Report of the

Defense Science Board

Task Force

on

 Wideband Radio Frequency 

Modulation

Dynamic Access to Mobile Information Networks

July 2003

Office of the Under Secretary of Defense

for Acquisition, Technology, and Logistics

Washington, D.C. 20301-3140
This is a product of the Defense Science Board (DSB).

The DSB is a Federal Advisory Committee established to provide

independent advice to the Secretary of Defense. Statements, opinions,

conclusions and recommendations in this report do not necessarily represent the 

official position of the Department of Defense.

This report is unclassified

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TABLE OF CONTENTS

TABLE OF CONTENTS.............................................................................I

EXECUTIVE SUMMARY.........................................................................III

CHAPTER 1. INTRODUCTION.................................................................1

Terms of Reference..............................................................................2

CHAPTER 2. REVIEW OF RF COMMUNICATIONS, CHANNELS,

AND MULTIPLE ACCESS SYSTEMS .........................................................7

CHAPTER 3. SUMMARY OF CURRENT CAPABILITIES

AND ONGOING RESEARCH AND DEVELOPMENT ................................ 21

Government Funded Research ........................................................21

Commercial Research and Development........................................23

CHAPTER 4. TASK FORCE FINDINGS................................................... 37

TOR Item 1: Technical Issues Associated with Wideband

Radio Frequency Modulation ..........................................................37

TOR Item 2: Review the Technical Issues Associated

with Spectrum Management............................................................39

TOR Item 3: Implications of Employing Wideband RF 

Modulation........................................................................................45

TOR Item 4: Network Services.........................................................49

TOR Item 5: Interference ..................................................................52

TOR Item 6: Cost and Technical Risks.............................................54

Summary of Findings .......................................................................59

CHAPTER 5: RECOMMENDATIONS ...................................................... 61

Agile Wideband Communications System Initiative .....................62

RF Communications Systems Research and Development...........62

RF Communications Systems Testbed ............................................65

Identify an Office for Network-Centric Communications 

Architecture.......................................................................................67

Policy..................................................................................................70

CHAPTER 6: CONCLUSIONS ................................................................ 73

REFERENCES ....................................................................................... 75

APPENDIX A. TERMS OF REFERENCE .................................................. 77

APPENDIX B. TASK FORCE MEMBERSHIP............................................ 81

APPENDIX C. LIST OF BRIEFINGS......................................................... 83

APPENDIX D. GLOSSARY .................................................................... 85
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EXECUTIVE SUMMARY 

Radio communications is in worldwide flux. There are pressures from the

commercial sector for additional frequency spectrum to provide new services;

there is significant demand from the Department of Defense (DoD) to increase

communications capacity around the world and in multiple

contexts/environments; and there are multiple proposals for innovative radio

architectures that promise greatly enhanced radio frequency capacity. This report 

discusses these aspects and presents a set of recommendations aimed at moving 

in a comprehensive manner to a coherent communications system for the

Department of Defense.

Wideband radio frequency (RF) technology addressed many of these issues

facing the Department of Defense regarding network-centric warfare. The 

technology offers high capacity communications links necessary to tie

widespread sensors, to officers, and to weapons on target; it offers flexibility to

meet mission goals, whether covert communications or networked task forces; it 

offers the means to interconnect terrestrial, airborne, space, and wired

infrastructure into a comprehensive warfare network; and it offers the means to 

adapt to domestic and international spectrum management policies and

recommendations.

Radio frequency spectrum management involves the interplay of technology, 

the physical world, economics and business, legislation and regulation,

homeland security and national defense, national policy and international

relationships. Recently, a number of themes have converged to cause significant 

reconsideration of how radio frequency spectrum is managed in the United

States and on an international scale around the world. The important technology 

themes are:

• Advances in radio frequency circuits, analog/digital conversion,

digital signal processing, field programmable gate arrays, and

computer aided design tools enable one to build flexible radios with

significant software control and processing.

• End-user interest in mobile access to information resources and

strong interest from the commercial sector to develop and deploy

new services raises the demand for spectrum.
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• Requirements of national defense and homeland security place high

demand on spectrum resources.

• Recognition that spectrum is woefully under-utilized due to dated

regulations and allocation/assignment processes and that treating

spectrum as a scarce resource leads to exorbitant license costs.

• Proposals to dramatically re-architect the modes and mechanisms for 

using radio frequency spectrum for communications of multiple

types promise higher utilization and enhanced services.

The Department of Defense (DoD) demands robust, high capacity, and agile

communications links in an extremely wide range of environments. Meeting

such demands requires addressing technical research and development issues,

integrating multiple systems (e.g. space, airborne, and ground based), and

cooperatively addressing national and international policy and regulation issues.

The task force was asked to investigate six items in its Terms of Reference, 

summarized here:

• Identify technical issues associated with wideband systems and

impact on DoD and other agency systems,

• Monitor interagency review of spectrum management,

• Examine implications of DoD use of wideband on U.S. positions at

WRC,

• Evaluate impact of wideband on future mobile networks and other

users,

• Evaluate flexibility of wideband RF systems to meet present and long 

ranged communications needs, and

• Identify and assess cost and technical risk of extensive employment

of wideband systems.

The task force found there are many promising communications technologies, 

many if not most having been developed with DoD support, to achieve specific

DoD communications needs. Research in wideband RF systems, advanced signal 

processing, and networking is especially active. Wideband RF systems promise

significant capabilities for adapting to a wide variety of problems, including high 

capacity links, robust communications, sharing the frequencies with existing

systems, agility in worldwide operation, and improving spectrum utilization.

However, evaluation of individual technologies many times becomes bogged
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down in arguing specific technical issues within a wide breadth of possibilities.

The task force used two models to understand these technical tradeoffs. The first

model, a RF Resource Space, helped us understand the tradeoffs between

frequency, spatial extent, time, and signal format. The second model, a

generalized communication channel, made explicit options in configuring a radio 

channel, for example, the tradeoff between compressing an information source

and increasing transmission capacity. The task force found missing any

architecture for network-centric systems. The lack of a network-centric 

architecture leads to technical bickering and limited progress towards a 

functional, integrated system. The challenges in formulating a network-centric 

system architecture and implementation roadmap are significant, but necessary 

to incorporate these many communications technologies into a capable networkcentric warfighting system.

Spectrum management continues to be a topic of significant debate within the 

federal government. Following the DSB report on DoD Frequency Spectrum Issues

[DSB2000] and many discussions in the commercial and academic sectors, a

number recent activities are dealing with spectrum management. The FCC’s

Spectrum Policy Task Force was chartered to evaluate changes in the spectrum

policy that will increase the public benefits derived from the use of radio

spectrum. The General Accounting Office (GAO) has issued a number of reports 

within the last year indicating congressional interest. Private and public groups

have open debates on spectrum policy issues. DoD has demonstrated the

importance of spectrum in meeting its mission by reorganizing its offices; 

creating a Office of Deputy Assistant Secretary of Defense for Spectrum, Space,

and C3; and engaging in discussions with industry and preparatory meetings for 

the World Radio Conference. DoD will continue to feel pressure for its spectrum 

resources from domestic and international sources and from the need to meet

future worldwide missions, including homeland defense. Early engagement with 

the various stakeholders and demonstrated capabilities to increase spectrum

utilization would benefit DoD.

Spectrum management, for DoD, continues to be a problem that must be

considered in a worldwide context. First, spectrum management is a sovereign

right of nations and subject to treaty negotiations. Given the multi-faceted nature 

of any specific mission, access to other nations’ radio spectrum resources is as

crucial as access to over-flight permission, port rights, and force basing rights.

Second, commercial interests, domestic, international, and global, will use

various national and international forums to advance their interests. These

forums might be individual sovereign nations, regional consortia, international
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treaties, or standards bodies. An emerging, and effective, way for commercial

entities to influence spectrum issues is through sets of countries that do not have 

the significant spectrum needs of the United States. DoD must recognize these

significant influences on spectrum policy; anticipate future trends in worldwide 

commercial services; fully participate at the earliest time and at the highest levels 

in these multiple international forums – and be fully prepared to rapidly adapt to 

shifts in international spectrum treaties, rules, and regulations.

To achieve the flexibility necessary for DoD to meet its worldwide missions, 

increase capacity, and increase spectrum utilization, radios will have to use the

latest technology, be adaptive, and be automatically coordinated across the

communications network. It will no longer be possible to optimize a radio

communications link for a specific mission. Missions will come and go over time 

and the units involved in a specific mission will be assigned ad hoc. Thus, the

radio communications network will be formed as needed. This implies that all

components of the radios system must be “tunable” and managed by an external 

network manager. The challenge before DoD is the integration of multiple radio 

technologies and the network protocols, routing, and management technologies

and the information dissemination technologies into an adaptive, mission

oriented communications system serving the warfighter. This is a significant

challenge that must be addressed in the near future.

As DoD communications requirements expand, the task force finds the cost of 

our systems can benefit from the advances in the commercial communications

sector. Yet the demands of the DoD can be very specialized (e.g. non-commercial 

radio frequencies and wider operating ranges), resulting in small parts quantities 

and performance requirements beyond those of the commercial sector. In many

cases, this obviates the opportunity to use commercial capabilities and

components. Wherever possible new communications strategies should be

designed such that they can capitalize on the technology investment and

production base of the commercial sector but, where this does not yield results,

investments will be required to minimize risk, reduce cost, and provide the

required capability to meet mission objectives.

In general, the task force finds that the Department of Defense is best served 

by investing in and advocating wideband RF communications systems for future 

communications systems though coordinated research, development, and

procurement; extensive experimentation, integration, test, and evaluation; and 

developing new policies and engaging the commercial sector through various

bodies with solid experience.
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In particular, to move this vision forward within OSD and the military 

departments, the task force recommends that:

1. The Office of Secretary of Defense must initiate a comprehensive

program in agile wideband communications systems.

2. Assistant Secretary of Defense for Network Information and

Integration (ASDNII) and Undersecretary of Defense for Acquisition,

Technology, & Logistics (USDATL) should increase and focus

investment in flexible and adaptive Agile Wideband communications

technologies to achieve necessary mission capabilities in a highly

dynamic RF communications environment.

3. ASDNII must establish an Agile Wideband Communications Systems

Testbed.

4. ASDNII should identify an office for network centric communications 

and develop a roadmap for technology investment, evaluation, and

transition into operational systems. The roadmap should indicate

phase-in and phase-out of technologies and architectures.

5. ASDNII must take the lead in demonstrating stewardship of allocated 

spectrum and the advantages of agile wideband RF communications to 

develop and put forth spectrum policies based on experience.

The proposed wideband based systems are readily reprogrammable in the

field and are inherently agile in space, frequency, time, and coding. The Joint

Tactical Radio System (JTRS) is but a first step towards these agile wideband 

systems. Investment in wideband systems will positively impact necessary high

capacity data links, critical missions, and adaptation to the varied and changing 

spectrum policy and regulation environment on a global scale. 

The wideband communications/network management approach advocated

in this report would be an extension of the widely discussed for Code Division

Multiple Access (CDMA) approach. CDMA appears to offer a single control

mechanism in which one can vary spreading, power, number of users, etc. It can 

be combined with other techniques, for example, data compression, frequency

hopping, and steerable antennas, to achieve additional performance. However,

sole selection of CDMA hinders other possible emerging technologies, such as
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multiple-input/multiple-output (MIMO) or Space-Time Processing (STEP)

advanced signal processing techniques. The approach advocated in this report is 

to consider CDMA an important component of a larger wideband RF approach

that intentionally incorporates and evaluates new technologies on a continuous

basis. Agility in spectrum, space, time, and signal coding ”future-proofs”

military radio investments against the rapid developments in waveform

technology, some of which may render CDMA obsolescent in the desired

deployment lifetime of military radios currently on the drawing boards.

Agility implies control. The investigations of the task force led it to recognize 

the emerging convergence of radio communications systems, networks, and the 

necessary future coordination between the two seemingly different technologies.

Agile radios require new, network based, control mechanisms that must take into 

account spectrum resources, international constraints, physical limitations,

timely mission needs, and rapid adaptation during mission execution.

Technologies to implement the control mechanisms; steerable and compact

antennas; high-efficiency power amplifiers and low-noise receiver; and advanced 

signal processing hardware are a few of the important investments. The 

convergence between radio communications systems and networked systems

must be recognized and pursued through research and experimentation.

Network control and routing protocols must be developed to support future

agile radio infrastructure. Ad hoc network routing protocols must evolve beyond 

current ”fewest hops/lowest cost” objectives to encompass a richer trade-off 

space. The future infrastructure will range from squad size, covert

communications across several kilometers, to fiber-satellite-unmanned aerial

vehicle-ground dissemination of timely information. The procedures of utilizing 

this advanced radio communications infrastructure must be investigateddeveloped-tried-deployed. The task force found little experience with new

modes of dissemination. Innovative information dissemination procedures must 

be coordinated with emerging command doctrine.

Many systems must come together and operate together in challenging and

extremely varied environments. The best assurance that multiple systems will

interoperate is extensive experience. The task force recommends an Agile

Wireless testbed be established within DoD to experiment with new systems,

integrate and test emerging systems, and evaluate the performance and provide 

feedback to researchers and system designers for continuous improvement. The 

number of wideband communications/network managed systems is numerous, 

only experimentation and experience will provide guidance to implement and

deploy the best possible systems.
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Finally, the Department of Defense must recognize the many interests and

forces on spectrum within the United States and around the world. DoD can take 

a leadership role in emerging policies by practicing ”spectrum stewardship” and 

demonstrating, through the testbed, new systems and capabilities. DoD’s 

position is strengthened by developing policy based on solid experience.

The body of this report first introduces the topic and reviews the Terms of

Reference for this investigation. It then presents an introduction to technical

communications for senior executives to the complex tradeoffs addressed. Next, 

it develops the findings in a detailed and systematic manner. Finally, it draws

recommendations and conclusions summarized above. This report argues that

the Department of Defense must embrace a technology development and 

architecture and develop a deployment path that incorporates wideband

technologies and institutes an organization that monitors and guides future RF

communications systems to achieve crucial mission requirements within an

achievable budget.
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CHAPTER 1. INTRODUCTION

The task force was asked to consider the implications of applying wideband

communications technology to future Department of Defense (DoD)

applications. To this end, the task force examined the current state-of-the-art in 

communications technology, reviewed government and industrial research,

considered how the technology might influence future DoD applications, and

what actions the DoD should invoke to take advantage of the available and

future technologies. Wideband radio frequency modulation systems are of great 

interest to the Office of the Assistant Secretary of Defense for Network

Information and Integration (ASDNII) because they offer the military potentially 

greater efficiency in the use of radio frequency spectrum, increased flexibility in

establishing communications networks, and at the same time can offer protection 

against interference as well as low probability of detection.

Communications is key to the vision of network centric warfare. In Joint

Vision 2020 [JCS2000], the Joint Chiefs of Staff put forward a vision of

interconnected sensors, shooters, command, control, and intelligence based on

pervasive communications. This communications-based interconnectivity would 

then provide operational information superiority, more complete battlefield

awareness, and dynamic joint operations. Communications also plays a critical

role in transformational efforts as outlined in the 2001 Quadrennial Defense

Review (QDR) [QDR2001]. The QDR requires “leveraging information 

technology and innovative concepts to develop an interoperable, joint C4ISR

architecture and capability that includes a tailorable joint operational picture.”

However, the task force has concluded that the vision stated by both the

Office of the Secretary of Defense and the Joint Chiefs of Staff will be difficult, if 

not impossible, to achieve given the current approaches and programs within the 

DoD. In particular, current programs continue to be focused on specific projects 

and do not consider wider system implications. While DoD talks about a

“systems of systems,” there is little value placed on putting programs in a larger 

context, on science of this “systems of systems,” and on experiments with large

communications systems. This report recommends directions DoD should take

to bring vision to reality in network-centric warfare.
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TERMS OF REFERENCE

The general direction of this study is summarized in the following statement 

from the Terms of Reference (TOR):

“...review and advise on key aspects of the policy and technology 

issues associated with the military applications of wideband Radio 

Frequency systems.” 

The task force took the following issues under advisement in directing

considerations:

• Identify technical issues associated with wideband systems and 

impact on DoD and other agency systems,

• Monitor interagency review of spectrum management,

• Examine implications of DoD use of wideband on U.S. positions at

WRC,

• Evaluate impact of wideband on future mobile networks and other

users,

• Evaluate flexibility of wideband RF systems to meet present and

long-ranged communications needs, and

• Identify and assess cost and technical risk of extensive employment

of wideband systems.

The draft TOR referred to “Wideband CDMA” systems. The task force asked 

to expand the terms to “Wideband RF Modulation,” to include in the study an

examination of emerging ultra-wideband systems. Ultra-wideband systems are

emerging from the laboratory into products and deployment and claim

significant capabilities related to wideband communications systems. The 

complete Terms of Reference is discussed in Chapter 4 and presented in

Appendix A.

