Air University

Stephen R. Lorenz, Lt Gen, Commander

Air War College

Stephen J. Miller, Maj Gen, Commandant

Kurt Schake, Col, PhD, Dean

Lawrence E. Grinter, PhD, Series Editor

Roy Houchin, PhD, Essay Advisor

Air University Press

Terry L. Hawkins, Interim Director

Bessie E. Varner, Deputy Director

Marvin Bassett, PhD, Content Editor

Darlene H. Barnes, Copy Editor

Vivian D. O’Neal, Prepress Production

Daniel Armstrong, Cover Design

Demorah Hayes, Quality Review

Please send inquiries or comments to

Editor

The Maxwell Papers

Air War College

325 Chennault Circle, Bldg. 1401

Maxwell AFB AL 36112-6006

Tel: (334) 953-7074

Fax: (334) 953-1988

http://www.au.af.mil/au/awc/awcgate/awc-mxwl.htm
AIR UNIVERSITY

AIR WAR COLLEGE

Spectrum Management

Key to the Future of Unmanned

Aircraft Systems?

Mary E. Griswold

Lieutenant Colonel, USAF

Air War College

Maxwell Paper No. 44

Air University Press

Maxwell Air Force Base, Alabama

May 2008
ii

Disclaimer

Opinions, conclusions, and recommendations expressed or implied within are 

solely those of the author and do not necessarily represent the views of Air University, the United States Air Force, the Department of Defense, or any other US 

government agency. Cleared for public release: distribution unlimited.

This Maxwell Paper and others in the series are available electronically at the Air University Research Web 

site http://research.maxwell.af.mil and the AU Press 

Web site http://aupress.maxwell.af.mil.
iii

Foreword

Today’s military operations depend on a very large number of systems to acquire and process critical information 

needed by combatant commanders to accomplish their mission. Intelligence, surveillance, and reconnaissance systems 

often provide a much-needed picture that is vital to decision 

makers. Requests from commanders for information provided by unmanned aircraft systems (UAS) are growing so 

fast that they are outpacing system availability. The future 

of these aircraft is of such importance to military operations that in September 2007, Deputy Secretary of Defense 

Gordon England directed the establishment of a task force 

to coordinate UAS issues and determine a way ahead in order to resolve differences between the military services and 

their approaches to these systems.

While the services continue to debate the advantages of 

one UAS over another or attempt to determine which service 

would best be able to manage its future, current operations 

are affected by the challenges caused by inadequate frequency 

spectrum and bandwidth availability. The most recent Department of Defense UAS road map (August 2005) lists problem areas highlighted by combat operations, including the 

lack of communications frequencies. Furthermore, a Defense 

Science Board report identifies constraints on communication bandwidth as an area needing more attention and new 

development. As UAS capabilities become even more sought 

after and as the number of these aircraft increases, something must be done to help ensure that the much-needed 

capabilities they provide are available to war fighters.

One of the most critical major UAS subsystems, communications, allows information to be passed between the 

aircraft and its ground elements or to other airborne assets; it also enables a UAS to be guided and controlled from 

virtually anywhere at any time. Bandwidth is needed to 

support the systems providing data to control the vehicle 

in flight, including its launch and recovery, and to send 

data from the onboard sensors or payload to processing 

centers. Communications systems are the key to the operations of these aircraft and to the successful accomplishment of their missions. Moreover, the ability to pass needed 
data between components of the systems depends upon 

available frequencies and adequate bandwidth to move the 

data as quickly as possible. Technology promises to offer 

solutions to a number of these challenges, but it is not the 

only answer for spectrum and bandwidth availability. Other 

possible solutions include acquiring additional spectrum 

resources, making changes to acquisition processes, and 

developing better management tools and processes capable 

of helping alleviate current difficulties.

In this paper, Lt Col Mary E. Griswold discusses the basics of the electromagnetic spectrum and UAS operations, 

pointing out how frequency management and bandwidth 

availability are key to UAS operations. She illustrates this 

through examples of difficulties encountered during military 

operations with spectrum and bandwidth issues. Finally, 

she notes that solutions to the current challenges are found 

in the employment of both short- and long-term actions in 

these areas to improve and optimize the use and availability 

of spectrum support for UAS operations in the future.

As with all other Maxwell Papers, this study is provided 

in the spirit of academic freedom and is open to debate and 

serious discussion of issues. We encourage your response.

