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CHAPTER V: CURRENT TECHNOLOGY STATUS, 

KNOWLEDGE GAPS, AND RESEARCH NEEDS 

The literature search for technologies to solve firefighter communications and personnel 

location problems caused by poor RF signal propagation in structures identified several 

promising technologies, including ultra wideband (UWB), mobile area networks 

(MANet), other spread spectrum, and use of frequency bands that couple inductively/ 

parasitically to conductors, power line distribution, among others. This chapter discusses 

each of the promising technology areas identified during the literature search. Included in 

each technology section is a discussion of what the technology is, how it is applicable to 

firefighter communications or location problems, current status relative to firefighter 

communications including research to date, and, if applicable, products that demonstrate 

current or potential usefulness to the firefighter communication problem and knowledge 

gaps. Finally, for each technology, a series of recommendations are included which, if 

implemented, could lead to improved radio communications for firefighters on the 

fireground. 

Many of the areas of promise discussed in this section are state-of-the art and their 

descriptions very technical. While every attempt has been made to describe the 

technologies in a straightforward manner, to fully address the nuances of the concepts 

and to correctly describe the technology, the level of information and detail may exceed 

the interest of the casual reader. 

Ultra Wideband 

Ultra wideband (UWB) is not a truly new technology. Marconi employed the concept 

with his spark gap transmitter over 100 years ago. First fully developed in the 1960s for 

the U.S. military, the bulk of work was in the classified area for about three decades. The 

technology has been in use in radar systems for some time because the wide bandwidth 

results in very accurate timing and allows accurate ranging. [208,286] Recent advances in 

switching technology are driving the cost of UWB implementation lower, and many 

believe UWB is the potential next wave in commercial wireless communications. UWB 

offers the promise of: 

• Precision range/radio location systems 

• Robust communications in severe multipath environments such as buildings 

• Low-power systems with long battery life 

• Promises to provide a means to share spectrum without affecting current radio 

signals due to its very wide band, very low power emissions that appear as noise 

to other non-UWB receivers. [301] 

UWB technology has many applications including communications, precision 

geolocation, and radar. Its recent application to high-rate digital communications, 

particularly for use in urban environments where robust propagation in structures is 

required, is an innovative technique that combines the ability to transmit high-rate digital 

data at low power. Impulse radio is a form of UWB spread spectrum signaling with 
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multipath mitigation properties that make it particularly applicable for application in 

severe multipath environments (such as those found in urban settings and within 

structures). [152,210,282,287,305] UWB, requiring a fading margin of only 1.5 dB9

, has 

demonstrated the ability to transmit within structures where higher power narrow band 

signaling fails. [305] Many researchers and commercial companies have come to the 

conclusion that UWB technology is the most promising solution for communications and 

precision location of firefighters in urban areas and particularly in buildings where 

conventional Global Positioning System (GPS) or almost any communications using a 

sinusoidal-based waveform is subject to the issues of multipath fading. It remains to be 

seen whether UWB will emerge as a supplement or a replacement to cellular radio and 

other more traditional RF technologies. 

TECHNOLOGY DESCRIPTION

UWB is a general term for a class of signals that have much wider bandwidths than those 

found in traditional narrowband or wideband communication systems such as trunked 

radio (narrowband) and recently launched third-generation (3G) cellular (wideband). 

UWB is differentiated from these signal classes in two ways: communications bandwidth 

and the use of a carrier-less RF implementation. For communications bandwidth, the 

FCC is considering two definitions: (1) bandwidth greater than 25 percent of the center 

frequency at the –10-dB points or (2) RF bandwidth greater than 1 GHz. [292] This is in 

contrast to wideband 3G cellular, which occupies less than 4 MHz of spectrum, or 

narrowband trunked radio, which occupies 25 kHz. A UWB transceiver can function in a 

carrier-less fashion because it directly modulates an impulse with extremely sharp rise 

and fall times thereby generating a signal with a bandwidth on the order of several GHz. 

[142] Narrowband and wideband systems use an RF carrier to translate a baseband signal 

to the desired RF operations band. The transceiver is very simple for a UWB system 

because of the low power transmitted and the carrier-less implementation. Typically, the 

system will not need a power amplifier and will consist only of a pulse generator fed 

directly into an antenna. To demodulate the signal, a UWB receiver coherently detects 

the signal using a correlation receiver. No complex analog carrier circuitry is needed; 

hardware costs can be kept low once the UWB-based products become mature and 

produced in quantities. Currently, the prototype-based systems are still relatively larger 

and more expensive as the technology is still new. 

In a UWB system, a transmitter emits sequences of impulses that are detected by a 

corresponding receiver whose front-end amplifiers are synchronized and time-gated to 

the transmitted pulse sequences. Data information to be sent is modulated onto certain 

parameters of the transmitted impulse. Such parameters may include the pulse position, 

amplitude, or orientation. For example, using pulse position modulation, the transmitting 

system may time advance a pulse to indicate ‘1’ and time retard a pulse for a ‘0’. [281] A 

single bit of information is typically spread over many pulses, and the receiver system 

coherently sums up the correct number of pulses to determine the bit value. Depending 

on the system vendor and application, some UWB systems transmit many closely spaced 

 

9

 This fading margin is very low; a typical indoor cellular system is designed with 20 dB of fading margin. 
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short pulses, and others may transmit fewer pulses with larger interpulse spacing and 

some use amplitude modulation. [106] Coherent summing provides integration gain in 

the receiver. To allow a multiple access environment, each user would be assigned a 

unique pseudo noise (PN) code similar to conventional CDMA systems (such as the 

cellular service provided by Sprint or Verizon). This PN code would be used to generate 

a unique sequence of time shifts on a pulse train that allows pulses to be discriminated 

from one user to another. As each transmit-and-receive pair is active only for a very short 

period of time, many transmit-receive pairs, each with its own unique pulse sequences in 

time, can operate within the same area without causing mutual interference. 

One important advantage of spread spectrum communication techniques is the ability to 

mitigate multipath problems. Impulse radio technology has the ability to nearly eliminate 

the adverse effects of multipath fading. Typically, multipath signals result from 

reflections of the original signal. These multipath signals will, in general, travel different 

length paths to the receiver with the result being each will have a different phase. They 

add together and, depending on the phase, can increase or decrease the received signal 

magnitude. In UWB systems with very short pulses, the delayed, reflected pulses could 

be detected and ignored. Studies that tested fading performance in homes and office 

buildings found minimal multipath effects [282,287,293] Other researchers are working 

on a Rake receiver UWB implementation which will allow the combining of various 

multipath signals to improve receiver performance similar to cellular CDMA systems. 

[306] 

UWB also has important advantages in transmitting through building materials and 

structures. Generally, building materials show increasing attenuation of RF signals as 

frequency increases. For penetrating a building with an RF signal, a low frequency is 

generally better than a high frequency. UWB is carrier-less and, therefore, covers the 

spectrum from near dc (0 Hz) to the upper end of the signal bandwidth, which can be a 

few GHz. A UWB system essentially “adapts” to the attenuation characteristics of the 

material it is passing through. For a given bandwidth, the center frequency of the UWB 

signal is low which makes for better propagation through and lower absorption from 

materials. Nevertheless, in spite of these advantages UWB transmissions are still 

inherently RF signals and are fundamentally subject to the same absorption 

characteristics as other sinusoidal-based radio transmissions. In this regard, the center 

frequency and other parameters of a UWB-based system must be carefully selected to 

achieve optimum performance for a given application. 

APPLICATIONS

Communications and Networking 

Several technologies are competing for the high-data-rate, short-range market for which 

UWB is suited. These technologies include wireless LAN (IEEE 802.11a, IEEE 802.11b) 

and Bluetooth (Table 8). Figure 7 shows that none of these competing technologies 

provide nearly as much spatial capacity as UWB. [142] UWB has been demonstrated to 

rates over 100 Mbps with the potential to go to 500 Mbps. [306] 
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TABLE 8: COMPARISON OF UWB TO OTHER WIRELESS SYSTEMS 

Technology Data Rate Range Cost Power Spectrum Comments 

UWB 

50–100 Mbps 

(theoretically up 

to 500 Mbps) 

500 ft Low Low UWB 

Only high-data-rate 

WLAN in 300–500-ft 

range 

802.11 54 Mbps 90–100 ft High High 5.0 GHz Power, cost issues 

HyperLan 25 Mbps 100 ft High High 2.4 GHz 

European standard, 

same as 802.11b 

issues 

802.11b 11 Mbps 250–300 

ft Med Med 2.4 GHz Speed issues 

Home RF 11 Mbps 150 ft Med Med 2.4 GHz Lost Intel support, 

speed issues 

Bluetooth 1Mbps 30 ft Low Low 2.4 GHz Speed issues 

Source: [50] 

FIGURE 7: SPATIAL CAPACITY OF UWB 

0

100

200

300

400

500

600

700

800

900

1000

Spatial Capacity (kbps/m2)

IEEE 802.11b Bluetooth IEEE 802.11a Ultra

wideband

Source [142] 

The short pulses of UWB signaling are less susceptible to multipath fading and better 

able to penetrate building materials than competing technologies. These characteristics 

make UWB applicable to robust in-building communications. [145,284] Low-power 

transmissions will also extend battery life. Radio and radar systems could be developed 

that dynamically trade data rate, range, and power consumption/battery life. UWB is 

inherently secure as its low power, high bandwidth makes is appear to be noise to a noncoherent detection system. This makes it more difficult to intercept. 
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Imaging Systems 

Motion detection and radar are natural applications for this UWB technology. Similar to 

other radar systems, UWB radar measures the roundtrip time and angle of arrival of 

reflected pulses. Because of the multi-GHz bandwidth of the system, the resolution can 

be as accurate as 3 cm. [152] This type of application requires a directional antenna 

system to determine angle of arrival. This requirement is a problem as development of 

directional antennas with this bandwidth is difficult. 

Hand-held imaging devices with the ability to detect, range and sense motion of people or 

objects have been developed and commercially deployed for use by police departments. 

[206] An example of such a handheld radar device is Time Domain’s RadarVisionTM. The 

technology has also been used to develop ground penetrating radar systems for 

applications such as mine detection. 

Indoor Geolocation and Tracking 

Using four reference receivers provides three-dimension location of UWB transmitters to 

centimeter precision because of the short, well-defined timing of the UWB pulses. Short 

pulses allow the direct path pulse to be differentiated from multipath reflections that lag 

in time. The UWB transmitter could be a communications radio providing voice 

communications combined with location or a UWB tag used only for location. 

[152,284,327] Each firefighter equipped with a UWB radio or a tag automatically and 

continuously transmits unique data to a set of antennas located at strategic points around 

the building whose positions are precisely known. In this manner, the precise threedimensional location can be determined. These systems typically use either angle of 

arrival (AOA) or time difference of arrival (TDOA) techniques to determine the location. 

