continuously listens on frequency F2, (dashed blue arrow), 

and simultaneously transmits whatever it receives on a second frequency, F1, (solid red arrow). 

The mobile units use the same two frequencies reversed in function, (i.e. mobile units 

continuously listen on F1 and occasionally transmit on the frequency, F2). 

Figure 3-2. Repeater Architecture
3-3

At a given instant (e.g., when mobile user M5 is transmitting on F2), the other users, 

shown in Figure 3-2(A) are listening on frequency F1. These mobile users hear the signal on F1

that was originally transmitted at F2 from M5 and re-transmitted by the repeater at F1. The 

important feature of the repeater architecture is that the ability of mobile users to communicate 

with each other depends entirely on how well the mobile users communicate with the repeater, 

instead of the often problematic direct path between mobile users. 

Since the repeater site is typically chosen to provide low-path-loss propagation to a large 

geographic area, the usable mobile-to-repeater coverage is much greater than typical mobile-tomobile coverage. Therefore, even though an intervening hill might prevent M3 from hearing M5

directly, they can communicate via the hilltop repeater site. 

A primary user (e.g., a dispatcher at M3) does not need to connect directly to the repeater 

site, but only needs radio contact with the repeater site, like any of the mobile users. This 

encourages placement of the repeater site on the top of a distant high tower or mountaintop, 

rather than being constrained to being close to the physical location of the communications 

center (e.g., downtown). 

The use of separate transmit and receive frequencies for mobile users also solves a major 

equipment design problem, since mobile radios can be built with the assumption that all possible 

receive frequencies will be in one frequency band segment, while all possible transmit 

frequencies will be in a separate band segment. This simplifies the design of the radios, while 

permitting greater flexibility in tuning among many possible frequency channels. Simplex radios 

cannot depend on those critical design simplifications and traditionally have only a few channels 

of operation. 

3.1.3 Mobile Talk-Around Mode 

One disadvantage of the repeater architecture is that all communications must pass 

through the repeater. If the repeater site malfunctions or if mobile units drive out of range of the 

repeater site, communications will cease, no matter how close together the mobile units may be 

to one another. There are various methods of solving these problems. For example, in some 

systems it may be practical to switch to a “talk around” mode where closely-spaced mobile users 

switch to a simplex mode and communicate directly with each other using frequency F2,

independent of the base or repeater station. Although such talk-around operation has all of the 

range limitations associated with mobile-mobile simplex operations, it provides a very useful 

alternative mode that often extends the useful range of operations outside the normal repeater 

range. 

3.1.4 Multi-Site Repeater Systems 

The coverage area served by a single repeater site can be increased by using multiple 

repeater sites. A two site example is shown in Figure 3-3. A signal will be repeated by repeater 

R1 if the mobile unit is within range of repeater R1 or by repeater R2 if the mobile transmitter is 

within range of repeater R2. Unfortunately, if a mobile unit is within range of both R1 and R2

(e.g., M5 in the figure), a signal will be transmitted by both R1 and R2. Simultaneous R1 and R2
3-4

signals that are received at about the same signal strength and frequency by any mobile users 

(e.g., M1 and M6 in the figure) can cause interference, which prevents the signal from being 

properly received. A discussion of simulcast systems, which are specially designed to prevent 

this problem, is included in the later paragraphs. However, some multiple repeater systems 

attempt to negate this problem, by locating/adjusting repeaters so they cause a minimum amount 

of such interference. 

Figure 3-3. Multi-Site Repeaters

One way to avoid this interference problem is to use different transmit frequencies at the 

repeater sites. Unfortunately, this solution also requires that the mobile users adjust their 

receiver frequencies to match the transmitted frequency of the local repeater site. This adds 

some inconvenience for a mobile user. Another way to avoid simulcast interference is to add a 

continuous tone-coded squelch system (CTCSS) signal to the mobile voice transmission. The 

various codes that can be transmitted by CTCSS can be used to “activate” individual repeater 

sites, so that only the selected site is caused to repeat the message. The user would have several 

selectable channels on the mobile radio, which all used identical frequencies but transmitted 

different CTCSS codes. By selecting a particular channel, the user can select which repeater site 

to activate. 

The use of different repeater transmitter frequencies, versus the use of activating different 

sites with CTCSS codes, gives various operational advantages and disadvantages. The use of 

CTCSS codes allows mobile users to operate everywhere using the same pair of frequencies. 

This means that mobile users do not need to continually switch frequencies depending on their 

location relative to the various repeater sites. The use of CTCSS also requires many fewer 

frequencies. However, if the repeater sites are used individually (i.e., if an incoming mobile 

message received at one site is not simultaneously repeated from all sites), the use of individual 

repeater transmit frequencies may allow more independent messages to be repeated from a set of 

repeater sites. 

3.1.5 Half-Duplex Radio Systems 

The half-duplex architecture combines elements of the simplex and the repeater 

architectures, as shown in Figure 3-4. As with the simplex system technology, half-duplex 

technology has a base station talking to multiple mobile users and receiving signals from these 

users. Like the repeater system, a half-duplex system transmits messages from the base station 

to the mobile users, Figure 3-4(A), at one frequency, F1, (solid red line) and receives messages, 

Figure 3-4(B), from mobile users at another frequency, F2, (dashed blue line). The primary 
3-5

functional difference between half-duplex and repeater architectures is that half-duplex base 

stations are directly linked to fixed communications networks, dispatchers, or a command center 

with wire-line or radio links. 

Figure 3-4. Half-Duplex Radio System

From a functional point of view, most half-duplex system messages originate or 

terminate at the base station, whereas all repeater messages originate and terminate at a distant 

mobile user. Since half-duplex system messages usually originate at the base station, mobile-tobase frequency F2 and base-to-mobile frequency F1 do not necessarily have to simultaneously 

transmit the same information, which allows some additional useful modes of operation. 

Messages can be sent from the base station to mobile users, with no activity in the mobile-tobase channel, Figure 3-4(A). Messages sent from the mobile users can be directed toward only 

the base station listeners (Figure 3-4(B)) or they can also be simultaneously re-transmitted to all 

users on frequency F1 (Figure 3-4(C)) like a repeater system. So-called “full-duplex” capabilities 

simultaneously use F1 and F2 to provide full-time two-way voice communications, without the 

need for a push-to-transmit control (i.e., cell phone systems are full-duplex). A full-duplex 

capability also provides the ability for a mobile user to transmit a message to the dispatcher, 

without waiting for the end of an ongoing message from the dispatcher. However, many 

portable/mobile radios do not have the ability to simultaneously transmit and receive, so these 

radios could not provide full-duplex operation. 

3.1.6 Multi-Site Duplex Systems 

Duplex systems tend to be used for some large and high priority systems (i.e., the Federal 

Aviation Administration’s (FAA) National Radio Communications System (NRCS)). Multiple 

duplex base stations can be combined together into networks, providing a coverage area that 

represents the cumulative coverage area of the multiple individual base stations. Large multi-site 

duplex systems often have the ability for the user to enter the system at any base station site to 

gain access to a dispatcher at a communications center, to connect to the telephone system, or 

connect to another base station coverage area at a distant location. Although multi-site systems 

can provide a wide range of services and coverage area, they often also require a high degree of 

user knowledge and attention. For example, each base station will use different frequencies, and 

the user must continually change transmit and receive frequencies when moving from the 

coverage area of one site to another site. Similarly, a user might contact a distant user by using a 

distant base station to provide the needed radio link; however, this could only be accomplished if 

the current location of the distant user was known so that the correct base station could be 

selected. 
3-6

Although a simplex channel provides two-way voice service using only half as many 

frequencies needed by a duplex system, the duplex architectures have some substantial 

advantages over simplex radios. The main reason is that, although simplex radios operate well 

by themselves for many purposes, they do not operate well within groups of other similar radios. 

A simplex radio transceiver must be able to receive at the same frequency that it transmits. A 

group of simplex transceivers (e.g., at a base station shared with 20 other simplex channel users) 

would need to have the ability to receive a signal simultaneously with 20 other users transmitting 

on the same antenna tower at nearby frequencies. This turns out to be extremely difficult from a 

technological basis. Even one nearby (in frequency and location) transmitter will overload the 

receiver front-end circuits and prevent reception, and combinations of transmitters will generate 

interfering intermodulation products at many unintended frequencies. Thus, sharing base station 

facilities with large numbers of other transmitters is difficult using simplex technology. 

Duplex technology uses different frequency band segments for mobile and base station 

transmitters (e.g., the lower half of an LMR band is used for mobile transmitters and the upper 

half of the band is used for base station transmitters, with a fixed frequency separation between 

the corresponding base and mobile paired frequencies). This greatly simplifies the construction 

of radio transceivers and allows much easier sharing of base station sites. Repeating the earlier 

scenario of sharing a base station with 20 other radio systems means the 20 other transmitters are 

now all in a different frequency band from that used by the receiver, and there are far fewer 

restrictions on how the base station can be shared. It is much easier to construct receivers and 

transmitters that can tune across a whole band with hundreds of different frequency pairs 

(channels). Moreover, this easy sharing and channel flexibility extends to ad hoc mixtures of 

radios, such as might occur when multiple agencies deploy their systems in the vicinity of any 

major emergency. When the overall usefulness of simplex and duplex systems is considered, the 

greater freedom to use arbitrary duplex channels for many operational situations is often more 

important than the implicit efficiency of the single duplex channel in isolated circumstances. 

3.1.7 Receive-Only Sites 

Duplex systems may, like repeater systems, have 

substantial problems with unequal effective operational 

ranges for mobile and portable radios versus the base 

station site. In many systems where reception is required 

for portable radios, especially for portable radios 

operating inside buildings, the problem of unequal range 

is solved by adding “receive-only” (RO) base stations as 

shown in Figure 3-5. 

These additional RO base stations are located so 

that a base station receiver is always within the 

transmitting range of even lower power portable radios. 

Typically, the received audio from each of the 

receiver sites, RO and two-way, are transferred to a 

central point (e.g., the dispatcher or the associated 

Figure 3-5. Base Station Reception Augmented 

with Receive-only Sites 
3-7

full-function base station) and the “best quality” received signal is selected as the only received 

signal. 

3.1.8 Simulcast Radio Systems 

When it is necessary to provide coverage over a larger geographical area than can be 

covered from a single base station, simulcasting can be a more convenient way to combine the 

coverage area of multiple base stations, as shown in Figure 3-6. Simulcast base stations use a 

duplex frequency plan at each site, but the same frequency pair, the same transmit frequency 

(solid red lines), and the same receive frequency (dashed blue line), is used at all sites. Unlike 

multi-site duplex systems described earlier, simulcast systems allow a mobile user to operate 

with a uniform pair of transmit and receive frequencies over the entire coverage area. The three 

circles in Figure 3-6 show nominal coverage areas for each of the three simulcast base stations. 

As shown in Figure 3-6, the set of simulcasting sites typically produce some overlapping 

coverage areas where a given receiver, e.g., M3, could receive approximately equal usable levels 

of signal from more than one base station site. To prevent these multiple signals from interfering 

with each other, the relative frequencies and time delays of these signals must be precisely 

controlled. This is accomplished by synchronizing frequencies transmitted at all sites and 

uniformly delaying the transmission of signals at each site to compensate for the relative time 

delays incurred in transporting the signal to each transmitter site. In the past, it was quite 

difficult to synchronize the frequencies, but now it is relatively simple to use Global Positioning 

System (GPS) signals from satellites to synchronize clocks and frequency sources at multiple 

sites. 

Figure 3-6. Simulcast System 

Simulcast systems also allow a single frequency, paired with the base transmitter 

frequency, to be used for mobile transmitters sending messages to the simulcast base stations. 

Typically, the signals received by each base station are all sent back to the simulcast 

communications center, where they are compared and the best signal is sent to the dispatcher, 

similar to multiple receive-only sites. As with other duplex radio systems, any messages 

received from mobile users may, or may not, be simultaneously re-transmitted to the rest of the 

mobile users. 
3-8

Thus, simulcast systems can provide very convenient duplex radio services over a much 

larger multi-site coverage area, using a single pair of base station transmit and receive 

frequencies. The simulcast system allows a simple mobile radio to be used across the full 

geographical coverage area without needing to switch frequencies or make other adjustments. 

3.1.9 Trunked Radio Systems 

When there are a large number of users concentrated in a given area (i.e., urban), and 

frequency resources are limited, trunked radio systems are a particularly useful type of halfduplex radio system. The half-duplex systems concepts demonstrated in figure 3-4 also applies 

to trunked radio systems. In trunked radio systems, multiple half-duplex radio channels are 

available, but none of them are permanently associated with a given user or function. Instead, 

the trunked system temporarily designates an arbitrary channel for a given user message at the 

instant that the user requests a radio channel. The only criterion for choosing a particular 

channel is that the channel is currently available (i.e., not being used by any other user) at the 

time when the user requests a channel. 

The appeal of trunked radio systems is that each channel of a trunked radio system can 

carry considerably more traffic than a similar channel on a conventional radio system, with no 

apparent user awareness of the presence of the other users. If “User A” were sharing a channel 

with other users on a conventional radio system, User A would be blocked from service if any of 

the other users were currently talking on the shared channel. For example, if the other users kept 

the channel busy for 20 percent of the time, User A should expect to find the channel unavailable 

for use 20 percent of the time. If User A needed immediate access to a radio channel at all times, 

this could be accomplished only by sharing his channel with no other users (or perhaps only a 

very few users). However, if User A were sharing channels on a trunked radio system having ten 

channels, for example, where other users kept all of the channels in use for 20 percent of the 

time, the blocking situation is much different. Since User A can be given any one of the ten 

channels, User A will be blocked only if all ten channels are simultaneously in use. The 

probability of all ten channels being used is much smaller than the probability that a single “User 

A” channel is in use. Therefore, each trunked system channel can carry much more traffic on 

average before User A will typically have to wait until other users stop talking. 

Another capability of trunked radio systems is the ability to divide users into various 

“talk groups.” These talk groups determine which users receive which messages. In general, 

each user belonging to a specific talk group hears the messages addressed to that talk group and 

transmits messages to the other members of that talk group. This feature allows the trunked 

radio system to divide its many users into various independent talk groups that match the 

functional groupings by which agency missions are accomplished. Additionally, existing talk 

groups can be rapidly modified to allow the talk group structures to adapt to new situations, such 

as major events or emergencies that require new cross-agency interoperability and command 

structures. 

Trunked systems become particularly flexible and more powerful when multiple trunked 

sites are assembled into networks of trunked systems. Such networks are quite complex and 

expensive, but they can have considerable advantages over single-site trunked radio systems. 
3-9

However, to provide these services, the capabilities of the individual trunked base 

stations must be combined into a system using inter-site connections, which are often broadband 

wireline or point-to-point microwave, and controlled with complex computer/controllers. For 

example, when a radio user within the coverage area of one site calls a talk group that is spread 

across the coverage areas of multiple sites, the required communications can be provided only by 

the unified network. Among various data that the network requires, for example, is the 

approximate current location of each talk group member, so that calls can be sent out via all of 

the required base stations. In addition, the network must know the current talk groups for each 

user, user radio capabilities, authorization, and encryption data. This information must be 

updated whenever a radio user moves from one base station coverage area to another, turns their 

radio off or if it moves temporarily out of range. 

The ability of the intelligent network to connect the sites is important since the network 

intelligence is what converts individual base station capabilities to a system having statewide, 

nationwide, or possibly even worldwide, coverage with a wide range of techniques to adapt to 

highly variable communications needs. There are also issues about the reliability and robustness 

of the network connecting the sites as well as the ability of base stations to continue critical 

operations if the network connections are severed. Since all traffic has to move through the base 

station sites, a failure of the links connecting a site to the control network could render the 

system completely inoperable. In some systems, the base stations have independent local 

operation software that allows them to act as stand-alone trunked repeaters if the connections to 

the network fail. This allows a partial set of communications capabilities to continue 

functioning, though it could not provide capabilities that depend on interconnection to the other 

elements of the network.

3.2 SUMMARY 

The federal agencies currently operate various types of mobile radio systems. Most of 

these systems incorporate the techniques described previously in this section. These descriptions 

are useful in understanding the current operations of the various federal agencies that are 

described in Section 4 and in understanding the SC algorithms described in Section 6 or in 

Appendix A. 
3-10

Page 3-10/Blank 
4-1

SECTION 4

FEDERAL OPERATIONS IN THE 162-174 MHZ BAND 

4.1 GENERAL 

The federal government accommodates non-tactical land mobile operations in the 162-174 

MHz and 406.1-420 MHz bands. These two bands are the most widely used by the federal 

agencies. Forty-eight federal agencies are authorized to operate in the 162-174 MHz band, 

which makes it one of the bands most heavily licensed by the federal government. 9 The 

following section provides a summary of the 162-174 MHz band in terms of allocation usage as 

well as operational descriptions of the federal agencies’ usage in the Washington, D.C. area as of 

November 2002, when the study was initiated. The Department of Homeland Security (DHS) is 

not included because the department was not established until March 2003.10

4.2 ALLOCATION 

The NTIA Manual contains the international and national allocations and footnotes, as 

shown in Table 4-1, for the 162-174 MHz band. The 162-174 MHz band is allocated on a coprimary basis with the fixed service, and this band is used for fixed systems in addition to mobile 

systems, including fixed point-to-point, fixed point-to-multipoint, maritime, and aeronautical 

mobile systems.11 Thus, federal land mobile operations are shared with other federal government 

services in this band and for this study. The SC analysis and results are derived from only the 

land mobile services. 

 

9 National Telecommunications and Information Administration, U.S. Department of Commerce, NTIA Special 

Publication 01-48, Alternative Frequencies for Use by Public Safety Systems: Response to Title XVII, Section 1705 

or the National Defense Authorization Act for FY 2001 (December 2001), [Hereinafter NTIA Special Publication 

01-48], at 2-5. 

10 The spectrum assignments that were utilized by the agencies prior to their transition to the DHS, were, for the 

most part, reassigned to the DHS. See, Pub. L. No. 107-296 (2002). 

11 See supra note 9, at 3-1. 
4-2

Table 4-1. International and National Frequency Allocations and Footnotes for the 162-174 MHz Band 

162-174 MHz 

International Table United States Table Remarks 

Region 1 Region 2 Region 3 Federal Government Non-Federal 

Government 

162.0125-173.2 

FIXED 

MOBILE 

5.226 US8 US11 

US13 US216 US223 

US300 US312 

G5 

162.0125-173.2 

5.226 US8 US11 

US13 US216 US223 

US300 US312 

Auxiliary 

Broadcasting 

(74) 

Private Land 

Mobile (90) 

173.2-173.4 173.2-173.4 

FIXED 

Land mobile 

Private Land 

Mobile (90) 

156.8375-174 

FIXED 

MOBILE except 

aeronautical mobile 

5.226 5.229 

156.8375-174 

FIXED 

MOBILE 

5.226 5.230 5.231 5.232 

173.4-174 

FIXED 

MOBILE 

G5 

173.4-174 

Footnotes Applicable to the Federal Government

5.226 – The frequency 156.8 MHz is the international distress, safety and calling frequency for the maritime mobile VHF 

radiotelephone service. 

US8 – The use of frequencies 170.475, 171.425, 171.575 and 172.275 MHz east of the Mississippi River, and 170.425, 170.575, 

171.475, 172.225 and 172.373 MHz west of the Mississippi River may be authorized for fixed, land and mobile stations operated 

by non-federal forest firefighting agencies. In addition, land stations and mobile stations operated by non-federal conservation 

agencies, for mobile relay operation only, may be authorized to use the frequency 172.275 MHz east of the Mississippi River and

frequency 171.475 MHz west of the Mississippi River. The use of any of the foregoing nine frequencies shall be on the condition 

that no harmful interference will be caused to government stations. 

US11 – The use of the frequencies 166.250 and 170.150 MHz may be authorized to non-government remote pickup broadcast 

base and land mobile stations and to non-government base, fixed and land mobile stations in the public safety radio services. 

US13 – For the specific purposes of transmitting hydrological and meteorological data in cooperation with agencies of the federal 

government the following frequencies may be authorized to non-government fixed stations on the condition that harmful 

interference will not be caused to government stations: 

MHz MHz MHz MHz

169.4250 170.2250 171.0250 171.8250 

169.4375 170.2375 171.0375 171-8375 

169.4500 170.2500 171.0500 171.8500 

169.4625 170.2625 171.0625 171.8625 

169.4750 170.2750 171.0750 171.8750 

169.4875 170.2875 171.0875 171.8875 

169.5000 170.3000 171.1000 171.9000 

169.5125 170.3125 171.1125 171.9125 

169.5250 170.3250 171.1250 171.9250 

US216 - The frequencies 150.775 and 150.790, and the bands 152-152.0150, 163.2375-163.2625, 462.9375-463.1875, and 

467.9375-468.1875 MHz are authorized for government/non-government operations in medical radio communications systems. 

US300 – The frequencies 169.445, 169.505, 170.245, 170.305, 171.045, 171.105, 171.845 and 171.905 MHz are available for 

wireless microphone operations on a secondary basis to government and non-government operations. 

US312 – The frequency 173.075 MHz may also be authorized on a primary basis to non-government stations in the Police Radio 

Service (with a maximum authorized bandwidth of 20 kHz) for stolen vehicle recovery systems. 

G5 – Use by the military services is limited by the provisions specified in the channeling plans shown in Sections 4.3.7 and 4.3.9 

of the NTIA Manual. 
4-3

4.2.1 Use of the 162-174 MHz Band 

The GMF was used as the baseline to obtain agency occupancy data for this Phase 1 

study. The GMF is the U.S. Government’s database that contains a complete listing of 

government frequency assignments and is an important tool used for various spectrum 

management activities. Table 4-2 shows the GMF summary of assignments by station class per 

agency and radio service in the 162-174 MHz band as of November 2002.12 Accordingly, these 

assignments may have been revised, updated, or expanded as needed to meet changing spectrum 

management requirements. 

Table 4-2. Number of Frequency Assignments 

within a 100 Mile Radius of Washington, D.C.

Aeronautical Land Mobile Mobile Fixed Experimental 

Mobile Service Service Service Service 

TOTALS 

Agriculture 23 8 5 36 1.9% 

Commerce 12 2 168 182 9.4% 

Coast Guard 4 10 14 0.7% 

Dept. of Defense 

 Air Force 51 1 52 2.7% 

 Army 61 13 74 3.8% 

 Navy 3 9 29 41 2.1% 

Energy 39 6 45 2.3% 

FAA 41 67 108 5.6% 

Interior 125 42 85 252 13.0%

Justice 66 523 81 670 34.4%

Treasury 197 19 15 231 11.8%

US Capitol Police 25 25 1.3% 

US Postal Service 41 41 2.1% 

Veterans Affairs 30 30 1.5% 

Others 133 1 10 144 7.4% 

3 857 605 451 29 1,945 TOTALS 

0.2% 44.0% 31.1% 23.2% 1.5% 100.0%

 

Services Station Classes13

 

Aeronautical Mobile FA, FAD, FAT, MA 

Land Mobile FB, FBR, ML, MLP, MLPR, MLR 

Mobile FL, FLEC, FLR, MO, MOB, MOE, MOEB, MOEC, MOP, MOR 

Fixed FX, FXD, FXE, FXH, FXHR, FXR 

Experimental XT 

 

12 The GMF is the federal government’s master list of frequency assignments authorized by NTIA, but does not 

necessarily represent the number of pieces of radio equipment associated with each assignment. There may be many 

pieces of radio equipment associated with a single frequency assignment. In addition, the GMF utilized for this 

study does not contain any classified federal frequency assignments.