The term ‘wideband RF modulation’ can have several meanings. In this

report, the following were considered:

(1) Use of a wide frequency range, generally contiguous, to achieve

high data transmission capacity (large bits per second capacity).

Sensors and aggregate links (e.g. Tactical Operation Center to
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INTRODUCTION _______________________________________________________________ 3

Tactical Operations Center or theater to CONUS links) are typical

examples.

(2) Use of a wide frequency range, perhaps non-contiguous, to achieve 

covert or anti-jam capabilities.

(3) Use of wide frequency range, perhaps non-contiguous, to achieve

agility and flexibility in spectrum utilization.

Second, the term ‘code division/multiple access’ (CDMA) can have several

meanings. In this report, the task force considered the following:

(1) Spreading a relatively narrow band signal over a wide bandwidth

to achieve robust and perhaps covert communications. Also known 

as “direct sequence spread spectrum (DSSS).”

(2) Using multiple orthogonal codes to allow several users access to

the same frequencies at different times, such as CDMA.

(3) A structure for a cellular radio system as used in some commercial 

cellular services (e.g. IS-95 or W-CDMA standards).

In discussing various systems and options, the task force intends to ensure

the meaning of terminology is clear.

While the TOR focuses on the technical aspects (e.g. sharing, flexibility,

interference, risks) of wideband systems and the spectrum issues, the task force 

carefully considered the fourth item, the use of wideband RF modulation in the 

context of future mobile networks. A communications mechanism, for example

wideband CDMA, or other and is used between traditional radios, networks, and 

services, promises a new synergy with significant capabilities.

The members of the task force were selected for their experience in a wide

range of backgrounds. Members were included with backgrounds in (a)

developing and analyzing new communications techniques, (b) designing and 

building commercial wireless communications systems, (c) building

communications of many types for the government, (d) space communications,

(e) software radios, (f) international spectrum management and policy, (g)

sensors, and (h) mobile networks. The extensive experience of the task force

members contributed to the comprehensive consideration of the issues and the

recommendations of this report. A list of task force members is provided in

Appendix B.
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The task force addressed three major themes during its study: the current

state-of-the-art in wideband communications systems; current domestic and

international spectrum management and policies; and the integration of radio

systems with networked information systems.

The task force ascertained the current state-of-the-art in wideband systems

from presentations from the academic, commercial, and government sectors. The 

base questions that the task force considered are:

• What are the capabilities of wideband RF systems? Bandwidth? Error 

performance? Covertness? Sharing?

• What is the rationale behind such systems? 

• Why is one able to consider such systems now? What is the enabling 

technology?

• Why might wideband systems perform better than conventional

narrowband RF systems? 

• What impact do these systems have on ”in-place” or “existing”

systems? What is the effect of raising the noise floor?

The presentations heard covered developed and deployed systems,

laboratory prototypes, and research programs and projects. In its estimation, the 

task force adequately covered the current state-of-the-art in wideband

communications.

The second item was to understand the current situation in spectrum

management policy. This involved presentations from several DoD offices, the

FCC, the Department of State, and industry. The current world situation with

respect to terrorism and homeland security provided a context to raise questions 

and understand the issues of this complex policy/technology/capabilities

conundrum.

The third line of examination was the interplay between communications

(links) and mobile information networks. This relationship is crucial to realizing 

the network centric vision of the Joint Chiefs of Staff. The most advanced

information systems are not useful if not inter-linked to many other systems and

capabilities. While the task force considers this an important component of

wideband communications, few expert counselors were available to discuss the 

issues associated with integration. The task force relied on its own judgment in

this area.
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The remaining body of the report is organized into five chapters. Chapter 2

presents two communication models suitable for framing the technology

questions. Chapter 3 reviews current capabilities and emerging technologies

relevant to wideband communications. Chapter 4 addresses each of the terms of 

reference, relates each to the material presented in Chapters 2 and 3, and presents 

the findings of the task force. Chapter 5 is a set of recommendations DoD should 

act upon with respect to wideband RF systems. Chapter 6 presents the

conclusions of the study.
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CHAPTER 2. REVIEW OF RF COMMUNICATIONS, CHANNELS,

AND MULTIPLE ACCESS SYSTEMS

The task force invested a considerable amount of time understanding and

developing a model for how to think about emerging communications systems. 

The task force believes the model presented below aids in framing and

understanding the many complex issues in network-centric communications

systems.

This chapter describes two models, one covering RF resources and the second 

the communications process, that aid in understanding the tradeoffs between

alternate systems and establish the context for further discussion. Each of the

TOR items is then addressed within the established context. The chapter

concludes with a summary of the findings.

Advanced communication systems involve the coordinated use of space,

time, frequency, and signal format (coding) – features of the electromagnetic 

spectrum. These emerging systems offer better utilization of spectrum resources 

and incorporate wideband RF. Achieving the radio communications capacities

necessary for network-centric warfare will require such better use of the

spectrum. Currently, technical trades in communications design are made to

optimize individual features such as link efficiency, bit error rate (BER), and 

range. As the interplay among trade spaces for networking and communication

channels grows, total system efficiency and performance will likely be achieved

by sub-optimizing individual features. Future advanced communications

systems will require the integration of high performance hardware, sophisticated 

signal processing algorithms and network enabled coordination to achieve their 

goals.

In this section, the task force reviews the work showing that RF

communications/networking integration is a necessary endeavor to pursue. To a 

certain extent, some of the material may appear to be tutorial in nature. The task 

force believes a clear exposition of the basics will aid the understanding of the

problem and the evaluation of alternatives. In this section, the capacity of an RF 

channel, the resources necessary to operate that link, the composition of subsystems needed to make a communications link, how design trade-offs are made 
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to achieve desired communications properties, and sharing among multiple

users will be addressed.

RF Propagation

Radio signals are subject to attenuation as they travel through space. The free 

space loss (FSL) equation predicts this loss. The natural free space loss can be

used to limit the extent of radio transmission (e.g. higher frequency, higher loss, 

shorter distance, lower probability of intercept) or constrain the frequencies used 

for communications (e.g. longer distance, lower frequency). The FSL equation is:

FSL = 32.4 + (20 log d) + (20 log f)

In this equation, d equals the path length in kilometers and f equals the

operating frequency in MHz. From the FSL equation, it can be seen that as

distance or frequency is increased, so is the path loss. As the operating frequency 

of a communications signal increases, the ability to communicate to a receiver at 

a given distance decreases if other changes are not made in the communications 

system such as increasing antenna gain or transmit power. As frequency

increases above 8 GHz, rain attenuation and eventually oxygen absorption add

to the signal attenuation. The factor of 20 in the “20 log d” is the loss considering 

a distance measured from a typical vertical antenna. For dismounted units in a

prone position, or for ground sensor mounted antennas, this path loss factor

increases to 40 log d. Also, for non-line of sight (NLOS) paths (e.g. foliage) the

attenuation problem becomes even more severe as the channel frequency

increases. There are tradeoffs in the availability and location of spectrum that is 

usable for specific applications based on the laws of physics.

RF Channel Capacity Limits

A theorem, put forth by Claude Shannon in 1948, states that the capacity of a 

channel (in bits per second) is a function of the bandwidth, the signal strength,

and the noise, given infinite time. The theorem states, for a single transmitter-toreceiver path:

C = B• Log2[1+ S /N]

C is the capacity in bits per second, B the channel bandwidth in Hertz, S the 

signal power, and N the noise power. This equation is extremely useful to
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understand fundamental limits. Data transmission at any rate is possible for an 

arbitrary bandwidth provided an adequate S/N ratio can be achieved in the

receiver. The actual data rate is less than C, and requires a sufficiently involved

encoder/decoder be used to approach C. Therefore, if one wants to increase

channel capacity while maintaining a given bandwidth, two things must be

considered. Either more signal energy per bit must be transmitted or noise and 

interference per bit must be reduces. Depending on the communications link

application, these adaptions could be significant. For instance, for a soldier

mounted radio, factors such as power consumption, size, and weight must be

considered when increasing transmission and/or processing power. On the other 

hand, if the communications link is between two fixed communications towers, 

these factors may not be an issue because the necessary infrastructure can be

planned, installed, and supported. Therefore, one will see throughout this study 

report that channel bandwidth/RF spectrum availability has specific impacts on 

the operational characteristics for a specific application and vice versa.

Shannon’s equation also embodies a number of assumptions. The equation

assumes signals are infinite in time, it says nothing about the spatial extent of the 

signal (i.e. ability to reuse the same bandwidth in a different location), it assumes 

noise is characterized as statistically white and Gaussian noise, and does not

consider the ability to eliminate known interference. While these are “system”

issues, they must be taken into account in considering advanced communication 

systems, many of which exploit these assumptions in Shannon’s Theory. 

RF Resource “Space”

RF communications exists in a feature “space” of frequency, time, spatial

extent, and coding. 
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The Radio Resource Space

• The RF Resource Space 

consists of

• Frequency – the radio 

frequencies used to carry a 

signal

• Time – the time duration a 

signal is transmitted

• Space – the volume over which 

the signal transmission is 

effectively communicated or 

causes interference

• Signal format – the manner in 

which information is encoded 

on the radio frequency signal

RF Resource illustrating a few signals 

in time, frequency, and space. Frequency

Time

Space

TDMA

CDMA

TV

FM

Figure 1.

Generally, interference between communication systems is avoided by

separating different systems along these features of frequency, time, spatial

extent, and coding. Frequency is the common method for separating RF signals. 

Each transmitter/receiver channel (Tx/Rx channel) is assigned a different

frequency. Filtering at the receiver and transmitter eliminate interference from

other Tx/Rx channels on different frequencies. Time is a second way to share the 

RF Resource. Tx/Rx channels agree on specific times to transmit/receive. Given 

sufficient coordination, several Tx/Rx channels can share the same frequency,

spatial extent, and coding. One utilizes spatial extent when one implements

directional antennas or takes advantage of multiple paths between the

transmitter and receiver. Signal coding is the fourth primary means of

multiplexing a Tx/Rx channel into the RF Resource. This form of multiplexing is 

feasible because each transmitter has available more of the resource than

necessary to communicate its information, and pseudo-randomly selects the

portion of the resource that it will use in any block of time. The most common

means of coding is direct sequence spread spectrum (DSSS), however other

techniques, such as ultra-wideband (UWB), are emerging. In DSSS, signals are

spread by applying a pseudo-random code. If the receiver knows the code and is 

synchronized with it, the receiver can separate the desired signal from others that 
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use different codes and communication is possible. Several cellular telephone

systems use DSSS, called Code Division Multiple Access (CDMA).

Coordination between numerous communications systems has generally

taken place through a deliberative and well-engineered process. In the United 

States, this has been through the National Telecommunications and Information 

Administration (NTIA) and Federal Communication Commission (FCC) and

internationally through the International Telecommunications Union (ITU).

While reasonable at the time, these nearly manual processes have resulted in an 

under-utilized RF Resource and an extremely complex set of regulations.

Understanding the RF Resource Space is a first step towards more efficient use of 

this resource.

Broadcast television and radio stations exemplify the sharing of the RF

Resource. In the same region, television and radio stations use different 

frequencies to separate individual channels. However, the same frequency is

reused separated by several hundred miles, relying on spatial extent to attenuate 

signals. Further, TV and radio stations change their transmit power levels based 

on the time of day, adjusting for different propagation characteristics during the 

nighttime.

Using the RF Resource Space, one can visualize the trade-offs between

different communications systems. Each “feature” of the space represents a

primary means of sharing the RF Resource: frequency division multiplexing,

time division multiplexing, spatial multiplexing, and code division multiplexing. 

The RF Resource concept does not eliminate well established physical

constraints, such as propagation loss or the Shannon limit. These, and other

physical constraints, still hold, but the concept of an RF Resource Space enables 

one to characterize and evaluate trade-offs among several options. While this

“space” of frequency, time, spatial extent, and coding is not a perfect Euclidian 

metric space, the task force believes it captures the essence of the resources

available to the communications system designer.

Generalized Communications Process

The throughput of an RF communications channel depends on the

bandwidth, signal power, noise power, and the spectrum resources allocated to 

the channel along with, and on other, information processing factors. Figure 2

illustrates the chain of communications processing.
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Generalized Channel

Compression Error Ctrl Spreading Modulation Transmit

De-Compress Error Ctrl De-Spread De-Modulate Receive

Composite

Channel

Thermal Noise

Mutual Interference

Jamming

Multipath

Other

Information

Source

Information

Sink

Encrypt

Decrypt

Figure 2.

Important factors in this processing chain are:

• Compression of the information (data). Data from the information

source can be compressed using lossless (or perhaps loss techniques

if appropriate) to reduce the number of bits that must be transmitted. 

Typical compression ratios can range from a few percent to thirty to

fifty percent depending on the nature of the data and knowledge

about the data.

• Error correction encoding. Additional bits can be added to the

information to enable the correction of transmission errors. While 

adding additional bits to transmit, error correction encoding allows

operation at lower signal to in-band interference (SIR) levels and may 

avoid retransmissions at higher protocol levels, a very ‘time

expensive’ (high-latency) operation.

• Spreading. Information bits can be ”expanded” where each

information bit is replaced by two or more transmission bits by the

exclusive-or with a spreading code or pseudo-random sequence. The 
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effect is to increase the bandwidth, and ”spread” the transmitted

energy across a wider frequency band. The signal to in-band 

interference ratio (SIR) can be converted to an equivalent signal to

noise ratio (Eb/N) by good spread spectrum processing, with N

representing the effects of both receiver noise and interference, and

being higher than the density of thermal noise alone (No). Spreading 

may be done to increase the SIR or to multiplex several users on the 

same frequency band.

• Modulation. Information bits are used to change an RF signal.

• Transmitter power. The transmitter power is a key factor in

determining the range of communications.

• Transmitter Antenna. The transmitter antenna effects the

communications by its efficiency and, perhaps, focusing the emitted

RF energy in a particular direction using the antenna structure or

signal processing. Transmit antennas can ”steer” a main beam toward 

the receiver and away from possible interceptors by “beamforming.”

• Propagation (Power received). RF energy transmitted is affected by

the environment. Some energy is directly ‘carried’ from the

transmitter to the receiver, some is absorbed by the physical

environment, some is reflected and delayed in arriving at the

receiver, and some is modified in transit. Many things effect the

transmission of the RF energy. The intended signal arriving at the

receiver is a complex result of propagation.

• Interference. In addition to the desired signal, other RF energy enters 

the receiver. Inherent in all receivers is thermal noise, an artifact of

the physical circuit. Other interference includes propagation effects,

other users on the same system, other users on different systems, and 

jammers. All contribute energy to the receiver and make it more

difficult to detect the intended signal.

• Receiver Antenna. The received signal is formed via a possibly multibeam receive antenna. The receiver simply detects all RF energy in

the receiver band.

• De-Modulate. The de-modulation step involves identifying the

desired signal and, optionally, subtraction of noise/interferers. The 

resultant signal is compared against expected values and a decision is 

made to determine if the signal is a 1 or a 0 (Digital transmission is

assumed). Different techniques of modulation and de-modulation 
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will lead to different performance and capabilities, including

occupied RF bandwidth of the channel.

• De-Spreading. If the information was spread before transmission, the 

corresponding inverse de-spreading operation is applied to remove

the effect, before or after de-modulation.

• Error Control. The transmitted data is checked for errors and if

detected, correctable errors are to be corrected.

• De-Compression. The original information stream is recovered once 

the de-compression operator is applied.

The communications process is a complex system and has been ”tuned” over 

time to achieve exceptional results in specific applications. The use of frequency 

modulation resulted in less noise in commercial radio broadcasts. The use of

Quadrature Amplitude Modulation (QAM) has increased the number of TV

channels broadcast over direct satellite services. It is important to recognize that 

all steps in the communications process must be considered in both the design

and the deployment of a robust system.

Crucial DoD Communications Properties

Each step in the communications process described above is controlled by

parameters and there are trade-offs between parameter settings for each step. For 

example, one might increase the effectiveness of error control by adding

additional error control bits to the information stream. Increasing error control

increases the communications overhead, reducing the user data rate. Another 

way to improve error performance is to increase transmitter power. Increasing

transmitter power increases the probability of detection by an enemy.

Parameters of the stages of the communications process are set to elicit

desirable system properties. Such system properties include:

• Jam resistance

• Low probability of detection

• Low probability of interception

• Foliage penetration

• Communications in adverse environments (robust communications)

• Communications distance
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• Communications capacity

These properties are often mutually inconsistent. Improvements in one often 

result directly in degradations of others. Channel processing parameters also are 

constrained by system implementation and deployment criteria, such as cost,

schedule, size, weight, ease of operational use, and power consumption. The

value of each parameter setting can only be established in the context of the

mission, cost of implementation, complexity of implementation, and other

criteria. No single approach, or settings of parameters, will meet all missions.