 STEPHEN J. MILLER

 Major General, USAF

 Commandant, Air War College

iv
v

About the Author

Lt Col Mary E. Griswold, USAF, is deputy director of operations, 754th Electronic Systems Group, Maxwell-Gunter 

AFB, Alabama. A career communications officer, she has 

commanded at the flight and squadron levels and served 

in support and staff assignments at the wing, center, major 

command, and joint levels. Prior to becoming a student at 

Air War College, Colonel Griswold was the chief, Operations 

Division, Directorate of Communications, Headquarters Air 

Combat Command, Langley AFB, Virginia. She earned a 

bachelor’s degree in computer science from BirminghamSouthern College, Birmingham, Alabama, and received her 

commission through the Reserve Officer Training Corps. 

She holds master’s degrees in business administration and 

management as well as strategic studies. Colonel Griswold 

is a 2008 graduate of the Air War College.

vii

Abstract

Can the future of highly technical unmanned aircraft systems (UAS) depend on something as minor as frequencies? 

The answer is an overwhelming yes, and, by the way, frequencies and spectrum management are not minor players 

in today’s global operations.

The Department of Defense’s (DOD) Unmanned Aircraft 

Systems (UAS) Roadmap, 2005–2030 (Washington, DC: Office of the Secretary of Defense, 4 August 2005) reported an 

increased demand from combatant commanders for UAS 

support, stating that the DOD’s challenge is “the rapid and 

coordinated integration of this technology to support the 

joint fight” (1). This increased demand could be the logical 

effect of a February 2004 report by the Defense Science 

Board recommending that the acquisition and operational 

fielding of unmanned aerial vehicles be accelerated. Despite 

promoting their increased fielding and use, both documents 

are open about deficiencies and challenges.

The road map lists problem areas highlighted by combat operations, including the lack of communications frequencies; furthermore, the Defense Science Board report 

identifies communication bandwidth constraints as an area 

needing more attention and new development. As UASes 

become even more sought after and as their numbers increase, something must be done to help ensure that their 

much-needed capabilities are available to war fighters when 

needed. Frequency management and bandwidth availability are keys to the successful future of UAS operations; 

this paper recommends the employment of both short- and 

long-term actions as solutions.

Technology promises to offer solutions to a number of 

UAS challenges, but that is not the only answer for spectrum and bandwidth availability. A very obvious answer 

to not having adequate frequencies or bandwidth (but one 

very difficult to execute) is to acquire more for use by the 

military, either permanently or temporarily. Unfortunately, 

treaties and international agreements control spectrum allocation on a global level and are neither easily nor quickly 

changed. Some future challenges can be alleviated by several possible alterations in the way spectrum-dependent 
systems are acquired, and changes in the testing of systems 

under development offer another possible answer to spectrum supportability. Moreover, better management tools 

could alleviate future challenges in managing frequencies 

and bandwidth.

The success of future UAS operations depends on the 

availability of needed frequencies and bandwidth. Both 

short- and long-term solutions to current challenges are 

possible and must be implemented to mitigate the negative 

effect of these limited resources. The tremendous capabilities that these systems can bring to support the war fighter 

demand that we solve the current problems and meet the 

challenges presented by spectrum and bandwidth availability. Electromagnetic-spectrum constraints should not 

drive the future of UAS employment.

viii


Introduction

As recently as September 2007, Deputy Secretary of Defense Gordon England directed the establishment of a task 

force to coordinate unmanned aircraft system (UAS) issues 

and determine a way ahead to provide for “common, joint, 

and operationally effective UAS programs.”1 Aren’t the systems we have now common, joint, and operationally effective? Why the need for a task force, and why did he mention 

specific areas to address, including streamlining acquisition 

and management, interoperability, integration of UASes into 

civil airspace, use of frequency spectrum and bandwidth, and 

payload and sensor management?2 The answers are not easy 

ones; mainly, they concern the issue of increasing demand 

for these systems and their products, as well as the existing challenges. The communications area of frequency and 

bandwidth availability represents one case in which these 

challenges will continue to increase as demand grows.