13 These station classes are defined in the NTIA Manual, supra note 1, at 6-18. 
4-4

In the 162-174 MHz band, there are 1,945 specific assignments within a 100 mile radius 

of Washington, D.C. The majority of the area-specific assignments are in the land mobile 

service (44 percent), followed by the mobile (31.1 percent), fixed (23.2 percent), experimental 

(1.5 percent) and aeronautical mobile (0.2 percent). The major users of this band are U. S. 

Department of Justice (DOJ), U. S. Department of Interior (DOI), U. S. Department of the 

Treasury (Treasury), and U. S. Department of Commerce (DOC). The location of these 

assignments is shown in Figure 4-1. Table 4-3 provides a summary count of assignments 

categorized by agency/bureau, station class and percentage of total assignments by bureau. 

There are also 2,816 area assignments in the band that can potentially be used at any given time. 

Table 4-4 shows a summary of area and statewide assignments by agency.14

Figure 4-1. Plot of All Agency Frequency Assignments within a 100 Mile Radius 

of Washington, D.C. in the 162-174 MHz Band 

 

14 Area assignments are: US&P (United States and Possessions), US (the 50 states and the District of Columbia), 

and USA (the 48 contiguous states and the District of Columbia). 
4-5

Table 4-3. Number of Frequency Assignments within a 100 Mile Radius of Washington, D.C. (162-174 MHz) 

 

Aeronautical Land Mobile Mobile Fixed Experimental

 TOTALS 

 Assignments % per Agency 

Agency/Bureau Mobile Service Service Service Service 

Agriculture 

 Animal and Plant Health 

 Inspection Service 7 2 9 25.0% 

 Agriculture Research Service 9 1 1 11 30.6% 

 Region 8 7 1 8 22.2% 

 Farm Service Agency 1 1 2.8% 

 Washington Office 2 2 5.6% 

 Office of Inspector General 4 1 5 13.9% 

TOTALS 23 8 5 36 

Commerce 

 (No Bureau) 2 2 1.1% 

 National Institute of 

 Standards and Technology 9 2 11 6.0% 

 National Weather Service 166 166 91.2% 

 Office of the Secretary 3 3 1.6% 

TOTALS 12 2 168 182 

Coast Guard 

 Coast Guard District 5 9 9 64.3% 

 Coast Guard Headquarters 

 Unit 50 1 1 7.1% 

 Coast Guard Headquarters, 

 Washington, D.C. 3 1 4 28.6% 

TOTALS 4 10 14 

Dept. of Defense 

 Air Force 

 (No Bureau) 51 1 52 100.0% 

 TOTALS 51 1 52 

 Army 

 AFMO CONUS 32 3 35 47.3% 

 Headquarters 1 1 1.4% 

 Corps of Engineers 5 5 10 13.5% 

 Military District of Washington 23 5 28 37.8% 

 TOTALS 61 13 74 

 Navy 

 (No Bureau) 3 9 29 41 90.9% 

 TOTALS 3 9 29 41 9.1% 

Energy 

 Headquarters Office 39 6 45 100.0% 

TOTALS 39 6 45 

FAA 

 (No Bureau) 5 5 4.6% 

 FAA Eastern Region 41 61 102 94.4% 

 FAA Western Pacific Region 1 1 0.9% 

TOTALS 41 67 108 
4-6

Table 4-3. Number of Frequency Assignments within a 100 Mile Radius of Washington, D.C. (Continued) 

Interior 

 Geological Survey 

 Administrative 1 1 0.4% 

 Geological Survey 

 Biological Resources Division 1 1 0.4% 

 Geological Survey 

 National Mapping Division 1 1 0.4% 

 Office of the Secretary 8 8 3.2% 

 National Park Service 

 National Capital Field Area 65 41 51 157 62.3% 

 National Park Service 

 New England Field Area 48 34 82 32.5% 

 U.S. Fish and Wildlife Service 

 CT,DE,D.C.,ME,MD,MA,NH,NY, 

 PA,RI,VT,VA,WV 

 1 1 2 0.8% 

TOTALS 125 42 85 252 

Justice 

 Bureau of Prisons 1 1 0.1% 

 Drug Enforcement Administration 3 3 0.4% 

 Federal Bureau of Investigation 53 456 62 571 85.0% 

 Immigration and Naturalization 

 Service 1 29 13 43 6.4% 

 Justice Management Division 8 8 1.2% 

 U.S. Marshals Service 4 36 6 46 6.8% 

TOTALS 66 525 81 672 

Treasury 

 Bureau of Alcohol, Tobacco 

 and Firearms 33 4 37 16.0% 

 U.S. Customs Service 21 4 1 26 11.3% 

 White House Communications 

 Agency 60 15 75 32.5% 

 Departmental Offices 3 3 1.3% 

 Bureau of Engraving and Printing 1 1 0.4% 

 Inspector General for Tax 

 Administration 10 4 14 6.1% 

 IRS Criminal Investigation Division 5 5 2.2% 

 Integrated Treasury Network 4 4 1.7% 

 U.S. Secret Service 60 6 66 28.6% 

TOTALS 197 19 15 231 

U.S. Capitol Police 

 (No Bureau) 25 25 100.0% 

TOTALS 25 25 

U.S. Postal Service

 Postal Inspection Service 13 13 31.7% 

 Mail Processing and Distribution 28 28 68.3% 

TOTALS 41 41 

Veterans Affairs 

 National Cemetery Administration 4 4 13.3% 

 VA Central Office 3 3 10.0% 

 Veterans Health Administration 23 23 76.7% 

TOTALS 30 30 
4-7

Table 4-3. Number of Frequency Assignments within a 100 Mile Radius of Washington, D.C. (Continued)

Aeronautical 

Land 

Mobile Mobile Fixed Experimental

Other Agencies & Bureaus Mobile Service Service Service Service 

 TOTALS 

 Assignments % per Agency 

Administrative Office of the

United States Courts 

 (No Bureau) 7 7 100.0% 

TOTALS 7 7 

Broadcasting Board of Governors 

 (No Bureau) 2 1 3 100.0% 

TOTALS 2 1 3 

Consumer Products Safety

Commission 

 (No Bureau) 1 1 100.0% 

TOTALS 1 1 

Environmental Protection Agency 

 (No Bureau) 4 4 100.0% 

TOTALS 4 4 

FCC 

 Field Operations Bureau 7 7 100.0% 

TOTALS 7 7 

General Services Administration 

 (No Bureau) 13 13 68.4% 

 Office of Federal Supplies 

 and Services 1 1 5.3% 

 Office of Federal Protection 

 and Safety 1 1 5.3% 

 Office of Information 

 Resources Management 1 1 5.3% 

 Public Buildings Service 3 3 15.8% 

TOTALS 19 19 

Government Printing Office 

 (No Bureau) 1 1 100.0% 

TOTALS 1 1 

Health and Human Services 

 National Institutes of Health 9 9 64.3% 

 Office of the Inspector General 1 1 7.1% 

 Substance Abuse & Mental 

 Health Administration 3 1 4 28.6% 

TOTALS 13 1 14 

House of Representatives 

 (No Bureau) 2 2 100.0% 

TOTALS 2 2 

Housing and Urban Development 

 (No Bureau) 8 8 100.0% 

TOTALS 8 8 

International Trade Commission 

 (No Bureau) 1 1 100.0% 

TOTALS 1 1 

Department of Labor 

 (No Bureau) 4 4 100.0% 

TOTALS 4 4 
4-8

Table 4-3. Number of Frequency Assignments within a 100 Mile Radius of Washington, D.C. (Continued)

National Aeronautical and Space Admin. 

 Goddard Space Flight Center 1 1 2 40.0% 

 NASA Headquarters 1 1 20.0% 

 Marshall Space Flight Center 2 2 40.0% 

TOTALS 4 1 5 

National Security Agency 

 (No Bureau) 2 2 100.0% 

TOTALS 2 2 

National Gallery of Art 

 (No Bureau) 4 4 100.0% 

TOTALS 4 4 

National Labor Relations Board 

 (No Bureau) 1 1 100.0% 

TOTALS 1 1 

Nuclear Regulatory Commission 

 (No Bureau) 3 3 100.0% 

TOTALS 3 3 

U.S. Senate 

 (No Bureau) 8 8 100.0% 

TOTALS 8 8 

Social Security Administration 

 (No Bureau) 2 2 100.0% 

TOTALS 2 2 

State Department 

 (No Bureau) 10 10 90.9% 

Office of Information 

Resource Management 1 1 9.1% 

TOTALS 11 11 

U.S. Supreme Court 

 (No Bureau) 8 3 11 100.0% 

TOTALS 8 3 11 

Smithsonian 

 (No Bureau) 13 5 18 100.0% 

TOTALS 13 5 18 

Department of Transportation 

 Office of the Secretary 8 8 100.0% 

TOTALS 8 8 

Services Station Classes 15

Aeronautical Mobile FA, FAD, FAT, MA 

Land Mobile FB, FBR, ML, MLP, MLPR, MLR 

Mobile 

FL, FLEC, FLR, MO, MOB, MOE, MOEB, MOEC, MOP, 

MOR 

Fixed FX, FXD, FXE, FXH, FXHR, FXR 

Experimental XT 

 

15 See supra note 13. 
4-9

Table 4-4. Nationwide (US&P, USA, and US) and Statewide Assignments by Agency 

Aeronautical Land Mobile Maritime Mobile Fixed 

Mobile Service Service Mobile Service Service Service 

TOTALS 

Agriculture 7 98 138 61 304 10.8% 

Commerce 27 11 30 68 2.4% 

Coast Guard 2 3 8 15 28 1.0% 

Dept. of Defense 

 Air Force 4 4 0.1% 

 Army 10 19 29 1.0% 

 Navy 3 3 0.1% 

Energy 10 59 26 17 112 4.0% 

FAA 2 12 1 2 17 0.6% 

Interior 2 51 1 1,032 170 1,256 44.6% 

Justice 2 85 279 41 407 14.5% 

Treasury 304 55 359 12.7% 

U.S. Capitol Police 2 2 0.1% 

U.S. Postal Service 30 43 73 2.6% 

Veterans Affairs 31 31 1.1% 

Others 14 92 1 11 5 123 4.4% 

37 810 5 1,561 403 2,816 TOTALS 

1.3% 28.8% 0.2% 55.4% 14.3% 100.0% 

 

 

Services Station Classes16

 

Aeronautical Mobile FA, FAD, FAT, MA 

Land Mobile FB, FBR, ML, MLP, MLPR, MLR 

Maritime Mobile FC, FCB, FCD, MS, MSD, MSP, OD, OE 

Mobile FL, FLEC, FLR, MO, MOB, MOE, MOEB, MOEC, MOP, MOR 

Fixed FX, FXD, FXE, FXH, FXHR, FXR 

 

16 See supra note 13. 
4-10

4.3 OPERATIONAL DESCRIPTION OF EACH AGENCY’S LMR OPERATIONS 

Federal agencies operating in 162-174 MHz band have various functions that include law 

enforcement, transportation, natural resource management, and emergency and disaster relief. 

How each agency achieves these functions is based on mission and operational requirements. 

Not all of the agencies’ primary missions are concentrated in urban areas. For example, the 

Departments of Interior and Agriculture are more concentrated in the rural areas where their 

missions dictate the protection and preservation of large expanses of land such as the national 

parks and forests. Therefore, some agencies or bureaus may not be listed in Table 4-3 because 

they do not have any frequency assignments in the study area. The following subsections discuss 

the general mission, current use, and future plans for each agency that has assignments in the 

162-174 MHz band within the study area. The information presented may include inputs 

provided by the various federal agencies. 

4.3.1 United States Department of Agriculture (USDA) 

The USDA’s mission is to enhance the quality of life for the American people by 

supporting production of agriculture by: ensuring a safe, affordable, nutritious, and accessible 

food supply; caring for agricultural, forest, and range lands; supporting sound development of 

rural communities; providing economic opportunities for farm and rural residents; expanding 

global markets for agricultural and forest products and services; and working to reduce hunger in 

America and throughout the world.17 The USDA has two distinct areas of operations within the 

100 mile radius around Washington, D.C., as shown in Figure 4-2. These areas are: Washington, 

D.C., for headquarters operations, and the Blue Ridge Mountain area for the U. S. Forest Service, 

each of which is described below. A list of the assignments is shown in Table 4-3. 

Headquarters 

The USDA’s Washington, D.C. area current operations consist of a series of half-duplex 

and simplex wideband (25 kHz bandwidth) analog mobiles and hand-helds with repeaters used to 

extend the range of the networks. USDA’s headquarters nets are used primarily for in-building 

security and the inspection bureau. USDA’s headquarters future communications will be 

expanding to a narrowband (12.5 kHz bandwidth) digital, multi-cast system, utilizing numerous 

CTCSS activated repeaters throughout the Washington, D.C. area. This new system will be 

Project 25/Telecommunications Industry Association 102 (P25/TIA 102) compliant and 

incorporate voice over Internet protocol (VoIP) technology.18

 

17 U.S. Department of Agriculture, Mission of USDA Agencies and Offices, at http://www.usda.gov/mission/misstoc.htm. 

18 Federal public safety agencies have engaged in a long-term standards development process known as P25/TIA 

102, a collective effort by industry and the state and local public safety agencies. This effort has resulted in the 

development of an extensive set of standards for digital public safety wireless communications. 
4-11

U.S. Forest Service 

The U.S. Forest Service is in the process of upgrading their current analog wideband 

system in the George Washington and Jefferson National Forests (a large part of this forest is in 

the study area). The U.S. Forest Service is upgrading its current operations to an analog 

narrowband system utilizing tone-code squelch enabled repeaters. All U.S. Forest Service district 

offices will be tied to the supervisor’s office via a T-1 landline and system control and dispatch 

will be performed using radio control over Internet Protocol (IP) technology. 

Figure 4-2. Plot of USDA Frequency Assignments within a 100 Mile Radius 

of Washington, D.C. in the 162-174 MHz band

4.3.2 United States Department of Commerce (DOC) 

The DOC mission is to promote job creation, economic growth, and improved living 

standards for all Americans by working in partnership with business, universities, communities, 

and workers to build for the future and promote U.S. competitiveness in the global marketplace 

by strengthening and safeguarding the nation’s economic infrastructure, and keeping America 

competitive with cutting-edge science and technology.19

The DOC operates a variety of radio communications systems for weather data 

dissemination, National Oceanic and Atmospheric Administration (NOAA) Weather Radio 

(NWR), Emergency Managers Weather Information Network, as well as the more conventional 

systems found in most federal agencies. Many of these systems operate in bands other than the 

 

19 U.S. Department of Commerce, The Commerce Mission Statement, at 

http://www.osec.doc.gov/bmi/budget/strtgc/aintro.pdf. 
4-12

government Very High Frequency (VHF) band of 162-174 MHz. However, the DOC has the 

fourth largest amount of assignments in the Washington, D.C. area, with 182 assignments as 

shown in Table 4-3. The location of the GMF assignments is shown in Figure 4-3. 

The DOC has two bureaus – the National Institute of Standards and Technology (NIST) 

and the National Weather Service (NWS) – that have frequency assignments in the outlined area 

and this band. The NWS has 74 assignments and NIST has nine, which are further described 

below. In addition, DOC has three assignments for the Office of the Secretary for the Silver 

Spring office and two other assignments in Baltimore. 

National Institute of Standards and Technology (NIST) 

Of NIST’s nine assignments, three are for police/fire/medical emergency 

communications, two for direct support of research and one for paging, and all are on or in the 

vicinity of the Gaithersburg campus. The other three serve to coordinate transportation, two 

transmitting in Washington, D.C., and one in Gaithersburg, Maryland. All operations are 

currently 25 kHz analog mobile and handheld radios. None of the operations use repeaters. 

National Weather Service (NWS) 

Many NWS assignments, both in and outside the Washington, D.C. area are associated 

with the collection and dissemination of meteorological information. These include 

NWR stations, which operate continuously on one of seven frequencies (162.40-162.55 MHz) 

allotted for this use. This is a transmit-only broadcast type network. The Remote Atmospheric 

Monitoring and Observation System stations operate along U.S. coasts 24 hours a day on 

163.325 and 163.350 MHz and report tide and other ocean data to central collection points. The 

hydrological stations operate 24 hours to collect such data as cumulative rainfall and rain rate, 

snow depth and stream height, typically at unmanned and remote locations. There are 60 

hydrological assignments on the frequencies 169.425, 169.4375, 169.475, 169.5, 170.25, 

171.1125 and 171.925 MHz. 

DOC’s future plans indicate a one-for-one swap out of narrowband equipment for their 

current wideband radios. Some areas, such as the DOC security division, have already converted 

to narrowband analog operations. 
4-13

Figure 4-3. Plot of DOC Frequency Assignments within a 100 Mile Radius 

of Washington, D.C. in the 162-174 MHz Band

4.3.3 United States Coast Guard (USCG) 

The USCG is a military, multi-mission, maritime service and one of the nation’s five 

Armed Services. Its mission is to protect the public, the environment, and U.S. economic 

interests – in the nation’s ports and waterways, along the coast, on international waters, or in any 

maritime region as required to support national security.20

 The USCG has 14 assignments, as shown in Table 4-3, in the 162-174 MHz band, within 

the Washington, D.C. area. Figure 4-4 shows the location of those assignments. The USCG 

typically operates simplex, data encryption standard (DES), systems primarily for firefighting 

and security. The USCG has eight sites in the study area with all being fixed/mobile law 

enforcement or handheld building security. Currently, all channels are wideband (25 kHz); 

however, all USCG handheld and mobile radios are capable of narrowband analog and digital 

operation when required. The USCG is adding the 162-174 MHz and 406.1-420 MHz bands to 

their short-range Rescue 21 (R-21) communication system (talk-in coverage out to 20 miles from 

shore). R-21 will be capable of operating on the 40 discrete frequencies set aside in the VHF and 

UHF bands for interoperability between law enforcement and public safety organizations during 

disasters and emergencies.21 This will allow the USCG to communicate with federal, state, and 

local agencies operating on agency specific frequencies within the VHF (150.8–174 MHz) and 

UHF (406.1–420 MHz) frequency range. R-21 will be a P25/TIA 102 compliant digital 

narrowband system with console-to-console patch capability that can be used to link 

 

20 U.S. Coast Guard, Overview, at http://www.uscg.mil/overview/. 

21 NTIA has identified 40 (20-VHF and 20-UHF) interoperability channels in the 162-174 MHz and 406.1-420 MHz 

bands for law enforcement and incident response plans. See NTIA Manual, supra note 1, at Section 4.3.16. 
4-14

communications between the USCG and other federal, state, and local agencies that do not 

operate within R-21 frequency bands or use non-interoperable communication systems. 

Figure 4-4. Plot of USCG Frequency Assignments within a 100 Mile Radius 

of Washington, D.C. in the 162-174 MHz Band

4.3.4 United States Department of Defense (DOD) 

The mission of the DOD is to defend United States territory and any occupied areas, 

overcome any aggressor that imperils our nation’s peace and security, maintain freedom of the 

seas, stabilize or contain international disturbances, and defend the United States through control 

and exploitation of air and space.22 The DOD is comprised of the four military branches: the 

Army, Navy, Marine Corps, and Air Force. DOD’s presence in the 162-174 MHz band is 

limited to base security (law enforcement), fire, and emergency medical services. Table 4-3 

shows a breakdown of assignments by military branch and Figure 4-5 shows the location of 

those assignments for the Washington, D.C. area. The systems are typically wideband analog 

simplex or half-duplex channels using repeaters, where necessary, to extend the range of the net. 

On some bases, the Army has used cross-band repeaters to provide interoperability between 

security forces operating in different bands. 

 

22 U.S. Department of Defense, DOD 101: An Introductory Overview of the Department of Defense, at 

http://www.dod.mil/pubs/dod101/. 
4-15

Figure 4-5. Plot of DOD Frequency Assignments within a 100 Mile Radius 

of Washington, D.C. in the 162-174 MHz Band

 The Army is developing a P25/TIA 102 compliant narrowband digital trunked system in 

the 380-400 MHz band to replace most systems currently in the 162-174 MHz band. Phase 1 of 

the Regional Concept 2005+ plan is tentatively scheduled to become operational by the end of 

2004.23 The system will include all branches of the service and will expand region-by-region to 

eventually interconnect military installations throughout the United States. 

4.3.5 United States Department of Energy (DOE) 

The DOE’s mission is to advance the national and economic security of the United 

States; promote scientific and technological innovation in support of that mission; and ensure the 

environmental cleanup of the national nuclear weapons complex.24

The DOE has 45 assignments, as shown in Table 4-3, in the Washington, D.C. area. 

Figure 4-6 shows the location of those assignments. The DOE already utilizes digital 

narrowband base stations, mobiles and portables to support a multi-channel force protection 

network between the headquarters building in Washington, D.C. and Germantown, Maryland. 

Each site operates on an independent pair of frequencies but can be linked via radio frequency 

(RF) to each other. This allows each site to have control of the Force Protection network. The 

network nominally operates in the digital narrowband mode, but has, on occasion, required 

encryption operation in wideband analog or digital modes. The DOE has other two-way repeater 

systems, a simulcast paging system, and simplex radios which are going to be gradually replaced 

with analog narrowband radios, due to the higher cost of digital narrowband equipment. 

 

23 See, Section 5 for a more detailed description of this system. 

24 U.S. Department of Energy, About DOE, at http://www.doe.gov 
4-16

Figure 4-6. Plot of DOE Frequency Assignments within a 100 Mile Radius 

of Washington, D.C. in the 162-174 MHz Band 

4.3.6 Federal Aviation Administration (FAA) 

The mission of the FAA is to provide a safe, secure, and efficient global aerospace 

system that contributes to national security and the promotion of U.S. aerospace safety. “As the 

leading authority in the international aerospace community, the FAA is responsive to the 

dynamic nature of customer needs, economic conditions, and environmental concerns.”25

The FAA has 108 assignments, as shown in Table 4-3, in the Washington, D.C. area. 

Figure 4-7 shows the location of these assignments. Eighty-five percent of the FAA’s 

assignments are dedicated to meeting its nationwide land mobile requirements through its 

Command, Control and Communications (C3) program. Previously called the National Radio 

Communications System (NRCS), this conventional VHF/FM system is used to manage, operate 

and restore the National Airspace System in support of FAA, United States Department of 

Transportation (DOT), and DOD functions during national disasters and security emergencies. 

Also, this system provides daily support for airways facilities technicians, civil aviation security 

agents, air traffic administration, and flight standards. During local, regional, or national 

disasters or emergencies, field personnel use the network for command and control missions. 

The NCRS/C3 is not confined to urban areas or airports, but covers a wide territory to reach 

remote FAA facilities such as radars, microwave radios, and other navigation/communications 

facilities. 

 Currently, the FAA is upgrading and expanding its existing equipment to meet the NTIA 

2005 narrowband mandate and provide greater command and control support in the aftermath of 

the events of September 11, 2001. Older, wideband analog radios are being replaced with new 

digital systems. Primarily, the FAA is replacing current repeaters and base stations on a one-to-

 

25 See Federal Aviation Administration, What We Do-Mission, at http://www.faa.gov 
4-17

one basis, using most existing frequency authorizations. In addition, the old NRCS frequency 

channel plan will remain the basis of the new C3 program. However, due to the need for 

expansion and changes in frequency allotments over the past two decades, there will be some 

alterations in geographical location and frequencies. 