Conversely, the UWB transmissions can be picked up locally within the same room with 

a small antenna array mounted on the firefighter’s helmet. This would allow the 

firefighter to not only determine his approximate location and detect or “see” others with 

radios or tags in a smoke-filled room, but also the identity of the other firefighters in the 

vicinity. Furthermore, using this system, the firefighter may also be able to detect the 

location of other UWB-equipped firefighters in adjacent rooms or floors. Receivers 

outside could detect the location of the firefighters as well. As of September 2003, this 

technology has yet to be demonstrated in practice despite several firms’ work in this area. 

RESEARCH AND PRODUCT STATUS

Research and product development using UWB technology is an area of significant 

activity. Two players in the UWB arena are Time Domain Corporation and Multi 

Spectral Solutions, Inc. (MSSI). Time Domain has focused on large-scale 

commercialization of UWB and has taken an aggressive approach to their intellectual 

property development with a suite of pioneer patents in this area. MSSI has remained 

smaller and more focused on specialized applications for both government and 

commercial users including geolocation. [279,285] In addition, a myriad of smaller 

companies and universities have made advances in both technology and prototype 
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development of UWB-based systems, either independently or by teaming with one of the 

larger players. To date, commercial companies have shipped products using UWB 

technology to “see” through walls for use by police and firefighters as noted above. 

Æther Wire & Location, Inc., has demonstrated prototype devices for precise 3D 

location, and Intel has working prototypes of USB devices operating at 100 Mbps with 

predictions of 500 Mbps soon. These products operate in the unlicensed spectrum at 2.4 

GHz and 5 GHz. Worcester Polytechnic Institute (WPI) is also pursuing a location and 

communications system that uses a UWB technology based on a form of orthogonal 

frequency division multiplexing (OFDM). [188,235,298] The advantage of using OFDM 

is that it is spectrally shaped to reduce interference to other RF communications. WPI 

expects to have a proof-of-concept demonstration running late 2004.10 

Significant resources are being devoted to UWB research at universities, government 

agencies, and commercial companies. The most important research topics are: 

• Developing reliable channel models to predict performance and to allow 

optimized transmitter and receiver design. 

• Ongoing research in receiver design to take advantage of multipath reflections 

similar to the Rake receiver technology found in CDMA cellular systems to 

achieve signal processing gain. 

• Developing highly integrated silicon solutions to drive the cost of UWB systems 

down. Time Domain has a three-chip solution at this time. 

• Determining the effect UWB systems have on other communications systems 

such as cellular and GPS. 

ISSUES

Regulatory 

The FCC and NTIA jointly manage the radio spectrum in the United States. UWB 

devices cannot avoid emitting energy into both government and non-government 

spectrum; thus, FCC must coordinate rules with NTIA. UWB meets FCC Part 15 

constraints on incidental radiation but needs a waiver due to the intentional nature of the 

radiation. [143] Recently the FCC gave UWB companies clearance to market their 

devices commercially, but only in a limited range of frequencies and with limited power. 

[223] The ruling restricted operation of UWB communications systems to low-power 

hand-held devices in the 3.1- to 10.6-GHz frequency band. While this specification could 

provide for some communications applications, the limitations are not practical for 

geolocation or radar. However, this was a step forward for UWB proponents and was 

achieved despite objections from the Pentagon as well as GPS and cellular operators. 

Major regulatory issues remain. Usage and interference characteristics of UWB systems 

have become a heated argument in the telecommunications, broadcast, and navigation 

 

10 From a telephone conversation with Dr. John Orr, September 2, 2003. 
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communities. Numeric limits on UWB emissions and what techniques should be used to 

measure them are still being argued from both sides. 

Although the UWB power levels are essentially white noise for most applications, there 

are still concerns of cumulative interference from widespread use of UWB devices in the 

same spectrum as conventional radio communication devices, including emergency 

services, GPS, and cellular networks. [301] The regulatory agencies are looking 

particularly at bands that are used specifically for fire, police, rescue, and other critical 

services. In February 2002, the “Revision of Part 15 of the Commission’s Rules Regarding 

Ultra-Wideband Transmission Systems (ET Docket 98-153)” was adopted. This 

memorandum mentioned the public safety sector as candidates for some UWB 

applications, but it did not include provisions for the several uses of UWB for fire and 

rescue. Industry proponents objected and provided several petitions for reconsideration, 

one of which was through-wall imaging systems specifically for police, fire, and rescue. 

In February 2003, the FCC published a revision to the 2002 docket. The memorandum 

includes several pages of discussion on the topic of firefighter and police safety. The 

proposed modification to the standards was adopted and somewhat relaxed the 

specifications for these applications. While this specifications relaxation was not a major 

technical concession, the acknowledgement of the importance and the shift in the FCC and 

NTIA to allow exceptions for UWB products for the public safety sector were steps 

forward for the UWB community. An excerpt from the FCC February 2003 memorandum 

opening the specification follows: 

We agree that any technology that increases the survivability of our police, 

emergency rescue personnel and firefighters should be encouraged. As a 

result of the factors discussed in the preceding paragraphs, we are 

amending our rules to permit the operation of a through-wall imaging 

system with a center frequency above 1990 MHz at the Part 15 general 

emission limits. However, we acknowledge the concerns expressed by the 

commenters and believe that some additional operational standards should 

be implemented to ensure that operation of this equipment does not result in 

harmful interference to other radio systems that may also be employed for 

public safety purposes. We do not believe that any of these standards will 

cause operational difficulties. [163] 

The FCC has stated its intention to continue evaluating the potential impact of UWB 

devices on other communications services to see if changes are needed to the UWB 

standards. [259] Traditionally, the FCC, NTIA, and wireless community have allocated a 

specific and separate spectrum for each use to avoid interference. This concept has been 

followed since the inception of wireless communications. As a result, the notion that 

UWB will occupy the same spectrum as many of the critical functions is a change in 

thinking for all parties involved. These issues are being addressed by the FCC, NTIA 

[201], and many commercial UWB proponents, but a significant amount of work and 

testing needs to be performed before UWB becomes mainstream. This process could take 

several years. For systems operating within the current limitations, the power restrictions 

limit either the data rates or the effective range of these devices to a degree that could 

potentially cripple this technology. [13] 
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Other 

UWB antenna development is lagging behind the remaining UWB system developments. 

UWB receivers have not reached the level of development to incorporate techniques such 

as Rake receiver design needed to provide truly robust communications in severe 

multipath environments. [280] 

There are some concerns about UWB’s susceptibility to jamming by narrowband signals 

within the UWB passband. [106] 

RECOMMENDATIONS

The public safety community should develop a position in regards to supporting UWB 

deployment and the minimum requirements needed for each firefighter application. If the 

fire community’s position is to support this technology, then minimum requirements 

should be developed for firefighter applications. An organization, such as PSWAC, 

NFPA, or Project MESA11 should be used to make the community’s position known to the 

spectrum-regulating organizations. 

The public safety community, using an organization such as PSWAC, NFPA, or Project 

MESA, should support antenna research and provide input on firefighter-specific 

antenna requirements. 

The public safety community, using an organization such as PSWAC, NFPA, or Project 

MESA, should support research and design of advanced receiver architectures such as 

the Rake receiver. 

Research into electromagnetic susceptibility and compatibility should be supported 

through organizations such as PSWAC, NFPA, or Project MESA. Ideally, power and 

frequency restrictions will be lessened to make UWB more widely applicable for public 

safety applications. 

Mobile Area Networks 

Advances in mobile ad hoc wireless network (MANet) communications techniques may 

make it possible for users to communicate more reliably than with a conventional radio 

system. Often, a user may be located inside a building where communication is possible 

with other neighboring radios also inside a building, but not with the tower or with radios 

located outside the building or in other areas of the building where the RF attenuation is 

too significant. This connectivity scenario brings rise to a new concept where each peer 

 

11 Project MESA is an international partnership producing globally applicable technical specifications for 

digital mobile broadband technology, aimed initially at the sectors of public safety and disaster response. 
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radio is capable of acting as a relay or router and provides a multiple hop communication 

relay chain. In this case, one user, deep inside a building, may be able to communicate 

with another radio closer to the building perimeter. The perimeter radio then acts as a 

relay between the first user and the tower to provide successful communications. 

Originally developed for military and commercial cellular applications, this concept is 

applicable for firefighters and other first responders. Commercially, this technology has 

been gaining increased popularity for wireless voice and data networks. For example, 

potentially large cost savings could be achieved for cellular operators if they could limit 

the number of base stations a tower would have. The concept has become so significant 

that it has inspired the forming of a new section of the Internet Engineering Task Force 

(IETF) on Mobile Ad hoc Networking. A MANet is useful wherever connectivity is 

temporary and on-demand such as a conference or meeting room, military team, sensor 

telemetry, and disaster or first response teams. 

TECHNOLOGY DESCRIPTION

An ad hoc network is a network that has no fixed infrastructure such as base stations. 

Nodes in the network that are mobile and connected by wireless links are called a mobile 

ad hoc network. [206] They are designed to be quickly and autonomously deployed 

without prior planning or preinstalled infrastructure. Whenever two or more nodes are 

within range of each other, a MANet will spontaneously form providing network 

functionality including voice-over IP, a technique for voice communications over a 

network. These nodes or routers are free to move randomly and organize themselves 

arbitrarily. As a result, the network's topology may change rapidly and unpredictably. 

[132] Multihop communications are used to communicate between nodes in the network. 

Multi-hop means that data from the originating node travels to the “best” nearby node, 

which then passes the data to its best nearby node until this series of hops gets the 

communication to the destination node. Each node acts as a router in cooperation with all 

the other nodes in the network. Because this networking approach is designed to form 

and maintain a network without user intervention or infrastructure, it would operate just 

like a traditional VHF or UHF radio from a firefighter’s point of view. He will not need 

to know or notice that when he speaks into his radio whether the communication reaches 

its destination via multiple hops or relays. 

The important features of a MANet are [302]: 

• Network topologies are dynamic. These nodes or routers are free to move 

randomly and organize themselves arbitrarily. Nodes can join or leave a network 

at any time. As a result, the network's topology may change rapidly and 

unpredictably. 

• The network must be able to function on battery power. The restriction of 

available battery power means that the network requirements and capabilities 

must be designed with energy consumption in mind. 

• Depending on the location of each node/radio the radio propagation conditions 

may be quite different. Thus the bandwidth of the wireless links is not consistent 

across the network. Links may drop and reconnect due to fading and other typical 

mobile communications effects. 
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• The physical security of ad hoc networks is lower than wired networks because of 

the use of wireless links and lack of infrastructure support. 