The Department of Defense’s (DOD) Unmanned Aircraft 

Systems (UAS) Roadmap, 2005–2030 of August 2005, 

which reported an increased demand from combatant commanders for UAS support, stated that the DOD’s challenge 

is “the rapid and coordinated integration of this technology 

to support the joint fight.”3 This increased demand could 

be the logical effect of a February 2004 report by the Defense Science Board recommending that the acquisition 

and operational fielding of unmanned aerial vehicles (UAV) 

be accelerated.4 Despite promoting the increased fielding 

and use of these aircraft, both documents are open about 

deficiencies and challenges. The road map lists problem 

areas highlighted by combat operations, including the 

lack of communications frequencies; the Defense Science 

Board report notes communication bandwidth constraints 

as an area needing more attention and new development.5

As UAS capabilities become even more sought after and as 

the number of these aircraft increases, something must be 

done to help ensure that they are available to war fighters 

when needed.

Frequency management and bandwidth availability are 

keys to the successful future of UAS operations, and the solution to the current challenges is the employment of both 

short- and long-term actions in these areas. To illustrate 
the problems and solutions, this paper will first cover some 

basics of the electromagnetic spectrum and spectrum management that will facilitate the examination of UAS operations. This includes some history of how UASes evolved to 

their current uses and how they operate. After looking at 

examples of difficulties experienced in military operations 

dealing with spectrum and bandwidth issues, the paper 

concludes with recommendations for improving and optimizing the use and availability of spectrum support for UAS 

operations in the future.

Electromagnetic Spectrum

To be effective, this discussion first needs to note a few 

definitions. The electromagnetic spectrum can be defined 

as the “range of frequencies of electromagnetic radiation 

from zero to infinity,” but this study will consider it the 

range of frequencies allocated for use by the international 

community in agreed-upon tables of frequency allocation.6

Electromagnetic spectrum, radio frequency (RF) spectrum, 

and spectrum are terms often used interchangeably in discussions of this medium.7 Radio waves and microwaves, 

two parts of this vast spectrum, are very important to communications systems, especially military communications, 

and access to this “critical, finite national resource” is vital 

to military operations.8

Almost as important as access to needed spectrum is 

spectrum management. Its purpose is to ensure that systems dependent on spectrum are able to perform their 

designed functions in their designed environment without 

causing unacceptable interference or being affected by 

such interference.9 According to DOD Directive (DODD) 

4650.1, Policy for Management and Use of the Electromagnetic Spectrum, proper spectrum management “shall be 

an integral part of, and essential to, military planning, 

research, development, testing, and operations involving 

spectrum-dependent systems.”10

Basics

Electromagnetic radiation is all around us, usually in the 

form of invisible waves of energy.11 Communications signals 

use these waves to transmit data, and the rate per second at 
which these waves cycle is the signal’s frequency (one cycle 

per second is a hertz, 1,000 cycles per second is a kilohertz, 

etc.).12 Figure 1 shows part of the spectrum primarily used 

by communications systems. Changes in the length of the 

wave across the spectrum, from very short to very long, 

cause each subset of the spectrum, or band of frequencies, 

to have unique characteristics, which can affect how the 

wave travels through Earth’s atmosphere.13 The superhigh 

frequency bands, which have extremely short wavelengths, 

are often called microwaves.14 Scientists who first discovered these microwave frequency bands during World War II 

gave them letter designations, which remain in use today.15

Bandwidth refers to a range of frequencies occupied by a 

given wave or, most often, the amount of data capable of 

transmission in a given amount of time.16

Acquiring Spectrum Resources

International treaties control global use of the spectrum, 

along with laws and regulations for use within the United 

States and its possessions, all of them dividing the specFigure 1. Electromagnetic spectrum. (Adapted from Mark Long, “Frequencies for Satellite Communications,” http://www.mlesat.com/Article9 

.html [accessed 13 December 2007].)

4"5&--*5&,B#"/%	m()[


4"5&--*5&,V#"/%	m()[


4"5&--*5&$#"/%	m()[


6)'57#30"%$"45	m.)[


7)'57$)"//&-4m	m.)[


'.3"%*0#30"%$"45	m.)[


7)'57$)"//&-4m	m.)[


$*5*;&/4#"/%3"%*0$)"//&-4	.)[


".3"%*0#30"%$"45	m.)[


4)'461&3)*()'3&26&/$:

6)'6-53")*()'3&26&/$:

7)'7&3:)*()'3&26&/$:

.'.&%*6.'3&26&/$:

-'-08'3&26&/$:

7-'7&3:-08'3&26&/$:

()[(*(")&35;

.)[.&(")&35;

L)[,*-0)&35;


.)[


.)[

.)[

.)[

.)[

L)[

L)[

L)[

4)'

6)'

7)'

4)0358"7&4

.'