Figure 4-7. Plot of FAA Frequency Assignments within a 100 Mile Radius 

of Washington, D.C. in the 162-174 MHz Band

4.3.7 United States Department of Homeland Security (DHS) 

 The DHS was created in March 2003, with its primary mission to protect the nation 

against further terrorist attacks.26 Component agencies will analyze threats and intelligence, 

guard our borders and airports, protect our critical infrastructure, and coordinate the response of 

our nation for future emergencies. Besides providing a better-coordinated defense of the 

homeland, DHS is also dedicated to protecting the rights of American citizens and enhancing 

public services, such as natural disaster assistance and citizenship services, by dedicating offices 

to these important missions.27 The DHS is a consolidation of agencies and bureaus from various 

departments, including: The Immigration and Naturalization Service (INS) (DOJ), The U.S. 

Customs Service (Customs) (Treasury), The Transportation Security Administration (TSA) 

(DOT), Federal Law Enforcement Training Center (Treasury), Animal and Plant Health 

Inspection Service (USDA), Office for Domestic Preparedness (DOJ), The Federal Emergency 

Management Agency (FEMA), Strategic National Stockpile and the National Disaster Medical 

System (Health and Human Services), Nuclear Incident Response Team (DOE), Domestic 

Emergency Support Teams (DOJ), National Domestic Preparedness Office (FBI), Chemical 

Biological Radiology and Nuclear Countermeasures Programs (DOE), Environmental 

Measurements Laboratory (DOE), National Biological Warfare Defense Analysis Center (DOD), 

Plum Island Animal Disease Center (USDA), Critical Infrastructure Assurance Office (DOC), 

 

26 See supra note 10. 

27 U.S. Department of Homeland Security, DHS Organization, at http://www.dhs.gov/dhspublic/theme_home1.jsp. 
4-18

Federal Computer Incident Response Center (Government Service Administration), National 

Communications System (DOD), National Infrastructure Protection Center (Federal Bureau of 

Investigation (FBI)), Energy Security and Assurance Program (DOE), the United States Secret 

Service (USSS) (Treasury) and the USCG (DOT).28 Although the GMF assignments from the 

various agencies have not been officially reassigned to DHS, as of November 2002, the 

department has the potential to become the largest user in the Washington, D.C. area in the 162-

174 MHz band. DHS plans to join the IWN with Justice and Treasury as they change their 

legacy systems over to narrowband. For the purpose of this study, no GMF assignment records 

have been re-designated to DHS but remained under their previous departments or agencies. 

4.3.8 United States Department of the Interior (DOI) 

The DOI is the nation’s principal conservation agency. Its mission is to protect 

America’s treasures for future generations, provide access to our nation’s natural and cultural 

heritage, offer recreation opportunities, honor our trust responsibilities to American Indians and 

Alaska Natives and our responsibilities to island communities, conduct scientific research, 

provide wise stewardship of energy and mineral resources, foster sound use of land and water 

resources, and conserve and protect fish and wildlife.29 Within the United States, the DOI has 

radio communications requirements in support of the National Park Service, Bureau of Land 

Management, Fish and Wildlife Service, Bureau of Indian Affairs, Bureau of Reclamation, and 

the U.S. Geological Survey. It is the second largest user with 252 assignments, as shown in 

Table 4-3, in the Washington, D.C. area. The location of the assignments is shown in Figure 4-8. 

DOI primarily utilizes conventional simplex and half duplex analog wideband systems for 

building security, executive services, maintenance, and law enforcement. The DOI plans to 

convert all LMR radios to digital narrow-band. They are also in the initial planning stage, and 

are looking for partners, to establish and share a Washington, D.C. area P25/TIA 102 compliant 

digital trunked system with the U.S. Park Police. 

Figure 4-8. Plot of DOI Frequency Assignments within a 100 Mile Radius 

of Washington, D.C. in the 162-174 MHz Band 

 

28 Id., at http://www.dhs.gov/dhspublic/display? Content = 3345. 

29 U.S. Department of the Interior, DOI Quick Facts, at http://www.doiu.nbc.gov/orientation/facts.cfm. 
4-19

4.3.9 United States Department of Justice (DOJ) 

The DOJ has a primary mission to “enforce the law and defend the interests of the United 

States according to the law, to provide federal leadership in preventing and controlling crime; to 

seek just punishment for those guilty of unlawful behavior; to administer and enforce the 

nation’s immigration laws fairly and effectively; and to ensure fair and impartial administration 

of justice for all Americans.”30 Wireless communications are critical to meet these mission 

requirements. DOJ uses the 162-174 MHz band extensively for its LMR operations and it is the 

largest user of this band with 672 assignments, as shown in Table 4-3, in the Washington, D.C. 

area. The location of the assignments is shown in Figure 4-9. DOJ currently utilizes a series of 

multi-channeled, pseudo-simulcast (non-synchronized), wideband (25 kHz) analog repeaters 

located throughout the Washington, D.C. area. The system is also augmented with voting 

repeaters to “extend” the transmit range of the portable radios. Many of the voted receivers are 

connected to the network via landline. 

The future plans for the DOJ involve the development of the IWN.31 The IWN initiative 

will consolidate all of the DOJ bureaus into a single LMR communications system. This new 

digital narrowband (12.5 kHz) system, which utilizes both the 162-174 MHz and 406.1-420 MHz 

bands, is being developed to increase spectrum efficiency, improve interoperability among all 

bureaus within DOJ as well as other federal law enforcement agencies, and maximize 

efficiencies and savings through shared communications systems. The IWN will consolidate the 

communications needs of the Office of the Attorney General, Federal Bureau of Investigation 

(FBI), Drug Enforcement Administration (DEA), Immigration and Naturalization Service (INS), 

U.S. Marshals Service (USMS), Bureau of Prisons (BOP) and various bureaus of the DHS. 

Section 6 of this report has a complete description of the IWN initiative. 

 

30 U.S. Department of Justice, Organization, Mission, and Functions Manual, March 2004, Overview, at 

http://www.usdoj.gov/jmd/mps/manual/overview.htm 

31 U.S. Department of Justice and U.S. Department of the Treasury, High Level Design Report (on file with author). 
4-20

Figure 4-9. Plot of DOJ Frequency Assignments within a 100 Mile Radius 

of Washington, D.C. in the 162-174 MHz Band 

4.3.10 United States Department of the Treasury (Treasury) 

The Treasury Department has a primary mission to promote prosperous and stable 

American and world economies, manage the government’s finances, and safeguard our financial 

systems.32 Prior to March 2003 Treasury also protected our nation’s leaders and pursued a safe 

and drug-free America.33 Wireless communications are critical to meet these mission 

requirements. For example, the USSS provides protection for the President, Vice President, and 

political leaders of the United States, as well as protection to visiting foreign dignitaries. 

Treasury uses both the 162-174 MHz and 406.1-420 MHz bands for 95 percent of its law 

enforcement and protection operations. The majority (more than 80 percent) of their land mobile 

radio equipment operates in the 162-174 MHz band.34 Treasury is the third largest user with 231 

assignments, as shown in Table 4-3, in the Washington, D.C. area. The location of the 

assignments is shown in Figure 4-10. Treasury currently uses a variety of wideband analog 

systems based on the mission requirement. The USSS, due to their mission requirements, relies 

mostly upon mobile and hand-held radios, with repeaters, as necessary to extend the coverage of 

their radios. Treasury also has major in-building coverage requirements, such as bank vaults and 

building security, which requires them to use in-building repeaters for “campus” type 

communications. Treasury’s future plans include joining the IWN to satisfy the majority of their 

 

32 U.S. Department of the Treasury, Duties and Functions at http://www.ustreas.gov/education/duties/ 

33 With the establishment of the Department of Homeland Security in 2002, the U.S. Secret Service and their 

functions, transferred from the Department of the Treasury effective March 1, 2003. See supra note 10. 

34 NTIA Special Publication 01-48, supra note 9 at 3-2. 
4-21

communications requirements.

Figure 4-10. Plot of Treasury Frequency Assignments within a 100 Mile Radius 

of Washington, D.C. in the 162-174 MHz Band 

4.3.11 United States Capital Police (USCP) 

The USCP is responsible for the safety and security of all members and staff of the 

United States House of Representatives and the United States Senate while they are physically 

located in and around the buildings of the Capitol campus and other locations within 

Washington, D.C. USCP also assists the United States Park Police, the United States Secret 

Service, Amtrak Police, Washington Metropolitan Area Transportation Agency (WMATA) 

Police, and the Washington, D.C. Metropolitan Police as needed for motorcades, demonstrations, 

emergency responses, and other special events.

In the Washington, D.C. area, the USCP has 25 assignments, as shown in Table 4-3. 

Figure 4-11 shows the location of those assignments. The USCP has ten frequency assignments 

in the VHF spectrum for use in the Washington, D.C. metropolitan area. These are paired into 

five channels used as a voting repeater system with satellite receivers and high power base 

stations. The combination of over 100 satellite receivers and high power transmitters provides 

officers and agents of the USCP with coverage of the Capitol and all buildings in the Capitol 

campus as well as off-campus communications in the Washington, D.C. metropolitan area. The 

USCP also has one shared frequency pair assignment for use when outside the Washington, D.C. 

metropolitan area. 

The five “in-town” frequency pairs are used for voice communications 365 days per year. 

The single shared “out-of-town” assignment pair is used when the members Congress have a 
4-22

scheduled offsite event that requires a presence of officers and agents of the USCP for security 

and protection. The USCP also provide on-site security for congressional retreats and 

conferences at remote locations. While securing these locations, USCP utilizes shared frequency 

assignments to coordinate their efforts. 

The USCP intends to continue conventional analog voice operations on all the existing 

assigned VHF frequencies to comply with the narrowband requirements. Equipment that is 

narrowband compliant is currently being purchased and issued to the officers and agents. The 

target date to complete the conversion to narrowband is late November 2004. 

The USCP is planning to implement a full simulcast site on their Channel 4 (wide area 

channel) and a multi-transmit (simulcast, not timed) site on Channels 1, 2, 3, and 5 near 

Cheltenham, Maryland, where the new Federal Law Enforcement Training Center (FLETC) is 

being built. The USCP is planning to have a backup command center at the Cheltenham facility. 

There are no plans at this time to convert to any form of digital, shared agency, or trunked voice 

communications.

Figure 4-11. Plot of USCP Frequency Assignments within a 100 Mile Radius 

of Washington, D.C. in the 162-174 MHz Band
4-23

4.3.12 United States Postal Service (USPS) 

The USPS is a national institution that is an integral part of the infrastructure of the 

American economy. The USPS “binds the nation together through the business, literary, and 

personal correspondence of the people, providing prompt, reliable service to all communities as 

required by the Postal Reorganization Act of 1970.”35

The USPS has 41 area specific assignments, as shown in Table 4-3, in the Washington, 

D.C. area. Figure 4-12 shows the location of these assignments. The USPS is divided into two 

major bureaus, the Mail and U.S. Postal Inspection Service both of which use the LMR system in 

the VHF band. 

Mail Bureau

Currently, the Mail Bureau utilizes LMR systems at mail processing facilities within the 

Washington, D.C. area. These facilities have extensive requirements for in-building 

communications. The communications systems are used for maintenance, mail processing, 

safety and emergency operations. The communications at these facilities typically provide 

coverage around the facility for about 2-3 miles. The configuration presently is analog with 

multiple repeaters and an extensive in-building antenna system throughout the facilities. In some 

facilities, there are outside communications between mobiles and the repeater. The USPS is in 

the process of converting the wideband VHF systems to narrowband. 

The Mail Bureau anticipates that the present VHF assignments for internal building 

communications will move to the UHF band. External mobile communications, however, will 

most likely remain in the VHF band. Both UHF and VHF equipment will remain analog. 

U.S. Postal Inspection Service

Presently, the U.S. Postal Inspection Service utilizes conventional analog VHF LMR 

assignments for both in-building and external communications between repeaters, bases, mobiles 

and handhelds. The U.S. Postal Inspection Service is moving toward a UHF communications 

system. The wideband VHF assignments will be eliminated in place of UHF narrowband multilink technology. There will be some VHF narrowband assignments to be used for 

interoperability between the bureaus and other law enforcement agencies. 

 

35 United States Postal Service, Five Year Strategic Plan – Introduction (2003), at 

http://www.usps.com/strategicdirection/__pdf/fiveyearplan2004-2008.pdf 
4-24

Figure 4-12. Plot of USPS Frequency Assignments within a 100 Mile Radius 

of Washington, D.C. in the 162-174 MHz Band

4.3.13 United States Department of Veterans Affairs (VA) 

The VA’s mission is to provide integrated and innovative health care services and 

benefits to eligible veterans and their beneficiaries.36 The VA has 30 assignments, as shown in 

Table 4-3, in the Washington, D.C. area. Figure 4-13 shows the location of these assignments. 

The VA operates several conventional wideband systems in the area supporting law 

enforcement, fire and security, emergency medical services, and maintenance in and around their 

hospital grounds and headquarters. The VA is in the process of moving its Washington, D.C., 

LMR operations out of the VHF band and joining the 1CommWireless narrowband trunked 

system, a commercial service operating in federal spectrum.37 The VA’s Baltimore operation 

has already transitioned to analog narrowband and is expected to remain analog until the end of 

the equipment’s life cycle. 

 

36 U.S. Department of Veterans Affairs, About VA., at http://www1.va.gov/about_va/. 

37 Formerly the Federal Specialized Mobile Radio (FEDSMR); see Section 5 for a detailed description. 
4-25

Figure 4-13. Plot of VA Frequency Assignments within a 100 Mile Radius 

 of Washington, D.C. in the 162-174 MHz Band

4.3.14 Other Agencies or Bureaus 

Agencies or bureaus within this group are comprised of various federal government 

entities that have twenty or fewer assignments in the 162-174 MHz band within the Washington, 

D.C. area. Table 4-3 provides a list of the other agencies or bureaus and breakdown of their 

assignments. Figure 4-14 provides the location of these assignments. The assignments used by 

these entities are primarily used for law enforcement, building security, administrative, 

maintenance, or paging. Most agencies utilize simplex or half-duplex analog wideband 

networks, with some of the larger networks (e.g., the Government Services Administration’s inbuilding maintenance network), utilizing base stations or repeaters to provide the necessary inbuilding coverage for the numerous federally owned buildings they are responsible for. Some 

agencies, such as the Social Security Administration, are sharing frequencies and networks with 

other agencies because they do not have large enough requirements to justify their own systems. 

Most of the nets are agency-exclusive and the area of coverage required is just their headquarters 

building or buildings within a “campus” type environment. Future narrowbanding requirements 

for many of these agencies will be accomplished by a simple one-for-one swap-out of analog 

wideband to analog narrowband radios. Other agencies, such as the State Department, have 

already migrated to conventional narrowband digital radios. 
4-26

Figure 4-14. Plot of Other Agency or Bureau Frequency Assignments within a 100 Mile Radius 

of Washington, D.C. in the 162-174 MHz Band 

4.4 SUMMARY 

This section provides an overview of the federal agencies’ uses of the 162-174 MHz band 

in the Washington, D.C. area. In the early 1990’s, NTIA mandated that the federal agencies 

migrate to more spectrally efficient narrowband technologies in this band by January 1, 2005. 

Agencies are at different stages of meeting the narrowband mandate (see Section 5). This 

includes: already procured narrowband equipment to replace wideband radios, narrowband 

equipment on order, new systems proceeding through the test and evaluation phase, or having 

plans in development for replacement systems. Some agencies stated that due to their unique 

mission, sharing of systems may not be practical, while other agencies stated that if the 

opportunity were presented to them, they would consider joining a shared system (e.g., IWN). 
5-1

SECTION 5

OTHER FEDERAL GOVERNMENT EFFORTS 

REGARDING SPECTRUM EFFICIENCY

5.1 GENERAL 

Since there is limited land mobile spectrum, agencies must employ new technologies and 

techniques to satisfy future requirements. The areas in which the federal government is 

implementing new technologies and techniques to improve spectrum efficiency include, but are 

not limited to, the following: migration to narrowband technology, integrated wireless networks, 

performance standards, and trunking technology. This information is important to understand for 

potential incorporation into the study. This section provides a brief discussion of some of the 

various mandates, initiatives, and programs for improving spectrum efficiency in the federal 

government. 

5.2 MIGRATION TO NARROWBAND TECHNOLOGY 

In 1992, Congress passed the Telecommunications Authorization Act of 1992.38 Title I 

of this act required NTIA to develop and implement a plan to make federal LMR systems use 

more spectrum efficient technologies. A report summarizing the plan and its implementation 

schedule was prepared and submitted to Congress as required by the legislation.39 As part of this 

plan, NTIA selected a 12.5 kHz channel width for re-channeling (or re-farming) the federal fixed 

and mobile bands.40 The reduction in channel width from 25 kHz to 12.5 kHz will effectively 

double the number of available channels in the 162-174 MHz and 406.1-420 MHz bands.41

The federal public safety agencies’ pursuit of more spectrum efficient technologies is a 

necessary tool to satisfy the growing demands for wireless communications within the federal 

government. As stated in the previous section, the federal agencies are in various stages of 

meeting the NTIA narrowband mandate. 

 

38 NTIA Act, supra note 2. 

39 NTIA Report 93-300, supra note 6, at 1. 

40 Id., at 8. 

41 After Jan. 1, 2005, all systems in the 162-174 MHz band must conform to this standard. After Jan. 1, 2008, all 

systems in the 406.1-420 MHz band must conform to this standard. 
5-2

5.3 TECHNICAL PERFORMANCE STANDARDS 

NTIA has long been an advocate of technical standards for receivers to minimize 

interference and increase overall spectrum efficiency. In addition, state and local public safety 

entities are also recognizing the importance of establishing receiver standards to minimize 

interference. As the demand for wireless services continues to grow, straining the limited 

spectrum resources that are available, it is becoming increasingly important to manage the 

resource by considering total system performance. Thus, both the transmitter and receiver 

performance characteristics must be considered for maximum spectrum efficiency. In the 

162-174 MHz and 406.1-420 MHz bands, NTIA has adopted receiver performance standards, in 

addition to transmitter performance standards, that include: intermodulation rejection; adjacent 

channel selectivity; and spurious response attenuation.42 NTIA and the federal public safety 

agencies believe that receiver performance standards are necessary to reduce interference from 

adjacent channel transmitters. This will allow transmitters and receivers to operate closer to each 

other, improve performance, and increase the overall efficiency of these bands. 

On March 24, 2002, the FCC released a Notice of Inquiry (NOI) that requested 

information to a variety of questions pertaining to the use of receiver standards.43 NTIA 

submitted reply comments to the FCC’s NOI encouraging the use of receiver standards, where 

appropriate, to prevent interference and utilize the spectrum more efficiently.44

The federal public safety agencies have also engaged in a long-term standards 

development process known as P25/TIA 102, a collective effort by industry and the state and 

local public safety agencies. This multi-phase effort has resulted in the development of an 

extensive set of standards for digital public safety wireless communications.45 Phase 1 of 

P25/TIA-102 specifies a 12.5 kHz channel width consistent with the NTIA narrowband mandate. 

Phase 2 provides a migration path to a narrower channel width of 6.25 kHz (or equivalent) as 

technology permits. The technology readiness obstacles currently associated with P25 Phase 2 

include battery size and weight, linear amplifiers, and oscillator stability. Also, based on 

information from manufacturers, the 6.25 kHz Phase 2 option is likely to be delayed several 

years due to technical problems with encryption techniques in very narrow bandwidths. 

 

42 NTIA Manual, Section 5.3.5.2. B, supra note 1, at 5-24-26. 

43 Federal Communications Commission, ET Docket No 03-65, Interference Immunity Performance Specifications 

for Radio Receivers, March 24, 2003. 18 F.C.C.R. 6039 (2003). 

44 National Telecommunications and Information Administration, U.S. Department of Commerce, Comments of the 

National Telecommunications and Information Administration in the matter of Interference Immunity Performance 

Specifications for Radio Receivers, ET Docket No 03-65, November 12, 2003. 

45 The standards are published in the Telecommunications Industry Association/Electronics Industries, an 

American Standards Institute (ANSI) accredited process. For example, see, http://www.ANSI.org. 
5-3

5.3.1 Trunking Technology 

The use of trunking technology as a means of increasing the efficiency and utility of 

spectrum resources is starting to be considered within the 162-174 MHz band and is already in 

use in the 406.1-420 MHz band. Federal agencies use trunked systems for limited areas with a 

high concentration of use and for campus environments, such as federal prisons, hospitals, 

laboratories, and training facilities. The DOD has the largest number of trunked systems 

operating and planned within the 406.1-420 MHz band. DOD uses these systems to satisfy the 

important needs of national security, training, administration, and emergency preparedness at its 

various facilities. Some planned federal systems, such as the IWN and the DOD Enhanced Land 

Mobile Radio (ELMR) System, will use trunking technology in their designs to satisfy some of 

their requirements, especially in areas with large concentrations of users. 

5.3.2 162-174 MHz Band Restructuring 

Although specifications and standards have long existed for equipment operating within 

the radio spectrum environment, the 162-174 MHz band is currently unstructured in its 

accommodation of user applications. Specifically, the current band allocation does not include 

separate frequency sub-bands for base station transmitters and mobile transmitters. Historically, 

this has not presented insurmountable difficulties for user applications within the band because 

spectrum has been readily available and most applications use simplex technologies. However, 

as the band becomes more congested, the ability to obtain additional suitable spectrum becomes 

increasingly difficult, even with the implementation of improvements in equipment technology 

(e.g., 12.5 kHz channels). As more users move to repeaters, trunked systems, and other 

technologies that require duplex frequencies, the need for a structured band becomes more 

evident. Structuring a band that already exhibits heavy use is a complicated process, and can 

also have numerous implications for spectrum management, the users, and their associated 

operations already within the band. 

5.3.3 Frequency Reuse 

Although the amount of spectrum available is finite, any given portion of spectrum can 

be re-used many times over, depending on the right circumstances. In many cases, the “right 

circumstances” includes the requirement that multiple users be separated by enough geographical 

distance so that the signals from the various user radios do not interfere with each other. If too 

large a distance is chosen, frequency re-use efficiency will suffer and not as many users will be 

able to use that frequency. If too small a distance is chosen, user systems will interfere with each 

other. 

For routine licensing in a common radio service (e.g., federal LMR systems), theory and 

practical experience have often been summarized in procedural “rules-of-thumb” that require 

different users, on the same frequency, be separated by some fixed distance, e.g., 100 miles. For 

a specific set of users, however, the required minimum separation distance can vary over a wide 

range, depending especially on the propagation of radio signals over the specific terrain that 

separates the specific users. For a specific set of users and terrain, the rule-of-thumb separation 
5-4

distance can be much too large, resulting in inefficient frequency re-use. However, if the rule-of 

thumb distance is too small, interference may result. 

The frequency reuse issue can be investigated in several ways. First, the existing 

procedure for establishing separation distances can be compared to terrain-dependent 

propagation models, agency requirements, and required signal to interference ratios for new 

systems. Once this is accomplished, it can be determined if existing separation policies could be 

refined to provide improved frequency re-use criteria. Secondly, possible changes in spectrum 

management techniques could be examined to determine whether the use of more accurate 

technical modeling used to routinely evaluate the required separations for specific users, will 

provide a useful amount of improved geographical frequency re-use. In this case, “useful” 

means a balance between improved re-use and the increased cost of processing a user 

assignment, as well as less future flexibility to make use of an assignment. 