Communications Channel Sharing

Finally, the task force addressed the issue of sharing the RF Resource Space

among multiple users. The previous sections focused on models for one-to-one 

communications. However, in most situations it is important for many users to

inter-communicate. To increase the utilization of the RF Resource Space, sharing 

mechanisms are employed. Traditional sharing mechanisms, as outlined above,

are frequency division, time division, code division, spatial extent (beamforming), and channel accessing schemes such as Carrier Sense Multiple Access

(CSMA), where users contend for use of the same channel, and so forth. 

When a portion of the RF Resource Space is underutilized, one implements

mechanisms to share the common communications resource. This is possible

when no single information source is sending data continuously, or one wants to 

exchange information between multiple senders and receivers. Generally, some

aspect of the orthogonal, or independent, nature of the RF Resource Space is

used to implement sharing, e.g. frequency, time, spatial extent, or coding. The

effect is division of the finite communications resource among multiple users. If 

multiple users wish to communicate and each one does not require the complete 

RF Resource, then one can increase utilization of the resource, with proportional 

reductions in the capacity available to each pair of users by multiplexing the

multiple users onto the same resource. The multiple users are sharing the limited 

RF Resource.

Spectrum sharing implies an allocation process, or mechanism, to assign a

portion of the RF Resource Space to one or more information transmissions. The 

communications resources can be allocated on a permanent, or static, basis or

intermittent (dynamic or demand access) basis. How this allocation is made

determines some of the properties of a shared communications resource. A

statically allocated resource is likely to show low utilization and low (access)
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latency equivalent to a dedicated communications link. It also may fail

catastrophically when a single critical link is damaged. A demand access system 

is likely to exhibit some delay in allocating the resource and even the possibility 

of blocking a transmission when no resource is available. However, a demand

access allocation process will likely show higher utilization. Only a very few

radio systems utilize dynamic allocation. The cellular telephone system

dynamically allocates resources to users as they initiate a call or move from cell 

to cell. Some land-mobile systems use a “trunking” mechanism to allocate

channels on demand.

The sharing/allocation mechanism includes an architecture describing how

users are interconnected, such as who can communicate with whom, and how

and where the communications resource is allocated. A common architecture is a 

hierarchy. The telephone system is designed as a hierarchy. Users connect to a

central office. The central offices in region are interconnected through a toll

office; toll offices may form a mesh network. Some toll offices connect to

international offices for overseas calls. Given the long time line for

implementation and known, historical traffic loads, the planned and hierarchical 

architecture suits the telephone system just fine. A different architecture is a

completely connected mesh network. The common handi-talkie implements a

mesh network in which each user can send information directly to any other

user. Control of such mesh networks can be chaotic, as with Citizens’ Band

Radio. Hybrid analog and/or digital networks are also possible that are mesh

networks at the lowest level, but each mesh network has a gateway to other

mesh networks.

The architecture and allocation mechanism will determine such properties as 

the following:

• Access latency to the network – length of time from first request to

time of first transmission

• Blocking probability – probability that a request for communications 

resources cannot be allocated

• Transit delay – length of time from sending first bit to receiving first 

bit (i.e. propagation delay across the network)

• Latency jitter – variation in transit delay among a set of transmissions

• Robustness – ability of the network to continue functioning in spite of 

damaged nodes or links, which may be mediated by routing and

internetworking protocols like TCP and IP
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• Setup time – time from first placement of nodes to operational status

• Adaptability – ability of the network to change organization and/or

routine in response to changes in node location or the environment

• Join time – the time and ability for a new user to join an existing

network and includes the necessary authentication and authorization 

checks

• Prioritization of access – gives high priority users first call on

available resources

When many communication links are involved to cover a geographic area,

packet networks provide certain economies in sharing the spectrum through the 

use of adaptive routing.

The high value of a common protocol to exchange information between

networks has been demonstrated by the Internet Protocol (IP). The architecture

of IP calls for a single protocol to exchange packets between networks. Many

different transport mechanisms, such as transmission control protocol (TCP),

user datagram protocol (UDP), and real-time protocol (RTP), can be

implemented on top of IP. Further, many different applications can use the few

transmission protocols and the single IP. IP can be carried on many different

types of networks: wired, optical, radio, et cetera. IP packets are moved through 

a network from the source endpoint, through router to router, to the destination 

endpoint. At each router the header of the IP packet, containing the destination

address, is examined and a decision is made on how to move the packet towards 

its destination. The decision process is implemented by an underlying routing

mechanism and protocol.

Routers exchange information between themselves on which hosts or

networks are reachable from each router using a routing protocol. The ‘best’

routes from a local router to remote networks are (usually) computed at each

router. This approach works well for static or slowly changing network

interconnects. However, it can take significant time for information on a change 

in connectivity to propagate across the network. This leads using outdated 

connectivity information and inconsistent routing decisions across parts of the

network. Rapid dissemination of connectivity information, while improving

routing decisions, could degrade user throughput on low capacity links. Further, 

routing protocols become a significant vulnerability if not suitably protected. An 

attacker breaking the routing protocol could cause significant havoc with just a

few well placed packets.
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Current protocols used in the Internet avoid, for good reason, knowing any

characteristics about the underlying networks. This approach leads to ubiquitous 

connectivity. However, this approach also precludes taking advantage of or

avoiding certain networks for certain applications. This is an issue in a networkcentric architecture. Current routing protocols assume a relatively static network 

infrastructure and are overwhelmed with highly mobile network infrastructures. 

Even protocols that seemingly address mobility, Mobile IP and ad hoc

networking for example, assume a relatively stable infrastructure.

Network protocols and network management for network-centric systems

must also exhibit the following characteristics:

• Robustness – the network should strive to maintain connectivity, 

perhaps at the detriment of other properties. Routing algorithms 

may have to maintain multiple paths between source and

destination and may have to anticipate future routes for highspeed nodes transiting the network. The network should degrade 

“softly” rather than abruptly.

• Security – access to the network should be protected,

transmissions should be protected and authenticated, and “lost 

parts of the network” should be prevented from further

participation.

• Set-up and recovery times – setting up the network should be

automatic and require minimum time, i.e. order of seconds not

minutes, and recovery from significant changes in the network,

e.g. joining two major units, should also be accomplished on the 

order of seconds.

• Network Protection – the protocols and management systems

must be able to deal with attacks on the network in an

expeditious manner. Denial of service attacks, attacks against the 

signaling and control system, unintentional consequences (e.g.

multi-casting high-bandwidth streams across low-bandwidth 

links), among many other events must be taken into account and 

dealt with.

The interaction between radio connectivity, highly mobile networks, and

commodity protocols continues to be a challenging problem.
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RF Communications, Channels, and Multiple Access

The previous sections reviewed the components, or sub-systems, of RF

communications systems. Traditional design approaches work on individual

components and seek to achieve mission critical communications properties

through component design. However, as described above, there is extensive

interaction between components and there are several approaches to achieving a 

particular communications property. The interactions, the multiple tradeoffs, and 

the requirements for wireless communications systems are complex. Few grasp

the entirety of the communications parameter space. The result is a large set of

projects focused on limited portions of the communications parameter space

resulting in a lack of coordination and inter-operation between the individual

systems. This is an extremely difficult task, but necessary given the networkcentric requirements for RF communications.

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CHAPTER 3. SUMMARY OF CURRENT CAPABILITIES AND

ONGOING RESEARCH AND DEVELOPMENT

The following is a summary of current wideband capabilities and ongoing

relevant research and development (R&D). The task force reviewed a number of 

research projects from government laboratories, government research funding

agencies, the commercial sector, and the academic sector. The task force was

impressed with the breadth and creativity of wideband communications systems 

and emerging capabilities. From our study it is clear that government, industry, 

and academia are interested and stimulated by the technical problems in

wideband communications. The set of briefings indicate an excited and dynamic 

research community tackling the major problems in wideband communications.

GOVERNMENT FUNDED RESEARCH

At the basic research level, government offices are supporting all aspects of 

wideband communications. For instance, typical of the basic research efforts in

very high-speed radio frequency circuits are:

• High Power, Highly Efficient, Linear, Wide Band-Gap Semiconductor 

Amplifiers

• 100 GHz Logic for Control and Direct Digital Synthesis to 25GHz

• 1.2 THz switching transistors

• 84 GHz logic

• Direct Digital Synthesis over 5 GHz

• 100 GHz, Ultra-Stable (goal of less than 30fs jitter) Clocks

• Very Wide Operating Band-Width Radiating Elements (Goal of five

to one)

• Low Noise Amplifiers

• Tunable Bandwidth, Tunable Center Frequency Filters

The implications of this effort are that DoD, with continued investment, can 

anticipate increases in capabilities in the RF circuit domain, especially in the
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future of ever higher operating frequencies where thus far uncontested

bandwidth is available. RF circuits will be a significant enabler in future

communications systems and capabilities. Assuming these research projects are

successful, and there is reason to expect they will be, DoD should anticipate a

continual shift from analog processing of communications (and radar) signals to 

digital processing. This shift will be extremely important at the higher

frequencies, above about 10 GHz, but the capability to process signals at higher 

rates will also mean that more complex signal processing algorithms can be

implemented for lower (carrier) frequency systems. Research in complex signal

processing algorithms should be incorporated into future DoD plans for radio

communications. The ability to use digital techniques, such as digital signal

processing, high-speed microprocessors, and programmable gate arrays, will

significantly impact DoD’s communications capability. DoD should continue to

invest in these research areas.

Government research laboratories are also investigating advanced

communications techniques, such as orthogonal frequency division multiplexing 

(OFDM) and ultra-wideband (UWB). OFDM promises increased capacity within 

a multi-frequency system and UWB systems challenge conventional thinking of

radio communications systems and regulations. Approaches that exploit joint

time/frequency/space for modulation and coding, such as the work being

performed at the Air Force Research Laboratory, show great promise for meeting 

the needs of those future systems requiring both agility and increased

performance.

At Government Funded Development 6.2 and 6.3 levels, the task force also

finds extremely interesting and worthwhile projects, but a lack of overall

coordination of the research towards a network-centric system. Each project is

justified as contributing to the goal of network-centric warfare, and is providing 

its contribution. But, it is not clear that many of these systems will inter-operate 

with one another and result in the type of system envisioned. There seems to be 

an implicit assumption that “the network,” as represented by the Internet 

Protocols and ad hoc networking, will tie all of these communications systems

together. That assumption avoids the complexity of ensuring compatible

exchange between systems, multiple system management issues, and welldefined capabilities and properties.

The task force sees the Joint Tactical Radio System (JTRS) program as possible 

bridge between legacy waveforms and future wideband agile radio systems.
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However, the task force saw limited evidence that JTRS is prepared to be this

bridge. JTRS is a procurement program where the effort is to replicate existing

waveforms to interoperate with existing systems without necessarily adding

significant cross-system linking. This focus is constrained by the extended

development/certification/procurement process and the need to work with

existing systems. The JTRS program, while providing radio links, does not view 

itself in the larger network-centric vision, particularly in the area of network

management. JTRS, a software based radio, could be the experimental platform 

to research and develop future advanced radio system concepts. The program

should consider making radios available for experimental purposes to various

research organizations.

The research and development projects performed by the DoD science and

technology community are fundamental to future DoD systems and the task

force does not want to diminish its importance. However, it is the integration, or 

even a plan for integration, the task force finds lacking. If an era of “systems of 

systems” indeed exists, then DoD needs to reflect that in the approach to

research and development projects, especially at the 6.3 and 6.4 levels.

COMMERCIAL RESEARCH AND DEVELOPMENT

The commercial R&D that the task force reviewed fell into three areas: ultrawideband systems, advanced signal processing techniques, and existing and

code-division multiple access systems.

Ultra-Wideband Radio Systems

Ultra-wideband (UWB) radio systems are characterized by a large

instantaneous fractional bandwidth with respect to the center frequency. 

Generally, if the quotient of the difference between the minimum and the

maximum frequencies divided by the average of the minimum and maximum

frequencies is greater than 0.20 - 0.25, the system is considered as ultrawideband. (The upper and lower frequencies are commonly defined as the –10 

dB points of the spectrum, relative to the peak.) The most common mechanism

for generating ultra-wideband signals is to use extremely short current pulses,

commonly called “impulses.” The power emitted at each frequency can be

somewhat adjusted by the shape of the pulse and the repetition rate. Other

mechanisms can also be used to generate UWB signals.
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UWB radio systems offer a number of advantages. First, the natural

frequency diversity of the signal makes it possible for a receiver to do a better job 

of separating the signals coming over different propagation paths to the receiver. 

So for instance, if there were only two propagation paths, a narrowband signal

coming over these paths would be added to itself, and depending on the phasing 

of the carriers, there would either be a strengthening or interfering of the signal, 

and it would look in time like a one-path signal. If the signal were UWB and the 

paths had a reasonable amount of differential delay relative to pulse width, these 

signals can be resolved and processed separately, and the amount of received

energy is more spatially stable. Current hardware is quite limited in energy

capture efficiency, i.e., the ability to use energy from many resolvable

propagation paths, because it usually looks at the signal coming over only one or 

two paths. However, this is not a fundamental limitation, but one that may be

overcome in future radio designs. 

Second, the low power spectral density and wide frequency band provides

covert communications and anti-jam properties, respectively, though these

properties tend to conflict, or not be simultaneously achievable. The presence of 

low frequencies in the signal offers imaging and sensing through walls, and

multiple users can share the same frequencies. The precise timing of received

pulses can be used for precise location and identification, or tagging.

The imaging, location, and identification capabilities are perhaps the most

important applications of UWB. For instance, UWB can be used in inventory

management to locate and catalog equipment in densely packed warehouses or 

shipping containers.

Under current FCC regulations, UWB systems typically operate over a short

range, typically less than 100 meters depending on data rate and propagation 

conditions, though some applications achieve relatively longer distances. This

can be an advantage for covert communications or frequency sharing, or a

disadvantage for larger scale communications systems. With suitable high power 

transmitters, the task force presumes communications over longer distances can 

be achieved, but this is yet to be authorized.

UWB radios challenge radio designers. Systems must operate and be power

efficient over a wide range of frequencies and signal distortion in transmission 

lines and antennae reduces performance. Many UWB systems require a very

precise clock at the receiver for a precise location function. This can be difficult to 
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implement. Detecting and locking onto an UWB transmission may also be

difficult or time consuming.

The energy emitted by an UWB radio is distributed over a wide frequency

range and, hence, there is a very low average power spectral density, or energy 

per Hertz. Some argue that the low power spectral density will not interfere with 

existing narrow band systems and that UWB radios should be allowed to co-exist 

with existing systems. However, many weak-signal systems, including those for 

radio astronomy, radars, receivers for covert transmitters, satellites, signal

intelligence, and geo-location, such as the Global Positioning System (GPS) are

designed to work with very small allowances for interference as they have small 

noise margins. Also, the impact of multiple UWB transmitters on the ambient

noise floor must be considered since a specific S/N must be maintained for a

given bit error rate (BER).

Because of the possibility for interference, the Federal Communication

Commission (FCC) and the National Telecommunications and Information

Administration (NTIA) in the United States, have been reluctant to permit

operation of UWB radios. After significant debate, the FCC and NTIA allowed

use of UWB radios in a limited frequency range and limited power. The emission 

limit for outdoor handheld devices is shown in Figure 3.

Note that the emission limit is at least –75 dBm/MHz between 0.96 GHz and 

1.61 GHz to protect GPS receivers. If it were possible to perfectly fill this FCC

spectral mask between 3.1 GHz and 10.6 GHz, the total equivalent isotropic

radiated power (EIRP) would be less than 0.56 milli-watts. Hence, FCC

compliance is a severe constraint that restricts applications to short range and/or 

low data rate communications. While the FCC will continue to review its UWB 

regulation from time to time, it is not expected that the UWB limits will change 

in the near term.
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0.96 1.61

1.99

3.1 10.6

GPS 

Band

Source: www.fcc.gov

UWB Emission Limit for

Outdoor Hand-held Systems

/MHz

Figure 3.

The primary concern with UWB radio systems is that not enough is known on 

how these systems interact with existing systems. The regulatory community has 

acted on the side of caution. Limiting the knowledge of these systems is the lack 

of production radios as manufacturers are reluctant to commit to production

without knowing the regulations; protection of intellectual property; unknown

system properties (e.g., pulse repetition rate and protocol); and aggregate effects. 

Further, there is nothing in the FCC rules and order that prescribe modulation

formats. As long as spectral masks are satisfied and a few other requirements are 

met, a system qualifies as UWB. Thus, any system that meets the power spectral 

density mask qualifies as an ultra-wideband system. Some studies such as NTIA, 

United Airlines, and the DARPA NetEx Program have preliminary results and

almost all call for further study. Singapore is setting up an Ultra-wideband 

Friendly Zone (UFZ) in their research park, and in that area is considering a

mask similar to the FCC mask, but higher by 6 dB in the 3.1-10.6 GHz band.