These characteristics of MANet are what drive the research and product development 

activities for this technology. Important areas for understanding the potential, issues, and 

risks of MANet are routing, security, quality of service, wireless link technology, and 

standardization efforts. 

The requirements imposed on MANet networks can be daunting as they include complex 

coordination and switching protocols, algorithms requiring high computational 

bandwidth, real-time handoff with other network nodes, sophisticated modulation 

technologies, and relatively high-date-rates (as compared with existing single-channel 

voice radios). Historically, communications architectures have tended toward pushing the 

network intelligence into a central hub. Since there are only a few hubs or one hub per 

system, it was cost-effective to have expensive RF components and computational 

elements. MANet-based systems push the networks “intelligence” into the handset. In 

spite of the added complexity, user demands still require small, durable packaged devices 

with long battery life. This remains a technical challenge. 

Routing technology is perhaps the most significant technical challenge for MANet 

systems. [136,137,156,157,270,272,273,274,275,276,277] Routing software development 

is driven by the constraints of link bandwidth, node power consumption, and the dynamic 

nature of the network topology. The protocols under consideration are able to form and 

maintain the network with minimal communications. This conserves link bandwidth for 

other services (voice over IP, for example) and extends battery life by limiting the time 

the node is transmitting. Because of the dynamic nature of the network, typical Internet 

routing protocols are not applicable. Most of the MANet protocols use distance vector 

algorithms, which only send routing tables to near neighbors rather than to everyone on 

the network, as do Internet routing protocols. 

Security becomes a difficult issue in a system such as this, since the nodes are mobile and 

can be connected dynamically in an arbitrary and random manner. A rogue mobile device 

could to wreak havoc in a network where each peer has autonomous capability and 

control. Eavesdropping is also a concern with wireless links. 

Quality of service in a MANet has more constraints than a wired network. These 

additional considerations are constant topology changes, bandwidth limitations, and 

limited memory and processing capabilities of network nodes tasked with routing 

communications. The limited memory and processing that each node has is a particular 

problem because of the dynamic topology. The routing protocols and tables require nodes 

to carry out complex calculations and store significant amounts of data about the routes 

including bandwidth. [271] 

There are several candidate wireless link technologies under consideration for mobile ad 

hoc LANs. These include IEEE 802.11 Wireless LAN, UWB, and HyperLAN/2. 
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Of these 802.11 is the most widely used and is suitable for relatively short distances. It 

provides up to 54 Mbps (802.11a or 802.11g) transmission rate and operates in the 2.4-

GHz band. This standard was not developed with mobility in mind and has some serious 

drawbacks. Studies have shown that it has poor scalability, as the throughput per node 

drops very quickly as the network grows. [307] It also has problems with handovers if the 

mobility of network nodes is high. These may not be problems for typical firefighter 

deployments with handheld radios. 

UWB is being used in some MANet projects. [283] It offers to provide high-date-rates at 

relatively low cost and link performance that is not adversely affected by multipath 

effects. A MANet using UWB signaling would combine the benefits of both 

technologies. The synergy between the excellent in-building propagation characteristics 

and the increased reliability offered by a peer-to-peer routing technology may offer a 

reliable in-building communications system. 

HyperLAN/2 is a standard developed by ETSI intended for wireless LANs. Its properties 

make it suitable for MANet applications. It provides high-speed data, 54 Mbps, efficient 

handovers for supporting mobility, and power-saving support. It also provides reasonable 

security by including authentication and encryption. It is relatively costly. 

Many of the technologies involved in wireless ad hoc networking are either established 

standards or have been submitted in draft form to standards bodies such as the IETF 

MANet Working Group. IEEE 802.11 and HyperLAN/2 are both established standards 

while most of the routing protocols are in draft status. Some areas are nowhere near 

having standards. Security and quality of service are areas with no near-term standards in 

progress. This lack of standards is an impediment to wide spread use of MANet. 

APPLICATIONS

Communications and Networking 

 This technique provides a wireless network approach analogous to the standard RF bidirectional amplifier approach that normally uses leaky feeder or coax and antennas for 

interior RF distribution. 

Although prototypes and demonstration projects exist using MANet approaches, no 

commercial systems suitable for firefighter use were found. Several commercial products 

exist that partially demonstrate MANet capabilities: 

• Vocera Communicator and Cisco IP Phone: These devices provide voice-over IP. 

Neither of these devices uses an ad hoc approach; instead they are implemented 

with infrastructure mode IEEE 802.11b using fixed wireless access points whose 

location must be determined by using standard RF planning techniques. They do 

demonstrate voice over IP on a wireless network. 

• Nokia RoofTop Wireless Router: This device acts as a wireless LAN access point 

for users within range and forms a fixed ad hoc network with other Nokia 
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RoofTop Wireless Routers to allow the network to function around obstructions 

such as buildings. It operates in the 2.4-GHz unlicensed band with a speed of 1–2 

Mbps. 

• Radiant Networks Meshworks: This product also forms a fixed wireless ad hoc 

network and acts as a wireless access router similar to Nokia’s but with data rates 

up to 25 Mbps duplex. 

• Mesh Networks Mesh-Enabled Architecture (MEA): MEA provides mobile 

Internet and geolocation in an ad hoc network. Mesh Networks uses a proprietary 

QDMA modulation for the 2.4-GHz-band radio link. The network supports 

multihop communications and fixed wireless routers. 

The U.S. Army and Marine Corp have deployed operational MANet systems. [302,309] 

The Army operates a system called Tactical Internet, which is a large MANet consisting 

of several thousand nodes. The nodes consist of man-portable and vehicle-mounted 

devices. The Marines have deployed a smaller MANet called in its Extending the Littoral 

Battlefield program. This network uses airborne relay nodes to which land and sea units 

connect using a Lucent WaveLan card that has been modified for longer range. Neither of 

these networks uses IETF MANet protocols and do not appear to support voice-level 

quality of service. Little detailed information is available on these implementations. 

Indoor Geolocation and Tracking 

One concept proposed to the National Institute of Standards and Technology (NIST) uses 

a MANet combined with the capability of UWB links to provide a fully integrated 

multifunction voice, data, and telematics system. This device would provide multiple 

critical functions including in-building location, local detection of colleagues, and 

multinodal communications. [206] The ultimate use of such a system could provide a 

unified fire safety network. The combination of a personnel location system with a GISbased floorplan of the building and fire-spread modeling software could become an 

essential tool in fire suppression operations. While some of these concepts may appear to 

be far fetched, most of the core technology is available in pieces to make a fire safety 

network a reality. 

Another approach proposed is to use “data bags” for MANet routing stations in addition 

to the carried handsets. These data bags are UWB transceivers that can act as relay points 

for the geolocation. In this architecture, the standard UWB transmitter tags carried by the 

firefighters would transmit at a power level in accordance with the existing FCC 

recommendations. This approach becomes feasible because the data bags act as mini-base 

stations inside the building, as opposed to other approaches that involve the use of 

antenna arrays located at points on the outside perimeter of the building. In this case the 

RF-shielding effect of the building can work to keep the radiation inside the structure and 

not to interfere with other communications and GPS used on the outside. In addition, the 

data bag also be used as a “sensor pack” to perform critical readings of temperature and 
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other data useful in suppressing a fire. This approach has the disadvantage of the data bag 

becoming expendable. 

RESEARCH AND PRODUCT STATUS

Mobile networking is an area of active research and product development by a number of 

organizations. NIST, for example, has three laboratories—Information Technology, 

Building and Fire Research, and Manufacturing Engineering—working together on a first 

responder testbed that uses an IEEE 802.11-based MANet to provide robust 

communications and radio location within an office building. [189] Recently, the testbed 

was used to demonstrate the ability of the MANet to accurately determine the location of 

each of the network communicators as well as voice communications. In September 

2002, Information Systems Laboratory (ISL) received SBIR funding to investigate the 

feasibility of a system called the Wireless Firefighter Lifeline to locate, track, and 

monitor firefighters inside of buildings to within 1 meter. [166] In addition to tracking 

firefighters, the proposed system also provides biometric data such as heartbeat and 

respiration as well as external temperature and air bottle level to the fire commanders. 

ISL will show the feasibility of the concept through a combined modeling and 

measurement program. Several other companies are developing applications that fuse a 

MANet with UWB. Among them are Æther Wire & Location, Inc., which is developing a 

networked location system under contract to DARPA, and WPI, which is developing a 

combined location and communications system. [300] Florian Wireless is investigating 

the data bag concept described above.12

Routing protocols are being intensely researched. [136,137,156,157,270,272,273,274, 

275,276,277] The routing algorithm faces unique challenges in a mobile environment. 

The most challenging aspects are the dynamic network topology, lack of centralization, 

potentially large networks both in numbers of radios and in area covered, the wireless 

links, and security considerations. Numerous algorithms have been proposed for 

application in ad hoc networks, each having a unique set of advantages and 

disadvantages. Requirements such as self-starting/self-organizing, scalability to large 

networks, computational complexity, routing reliability, link establishment, switchover 

time, blocking constraints, and queuing constraints are being assessed. Some top 

candidates are: [136,137,156,157] 

• Ad Hoc On-demand Distance Vector 

• Landmark Routing 

• Temporally Ordered Routing Algorithm 

• Dynamic Source Routing 

• Fisheye State Routing Protocol 

• Zone Routing Protocol 

• Optimized Link State Routing 

 

12 This information is based on verbal and email correspondence between Rich Meyers of System Planning 

Corporation and Florian Wireless personnel. 
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Architectural approaches being investigated include full autonomous peer-level routing, 

hybrid configurations using a combination of conventional point-to-point radio and ad 

hoc networking when required, and dynamic master–slave topologies. 

ISSUES

Mobile ad-hoc network routing protocols are designed to run on non-engineered, 

dynamic wireless networks. As a result, there are a number of issues in how to provide 

security and guarantee performance within the bandwidth, battery, processing, and 

memory constraints of mobile nodes communicating over radio links. These have to be 

addressed if MANets are to become commonplace. 