In addition, it should be noted that frequency re-use can be enhanced by deliberately 

restricting the size of transmitter coverage areas (e.g., low power/low antenna height sites). Such 

techniques also greatly decrease the required minimum separation distance for re-using a 

frequency. Although such small-cell techniques have been widely used by cellular systems, they 

have not yet been widely used by public safety agencies due to costs associated with constructing 

additional sites. Nevertheless, public safety agencies may potentially benefit from the use of 

small cells in a dense urban setting. The subject of frequency reuse as it relates to spectrum 

efficiency will be addressed in subsequent phases of this report. 

5.4 INITIATIVES AND SPECTRUM EFFICIENCY IMPROVING PROGRAMS 

5.4.1 NTIA Spectrum Summit 

NTIA held a Spectrum Summit in April 2002 to help identify the best solutions to 

challenges posed by management of the nation's airwaves. The purpose of the spectrum 

management and policy summit was to explore new ideas to develop and implement spectrum 

policy and management approaches that will make more efficient use of the spectrum; provide 

spectrum for new technologies; and improve the effectiveness of domestic and international 

spectrum management processes.46

During the Spectrum Summit one of the major concerns expressed by the federal and 

private sector spectrum management community, and radio service users and providers, was 

future spectrum availability to satisfy needs to expand services and to accommodate new 

technologies. It was suggested that additional spectrum to fulfill these needs could possibly 

come from current users improving their spectrum efficiency through new technologies or 

creative assignment approaches, increased sharing, more realistic interference protection criteria, 

or some combination of all of these. 

 

46 National Telecommunications and Information Administration, Notice, Spectrum Management and Policy 

Summit, 67 Fed. Reg. 10,682 ( March 5, 2002). See also, NTIA Spectrum Summit at 

http://www.ntia.doc.gov/ntiahome/summit/index.html. 
5-5

5.4.2 Federal Communication Commission’s (FCC) Spectrum Policy Task Force 

In June of 2002, the FCC convened the Spectrum Policy Task Force to address a number 

of policy issues important to improving the way spectrum is managed. One primary issue 

addressed by the task force was spectrum efficiency. Spectrum efficiency questions focused on 

how to promote and measure spectrum efficiency, while protecting the ability of public safety 

entities to do their jobs in light of the increasing demand for spectrum. In its attempt to develop 

a method to measure spectrum efficiency, the task force concluded that, due to differences in 

radio services, it was not feasible to select an objective means to compare unlike services and 

users.47 The Task Force identified three variations on and definitions for the term “efficiency” as 

applicable to spectrum management: spectrum efficiency, technical efficiency and economic 

efficiency.48

Both NTIA’s Spectrum Summit and the FCC’s Spectrum Policy Task Force provided 

valuable insight into current thoughts on spectrum efficiency. One of the common themes 

expressed in both forums is improving spectrum efficiency, especially in the bands used for 

mobile communications. Many have observed that the federal government agencies have fewer 

mobile users per unit of the spectrum than is true for business, non-federal public safety, or 

commercial (cellular phone and PCS) applications. Public safety users require high reliability 

and availability with frequency channels whose traffic loads change drastically with planned or 

unplanned events. As a result of these operational requirements, federal public safety 

frequencies are not in use all of the time, which could be perceived as inefficient use of the 

spectrum. Additionally, federal users generally require frequencies on a nationwide basis, 

limiting the ability to re-use much of what is used. 

5.4.3 General Accounting Office (GAO) Reports 

The GAO, in its report on improving spectrum management, found that, although NTIA 

has oversight activities that encourage efficient use of the spectrum, the lack of resources has 

hindered the agency’s effectiveness.49 Lack of resources was also an issue for the federal 

agencies. In fact, the federal agencies reported difficulties implementing NTIA initiatives such 

as land mobile narrowbanding, primarily due to staffing, priority, and budget issues. The report 

also points out that many federal government uses of the spectrum do not have commercial 

counterparts and cannot easily be compared using common efficiency measures, such as the 

number of subscribers per hertz.50 The report also briefly explored the concept of using 

spectrum fees as an incentive for spectrum efficiency. Interestingly, at least one of the agencies 

 

47 Spectrum Policy Task Force Report, ET Docket No. 02-135, Federal Communications Commission, (November 

15, 2002), at 21, available at http://hraunfoss.fcc.gov/edocs_public/attachmatch/doc_228542A.pdf. 

48 Id., at 21 

49 Telecommunications: Better Coordination and Enhanced Accountability Needed to Improve Spectrum 

Management, General Accounting Office, GAO-02-906, (September 2002), at 25. 

50 Id., at 31.
5-6

interviewed stated that NTIA’s current reimbursement structure for spectrum management 

services was not large enough to encourage spectrum efficiency. Spectrum fees to encourage 

efficiency versus fees to recover the cost of spectrum management will be addressed in a followon study. 

In another report on current issues relating to spectrum management, the GAO, through 

interviews with agency and industry officials, attempted to determine how the federal 

government encourages efficient use of spectrum by federal agencies.51 In findings similar to 

the previous report, the GAO concludes that NTIA is required by law to promote the efficient 

and cost-effective use of the spectrum it manages. The process by which NTIA certifies and 

authorizes (assigns) spectrum is designed to promote efficiency, but the justification for use of 

spectrum and review of current assignments is largely left up to the individual agency. The 

GAO found that inadequate resources were the primary reason for a lack of comprehensive 

review of assignments, preventing any enforcement or monitoring activities to identify and 

return unused spectrum. GAO found that, in many cases, the five-year review process, the 

primary tool that NTIA uses to determine if assigned spectrum is actually used, is either not 

accomplished or overdue.52

 

5.4.4 Presidential Initiative to Develop, Implement Spectrum Policy for the TwentyFirst Century 

On June 5, 2003, President Bush announced a new initiative to develop a radio spectrum 

policy for the Twenty-FirstCentury.53 The Executive Memorandum directs the DOC to facilitate 

policy changes to create incentives for more efficient and beneficial use of spectrum and to 

provide a higher degree of predictability and certainty in the spectrum management process as it 

applies to incumbent users; and develop policy tools to streamline the deployment of new and 

expanded services and technologies, while preserving national security, homeland security, and 

public safety, and encouraging scientific research.54 The Secretary of Commerce announced the 

formation of a high-level interagency task force under the Executive Memorandum issued by the 

President that will recommend ways to stimulate more efficient use of the radio frequency 

spectrum by federal government users. The task force will provide recommendations that 

promote effective, efficient and beneficial use of spectrum without unacceptable interference to 

critical incumbents. 

 

51 General Accounting Office, Telecommunications: History and Current Issues Related to Radio Spectrum 

Management, testimony before the Committee on Commerce, Science, and Transportation, U.S. Senate, GAO-02-

814T (June 11, 2002), at 1. 

52 Id., at 14. 

53 Memorandum on the Spectrum Policy for the 21st Century, 39 Pub. Papers 23 (June 9, 2003). 

54 Id. 
5-7

As a part of the initiative, NTIA published a NOI seeking comments on policy reforms 

relative to the management of the radio frequency spectrum.55 The NOI contains a list of 

questions to assist in identifying issues that may need to be addressed in changing U.S. spectrum 

management policies. Comments to the NOI were due May 2004. 

The recommendations resulting from these activities were included in a two-part series of 

reports released by the Secretary of Commerce in June 2004, under the title Spectrum Policy for 

the 21st Century- The Presidents Spectrum Policy Initiative.56 These reports contain 

recommendations regarding the efficient use of the radio spectrum. 

5.4.5 SAFECOM Program Office 

SAFECOM was established in the spring of 2002 to address the wireless communication 

needs of public safety organizations. SAFECOM serves as the umbrella program within the 

federal government to help local, tribal, state and federal public safety agencies improve public 

safety response through more effective and efficient interoperable wireless communications. As 

a public safety practitioner driven program, SAFECOM is working with existing federal 

communications initiatives and key public safety stakeholders to address the need to develop 

better technologies and processes for the cross-jurisdictional and cross-disciplinary coordination 

of existing and future communications systems. 

5.4.6 1CommWireless (Formerly FEDSMR) 

The Washington/Baltimore system, operating under the name of 1CommWireless, is one 

of several federal communications systems in the northeast and southeast that is owned and 

operated by a commercial vendor that provides service to federal users. The 

Washington/Baltimore system is currently transitioning to a new narrowband, multi-site system 

using the transcript protocol (this protocol provides a digital backbone supporting system 

enhancements such as seamless roaming, over-the-air re-keying (OTAR), console interfaces, 

privacy, and compatibility with other systems). Radio equipment for use on the system is 

available from several vendors at a price considerably less than the wideband radios formerly 

employed on the company’s previous analog system. The sites include Baltimore Washington 

International airport, Martinsburg, West Virginia, Veterans Administration Building at Lafayette 

Park, Crystal City, and Dulles Airport with several others currently under consideration. The 

system will be using twenty channel pairs that will be reused throughout the area similar to 

cellular radio’s reuse of the spectrum. The frequencies are assigned to NTIA, which permits the 

contractor, in this case, 1CommWireless to use the frequencies to provide telecommunication 

services exclusively to the federal government in the 406-420 MHz government band. This 

system supports over 2,000 subscriber units. Current federal government agencies using the 

 

55 National Telecommunications and Information Administration, Docket No. 040127027-4027-01,

69 Fed. Reg. 4,923 (February 2, 2004), available at 

http://www.ntia.doc.gov/ntiahome/frnotices/2004/spectruminitiativenoi_01282004.pdf. 

56 Spectrum Policy for the 21st Century- The President’s Spectrum Policy Initiative: Report 1 “Recommendations of 

the Federal Government Spectrum Task Force, U.S. Department of Commerce, NTIA, June 2004; Spectrum Policy 

for the 21st Century- The President’s Spectrum Policy Initiative: Report 2 “Recommendations for State and Local 

Governments and Private Sector Responses, U.S. Department of Commerce, NTIA, June 2004. 
5-8

1CommWireless system include Bolling Air Force Base, Smithsonian Institution, United States 

Holocaust Memorial Museum, United States Senate, Office of the Inspector General, and the 

Naval District of Washington Transportation among others. These user organizations pay a 

monthly fee based on the number of subscriber units accessing the system. Depending on the 

number of talk group assignments, monthly fees may be as low as $24.00 a month. 

Federal agency participation in the 1CommWireless system is relatively small compared 

to the overall federal government radio equipment usage in the Washington/Baltimore area. This 

is because there are large government owned and operated systems in the area that were in 

operation before the 1CommWireless system became operational in 1990.

5.4.7 Integrated Wireless Network (IWN) 

The U.S. House of Representatives, Committee on Appropriations Report addressed the 

issue concerning narrowbanding of the current DOJ land mobile systems. Specifically, it was 

noted that any DOJ narrowband conversion initiative must be based upon a comprehensive 

strategy, which achieves as one of its goals “maximized efficiencies and savings through shared 

infrastructure and common procurement strategies.”57 To increase spectrum efficiency and 

maximize the limited spectrum resources available to federal public safety agencies, DOJ, DHS, 

and Treasury are developing the IWN to address the needs of the numerous bureaus and agencies 

within their departments. The IWN will provide national coverage through hybrid LMR 

systems, which will consist of both trunked and conventional digital narrowband equipment. 

Overall spectrum planning and support activities critically influence the IWN network 

design through four distinct phases. 

1. Phase 1 – Existing Capabilities Survey. In this phase, existing users within the scope 

of the IWN project design area are identified and defined by Operations and 

Engineering, and then characterized in accordance with their legacy system 

operational capabilities, coverage, and requirements. 

2. Phase 2 – Operational Requirements Definition. In this phase, user requirements 

anticipated to be supported by the IWN network are specifically defined by 

Operations. This phase is critical in determining the overall spectrum resources 

necessary for support of IWN network operations. 

3. Phase 3 – Frequency Selection and Assignment Processing. The third phase involves 

detailed identification and formal coordination/processing of the specific frequency 

assignments required for site operations within the IWN. 

4. Phase 4 – Operational Transition/Implementation. The final phase of spectrum 

planning and transition activities within the IWN is heavily predicated on the 

 

57 Departments of Commerce, Justice, and State, the Judiciary, and Related Agencies Appropriations bill, Fiscal 

Year 1999, H.R. Rep. No. 105-636, at 12 (July 20, 1998). 
5-9

availability of the selected frequency resource to support the network’s overall 

operation channeling requirements. 

Once the planning phases are concluded, an initial pilot test project will be conducted in 

the State of Washington. The IWN will be based on digital technical standards that maximize 

the use of the available spectrum and will be P25/TIA 102 compliant. The IWN is planned to 

increase spectrum efficiency through shared infrastructure and utilizing digital narrowband 

technology. The system will also provide economies of scale through common procurement 

strategies. 

With limited spectrum resources in the 162-174 MHz and 406.1-420 MHz bands, more 

federal public safety agencies are looking at IWN-type systems to maximize the use of spectrum 

resources to meet the increasing spectrum demands of their agencies. 

5.4.8 United States Department of Defense Trunked Network 

The Department of the Army is planning to implement a P25/TIA-102 compliant, voice 

over internet protocol (VoIP) capable, digital narrowband trunked system in the 380-400 MHz 

band. The Regional Concept 2005+ plan is to expand the system region-by-region to eventually 

connect military installations throughout the United States. Most of the current operations using 

the 162-174 and 406-420 MHz bands will relocate to this new system. The system will be builtout in two phases. The first phase build-out will include Army installations within the National 

Capital Region (NCR) and the Military District of Washington (District of Columbia, Virginia, 

Maryland, and New York), along with a Navy system at the Navy Annex, Quantico Marine 

Base, Quantico, Virginia. The second phase build-out will include Navy and Air Force 

installations within the NCR. Dispatcher requirements will be controlled by digital consoles, or 

via mobile or base station assigned to each team or agency at the installation. The trunked 

system will be controlled from a central location by means of a Communications System 

Director, to facilitate collection of usage data, dynamic system configuration and 

reconfiguration, and control. Connectivity to the alternate zone and system controller main 

repeater site will be via T1, fiber, and hardwire over existing infrastructure, or constructed RF 

line-of-sight systems. Users will be comprised of DOD Operations, Defense Protective Service, 

fire departments, law enforcement center, medical, force protection, information management, 

administrative, public works, and Emergency Operations Center, training, and post support. The 

system is planned to employ cross band capabilities to allow interoperability with the multitude 

of federal, state, and local agencies in the area. 
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Page 5-10/Blank 
6-1 

SECTION 6

THE SIGNAL CAPACITY ANALYSIS PROGRAM (SCAP) 

6.1 GENERAL 

One of the first steps in designing future spectrum efficient radio networks for federal 

radio systems in the Washington, D.C. area is to understand how much service is needed, of 

which types, and in what locations. The SCAP is designed to process existing GMF data to 

provide this radio service information. Every federal agency using the radio spectrum must have 

frequency assignments (licenses) listed in the GMF for every transmitter in use. Therefore, the 

GMF should contain frequency records corresponding to all federal radio systems in use in the 

Washington, D.C. area. Moreover, these GMF records will usually contain sufficiently detailed 

technical information that the records can be analyzed to accurately estimate the coverage area of 

the selected assignments. For this Phase 1 study, the GMF data were analyzed for all 

assignments located within a 100-mile radius of Washington, D.C. for frequencies within the 

162-174 MHz federal land mobile band and supplemented with agency inputs. 

6.2 DEFINITION OF SIGNAL CAPACITY 

There are several ways to define the amount of “service” provided by a given radio system. 

These definitions need to reflect the type of service provided by the particular radio systems, e.g., a 

radar system would be defined by completely different factors than a mobile radio. Different service 

definitions would be assumed to provide different types of information, would present various 

difficulties in obtaining the required information, and would have different applicability to the problem 

of providing specifications for a future radio system. The definition of radio service selected for this 

work is called signal capacity (SC). The SC is defined as the number of independent 2-way voice 

radio channels that can be received by a mobile radio user at a given geographical location. Note that 

the definition includes the word “received” rather than a phrase like “used by.” The SCAP considers 

only base station transmitters and the geographical distribution of the field strength that they produce. 

This model is based only on the base-to-mobile signals that can be received by mobile users. The SC 

model includes no information about base station receivers, or any receivers whatever. However, any 

future radio system designed to meet the SC specifications produced by the SCAP would also need to 

meet suitable base station receiver functions (possibly including receive-only sites) and (probably) be 

capable of mobile-to-mobile operation. 

This SC definition is particularly useful for several reasons: 

1. The major service provided to federal users in the 162-174 MHz band is two-way voice 

channels to mobile users. Therefore, this definition captures most of the use in the 162-

174 MHz band. 

2. The SC is additive. This means that the SC produced by Agency X assignments can be 

added to the SC associated with Agency Y assignments to obtain a SC for both agencies. 
6-2 

3. The SC can be calculated from data that is available in GMF license records and 

technical models, including transmitter data, terrain/ground cover data, and propagation 

models. 

4. The SC could be used to design alternative future radio systems, which would provide 

coverage to various geographical areas, using a sufficient number of transmitter channels 

to match or exceed the respective SC values. 

However, the SC definition makes many simplifications that may limit its usefulness in 

specific circumstances. These include: 

1. There is no data on whether a given channel is lightly or heavily used. However, the 

existence of a radio channel used or not used suggests that the system was built for a 

reason, and that reason still must be presumed to exist when a future system is built to 

replace the existing radio system. 

2. All voice channels are considered identical, whether analog or digital, narrowband or 

wideband, simplex or duplex, high priority or low, etc. Equally important, SC only 

considers the radio link, with no distinction as to what capabilities are available via that 

link: data, encryption, database access, telephone access, wide area access, etc. For the 

purpose of SC, “a channel is a channel is a channel.” 

3. Only permanently sited transmitters (and their corresponding coverage areas) are 

considered here; all receiver assignments and mobile transmitters are ignored. Future 

studies on designing replacement systems will also need to duplicate receiver coverage 

specifications (e.g., receive-only sites etc.). It is assumed mobile transmitters would 

probably not be replaced by a new permanent infrastructure. Therefore they do not need 

to be included. 

4. Many assignments include multiple station classes, different emission designators, and 

different transmitter powers. The SCAP analyzes the highest power signal from these 

multiple sets of specifications, giving the largest possible coverage area. In some cases, 

the assignments may authorize the use of transmitter power higher than the actual 

transmitter power installed. 

5. A single coverage criterion is used with SCAP, although various agencies may require a 

variety of coverage definitions. For example, some agencies may require high-reliability, 

in-building access to portable receivers, while other agencies may accept less reliable 

rural access via outdoor vehicular radios. A single criterion of 10 microvolts/meter 

(μV/m) with 50 percent confidence and 90 percent reliability was selected to define 

coverage.58

 

58 See Appendix A, at A-2, for a detailed explanation of the threshold and confidence/reliability criteria. 
6-3 

In summary, although the SC may not provide an exact measure of the service that a 

radio system (or a set of radio systems) produces, it provides a fairly realistic measure of service 

in the 162-174 MHz band that can be calculated. The SC is a particularly useful measure, 

because radio systems can be relatively easily designed to match or exceed a given SC, with a 

reasonable assurance that a new full-featured radio system (e.g., a trunked system) would 

reliably match or exceed most realistic performance measures of the current system. 

6.3 BASIC SCAP ANALYSIS 

The SCAP performs its analysis in several stages. Additional details are available in 

Appendix A. The first stage includes reading a modified version of the GMF, which has been 

sorted to include assignments in the 162-174 MHz band within a 100-mile radius of Washington 

D.C. In addition, each assignment record has been augmented with a function code that tells 

SCAP how each assignment record is to be analyzed. The function code includes a 

determination of function and network identification. Since the analysis for each network is 

performed independently, SCAP must first identify all transmitters belonging to each network. 

A network is defined as any related set of transmitters that are part of an integrated system or 

network following a uniform set of SC rules. In general, a minimal network includes a single 

transmitter. Other networks can include a simulcast system with 15 sites and ten frequencies at 

each site. 

The SCAP uses the GMF assignment data for each transmitter assignment to obtain 

antenna and transmitter data, which is used with a terrain-based propagation program to compute 

predicted field strengths from that transmitter. The field strength predictions are combined with 

receiver sensitivity data to predict a coverage area for each transmitter; all field strengths higher 

than a certain threshold are assumed to provide coverage (service) for mobile users. The 

predicted coverage is calculated at one-mile intervals to show coverage over a 200-mile square, 

centered on Washington, D.C. 

The SCAP uses the basic coverage information to calculate a pair of peak and average SC 

maps for each network, following the specific algorithms for each function code, as described in 

Appendix A. The peak SC and average SC maps for each network can be combined to give 

similar paired peak and average SC maps for multiple networks by simply adding the 

corresponding elements representing peak or average SC at respective geographical locations. 

The peak and average SC maps can continue to be added together to obtain peak and average SC 

maps for various larger groups of networks. Continuing the process of addition, coverage maps 

for groups of networks for individual agencies can become coverage maps for whole 

departments, and ultimately, the entire federal government. 

The SC maps are calculated at one-mile intervals for all locations over a 200-mile square 

area. However, the GMF database used for these calculations included only GMF records for 

systems located within a 100-mile radius circle, centered on Washington, D.C. Therefore, there 

can be some substantial “edge” affects in this modeling. For example, a transmitter located just 

outside the 100-mile radius circle would not be included in the model at all, even though it could 

have a substantial portion of its coverage area inside the area of the map. Furthermore, a 

transmitter just inside the circle would be included in the model, but part of its coverage area 
6-4 

could lie outside the calculated area of the square map. This reduction in the apparent size of its 

coverage area could affect the numbers in the average SC maps. 

The use of a 200-mile square represents a compromise between performing the study 

using a larger square, which would require more extensive analysis, and using a smaller square, 

which would cause the edge effects to be relatively greater. A 200-mile square will produce 

minimal distortions in the immediate Washington, D.C. area, though the distortions could be 

larger near the edges of the map. 

6.3.1 Peak and Average Signal Capacity Maps 

Although the SC was defined initially at a given location, it is convenient to summarize 

the SC at many adjacent locations as a contour map, using colors or contour lines to identify 

areas that have 

certain ranges of SC 

values. Figure 6-1 

shows examples of 

four maps from 

single transmitters 

sited at Alexandria, 

Greenbelt, 

Hazlettville, and 

Preston. Each map 

shows geographical 

areas of coverage 

from each 

transmitter. The 

quantity plotted in 

these maps is called 

a “peak” signal 

capacity (PSC) map 

to distinguish it 

from an “average” 

signal capacity 

(ASC) map 

described later. The 

maps produced in 

this study are 

generated by 

calculating predicted 

field strength at one-mile intervals over a 200-mile square centered around Washington, D.C. 

The calculation uses transmitter and antenna data obtained from the respective GMF files. The 

terrain-based Longley-Rice propagation model is used in the analysis, with “coverage” defined 

as all locations with field strength in excess of 10 μV/m. The shaded areas of the maps indicate 

coverage from the associated transmitter. Since only one transmitter is present in each of these 

examples, every point on the maps will have coverage from either one or zero transmitters, (i.e., 

Figure 6-1. Peak Signal Capacity Coverage Map Examples 
6-5 

SC values of either zero or one, representing no coverage, or coverage by one transmitter). The 

effect of terrain is visible in enhancing or shadowing the coverage areas. The PSC map can be 

understood as showing the maximum number of independent users that could be simultaneously 

served at any given location, assuming that no other users were being served at other locations. 

An ASC map, as shown in Figure 6-2, can also be created. The ASC map shows the 

maximum number of independent users per square mile that can be served at one time if users 

were distributed evenly across the coverage area of a transmitter. The ASC map for an 

individual transmitter is determined by calculating the PSC map, totaling the number of square 

miles of coverage for 

that transmitter, and 

dividing the PSC 

values by the total 

coverage area. 