In the situation in which some narrowband interferers are present, spectrum 

management algorithms may be needed to manage UWB transmission and

reception. That is, the transmitter and receiver have to cooperate in their

transmission and reception techniques to avoid or mitigate the narrow band
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interferers, such as friendly systems on transmit and receive, unfriendly systems 

on receive.

More research is required to understand UWB radio systems and their

interactions with narrow-band radio systems.

Advanced Signal Processing

Industry is making significant investments in advanced digital signal

processing techniques. One can see this in efforts to (a) develop and standardize 

software-defined radios, such as the Joint Tactical Radio System (JTRS), (b) use

digital processing techniques much closer to the radio frequency front-end (the

circuitry connected to the antenna), (c) build higher capacity systems, and (d)

build more robust systems.

The ability to operate digital circuits at higher clock rates and the increased

density of logic gates per square centimeter enables these systems. US

government laboratories and sponsored research will drive digital processing

and the conversion from analog to digital processing further in the next several

years. The trend not only places radio signal processing on the so called

“Moore’s Law Curve,” a doubling of circuit density every 18 months, but also 

opens up the opportunity to use more complex processing algorithms that are

too expensive to implement in analog hardware.

One example of this trend is the multiple input/multiple output (MIMO)

transmission scheme exemplified by Lucent Technologies’ BLAST system.

BLAST significantly increases the capacity of a point-to-point radio

communications link by taking advantage of the multiple signal paths.

Normally, radio engineers consider multiple signal paths a problem (e.g.,

multipath and fading degradation). However, BLAST purposely uses multiple

signal paths to increase the capacity of the available channel. This is

accomplished using multiple transmitters and receivers along with the necessary 

signal processing. BLAST requires significant, and continuous, ‘sounding’ of the 

channel and updating of the channel characteristics to achieve a significant

capacity improvement over a single input/single output communications link.

There are operational impacts which must also be addressed, such as the

additional transmit/receive pairs for each antenna element, and the number of

elements allowable on a given communications platform. Factors such as weight, 

size, power consumption and ease of operation must also be considered.
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Space/time processing, in which one uses multiple antennas and transmits the

same data at slightly different times, can improve the robustness of the

communications channel. Most people have experienced the dropout of a radio,

such at FM or cellular, channel while in a particular position. Slight movement in 

any direction removes the problem. This is signal fading usually due to multiple 

propagation paths canceling each other. STEP offers a range of techniques to

reduce or eliminate these effects and maintain the communications link.

A second important signal processing technique is that of identifying

interfering emitters and, by identifying those emitters, eliminating, or

subtracting, their signal from the intended received signal. This is an extremely 

powerful technique. The technique can be used to increase the utilization of the 

RF Resource Space of multi-user systems and can be used to eliminate known

emitters in the area. The technique implies knowledge of other users and

interferers and those signal characteristics. Advanced theoretical work is

developing new techniques and algorithms to determine the structure of signals

without prior knowledge. These techniques could be used to adapt to the local 

environment. Operational impacts must also be considered, if there is a need for 

additional antennas and other RF components.

It is important to realize that the transition from analog to digital processing 

is not just a replacement of the analog algorithms with digital implementations. 

The incorporation of digital techniques at the most basic radio signal processing 

levels allows one to use significantly more complex algorithms which result in

significantly increased communications system capabilities and properties. The

task force will discuss the interaction of these advanced radio signal processing 

techniques with higher level network services later in a following section.

Second, these advanced signal processing techniques require significant

processing, or computing, power and there is a corresponding size and power

requirement to implement these techniques.

Code Division Multiple Access Systems 

The task force surveyed many types of ‘wideband’ techniques and the

associated spread spectrum and multiple access methods. The term spread 

spectrum refers to the process by which the bandwidth of the RF transmission is 

increased substantially beyond the minimum required to transmit the

information in a particular modulation scheme. Multiple access describes the
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manner in which multiple user signals are transmitted through a common

channel in a substantially non-interfering way.

The two most commonly encountered methods of spread spectrum (SS) are

direct sequence spread spectrum (DSSS) and frequency hopping spread

spectrum (FHSS).

DSSS systems, sometimes called pseudonoise (PN) systems, employ a key

generator to produce a high speed binary code sequence. An information signal 

is combined with this code sequence. This composite signal is then used to

modulate an RF carrier. The code sequence determines the RF bandwidth,

resulting in a spread spectrum signal. At the receiver another key generator

produces a replica of the transmitter's code sequence, and the incoming RF signal 

is multiplied with this sequence. This collapses the RF bandwidth into a

bandwidth which is commensurate with the information alone. Conventional

narrowband demodulation techniques are then used to recover the information

signal from the RF carrier. The critical problem in direct sequence systems—

acquisition—is to synchronize the transmitter and receiver key generators

[FCC1981].

In FHSS, the carrier frequency is periodically switched to a new value within 

a spectral region much larger than the baseband bandwidth of the data-bearing 

signal. A receiver ‘dehops’ the input signal to recover an IF or baseband version 

of the information.

A third method, time-hopping (THSS), deserves mention because of its

relationship to another technique that was considered by the task force. In THSS 

information is modulated onto a pulse whose duration is very short compared to 

the inverse of the information data rate, and the location of the pulse changes

pseudo-randomly within the allocated pulse slot from transmission to

transmission. Because of the short pulse use, THSS resembles ultra-wideband 

(UWB) techniques. In its wideband review, however, the DSB chose to

distinguish between spread spectrum and UWB systems on the basis of the

typical service volumes associated with each in terrestrial applications—spread 

spectrum techniques, as used in cellular telephony or wireless LANs operate

over tens of miles, whereas the range of UWB is usually on the order of tens of

feet.

Hybrid SS systems can be constructed—as an example, a DSSS code can be

frequency hopped over a wider bandwidth to create DSSS/FHSS. 
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In a communication channel dominated by receiver noise the various

spreading methods offer little to choose among in terms of typical performance 

measures—e.g. error rates for the bit, word, or frame. Such comparisons should 

be drawn under circumstances of equal processing gain, conventionally defined as 

the ratio of the spread bandwidth to the information data rate. Where

distinctions may arise among SS techniques, however, is in their antijam or

detectability properties.

The allocation of AM/FM radio channels is an example of (non-spread 

spectrum) multiple access, in this case in the frequency domain; this may be

called frequency-division multiple access (FDMA). Access by time slotting is

TDMA; that by multiple, co-channel DSSS codes is CDMA. The ability to

distinguish among signals on the basis of their strength at the output of a receive 

antenna gives rise to space-division, i.e. SDMA. Discrimination may be based on 

either physical (path loss) or angular (antenna pattern) separation. As for SS,

hybrid access techniques are formed from combining two or more of the basic

types, e.g. CDMA/TDMA.

Any form of multiple access may employ either a deterministically assigned

or contention-based method of access. That is, access may be granted by an

authority following a request, or open channels may be seized under control of a 

protocol that eventually resolves the contention and grants exclusive use to one 

user in the short term. A generic example of contention access is carrier-sense 

multiple access (CSMA), in which a receiver scans channels, looking for energy, 

and may attempt to access any channels found not in use. The distinction

between the two methods is really based on whether contention is resolved

before or after RF transmission in the communications channel commence.

The task force reviewed several CDMA systems, both commercial and

military oriented, see Table 1. The systems examined primarily use DSSS

modulation and CDMA techniques to achieve various system properties, e.g.

multiple users, covert communications, low probability of intercept (LPI), low

probability of detection (LPD), anti-jamming (AJ).

The task force believes that a joint appraisal of the status of both military and 

commercial communications systems is key to developing appropriate guidance 

for future government developments. More than ever, the technology bases of

the two arenas overlap, and the capabilities offered by commercial systems

become of great interest in an era where the government increasingly relies on
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out-sourced services rather than proprietary systems. These issues are

sufficiently important that three years ago the DSB itself addressed them in a

report devoted to “an examination of private sector sources of technology,

acquisition support and test and evaluation as well as processes for obtaining

private sector support” [DSB2000-6].

Government 

Program

Commercial 

Program

GPS Omnitracs

JTIDS Globalstar

NTDR IS-95

FCS-C cdma2000

DSCS W-CDMA

TDRSS IEEE 802.11b

CDL

JTRS

Table 1. Representative government and commercial CDMA systems.

CDMA had been used in military systems since the 1970’s and developed into 

a digital cellular telephone system standard, known as Interim Standard-95 (IS95) by the 1990’s. It may be noted that commercial utility of spread spectrum had 

been advocated to the FCC long before the advent of IS-95. In a 1981 report on

the efficient modulation, the FCC observed, “The low power density and

interference suppression capability of spread spectrum systems suggests a

unique application,...band overlay. It may be possible in some circumstances to 

overlay spread spectrum systems on spectrum used by conventional services

with little or no mutual interference....Short range systems, such as cordless

telephones, might prove ideal for such an application” [FCC1981]. In this and

related passages in the report, the FCC uses the term “spread spectrum”

narrowly, essentially equivalent to the present use of “CDMA.”

Justifications cited by FCC for this viewpoint remain valid today, some 

having assumed increased importance. Among them are selective addressing,

uncoordinated sharing of a frequency channel, low power spectral density,

ability to track a spread spectrum transmitter and interference rejection. Among 

all discussed properties, only one, which related to spectral efficiency, bears a
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cautionary note concerning the potential impact of mutual interference and the 

near-far effect on spectral efficiency.

To the FCC’s favorable citations, others may be added that are derived from

DoD’s projected needs for autonomous, net-centric communications in a serviceon-demand environment. Among the reasons why CDMA merits consideration

as an enabling technologies for future DoD networks are: (1) high data rate, AJ,

LPI, LPD and mobile ad hoc networking (MANET) capabilities have been

demonstrated in prior programs; (2) a large DSSS commercial base exists to

leverage commercial investment; and (3) CDMA in its hybrid forms is well suited 

for the envisioned (advanced and dynamic) spectrum management options in

the future. In defense of the latter claim the task force noted that the absence of 

world-wide, dedicated, primary-use spectrum to service all DoD needs drives

the pursuit of a spectrum aggregation policy to implement the derived

communication requirements, mandating that the supporting technologies

exhibit features and flexibilities compatible with that approach.

The need for novel spectrum access methods for DoD is presupposed on the 

basis that it seems unlikely that answers to DoD’s future spectrum needs are to

be found within the currently accepted U.S. and international spectrum access

regulations. Mounting evidence for this can be found domestically in recent

reports of the Spectrum Policy Task Force (SPTF) of the Federal Communications 

Commission (FCC), in which the SPTF examines current spectrum usage models 

and, upon considering documented evidence that there is considerable and

somewhat unpredictable amount of peak-to-average usage fluctuation in a

variety of assigned bands, including some of the most sought-after U.S.

spectrum—the VHF/UHF public sector allocations—finds it reasonable to begin

addressing alternative access paradigms exploiting previously unused allocation 

dimensions, such as time and in-band noise floor, or interference level, to

improve the efficiency of spectrum use [FCC2002-11].

CDMA, as represented by the Qualcomm-developed IS-95B cellular

telephony standard, constitutes high-visibility proof that CDMA systems will

work up to their theoretically anticipated limits in the real world. IS-95B employs 

one form of CDMA—single carrier—among several varieties, and though not

fully representative of the scope of offered capabilities, commercial CDMA does 

illustrate many of the best usage modes for CDMA in other contexts.
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MeshNetworks, Inc. has developed an ITT Industries patent into a

commercial CDMA hybrid called Quadrature-Division Multiple Access

(QDMA). Using simultaneous transmission of a communications channel and a

control channel, each spread by different PN codes, QDMA facilitates restricting 

communications on the network to a particular conversation mode and between 

identified radios. Transmissions are performed in a network-referenced time

division duplex format having 16 slots per second. A user radio (the one

initiating transmission) becomes a network controller that maintains power

control and time synchronization, normally functions allocated to a base station. 

A network control station can voluntarily or by command transfer control of the 

network to any of the other radios on the network. Carrier-sense multiple access 

(CSMA) lets radios contend for open slots until one of the radios captures the

slot.

QDMA partially addresses some major concerns for military CDMA, in

particular the normal requirement for a base station of unique capability that

consequently becomes a single-point failure liability. It accomplishes this by

shedding throughput to avoid the hard timing issues of OCDMA, replacing

orthogonality in code and frequency by that in time. This approach, undoubtedly 

not a turn-key solution for DoD, contains elements of interest and should be

extrapolated to scenarios modeling future DoD requirements.

The task force finds the following aspects of CDMA favorable to the needs of 

future DoD networking:

• CDMA implements flexible channelization in which capacity

saturation is approached gradually rather than abruptly as may occur 

in fixed-allocation TDMA or FDMA

• Multi-carrier CDMA and other hybrids incorporating filter bank

technology offer the potential for non-contiguous band allocation

and/or novel approaches to frequency diversity

• Efficient techniques for accommodating data rate variations versus

time exist and are likely to be refined in the commercial sector

• When typical MANET issues such as flexibility, connectivity, 

availability, and equality of resources for all net members are of

greater concern than operation near a throughput maximum,

CDMA/TDMA hybrids offer operation without near-far interference 

or requirement for a fixed-function base station—an example is

QDMA; hybrids deserve increased attention in connection with
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programmable signal formats, since different (or differently

parameterized) hybrids may serve some applications better than

others

• Unlike frequency-hopped systems, CDMA is instantaneously

wideband and thus has somewhat greater resilience to sophisticated 

jamming and detection threats

• Beyond their function in communications, CDMA signals can

provide timing (or pseudo-range) measurements that may augment a 

host platform’s navigation and guidance system(s)

Lingering questions about CDMA identified by the task force include:

• High throughput requirements are typically met via hub-spoke 

architecture, which places a significant burden on the hub—or base

station— node, creates undesirable single-point vulnerabilities and

forces a symmetrical frequency-division duplex spectrum allocation

requirement

• Despite the great variety of architectural, signal format and protocol 

fixes to be had, non-orthogonal forms of CDMA are always subject to 

service degradations brought on by the familiar near-far problem

• Use of orthogonal CDMA (OCDMA) can eliminate near-far effects

within a controlled subnet; synchronization of multiple transmissions 

for orthogonality is easy, but adjusting receive times when multiple

sources transmit simultaneously may require additional timefrequency measurement and control overheads that rob capacity

while increasing a terminal’s processing load; OCDMA is promising

but untested

• Although power control can mitigate much potential interference,

either within subnet or to other uncoordinated subnets, further

research is needed to determine the extent to which power control

complicates MANET CDMA

• Legacy operating procedures inherited from the commercial CDMA 

world are less than fully appropriate to MANET situations—see 

Table 2; realization of CDMA’s potential relies on synergistic

development of related network technologies
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Cellular Network Ad Hoc Network

Fixed, pre-located cell sites and 

base stations

No fixed base stations, very rapid 

deployment

Static backbone network 

topology

Highly dynamic network topologies 

with multi-hop

Relatively benign environment 

and stable connectivity

Hostile environment (losses, noise) and 

sporadic connectivity

Detailed planning before base 

stations can be installed

Ad hoc network automatically forms 

and adapts to changes

Table 2. Differences between ad hoc and cellular networks.

These differences between commercial cellular networks and mobile ad hoc

networks mean that it would be difficult to directly apply commercial CDMA

cellular technology to DoD mobile ad hoc networks.
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CHAPTER 4. TASK FORCE FINDINGS

TOR ITEM 1: TECHNICAL ISSUES ASSOCIATED WITH WIDEBAND RADIO 

FREQUENCY MODULATION

The TOR states: The Task Force will identify the technical issues associated

with the employment of Wideband RF modulation by the Department of Defense and 

defense-related agencies and its potential impact on other defense and non-defense 

users of the RF spectrum. In particular, the implications of DoD use of Wideband RF 

modulation as an alternative to a requirement for additional RF spectrum

allocation(s) for the DoD should be assessed.

Chapter 2 described models of communication channels to better understand 

complex radio communications systems and Chapter 3 reviewed the state-of-theart of communication sub-system technologies, respectively. The important

findings of this review are:

• Radio and networking technologies are available to implement and

deploy wideband communications platforms.

• Future radios must be designed as an integrated system rather than

independent components and designed to interoperate with a broad 

range of platforms. Communications technologies from antennas to

network protocols, and everything in between, must work together as 

a seamless whole.

• Future radios will coordinate activity over a network to increase

capability.

• Radio communications platforms should be adaptive and readily

configured to DoD mission needs.

• Computer-based signal processing will significantly increase radio

platform capabilities.

• Adaptability and increased capabilities are necessary to meet DoD

wireless capacity needs and reduce demand for additional RF

spectrum.
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The task force conclusion from this review is that wideband RF systems are

ready for advanced development and deployment.