Performance 

Wireless Links: Relatively speaking, wireless links perform poorly compared to their 

wired counterparts. Their limited bandwidth and propagation problems, such as multipath 

fading, have a direct impact on routing and quality of service aspects, specifically 

latency, which is critical for applications such as voice. These links must function within 

the power constraints of the mobile nodes. Robust, low-power wireless links are 

essential. [302,307] 

Routing and Scalability: A routing protocol must maintain security and quality of service 

in a dynamic environment but function within the limits of the link bandwidth (constantly 

changing) and node battery life, processing ability, and memory capacity. As ad hoc 

networks grow beyond a few nodes, this becomes increasing difficult. Current routing 

protocols provide only a fair ability to add nodes (scalability). Networks with poor 

scalability may lose the ability to provide the data bandwidths required for voice, have 

increased latency (delay) affecting the ability to talk over a link, or suffer reduced battery 

life. [135,136] Experimental results show that the throughput per node drops by a factor 

of 10 if the network grows from 2 to 8 nodes. [307] As more nodes join the network, the 

total data bandwidth of the system increases until the maximum that can be supported is 

reached. This increase is because nodes must transmit their own user’s voice and data, 

but also be able to relay signals from other users. Once the maximum is reached the total 

rate remains fairly constant as more nodes join. Because the total data transfer cannot 

exceed the maximum, the data rate per node must drop as more nodes are added. Poor 

scalability can also lead to reduced battery life as complex routing algorithms require 

more complex, high-power consumption processors, Wireless links operating at full rate 

also require more power. Finally, if the routing algorithms are not optimized for voice 

properly, they may cause such delays (latency) that it is difficult to talk. 

Dynamic Location Modeling: In a large building fire, it is likely that one or more nodes 

or group of nodes will be unable to communicate with any other node or group of nodes 

because the node (the firefighter and his radio) are out of range, thereby losing 

communications with radios on the outside of the building. For this reason, it is important 

to understand the dynamics of where these nodes would be located during a fire. In 

addition, this requirement will be key in determining a methodology for the use of fixed 
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routing devices that would be strategically placed by the firefighter. The location 

distribution should be analyzed for several major building types, and this overlaid on a 

propagation model to determine the system-level constraints. [247] 

Security 

The two key security considerations for mobile ad hoc networks are (1) tampering or 

utilization of techniques to intentionally render the system inoperable, and (2) 

eavesdropping and surveillance. Security becomes a difficult issue in a system such as 

this, since the nodes are mobile and can be connected dynamically in an arbitrary and 

random manner. It is possible that an outside mobile device could be able to disrupt a 

network where each member has autonomous capability and control. There are also 

physical security risks compared to static operation networks because portable devices 

may be stolen. 

RECOMMENDATIONS

Research should be undertaken to determine the requirements and deployment guidelines 

for fixed MANet node deployment. 

Firefighter requirements for routing, scalability, and security should be established and 

coordinated through organizations such as PSWAC or Project MESA. 

Channel Coding, Interleaving, and Encryption 

An important aspect of radio communications under impaired conditions is known as 

Forward error correction (FEC) or channel coding. Channel coding uses mathematical 

techniques of digital signal processing to enhance data reliability by applying redundancy 

in a known structure to a sequence of data before its transmission. While FEC is nearly 

always used in conjunction with various complementary modulations schemes (e.g. 

TDMA, CDMA, UWB), it is an independent element in the communication chain. The 

structure used by the FEC allows a receiver to detect (and an increased chance to correct) 

errors. The decoder corrects errors without requesting retransmission of the original 

information as is done in many acknowledgements-based protocols; hence the word 

forward. However, FEC comes at a price. The additional structure or redundancy in the 

data stream results in an increase in the required transmission rate. 

TECHNOLOGY DESCRIPTION

Early advances in channel coding date back to Shannon in 1948 when he first published 

his concept of block coding or algebraic coding. Block coding is one of the simplest 

forms of FEC, where the coder inserts redundant bits in accordance with a specific 

algebraic algorithm. Several years later, convolutional coding was introduced which used 

a similar technique to block coding, but instead operated on the data in a continuous 

fashion instead of discrete blocks. In the late 1960s, Andrew Viterbi developed a coding 
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scheme that bears his name and is now the most prevalent technique in use today. Viterbi 

FEC uses a probabilistic technique of considering memory and determining the most 

likely sequence of bits. Other techniques combine a variety of coding techniques to 

achieve improved performance. For example, while convolutional or Viterbi performs 

well with random errors, other techniques may handle burst errors that are typical in radio 

communication channels. This technique is termed concatenated coding. Another 

technique called Reed-Solomon coding is commonly used behind a Viterbi FEC to form 

a concatenated codec. [333] 

Another technique that is frequently used in conjunction with FEC is interleaving. 

Interleaving is particularly effective in communication channels with burst errors. In 

virtually all digital communication channels, data are transmitted in a formatted frame or 

packet. These frames contain various fields such as an address or header, control words, 

and the actual traffic or payload data. In order for these frames to be properly detected, a 

synchronization method usually uses some predetermined sequence often referred to as a 

unique word. If this sequence is not properly detected, then the entire frame or burst of 

data could be lost. Also, certain protocols are more vulnerable to corruption of the control 

data and other critical fields that may occur when a burst error is encountered. Often a 

burst error in the wrong location of a frame will result in synchronization loss, and the 

receiver may require some time to regain synchronization, in which case a significant 

data loss may occur. [333] 

In addition to the inherent synchronization associated with standard digital data 

transmission, the encryption required for secure communication also poses a challenging 

problem. In many modern encryptions, a “crypto sync” is maintained in the decoders. If 

this crypto sync is lost, it may be seconds before the secure channel is reestablished. 

Interleaver technology mitigates this problem by effectively spreading the data over a 

larger period of time. This has the effect of being able to deal with the correction of 

Gaussian-like errors as opposed to the total data loss associated with burst errors. With 

this technique, a burst error on the radio channel may appear as random errors to the FEC 

algorithm. [333] 

In the early 1990s, a new coding scheme called turbo coding was developed in Europe. 

[334] Turbo coding is the most advanced channel-coding scheme developed, and its 

performance approaches the theoretical limit suggested by Shannon. It is a technique that 

uses a combination of other techniques, with multiple encoders and an internal interleaver 

as an integral part of the coding scheme. The major drawback of turbo coding is that is it 

computationally expensive. As a result, custom hardware was required to use this 

technology in systems, as opposed to Viterbi and other techniques that were readily 

capable of being implemented on the same DSP as the modem functions. This factor 

combined with the establishment of a standard for turbo coding and complex intellectual 

property and licensing issues have slowed the widespread use of turbo coding. However, 

an ever-increasing number of systems are being implemented with turbo coding. [323] 

FEC techniques are critical to improving radio communications. This technology is 

particularly important for radio communications inside buildings as it will allow more 
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reliable links in these structures. In addition, as spectrum utilization becomes more of an 

issue, more advanced coding schemes can maintain channel efficiency. 

APPLICATIONS

These techniques are commonly used in virtually all digital wireless communications. 

These include satellite, microwave, and radio communications. These are also used in 

many data storage systems, and even music CDs, to improve reliability of the storage 

mediums should the data become corrupted. 

RESEARCH

Continuous work is being done in this area to improve turbo coding and other 

interleaving technology. Much effort has been spent on computation reduction and 

practical implementation techniques. New interleaving technology is also being 

developed to work better with higher level protocols, such as IP and ATM. 

ISSUES

The major issue is assurance that the appropriate channel coding is used in the selected 

systems. 

RECOMMENDATIONS

Further understand the operation of various FEC and interleaving schemes as they relate 

to the channel error characterization of transmissions inside buildings. 

Investigate the implication of various coding schemes with other suggested areas such as 

MANets and UWB. 

Power Line Communications 

Power line communications (PLC), also referred to as broadband power line (BPL) uses 

existing power transmission networks to deliver communication services to any device 

plugged into an ac outlet and equipped with a PLC LAN interface. Using the power lines 

for communications is not a new concept. In the 1920s, AT&T was awarded PLC patents. 

In the 1950s, power utilities were using low frequencies (sub 1 kHz) to send control 

messages to equipment on the power grid. By the 1980s, bi-directional communications 

in the 5-to-500-kHz band were being used. Following these narrowband, low-data-rate 

PLC applications, broadband PLC started to develop and today commercialized products 

for LAN applications and Internet access are becoming more widely deployed. [265] 

Firefighter use of PLC has several attractive benefits. It promises to be low cost because 

it uses existing infrastructure that is available in every building. Commercial 

developments in this technology area appear to be growing, and firefighters should derive 

cost benefits from this as well. But perhaps the biggest attraction to this type of 
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communication is the ubiquity of power outlets. Not only are they found in every large 

structure, ac outlets are found in essentially every room, parking garage, and hallway. 

PLC data rates are sufficient for high-speed LAN applications including voice over IP 

and can be interfaced to the Internet. 

TECHNOLOGY DESCRIPTION

Power line communications can be divided into two independent systems, in-house PLC 

and Access PLC. In-house PLC conforms to the HomePlug 1.0 standard for LANs and 

operates on the low-voltage (LV) power lines in buildings. Access PLC, where available, 

can be used instead of DSL or cable for backhaul of HomePlug traffic over the medium 

voltage (MV) transmission lines to the Internet. HomePlug is the only power line 

protocol in use for broadband LANs in homes and offices. On the MV transmission grid, 

however, many different protocols are in use for Access PLC with little effort being 

expended to develop a single standard. 

Access PLC, currently in field trials with several power utilities, provides 45-Mbps rates 

over the MV power grid plus the low-voltage lines between the transformer and the 

electric meters of the premises connected to the transformer. The MV distribution 

network extends from the power distribution substation to the stepdown transformer. 

Some Access PLC systems have signaling that can pass through the transformer while 

others use a bypass technique. Typically, the bypass is accomplished by wireless or fiber 

optic connection as the utilities will not allow the LV lines any potential electrical 

connection to the MV grid for safety reasons. An Access PLC base unit is used to 

connect the Internet to the medium voltage line using inductive coupling rather than a 

direct connection. [248] 

The LV power lines extend from the stepdown transformer into the home or office. 

Several protocols are used for low-voltage PLC. Most of the protocols such as X–10, 

CEBus, and LonWorks are meant for home and office automation and security 

applications and are not sufficient for high-data-rate applications. HomePlug technology 

is meant for high-speed LAN applications with current technology built to the HomePlug 

1.0 standard [294] supporting data rates up to 14 Mbps, which is more than adequate for 

voice. HomePlug 1.0 data rates are compared with other broadband LAN types in Table 

9. HomePlug is able to coexist on the same power lines with the other standards because 

it uses a different frequency band. 

TABLE 9: NETWORK DATA RATE COMPARISON

Network Type Data Rate (Mbps) 

Ethernet/IEEE 802.3 10/100 

IEEE 802.11a 55 

HomePlug 1.0 14 

IEEE 802.11b 11 

HomePNA 2.0 10 

Source: [294] 
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HomePlug LAN Internet access is accomplished by having a gateway via cable, DSL, 

wireless, or router. An alternative is to use a PLC modem to couple the HomePlug LAN 

to the Access PLC backhaul network. The modem is connected to the HomePlug LAN 

inside of the meter, and is connected to the electric line outside of the meter. By emerging 

standards, there is a frequency separation between Access and in-house: Access is to use 

the RF frequency space below about 10 MHz, while HomePlug should use the RF 

frequency space from 10 to 20 MHz. 