-'

7-'
trum into sections defined by the type of service using it 

(e.g., radio navigation or fixed satellite), type of user (government or nongovernment), and region of the world (there 

are three regions).17 Because spectrum is a finite resource, 

competition has begun between competing interests, and 

governments who control it are being pressured to “sell off” 

or allocate bandwidth to commercial interests.18 Those portions remaining become more congested and more difficult 

to deconflict among users.19 Acquiring sufficient spectrum 

and bandwidth to support military operations continues to 

be challenging, but this environment in which national government is pressured to reallocate current government and 

military portions of the spectrum for commercial or private 

use will present even greater challenges.20

The finite nature of spectrum resources makes it necessary to closely control use of the allocations currently owned 

by the military. Both a frequency allocation and a frequency 

assignment must be obtained by any new US government 

system desiring to use any portion of the spectrum; usually, 

a new system will not be allowed to interfere with an existing 

system having an equal- or higher-priority assignment.21

Spectrum supportability is the term for an assessment of 

whether or not the spectrum that is needed to support a 

system continuously from development through testing and 

into operational use is available—or will be available.22 It requires a system to have at least an equipment-spectrum certification, a reasonable assurance that sufficient frequencies 

are available from host nations to support operations, and 

an electromagnetic-compatibility consideration.23 A system 

receives an equipment-spectrum certification from authorities in nations where the system has the potential to operate, 

after their review of information on its technical characteristics. The certification indicates whether or not the system 

meets the nation’s spectrum-management requirements.24

The process of developing spectrum-dependent systems 

is strictly controlled in order to help ensure continued 

availability. DODD 4650.1 states that spectrum-dependent 

equipment or systems shall not be developed or procured 

without reasonable assurance that required electromagnetic spectrum is or shall be available to support the development, testing, and operation of that equipment or 

system; it further notes that no spectrum-dependent “off-
the-shelf” system shall be purchased or procured without 

the assurance that spectrum supportability has been or 

can be obtained.25 In order to ensure that this guidance 

is followed, acquisition processes added required steps to 

address the allocation of spectrum for a system in design 

or development (fig. 2). Necessary work to obtain spectrum 

supportability should be started as early as possible and 

occur during the technology-development phase of system 

acquisition.26 Other steps prevent a system from going into 

the development and demonstration phase or the production and deployment phase unless it has a spectrumsupportability determination completed or a waiver granted 

by increasingly higher levels of government acquisition officials.27 DOD guidance also requires systems purchased 

off the shelf or through other-than-normal acquisition processes to have a spectrum-supportability determination before they are acquired.28 This process is made more difficult because most systems are designed within the United 

States and meet US requirements, but there is normally 

no way to predict where the systems may be used outside 

the United States.29 These potential limitations of spectrum 

availability and use in other countries must be considerations during the development and purchase of systems, 

including UASes.30

Operations of Unmanned Aircraft Systems

Citing an agreed-upon definition of the terms in use will 

ensure common understanding in the discussions to follow. 

Joint Publication (JP) 1-02, Department of Defense Dictionary of Military and Associated Terms, defines an unmanned 

aircraft as “an aircraft or balloon that does not carry a human operator and is capable of flight under remote control 

or autonomous programming” and a UAV as a “powered, 

aerial vehicle that does not carry a human operator, uses 

aerodynamic forces to provide vehicle lift, can fly autonomously or be piloted remotely, can be expendable or recoverable, and can carry a lethal or nonlethal payload.”31

It further states that a UAS includes the component parts 

needed to control an unmanned aircraft, including all the 

necessary equipment, personnel, and network capability.32

Even though they have distinct differences, in many in-
stances the terms UAS and UAV are used interchangeably. 

However, definitions don’t describe how these systems got 

to today’s military operations and how they work, which are 

keys to understanding the challenges they face. A bit of history can give us an idea of how they came to be, and some 

basics on system operations can begin to build insight into 

the complex issues surrounding them.

History

UAS beginnings are much earlier than one might expect. 

In 1918 Elmer Sperry, in partnership with the US Navy, 

demonstrated the first powered, unmanned flight with a 

naval aerial torpedo and led the way for future development 

in unmanned flight.33 The 1920s saw the US military progFigure 2. Spectrum management and the acquisition process. 