Wideband RF technologies will be used to meet a number of DoD missions –

high capacity links, reduces transmission errors, covert communications,

spectrum sharing, and multiple access. However, meeting these missions

simultaneously with a single approach is not feasible. For example, covert high 

capacity links are unlikely, as are many users networked together sharing, while 

not interfering with, another allocation. Wideband RF technologies, along with

tunable radios and networked management, provide DoD with the mechanism

and opportunity to meet its varied missions.

As reported in Chapter 3, the task force examined a number of commercial

and military CDMA systems. Almost all of these systems were designed for a

single purpose and defined infrastructure. One does not find in these systems the 

agility believed necessary in a network-centric mission. Many of these systems

are point-to-point or point-to-hub architectures that rely on a media access

control (e.g. IEEE 802.11b) or on orthogonal spreading code and strict power

control (e.g. CDMA cellular). Media access control is a RF resource allocation

mechanism for sharing the same spectrum among multiple users. CDMA cellular 

systems require strict power control to minimize interference between users. No 

one has worked out the details of how CDMA might actually work in a highly

mobile, ad hoc network.

Chapter 3 also discusses the need to integrate network based management

and flexible radio links. The task force found little work in this area. There is

some work in the U.S. Army/DARPA Future Combat Systems Communications 

program on managing directional antennas, but in general, the ad hoc

networking community is mostly concerned with simple routing issues and

assumes unidirectional antennas and a simple receiver range. Directional 

antennas, frequency flexibility, modulation flexibility, coding, i.e. the

components of the generalized communication channel, have not be considered. 

Bringing these factors into a mobile network management mechanism is a

complex problem that must be addressed to realize the potential of wideband

systems.

Electronic technologies are available to build wideband RF systems. The

behavior of individual components is well understood. To achieve the dynamics 

necessary for network-centric warfare requires tunable radio components and

network based management systems. Through focusing on these issues, DoD
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should increase it utilization of RF spectrum and achieve it’s vision of networkcentric warfare.

TOR ITEM 2: REVIEW THE TECHNICAL ISSUES ASSOCIATED WITH SPECTRUM 

MANAGEMENT

The TOR states: The review of the technical issues associated with the

employment of Wideband RF modulation by defense related agencies should take

account of the concurrent interagency review of spectrum requirements for advanced 

wireless mobile services led by the National Telecommunications and Information

Administration and the Federal Communications Commission.

The situation in spectrum management policy can best be characterized by

”many actors, no director.” The distributed nature of spectrum management in

the U.S. Government makes it difficult for any one entity to take the lead in

spectrum policy and management reform. The actors are the Department of

Defense, the Federal Communications Commission, the National

Telecommunications and Information Agency, other agencies, the commercial

sector, and private think tanks and individuals.

Department of Defense Spectrum Management

The Defense Science Board raised the issue of spectrum management in a

study published in November 2000 titled, “Coping with Change: Managing RF 

Spectrum to Meet DoD Needs.” This report initiated some changes within the

Department of Defense and raised the issue of spectrum management and policy 

as it relates to national defense and economic development. The report is the

basis of a number of discussions on future spectrum management and policy.

Within the Department of Defense, the Defense Spectrum Office was

organized under the Director of DISA and a new Office of Deputy Assistant

Secretary of Defense (DASD) for Spectrum, Space, Sensors, and C3 Policy was

created. These offices coordinate activities between the Office of the Assistant

Secretary of Defense for Network Information and Integration (ASDNII) and the 

Joint Staff. The Defense Spectrum Office (DSO) consists of a National Team, and 

International Team, and an Emerging Technologies Team. These teams handle

most of the day-to-day spectrum management decisions. The DSO works closely 

with the Joint Spectrum Center which directly supports operational spectrum
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management, maintains an extensive international spectrum management

database, and manages electromagnetic environmental effects (E3).

While these new offices are encouraging, it continues to be unclear which

office speaks for the Department of Defense on spectrum management policy

matters. These organizations need to:

• Define long-term spectrum requirements, policy, and usage;

• Define immediate-term spectrum requirements, policy, and usage;

• Ensure all existing and new programs have a consistent plan

addressing current and future spectrum needs;

• Catalog all current and planned spectrum usage by DoD systems;

• Catalog all international spectrum usage;

• Ascertain future/immediate conflicts between DoD systems/

programs and global commercial directions, needs, and directions;

• Engage at a high level in international forums/standards for

emerging wireless communications systems;

• Continue support to operational units in the field;

• Continue investigation into electromagnetic environmental effects

(E3) and interference between existing systems and existing systems 

and emerging systems (e.g. ultra-wideband);

• Develop a plan for emergency and wartime spectrum usage.

Federal Communications Commission Spectrum Policy 

Management

The Federal Communications Commission (FCC) manages all spectrum for

Commercial and State and Local Governments including Broadcast, Cellular

Telephone, Industrial and Public Safety.

The FCC initiated a study on spectrum policy coordinated by the “Spectrum 

Policy Task Force.” The task force submitted a report to the commission in

November 2002. The report is still under consideration. The task force was

challenged with the task of “improving the way that the electromagnetic radio

spectrum is ‘managed’ in the United States.” The FCC task force followed FCC

procedures and solicited comments from interested parties and held open
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forums. The Spectrum Policy Task Force (SPTF) reported the following major

findings and recommendations (quoted):

• Advances in technology create the potential for systems to use spectrum 

more intensively and to be much more tolerant of interference than in the

past.

• In many bands, spectrum access is a more significant problem than physical 

scarcity of spectrum, in large part due to legacy command-and-control 

regulation that limits the ability of potential spectrum users to obtain such 

access.

• To increase opportunities for technologically innovative and economically

efficient spectrum use, spectrum policy must evolve towards more flexible

and market-oriented regulatory models. 

• Such models must be based on clear definitions of the rights and

responsibilities of both licensed and unlicensed spectrum users, particularly 

with respect to interference and interference protection.

• No single regulatory model should be applied to all spectrum: the

Commission should pursue a balanced spectrum policy that includes both

the granting of exclusive spectrum usage rights through market-based 

mechanisms and creating open access to spectrum “commons,” with

command-and-control regulation used in limited circumstances. 

• The Commission should seek to implement these policies in both newly

allocated bands and in spectrum that is already occupied, but in the latter

case, appropriate transitional mechanisms should be employed to avoid

degradation of existing services and uses.

In general, the FCC SPTF recommendations are reasonable. However, this

task force is concerned with “pure” market approaches. In a ”pure spectrum

market,” DoD would compete with commercial interests for access to spectrum. 

Our concerns are that without a clear definition of the market (e.g. who can

enter, the cost of entry, and the rules of the market) it is difficult to commit to a 

market approach. In a “pure market” approach DoD would submit to funding

sources to maintain and innovate in spectrum resources. A British study

[Cave2002] recommended “spectrum trading” for commercial purposes, but

recommended an approach of “government reserving spectrum” for public

services, such as “defense, the emergency services, science and aeronautical

radar.” There should be a distinction between allocations and licensing. As

spectrum is allocated internationally, it would be difficult for a country to

depend on market allocations, which could be quite different from the ITU

International or Regional allocations. 
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The FCC has initiated a national discussion of spectrum policy and

management. The Department of Defense must track these efforts; anticipate its

needs and potential conflicts; coordinate with emerging service efforts; and

clearly state its reasoned positions to ensure cooperation and coordination with 

the efforts at the FCC.

National Telecommunications and Information Agency 

Spectrum Policy

The National Telecommunications and Information Agency (NTIA) is

responsible for coordinating all Federal Spectrum, including DoD Spectrum,

through the Interagency Radio Advisory Committee (IRAC). IRAC has twentytwo members including three from DoD, which is a small representation

considering DoD’s spectrum needs compared to most of the others member

agencies. NTIA coordinates with the FCC on an informal basis to bring

coherence to federal spectrum management. The task force found little effort

from NTIA on addressing future spectrum needs and management.

Reports from the General Accounting Office

The General Accounting Office (GAO) has issued two reports on spectrum

management affecting DoD spectrum. The first, “Defense Spectrum

Management: More Analysis Needed to Support Spectrum Use Decisions for the 

1755-1850 MHz Band” [GAO2001] reviewed a number of studies, including DoD 

and industry studies, related to interference and possible sharing of this band.

The report concluded that the information available and models for predicting

interference and the impact of sharing spectrum were insufficient to make sound 

decisions. Understanding the capabilities of the systems occupying this band,

interference models, and possible sharing or re-allocation strategies continues to 

be studied by several government agencies and industry groups.

The second report [GAO2002], “Telecommunications: Better Coordination

and Enhanced Accountability Needed to Improve Spectrum Management,”

provides an “overview of the development of the legal and regulatory

framework for spectrum management at the federal level and assess key issues

associated with spectrum management at federal agencies.” The report points

out that the “FCC and NTIA’s efforts are not guided by a national spectrum

strategy” and “the challenges the United States faces in preparing for World

Radio-communication Conferences...have raised questions about the adequacy
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of the United States’ preparatory process.” Further, spectrum management

within federal agencies is hindered by staffing and resource shortages.

A third GAO report was released in January 2003 [GAO2003]. This report,

“Comprehensive Review of U.S. Spectrum Management with Broad Stakeholder 

Involvement Is Needed,” focuses on spectrum management issues. The report

examines,

market-oriented approaches to spectrum management and other 

issues. Specifically, this report discusses (1) concerns about 

whether future spectrum needs can be met, given the current 

regulatory framework; (2) the advantages of market-based 

mechanisms and how they have been applied to help meet future 

spectrum needs; (3) whether there are difficulties with using 

market-based mechanisms; and (4) if it is found that fundamental 

spectrum reform is needed, whether the current regulatory 

environment is conducive to facilitating such reform.

The report recognizes that a number of discussions and reviews of spectrum 

policy and management are underway. However, the report indicates, “it does

not appear likely that timely reforms can be agreed to amid the diversity of

views held by stakeholders.” Further, no single agency holds the decisionmaking authority. The report recommends the formation of an independent

commission “that would conduct a comprehensive examination of current U.S.

spectrum management.” The commission should involve all relevant

stakeholders.

The GAO reports and their frequency indicate there is increased interest from 

Congress in the spectrum management and policy issue and the probability of

actions in this area in the near term is likely. The DoD should be aware of this

activity and anticipate and participate in all discussions related to spectrum 

management with Congress and the GAO.

Department of State

The Department of State maintains a small office for International

Communications and Information Policy (CIP) and “has the authority and the

ultimate responsibility for establishing foreign telecommunications policy”

[Gross2002]. A primary responsibility of this office is the coordination of the U.S. 

position on international spectrum allocations and policy.
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International spectrum management is carried out at the International

Telecommunication Union's (ITU) World Radio-communication Conference

(WRC). The ITU is a United Nations organization that establishes world

telecommunications standards, radio frequency allocations, satellite positions,

and telecommunications rules. The WRC operates under a one nation/one vote 

rule and results of the WRC are formalized by international treaty. To achieve

the goal of a winning vote on its position, the United States must form coalitions 

that will support its position. Depending on the nature of the U.S. position or

opposition to, the United States may find it necessary to have bilateral and

multilateral meetings with many countries prior to and during the Conference.

Many nations in a region vote as a block and do so to seek economic and/or

political advantage. Not all nations share the same needs as the United States has 

for global operation of radio systems for national security purposes, therefore,

finding support is sometimes difficult and time consuming.

CIP coordinates with NTIA, FCC, and other federal agencies to develop

positions and proposals for the WRC. The next WRC was scheduled for June

2003 and preparations started shortly after the last WRC. The United States

continues to be hampered by the fact that the head of delegation to the WRC is

appointed only a few months before the meeting. Therefore, the head of

delegation has little time to understand the ITU procedures, the issues, and

history; organize the delegation; and meet the other delegation heads before the 

actual meeting.

The organization for the next WRC appears much improved over previous

years. However, the process needs continued improvement with respect to long 

term planning, working with other nations and regional groups, commercial

interests, and balancing U.S. security needs versus commercial endeavors.

Spectrum Policy, Management, and Organization 

Discussions

There continue to be many discussions and forums addressing spectrum

policy, management, and organization. DoD appears to be an active participant 

in these discussions and forums. Because spectrum management is receiving

much broader interest from the various stakeholders, it is beginning to attract the 

attention of Congress. Many recognize the importance of spectrum for economic 

development and DoD must understand these forces and clearly articulate its

operational needs and requirements.
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TOR ITEM 3: IMPLICATIONS OF EMPLOYING WIDEBAND RF MODULATION

The TOR states: Implications of the employment of Wideband RF modulation

for U.S. positions at the future WRCs should be identified and assessed.

The radio communications systems for network-centric warfare must operate 

in, and be compatible with, a global framework of commerce, national

sovereignty, and mission success. Figure 4 illustrates many of the operational

situations U.S. warfighters will encounter.

Communications Operations

Military

Operations

Hostile Action Over-flight/

Forward Sppt

Peacetime

Training

Homeland

Defense

Peacetime

Training Police Action

CONUS OCONUS

• Comm’l users

• FCC, NTIA, IRAC

• Emergency

Priorities/

Powers???

• Treaty

Restrictions

by Country

• Coordination

with Allies,

Coalitions

• No restrictions

in-theater???

•Coordination

with Allies,

Coalitions

• Treaty

Restrictions

by Country

• Coordination

with Allies,

Coalitions

• Treaty

Restrictions

by Country

• Coordination

with Allies,

Coalitions

OPERATIONAL RADIO RESTRICTIONS

Figure 4.

Military operations span a wide range of activities. These operations take

place inside the continental United States and outside the United States. Each

type of operation and location places restrictions on the radio spectrum and

communications capabilities that can be used and the way in which they can be 

used. Inside the United States, activities such as training and test and evaluation 

must conform to established domestic frequency allocations. In a homeland

defense operation, communications with civilian authorities will be required and 

this will likely require interoperation with non-DoD, non-federal radio systems.

Outside the United States, the military encounters spectrum usages constraints
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depending on geographic location and activity. Almost all operations outside the 

United States will require interaction with coalition partners, whether a joint

operation or access to facilities. Communications with coalition partners will

have to conform to established allocations and rules in the locale. These

constraints will hold even if the military is involved in a hostile action in theater. 

While there may be no restrictions or U.S. imposed restrictions in theater,

military units most likely will encounter restrictions en route.

Another area where restrictions will apply is in training. Although a tactical 

communications system may have the capability to provide significant range and 

data rate in the United States, its capabilities may very well be restricted 

worldwide outside the U.S. borders, where effective radiated power (ERP),

which is antenna gain plus transmit power, restriction will most likely exist. For 

example, restrictions occur while operating in the 2.4 GHz Industrial, Scientific, 

Medical (ISM) band where ERP for most of the world outside of the United

States is limited to 10 – 100 milliwatts whereas a maximum of 4 watts is allowed 

in the United States.

Further, DoD must be aware that any significant disruption of other

government or commercial services due (or even perceived due) to DoD

operations will not be dealt with in the technical arena, but in the media,

political, commercial, and diplomatic arenas. Incidents will be transformed from 

technical issues into political issues. And, even if the technical problems are

resolved quickly, the political issues will have a long ”half-life.”

Regulatory Issues

The Defense Science Board Report on Spectrum Management [DSB2000]

described in detail the interaction between the Federal Communications

Commission, the National Telecommunications and Information Agency, the

Department of State, and international bodies. The organizational chart is

illustrated in Figures 5 and 6. 
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Federal Communications 

Commission (FCC)

National Telecommunications and 

Information Administration 

(NTIA / DoC)

Private Sector /

Public Safety

Federal

Users

Executive Branch Independent Agency

Interdepartmental

Radio Advisory

Committee (IRAC)

DoD has three seats of 22

Informal Liaison

U.S. Spectrum Management Structure

Figure 5.

Since publication of the DSB Spectrum Management report of December 2000, 

the issue of spectrum management policy has increased in visibility. Some of this 

attention is due to interest in fielding new wireless services by the private sector. 

Additional attention is brought by the immense cost incurred during recent

spectrum auctions. Several organizations, including the FCC Spectrum Policy

Task Force and the Center for Strategic and International Studies Commission on 

Spectrum Management are reviewing spectrum management policy and

discussing possible new approaches. DoD is involved and should continue to be 

involved in these activities.

As described above, the Department of State is involved with international

spectrum policy issues and maintains a small office following those issues. While

this office follows the issues, the United States continues at a disadvantage in the 

international forum because its ambassador is appointed shortly (less than six

months) before the ITU World Radio Conference. Subsequently, there is

insufficient time to build the long-term relationships necessary in this forum and 

be aware of the issues and implications of proposed actions.
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While at the time of the DSB Spectrum Management Study (1999-2000) the

telecommunications industry was extremely active and ”economic security”

appeared to be reaching par with national security, the events of September 11, 

2001 have shifted the focus back to national and homeland security. While this

focus is fully justified, that does not eliminate pressure from the domestic private 

sector or the global private sector on spectrum resources and it adds to the

requirements that DoD be capable of inter-operating with domestic public safety 

and law enforcement agencies. 