Within a given HomePlug LAN, the network is self-configuring. The protocol supports 

devices joining or leaving the network at any time. If you plug in another module 

(ordinary node or gateway), then the network need only know how to address the node 

within the address space of the HomePlug LAN. A unique address must be set using a 

computer on the LAN or manually prior to inserting the device into an ac outlet. The 

addresses available on the network need to be known so as not use an address already in 

existence. If the address is not set manually, but by means of a computer, then the 

computer would need the information of the address space in the HomePlug LAN. The 

protocol included priority access with the intention of supporting high-date-rate and lowlatency applications such as voice and video. The standard calls for the range to be up to 

1,000 feet with throughputs as high as 14 Mbps. Real-world throughput is slower as 

shown in Table 10. 

TABLE 10: EXAMPLE REAL-WORLD POWERLINE DATA THROUGHPUT

Powerline 

Transmitter Receiver 

Distance 

Between 

Transmitter and 

Receiver (ft) 

WSFTP 

Throughput 

(Mbps) 

TTCP 

Throughput 

(Mbps) 

Laptop 

(Dining Room) 

Laptop 2 

(Dining Room) ~2 4.2 5.2 

Laptop 1 

(Den) 

Laptop 2 

(Dining Room) ~23 4.5 5.3 

Laptop 2 

(Office) 

Laptop 1 

(Kitchen) ~35 4.0 4.5 

Laptop 1 

(Kitchen) 

Laptop 2 

(Office) ~35 3.1 3.1 

Laptop 1 

(Children’s 

Room) 

Laptop 2 

(Office) ~70 1.9 1.8 

Laptop 2 

(Office) 

Laptop 1 

(Children’s 

Room) 

~70 4.1 3.9 

Laptop 1 

(Swimming Pool) 

Laptop 2 

(Office) ~60 2.0 1.6 

Laptop 2 

(Office) 

Laptop 1 

(Swimming 

Pool) 

~60 2.4 2.8 

Source: [294]
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APPLICATIONS

This technique could be used analogously to the standard RF bi-directional amplifier 

approach that normally uses leaky feeder or coax and antennas for interior RF 

distribution. 

Communications and Networking 

A variety of HomePlug devices are widely available in retail stores for setting up LANs 

in homes and offices. Siemens, for example, sells devices that provide interfaces to the 

power line including: 

• Wireless access point (IEEE802.11b) interface to HomePlug. Siemens sells this 

device to extend the range of a wireless network — an application very similar to 

what firefighters would like to do, extend the range of their hand-held radios. 

• Wireless router to HomePlug. 

• Wired router to HomePlug. 

These devices and the HomePlug standard are designed to make setup easy for the 

average consumer. According to product literature, it is possible to merely connect the 

devices to an ac outlet and have a working network; Siemens ships all its HomePlug 

products with the same default key for its built-in 56-bit DES encryption. These units are 

inexpensive with prices for devices in the $100 range. Access PLC is still in the field trial 

stage, and prospects for commercial success of this technology remain uncertain. 

The use of HomePlug LANs alone or in conjunction with Access PLC in homes and 

offices offers some possible applications for firefighters, including “intelligent buildings” 

and voice and video applications. A HomePlug LAN-equipped intelligent building has 

the potential to connect every electrical device to the LAN and in conjunction with 

Access PLC or alternatives in the same manner as DSL or cable modems connect to the 

Internet. This would allow firefighters to monitor HomePlug sensors (fire, smoke, and 

seismic could be developed) in buildings for fire location and progress and building 

stability before and after entering a burning structure. This ability could aid in developing 

firefighting plans and enhancing the safety of firefighters. It would even be possible to 

integrate this sensor data with fire prediction tools such as the Fire Dynamics Simulator 

and Smokeview visual tool under development by NIST. Even if firefighters did not have 

access to the intelligent building HomePlug LAN over the internet it may be possible to 

develop a first responder interface to a building’s HomePlug LAN (or LANs) that 

firefighters could connect to when arriving at the fire scene. 

A HomePlug LAN can also carry voice communications using voice over IP. In this 

application, the power lines could serve as range extenders for a new generation of radios 

such as the IEEE 802.11 mobile ad hoc network radios being demonstrated by NIST on 

its first responder test bed [189]. As firefighters enter a building, they would plug 

HomePlug to radio interface devices such as Siemens WAP/HomePlug into ac outlets as 

required to give radio coverage local to the HomePlug device. The HomePlug devices 
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autonomously establish a network as long as they have been preset to use the same DES 

encryption key. When a firefighter communicates, his voice would be carried in multiple 

hops either directly to the outside of the structure or if necessary to the WAP/HomePlug 

interface then over the ac power lines to other WAP/HomePlug devices in range of the 

fire personnel outside of the building. [217,250] Firefighters would also need a radio 

device to enable firefighters using 802.11 radios to communicate with personnel using 

the traditional UHF and VHF radios outside the building. Motorola’s ACU–1000 is a 

product that provides a similar type of interoperability for currently deployed radio 

systems that cannot interface directly. [2] 

Another less likely option would be to inductively couple an Access PLC network base 

unit on the stepdown transformer side of the building’s electrical meters. This approach 

has drawbacks. No devices such as those available for HomePlug are being developed, as 

this standard is intended as Internet backhaul rather than LAN applications. There are no 

standards for Access PLC, and two Access PLC networks cannot coexist, so firefighters 

could not set up their own network if one already existed. [248] Access PLC can coexist 

with HomePlug as each resides in a different frequency band. If Access PLC is used for 

Internet access, a conditioning unit will be installed in front of the electric meter. This 

unit has two outputs. The first output is the electrical line for the building, which passes 

through a low-pass filter to filter the Access PLC signal from the electrical lines entering 

the house. The second is the output for the PCL modem, which passes through a highpass filter to allow only the high-frequency PLC signaling to the PLC modem. 

RESEARCH AND PRODUCT STATUS

The HomePlug 1.0 standard is fully developed and devices built to this standard are 

widely available in retail stores. These products provide every conceivable type of 

network functionality likely to be needed in a LAN. 

The next-generation standard (HomePlug AV) will produce data rates above 100 Mbps to 

support high-definition television (HDTV) and standard-definition television (SDTV). 

The HomePlug AV standard release is expected in late 2004 or early 2005. 

Access PLC has reached the field trial stage. [248] Some of the companies involved in 

field trials of proprietary protocols are Ambient, Amperion, Current Technologies, and 

Main.net. A typical example of the many trials is one testing Ambient Corporation’s PLC 

solution operating in Santiago since March 2002. This trial, in which a group of 

volunteers has broadband Internet access and voice over IP service, is in a high-standard 

commercial neighborhood in Santiago. This trial uses the power distribution grid 

operated by Chilectra, an electric utility for broadband Internet access. Internet access 

data transmission rates reach up to symmetric up/down 10 Mbps to the customer premise. 

ISSUES

PLC has both technical and regulatory issues both for commercial applications and for 

firefighter applications. 
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Technical 

Using an Access PLC Network: Only one Access PLC network can exist on a power line 

at a time, but several Access PLC protocols are being tested with no sign of a movement 

to standardize. Firefighters will not know which, if any, Access PLC standard is in use or 

which buildings or parts of dwellings have PLC modems installed. Further, no devices 

are developing applications such as interfacing wireless to power line. 

Coexisting With or Joining a HomePlug: It needs to be confirmed that firefighterinstalled HomePlug devices will operate as needed. 

Setup and Use of a Firefighter PLC Network: It is not clear that the setup and operation 

of a PLC or PLC and wireless hybrid network, HomePlug or Access, can be made fast 

and straightforward enough for firefighters to accomplish in the limited time available to 

them on scene. A procedure would need to be established so firefighters know where to 

install HomePlug devices to relay voice over the power lines. An interface from the 

IEEE802.11 network to the firefighter’s UHF and VHF radios would need to be 

developed to allow the new radios to communicate with the older systems in use. 

Reliability: A test in 500 homes showed that 80 percent of outlet pairs supported more 

than 5 Mbps, and 98 percent were able to support more than 1 Mbps. [294] No testing 

was found in the literature search for real-world performance in structures other than 

homes. Two issues arise here: whether these results meet firefighter requirements and if 

these results hold true in wider testing, including office buildings and multidwelling 

units. 

Security: At least in concept, a technique could be developed to let firefighters access a 

building’s PLC network, but this could create security issues for the everyday users of 

these networks. 

Range: It is unclear whether the real-world range and data bandwidth are sufficient for 

application to structures other than homes. A related concern is the range between 

devices installed on separate low-voltage ac lines connected to separate electrical meters. 

The meters may provide some low-pass filtering and attenuate the signaling. 

Regulatory 

Although the FCC is strongly supporting finding competing technologies (facilities-based 

competition) that provide communications services to homes and offices via a “third 

wire,” opposition exists to Access PLC implementation. Access PLC uses the HF 

spectrum and has the potential to interfere with amateur radio, AM radio, military 

communications, radio astronomy, and distress frequencies. [265] The American 

Amateur Radio League is fighting Access PLC because of their concern that widespread 

implementation of Access PLC will interfere with the HF band and prevent reliable HF 

communications. [257] There is also some concern about interfering with differential 

GPS networks. [261] 
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RECOMMENDATIONS

A detailed study should be undertaken to determine the feasibility of using the HomePlug 

standard as an in-building repeater approach in large structures including those with 

electrical service via multiple electrical meters. Research is needed to determine what 

modifications are necessary to make HomePlug devices suitable for fire service 

communications and to determine if the distribution of ac outlets that work on the 

network is satisfactory. 

Access PLC should be given a very low priority for use in firefighter applications due to 

the numerous uncertainties. 

RF Distribution in Buildings Using Heating and Ventilation Ducts 

Work has been done evaluating the feasibility of a technique for in-building RF 

distribution that uses heating, ventilation, and air conditioner (HVAC) ducts as 

waveguides. [164] 

TECHNOLOGY DESCRIPTION

HVAC ducts in several configurations were used as waveguides for RF distribution. 

Depending on the frequency, good results were obtained with HVAC ducts and showed 

significantly lower losses than both direct propagation and leaky feeder cable techniques. 

Because an existing infrastructure is used, this approach has the potential to be low cost. 

APPLICATIONS

This technique could be used analogously to the standard RF bi-directional amplifier 

approach that normally uses leaky feeder or coax and antennas for interior RF 

distribution. 