This computation 

means that the ASC 

map values at each 

location will be 

expressed in terms of 

users per square mile 

that the transmitter 

could provide service 

to, assuming that 

users were evenly 

spaced across all of 

the transmitter 

coverage area. 

Integrating the ASC 

values across the 

entire coverage area 

of one transmitter will 

give a total of exactly 

“one user.” Figure 6-

2 shows an ASC 

map of the same 

transmitter whose 

PSC map was shown in Figure 6-1. Specifically, Hazlettville, in Figure 6-1, shows radio 

coverage of about 2,500 square miles (out of a total of 40,000 square miles included in the map). 

Therefore, the ASC map shows that this transmitter would provide coverage to about .0004 users 

per square mile, if the users were evenly distributed over the whole 2,500 square mile area of 

coverage, (2,500 mile squared x .00014 users/mile squared = 1 user). As a convenience in 

reading the ASC maps, the actual ASC values in this report have been multiplied by 10,000 

before they have been plotted, so that .0004 is plotted as “4”. This gives values that are easier to 

read and relate to PSC values. Note that a smaller transmitter coverage area gives larger ASC 

values on the map. The Preston transmitter in Figure 6-2 has a noticeably larger coverage area, 

Figure 6-2. Average Signal Capacity Map Examples 
6-6 

but the lighter shade corresponds to a plotted ASC value of around “2”, a number only about half 

as large as the ASC values corresponding to the other three transmitters. 

Both the previous ASC and PSC map examples describe use by one independent user. 

This does not imply that only one individual user can actually be served by the system at a given 

time. The independent user may be a talk group with a hundred members that are 

simultaneously receiving a common message. More likely, the one independent user would be 

several talk groups, each with multiple users, who time-share the single radio channel among 

themselves. The only constraint among the multiple users in each of the multiple talk groups is 

that only a single message can be carried by the radio channel at one time. Likewise, the one 

independent user could actually be a single user. 

The PSC map and the ASC map provide two different methods of looking at the problem 

of providing service, based on different assumptions about how users are distributed 

geographically. The PSC map assumes that all users may be concentrated at the same 

geographic location. The ASC map assumes that users are evenly distributed across the coverage 

area of their respective base station transmitters. In analyzing the SC that is provided by an 

existing transmitter, it is not known whether that transmitter was intended to serve users who are 

statistically evenly distributed across the coverage area or users that are usually located in one 

small portion of the coverage area. Lacking this specific information for each transmitter, the 

analysis covered the extreme cases by calculating both the PSC and ASC maps. In many ways, 

the PSC and ASC maps represent the worst and best cases of user geographical distributions, 

respectively. Real-world user distributions presumably must lie somewhere between these two 

extremes, but it is not necessarily clear exactly where. Nevertheless, the PSC and ASC maps 

place bounds on the effects of user location. 

If all transmitters had the same coverage area, the PSC and ASC maps would look 

identical, except for a scaling factor related to the coverage area of the transmitters. However, if 

transmitters with one coverage area are replaced with future transmitters having a different 

coverage area, the assumptions about whether replacement transmitter requirements scale 

proportionally to coverage area or not become very important, since these two different 

assumptions give much different results. ASC values scale proportional to coverage area; 

designing a new system with micro cells having ten percent of the coverage area of current 

transmitters would result in designing the micro cells to handle ten percent of the traffic. PSC 

values do not scale with coverage area. A ten percent-sized micro cell would still need to handle 

all of the traffic of the standard transmitter, since it is possible that all of the users from the 

standard cell may sometime be crowded into that single micro-cell. Therefore, both sets of maps 

are important as a more complete basis for designing a range of possible alternative radio 

systems to match the current capabilities of users in the 162-174 MHz band. 

Although PSC and ASC maps show the coverage of individual transmitters, they are 

particularly useful because individual SC maps for individual transmitters can be combined with 

SC maps of other transmitters to get SC maps corresponding to groups of transmitters. In 

particular, the PSC map values at a given geographic location from one transmitter can be added 

to the PSC map values at the corresponding geographic locations for another transmitter to 

produce a PSC map for the combination of the two transmitters. Similarly, the ASC map values 
6-7 

for one transmitter can be added to corresponding ASC map values for another transmitter, on a 

point-by point basis to obtain an ASC map for the two transmitters. 

In similar fashion, PSC maps for a few transmitters can be added together to give PSC 

maps for arbitrarily large numbers of transmitters. Thus, PSC maps can be obtained for specific 

commands, whole agencies, or whole departments, or even the entire set of users in the 

Washington, D.C. area. Similarly, the individual ASC maps can be combined to give ASC maps 

for arbitrarily large groupings of transmitters. 

6.3.2 The Use of Function Codes to Define Signal Capacity of Networks 

Although the previous descriptions of ASC and PSC maps have discussed single 

transmitters, the lowest level of radio system that can actually be analyzed to produce PSC or 

ASC maps is not a single transmitter but is instead a “network.” A network is a group of 

transmitters (one or more) designed to produce a specific type of service over a given area. In 

many cases, a network contains only a single transmitter. The concept of network must be used 

to compute SC because, in many systems, the use of one transmitter constrains how other 

transmitters can be used. For example, if one simulcast transmitter is transmitting a signal, no 

other simulcast transmitter on that channel can be simultaneously used to transmit a different 

signal. Thus, the ability to receive an independent signal at one location is dependent on what is 

happening at another location. The network, as defined here, is the smallest set of transmitters 

that must be included in the SC calculations to obtain an accurate value. Once the ASC and PSC 

maps for a network have been properly calculated, these values are independent quantities and 

SC maps from one network can be freely combined with SC maps for other networks. 

The SCAP uses the GMF frequency database as a source of technical information about 

LMR transmitters in the 162-174 MHz band. A function code (F, N) is added to each GMF 

assignment record that provides additional information needed by the SCAP. The parameter F 

shows SCAP what type of technology the network uses (i.e., what set of algorithms to use to 

compute SC maps). Different algorithms are needed for independent base stations, repeaters and 

multi-site repeater systems, simulcast systems, trunked base stations and multi-site systems, and 

others, as described in Appendix A. The parameter N shows what other transmitters to include 

in this analysis. All transmitters with the same N identifier belong to the same network. 

Transmitters are often assigned as individual equipments, but the SCAP needs to perform 

calculations on groups of transmitters (networks) therefore the “network” function codes are 

used to enable this required grouping. A more detailed description of the specific types of 

networks and the associated SC algorithms are given in Appendix A. 
6-8 

The function codes were determined by a study of the GMF records and consultations 

with frequency management staff at the various federal agencies. The function code 

determinations are only for purposes of SCAP 

analysis and no actual changes were made to 

any GMF records. Some GMF records did not 

fit exactly into the functional categories that 

were established. Consultations were made 

with agency staffs to attempt to get the closest 

possible fit. 

Figures 6-3 and 6-4 provide an 

example of the SCAP analysis of a basic 

network, showing how different types of 

networks give different PSC and ASC map 

results, in a network that consists of a group of 

four base stations. These four transmitters 

will be analyzed as a simulcast network and as 

a network of single-channel trunked radio 

systems. 

The PSC map for the simulcast system is 

shown in Figure 6-3 and the PSC map for the 

trunked radio system is shown in Figure 6-4. 

The simulcast system PSC map was created 

by first calculating the coverage areas of each 

base station and placing a “1” at each location 

where coverage was available from any of the 

four base station transmitters. In locations 

where coverage is available from more than 

one base station, the PSC for the simulcast 

system is still “1,” since all base stations 

transmit an identical message, so only one 

independent message can be received at any 

location. This PSC simulcast system map 

functions as though the radio system were a 

single transmitter with a very large coverage 

area, with a single color shade and a PSC 

value of “1” at all locations that get coverage 

from one or more transmitters. 

Figure 6-4 shows the PSC map for the 

same four sites analyzed as trunked sites. A 

four-site trunked radio system using 

independent frequencies to provide coverage from each transmitter site could provide 

independent messages from each site. Therefore, in all locations where coverage is available 

from multiple base stations, the PSC values add together to equal the number of different sites 

Figure 6-3. PSC Map for Four Transmitters Analyzed 

as a Simulcast System 

Figure 6-4. PSC Map for Four Transmitters Analyzed as a 

Trunked System 
6-9 

from which coverage is available. As shown in Figure 6-4, some locations get independent 

coverage from as many as three of the transmitter sites. The darker shading represents the larger 

PSC values. 

The average SC value is determined 

by dividing the PSC at a specific location by 

the area over which each transmitter 

provides coverage. In the case of a 

simulcast system, the entire four-site 

simulcast coverage area resembles what the 

coverage area of a single transmitter that 

covers a very large area would look like. 

Therefore, the simulcast system ASC map, 

Figure 6-5, looks identical to the simulcast 

PSC map, except for a scaling factor that 

shows a single relatively low average 

number of independent users per square mile 

that can be served by the simulcast system. 

Figure 6-6 shows the ASC map for 

the four sites analyzed as trunked sites. The 

ASC values for the four base station trunked 

network is calculated by finding the ASC 

values for each base station on an individual 

basis, and adding the individually calculated 

ASC values at points where coverage is 

available from multiple stations. In this 

case, the transmitters operate independently, 

so the coverage area is the respective area 

for each separate transmitter. Since each 

transmitter can serve a different population 

of independent users, the ASC values add 

together where coverage is available from 

multiple transmitters. 

Therefore, PSC and ASC are 

different for the four-site simulcast network 

and the four-site trunked network. The peak 

usage per simulcast channel would be one 

independent user per channel over the entire 

four-site area. The peak use per trunked 

channel would be one independent user per 

channel at many points, but there would also 

be locations that may provide service to two 

to three independent users, due to overlapping coverage areas from multiple sites. 

Figure 6-5. ASC Map for Four Transmitters Analyzed as 

a Simulcast radio System 

Figure 6-6. ASC Map for Four Transmitters Analyzed as 

a Trunked Radio System. 
6-10 

The average number of independent users per square mile that the four-station simulcast 

system can support would be smaller than the number of independent users per square mile for 

the four-site trunked system for two reasons. First, there is only one independent signal available 

from the simulcast system, whereas the trunked system provides multiple signals in many 

locations. Second, the coverage area is larger for the simulcast system than for any of the 

individual trunked sites, so the ASC value for the simulcast system is smaller than the ASC value 

for any of the individual trunked transmitters. Therefore, the ASC values, the average number of 

independent users per square mile, are smaller for the simulcast system, at any given location, 

than for the corresponding location on the ASC trunked system map. 

The above analysis shows numbers that are based on independent users. An independent 

user can be a single user or a large talk group with hundreds of users as long as the talk group 

members all receive the same messages. Many public safety systems are not designed to support 

individual independent users, but are designed for talk groups containing many users spread 

across a wide area. Under these circumstances, large coverage areas are more important than 

being able to locally serve multiple independent users. Therefore, the apparent disadvantages of 

the simulcast system versus the trunked system may not be as great as shown in these numerical 

examples, when large talk groups spread across large areas are considered. 
7-1 

SECTION 7

FEDERAL AGENCY SIGNAL CAPACITY MAPS 

7.1 GENERAL 

This section contains the SC maps for various agencies and groups of agencies, resulting 

from a SC analysis of the Washington, D.C. area GMF data within the 162-174 MHz band. The 

basic concepts of PSC and ASC have been described in Section 6, with additional technical 

details included in Appendix A. Also described in that section, and in Appendix A, are the 

function and network codes used to convert GMF assignment files into SC coverage maps 

7.2 TECHNICAL PARAMETERS FOR SIGNAL CAPACITY MAPS 

The SC maps contained in this section were generated from data found in the November, 

2002 GMF files. The SC maps were developed from all assignments that are located within a 

100-mile radius centered on coordinates 38°54'34"N, 077°00'00"W, which corresponds 

approximately to the National Capitol building. Assignments located outside of the described 

100-mile radius circle were not included in the analysis, although the coverage areas of any 

included assignments were calculated over a square that is 200 miles on each side. This means 

that there are “corners” of the square that are outside the 100-mile radius circle where coverage 

from transmitter assignments located inside the circle were analyzed, but no GMF assignments in 

those corner areas were included in the SC modeling. No assignments located outside of the 

100-mile circle were included in the analysis, but transmitters would normally be found outside 

this circle and provide additional coverage to locations inside the circle. Therefore, there are 

expected to be “edge effects” near the outside of the circle where less-than-expected numbers of 

transmitters will be seen in the maps. The selection of a 100-mile circle was intended to result in 

a minimum level of edge distortion over most of the map, but especially in areas near 

Washington, D.C. 

The geographically selected GMF assignments were categorized using the function codes 

and network codes, according to how the respective assignment should be analyzed by the 

SCAP. Transmitters selected for inclusion in the SC modeling were analyzed to show their 

coverage areas. For this analysis, the terrain-based Longley-Rice propagation program was used, 

along with transmitter power, antenna, and location data from the GMF. The coverage analysis 

assumed that any location should be considered to have coverage if the 50-90 signal amplitude 

exceeded ten microvolts/m. This coverage criterion was chosen as a compromise between urban 

and rural coverage objectives, for a wide range of modulations and bandwidths. Appendix A 

provides a more detailed description of the model. 

Many GMF assignments incorporate multiple modulations, bandwidths, and transmitter 

powers. In this case, the highest transmitter power was used to calculate the coverage area, 

ignoring other differences based on modulation and bandwidth. 
7-2 

7.3 INTERPRETING THE SIGNAL CAPACITY MAPS 

The SC maps are designed to easily summarize the service that is provided by existing 

federal mobile radio systems in the 162-174 MHz band in the Washington, D.C. area. As 

described in Section 6 and in Appendix A, two different types of SC maps were needed to 

describe different aspects of SC. PSC maps show how many independent radio signals are 

available at any given location to a radio receiver at that location. Figure 7-1 shows an example 

of a PSC map for several selected federal radio systems. 

Figure 7-1 shows PSC values for all locations in a 200-mile square, centered around 

Washington, D.C. These values were calculated for locations spaced on a 1-mile grid. The color 

of the shading at every location indicates how many radio signals can receive at that location. 

Concentrations of radio signal coverage are located in the areas around Washington, D.C. In 

addition to certain cities, the map shows county and state boundaries, as well as major rivers and 

coastlines. 

Figure 7-1. Peak Signal Capacity Map 

for Several Federal Radio Systems
7-3 

The red shades on the map show that a mobile user in several high-signal areas can 

receive as many as 35 independent signals from various transmitters analyzed on this map. 

However, at many locations outside the high-signal areas, the white area shows that no signals 

would be available to a mobile user. At various in-between areas, a few (but not many) signals 

could be received by a mobile user. However, one “independent signal” does not mean that only 

one user at one location can receive the signal. Instead, a very large number of mobile users can 

be simultaneously listening to that one same signal at many locations across the map. 

In addition, the SC map does not show whether the “one signal” available at one location 

on the map is the same “one signal” that may be available at other locations on the map. In 

general, this ambiguity does not become troubling unless the required coverage is supplied by 

base stations placed at considerably different locations than the original base stations that were 

analyzed to produce the SC maps. Even assuming that different base station locations were used, 

one would generally expect that these SC map values would add up in different ways, some 

better, and some worse that would not result in systematic difference that would produce 

distorted results. However, consider the case where a specific existing base station was sited to 

provide coverage to a specific set of users operating in certain specific geographic areas. 

Changing base station locations in a potential future system might result in multiple base stations 

being required to provide coverage to all of the users who were covered before by a single base 

station. This could result in more future base stations being required than would normally be 

calculated. The magnitude of this effect is not known. 

Areas are considered “high-signal” because of the number of independent signals present, 

not because the signals are strong signals (i.e., high field strength). In fact, a small, high-signal, 

almost-vertical line west of Washington is probably the result of a number of relatively weak, but 

above the coverage threshold value, signals from Washington adding to a number of the 

similarly weak signals coming from the Hagerstown/Fort Royal area. Thus, the vertical line 

shown in Figure 7-1 is composed of a large number of weak signals. 

The effects of terrain are clearly seen in the maps. For example, near the lower, left-hand 

corner of the map is a diagonal line of higher-signal locations. This is caused by locations in 

high mountains receiving usable levels of signal from many distant radio base stations. Similar 

effects are seen from many mountain ranges scattered over the land, but not at locations over the 

ocean. 
7-4 

This specific PSC map was produced as part of a 5-step process: 

1) the various assignments (or agencies) to be included in the map were identified from 

the GMF, 

2) the assignments were categorized and coded for function/technology (by attaching a 

specific function and network code to each assignment), 

3) the coverage area was independently calculated for each transmitter in a network, 

4) PSC maps for each network were assembled from the transmitter coverage maps 

according to the applicable function codes for that network, and 

5) PSC maps for each network were combined into a PSC map for the agency or group 

of agencies. 

The particular assignments included in this example were selected mainly to show 

multiple “high-signal” areas, terrain effects, and low signal rural areas. 

Although the PSC map shown in Figure 7-1 provides much useful information for 

visualizing how many signals could be seen by a mobile user, this information is not necessarily 

the most useful information for designing future alternative mobile radio systems. The most 

useful type of system design information is usually in the form of the number of users per square 

mile that could be served by a radio system. This type of data is provided by ASC maps. The 

ASC map corresponding to the PSC map shown in Figure 7-1 is shown in Figure 7-2. 

As with the PSC map, the ASC maps shows the number of “independent users” per 

square mile that current systems can support. A single independent user represents a voice 

channel in use 24 hours a day. The actual number of users supported can be quite large, since 

many users could be distributed across a wide area and simultaneously listening to a common 

signal. In addition, multiple talk groups could be time-sharing that single voice channel, each 

talk group containing many users. 

The ASC maps were computed by following the same five steps that were used to 

compute the PSC map, except that a different algorithm was used in step 4. The algorithm 

followed in step 4 calculated the total effective area of a network and divided the PSC value at 

each location by area (in square miles) of the network coverage. This means that a network 

consisting of a single base station with a coverage area of about 36-mile radius would provide 

about 4,000 square miles of coverage. If there were a single transmitter at the base station, the 

PSC values for each point of coverage would be “1” at each location. The ASC values would be 

1/4000 at each location, or 0.00025. Note that the total number square miles of coverage times 

the ASC value gives the total number of independent voice channels on the map. 
7-5 

Although the PSC and ASC maps appear quite similar, there is a major difference in the 

numerical values that appear on the maps. Whereas the maximum PSC value is 35, the 

maximum ASC value is .0129. Since the ratio of these two values is about 2,600, this suggests 

that coverage area of the typical site is about 2,600 square miles, corresponding to a reception 

radius of about 29 miles. 

The ASC map shows how many independent users per square mile could be served by 

the mapped radio stations. The ASC data can be used when future systems are designed with 

base station sites whose calculated coverage areas are substantially different in size from the 

original system coverage areas. For example, if two alternative future systems were designed 

and System A employed base station sites having typical coverage areas equal to 4,000 square 

miles, while System B sites had coverage areas of 2,000 square miles, each site in System A 

would need to be designed to carry about twice as much total traffic as each of the System B 

sites. 

Figure 7-2. Average Signal Capacity Map for Several 

Federal Radio Systems 
7-6 

The ASC maps are computed by finding the total coverage area of a given transmitter and 

assuming that each independent transmitted frequency could support one independent mobile 

user. If one assumes that the one independent user is equally likely to be anywhere across the 

coverage area, on the average, the ASC map would show that the ASC value of average 

independent users per square mile is 1/A, where A equals the total coverage area in square miles. 

For example, if a particular base station with a coverage area of 3,000 square miles can 

support one independent user somewhere over that total coverage area, the average density of 

independent users over the entire 3,000 square miles would be 1/3000 independent user per 

square mile = 0.00033. If another base station site provided coverage over only 500 square 

miles, the average density of users for that site would be 1/500 user per square mile = 0.002. 

Note that a base station with a small coverage area provides ASC maps having larger average 

user density values. The summation of average SC (user density) over a single transmitter 

coverage area = 1 (i.e., one user). 

Note that a single independent user can consist of many actual users spread randomly 

across the coverage area (as long as all users are listening to the same message). Moreover, the 

users could include members from multiple talk groups, each talk group using the radio channel 

at different times, as long as the total duration of the multiple messages was less than 100 percent 

of the time. 

The ASC values from a single channel or a single site add to ASC values from other 

channels or other sites, depending on whether the additional channels or sites contain 

independent message content. In the case of overlapping coverage from semi-independent sites 

(e.g., multi-message repeater networks, see Appendix A.), the ASC values are calculated first as 

though there were no overlapping. Then, the ASC values are averaged together in any areas of 

overlapping coverages. As with the PSC maps, the ASC maps for agencies and larger groups of 

assignments are produced by adding the ASC maps values for one network to the ASC map 

values for other networks on a point-to-point location basis. 

Most ASC maps will closely resemble the corresponding PSC maps, except for a 

proportionality factor, P, which will be fairly constant over the entire map. If P = PSC 

value/ASC value at any given location, the value of P should be the approximate size of the 

coverage area of typical base station transmitters in that area. Therefore, the value of P should 

change over the map mainly if an agency uses different technologies or design criteria for 

different geographical areas. For example, mountaintop repeaters could give large coverage in 

rural areas, but short-range, high capacity systems might be used in urban settings. 

A single color scale has been used to plot all of the ASC and PSC maps. This color scale 

was chosen to allow a quasi-logarithmic representation of the ASC and PSC numerical values, 

such that the colors will allow a useful differentiation of numerical values, whether a specific 

agency map has relatively large or small numeric values. This convention should aid in the 

reader being able to make a direct comparison in numeric values among the various agency 

maps. 
7-7 

In addition, since the ASC maps typically contain values that are 5,000-10,000 times 

smaller than the corresponding PSC maps, the ASC map numeric values have been multiplied by 

10,000 times before being plotted. This change was made to facilitate an understanding of the 

similarities and differences between the corresponding ASC and PSC maps. A common color 

scale, as used in the PSC maps, has also been used for all of the ASC maps. A white background 

indicates “zero” SC (no receivable signals) for both the ASC and PSC maps. 

7.4 SIGNAL CAPACITY MAPS FOR FEDERAL AGENCIES 

The following sections contain SC maps for various federal agencies. Each section is 

formatted in approximately the same way and contains approximately the same information. The 

agencies are mainly grouped by federal department and arranged in alphabetical order. The 

Army, Navy, and Air Force are grouped together under “Department of Defense.” Some 

agencies with less than 20 frequency assignments apiece are grouped together as “Other Federal 

Agencies.” 

In addition to the individual departments, three sets of maps were made for a combination 

of combined departments. These groupings include SC maps for all federal agencies, for all of 

the agencies associated with the new IWN and for all federal agencies minus the IWN agencies. 

These additional three groupings are assumed to represent several logical combinations of 

federal agencies that may be involved in building future shared trunked systems. 

Each agency/grouping includes a summary of assignment statistics for that agency. 

These assignment statistics show how many assignments were placed within each of the SCAP 

functional categories. Although wireless links (F = 4), simulcast stations (F = 5), and area 

assignments US/USA/US&P (F = 24) were included as potential categories of systems during the 

determination of SCAP function codes, no GMF assignments with these codes were identified 

for the Washington-area assignments. (In the case of “area-type” assignments, these assignment 

types were eliminated from the GMF assignments before the detailed function code 

determination was started.) Therefore, the function codes F = 4, F = 5, and F = 24 were omitted 

from the function code summaries for each agency. Table 7-1 provides the total number of 

agency assignments and their function codes that were used in the SCAP analysis and Table 7-2 

provides the total number of assignments and their function codes that were not used in the 

SCAP analysis. 