(Adapted from Joint Program Executive Office Joint Tactical Radio System [JPEO JTRS], “JTRS Overview for CCEB [Combined Communications Electronics Board] Spectrum Task Force,” 3 May 2006, 31, http://

jpeojtrs.mil/files/tech_overview/CCEB_JTRS.pdf.)

Concept

Refinement

Concept

Refinement

Decision

Critical

Design

Review

FRP

Decision

Review

Technology

Development

System Development

and Demonstration

Production and

Deployment

Operations and

Support

LRIP/OT&E

Pre-Systems

Acquisition Systems Acquisition Sustainment

SpectrumSupportability

Analysis

Band

Selection

Start HNA

Coordination

E3 Requirement

Definition

Define EME

E3 Requirement

Definition

Stage 1 Stage 2 Stage 3 Stage 4 Maintain 1494

4QFDUSVN

1MBOOJOH

%%'.

 

EMC and E3 Analysis/Testing

Mitigation Measures

Continue Host-Nation

Coordination

Update EME as Required Update EME as Required Update EME as Required

Full E3 Testing

Initial Permanent Frequency

Assignments

HNA

Deployed Suppport

Permanent Frequency

Assignments

ECP Upgrades and P3I

JCIDS

Analysis ICD

IOC FOC

CDD CPD

A B C

CPD (Updated to Support FullRate Production Decision)

(Acquisition Decision)

IOC = initial operating capability

FOC = full operating capability

LRIP/OT&E = low-rate initial production / 

operational test and evaluation

FRP = full-rate production

EMC = electromagnetic compatibility

E3 = electromagnetic environmental effects

HNA = host-nation authorization

ECP = engineering change proposal

P3I = preplanned product improvement

EME = electromagnetic environment

DD FM = DOD form

JCIDS = Joint Capabilities Integration and Development System

ICD = initial capabilities document

CDD = capabilities development document

CPD = capabilities production document
ress to using remote radio control of an unmanned aircraft, 

and during the 1930s and ’40s, remotely operated target 

drones were used in a variety of training areas.34 Drones 

continue to be valuable assets to the US military today for 

research and testing as well as training. Technological advancements equipping them with advanced navigational 

systems resulted in the development and use of surveillance and reconnaissance UAVs in the 1950s and ’60s.35

The SD-1 Observer, developed by Northrop Grumman and 

equipped with externally mounted cameras, was the first 

tactical-reconnaissance UAV; this technology, the basis for 

adapting target drones into surveillance and reconnaissance platforms, was just the beginning.36

Continuing research resulted in advancements in technology and capabilities. The 1960s saw the introduction of 

the Air Force’s Lightning Bug, based on target-drone technology from the Ryan Aeronautical Firebee, which was able 

to conduct longer flights than previous UAVs and at higher 

altitudes.37 First used in Vietnam in 1964, the Lightning 

Bug completed over 3,400 tactical surveillance and reconnaissance missions during the war, gathering imagery on 

valuable military targets, including enemy surface-to-airmissile sites and locations of prison camps.38

Outside the United States, Israel did much UAV research 

and development in the 1970s, developing the Scout for 

military use.39 It was the first “genuine remotely controlled 

UAV prototype with adequate sensors and stable electrooptic systems required for functionality on a small platform” 

and could operate at 15,000 feet, performing missions up to 

six hours.40 It proved hugely successful in Israel’s war with 

Lebanon in 1982, locating Syrian air-defense resources and 

gathering electronic signals and frequencies used during 

Israeli attacks to destroy air-defense sites.41 Noting Israel’s 

success in the use of UAVs, the United States and other 

nations began development of their own programs, but US 

UAVs did not see significant military use again until Operation Desert Storm in the 1990s.42

Developed in the 1980s, the Pioneer was one of the first 

major US UAVs, considered the first generation of UAVs using RF technology.43 In 1994 the Air Force first used the 

Predator, which became a tremendous asset to operations 

in Bosnia in 1995.44 It has also performed operational 
missions in Kosovo, Afghanistan, and Iraq, in addition to 

missions in the United States to support border patrol.45

In 2002 a Predator conducted its first operational missile 

launch, targeting and destroying a vehicle believed to be 

carrying suspected terrorists and thus offering another example of evolution in the capabilities of UASes.46

The Global Hawk, another system in the current fleet 

of Air Force UASes, made its first flight in 1998 and has 

supported combat operations around the globe, flying 

thousands of hours in operational missions.47 The first unmanned, powered vehicle to fly across the Pacific Ocean, 

doing so in 2001, it is one of many UASes continuing to 

play a big part in ongoing operations.48 Data gathered in 

September 2004 showed over 100,000 flight hours by approximately 20 types of US and coalition UASes supporting 

Operations Enduring Freedom and Iraqi Freedom.49 UAS 

operations continue to reflect the importance of their capabilities in military operations.