One scenario for deploying an HVAC RF distribution system involves coupling RF into 

the ducts at a central point in the duct system. This could be near the central air handler in 

a typical HVAC installation. The coax to waveguide couplers, similar to those now used 

to couple to conventional waveguide, would be inserted into the duct. The RF would 

propagate via the duct, splitting at each branch or tee, which acts as waveguide power 

dividers. If RF obstructions are in the duct, the signal would be coupled around and 

special louvers would be installed in each room to radiate the signal. If the area to be 

covered was shielded from the duct then couplers could be used to feed a passive 

reradiator. Table 11 gives the duct sizes required for various bands. 
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TABLE 11: HVAC DUCT SIZE REQUIREMENTS TO SUPPORT COMMON WIRELESS BANDS

Band 

Lowest 

Frequency 

(MHz) 

Minimum 

Duct Width 

(rectangular) 

(cm) 

Minimum 

Duct Radius 

(circular) 

(cm) 

Cellular 824 18.20 10.70 

ISM 902 16.60 9.75 

PCS 1805 8.10 4.75 

ISM 2400 6.25 3.66 

U-NII 5150 2.91 1.71 

Source: [164] 

RESEARCH

Although providing in-building coverage for RF communications is an area of intense 

study, this technique is not being widely investigated, no buildings have been built or 

retrofitted to use this approach, and no commercial products are available. This is not a 

technique that can be adopted by firefighters prior to commercial companies using it as it 

requires the HVAC system to be specially built. If it were adopted in the future by 

companies providing commercial communications services (cellular, trunking, and PCS) 

it may be advantageous for firefighters to have equipment and the training to enable them 

to communicate via the building’s built-in system. 

ISSUES

Considerable research would be needed to go beyond the current technical feasibility 

study stage. Also, the business case for this type of application has not been put forth 

beyond the researchers feeling that using or reusing parts of existing infrastructures 

(HVAC ducts, etc.) should compare favorably with installation of leaky feeder and other 

current methods on in-building RF distribution. 

Areas for further study include: [164] 

• The waveguide characteristics of most HVAC ducts lead to multimode 

propagation. Added to this will be the effects of reflections from end caps, bends 

and junctions leading to delay spread. Delay spread and coherence bandwidth in 

this environment have not yet been developed. 

• Efficient couplers for getting RF signals into and out of HVAC ducts have not 

been developed. 

• Ducts are not manufactured as precision waveguides. Because of this, mode 

conversion from the dominant duct waveguide mode to orthogonally polarized 

modes is likely to occur at joints and other imperfections leading to signal loss. 

• Viable methods of controlling and determining power splitting at branches and 

tees to allow proper system design do not exist. 

• Current implementations of air dampers and fins in HVAC systems are likely to 

block RF signals propagating in the duct. New methods and materials that will 
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allow RF propagation while performing the necessary air handling have not been 

determined. 

• Many HVAC systems contain RF obstructions such as fans and coils. Methods for 

coupling around these obstructions have not been investigated. 

RECOMMENDATIONS

Further work should be supported to determine if an approach to providing BDA-type 

functionality is feasible. This work should include a study of the distribution of ductwork 

types in structures as well as research that addresses identified issues. Carnegie Mellon 

University has performed some of this research, but this area needs to be more fully 

explored. 

Alternative Frequency Bands 

It may be feasible to take advantage of the propagation characteristics of frequency bands 

outside of the normal VHF and UHF bands used in firefighter communications. The VLF 

and MF bands both provide improved propagation through earth (and by extension, 

building materials). The MF frequencies have been shown to efficiently couple to and 

propagate in mine tunnels over phone lines, ac lines, or even rails used for haulage 

vehicles to provide underground communications over distances of several thousand feet. 

TECHNOLOGY DESCRIPTION

Very Low Frequency Communications 

The VLF band is very narrow, only 27 kHz, and currently allocated for uses such as radio 

navigation. Radio waves in segments of this band can propagate long distances by the 

surface wave phenomenon, and the band is able to penetrate better into the ground than 

higher frequencies. [311] Voice communications in the VLF band would require the use 

of digital compression because of the limited bandwidth. 

Medium Frequency Communications 

The MF band is from 300 kHz to 3 MHz. This band currently includes AM radio (535 to 

1605 kHz or almost half of the band), radio navigation, and various others. Maritime and 

mobile distress, safety, and calling channels for public safety are allocated several 

hundred kHz in this band. MF signals are useful in that they can propagate over fairly 

substantial distances (e.g., two mobile units could easily talk to one another with tens of 

miles of separation). MF signals can propagate through solid material, even several 

hundred meters of rock under the proper conditions, do not attenuate as rapidly as higher 

frequencies when propagating around corners, and can propagate in conductive materials 

in the tunnels such as telephone and power lines. A widely available commercial 

application of MF is RF communications on power lines where it is used for LANs and 
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marketed under the HomePlug name. The HomePlug application was discussed in the 

“Power Line Communications” section. 

The U.S. Bureau of Mines and others [17,18,19,20,21,22,23,24] have studied MF 

propagation in mines in the United States, Canada, Australia, the United Kingdom, New 

Zealand, China, and South Africa. [115] These studies were able to measure and analyze 

the various RF propagation modes found in mines. The studies found that complex 

interactions occurred between MF radio waves and the environment as determined by the 

natural geology (rock composition, water content, etc.) and the man-made features 

(tunnel cross section, presence of conductors such as ac power lines, etc.). Of most 

interest to this report was the finding that when conductors, such as phone or power lines, 

were present propagation in the conductors (two or more conductors are required) 

completely dominates other underground propagation modes. [288] The studies found 

that, in effect, the existing conductors in the facility act as the antenna and transmission 

line for the communications system. 

Mining organizations and related government organizations have also conducted field 

trials of systems using inductive coupling of MF waves into and reradiating from existing 

conductors such as phone lines and ac power lines to provide communications between a 

base unit and mobiles in underground mines over distances exceeding 4,700 meters 

without repeaters. [204] In these installations, it was found that the attenuation rate in the 

conductor was 1 dB/1,000 feet at 100 kHz and 3 dB/1,000 feet at 300 kHz; at 450 MHz, 

the rate was 21 dB/1,000 feet of leaky feeder cable. [115] Others have developed 

propagation models for frequencies from MF to UHF based on extensive measurements 

done in many underground mines. [115,213] These low-loss propagation modes exist in 

circular and rectangular air-filled tunnels with containing conductors (ac power and 

telephone lines and rail tracks). The attenuation is dependent on the distance between the 

conductors and the tunnel rock wall. [211] 

The various MF communication installations used a number of approaches to antenna 

design. The designers had to make the antennas man-portable for the mobile radios. For 

the base station, the antennas could be larger as long as they fit within the tunnel 

dimensions. In either case, the antennas were much smaller than design rules would 

dictate for this frequency. Typically, antennas have dimensions on the order of one-half 

the signal wavelength, which for a 100 KHz signal would be 1500 meters, and obviously 

not practical. The man-portable radio typically used a loop antenna carried over the 

shoulder similar to a bandoleer [116,175] or integrated into a vest. [204] In one case 

[127] the base units used loop antennas that were 6 feet by 24 feet mounted along the 

tunnel wall, and in others used a single-line coupler placed around a bundle of phone 

lines similar to a current probe [204]. The portable antenna and both base station 

configurations performed well. 

APPLICATIONS

Most products and research using VLF and MF frequencies are aimed at underground 

mining operations. 
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Very Low Frequency 

VLF products have been introduced and are used as through-the-earth (TTE) emergency 

evacuation paging systems in place of stench gas [115,179]. Examples are Mine Site 

Technologies’ PED system and MRS’ FlexAlert system. [180] Both systems use large 

loop antennas to transmit to man-portable LF receivers. The man-portable systems 

typically build a VLF receiver and antenna into a miner’s vest. These types of emergency 

paging systems may be of use to firefighters, especially in structures where typical VHF 

or UHF radios provide inadequate coverage. 

Transtek has tested, but not commercially deployed, a VLF TTE communications system 

that allows two-way, real-time, voice communications. No published information is 

available on this system. 

Medium Frequency 

For communication applications, the predominant use of the MF is in underground mines, 

although in the 1970s fire departments in England used large MF loop antennas 

surrounding tall buildings to communicate with firefighters within the building. [115] 

The mine communication applications made use of propagation via the conductor 

transmission lines in tunnels and direct wireless radio-to-radio communications. A typical 

setup had a base station that provided an interface to the telephone system used at the 

mine and an MF loop antenna or line coupler. The telephone system provided 

communications with the outside world while the loop antenna provided communications 

with the underground areas of the mine. The loop antenna was hung on the tunnel wall 

where it parasitically coupled with the conductors (telephone, ac power, rail tracks) 

running through the mine. If the line coupler approach was used, it was clamped around a 

bundle of conductors, frequently telephone lines. Portable transceivers were mounted in 

vehicles or fitted into vests worn by miners. Loop antennas for the portable units were 

worn bandolier fashion. Repeaters were installed in the mine. These units coupled to the 

conductor transmission lines carrying the MF communications signal. If a miner wanted 

to talk to another miner, the communications was direct; communication was wireless to 

the other miner’s radio if he was local. If the other miner was out of direct wireless range, 

the repeater coupled the miner’s transmission onto the conductor and a repeater near the 

other miner retransmitted it. Miners could receive transmission from base unit via the 

conductor without a repeater as long as they were within 2 or 3 miles of the base unit and 

were standing within about 2 meters of the conductors. [211] They could also talk back to 

the base station over the same conditions. 

RESEARCH AND PRODUCT STATUS

There appears to be very little current research or development in the area of MF 

communications. Australia’s Commonwealth Scientific and Industrial Research 

Organisation has some activity in this area but generally it is a mix of public and private 

funding and information dissemination is limited. [17,18,19,21,22] 
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ISSUES

Mine Communications Applicability to Above-Ground Structures 

The research and trials in this area have been done in underground mines where MF 

waves propagate in either of two modes: using conductor pairs in tunnels as transmission 

lines for long distance communications or via direct, wireless radio-to-radio 

communications for shorter range communications. [288] The conductor-pair 

transmission line propagation uses the tunnel as part of the transmission media; this type 

of propagation may not occur in structures. To determine the practicality of direct, totally 

wireless radio-to-radio and power-line-coupled MF to radio, a measurement program 

needs to be designed and implemented that tests performance over a range of structure 

configurations. 

Frequency Allocations 

There are frequencies in the MF band for maritime and mobile distress channels for 

public safety use but not for MF structure communications. Also, there are potential 

interference problems between this and Access PLC or HomePlug networks. 

Commercial Development 

Based on the literature search, it appears little research or product development is 

ongoing in this area even for underground mining. This may make development time and 

cost prohibitive. 

RECOMMENDATIONS

A study should be undertaken to determine the system design and effectiveness of a VLF 

or MF emergency evacuation paging system for firefighter application in structures. 