Federal Users

NTIA FCC Private Sector

Public Safety

State

Department

International 

Telecommunications 

Union (ITU)

World Radio

Conference (WRC)

U.S. and International Spectrum 

Management

Figure 6.

The effects seeking additional spectrum resources the task force has seen and 

will continue to see include:

• Governments will support the growth of their industries in the

wireless market by seeking global frequency allocations for new

services,

• Domestic and international corporations will support global

frequency allocations for new services to remain competitive through 

multiple ”national bases”,
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• Corporations will use international standards bodies to embody

global allocations and services,

• Corporations will use the U.S. organization and regulatory

framework to embody global allocations and services, and

• Corporations will use lobbying efforts on regulators, federal

departments, and Congress to achieve global allocations and services.

These are not necessarily new techniques, but a divergence of national

policies may make the effects more intense. DoD must understand the sources of 

spectrum resource pressure and where and how that pressure is brought to bear. 

ASDNII recognizes many of these issues in their “Electromagnetic Spectrum

Management Strategic Plan” [DOD2002]. Likewise, the regulatory bodies must

understand the impact of frequency spectrum availability, and where in the

frequency band it is available, on the operational capability of the warfighter.

Operations in the Regulatory Environment

DoD will continue to encounter conflicts in the regulatory arena. These

conflicts will arise from the complexity of the DoD mission, recently increased by 

the new emphasis on homeland security. Domestic economic interests to provide 

new services and global businesses interested in seamless inter-operability will

continue to challenge DoD spectrum resources. DoD must be an articulate voice 

for its worldwide needs in these various forums and be prepared, through

advanced radio technology, to adapt to adverse decisions and environments to

the maximum extent possible

TOR ITEM 4: NETWORK SERVICES

The TOR states: The technical impact of the DoD employment of Wideband RF 

modulation on future mobile wireless networking and other users of the RF spectrum

should be identified and assessed.

Integration of wideband RF communications systems with information and

networking services is crucial to network-centric warfare. This integration will

result in new capabilities, including direct sensor-to-shooter communications, 

adaptive radio communications systems, and rich information services.

Wideband RF systems are crucial to achieving these capabilities because they

provide the agility necessary for many future missions. Wideband RF systems
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can provide high data capacity, robust communications, and non-contiguous 

spectrum utilization, but perhaps not at the same time.

There are three forces pushing wideband RF communications systems and

networking services together into a synergistic system:

• Need for rapid and robust communications authority between units

within the battlefield and rear support resources independent of

organization, i.e. direct sensor-to-shooter and joint operations. This is 

a doctrine issue.

• Extremely varied operational environments dictated by physical 

phenomena, coalition partners, multiple foreign regulations, and

international treaties.

• Need for rapid information dissemination and access.

The Generalized Communications Channel Model, described in Chapter 2, is 

a starting point for understanding the synergy between radio communications

and networking services. In that section, this report argues that future radio

systems must be designed for agility within the four feature resource space

because of wide, unknown range of possible missions and the uncertainty of RF 

operating environments. DoD can no longer afford to design and procure radio

systems for specific missions, the possible constraints are simply too complex to 

anticipate.

Given that adaptive communication systems are required, what must be 

accomplished to deploy these systems? First, the communication components

must be designed and implemented in a manner that they can be controlled by 

an authorized external management sub-system. Second, techniques to set the

controls to achieve desired system characteristics and properties must be

designed and implemented. Third, instruments and databases must be

implemented to sense the local environment and adjust the radio system based

on present needs and local rules. Fourth, network protocols must be designed

and implemented to ensure the multiple radios are interoperable.

Examples of adaptations the task force anticipates include:

• Change to a different set of RF frequencies to avoid interference,

penetrate foliage, gain bandwidth for capacity, communicate with a

different information service, avoid detection, et cetera.
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• Change modulation/power/compression to increase/decrease

capacity, avoid or ignore detection

• Change antenna characters to point/track a new information service, 

avoid detection, avoid interference, et cetera.

Coordinating these types of changes in timely manner will require robust

network communications between radios. For example, if two radios are to

change frequency, time, spatial orientation, or coding, both must know the new

RF resources to be used ahead of the change and know the exact time of the

change. Network protocols to communicate these adaptive uses have yet to be

developed.

Many of the technologies necessary to implement the type of adaptive radio

system described above are in development.

Software defined radios (SDR), in particular the Joint Tactical Radio System

(JTRS), fit this description. SDRs define almost all of their characteristics and

capabilities in software modules, which can be quickly switched “on-the-fly” by 

the user. New capabilities can be implemented by developing and deploying

new modules. Modules can easily be selected and controlled by setting

parameters.

However, the JTRS program has until recently focused on implementing

legacy waveforms. The focus on legacy waveforms, while meeting

interoperability needs with existing systems, has not taken full advantage of the 

SDR concept or capabilities. The wideband networking waveform (WNW),

which supports multiple capacities and modulation types, is a first step towards 

a more flexible radio system. 

While SDRs promise extensive flexibility and rapid deployment,

development of SDR capabilities should not be underestimated. The software is

difficult to develop, testing for feature interaction is complex, and adaptive 

systems are difficult to test and evaluate. Also, the impact on antenna design is

significant based on platform type (i.e., soldier, vehicle, UAV, aircraft).

The DARPA XG program concentrates on sensing RF signals and uses local

databases to infer the local RF environment and to exchange information among 

a set of radios. Research programs at the service and industrial laboratories

promise high performance circuits and signal processing capabilities. Adaptive
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mobile network routing protocols are under development. However, the task

force views these as fragmented efforts that need to be pulled together and

coordinated to achieve the presented vision.

A crucial need, and perhaps a show-stopper, is dynamic cryptographic

keying of deployed systems. The ability to authenticate a user to allow them to

join a network, determine user authorizations, avoid network compromise

should a node be lost, and other capabilities are required. Additionally,

considerable policy, cost, power, security, and interoperability issues surround a 

truly user-friendly, mass-deployment cryptographic system for next-generation 

communications. Assured and robust protocols and techniques are perhaps the

least developed technologies required to instantiate adaptive radio

communications systems.

There is a critical need for a large-scale integrated simulation capability that

gives the information system designer the ability to adapt subsystem parameters 

and strategies based on a dynamic information model. Using all of the

aforementioned advances in technology available on an ad hoc basis, the planner 

would get the maximum performance out of a heterogeneous network of SDRs. 

This simulation tool would need to translate directly into operational settings for 

a deployment. It is not likely that commercial industry would lead the charge,

given that most commercial systems will continue to operate with fixed base

stations.

TOR ITEM 5: INTERFERENCE

The TOR states: Wideband RF modulation is a very flexible format that may

permit the DoD to fully exploit its variable code length and bandwidth-on-demand 

characteristics using packet switching techniques to meet the DoD’s long-term 

United States and possessions (US&P) communications requirements. The potential 

limitations of this approach should be addressed including communication systems

that cannot effectively employ direct sequence modulation. The implications of this

approach during a transition time when both legacy systems using traditional

narrow band techniques and systems using these new technologies also should be

addressed. Implications of the employment of Wideband RF modulation for the U.S. 

regulatory regime should be identified and assessed.

The promise of wideband RF modulation is that communications can occur at 

very low power spectral density levels and, hence, the wideband
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communications will not interfere with existing communications systems.

Unfortunately, no such blanket statement can be made. Our concerns are

threefold. First, many existing military systems are designed with very limited 

noise margins. Any additional interference (noise) would degrade system

capabilities. Second, the aggregate effect of multiple low power density emitters 

on an existing system is not well understood. Third, interference effects on low 

power spectral density systems by existing narrow-band systems are not well

understood.

From these observations, one might conclude that significant additional study 

is in order. However, those types of studies are expensive, require significant

amounts of time, require a large-scale testbed, and additional time necessary to 

modify the affected systems. The DARPA NetEx program is taking this approach 

with respect to ultra-wideband systems. While they will compile useful

interference results on some two dozen systems, it is unlikely they will be able to 

state anything about other systems. That is, the results would be static, reflecting 

the examined systems, and not recently deployed systems or new environments.

The radio communications environment is evolving with new services, 

architectures, modulation techniques, among many other technologies. Some

advocate a complete opening of spectrum resources and encourage that all

systems should be (ultra) wideband system. The advocates tend to think that

interference can be handled by “smart receivers” that reject interfering signals. It 

is difficult, in the global market, to determine which might be successful and

which will fail. A particular radio communications deployment might encounter 

new services, a high powered transmitter, or a conjunction of many relatively

low powered, spectrum sharing devices. One has to anticipate that the RF

environment and/or mission is likely to change rapidly and DoD system must

adapt.

In a dynamic system, the following adaptations might take place:

• A receiver senses an interferer and coordinates with its

corresponding transmitter to change to a different portion of the RF

Resource Space. 

• A system senses an interferer affecting the receive function and

executes an adaptive interferer cancellation algorithm. The

cancellation algorithm might be re-pointing an antenna, steering an

antenna null in the direction of the interferer, or use signal processing 

to subtract the interfering signal.
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• A receiver senses an interferer and coordinates with the interferer to 

change to a different portion of the RF Resource Space. 

However, all radio communications comes down to how much signal energy 

is detected at the receiver, how much interference can be rejected through

antennas, filters, and signal processing, and can the desired signal be detected

and de-modulated given those receiver energy levels. The extra processing

comes with the price of computing resources and power. Further, if a nearby

system is transmitting several mega-watts of RF power, signal processing and 

detection will not help when the physical energy detection mechanism is

overloaded. DoD needs to be aware of these emerging ideas and architectures

and articulate DoD’s requirements and concerns with a technically strong

foundation.

TOR ITEM 6: COST AND TECHNICAL RISKS

The TOR states: Implications for the cost and technical risk associated with the 

extensive use of Wideband RF modulation by the DoD should be identified and

assessed.

Both cost and risk become drivers in the quest to fully utilize the available 

bandwidth and provide the connectivity required for the warfighter of the

future.

As DoD communications requirements expand, the task force finds the cost of 

DoD systems can benefit from the advances in the commercial communications

sector. Yet the demands of the DoD can be very specialized (e.g. non-commercial 

radio frequencies and wider operating ranges), resulting in small parts quantities 

and performance requirements beyond those of the commercial sector. In many

cases, this obviates the opportunity to use commercial capabilities and

components. Wherever possible new communications strategies should be

designed such that they can capitalize on the technology investment and

production base of the commercial sector but, where this does not yield results, 

investments will be required to minimize risk, reduce cost, and provide the

required capability. 

The demands made on communications systems by such tasks as intelligence, 

surveillance, and reconnaissance (ISR) illustrate the drivers for cost and risk. ISR 

systems generally consume tremendous bandwidth, increasingly require global
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connectivity, demand immediate global presence, and require mobile

networking. All of this must take place in a congested electromagnetic spectrum 

space, in all environmental conditions, and under battle conditions.

In addition, the sensor to shooter path is becoming more direct, thus

requiring very small units of action to have full access to ISR data. This causes

proliferation of systems, requires smaller, less expensive systems to be available, 

and generates entirely new requirements. In the past, ISR systems were point-topoint, could be elaborate, expensive and power hungry. The new systems must 

be small, mobile, and power conserving while at the same time delivering the

kind of performance provided only by large centralized systems in the past.

In order to realize these systems (and others), the costs and risks need to be 

fully assessed and plans for mitigating the associated problems must be

developed. The task force assessment of the risk items includes the following,

non-exhaustive list.

1) Device Technology – Device technology has advanced a great deal in the

commercial sector and many current DoD systems have benefited tremendously. 

In the areas of digital devices, computing and signal processing in particular, the 

commercial sector is the great enabler of new capability. In some areas where the 

DoD does or will operate however, there is a need for improvement to enable the 

development and deployment of significantly improved systems. The two most 

prominent examples of the need for device technology improvement are solidstate power amplifiers and antennas.

2) Power Amplifiers – For many mobile applications, solid-state power

amplifiers are becoming a cost driver and a performance limiter. Current solidstate power amplifiers are highly inefficient, twenty percent efficiency is

considered to be state-of-the-art performance at Ku-band today. This means that 

the devices consume five times as much power as they radiate, eighty percent of 

the input power must be dissipated as heat, and significant battery energy is

wasted. The resulting communications devices are larger and heavier than is

desirable.

Further, the power amplifiers and RF front ends which exist today do not

lend themselves to the highly flexible frequency plans which this report

envisions. In many cases, the limiting factor on the ability to rapidly re-configure 

a communications system is the ability to readily tune to a new frequency while 

meeting the power output and frequency mask requirements. Software radios, as 
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discussed, have tremendous potential for highly agile, adaptive communications, 

but that capability is moot if the use of the available bandwidth requires a nonrealizable RF front end.

3) Antenna technology – In the frequency bands of interest to the military,

current antenna systems are still often based on parabolic dishes. This means that 

they are relatively large, are quite fragile, and are not agile. Research has been

going on for years in the area of active antenna arrays and some progress has

been made, but these systems are still mostly experimental and are very

expensive. There is some correlation of these efforts with the solid-state power

amplifier research, since many of the schemes require multiple individually

phased power amplifiers. Progress in antenna design and controllable power

amplifiers could open new avenues to sharing and exploiting electromagnetic

spectrum.

4) Networking Protocols – The source of most of the networking routing

protocols, commercial industry, has not adequately addressed messaging

protocols for network entry, authentication and authorization in a way that is

suitable for long range, variable latency, mobile infrastructure, hostile

environments. The existing commercial protocols for wireless networking are

designed for short range Ethernet Local Area Networks, such as IEEE 802.11, or 

cellular telephony based, rather than being IP router based.

For routing protocols once nodes have entered the network, something better 

than an Open Shortest Path First (OSPF) link state announcement needs to be

identified. A method for discovery/definition of link quality that is tied to the

physical connection is needed. Current industry protocols assume a high quality 

physical link and are not designed to quickly identify and react to varying

conditions. Military wireless communications must use routing protocols that

can account for long distances, high latency and intermittent conditions often

found in military/intelligence links.

Existing academic research usually does not concentrate on military style

high bandwidth interconnect between networks and therefore may not yield the 

solutions required for the current and projected DoD problems. Academic

research into MANET routing generally assumes a flat network of peers, or a

simple two-level hierarchy, with a shared communications channel. This is

appropriate for the individual soldier and small unit networks, but does not

match a network-centric concept. The theater-wide military networks required

for sensor to shooter integration and Network Centric Warfare in general are
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more prone to be hierarchal in design with dedicated trunks (wired or wireless) 

between subnetworks and LANs.

In addition, current routing protocols (such as Mobile IP) and hardware

solutions generally assume stationary routers and mobile end users, rather than 

the mobile router infrastructure with variable network exit and re-entry that

characterizes the demanding DoD environment. It is not enough to be able to

adapt to small units moving between local routers, the DoD must also account

for varying connections and conditions between the routers – for which Mobile 

IP has no solution.

5) Software Radios. Software radios can be viewed as both a risk and an

opportunity. The risk lies in the capability to develop and implement

communications protocols, waveforms, etc. that are not supportable by existing

device technologies, spectrum allocations, and protocols. This is a complex task 

requiring detailed planning and diligent software implementation. There is a

danger that overly complex network interactions are required as well. The

opportunity is that, in the event that highly flexible amplifiers and antennas can 

be developed, software radios can take full advantage of this technology.

Research into software radio algorithms is required to ensure that as Digital 

Signal Processing (DSP) devices and Field Programmable Gate-Arrays (FPGAs)

become faster, larger, and cheaper, the optimum waveform techniques are

developed in parallel. New initiatives to place some of the burden for

interference management on the receiver also pose risks to existing radios and it 

is possible that research and development in the area of software radios could

mitigate or avoid some of that risk.

The wideband communications technology has several clear cost elements,

trends, and correlations which may be used to estimate costs. These include:

• Most of the technology required for modern wideband wireless

techniques is predominantly digital and software/firmware; analog

circuitry is a constantly shrinking portion of the equipment and

development cost.

• As a first-order approximation, the total amount of circuitry and

software in a purchased wireless communications device is directly

proportional to the data rate; this approximation takes into account

digital, RF, analog hardware as well as amortized

software/firmware.
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• Non-recurring development costs of embedded communications

software/firmware will comprise the lion’s share of the DoD

communications’ purchase dollar; as such, the key enabler or

deterrent for industry’s development of such software/firmware are

the accounting rules by which they may recover their non-recurring 

investment.

• Digital technology continues to increase in capacity and decrease in

cost, following the classical Moore’s Law time/cost curve.

• Analog circuitry is a very small portion of the total equipment cost,

and is mostly implemented in integrated circuits whose cost is

quantity-driven, typically requiring production in the millions of 

units and suggesting that DoD needs can only be met affordably by

leveraging commercial technology or budgeting for the steep front

end cost of integrated circuits.