Unmanned Aircraft System Basics

In order to begin to discuss the difficulties and challenges 

of UAS employment, we must have a basic understanding 

of the components of a UAS and how it works. As described 

in its definition, mentioned earlier, a UAS is made up of a 

number of parts or components, including the aircraft itself 

as well as all the support systems. One of the most critical 

major subsystems—communications—allows information 

to be passed between the aircraft and its ground elements 

or to other airborne assets, enabling a UAV to be guided 

and controlled from virtually anywhere at any time.50 Bandwidth is needed to support the systems providing data to 

control the UAV in flight, including its launch and recovery, 

and to send data from the onboard sensors or payload to its 

processing centers.51 These communications are done primarily through the use of RF applications, including both 

line of sight (LOS) and beyond line of sight (BLOS) systems 

and data-link communications.52

A data link is a pathway to send data between entities 

or, according to JP 1-02, “the means of connecting one location to another for the purpose of transmitting and receiving data.”53 A UAS data link typically consists of an RF 

transmitter and a receiver, an antenna, and modems to 
link these parts with the sensor systems.54 For UASes, data 

links serve three important functions: (1) as uplinks from 

the ground station and/or a satellite to send control data to 

the UAV, (2) as downlinks from the UAV to send data from 

the onboard sensors and telemetry system to the ground 

station, and (3) as a means for allowing measurement of 

the azimuth and range from the ground station and satellite to the UAV to maintain good communications between 

them.55 Efforts to standardize data links have resulted in 

the use of the common data link (CDL), typically a fullduplex, wideband data link when used by UASes, usually 

jam resistant and secure.56 The CDL is the DOD standard 

for high-capacity data communications of airborne sensor 

data.57 These links connect the ground station with the UAV 

via direct, point-to-point links or use satellite communications (SATCOM) in either X or Ku bands.58 They can pass 

uplink command and control data at rates ranging from 0.2 

to 2 megabits per second (Mbps) and downlink data from 

the onboard sensors at rates from 10 to 274 Mbps.59

The system specifics of UASes continue to evolve with 

improvements in technology. The Pioneer of the 1980s used 

C-band and ultrahigh frequency (UHF) LOS communications for its uplink as well as C-band LOS for its downlink.60 Its data rate of 7.317 kilobits per second (Kbps) was 

extremely slow when compared to today’s possible rates 

and was the result of limitations in spectrum as well as 

limited power available in the small, lightweight vehicle.61

Today’s Global Hawk UAS is made up of the aircraft, the 

launch and recovery element (LRE), and the mission control element (MCE).62 The LRE controls the aircraft using 

LOS CDL, LOS UHF, and BLOS UHF radios, while the MCE 

uses narrow-band LOS UHF radio and UHF SATCOM with 

Inmarsat backup for command and control.63 Although the 

MCE can control the aircraft with the same capabilities of 

the LRE, it is also responsible for control of the onboard 

sensors and receipt and distribution of the sensors’ products transmitted from the aircraft to the MCE using either 

LOS CDL or Ku-band SATCOM.64 Figure 3 illustrates the 

parts of the Global Hawk system and communications 

paths between the elements.

Predator operations use similar concepts as well. Performing functions similar to those of parts of the Global 
10

Hawk system, the Predator UAS has its aircraft, a ground 

control station (GCS), and an LRE. Having a purpose similar 

to that of the Global Hawk MCE, the GCS consists of equipment to control flight operations and sensor payload using 

LOS data-link and Ku-band SATCOM data-link equipment 

as well as VHF/UHF radios.65 The Predator LRE contains 

enough equipment to successfully launch and recover the 

aircraft, controlling it during takeoffs and landings using 

the LOS data link, which must be maintained until it transfers control to the GCS because the LRE has no BLOS communications capabilities.66