Table 7-1. Total Number of Assignments with Function Codes Included in SCAP 

Total assignments included in SCAP analysis 866 

Individual base station transmitter F = 3 247 

Trunked network F = 6 5 

Single-message repeater network F = 7 274 

Multiple-message repeater network F = 8 220 

Mobile/mobile user net F = 9 120 
7-8 

Table 7-2. Total Number of Assignments with Function Codes Not Included in SCAP Analysis

Total assignments not included in SCAP analysis 1079 

Obsoleted link F = 20 84

Dedicated link F = 21 333

Receiver F = 22 418

Receive-only station F = 23 180

Low power (10 mW or less) F = 25 28

Mobile-only replace by new system F = 26 36

The role of each agency is also described in general terms, with the expectation that this 

description may be useful in helping the reader to understand why the SC maps show more 

coverage at one location instead of others. 

The major features in each of the following sections are “agency” PSC and ASC maps, 

which are displayed for each agency, department, or group of agencies. 
7-9 

Analysis of the Signal Capacity Maps By Agency 
7-10 

7.4.1 United States Department of Agriculture (USDA) 

The locations of the USDA assignments within 100 miles of Washington, D.C. were 

shown previously in Figure 4-2. That figure shows two major transmitter concentrations, 

including national headquarter sites in and near Washington, D.C., and national forest sites west 

of Washington serving the Washington and Jefferson National Forests. The urban/headquarter 

sites will use P25 digital technology, while the rural national forest sites will use analog voice 

radios. 

The PSC and ASC maps corresponding to current assignments are shown in Figures 7-3 

and 7-4, respectively. The PSC map shows that USDA has a peak level of approximately 13, 

which indicates that there can be up to 13 individual signals concentrated around the USDA 

headquarters building in Washington, D.C. The second concentration of signals is in the area 

west of Washington, D.C., where up to three independent signals provide coverage in the 

national forests. A line of points of higher incidental coverage between Washington and the 

national forests occurs at high elevation locations, where the forest coverage is supplemented 

with occasional distant coverage from the Washington emitters. The ASC map shows the same 

concentration of signals that the PSC shows, but now represents a maximum average level of 

approximately .0080 signals per square mile of coverage. Table 7-3 provides the USDA 

assignments and function codes that were and were not included in the SCAP analysis. 

Figure 7-3. Peak Signal Capacity Map for U.S. Department of Agriculture 
7-11 

Table 7-3. U.S. Department of Agriculture Assignments and Function Codes 

Function Description # of Assignments

F = 3 Individual base station transmitter 11 

F = 6 Trunked network 0 

F = 7 Single-message repeater network 9 

F = 8 Multiple-message repeater network 0 

F = 9 Mobile-only user net 2 

Total included = 22

F = 20 Obsoleted link 0 

F = 21 Dedicated link 2 

F = 22 Receiver 12 

F = 23 Receiver-only station 0 

F = 25 Low power (10 mW or less) 0 

F = 26 Mobile-only (replaced by new system) 0 

Total not included = 14

Figure 7-4. Average Signal Capacity Map for U.S. Department of Agriculture 
7-12 

7.4.2 United States Coast Guard (USCG) 

The locations of the USCG assignments within 100 miles of Washington, D.C. were 

shown previously in Figure 4-4. That figure shows the major transmitter concentrations along 

the Chesapeake Bay, including the headquarter sites in and near Washington, D.C. The USCG 

currently uses wideband simplex systems, but all current radios have narrowband digital and 

analog capabilities. The USCG will be incorporating the 162-174 MHz band into their new 

Rescue 21 digital system. The PSC and ASC maps corresponding to current assignments are 

shown in Figures 7-5 and 7-6, respectively. 

The PSC map shows that USCG has a peak level of approximately 4, indicating that there 

can be up to 4 individual signals around the Baltimore Coast Guard Activity. The remainder of 

the USCG signals are individual sites along the Chesapeake Bay, which represents a PSC of 1. 

The ASC map shows the same concentration of signals that the PSC shows, but now represents a 

maximum average level of approximately 0.0028. A distinct difference, though, is the higher 

ASC in the area just south of Salisbury, Maryland. This is due to the coverage area being 

smaller, thus a higher ASC per square mile. Table 7-4 provides the USCG assignments and 

function codes that were and were not included in the SCAP analysis. 

Figure 7-5. Peak Signal Capacity Map for U. S. Coast Guard 
7-13 

Table 7-4. U.S. Coast Guard Assignment and Function Codes

Function Description # of Assignments

F = 3 Individual base station transmitter 9 

F = 6 Trunked network 0 

F = 7 Single-message repeater network 0 

F = 8 Multiple-message repeater network 0 

F = 9 Mobile-only user net 5 

Total included = 14

F = 20 Obsoleted link 0 

F = 21 Dedicated link 0 

F = 22 Receiver 0 

F = 25 Low power (10 mW or less) 0 

F = 26 Mobile-only (replaced by new system) 0 

Total not included = 0 0

Figure 7-6. Average Signal Capacity Map for U. S. Coast Guard 
7-14 

7.4.3 United States Department of Commerce (DOC) 

The locations of the DOC assignments within 100 miles of Washington, D.C. were 

shown previously in Figure 4-3. That figure shows the concentrations for the two line offices 

that use this band; the National Institute of Standards and Technology (NIST), with its heaviest 

concentration around Gaithersburg, Maryland, and the National Weather Service, which is 

located primarily in the mountainous area west of Washington, and other sites located around the 

area. DOC currently uses wideband analog radios, but will be transitioning to analog 

narrowband. The PSC and ASC maps corresponding to current assignments are shown in 

Figures 7-7 and 7-8, respectively. 

The PSC maps show the largest peak usage of approximately 9 individual signals around 

the Washington, D.C. and Gaithersburg, Maryland areas. Some other notable remote areas have 

PSCs as high as 5. This is most probably due to the higher elevation of mountain locations 

picking up incidental signals from the Gaithersburg transmitters. The ASC map shows the same 

concentration of signals as the PSC map but results in an average of 0.0028 signals per square 

mile. Table 7-5 provides the DOC assignments and function codes that were and were not 

included in the SCAP analysis. 

Figure 7-7. Peak Signal Capacity Map for U.S. Department of Commerce 
7-15 

Table 7-5. U.S. Department of Commerce Assignments and Function Codes 

Function Description # of Assignments 

F = 3 Individual base station transmitter 9 

F = 6 Trunked network 0 

F = 7 Single-message repeater network 0 

F = 8 Multiple-message repeater network 1 

F = 9 Mobile-only user net 1 

Total included = 11

F = 20 Obsoleted link 0 

F = 21 Dedicated link 172 

F = 22 Receiver 0 

F = 23 Receiver-only station 0 

F = 25 Low power (10 mW or less) 0 

F = 26 Mobile-only (replaced by new 

system) 

172 

Total not included = 172

Figure 7-8. Average Signal Capacity Map for U.S. Department of Commerce 
7-16 

7.4.4 United States Department of Defense (DOD) 

The locations of the DOD assignments within 100 miles of Washington, D.C. were 

shown previously in Figure 4-5. That figure shows that the assignments are spread out over the 

entire area. However, this is in relation to the various DOD facilities that are in and around the 

Washington area. DOD currently utilizes various systems in this band to support base security 

and fire, but there are plans to develop a joint service, digital narrowband trunked system in the 

380-400 MHz band. The PSC and ASC maps corresponding to current assignments are shown 

in Figures 7-9 and 7-10, respectively. 

The PSC map shows that DOD has a peak level of approximately 36. This is primarily 

concentrated around the Washington area due to the higher concentration of DOD facilities in 

close proximity to Washington. There are some higher capacity areas scattered northwest of 

Washington. This may be due to higher elevations receiving incidental signals from Washington 

and the surrounding area. The ASC map shows the same concentration of signals, except that 

the highest is in the northern section where it attains approximately 0.0228 signals per square 

mile. This could be due to smaller coverage areas. Table 7-6 provides the DOD assignments 

and function codes that were and were not included in the SCAP analysis. 

Figure 7-9. Peak Signal Capacity Map for U.S. Department of Defense 
7-17 

Table 7-6. U.S. Department of Defense Assignments and Function Codes 

Function Description #of Assignments 

F = 3 Individual base station transmitter 75 

F = 6 Trunked network 0 

F = 7 Single-message repeater network 9 

F = 8 Multiple-message repeater network 0 

F = 9 Mobile-only user net 24 

Total included = 108

F = 20 Obsoleted link 0 

F = 21 Dedicated link 39 

F = 22 Receiver 6 

F = 23 Receiver-only station 5 

F = 25 Low power (10 mW or less) 9 

F = 26 Mobile-only (replaced by new system) 0 

Total not included = 59

Figure 7-10. Average Signal Capacity Map for U.S. Department of Defense 
7-18 

7.4.5 United States Department of Energy (DOE) 

The locations of the DOE assignments within 100 miles of Washington, D.C. were shown 

previously in Figure 4-6. That figure shows that transmitters concentrate in the Washington, 

D.C. headquarters and Germantown, Maryland campus areas. DOE is currently operating with 

digital narrowband equipment for their force protection operations, with the rest of their systems 

being gradually changed over to analog narrowband. The PSC and ASC maps corresponding to 

current assignments are shown in Figures 7-11 and 7-12, respectively. 

The PSC and ASC maps are virtually identical in presentation. The maps show the 

highest peak of approximately 3, and highest average of approximately 0.0012 signals per square 

mile in the area between Washington and Germantown. Incidental signals are noticeable in the 

higher elevations northwest and west of Washington. Table 7-7 provides the DOE assignments 

and function codes that were and were not included in the SCAP analysis. 

Figure 7-11. Peak Signal Capacity Map for U.S. Department of Energy 
7-19 

Table 7-7. U.S. Department of Energy Assignments and Function Codes 

Function Description # of Assignments 

F = 3 Individual base station transmitter 0 

F = 6 Trunked network 0 

F = 7 Single-message repeater network 8 

F = 8 Multiple-message repeater network 0 

F = 9 Mobile-only user net 1 

Total included = 9

F = 20 Obsoleted link 0 

F = 21 Dedicated link 34 

F = 22 Receiver 0 

F = 23 Receiver-only station 0 

F = 25 Low power (10 mW or less) 2 

F = 26 Mobile-only (replaced by new system) 0 

Total not included = 36

Figure 7-12. Average Signal Capacity for U.S. Department of Energy 
7-20 

7.4.6 Federal Aviation Administration (FAA) 

The locations of the FAA assignments within 100 miles of Washington, D.C. were shown 

previously in Figure 4-7. That figure shows that the major transmitter concentration is in and 

near Washington, D.C., and Baltimore, Maryland. The FAA has a major nationwide 

communications system based on a regional concept that can tie all aviation and FAA support 

facilities together. The FAA will be replacing their older wideband system with a newer 

narrowband digital system. The PSC and ASC maps corresponding to current assignments are 

shown in Figures 7-13 and 7-14 respectively. 

The PSC shows that the highest peak signal is approximately 13. This is consistent 

throughout the Washington/Baltimore area. This is due to three major airports being located in 

relative close proximity to each other. There are some mid-level and lower concentrations 

closely surrounding the other regional airports in the study area. Incidental signals from the 

Washington area are present in the higher elevations to the west giving those areas a higher peak 

capacity than is supported by actual transmitters. The ASC map shows that ASC reaches level of 

approximately 0.0060 signals per square mile. Table 7-8 provides the FAA assignments and 

function codes that were and were not included in the SCAP analysis. 

Figure 7-13. Peak Signal Capacity for the Federal Aviation Administration 
7-21 

Table 7-8. Federal Aviation Administration Assignment and Function Codes 

Function Description # of Assignments 

F = 3 Individual base station transmitter 25 

F = 6 Trunked network 0 

F = 7 Single-message repeater network 16 

F = 8 Multiple-message repeater network 3 

F = 9 Mobile-only user net 2 

Total included = 46

F = 20 Obsoleted link 1 

F = 21 Dedicated link 22 

F = 22 Receiver 38 

F = 23 Receiver-only station 0 

F = 25 Low power (10 mW or less) 1 

F = 26 Mobile-only (replaced by new system 1 

Total not included = 63

 

Figure 7-14. Average Signal Capacity for the Federal Aviation Administration 
7-22 

7.4.7 United States Department of Interior (DOI) 

The locations of the DOI assignments within 100 miles of Washington, D.C. were shown 

previously in Figure 4-8. That figure shows the major transmitter concentration around the 

national headquarter sites in and near Washington, D.C. A lesser, but still notable peak signal 

concentration is noted around Washington, D.C. DOI is currently researching the feasibility of 

placing their law enforcement operations on a digital narrowband trunked system. Their other 

operations will convert to analog narrowband equipment. The PSC and ASC maps 

corresponding to current assignments are shown in Figures 7-15 and 7-16, respectively. 

The PSC map shows concentrations of up to approximately 24 signals in, and closely 

around, the Washington, D.C. area. Noticeable higher peak levels are also noted around the 

immediate Washington, D.C. area. These areas correspond to the national parks that reside in 

the study area. The ASC map shows that the ASC reaches approximately 0.0096 signals per 

square mile. Table 7-9 provides the DOI assignments and function codes that were and were not 

included in the SCAP analysis. 

 

Figure 7-15. Peak Signal Capacity for U.S. Department of Interior 
7-23 

Table 7-9. U.S. Department of Interior Number Assignments and Function Codes

Function Description # of Assignments 

F = 3 Individual base station transmitter 15 

F = 6 Trunked network 0 

F = 7 Single-message repeater network 12 

F = 8 Multiple-message repeater network 63 

F = 9 Mobile-only user net 4 

Total included = 94

F = 20 Obsoleted link 23 

F = 21 Dedicated link 5 

F = 22 Receiver 93 

F = 23 Receiver-only station 0 

F = 25 Low power (10 mW or less) 1 

F = 26 Mobile-only (replaced by new system) 36 

Total not included = 158

Figure 7-16. Average Signal Capacity for U.S. Department of Interior 
7-24 

7.4.8 United States Department of Justice (DOJ) 

The locations of the DOJ assignments within 100 miles of Washington, D.C. were shown 

previously in Figure 4-9. That figure shows the major transmitter concentration in Washington, 

D.C., with other transmitters “scattered” throughout the study area. DOJ is in the process of 

developing their next generation communication system, IWN. This system will be a pseudonationwide P-25 digital trunked system. The PSC and ASC maps corresponding to current 

assignments are shown in Figures 7-17 and 7-18, respectively. 

The PSC map shows that the PSC for DOJ is an almost linear decrease in peak signals 

moving out from Washington, D.C., with the highest concentration of signals, approximately 70, 

in Washington, D.C. The higher peaks in the diagonal line to the southwest are probably 

incidental signals received in the higher attitudes from the metro area. The ASC shows that DOJ 

reaches an ASC of approximately 0.0167 signals per square mile. Table 7-10 provides the DOJ 

assignments and function codes that were and were not included in the SCAP analysis. 

Figure 7-17. Peak Signal Capacity Map for U.S. Department of Justice 
7-25 

Table 7-10. U.S. Department of Justice Number Assignments and Function Codes 

Function Description # of Assignments 

F = 3 Individual base station transmitter 30 

F = 6 Trunked network 0 

F = 7 Single-message repeater network 139 

F = 8 Multiple-message repeater network 54 

F = 9 Mobile-only user net 12 

Total included = 235 

F = 20 Obsoleted link 52 

F = 21 Dedicated link 13 

F = 22 Receiver 191 

F = 23 Receiver-only station 175 

F = 25 Low power (10 mW or less) 4 

F = 26 Mobile-only (replaced by new system) 0 

Total not included = 435

Figure 7-18. Average Signal Capacity Map for U.S. Department of Justice 
7-26 

7.4.9 United States Capitol Police (USCP) 

The locations of the USCP assignments within 100 miles of Washington, D.C. were 

shown previously in Figure 4-11. That figure shows the major transmitter concentration is in 

Washington, D.C. area. The USCP currently uses a conventional wideband analog system. 

They will be replacing these radios with narrowband analog radios. The PSC and ASC maps 

corresponding to current assignments are shown in Figures 7-4 and 7-5, respectively. 

The PSC map shows the highest PSC of approximately 5 in the Washington, D.C. area. 

Some peak signals are evident to the west due to incidental signals being present at higher 

elevations. The ASC map is virtually identical map to the PSC, but shows the highest ASC to be 

approximately 0.0013 signals per square mile. The ASC is higher than would be expected due to 

the concentrated operating area of the USCP. Table 7-11 provides the USCP assignments and 

function codes that were and were not included in the SCAP analysis. 

Figure 7-19. Peak Signal Capacity Map for U. S. Capitol Police 
7-27 

Table 7-11. U.S. Capitol Police Assignment and Function Codes

Function Description # of Assignments 

F = 3 Individual base station transmitter 0 

F = 6 Trunked network 0 

F = 7 Single-message repeater network 14 

F = 8 Multiple-message repeater network 0 

F = 9 Mobile-only user net 5 

Total included = 19

F = 20 Obsoleted link 0 

F = 21 Dedicated link 0 

F = 22 Receiver 6 

F = 23 Receiver-only station 0 

F = 25 Low power (10 mW or less) 0 

F = 26 Mobile-only (replaced by new system) 6 

Total not included = 12

Figure 7-20. Average Signal Capacity Map for U. S. Capitol Police 
7-28 

7.4.10 United States Postal Service (USPS) 

The locations of the USPS assignments within 100 miles of Washington, D.C. were 

shown previously in Figure 4-12. That figure shows the major transmitter concentration in 

Washington, D.C. The USPS currently uses wideband analog radios but is in the processes of 

changing over to narrowband. The PSC and ASC maps corresponding to current assignments 

are shown in Figures 7-21 and 7-22, respectively. 

The PSC map shows a PSC of approximately 13 in and immediately around Washington, 

D.C. The peak level of three located to the north is due to a smaller number of transmitters in the 

Harrisburg, Pennsylvania postal facility. The higher peak levels that run in a diagonal line to the 

west of Washington, D.C. are most likely incidental signals in the higher elevations from 

Washington, D.C., and not representative of the actual transmitters supporting that area. The 

ASC map gives a virtually identical representation achieving an ASC of approximately 0.0072 

signals per square mile. This higher level is concentrated due to the use of in-building, small 

area coverage repeaters in the Washington, D.C., postal facilities. Table 7-12 provides the USPS 

assignments and function codes that were and were not included in the SCAP analysis. 

Figure 7-21. Peak Signal Capacity for U.S. Postal Service 
7-29 

Table 7-12. U.S. Postal Service Assignments and Function Codes

Function Description # of Assignments 

F = 3 Individual base station transmitter 16 

F = 6 Trunked network 0 

F = 7 Single-message repeater network 6 

F = 8 Multiple-message repeater network 0 

F = 9 Mobile-only user net 14 

Total included = 36

F = 20 Obsoleted link 0 

F = 21 Dedicated link 0 

F = 22 Receiver 5 

F = 23 Receiver-only station 0 

F = 25 Low power (10 mW or less) 0 

F = 26 Mobile-only (replaced by new system) 0 

Total not included = 5

Figure 7-22. Average Signal Capacity for U.S. Postal Service 
7-30 

7.4.11 United States Department of Treasury (Treasury) 

The locations of the Treasury assignments within 100 miles of Washington, D.C. were 

shown previously in Figure 4-10. That figure shows the major transmitters are in and around 

Washington, D.C., with smaller transmitter sites “scattered” throughout the study area. Many of 

Treasury’s bureaus were transferred over to the Department of Homeland Security and therefore 

will join the IWN with Justice. The PSC and ASC maps corresponding to current assignments 

are shown in Figures 7-23 and 7-24, respectively. 

The PSC map shows that Treasury’s PSC is almost a linear taper-off from Washington, 

D.C. throughout the whole area, while attaining a PSC of approximately 35. A noticeable 

concentration of SC can be seen around the capitol cities of Richmond, Virginia, and 

Wilmington, Delaware. The ASC map shows the same concentration of signals as the PSC and 

attains an ASC of 0.0129 signals per square mile. Table 7-13 provides the Treasury assignments 

and function codes that were and were not included in the SCAP analysis. 

Figure 7-23. Peak Signal Capacity for U.S. Department of Treasury 
7-31 

Table 7-13. U.S. U.S. Department of Treasury Assignments and Function Codes

Function Description # of Assignments 

F = 3 Individual base station transmitter 5 

F = 6 Trunked network 5 

F = 7 Single-message repeater network 38 

F = 8 Multiple-message repeater network 100 

F = 9 Mobile-only user net 17 

Total included = 165

F = 20 Obsoleted link 7 

F = 21 Dedicated link 13 

F = 22 Receiver 46 

F = 23 Receiver-only station 0 

F = 25 Low power (10 mW or less) 0 

F = 26 Mobile-only (replaced by new system 0 

Total not included = 66

Figure 7-24. Average Signal Capacity Map for U.S. Department of Treasury 
7-32 

7.4.12 United States Department of Veterans Affairs (VA) 

The locations of the VA assignments within 100 miles of Washington, D.C. were shown 

previously in Figure 4-13. That figure shows two major transmitter concentrations, including 

national headquarter sites in and near Washington, D.C., and a major VA facility in northeastern 

Maryland. The urban/headquarter sites will be changing over to the 1CommWireless system, a 

digital trunked system, while the other sites have already transitioned to analog narrowband 

radios. The PSC and ASC maps corresponding to current assignments are shown in Figures 7-25 

and 7-26, respectively. 

The PSC map shows that the higher peak signals of approximately 7 are more in the 

northeastern portion of the map. This is caused by an overlapping of transmitter signals from 

facilities in Pennsylvania, Maryland, and Delaware. The diagonal line to the west of Washington 

is most likely incidental signals in the higher elevations. The ASC map mirrors the peak map in 

that the highest average capacity of approximately 0.0036 signals per square mile is in that same 

area to the northeast. Table 7-14 provides the VA assignments and function codes that were and 

were not included in the SCAP analysis. 

Figure 7-25. Peak Signal Capacity Map for U.S. Department of Veteran’s Affairs 
7-33 

Table 7-14. U.S. Department of Veterans Affairs Assignments and Function Codes

Function Description # of Assignments 

F = 3 Individual base station transmitter 0 

F = 6 Trunked network 0 

F = 7 Single-message repeater network 5 

F = 8 Multiple-message repeater network 6 

F = 9 Mobile-only user net 6 

Total included = 17

F = 20 Obsoleted link 0 

F = 21 Dedicated link 7 

F = 22 Receiver 5 

F = 25 Low power (10 mW or less) 0 

F = 26 Mobile-only (replaced by new system) 0 

Total not included = 12

Figure 7-26. Average Signal Capacity Map for U.S. Department of Veterans Affairs 
7-34 

7.4.13 Other Agencies 

The category of “other agencies” includes several smaller agencies and other agencies 

with the majority of transmitters located in the immediate Washington, D.C. area. Their 

assignments were shown previously in Figure 4-14. That figure shows a few separate locations 

outside of Washington, D.C. Most the various agencies utilize various forms of analog 

wideband radios while some have already transitioned to narrowband analog or digital. The 

PSC and ASC maps corresponding to current assignments are shown in Figures 7-27 and 7-28, 

respectively. 

The PSC map show a large PSC, approximately 55, concentrated in and around 

Washington, D.C. This is indicative of the concentration of the various agencies conducting 

most, if not all of their LMR operations in and around Washington, D.C. There are some higher 

peaks to the northwest and west, but this is probably due to incidental signals at higher elevations 

from Washington, D.C., rather than being caused by actual transmitters. The ASC shows the 

same coverage pattern with the highest ASC at approximately 0.040 signals per square mile. 