Mine research used a conductor-in-tunnel waveguide. The applicability of this situation 

to structures should be investigated with empirical measurements in a range of structures 

and variety of conductors (power line, telephone, with and without direct coupling to 

conductors). All types of construction should be investigated, ranging from older 

buildings with predominantly load-bearing masonry walls to modern structures. 

Man-portable and vehicular-mounted antenna development should be supported 

particularly as it addresses firefighting requirements. 

Frequency allocation issues should be studied to determine the likelihood that this type of 

application would be approved. 
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Electronic Status and Firefighter Location 

Firefighter status boards that require firefighters to manually check in and out are in use 

today. These systems, however, are prone to human error and can result in placing a 

firefighter’s safety at risk when not used properly. Recently, systems have been tested 

that automatically track firefighter status to address the difficulties faced by incident 

commanders in tracking personnel on the fireground. 

TECHNOLOGY DESCRIPTION

One system, the Motorola Fireground Accountability System [185], uses the wireless 

signals from each firefighter radio to automatically identify firefighters by sector or 

working assignment. Each radio channel corresponds to an incident command sector, and 

identification information is automatically shown on the incident commander's laptop. 

This reduces the manual approach to status tracking, although the system still has to be 

set up to assign radio channels to sector and enter firefighter identification information. 

Improvements to the system are planned. An evacuation tone triggered by the incident 

commander that wirelessly transmits an evacuation signal to firefighter radios will be 

available. Also, to be added is the capability to poll firefighter radios to identify radios 

that are out of coverage range. The time elapsed since the radio was in coverage will be 

logged. [154] 

ISSUES

Although the system tracks radios to determine if they are out of coverage range and logs 

the elapsed time, it does not tell the incident commander the location of the firefighter. 

RECOMMENDATIONS

Any automated personnel monitoring systems should be integrated with a radio location 

system to provide 3D location of either the firefighter’s radio or an RF tag worn by the 

firefighter. 

Radio location setup and operational requirements should be developed to make the 

location system operable by firefighters. 

Bi-directional Amplifiers 

Bi-directional amplifiers (BDAs) are a technically straightforward technique for 

providing improved coverage in areas that are shadowed from RF communications. 

Unfortunately, there are cost/economic barriers to implementation. 

TECHNOLOGY DESCRIPTION

BDAs are used to boost an exterior signal reradiated in the interior of a structure or tunnel 

and boost the signal from the interior to the exterior. A typical installation uses an 
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exterior antenna called a donor antenna to receive the RF communications signal from 

the exterior source (e.g., a public safety trunking system and transmit signal from the 

interior to the same trunking system). Attached to the donor antenna is a signal boosting 

unit, the BDA. This device uses one frequency band for the talk in channel and a second 

for the talk out channel. Attached to the BDA is a network of cables for distributing the 

signal throughout the structure. The network can be leaky feeder cable that radiates the 

RF signal along its entire length or can be standard coaxial transmission line that has 

antennas and hybrid couplers attached where needed to provide the desired coverage. 

Proper functioning of a BDA system requires a significant amount of RF engineering 

design prior to installation and a significant amount of test and rework time after the 

system is installed. BDAs will not work with simplex radios. 

APPLICATIONS

Many companies provide the components (antennas, cable, etc.) and the engineering 

services needed to install BDA-type systems. 

ISSUES

While technically straightforward to implement, a bi-directional amplifier system is 

expensive to install. It requires the installation of an exterior donor antenna, a bidirectional amplifier unit, and multiple interior antennas and hybrid couplers fed by long 

lengths of coaxial transmission line or, alternatively, the use of leaky feeder cable run 

throughout the building. This is expensive to install in new buildings and even more 

expensive to retrofit to existing buildings. Commercial cellular and trunk radio operators 

see no economic incentive for the installation of such a system except in very limited 

cases where they are guaranteed an income stream for a sufficient time. Systems that 

have been installed are not likely to have been designed with firefighter requirements in 

mind and may not provide the coverage desired or the redundancy needed to provide 

satisfactory operation while sustaining damage during a fire. One answer to this is to 

force installation by building code requirements. This has met with resistance from local 

governments who do not want to put disincentives to businesses into the building code. 

RECOMMENDATIONS

Work with multiple local governments to establish regional adoption of building codes 

requiring installation of BDA systems in new high-rise buildings. The system 

requirements should address fail-safe features necessary to provide reliable 

communications even while sustaining fire damage. 

Investigate alternative implementations of the BDA concept such as power line 

communications, medium frequency coupling to conductors, or use of modified HVAC 

ducts. 
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Smart Antennas 

New-generation smart antennas may provide improved communications if integrated into 

firefighter repeaters, inside or outside a structure. 

Smart antennas have been in limited use for commercial CDMA cellular and other 

wireless applications for several years. These smart antennas are installed at the base 

stations where technical personnel manually program the combining circuitry phase and 

gain adjustments to produce the desired antenna gain, beam-width, and direction to 

reduce interference. In a CDMA network, reducing interference increases capacity. In 

general, the antennas are not automatically adaptable to changes in the RF environment 

or adapted too slowly to react to fast changes. Antenna setup requires an understanding of 

RF propagation, and in-building coverage improvement is not addressed. The antennas 

also are not portable and are expensive. 

TECHNOLOGY DESCRIPTION

A smart antenna consists of a set of antenna elements called an array connected to a 

combining circuit that adapts to the RF environment. The combining circuit adjusts the 

phase and gain of the each elements’ signal and then sums the signals together. This 

signal is fed to the receiver. Recently, product plans have been announced that are 

directed at the wireless LAN market. These developments promise significant benefits for 

wireless LANs: 

• Significant increase in wireless link range 

• Increased network data throughput 

• Reduced power consumption 

• Higher reception reliability 

In contrast to the smart antennas used in cellular base stations, these antennas are small 

and low cost enough to be integrated into home and office wireless access points. They 

have the ability to scan for signals coming from other wireless access points and mobile 

nodes and quickly adapt the smart antenna to point in the direction necessary to optimize 

the wireless link between the smart-antenna-equipped wireless access point and the 

mobile node or other wireless access point. The antenna pattern can be optimized to 

counter the effects of noise, interference, and multipath. [313] These antennas have 

multiple, independent antenna beams so they can produce multiple optimized antenna 

patterns to accommodate multiple wireless links simultaneously. 

Another type of smart antenna is called a MIMO, or multiple input, multiple output, 

system. In a MIMO implementation, both the transmitting and the receiving radio use 

antenna arrays. These systems have demonstrated the potential for very high capacities. If 

the number of antennas is the same at the transmitter and the receiver, the link capacity 

increases linearly with the number of antennas. [340] These types of antennas have been 

tested for hand-held radios as well. [339] In this case, because of the proximity of the 
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antenna array elements, pattern and polarization diversity was used in the MIMO 

processing. 

APPLICATIONS

The inclusion of smart antenna technology in portable repeaters and wireless access 

points could bring important benefits to firefighters. This technology, combined with a 

MANet for firefighters or with conventional UHF or VHF portable radios, would provide 

improved range in or out of buildings. Firefighters could set up a smart-antenna-equipped 

repeater on the building’s exterior and it would cover more of the interior. If the situation 

demanded, they could carry additional repeaters into the building that could communicate 

with the exterior repeater and the firefighter mobiles. One of the functions that could be 

designed into a smart antenna would be the ability to help the firefighter automatically 

locate a site for the repeater. It may be possible to design the smart-antenna-equipped 

repeater to guide firefighters in placing them for the best results. Because the smart 

antenna scans antenna beams to automatically optimize the wireless links to devices 

within its range, a firefighter could carry one into a building and by watching a simple 

display know if the signal strength back to the outside repeater is in the optimum range. 

Also, if firefighters deployed smart wireless access points through a building, they could 

use the same feature to know when they have reached the optimum distance from the last 

repeater. 

Several companies have announced products in development. Lumera Corporation has 

demonstrated an antenna design using a patch array technology to form multibeam 

patterns. The company says the antenna, measuring about 3 inches on a side and 1/4 inch 

height, can support low-power applications such as IEEE 802.11 LANs, as well as 

applications that require up to 10 watts. [321] A second company, Airgo Networks Inc., 

is developing a cost-effective smart antenna based on an OFDM three-antenna, four-chip 

design. Airgo claims it can double the throughput and quadruple the range of 802.11 

wireless LANs. [322] 

RESEARCH AND PRODUCT STATUS

This is an area of active research and product development. Several companies have 

announced products, but these still seem to be some time away from actual product 

deployment. Also, Project MESA has identified smart antennas as an area of interest for 

enhancing public safety communications. 

In general, the performance enhancements offered by the use of smart antennas in 

multihop ad hoc networks can be significant. Issues still remain due to the added 

complexity that smart antennas add to the protocols. [313] 

ISSUES

The effectiveness of smart antennas is closely linked to media access control (MAC) 

protocols. Various MAC protocols have been explored for use with smart antennas. The 

optimum antenna pattern is not obvious due to MAC protocol complexity in conjunction 
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with the functionality of multihop ad hoc networks. Until this is resolved, smart antennas 

may be of limited use. 

RECOMMENDATIONS

Smart antennas improve wireless LAN performance including mitigating multipath and 

should be considered for incorporation into both traditional repeaters and wireless 

access points for a firefighter-deployed MANet. 

Research is needed to develop protocols that optimize smart antenna performance in 

smart antenna applications. The MIMO architecture holds particular promise. 

Training for the use of smart antennas or simplification of the setup procedures should be 

pursued if smart antennas are to be easily used. 

Development of requirements for firefighter applications via an organization like Project 

MESA should be considered. 

Spread Spectrum 

The use of spread spectrum modulation techniques can provide significant multipath 

mitigation and result in improved communications within structures. [218,219] 

TECHNOLOGY DESCRIPTION

The two main types of spread spectrum modulations are frequency hopping and direct 

sequence. A third type is a hybrid of both. 

Direct sequence systems use a high-rate code sequence, along with the information being 

transmitted, to modulate their RF carrier. The high-speed sequence is used directly to 

modulate the carrier, setting the transmitted RF bandwidth. Binary code sequences from 

11 bits to 289–1 bits have been employed, at code rates up to several hundred megabits 

per second. CDMA cellular systems used in the United States are an example of a direct 

sequence spread spectrum system. 

A frequency hopping system covers a wideband frequency spectrum by hopping from 

frequency to frequency over a wide band. The sequence of frequencies occupied is 

determined by a code sequence, and the rate of hopping is a function of the information 

rate. 

Advantages of spread spectrum include: 

• Multipath mitigation 

• Rejection of narrowband interference. 

• Multipath access: number of users can access a common channel for 

communication. 
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• Random access: users can start their transmission at any arbitrary time. 