Communications systems are key to the operations of 

UASes as well as the successful accomplishment of their 

missions. The ability to pass needed data between components of the systems depends upon available frequencies 

and adequate bandwidth to move the data as quickly as possible. For takeoff and landing operations, data-link requirements are only in the several-Kbps range, while requirements to transmit sensor data from the onboard sensors 

can exceed 250 Mbps.67 Bandwidth requirements continue 

to increase. Estimated requirements for future capabilities 

Global Hawk Ku SATCOM

60,000–65,000 Feet Altitude UHF SATCOM

Greater than 300 Knots Airspeed 1.5–50 Mbps

LOS and

Relay

Sensor Data

1.5–274 Mbps

Sensor Data

1.5–50 Mbps

UHF

Command and

Control

UHF

Command and

Control

MCE

Forward

DCGS

Afloat

DCGS

Theater /

Tactical Users

Joint Force Air Compnent Commander

LRE

Distributed

Common

Ground

Surface System

(DCGS)

In-Garrison

or In-Theater

Global Hawk Ku SATCOM

60,000–65,000 Feet Altitude UHF SATCOM

Greater than 300 Knots Airspeed 1.5–50 Mbps

LOS and

Relay

Sensor Data

1.5–274 Mbps

Sensor Data

1.5–50 Mbps

UHF

Command and

Control

UHF

Command and

Control

MCE

Forward

DCGS

Afloat

DCGS

Theater /

Tactical Users

Joint Force Air Component Commander

LRE

Distributed

Common

Ground

Surface System

(DCGS)

In-Garrison

or In-Theater

Figure 3. Global Hawk communications architecture. (Adapted from

Unmanned Aircraft Systems [UAS] Roadmap, 2005–2030 [Washington, 

DC: Office of the Secretary of Defense, 4 August 2005], C-3.)
11

in 2015 and beyond are 548 Mbps for Global Hawk sensor 

data and 44.7 Mbps for Predator.68

Issues with Spectrum Support

in Military Operations

Difficulties in acquiring adequate spectrum and bandwidth to support military operations have negatively affected the mission and are documented as far back as 

Desert Storm and up to ongoing operations in Afghanistan 

and Iraq. In order to develop solutions, we must examine 

the problems and their causes.

The lack of available bandwidth to transmit data is a fundamental problem. In Desert Storm, DOD satellites provided only 75 percent of the bandwidth needed during peak 

capacity, with the remainder provided by North Atlantic 

Treaty Organization systems and leased from commercial 

satellites.69 Demand for bandwidth in Operation Allied Force 

was more than twice that used in Desert Storm, and even 

after optimizing the available military bandwidth, the Defense Information Systems Agency (DISA) still had to contract for more than $20 million in commercial satellite 

bandwidth.70 During Enduring Freedom, Lt Gen Harry 

Raduege Jr., the director of DISA at the time, observed 

that “we’re supporting one-tenth the number of forces deployed during Desert Storm with eight times the commercial SATCOM bandwidth” and that “Global Hawk consumed 

five times the total bandwidth used by the entire US military in the Gulf.”71 Recently, the current director of command, control, communications, and computer systems for 

US Central Command (CENTCOM/J6) was quoted as saying, “It’s astronomical how much satellite communications 

we have over in our [area of responsibility]”; he also talked 

about the “unbridled proliferation” of systems requiring 

satellite bandwidth.72

A host of additional challenges affects UAS operations. 

Simultaneous operations of two Predators from Bosnia during Allied Force required 6 Mbps of bandwidth for each to 

support dissemination of its video, severely stressing available resources and necessitating preemption of lower priorities when the Predators were operating.73 Predator and 

Global Hawk operations in Afghanistan and Iraq continue to 
12

highlight the critical nature of SATCOM to UASes. The high 

data rates required for the systems’ imagery products cannot 

be supported by DOD satellites, so channels are leased from 

commercial satellites to provide the needed data.74 With this 

comes great dependence on other-than-military resources 

that are subject to unavailability due to purchase by others 

or refusal of service from private vendors.75 Operations also 

show that the limited number of available frequencies often 

restricts the number of airborne UAVs to one at a time, even 

though abundant capability exists to operate more of them 

simultaneously.76 According to a US Central Command Air 

Forces staff member, there are only two assigned frequency 

sets for use in Balad, Iraq, which limits the number of unmanned aircraft operated and launched from the airfield.77

Other problems include the loss of a communications link 

to an unmanned aircraft due to frequency interference, 

usually caused by friendly sources or by the urban environment of current operations.78

Availability of frequencies for use in deployed operations 

and interference to systems are always sources of difficulty. 