This is a relatively large figure due to the majority of operations concentrated in the Washington, 

D.C. area. Table 7-15 provides the “other agency” assignments and function codes that were and 

were not included in the SCAP analysis. 

Figure 7-27. Peak Signal Capacity Map for “Other Agencies” 
7-35 

Table 7-15. “Other Agencies” Assignments and Function Codes

Function Description # of Assignments 

F = 3 Individual base station transmitter 45 

F = 6 Trunked network 0 

F = 7 Single-message repeater network 18 

F = 8 Multiple-message repeater network 27 

Total included = 90

F = 20 Obsoleted link 1 

F = 21 Dedicated link 26 

F = 22 Receiver 16 

F = 23 Receiver-only station 0 

F = 25 Low power (10 mW or less) 11 

F = 26 Mobile-only (replaced by new system) 0 

Total not included = 54

Figure 7-28. Average Signal Capacity Map for “Other Agencies” 
7-36 

7.4.14 All Federal Agencies 

PSC and ASC maps were developed to give an overall “picture” of what the total federal 

usage looks like in the study area. As with all the individual agency maps, the highest peak, 

approximately 268, and average, approximately 0.1000, center in and around the Washington, 

D.C. area. This stands to reason, as all the agency headquarters are located in D.C. The PSC and 

ASC maps corresponding to current assignments are shown in Figures 7-29 and 7-30, 

respectively. Table 7-16 provides all federal agencies assignments and function codes that were 

and were not included in the SCAP analysis. 

Figure 7-29. Peak Signal Capacity Map for all federal agencies 
7-37 

Table 7-16. All Federal Agencies Assignments and Function Codes

Function Description # of Assignments 

F = 3 Individual base station transmitter 247 

F = 6 Trunked network 5 

F = 7 Single-message repeater network 274 

F = 8 Multiple-message repeater network 220 

F = 9 Mobile-only user net 120 

Total included = 866

F = 20 Obsoleted link 84 

F = 21 Dedicated link 333 

F = 22 Receiver 418 

F = 23 Receiver-only station 180 

F = 25 Low power (10 mW or less) 28 

F = 26 Mobile-only (replaced by new system) 36 

 Total not included = 1079 

Figure 7-30. Average Signal Capacity map for all federal agencies 
7-38 

7.4.15 Integrated Wireless Network (IWN) (United States Departments of Justice, 

Treasury and Homeland Security) 

The PSC and ASC maps for this section are a combination of the agencies that will be the 

initial users of the IWN. These agencies will include: Federal Bureau Investigation (FBI), U.S. 

Marshall Service (USMS), Bureau of Prisons (BOP), Drug Enforcement Administration (DEA), 

Alsohol, Tobacco and Firearms (ATF), Customs and Border Protection, Immigration and 

Naturalization Services, General Services Administration (GSA), Transportation Security 

Administration(TSA), and the U.S. Secret Service (USSS). 

The PSC map shows that the main concentration of peak signals, approximately 84, is in 

close vicinity to Washington, D.C. The ASC shows the same properties, attaining a highest 

average capacity of approximately 0.0250 signals per square mile. Table 7-17 provides the IWN 

assignments and function codes that were and were not included in the SCAP analysis. 

Figure 7-31. Peak Signal Capacity Map for IWN Agencies 
7-39 

Table 7-17. IWN Assignments and Function Codes

Function Description # of Assignments 

F = 3 Individual base station transmitter 35 

F = 6 Trunked network 5 

F = 7 Single-message repeater network 149 

F = 8 Multiple-message repeater network 85 

F = 9 Mobile-only user net 24 

Total included = 298

F = 20 Obsoleted link 56 

F = 21 Dedicated link 27 

F = 22 Receiver 217 

F = 23 Receiver-only station 175 

F = 25 Low power (10 mW or less) 4 

F = 26 Mobile-only (replaced by new system) 0 

Total not included = 479 

Figure 7-32. Average Signal Capacity Map for IWN Agencies 
7-40 

7.4.16 All Federal Agencies minus IWN 

The last two maps represent the federal users in the study area minus the participants of 

the IWN. Once again, the highest peak, approximately 190, and average, approximately 0.0700, 

capacity signals are centered nearest Washington, D.C. This is primarily due to the various 

agencies’ headquarters being located within this area. Table 7-18 provides the Non-IWN 

assignments and function codes that were and were not included in the SCAP analysis. 

Figure 7-33. Peak Signal Capacity for Non-IWN Agencies 
7-41 

Table 7-18. Non-IWN Assignments and Function Codes 

Function Description # of Assignments 

F = 3 Individual base station transmitter 212 

F = 6 Trunked network 0 

F = 7 Single-message repeater network 125 

F = 8 Multiple-message repeater network 135 

F = 9 Mobile-only user net 96 

Total included = 568

F = 20 Obsoleted link 28 

F = 21 Dedicated link 306 

F = 22 Receiver 201 

F = 23 Receiver-only station 5 

F = 25 Low power (10 mW or less) 24 

F = 26 Mobile-only (replaced by new system) 36 

Total not included = 600

Figure 7-34. Average Signal Capacity Map for Non-IWN Agencies 
7-42 

Page 7-42/Blank 
8-1 

SECTION 8

SUMMARY OF FINDINGS 

The following section provides a summary of findings of the Phase 1 study that was 

based on a SCAP for the 162-174 MHz band in the vicinity of Washington, D.C. The SCAP 

produced results in terms of PSC and ASC contours maps for the various federal agencies. 

1. The SCAP was developed to provide a theoretical basis for understanding the services 

provided to federal LMR users in the 162-174 MHz band within a 100-mile radius of 

Washington, D.C. Radio services not provided by the fixed base station infrastructure 

were excluded from this study by assigning appropriate function codes. 

2. Data from the GMF, supplemented with information obtained from the agencies, 

allowed the SCAP to provide PSC and ASC maps for federal agencies in the 162-174 

MHz band in the Washington, D.C. area. These results can provide an improved 

understanding of federal LMR services, and can be applied in the design of possible 

future LMR systems with higher spectrum efficiency and effectiveness than current 

systems. 

3. Although SCAP provides a useful tool with which to compare the services provided by 

current and future systems, it does not provide any measure of absolute spectrum 

efficiency achieved by either system.

Table 8-1 provides a summary of the maximum PSC map values and the total number of 

transmitters included in the SCAP for each federal agency and some groups of agencies. The 

maximum PSC map value shows what the highest level of PSC was in the PSC map for each 

agency, e.g., a value of “35” indicates that some locations provided coverage for as many as 35 

separate radio channels. The “included transmitter” column shows how many LMR transmitters 

were included in the SC maps for each agency. Agencies with large numbers of radios and high 

PSC values included DOD, DOI, DOJ, and Treasury. These agencies had extensive LMR 

networks that could provide as many as 24-70 independent LMR channels in some locations. 

The All-Agency group contained a total of 866 transmitters and a maximum PSC map value of 

268. Even the group of IWN agencies had only about 35 percent of the total transmitters, with 

almost 65 percent of the remaining for the other agencies. This means that even the largest 

agencies represent only a small percentage of the total number of federal government 

transmitters. The increased scale of an all-agency operation could provide substantial 

advantages, if future systems provide meaningful economy of scale factors. 
8-2 

Table 8-1. Maximum Peak Signal Capacity and Included Transmitters

Agency Max Peak SC Map Value # of Included Transmitters 

Agriculture 13 22 

U.S. Coast Guard 4 14 

Commerce 9 10 

Defense 38 108 

Energy 3 9 

FAA 17 46 

Interior 24 94 

Justice 70 235 

U.S. Capitol Police 5 19 

U.S. Postal Service 13 36 

Treasury 35 165 

Other Agencies 55 90 

All Agencies 268 866 

IWN Agencies 84 298 

Non-IWN Agencies 190 568 

4. Many agencies have no coverage adjacent to the immediate Washington, D.C. area. 

Such agencies may gain much greater coverage, extending their coverage to 93 percent 

of all locations within the 200-mile square area that was analyzed, if they could share 

the existing LMR radio systems of other federal agencies. (Of course, it is also possible 

that many agencies do not need any coverage outside their current coverage areas.) 

Agencies with small numbers of users, but needing wide coverage would probably find 

it much less expensive to get the required service with some type of future shared 

system. Analysis of PSC data from the All-Agency map shows that 93 percent of 

locations had coverage from at least one transmitter, and 63 percent of locations had 

coverage from at least ten transmitters. Ten percent of locations had coverage from at 

least 100 transmitters, almost four percent of the locations had coverage from at least 

200 transmitters, and some locations received more than 265 transmitters. The few 

areas without any coverage were mainly in the corners of the map beyond the 100-mile 

radius circle, which may be largely due to “edge” effects inherent in the modeling. 

5. The SCAP encompasses only the base-to-mobile aspects of current radio systems. A 

future radio system, as a minimum, would need to duplicate the mobile-to-base and 

mobile-to-mobile capabilities of current radio systems. The base-to-mobile information 

provided by the SCAP model can help define the necessary corresponding mobile-tobase capabilities. However, the inferred mobile-to-base capability will need to be 

further studied to determine specific requirements (including in-building, portable 

coverage), so that the needed mobile-to-base capabilities can be completely included in 

the design specifications. 

6. Although the SCAP provides very useful information about the geographic locations 

where current radio services are provided to mobile radios, it provides no data showing 

where the served mobile users are located. A computed coverage area for a specific 

base station transmitter shows all of the locations where a mobile user could possibly 
8-3 

receive a usable signal, but it does not necessarily mean that the mobile users actually 

are located uniformly over the computed coverage area when they receive that signal. 

For example, a given transmitter located near the center of Washington, D.C. could be 

used solely to provide in-building coverage, (e.g., the four sub-basement parking levels) 

for buildings in the middle of the city, or it could possibly be used solely to provide 

coverage to mobile units operating in the distant suburbs. Since SCAP provides no clue 

as to which set of mobile users such a system is designed to serve, an alternative future 

system might be unnecessarily designed to serve both sets of users.

 

7. The SCAP analysis does not provide any information on the amount of radio traffic 

carried on each channel. Therefore, although it may be known that 23 independent 

radio signals are available at a given location, there is no information about how much 

of the time these 23 channels are actually used, or when the channels are used. This 

type of data could be obtained by measuring actual LMR radio traffic data, using 

equipment like the NTIA/ITS Radio Spectrum Measurement System (RSMS). 

8. The SCAP analysis (and the associated agency interviews) ensured that the analyzed 

LMR systems included no aspects of agency operation that would necessarily be 

disadvantaged by combining operations with other agencies, assuming that the required 

availability of service, reliability, response time, and protection of sensitive information 

could be provided by some future system. Technical functions of agency operation that 

could not be incorporated within the SCAP (e.g., mobile-to-mobile operation) were 

excluded from this analysis by the assignment of suitable function codes. Thus, it 

appears that the existing functions provided to agencies by the assignments included in 

the PSC and ASC maps could be provided by a future shared system. Whether such a 

future shared system could provide all of the desired features at a reduced cost, or with 

other advantages, remains to be seen. These details will be investigated in Phase 2 of 

the study. Similarly, the policy and managerial problems associated with possible 

future shared systems may not be trivial to resolve. 

9. The GMF, in its current form, did not always provide sufficient information to permit 

the assignment of function codes as an input to the SCAP model. Additional 

information on system operations was often required from the various agencies. 

10. There are various existing programs, initiatives, and studies on improving spectrum 

efficiency within the federal government. These programs will continue to provide a 

context within which future improvements to federal spectrum efficiency will need to 

adapt and conform. Such programs may be particularly important to consider in 

assessing the feasibility of various future LMR system designs proposed in Phase 2 of 

this overall study, as well as the scheduling and priority of the related studies. 

11. It is envisioned that the SCAP results developed for Phase 1 will help to quantify the 

advantages and disadvantages involved in a future radio system, as well as to provide 

insights to the best architectures and technologies to be employed and the 

circumstances under which maximum effectiveness would be achieved. 
8-4 
A-1 

APPENDIX A

DESCRIPTION OF SIGNAL CAPACITY ANALYSIS PROGRAM 

A crucial piece of the analysis of existing agency radio services is the determination of 

the current geographical SC of existing radio systems providing communications to existing 

federal mobile users. The resulting PSC and ASC maps will be the starting point for the design 

of several alternative future radio systems to be designed in Phase 2 of this study. Specifically, 

the PSC maps will show how many independent LMR channels can currently be received by 

mobile users, cumulatively, for all agencies, at any location within a 100-mile radius of 

Washington, D.C. The ASC maps will show how many average independent users per square 

mile can be supported by the current radio systems. It is assumed that any alternative future 

radio system that is capable of providing a similar, or greater, SC for all locations of the maps 

could be viewed as providing services that are equal to or greater than the services provided by 

current radio systems. The following section discusses, in detail, the computation algorithm for 

the SCAP. 

A.1 COVERAGE ANALYSIS OF CURRENT RADIO SYSTEMS 

In computing the SC maps for each network, the first step is to compute the coverage 

area for each included transmitter. This will require transmitter and antenna information that can 

be used to compute predicted signal strength as a function of geographical location, using a 

terrain-based propagation model. Any predicted field strengths in excess of an established limit 

may be presumed to constitute “coverage.” Since all of these network SC maps are intended to 

be added to other network SC maps, it may be useful to compute the field strength at a standard 

set of geographical locations, namely a fixed standard set of locations with 1-mile spacing over 

an approximate 100-mile radius centered on Washington, D.C. These geographical locations 

remain fixed at a standard set of locations, instead of being located relative to each transmitter 

location. 

 The field strength, S, from a transmitter can be calculated as: 

 S = P + G – R - L + 74.8 

 Where: S = field strength in decibels above 1 microvolt/meter (dB μV/m), 

 P = transmitter power in decibels above 1 Watt (dBW), 

 G = transmitting antenna gain in decibels above isotropic (dBi), 

 R = 20 log distance from transmitter (kilometers), and 

 L = Propagation loss (dB), compared with free-space. 

 

 The transmitter power and transmitting antenna gain, as well as antenna location and 

elevation, come from the GMF records. The propagation loss is calculated by using the 

Longley-Rice model with the required terrain data.59

 

59 National Telecommunications and Information Administration, U.S. Department of Commerce, NTIA Report 82-

100, A Guide to the Use of the ITS Irregular Terrain Model in the Area Prediction Mode (April 1982). 
A-2 

All systems will be analyzed to show coverage for a single field strength level of X μV/m 

for a certain percentage of locations and a certain percentage of time, assuming typical mobile 

radio parameters. For these coverage predictions, the terrain-dependent Longley-Rice model 

was used, giving predicted propagation path losses for 1-mile increments over a 200-mile square 

centered on Washington, D.C. The process of selection of proper parameters for field strength 

and percentages of time and locations is described in the next paragraphs. 

Proper coverage analysis parameters for this modeling effort would be best selected to 

reflect the functional/operational requirements of each of the respective radio systems. On this 

basis, a radio transmitter used to service handheld radios that may be used inside large office 

buildings and provide very reliable continuous service may require a field strength of 30-100 

μV/m outside the building. On the other hand, the need to intermittently maintain contact with a 

dispatcher at a maximum distance using a mobile transceiver might be accomplished with a 

signal level as little as 1 μV/m. Although there is a large difference between these two field 

strength requirements, it still may theoretically be possible to divide transmitters into categories 

that would show which field strength value should be used in the coverage analysis for each 

transmitter. However, the main purpose of the SC analysis is to develop a definition of coverage 

that is interchangeable between various systems. Otherwise, a future application of the SC data 

may attempt to provide a 1 μV/m signal to an operational mission that needed a 100 μV/m 

signal. Therefore, it was necessary to choose a single definition of coverage that could be used 

for all systems. 

In addition to the decision about field strength values, there are similar choices 

concerning the values of “reliability” and “confidence” associated with the field strength values. 

A propagation model like Longley-Rice provides predictions for mobile radio signal strength, S, 

from base stations in the form of: “There is a confidence of at least C percent that the received 

mobile radio signal will be above S μV/m for R percent of the time.” Since this propagation 

model is being applied to a mobile/portable system where it is assumed that the mobile unit is 

moving, the R factor (reliability) includes the effects of moving through time as well as moving 

across geography. Choosing a higher value for reliability (R) or confidence (C) has a similar 

effect to choosing a higher value of field strength (S) (e.g., at a given location, a confidence of 

getting at least a small signal with very high reliability almost all of the time). 

Figure A-1 shows the relative coverage areas of a group of transmitters, analyzed using 

different combinations of reliability, confidence, and field strength as the definition of 

“coverage” when generating these PSC maps. These 200-mile square PSC maps show how 

many transmitters can be received at each location on the map, using the same color scale on all 

maps to show the number of receivable transmitters. The PSC coverage maps are arranged in 3 

columns, having 4 rows each. The first column (left-most) was analyzed for a reliability of 50 

percent and a confidence of 50 percent for 4 different field strength values. The middle column 

was analyzed for a reliability of 90 percent and a confidence of 50 percent; the right-most maps 

to show the number of receivable transmitters. The PSC coverage maps are arranged in 3 

columns, having 4 rows each. The first column (left-most) was analyzed for a reliability of 50 

percent and a confidence of 50 percent for 4 different field strength values. The middle column 

was analyzed for a reliability of 90 percent and a confidence of 50 percent; the right-most 

column was analyzed for a reliability of 90 percent and a confidence of 90 percent. All three 
A-3 

columns were analyzed for identical field strength limits. The top row assumed that “coverage” 

required a signal of at least 1 μV/m, the second row assumed that “coverage” required a signal of 

at least 2 μV/m, the third row showed coverage based on 5 μV/m, and the bottom row was 

calculated for a coverage limit of 10 μV/m. 

Figure A- 1. 200-mile square coverage maps for selected transmitters, based on 50/50, 90/50, and 90/90 

(reliability/confidence) statistics for field strength of 1, 2, 5, and 10 μV/m. 
A-4 

In the preceding figures, the maps show that the coverage areas for a set of transmitters 

decrease greatly when the receiver/service requires higher reliability, higher confidence, or 

higher field strength. As described in the following paragraphs, the decision was eventually 

made to use a coverage criterion of reliability of 90 percent, confidence of 50 percent, and field 

strength of 10 μV/m. 

Initially, it should not make any difference which threshold value and statistics are 

selected, since the major purpose of the SC model is to assure that the coverage of the new 

system(s) is at least as good as the coverage of the current systems. As long as the old and new 

systems are tested with the same coverage parameters, use of exact values is not so important. 

Unfortunately, the preceding statement is not quite true. The problem is that the SC model does 

not “know” what is the intended use of a given radio system. If the intended use of a current 

radio system is to provide some coverage at large distances, the SC modeling should capture that 

use in its analysis, since that use will need to be provided in a future system. If the extended 

rural coverage is merely an unintended consequence of a transmitter intended to provide highly 

reliable in-building communication in urban areas, then the SC modeling should not include it 

and a future system should not need to provide it. If all the future systems used the same base 

station placement as existing systems to provide duplicate coverage, there would be less need to 

determine the intended coverage of transmitters, since duplicating the urban coverage would also 

tend to duplicate the rural coverage whether it was needed or not. However, since some of the 

alternative future systems will use different architectures and cell sizes, there is less assurance 

that close-in and distant coverage will be similarly related in old and new systems. 

The selection of a signal level near 1 μ/m was assumed to be inappropriate for several 

reasons. Many public safety personnel use portable handheld receivers, whose overall sensitivity 

in normal operating circumstances is likely to be as much as 3 μV/m. This high signal 

requirement is caused partly by less-efficient small antenna systems and partly by absorption and 

shielding by personnel holding the radio. The problems become even more pronounced when 

such handheld receivers are operated inside buildings, which can provide 10-30 dB of additional 

losses to radio signals. The general requirements of public safety personnel are to have higher 

reliability and availability of communications. Finally, the use of very low occupancy thresholds 

in analyzing current systems produced a strange anomaly. In some circumstances, the highest 

SC values occurred in rural locations where few users were present. The use of very low 

threshold values caused urban transmitters to produce “coverage” in some quite distant rural 

areas. In fact, there were some high-elevation rural locations where the weak signals from 

multiple distant urban areas could add together to produce coverage by total numbers of signals 

higher than in the core of any single urban area. Further analysis revealed that most urban 

transmitters were not installed with the intention of providing intermittent and unreliable 

coverage to large numbers of non-existent rural users. This “rural peak” effect seems to 

disappear for occupancy thresholds greater than 5μV/m. 

However, most rural service is delivered to public safety users with mobile radios or 

operating outdoors with handheld radios. Such situations can provide good reception with signal 

levels of less than 3 μV/m, though rugged terrain might produce deep signal shadows that often 

had much less signal than that. Since it seems reasonable to include any signal levels that could 
A-5 

be expected, to provide usable service to federal users, an amplitude level near 3 μV/m could be 

assumed as an appropriate coverage limit. 

After considering many factors, coverage was eventually defined by using a field strength 

of 10 μV/m, providing 90 percent reliability at a 50 percent confidence. This set of parameters 

corresponds to the bottom map in the middle column in Figure A-1. For simplicity, this 

definition was used for all radio technologies, even though some signal modulation technologies 

require more or less signal power for operation. The SC summary maps in Section 7 of this 

report were computed using the above definition for coverage. 

A.2 PEAK AND AVERAGE SIGNAL CAPACITY MAPS 

This section contains a description of the algorithms used to calculate the PSC and ASC 

maps for networks having various function codes. Note that some network types may have 

different function codes, but use the same algorithm for computing the SC network maps. These 

multiple function codes are useful because the function codes are also intended to be used later in 

summarizing various statistical changes in how frequencies are used and the different function 

codes will facilitate some of this future analysis. Two distinct types of SC maps will be done for 

each network: a PSC and an ASC map. These two representations of SC will place two types of 

bounds on the SC provided by current systems. The PSC map produces results that assume that 

all users might be concentrated into a single small geographical area. Alternatively, the ASC 

maps assume the most benign geographical distribution of users, with users spread out as evenly 

and uniformly as possible. The ASC maps provide “users per square mile” data that is intended 

to scale base station traffic proportional to the coverage area of a given base station. Under the 

ASC assumptions, a base station with ten percent of the coverage would be expected to carry ten 

percent of the traffic. Designs using PSC data would not scale with coverage area, since all of 

the possible users could be crowded into that particular ten percent of the coverage area. 

Any alternative future network would be required to assume some geographic 

distribution of users in its design. The calculation of both ASC and PSC maps provides two 

different extremes of rules, either of which might furnish a partial basis for new system design, 

but probably both should be used. Consider the implications of designing an alternative future 

system on the basis of ASC map values. Since the ACS values provide data on users per square 

mile, the design traffic loading on a given site would scale proportional with the area to which 

the site is providing coverage. If the new alternative system uses sites with the coverage areas 

smaller than current site coverage areas, the design traffic loading per site would be 

proportionally smaller than current traffic loading per site. However, if the future alternative 

design uses sites with larger coverage areas, presumably the new sites would be designed to 

carry proportionately larger traffic loads than the old sites. Under these conditions, the design 

criteria based on the ASC maps would be larger than the design criteria based on the PSC maps. 

Therefore, the PSC maps assume that the number of users does not change with coverage area, 

but remains constant with all possible users concentrated into a single location. Furthermore, a 

design based on the PSC maps would require a constant design site traffic load that would not 

change with coverage area of the site. This circumstance would require supporting the full PSC 

number of users within even very small cells, but the use of larger-than-current cells would 

require fewer channels based on PSC data than on ASC data. 
A-6 

Thus, the PSC and ASC maps represent the worst-case and best-case situations from the 

standpoint of designing alternative radio systems, depending on whether the alternative future 

systems use smaller or larger cells than the current systems. The exact design criteria that will be 

used to size possible future system designs is not yet known, but it must surely lie between these 

two bounding cases. The Phase 2 report on the design of possible alternative future systems will 

more fully consider this aspect of system design. 