• Higher information capacity needs drive users to higher frequencies

that can support the bandwidth/data rate. This in turn drives

semiconductor process and device technology needs, requiring a

constant stream of new materials and finer geometry processes to

support the higher frequencies. The result is that there never appears 

to be an “equilibrium” where a new semiconductor technology for a 

particular band is allowed to stabilize and mature for years (like

silicon and digital circuits); rather, a constant semiconductor

investment stream is required and should be planned for.

• The contention for spectrum in higher bands is heavily driven in the 

commercial sector by the cost of licensing spectrum. Obtaining

“pioneer” licenses in “unexplored” portions of the spectrum is

inexpensive though risky. In the face of this and the search for higher 

frequencies for greater capacity, DoD once again is outside the

process.

• The extension of this cost basis is rapidly transitioning to the free

space optical domain, where very high speed “wireless” [fiberless]

optical communications can convey gigabits of data. As yet, this is

“pioneering” technology and services, and has no FCC licensing

(although they are considering the ramifications but are already

behind the power curve). DoD would be well-advised to “stake a

claim” in this vital future medium before the ad hoc market rules

dominate the medium, causing the potential for significant future

costs.
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In summary, the costs and risks of moving to a more comprehensive solution 

to the efficient use of wideband RF systems can best be managed by taking

advantage of the relevant developments in the commercial sector, by recognizing 

the areas where commercial efforts are not applicable, acknowledging important 

trends in communications systems implementations, and supporting the

appropriate research and development required for DoD unique problems.

SUMMARY OF FINDINGS

The cost and complexity of designing and building new network-centric 

communications systems is significant. Flexible dynamic communications

systems that use the entire RF Resource Space are integral to the success of

network-centric systems-of-systems. Current investment in new smart

communication systems is essential and shows the huge potential improvement

in capability and capacity. 

However, radio communications systems need to operate in a morass of

detailed domestic, international, and doctrinal rules and regulations and

pressures from the commercial sectors for new spectrum resources. Future

wideband communications systems need to account for and adapt to current,

emerging, and future regulations and laws.

The spiral development philosophy allows gradual insertion of these new

technologies as they are designed and tested, providing increased performance

over time. Diligent attention to how a component fits into the larger system, not 

just to the component itself, will assure that the end result is a fully integrated

and compatible systems-of-systems. The days of independently pursuing a

technology and developing a component without considering its role in the

encompassing system are gone.
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RECOMMENDATIONS_____________________________________________________ 61

CHAPTER 5: RECOMMENDATIONS 

Networks, by their very nature, derive their value from the interconnectedness and rapid exchange of information. General Richard Myers, 

Chairman, Joint Chiefs of Staff, captured the importance of combining

talents of many different military units when speaking to Pentagon workers 

in November 2002.

“In my travel to see the war fighters around the world, no

single unit ever seems to be able to do the job all by itself

and do –it – and do it alone. The best tactical solutions are

often found when we combine the talents of many different

units and many different services. Those operations, the

successful ones, are often characterized by a climate of trust 

and confidence between the senior leadership. We need to

learn from them, and we need to continue to improve our

joint war fighting. Whether you're a soldier, a sailor,

airman, Marine, Coast Guardsman, or DOD civilian, this

war on terrorism will require great innovation and sacrifice

on all our parts over the next several years.”

– General Richard B. Myers, Chairman, Joint Chiefs of Staff, 

November 12, 2002, Pentagon Town Hall Meeting

In a similar vein, network-centric warfare demands the combined

capabilities of a range of technologies: antennas, RF circuits, signal

processing, resource management, network routing, and network services.

Putting a collection of world-class technologies together without taking into 

account how they interact and even forcing them to interact without due

consideration is doomed to failure. 

Following are the recommendations of this task force. Several of the

recommendations include specific technical or programmatic

implementation objectives.
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AGILE WIDEBAND COMMUNICATIONS SYSTEM INITIATIVE

RECOMMENDATION #1: THE OFFICE OF SECRETARY OF DEFENSE MUST 

INITIATE A COMPREHENSIVE PROGRAM IN AGILE WIDEBAND 

COMMUNICATIONS SYSTEMS.

Agile wideband communications systems are capable of addressing all

of the Department of Defense radio frequency communication needs. They 

offer high data rate transmission, ability to meet all possible military 

requirements, such as covert communications and robust communications, 

and provide the capability to adapt to the local/regional communications

environment. The DoD Science and Technology community has recognized 

the need for basic science and project development in wideband

technologies. The service laboratories also recognize this need. However,

the DoD lacks a comprehensive program to guide, implement, and deploy

the crucial wideband technologies. 

A comprehensive program should coordinate research and

development programs across DoD research organizations; invest in

extensive experiments, evaluation, and integration in a ongoing testbed;

organize a network centric architecture office to define and continuously

update a roadmap for investment, integration, and deployment; and use

the advanced technology and experience to lead and formulate future

spectrum policy at the national and international forums. 

RF COMMUNICATIONS SYSTEMS RESEARCH AND DEVELOPMENT

RECOMMENDATION #2: ASDNII AND USDATL SHOULD INCREASE AND 

FOCUS INVESTMENT IN FLEXIBLE AND ADAPTIVE AGILE WIDEBAND 

COMMUNICATIONS TECHNOLOGIES TO ACHIEVE NECESSARY MISSION 

CAPABILITIES IN A HIGHLY DYNAMIC RADIO FREQUENCY 

COMMUNICATIONS ENVIRONMENT.

It is clear from this study that every aspect, every technology in an RF 

radio communications system should be programmable and controllable.

That is to say, the wireless communications function should – and will in
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RECOMMENDATIONS_____________________________________________________ 63

the future – simply be an embedded component of a user subsystem and

the radio as a standalone procurable item will cease to exist. More

important than control within a component, e.g. a smart antenna or tunable 

receiver, is that the component be controllable from another system

component. For example, smart antenna designers must expect their

antenna will be controlled from a network resource manager and network

traffic routing will be controlled from network services sources and sinks.

This implies the flexible capability must be built-in and the interface well

defined and available to other parts of the system. A significant part of the 

investment should be in the required flexibility and the interfaces (the

protocols) between components. Every program manager, every principle

investigator should be challenged to answer how their investment fits in

the larger RF communications systems picture. Specifically,

• Director, Defense Research and Engineering (DDR&E) should

continue research and development in breakthrough RF device 

and circuits, antenna, signal processing, software radios, and

networking technologies at the science and technology

organizations, the service laboratories, and engineering research 

and development centers.

• DDR&E and NII should make a significant investment in

network management and access technologies for mobile, ad

hoc, military tactical networks. Of particular importance is

investment in research and development of flexible and

adaptive RF communications systems, RF link protection such

as low probability of detection/intercept (LPI/LPD),

mechanisms for robust and secure mobile infrastructure, interconnected and inter-operating communications systems, and

the necessary control mechanisms and protocols. 

• DDR&E should increase investment research and development

in dynamic, efficient, ad hoc, adaptive spectrum utilization

procedures and services and automatic spectrum management

necessary for anytime/anywhere missions.

Specific technical objectives should include: 
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• Show the feasibility of at least one instantaneously wideband

waveform capable of simultaneous operation in non-contiguous 

bands;

• Perform experiments proving that communications using timevariable spectrum occupancy at a level more sophisticated that 

frequency hopping technology is feasible;

• Demonstrate wideband codes assigned to a “large” set of users 

within a subnet, with subsequent modification of the

assignment due to introduction of new users and/or change in

demand by one or more nodes, control may be centralized or

distributed, as dictated by other aspects of the architecture;

• Show at least one architecture and a related set of protocols that 

permit network operations to be conducted by DSSS signaling

in an orderly fashion and allow users the desired connectivity

and data rates;

• Show that adequate time and frequency control can be

maintained within subnets, and perhaps at higher tiers as well. 

This involves algorithms for arrival time measurement at the

various nodes and determination of subsequent transmission

times. The goal should be to achieve isolation 10-20 dB better

than would be expected in an uncoordinated environment;

• Perform experiments in which operation is conducted within

otherwise occupied bands to ascertain that the ambient

interference does not compromise the performance of the test

system, nor the test system adversely interfere with systems in 

the “host” band;

• Develop a conflict monitoring capability to determine how well 

the spectrum access methodology performs and to generate

corrective data for subsequent refinement of the spectrum 

access strategy and network architecture details; and

• Develop a data reduction capability in which the characteristics 

of the test radio platform(s) are extrapolated to estimate what

would be required in a complete system and to determine

whether a technology development program for any radio

components is needed and what its content might be.
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RECOMMENDATIONS_____________________________________________________ 65

Only through investment in flexible and adaptive RF communications

will DoD be able to meet the variety of its missions in the locations

necessary.

RF COMMUNICATIONS SYSTEMS TESTBED

RECOMMENDATION #3: ASDNII MUST ESTABLISH AN AGILE WIDEBAND 

COMMUNICATIONS SYSTEMS TESTBED.

Inherent in building systems is the need to experiment, test, integrate

and evaluate the interactions of the numerous components in real-life 

situations, in the physical environment, and on a continuous basis. A largescale testbed is needed to assess, evaluate, and transition technologies and 

capabilities from research and development into production and

deployment. Such a testbed would provide feedback to the research

community and identify as soon as possible problems in anticipated

solutions. The testbed could be used to try new algorithms, for example

new waveforms on a JTRS radio network or new routing algorithms for

network services, without significant additional investment by individual

projects in hardware and logistics.

Further, the testbed would be used to measure and evaluation

interference between existing defense, government, and commercial

systems and emerging wideband systems. Solid measurement data is

necessary to understand system interactions and to provide a basis for

policy recommendations when working with regulatory agencies and the

commercial and international sectors.

The testbed should be built in cooperation with the commercial sector to 

explore new RF communications technologies and determine interference,

compatibility, and performance characteristics of new radios. The testbed

should be used to evaluate the effectiveness of spectrum management tools 

and techniques.

Testbed objectives include:
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• Performance of new equipment, algorithms and software

should be verified in simulation and laboratory test bed settings 

prior to field trials. A laboratory testbed should be funded by

DDR&E to develop the facilities, equipment, software suites and 

personnel needed to carry out the responsibilities of functional 

testing of equipment and software as an integral part of an

overall program to develop the integrated network capabilities.

• Research a next generation JTRS waveforms to address current 

limitations. Potential enhancements include integration of

Space-Time processing (MIMO), improved mobile networking

protocols, integration of XG-like adaptive spectrum access,

reduction in overhead associated with current networking

protocols, additional modulation options (in addition to the 4

current ones), and development of networking protocols and

modulations suitable for use at higher frequencies (current

upper limit is 2 GHz).

• The potential application of CDMA technology (orthogonal

codes) and precision timing to radar systems to decrease

spectrum use and increase frequency reuse should be studied

and demonstrated through DDR&E sponsored research

programs.

• Conduct research into the application of adaptive spectrum

access protocols to the problem of mitigating the near-far 

problem in CDMA systems.

• Electromagnetic compatibility (EMC) analysis of wideband

waveforms versus legacy equipment and a review of DoD

spectrum use to migrate or replace spectrum-inefficient 

equipment. There should also be an analysis/modeling of

dynamic spectrum access techniques (e.g., DARPA XG

Program) for EMC affects on RF equipment environments.

• A modeling and simulation test bed should be developed to

evaluate wideband, networked, adaptive communications

systems and the effects to and from RF equipment

environments. The Joint Spectrum Center (JSC) should be an

active participant in each of these activities.
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RECOMMENDATIONS_____________________________________________________ 67

IDENTIFY AN OFFICE FOR NETWORK-CENTRIC COMMUNICATIONS 

ARCHITECTURE

RECOMMENDATION #4: ASDNII SHOULD IDENTIFY AN OFFICE FOR 

NETWORK CENTRIC COMMUNICATIONS AND DEVELOP A ROADMAP 

FOR TECHNOLOGY INVESTMENT, EVALUATION, AND TRANSITION INTO 

OPERATIONAL SYSTEMS. THE ROADMAP SHOULD INDICATE PHASE-IN 

AND PHASE-OUT OF TECHNOLOGIES AND ARCHITECTURES.

ASDNII must identify an office for network-centric architecture. This

office would articulate how one goes about building a network-centric 

communications system. The various Joint Vision documents call for

”network-centric warfare,” ”information superiority,” and other

capabilities built upon communications. However, these documents do not 

elicit how such a system might be built, nor the components necessary to

build such a system. This leaves the door open to many claiming they are 

working toward a network-centric system without have to explain exactly 

how their work fits into the system.

To aid ASDNII decision process, the Network-Centric Architecture

Office (NCAO) should develop an RF communications/network

management technology roadmap. The roadmap should serve two

purposes: a strategic plan and a tactical plan. The strategic plan should be

driven by the requirements and needs of the services. It should show the

components actually needed to build a network-centric communications

system, including digital and analog hardware as well as

software/firmware, the time those components are likely to be available,

and identify technology challenges to be solved to achieve the desired

result. The tactical plan should show the prototyping and development

steps needed to move wideband technology from the laboratory to

deployment and use. The roadmap should be updated on a semi-annual or 

annual basis as technology and systems evolve. DoD, federal government, 

industry, and academic participation in developing and maintaining the

roadmap is essential. 

Without such a roadmap, every technology that might fit into a

network-centric RF radio frequency communications system becomes a
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68 ____________________________________________________ RECOMMENDATIONS

candidate for investment. Without clear articulation of how the technology 

contributes to the network-centric system, funding is likely to be

misdirected. The roadmap should not be a gatekeeper to early research

investment in innovative technologies, doing so would limit the very

innovation that is relied upon. 

Specific Recommendations of the task force are: 

• ASDNII should identify Network Centric Architecture Office

(NCAO) chartered with integrating diverse DoD efforts to

provide technical alternatives to the current form of radio

communications and network management. The goal is to

develop an insertion path for new technologies that can be

explained to Congress and to the American people as a

cornerstone of DoD's leadership of the public trust in this area.

The NCAO should be consolidated from ongoing NII, JTRS JPO 

and DDR&E wireless networking technology efforts and be

placed under central management. The NCAO would be

responsible for coordinating research, development,

experimentations, and evaluation related recommendations of

this report.

• The NCAO office should develop a roadmap for technology 

investment, evaluation, and transition into operational

systems. The roadmap should indicate phase-in and phaseout of technologies and architectures and be sufficiently

specific to permit the development of implementation and

transition plans by all unified Commands, Services, and DoD 

agencies. The roadmap should indicate when to reallocate or 

're-mine' spectrum as obsolete military inventory is removed 

from service.

• The NCAO should develop executable plans for wideband

technology pilot programs. Where possible, these technology 

pilot proposals should demonstrate Joint service application. 

Plans should include service sponsorship commitments to

enable submission as ACTDs, ATDs, or insertion into Joint

Experimentation.
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RECOMMENDATIONS_____________________________________________________ 69

• The NCAO should draft a report recommending an

executable detailed study to establish a cohesive, wellfocused science and technology program to enable

capabilities in wireless networking technologies. The

detailed study will quantify capability improvements

possible in each of the following areas: communications, 

surveillance, targeting and weapons delivery. The study

would include detailed numerical analyses and conclusions

regarding the effect of improved spectrum.

• ASDNII should establish a senior technical advisory board

comprised of industry and government scientists for innovative 

use of network and spectrum technologies. The advisory group 

should consist of recognized industry experts in internetworking technologies, commercial information and network 

security technologies, emerging information transfer

technologies and systems, and other commercial activities such

as standards development, infrastructure development, and the 

like. The advisory board would monitor the network-centric 

roadmap, suggest modifications, and alert DoD to emerging

technologies and policies. The advisory board could be set up

under the auspices of the National Research Council similar to

the Board on Army Science and Technology.

• ASDNII with the NCAO should work with the service

representatives responsible for requirements generation to

identify anticipated shortfalls in achieving JV2020 capabilities

that could be addressed by wideband systems. For those

potential wideband applications, a high level CONOPS will be

prepared to help identify specific wideband system capabilities 

to be addressed through DDR&E sponsored research.

• Proposals in this report represent a fundamentally different

approach to using the RF resource space. NII, Joint Staff, and

service representatives should identify compatibility and

interoperability issues associated with a migration to wideband 

systems and develop a DoD-wide transition plan.

The Network-Centric Architecture Office would in many respects

carryout the systems engineering work for a network-centric 
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70 ____________________________________________________ RECOMMENDATIONS

communications system. It would insure the wide range of mission

requirements and capabilities are met, that components work together

through the testbed, and anticipate future needs and requirements.

POLICY

RECOMMENDATION # 5: ASDNII MUST TAKE THE LEAD IN 

DEMONSTRATING STEWARDSHIP OF ALLOCATED SPECTRUM AND THE 

ADVANTAGES OF AGILE WIDEBAND RF COMMUNICATIONS TO DEVELOP 

AND PUT FORTH SPECTRUM POLICIES BASED ON EXPERIENCE.