• Privacy due to unknown pseudo random codes: The applied codes are, in 

principle, unknown to a hostile user. This means that it is difficult to detect and 

monitor the message of another user. 

APPLICATIONS

The literature search found one non-UWB spread spectrum product intended for 

firefighter use, a frequency hopping two-way emergency pager called T PASS 3 

Evacuate. [197] This device is an NFPA compliant two-way PASS device that operates in 

the unlicensed band from 90–928 MHz. It can individually address up to 1,100 

firefighters or can page all at once. It has a companion repeater to provide extended range 

when necessary. In one field trial, two of the repeaters were required to provide coverage 

in a 75-story high rise. The pager is in use in the Las Vegas and Houston fire 

departments. 

ISSUES

Even though spread spectrum signals are immune to most narrow band interfering signals 

they can be interfered with under the right circumstances. When the interferer is strong 

enough to overcome the processing gain from signal spreading, a narrow band 

interference suppression algorithm is needed. An example of this type of interference was 

interference caused by old analog cell phones to newer CDMA cell phone base stations. 

RECOMMENDATIONS

New firefighter communications systems procurements should incorporate multipath 

mitigation as a basic requirement. Use of spread spectrum techniques with the ability to 

withstand narrow band interference is a key component in mitigating multipath. 

Other Technologies 

COMMERCIAL WIRELESS NETWORKS

Use of commercial cellular (800 MHz and 1900 MHz) radios were discussed at the 

preliminary project meeting and rated a low priority for inclusion in this report for the 

following reasons: 

• Propagation in structures similar to or worse than existing firefighter UHF radios. 

• Cellular network availability is not likely in emergencies either due to overuse or 

the system being down because of emergency. 

PROJECT 25 

Project 25, a joint effort of U.S. federal, state, and local government, is the approved 

narrowband interoperability voice and data standard for use in the 700 MHz band for 
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public safety wireless communications. Project 25 radios were discussed at the 

preliminary project meeting and rated a very low priority for inclusion in this report for 

the following reasons: 

• Project 25 standard radios share the same propagation limitations as other UHF 

radios. 

• Project 25 is intended to address other issues such as interoperability and security 

rather than improving in-building communications. 

BLUETOOTH

Bluetooth, a technology that is generally used to wirelessly connect devices, was also 

discussed at the preliminary project meeting and rated a low priority for inclusion in this 

report for the following reasons: 

• Range limited to about 10 m. 

• Data rate approximately 1 Mbps. 

• Intended for short-range use to replace cables. 

The literature search did not find anything to cause the priority of this technology to be 

raised as no applicable research or products were found relevant to this report’s focus on 

firefighter communications in structures. 

General Recommendations 

The following recommendations are given in addition to the detailed recommendations 

by technology area given above. They are generally applicable to the problem of 

firefighter communications in structures. 

The first set of general recommendations address critical deficiencies in the knowledge 

base of the propagation characteristics of radio waves in structures. The literature search 

revealed that while propagation studies have been performed on specific frequencies 

there has been no comprehensive study of propagation characteristics for the full 

frequency range of interest to fire and emergency communications. Nor is there a 

complete understanding of the effects of building materials on these propagation 

characteristics. This latter topic is one that should be ongoing as new materials and 

building techniques, especially those used in high-rise construction, are continually 

evolving. 

RF measurements by NIST [78,79] should be extended to cover from VLF to 10.6 GHz. 

Investigation of frequency dependency of the material dielectric and conductivity 

constants over these frequencies should also be funded. 

An RF propagation survey in structures from VLF to at least 10.6 GHz (upper end of 

band allowed for UWB) should be pursued. 
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The next set of recommendations address deficiencies that affect the determination of 

system specifications for structure communications. For example, 100 percent in-building 

communications coverage is not a realistically achievable goal; 30 percent coverage may 

currently be achieved and is insufficient. These guidelines and requirements need to be 

detailed so that system developers are aware of the acceptable performance parameters. 

Moreover, consideration must be given on how to merge new technology communication 

systems with existing fire department communication systems. 

Requirements should be developed for the minimum level of coverage necessary for inbuilding communications. This is a basic requirement and is independent of the 

communications technology. 

Guidelines for repeater placement for a variety of structures and fire scenarios should be 

developed. 

New technology communications systems should be interoperable, to some degree, with 

legacy systems. 

Current communications technology is a dynamic and evolving field. It is important that 

the technological community and communication system developers understand the 

needs of the fire service. Conversely, it is important the fire services understand the 

possibilities and the limitations of the technologies available. New systems will be more 

complex than the fire service has worked with in the past. Both the fire service and 

manufacturers will need to address the interface between user and developer. 

Establish and fund an organization to facilitate dialog between emergency responders 

and the technical and regulatory groups. 

Public workshops to address firefighter communications issues found in structures should 

be held on a routine basis. 

A newsletter, electronic bulletin board, web page, or other information sharing means 

should be developed specific to firefighter communications issues. 
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Summary of Recommendations 

Table 12 summarizes all of the detailed recommendations noted throughout this chapter. 

The recommendations are grouped by technology area. 

TABLE 12: SUMMARY OF RECOMMENDATIONS

Technology Area Recommendation Page 

The public safety community should develop a position in 

regards to supporting UWB deployment and the minimum 

requirements needed for each firefighter application. If the 

fire community’s position is to support this technology, 

then minimum requirements should be developed for 

firefighter applications. An organization, such as PSWAC, 

NFPA, or Project MESA should be used to make the 

community’s position known to the spectrum-regulating 

organizations. 

50 

The public safety community, using an organization such 

as PSWAC, NFPA, or Project MESA, should support 

antenna research and provide input on firefighter-specific 

antenna requirements. 

50 

The public safety community, using an organization such 

as PSWAC, NFPA, or Project MESA, should support 

research and design of advanced receiver architectures 

such as the Rake receiver. 

50 

Ultra Wideband 

Research into electromagnetic susceptibility and 

compatibility should be supported through organizations 

such as PSWAC, NFPA, or Project MESA. Ideally, power 

and frequency restrictions will be lessened to make UWB 

more widely applicable for public safety applications. 

50 

Research should be undertaken to determine the 

requirements and deployment guidelines for fixed MANet 

node deployment. 

57 

Mobile Area 

Networks Firefighter requirements for routing, scalability, and 

security should be established and coordinated through 

organizations such as PSWAC or Project MESA. 

57 

Further understand the operation of various FEC and 

interleaving schemes as they relate to the channel error 

characterization of transmissions inside buildings. 

Channel Coding, 59 

Interleaving, and 

Encryption Investigate the implication of various coding schemes with 

other suggested areas such as MANets and UWB. 59 

A detailed study should be undertaken to determine the 

feasibility of using the HomePlug standard as an inbuilding repeater approach in large structures including 

those with electrical service via multiple electrical meters. 

Research is needed to determine what modifications are 

necessary to make HomePlug devices suitable for fire 

service communications and to determine if the 

distribution of ac outlets that work on the network is 

satisfactory. 

65 Power Line 

Communications 

Access PLC should be given a very low priority for use in 

firefighter applications due to the numerous uncertainties. 65 
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Technology Area Recommendation Page 

RF Distribution in 

Buildings Using 

Heating and 

Ventilation Ducts 

Further work should be supported to determine if an 

approach to providing BDA-type functionality is feasible. 

This work should include a study of the distribution of 

ductwork types in structures as well as research that 

addresses identified issues. Carnegie Mellon University 

has performed some of this research, but this area needs 

to be more fully explored. 

67 

A study should be undertaken to determine the system 

design and effectiveness of a VLF or MF emergency 

evacuation paging system for firefighter application in 

structures. 

70 

Mine research used a conductor-in-tunnel waveguide. 

The applicability of this situation to structures should be 

investigated with empirical measurements in a range of 

structures and variety of conductors (power line, 

telephone, with and without direct coupling to conductors). 

All types of construction should be investigated, ranging 

from older buildings with predominantly load-bearing 

masonry walls to modern structures. 

70 

Man-portable and vehicular-mounted antenna 

development should be supported particularly as it 

addresses firefighting requirements. 

70 

Alternative 

Frequency Bands 

Frequency allocation issues should be studied to 

determine the likelihood that this type of application would 

be approved. 

70 

Any automated personnel monitoring systems should be 

integrated with a radio location system to provide 3D 

location of either the firefighter’s radio or an RF tag worn 

by the firefighter. 

71 

Electronic Status and 

Firefighter Location Radio location setup and operational requirements should 

be developed to make the location system operable by 

firefighters. 

71 

Work with multiple local governments to establish regional 

adoption of building codes requiring installation of BDA 

systems in new high-rise buildings. The system 

requirements should address fail-safe features necessary 

to provide reliable communications even while sustaining 

fire damage. 

72 

Bi-directional 

Amplifiers 

Investigate alternative implementations of the BDA 

concept such as power line communications, medium 

frequency coupling to conductors, or use of modified 

HVAC ducts. 

72 
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Technology Area Recommendation Page 

Smart antennas improve wireless LAN performance 

including mitigating multipath and should be considered 

for incorporation into both traditional repeaters and 

wireless access points for a firefighter-deployed MANet. 

75 

Research is needed to develop protocols that optimize 

smart antenna performance in smart antenna 

applications. The MIMO architecture holds particular 

promise. 

75 

Training for the use of smart antennas or simplification of 

the setup procedures should be pursued if smart 

antennas are to be easily used. 

75 

Smart Antennas 

Development of requirements for firefighter applications 

via an organization like Project MESA should be 

considered. 

75 

Spread Spectrum 

New firefighter communications systems procurements 

should incorporate multipath mitigation as a basic 

requirement. Use of spread spectrum techniques with the 

ability to withstand narrow band interference is a key 

component in mitigating multipath. 

76 

RF measurements by NIST [78,79] should be extended to 

cover from VLF to 10.6 GHz. Investigation of frequency 

dependency of the material dielectric and conductivity 

constants over these frequencies should also be funded. 

77 

An RF propagation survey in structures from VLF to at 

least 10.6 GHz (upper end of band allowed for UWB) 

should be pursued. 

77 

Requirements should be developed for the minimum level 

of coverage necessary for in-building communications. 

This is a basic requirement and is independent of the 

communications technology. 

78 

Guidelines for repeater placement for a variety of 

structures and fire scenarios should be developed. 78 

New technology communications systems should be 

interoperable, to some degree, with legacy systems. 78 

Establish and fund an organization to facilitate dialog 

between emergency responders and the technical and 

regulatory groups. 

78 

Public workshops to address firefighter communications 

issues found in structures should be held on a routine 

basis. 

78 

General 

Recommendations 

A newsletter, electronic bulletin board, web page, or other 

information sharing means should be developed specific 

to firefighter communications issues. 

78