SC maps are computed in two distinct stages. First, the PSC and ASC maps for 

individual networks are calculated using the GMF data, the function code and corresponding 

algorithms for that specific network, and applicable propagation models. Once the PSC and 

ASC maps have been calculated for a specific network, these maps can be combined and 

recombined on a strictly additive basis, without regard for the specific function codes that were 

originally used to compute the maps. PSC maps are combined with other PSC maps, adding 

numeric values on a location point-by-point basis to get a new cumulative PSC map. Similarly, 

ASC maps are combined with other ASC maps, adding numeric values on a location point-bypoint basis to get a new cumulative ASC map. Cumulative SC maps can be combined with other 

cumulative SC maps or network SC maps to get new SC maps representing more extensive 

combinations of assignments or agencies. 

The PSC will be determined by placing a “1” in each location where one signal from a 

base station can be received. If a base station has ten independent signals that can all be received 

at a given location, a value of “10” would be placed at that location. If a receiver at a given 

location could receive nine signals from one base station and seven different signals from 

another base station, a value of “16” would be put in that location. This network PSC map 

shows the peak number of independent signals that can be received at each location. When a 

cumulative PSC map shows the combined PSC for all the networks belonging to a single agency, 

the map would indicate the maximum number of independent signals that can be received from 

all networks belonging to that agency at each location. Similarly, when the PSC maps for each 

agency are combined to give a cumulative PSC map for all agencies, that map will contain 

numbers showing the maximum number of independent radio signals that could be received from 

all agencies at each location. PSC values will all be positive integers, possibly as large as several 

hundred. 

The ASC map is computed by normalizing the coverage area of a base station transmitter 

to give the average use per unit area (square mile) that could be obtained from a given 

transmitter. If a transmitter, “A,” has twice the coverage area of another transmitter, “B,” the 

average use per unit area for all areas of transmitter “A” coverage will be half of the average use 

of the transmitter “B” coverage area. The coverage area of a transmitter multiplied by the ASC 

value at each location of coverage will give a number that represents the total number of 

independent transmitters. The ASC value of a single transmitter is computed by modeling the 

coverage of that transmitter and putting a “1” at each location having coverage (note that this is 

identical to the PSC map for that transmitter). The total number of locations having a “1” are 

counted and placed into the value “K.” Since the computed locations are one mile apart, K 

represents the transmitter coverage area in square miles. Then the “1” at each coverage location 

is replaced with the value “1/K.” If a given base station had ten independent transmitters having 
A-7 

the same coverage area, the ASC map for that base station would have a value of “10/K” for the 

ASC at each coverage location. ASC values will tend to be small positive fractions, typically in 

the range of .000l to 0.1. However, to make it easier to read ASC maps, the actual ASC values 

plotted on the ASC maps have been multiplied by 10,000. This gives ASC maps values ranging 

between 0 and 600. 

The cumulative ASC map for all networks belonging to a single agency can be computed 

by adding the values at each corresponding geographical location from all of the ASC maps for 

each independent network for that agency. Similarly, the summary ASC map for all agencies 

can be generated by adding together the ASC values at each corresponding location for each of 

the summary ASC maps for each agency. If the values for every geographical location on the 

cumulative ASC map are summed, it will represent the total number of independent radio 

transmitters represented by the map, adjusting for the fact that the ASC map values have been 

multiplied by 10,000. 

These two SC maps represent the maximum and minimum signal capacities that need to 

be provided by the new radio system. If all radio networks included in this analysis had identical 

coverage areas (same total area, not the identical geography), the maps would be identical 

(except that the ASC map would have values equal 1/K times the corresponding location values 

in the PSC map). The physical significance of the PSC and ASC maps is that the PSC map 

shows the capacity that the new comparable network would need to handle if all possible users 

were concentrated at a single location on the map. The ASC shows the capacity per square mile 

of coverage that the new comparable system would need if all users were spread out as evenly as 

possible over the coverage locations on the map. 

The ASC and PSC maps do not represent realistic estimates. The actual SC values would 

be somewhere between the two. These two types of SC maps suggest the extreme range of 

circumstances that could be supported by the present infrastructure. Even if a comparable 

infrastructure was built to match the PSC maps, there would be no assurances that certain 

circumstances would not overload the system. It would only ensure that the comparable system 

would not have fewer capabilities than the current one. In a wide range of circumstances, a 

properly designed comparable system would be expected to work considerably better than the 

current system. 

A.3 FUNCTION CODE DESCRIPTIONS AND ALGORITHMS 

SC modeling begins by dividing all GMF assignments in the geographical area of 

concern into various classes. The GMF data and agency consultation is necessary to generate a 

“function code” for each assignment. The function code indicates how each assignment is to be 

analyzed by the SCAP. The function code (F, N) has two parameters. “F” denotes the function 

served by that assignment; “N” is an integer that identifies the specific network of which that 

assignment is a constituent part. The actual value of “N” has no significance except to identify 

assignments that are parts of the same network. Each assignment belongs to exactly one 

network; all assignments belonging to the same network will be given the same value of “N.” 

Networks containing only a single assignment do not exercise any network qualities and are 

given a value of N = 0. N = 0 indicates that no other assignment belongs to a given network. 
A-8 

Division of Assignments by Function (F): This variable is associated with the first parameter 

in the function code for each assignment. The function codes for assignments not included in the 

SC analysis are also specified, even though they all produce the same result (no action). This is 

because it is important that it is correctly understood why such assignments were not included, 

and this specification helps to document the understanding of each such assignment. In addition, 

such function codes will be useful in counting some aspects of “before and after” when 

frequencies are compared for particular purposes. The following paragraphs describe the details 

of the function codes and the associated SCAP analysis algorithms. 

Assignments Included in SCAP Analysis:

Base station transmitter F = 3 

Wireless link F = 4 

Simulcast network F = 5 

Trunked network F = 6 

Single-message repeater network F = 7 

Multiple-message repeater network F = 8 

Mobile/mobile user net F = 9 

US/USA/US&P incorporated into net F = 10 

Assignments not Included in SCAP Analysis:

Obsoleted link F = 20. 

Dedicated link F = 21 

Receiver F = 22 

Receive-only station F = 23 

US/ USA/US&P w/o local F = 24 

Low power (10 mW or less) F = 25 

Mobile/portable-only networks F = 26 

The function codes 3 through 10 describe GMF assignments for transmitters that directly 

provide communication services to mobile users, which services could be provided by a single 

shared network. Since these function codes represent assignments that will be included in the 

SCAP analysis, all of these function codes will also require a network number “N.” 

Base Station Transmitter (F=3). This function code is used for an individual base 

station serving a number of mobile users, where it is likely that future service to these users 

could be provided by some type of large shared radio system. Each individual base station 

transmitter can be considered as an independent network and computed separately. All locations 

on the PSC map with predicted coverage will be labeled with a “1,” which shows that one radio 

link is available at that particular location. The ASC map is generated by counting the total 

number of points on the map with coverage, setting K equal to that number of points, and placing 

the value 1/K at all points that get coverage from the base station. N = 0 is the recommended 

network value for a single assignment, indicating that no other transmitters are part of that 

network. 
A-9 

If base station transmitters at multiple sites use the same frequencies, it may be difficult 

to know whether the base station signals can be considered to be independent or not. In general, 

if the base stations have coverage areas that overlap, they cannot be considered independent and 

need to be analyzed as a multi-site network. A user in an overlapping coverage area cannot 

receive multiple independent signals, since the signals are transmitted at the same frequency and 

they will interfere with each other. In the case of multiple same-frequency base stations, the 

function code (F=3) can be used with multiple assignments that all have an identical non-zero 

value for N. If the base station coverage areas do not overlap, this network algorithm will give 

the same results as multiple independent base stations. 

The PSC map for the above network of multiple base stations can be computed by 

finding all locations where a signal can be received from one or more sites and placing a “1” in 

those locations. Locations receiving signals from one base station (non-overlapping coverage 

areas) would obviously get a PSC of “1.” Locations receiving signals from more than one base 

station (overlapping coverage areas) would also get a “1,” because no more than one signal could 

be received without interference (since all signals are at the same frequency). Therefore, the 

PSC maps would have a “1” in each coverage location, no matter whether coverage was from 

one base station site or from many sites. This result is identical to that obtained from multiple 

simulcast sites. This calculation might err on the side of being too optimistic, because many 

locations receiving multiple signals would actually be able to receive no signals; interference 

between the signals would prevent any signal from being received. In addition, some multi-site 

systems may allow only one site to transmit at one time to prevent interference between signals 

radiated from multiple sites. 

The ASC map for a multiple sites network can be calculated in the following manner: 

1. Calculate the ASC maps for all base station sites individually, using the same calculations as 

for a single base station. 

2. Combine the ASC maps for the individual base station sites as follows: 

a. At all locations where there is coverage only on a single ASC map, directly transfer the 

ASC values to the combined network ASC map. 

b. For any locations where there is overlapping coverage, calculate an average ASC value 

from all of the non-zero ASC values at each location. 

The above procedure should be used in any circumstances where multiple base stations 

using the same frequencies might have overlapping coverage. This algorithm will give the same 

ASC map results for multiple non-overlapping base stations sites as when the sites are analyzed 

individually and their individual SC maps are added together. This same algorithm will be used 

to analyze multiple site repeater systems using the same frequencies. 
A-10 

Fixed Wireless Link (F=4). This assignment is used for certain types of fixed radio 

systems (i.e., stationary base station and mobile/fixed auxiliary sites), whose services could be 

provided by some type of large shared radio system. In general, a more complex model would 

need to be used if the auxiliary sites communicate directly with each other, instead of only 

communicating with the base station. Each individual base station transmitter can be considered 

as an independent network and computed separately. All locations on the PSC map with 

predicted coverage will be labeled with a “1,” which shows that one radio link is available at that 

particular location. The ASC map is generated by counting the total number of points with 

coverage equal to K and placing the value 1/K at all points that get coverage from the base 

station. N = 0 is the recommended network value. 

If this system is not suitable to be incorporated into a larger shared system, it should be 

coded “F = 21.” The difference between placing an assignment into the category of “dedicated 

link” (F = 21) or “wireless link” (F = 4) is whether the link function is able to be efficiently 

provided by the future shared system. For example, a dedicated link might be used to provide a 

narrowband backup voice and data link between two federal communication centers; this link 

could not be practically integrated into a future system. Another link might gather continuous 

status/location data from a fleet of vehicles (all vehicles updated every 30 seconds). While this 

could theoretically be serviced by a future mobile system with digital messaging capabilities, via 

the mobile radios in the vehicles, it would probably not be an efficient way to provide the 

service, and more detailed analysis might eliminate it from being a candidate for inclusion in the 

future network. However, a nominally similar service providing river flood warning data (e.g., 

short data message every 15 minutes) might turn out to better match the digital messaging 

capabilities in the future system; this system could be a candidate for inclusion. Depending on 

the exact function of the link and the features chosen for the future system, a given assignment 

may be placed in either of these categories. 

Simulcast Network (F=5). This function code identifies an assignment used as part of a 

simulcast network, with multiple sites using the same transmit frequencies and receive 

frequencies. A previously unused non-zero value of “N” should be selected and used to label all 

simulcast transmitters belonging to this network and operating on a given frequency. The 

coverage areas from all base station transmitters at a given frequency are calculated, and a total 

coverage area for the entire set of transmitters is calculated. The PSC map is generated by 

putting a “1” at all locations that receive coverage from one or more sites. The ASC map is 

generated by counting the total number of points with coverage equal to K and placing the value 

1/K at all points that get coverage from one or more base stations. Note that coverage at a single 

point from multiple simulcast base stations only results in a PSC value equal to 1 because the 

multiple base stations are all transmitting the same signal. Therefore, only one signal can be 

received, irrespective of how many base stations can deliver that single signal to the user. 

In general, most simulcast networks use multiple frequencies. In this case, all sites 

operating at a specific single frequency should be calculated as a single network, with separate 

networks used for each different frequency. If desired, SC maps can be developed for the total 

simulcast system by combining the PSC maps and ASC maps for each frequency (i.e., 

independently computed networks) belonging to the simulcast system. 
A-11 

Trunked Network (F=6). This function code describes an assignment that is used for a 

trunked network, using only local channels. In the case of trunked networks, all channels at all 

base stations operate independently; this is much different from the earlier simulcast example. 

Therefore, a given trunked base station with ten channels would provide ten possible 

independent signals at each point of coverage. Coverage at a given location from two base 

stations (one with ten channels and one with five channels) would provide the possibility of 

receiving 15 independent signals. 

Trunked networks should be assigned a function code (6, N), where N is the same for all 

assignments (transmitter frequencies) at all base stations in the entire trunked network. The peak 

SC map is constructed by computing a coverage area for each transmitter and placing a “1” at 

each location where coverage is available from that transmitter. The PSC values are additive at a 

given location; coverage at a given location by “M” different transmitters gives a PSC value 

equal to M for that location. The ASC map is computed by calculating a coverage area for each 

transmitter and counting the number of locations where coverage is available equal to K. A 

value of 1/K is placed into the average SC map at each location where coverage from that 

transmitter is available. The ASC values are additive at a given location. Coverage at a given 

location by M different transmitters (T1, T2, ... , TM ) gives an ASC value equal to 1/K1 + 1/K2 + 

... + 1/KM at that location, where the K’s are the coverage areas for the respective transmitters. 

In general, all of the K’s will be equal for transmitters at a given site, but each different site will 

have different coverage areas. 

One pair of frequencies at each site will be used for a control channel, and it would 

therefore not be available to carry traffic. However, some trunking technologies allow the 

control channel to carry traffic. Moreover, trunked radio channels generally carry more traffic 

than non-trunked channels. Therefore, all trunked system channels were counted as traffic 

channels. 

Repeater Network (F=7). This function code is used for a repeater transmitter, or for a 

multi-site repeater network. If the repeater network uses a standard pair of repeater frequencies 

at multiple repeater sites with overlapping coverage areas to extend the geographical coverage of 

a system of repeaters, the analysis of the repeater system may need some additional detailed 

study, because it is not usually immediately evident which combinations of the repeaters could 

be used to support individual messages and which could not. The multi-site analysis presumes 

the most efficient possible repeater configuration; in some cases, the repeater network may only 

allow a single message to be carried throughout the entire system. The difference between these 

cases might also depend on options selected by the user for the specific message. 

Single-Message Repeater Systems (F=7). This function code designates a repeater 

assignment, where the repeater (or repeaters) allows only a single message to be carried on the 

repeater system. Repeater systems are often constructed with multiple repeater sites with 

overlapping coverage areas that all use the same receiver frequency and transmitter frequency. 

This means that a mobile user could simultaneously transmit to multiple repeaters, which would 

each repeat (transmit) the same repeated message at the same frequency. Under such 

circumstances, the multiple repeated messages could be expected to interfere with each other, in 

the same way that interference can be caused if simulcast transmitters are not carefully designed 
A-12 

and adjusted. Designing such repeater systems so that multiple repeaters do not transmit 

simultaneously at the same frequency often prevents this interference. Depending on how this is 

accomplished, a repeater system may (or may not) carry multiple independent messages. F = 7 

includes all single-signal repeater systems. This includes systems that consist of a single 

repeater site. Other included repeater systems use multiple repeater sites that are controlled (e.g., 

with CTCSS codes) so that only a single repeater site re-transmits a message at a given time. 

Zone repeaters use multiple frequencies to transmit a single message from multiple sites that 

provide an extended coverage area; however, all sites transmit the same message content. 

PSC maps for a single-message repeater system are computed by placing a “1” at each 

location where there is coverage from one or more repeater transmitters. ASC maps are 

computed by counting the total number of locations with coverage from one or more sites equal 

to K and placing the value 1/K at each location with coverage. Note that these calculations are 

identical to simulcast systems. 

Multiple-Message Repeater Systems (F=8). This function code designates a multi-site 

repeater system that allows multiple independent signals to be repeated. Although some repeater 

systems are designed so that only a single message can be repeated at a given time, other types of 

repeater systems can handle multiple simultaneous messages. For example, consider a multi-site 

repeater system covering a large geographical area. When mobile User A is using a specific site 

to relay a message, an adjacent site (with approximately the same coverage area) cannot 

simultaneously be accessed by mobile user B, since A and B would be simultaneously using the 

same frequency at the same time in the same geographical area. However, simultaneous use 

would be possible if User A and User B were accessing repeater sites that were sufficiently 

separated from each other so that User A’s signal did not interfere with User B’s signal at the site 

which user A was attempting to access (and vice versa). In this example, mobile users can 

operate independently (using separate messages) in some geographical areas, but not in other 

areas. This is the circumstance that function code (F = 8) is intended to analyze. In addition, 

some repeater systems are designed to allow the user to choose how the repeater system operates 

(e.g., perhaps passing a message down a string of repeaters to headquarters or choosing to repeat 

the signal on the local repeater). Such systems will also be designated with F = 8, although F = 7 

would appear to be correct for part of the time. 

The PSC map is calculated by finding the total coverage area of all base station repeater 

transmitters and placing a “1” at all locations with coverage. 

The ASC map for the multiple sites can be calculated in the following manner: 

1. Calculate the ASC maps for all repeater sites individually, using the same 

calculations as for a single repeater station. 

2. Combine the ASC maps for the individual repeater sites as follows: 

a. At all locations where there is coverage only on a single ASC map, directly transfer 

the ASC values to the combined ASC map. 
A-13 

b. For any location where there is overlapping coverages, calculate an average value 

from all of the non-zero ASCs at each location. 

The above procedure should be used in any circumstances where apparently independent 

repeater sites using the same frequencies might have overlapping coverage areas. If there is no 

overlap, this algorithm will give the same results as calculating the SC maps for independent 

repeaters and combining them. 

Mobile/Portable User Net (F=9). This designation is used with an all-mobile/portable 

user net having no fixed base stations. In general, it may be difficult to determine the coverage 

area of such a system according to a set formula. A location and radius may be indicated on the 

assignment, or other data may become available. However, such a system could obviously be 

served by a shared, trunked network, assuming that the network provided service in the 

applicable system service area. 

US/USA/US&P Assignment (F=10). This designation is used for a US/USA /US&P 

assignment added into the shared network. Since such an assignment has no localized 

geographical location and therefore no SC coverage area, these assignments will need to be 

estimated individually by hand, with some reasonable equivalent coverage included. For this 

reason, this function code was not incorporated into the study. 

The function codes 20-26 represent assignments that have not been included in the SCAP 

analysis. This is because the codes represent assignments whose functions are never included 

(e.g., receivers), or because the function provided by a specific system could apparently not be 

easily incorporated in a shared radio system. In the case of these function codes, it is not 

necessary to include any value for N. 

Obsoleted Assignment (F = 20). This indicates that the assignment would no longer be 

needed if an integrated trunked network were operational. Typical examples may include 

telemetry links used to control or indicate the status of equipment associated with the present 

LMR systems, or links used to transport communications between base station sites (as an 

alternative to a wire line connection). The important distinction is that such a link is not intended 

to directly provide communications to users. This function designation indicates that this 

assignment will not need to be supported in any way in the new system. Note that F = 20 does 

not imply in any way that the assignment is not needed to provide services to current networks, 

but only that its specific function would not be specifically transferred to a comparable network, 

especially when the actual architecture of an alternative comparable future system has not yet 

been defined. 

Non-Incorporated Assignment (F=21). This assignment is used for a dedicated or 

special-purpose function that would not be expected to be incorporated in, or replaced by, the 

future shared trunked radio system. It is assumed that these frequency assignments will continue 

to be needed whether or not a new trunked system is constructed. However, for fixed links that 

intermittently transmit data or status in a geographic area served by the shared system, future 

incorporation into the shared system might be considered on an individual basis at a later time. 
A-14 

Since these links will be unaffected by any conversion to a future shared trunked systems, 

F = 21 will be the initial default setting for all assignments. If F = 21, the SCAP analysis 

program will ignore this assignment. 

Receivers (F=22 or F=23). The first round of SCAP analysis will consider only 

transmitter assignments. It is assumed that many agency transmitter assignments have matching 

receiver information. If the receiver frequency is for a standard base station receiver or mobile 

receivers paired with a transmitter at that same site, let F = 22. This indicates that the specifics 

of the situation are adequately described by the transmitter coverage and no further action is 

necessary on the assignment. In many cases, however, the receiver information may provide 

important non-standard information on the nature of the functions of the associated network. 

Receive-only site information may identify functional requirements to provide in-building 

coverage to handheld transmitters, etc. If the receiver assignment is for a receive-only site or for 

some other specialized receiver site, let F = 23. Initially, only the transmitter information will be 

directly incorporated into the geographical SC maps, but F = 23 will serve as a reminder for 

possible later analysis that there are some special receiver requirements that may need to be 

accounted for in the final design. Note that the practice of providing assignments for receivers is 

optional and varies greatly between agencies. These assignments will be ignored in the SCAP 

analysis. 

US/ USA/ US&P Assignments (F=24). The analysis assumes that any US/ USA/ 

US&P, and similar wide-area assignments having “000000" latitude or longitude values will be 

not be used to support any permanent local radio infrastructure. Although the same frequencies 

identified by these wide-area assignment types are often available for temporary or permanent 

local uses, it is understood that any local permanent uses of these frequencies will be identified 

by separate local assignments with geographical coordinates and specifics. These local 

assignments for any local use should be examined independently and designated with the 

appropriate function codes. However, in this analysis of existing local infrastructure capabilities, 

all US, USA, and US&P assignments that are not specifically associated with a location and 

function will be identified with F=24 and ignored in the SCAP analysis. 

Low Power Assignments (power = 10 mW or less) (F = 25). This includes any low 

power assignments (=<10 mW). An example of this category is about 900 low power 

assignments for tracking wildlife tags used by the Department of Interior and some wireless 

microphones used by multiple agencies. These assignments will be ignored in the SCAP 

analysis. 

Mobile/portable-only Assignments (F = 26). This includes assignments that include no 

specific base stations, but involve only portable or mobile radios talking between each other. 

Typical applications might involve a guard force patrolling a federal building, using handheld 

radios to talk with each other. These were excluded from further analysis, since they are using 

no fixed infrastructure that could be replaced by a shared radio system. At some time in the 

future, it might be useful to migrate such systems to become mobile units on a shared system, but 

such a determination would be uncertain and premature at this time. Therefore, the presumption 

is that such systems would continue to operate in their present mode. 
A-15 

A.4 COMBINING SIGNAL CAPACITY MAPS 

The PSC and ASC maps for each network can be generated by the SCAP, after function 

codes have been assigned to each GMF assignment. The resulting ASC and PSC maps can be 

combined with other ASC and PSC maps to get ASC and PSC maps for any desired combination 

of transmitter networks. The process of combining these SC maps is limited only by the 

assumption that the original network SC maps were calculated in a compatible manner–i.e., the 

same distance scales, the same technical criteria for a definition of “coverage,” etc. As long as 

these criteria are maintained, SC maps could be combined from different frequency bands, from 

different agencies, from various federal, state, and local governments, etc. Attempts to combine 

SC maps from different services might be possible, but one would need to carefully explore 

whether a common meaning of “coverage” could be established for the different services. The 

actual SC maps selected to be combined will be dependent on the selection of combinations of 

agencies whose combined systems one would seek to describe.