A common view is that the Department of Defense controls a significant 

portion of the radio frequency spectrum, but a recent General Accounting 

Office report [GAO2002] showed that the federal government has exclusive 

access to only 13.7% of the spectrum between 9 kHz and 3.1 GHz compared 

to 30.6% exclusive access to that same spectrum by the non-federal 

community. Given the demand for new commercial wireless services, the

mission requirements of the DoD and the current lack of a national

spectrum policy, the DoD will need to work within its current allocations in 

the foreseeable future.

Any review of spectrum policy should be aimed at promoting efficient

use of the spectrum in a way that best meets the demands of federal and

non-federal users. As both DoD and the private sector employ advanced

communications systems capable of transmitting greater amounts of data, 

the spectrum requirements of both are increasing. Certain systems, such as 

wide area mobile operations must be accommodated in bands below

roughly 4-5 GHz to achieve reasonable coverage. Policies should focus on

means of making this prime spectrum available for services that require it, 

such as wide-area mobile. The process should examine ways to maximize

the efficiency use by grouping like services together in order to minimize

interference, and it should provide a well-defined technical structure.

Services such as fixed services or services that serve small areas should be 

accommodated in higher bands that are not technically suitable for wide

area mobile services.
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RECOMMENDATIONS_____________________________________________________ 71

In general, it will not be possible for military and commercial systems to 

be deployed in the same area using the same frequencies without causing

harmful interference. However, ASDNII could explore ways for systems to 

be deployed on a coordinated basis to the mutual benefit of all users. To a 

large extent, commercial and military use occurs in different geographic

areas. Accordingly, it should be possible to divide use of spectrum on a

geographic basis for similar systems. Agreements could be reached

between commercial licensees and DoD to have some shared spectrum and 

for DoD to have priority use of the otherwise commercial part of the shared 

spectrum during a national emergency. There is precedence for agreements 

that would provide for DoD control of the commercial infrastructure if

necessary.

Consistent with the need to group like services, a focused U.S. spectrum 

management effort to provide additional spectrum for wideband, wide area 

services could put the United States in a leadership position to set the

direction for global harmonization of spectrum. Harmonization would

benefit both the military and the commercial sectors by providing global

markets and consistency in spectrum availability for the military. Greater

global harmonization would help drive down the cost of equipment and

services.

DoD investment in wideband technologies could significantly enhance

commercial usage of the technology. It is possible that agreements could be 

reached that would result in increased and more efficient sharing between 

military and commercial services. To the extent that the military and/or

homeland security is authorized to have priority over other uses during an 

emergency, a commercial infrastructure based on wideband technology

would be beneficial.

ASDNII must take a number of steps to demonstrate leadership in

spectrum management. These steps include:

• Pursue an active agile wideband program to have the tools for 

future spectrum management;

• Reduce/eliminate the assignment of narrowband frequency

channels in selected bands and utilize agile wideband
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72 ____________________________________________________ RECOMMENDATIONS

technologies and dynamic RF resource management to increase 

utilization and capacity within the selected bands;

• Used agile wideband systems to demonstrate improved

spectrum utilization and dynamic spectrum management

within DoD allocations in experimental, test, and evaluation

programs;

• Take the lead in developing standards, through established 

forums (e.g. ITU, FCC, NTIA, standards bodies), for dynamic

spectrum management and increased RF resource management; 

and

• Use experience in agile wideband radio systems to develop a

strategy for balancing national security and economic needs for 

spectrum and recommendations for spectrum management

policies and techniques. The strategy and recommendations

should address domestic, international, and coalition (e.g.

NATO) issues. Recommendations should be presented to the

appropriate leadership and national and international

organizations.
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CONCLUSIONS ______________________________________________________________ 73

CHAPTER 6: CONCLUSIONS

Radio communications is currently one of the most exciting technologies in

research and development. Breakthrough technologies in devices, circuits,

antennas, signal processing, and mobile networking offer immense capabilities

for communications. But as these individual technologies advance, the synergy

of linking these wide ranging technologies is also being experienced. Smart

antennas linked to agile radios controlled through a decentralized network 

manager offer increased mission critical capabilities and resource utilization.

This is a shift in focus from limited, single use communications systems to

network-centric, system-organized capabilities.

The innovation present in radio communications research indicates no single 

technology will satisfy all missions. Ultra-wideband systems promise useful

sharing and sensing capabilities, but also are limit in distance and are likely to

cause interference with crucial existing services. CDMA offers significant robust 

capabilities in point-to-point and fixed infrastructure applications, but in a peerto-peer networking application, the same capabilities may be difficult to achieve. 

Further, the need for contiguous spectrum in direct-sequence CDMA may make 

it difficult to operate in some jurisdictions. A significant investment in directsequence CDMA is risky at this time given the lack of experience in peer-to-peer 

radio networks and worldwide spectrum allocation problems.

Agility, robustness, networking and adaptation, along with traditional

properties of anti-jam, low probability of intercept, capacity, foliage penetration

among others, will be crucial properties for the military in the future. These

emerging properties require more than just linking multiple systems together

with a single protocol, e.g. the Internet Protocol, but require the development

and evaluation of system-wide management and control mechanisms. Given the 

complexity of these multiple communications systems, it is absolutely necessary 

to evolve these systems over time through extensive experimentation and

evaluations. Analysis, simulation, and emulation, while important, are not

sufficient to develop reliable communications systems.

It is through demonstration and action that the Department of Defense can

take the lead in offering new radio communications technologies and new

strategies and policies to the larger national and international communities.
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CONCLUSIONS ___________________________________________________ RF MODULATION

74 ______________________________________________________________CONCLUSIONS

Demonstration of agile radios, dynamic spectrum management, and high RF

resource utilization can be the driving force behind increased capacity for both

DoD and the commercial sector and provide the basis for introduction of new

wireless services.
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RF MODULATION______________________________________________________ REFERENCES

REFERENCES ________________________________________________________________ 75

REFERENCES

[JCS2000] Joint Chiefs of Staff, “Joint Vision 2020,” Office of Strategic Plans and 

Policy, Washington, D.C., June 2000.

[QDR2001] Office of the Secretary of Defense, “2001 Quadrennial Defense Review,” 

Department of Defense, Washington, D.C., September 2001.

[DSB2000] Defense Science Board, “DoD Frequency Spectrum Issues – Coping with 

Change: Managing RF Spectrum to Meet DoD Needs,” December 2000.

[DSB2000-6] Report of the Defense Science Board on the Technology Capabilities of 

Non-DoD Providers, June 2000, Washington, DC.

[DOD2002] Office of the Assistant Secretary of Defense, “Electromagnetic Spectrum 

Management Strategic Plan,” October 2002.

[FCC1981] Frequency, Efficient Use of Modulation, Federal Communications 

Commission Report FCC 81-289, 1981, Washington, DC

[FCC2002] Federal Communications Commission, “Spectrum Policy Task Force,” ET 

Docket No. 02-135, November 2002.

[FCC2002-11] Report of the Spectrum Efficiency Working Group, Federal 

Communications Commission Spectrum Policy Task Force, November 15, 2002.

[Cave2002] M. Cave, “Review of Radio Spectrum Management,” Department of Trade 

and Industry, Her Majesty’s Treasury, March 2002.

[GAO2001] General Accounting Office, “Defense Spectrum Management: More 

Analysis Needed to Support Spectrum Use Decisions for the 1755-1850 MHz Band,” 

Report GAO-01-795, August 2001.

[GAO2002] General Accounting Office, “Telecommunications: Better Coordination and 

Enhanced Accountability Needed to Improve Spectrum Management,” Report GAO02-906, September 2002.

[GAO2003] General Accounting Office, “Comprehensive Review of U.S. Spectrum 

management with Broad Stakeholder Involvement Is Needed,” Report GAO-03-277, 

January 2003.
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REFERENCES______________________________________________________ RF MODULATION

76 ________________________________________________________________ REFERENCES

 [Gross2002] David A. Gross, Radio Frequency Spectrum, Testimony Before the House 

Government Reform Committee, Subcommittee on National Security, Veterans 

Affairs, and International Relations, Washington, DC, April 23, 2002.
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RF MODULATION______________________________________________________APPENDIX A

TERMS OF REFERENCE _________________________________________________________ 77

APPENDIX A. TERMS OF REFERENCE
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APPENDIX A _____________________________________________________ RF MODULATION

78 _________________________________________________________ TERMS OF REFERENCE



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APPENDIX A _____________________________________________________ RF MODULATION

80 _________________________________________________________ TERMS OF REFERENCE
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RF MODULATION______________________________________________________ APPENDIX B

TASK FORCE MEMBERSHIP ______________________________________________________ 81

APPENDIX B. TASK FORCE MEMBERSHIP

Chairman

Dr. Gary Minden University of Kansas

Task Force Members

Dr. William Ballhaus The Aerospace Corporation

Mr. Kent Erickson L3

Mr. Klein Gilhousen Qualcomm

Dr. Jim Isaacs ITT

Ms. Diana Johnson The Aerospace Corporation

Ambassador Travis Marshall Private Consultant

Dr. Joseph Mitola III MITRE

Mr. Walt Morrow MIT Lincoln Lab

Mr. Rocky Roccanova TRW

Dr. Robert Scholtz University of Southern California

Dr. K. Sam Shanmugan University of Kansas

Mr. Robert Sternowski Rockwell Collins, Inc.

Executive Secretary

Mr. Mark Norton OASDNII

DSB Representative

LtCol Roger Basl, USAF DSB Secretariat

Government Advisors

Mr. Joe Capps Army CIO/G-6

Mr. Scott Hoschar CNO/OPNAV

Mr. Joesph Inserra CECOM

Dr. John Knab DISA

Dr. Alan Lindsey AFRL/IFGC
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APPENDIX B______________________________________________________ RF MODULATION

82 _____________________________________________________ TASK FORCE MEMBERSHIP

COL Danny Price OASDNII

Mr. David Townsend NRL

Mr. Owen Wormser OASDNII

Staff

Ms. Stacie Smith Strategic Analysis, Inc.
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RF MODULATION_____________________________________________________ APPENDIX C

LIST OF BRIEFINGS_____________________________________________________________ 83

APPENDIX C. LIST OF BRIEFINGS

June 3-4, 2002

Mr. Owen Wormser and Dr. 

Boudri Younes

ASDNII Topics

Dr. John Gowens and Dr. Brian 

Sadler

ARL R&D

Dr. Pete Camana ViaSAT

Ms. Ginger Lew and Dr. Kalle 

Konstan

ASB Wireless Study

Dr. Dan Scheresko Space Communications Architecture

COL Steve McLaird and COL Mike 

Cox

JTRS 

Dr. Bob Fontana UWB Topics

June 24-25, 2002

Dr. Tom Meyer DARPA ATO Programs

Dr. Steve Huffman MITRE Briefing

Mr. John Stenbit ASDNII Directives

Mr. Joseph Inserra Wideband Radio Systems 

Technology for Army Applications

Mr. Bob Sternowski Rockwell Collins UWB

Dr. Klein Gilhausen CDMA Technologies

Dr. Donald Kelly UWB and Time Domain Presentation

Maj Dave McMorries USMC Requirements

Dr. Bobby Junker and Mr. Dennis 

McGregor

ONR Issues

July 25-26, 2002

Mr. James Sterbenz MANET

Dr. Gerald Maguire Telecom Issues

Mr. Byron Barker and Mr. Richard 

Larson

Defense Spectrum Office

Dr. Alan Lindsey and Dr. Mark 

Linderman

AFRL Issues

Mr. Paul Perkowski MILSATCOM Requirements

Col Brian Robinson Transformational Communications 

System
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APPENDIX C _____________________________________________________ RF MODULATION

84 ___________________________________________________________ LIST OF BRIEFINGS

August 28-29, 2002

Mr. John Wehling TRW Topics

Mr. Alex Pidwerbetsky BLAST and Lucent Technologies

Mr. Ken Pramik NSA Security Issues

Mr. Jim Marshall Wideband Analytical Foundations 

and Demo Recommendations

Mr. Charles Niessen Spectrum and CDMA Issues

Mr. Kent Erickson Wideband CDMA and L-3

Dr. Rich Orr CDMA Network Architecture 

Implications

Mr. Rob Calderbank, Mr. Suhas 

Diggavi, and Mr. Naofal Al-Dahir

AT&T Presentation

Dr. Randy Young Scale Time Offset Modulation

September 26-27, 2002

Dr. Paul Kolodzy FCC Spectrum Issues

Mr. Scott Harris, Mr. Peter Pitsch 

and Mr. Jeff Campbell

Spectrum Policy Issues – An Industry 

Perspective

Dr. Greg Gibbons Covert Localization and Tracking

October 21-22, 2002

Mr. Mike Mearns Overview of Navy Developmental 

Wideband Radars

Mr. Tom D’Amico Motorola Presentation

Mr. Don Latham DSB 2002 Summer Study Briefing

Dr. Wolfgang Kober CDMA Co-Channel Interference 

Mitigation

November 21-22, 2002

Mr. Paul Roosa NTIA

Mr. Mike Francl CDL Briefing

Ambassador David Gross Department of State Presentation

Mr. Joseph Inserra Army Action Item
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RF MODULATION______________________________________________________APPENDIX D

GLOSSARY__________________________________________________________________ 85

APPENDIX D. GLOSSARY

AJ Anti-Jamming

AFRL Air Force Research Laboratory

AM Amplitude Modulation

ARL Army Research Laboratory

ASB Army Science Board

ASDNII Assistant Secretary of Defense for Network Information and Integration

ATO Advanced Technology Office (DARPA)

BER Bit Error Rate

BLAST Bell Labs Layered Space-Time System

C3I Command, Control, Communication & Intelligence

CDMA Code Division Multiple Access

CIP Communication and Information Policy

CONUS Continental United States

CSMA Carrier-Sense Multiple Access

DARPA Defense Advanced Research Projects Agency

DASD Deputy Assistant Secretary of Defense

DC Direct Current

DISA Defense Information Systems Agency

DoD Department of Defense
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APPENDIX C _____________________________________________________ RF MODULATION

86 __________________________________________________________________ GLOSSARY

DSB Defense Science Board

DSO Defense Spectrum Office

DSP Digital Signal Processing

DSSS Direct Sequence Spread Spectrum

Eb/No Bit Energy to Noise Ratio

EHF Extremely High Frequency

EIRP Equivalent Isotropic Radiated Power

ERP Effective Radiated Power

E3 Electromagnetic Environmental Effects

FCC Federal Communication Commission

FDMA Frequency-Division Multiple Access

FHSS Frequency Hopping Spread System

FM Frequency Modulation

FPGA Field Programmable Gate-Array

FSL Free Space Loss

GAO General Accounting Office

GHz Gigahertz

GPS Global Positioning System

HDR High Dose Rate

HF High Frequency

IEEE Institute of Electrical & Electronics Engineers

IP Internet Protocol
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RF MODULATION______________________________________________________APPENDIX D

GLOSSARY__________________________________________________________________ 87

IRAC Interagency Radio Advisory Committee

ISM Industrial, Scientific, Medical Band

ISR Intelligence, Surveillance, and Reconnaissance

ITU International Telecommunication Union

JTRS Joint Tactical Radio System

kHz Kilohertz

LAN Local Area Network

LOS Line of Sight

LPD Low Probability of Detection

LPI Low Probability of Intercept

MANET Mobile Ad-Hoc Networking

MHz Megahertz

MIMO Multiple Input/Multiple Output

NATO North Atlantic Treaty Organization

NETEX NETworking in Extreme (DARPA Program)

NLOS Non line of sight

NTIA National Telecommunications and Information Administration

OCDMA Orthogonal Code Division Multiple Access

OFDM Orthogonal Frequency Division Multiplexing

ONR Office of Naval Research

OSD Office of the Secretary of Defense

OSPF Open Shortest Path First
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APPENDIX C _____________________________________________________ RF MODULATION

88 __________________________________________________________________ GLOSSARY

PN Pseudonoise

QAM Quadrature Amplitude Modulation

QDR Quadrennial Defense Review

QDMA Quadrature-Division Multiple Access

RF Radio Frequency

RTP Real-Time Protocol

SDMA Space-Division Multiple Access

SDR Software Defined Ratios

SIR Signal to in-band interference

SPTF Spectrum Policy Task Force

SS Spread Spectrum

STEP Space Time Processing Program

TCP Transmission Control Protocol

TDMA Time Division/Demand Multiple Access

THSS Time Hopping Spread Spectrum

TOR Terms of Reference

Tx/Rx Transmitter/Receiver

UAV Unmanned Aerial Vehicle

UDP User Diagram Protocol

UFZ Ultra-Wideband Friendly Zone

UHF Ultra High Frequency

US&P United States & Possessions
DSB TASK FORCE ON WIDEBAND 

RF MODULATION______________________________________________________APPENDIX D

GLOSSARY__________________________________________________________________ 89

UWB Ultra-Wideband

VHF Very High Frequency

W-CDMA Wideband-Code Division Multiple Access

WRC World Radio-Communication Conference

XG next Generation (DARPA Program)