As explained earlier, control of spectrum allocation and use 

of spectrum-dependent systems are up to each country, 

within its borders, and can vary from nation to nation. Frequencies authorized for use in one country may not be authorized for use in another.79 In Iraqi Freedom, the Army’s 

Hunter UAV did not operate for the first 30 days in-theater 

because it was awaiting frequency deconfliction in order 

to obtain operational frequencies to use.80 An improperly 

configured UAV payload caused interference, resulting in 

problems with the UAV’s downlink communications during 

operations in the Balkans.81 An electronic-countermeasure 

system supporting Iraqi Freedom experienced friendly interference from a UAV because the aircraft deployed without first receiving spectrum support and failed to acquire it 

after arriving in-theater.82 Can anything be done to alleviate 

these problems?

Recommendations

According to Renee Puels, the DOD’s UAV road map lists 

objectives for better defining the role of UAVs in military operations out to the year 2030, noting that technology is the 
13

“enabler” for reaching most of the objectives.83 Technology 

promises to offer solutions to a number of UAS challenges, 

but it’s not the only answer for spectrum and bandwidth 

availability. Other possible solutions include acquiring additional spectrum resources, making changes in the acquisition system, and conducting other process-related actions 

capable of helping alleviate today’s difficulties.

Utilizing Technological Advances

Advances in electromagnetic-spectrum technology offer 

future solutions to problems with military and UAS bandwidth availability. One such advance is optical data links, 

or lasercom, with bandwidth possibly two to three times 

greater than that of RF systems, low probability of intercept, 

30–50 percent less weight than comparable RF systems, 

and resistance to interference and jamming.84 Lightweight 

electro-optical systems with low power requirements can 

also be a benefit to UASes.85 Unfortunately this technology has not progressed as rapidly as desired because there 

continue to be problems acquiring and maintaining a link 

due to insufficient pointing, acquisition, and tracking technology; furthermore, no current technology is capable of 

supporting the data rates.86

Technological advances in other areas could offer advantages as well, but they are not readily available currently. Applications enabling sensors to cover large surveillance areas 

would select for transmission only the data of interest. This 

would decrease current downlink requirements.87 A similar 

effort to reduce needed downlink-bandwidth rates involves 

data compression, possibly having near-term effects, but the 

technology could still benefit greatly from improvements.88

Acquiring More Spectrum

A very obvious answer to having inadequate frequencies 

or bandwidth (but one very difficult to execute) entails acquiring more for use by the military, either permanently 

or temporarily. As discussed earlier, treaties and international agreements control spectrum allocation on a global 

level, a process managed by the World Radiocommunication Conference.89 The United States began to address UAS 

spectrum issues at the international level by proposing an 
14

agenda item at the next conference to consider the impact 

that UASes will likely have on spectrum requirements.90

The US proposal states that UAV use around the world is 

expected to experience tremendous growth over the next 10 

years and that, despite the potential need for more spectrum 

in the aeronautical-mobile and/or aeronautical-mobilesatellite use areas, studies should be conducted to assess 

potential requirements and identify frequency bands that 

would best support those requirements.91 Previous studies 

done in response to an agenda item in a prior conference 

made several conclusions affecting the future of UAS operations: (1) significant growth is projected in this section of 

aviation, (2) future UAS use will include operations in nonsegregated airspace, (3) when operating in nonsegregated 

airspace, these aircraft must be safely integrated and use 

the same operational practices as manned aircraft, and (4) 

additional communications requirements will be needed in 

order to ensure safety.92 The studies also noted that shortterm increases can possibly be absorbed with existing allocations but that much larger deployments of UAVs will 

require additional spectrum.93

Short-term acquisition of bandwidth and spectrum support can provide an easier answer, but, as discussed earlier, 

it has risks. Lease or purchase of bandwidth from commercial sources is very expensive, and sources may not be immediately available to meet mission requirements. Vendors 

able or willing to provide adequate bandwidth at the needed 

place and time could jeopardize mission accomplishment if 

we rely on them as the sole means of obtaining additional 

spectrum support.94

Changing Acquisition Processes

Future challenges can be alleviated by several possible 

changes in the way spectrum-dependent systems are acquired. As described earlier, the current acquisition process for spectrum allocation ties accreditation of spectrum 

support to a specific device, propagating the inflexibility of 

spectrum assignments.95 This process could be made more 

flexible by accrediting classes of equipment within certain 

parameters to operate within a constrained range of frequencies, which would then be assigned and managed by 

the gaining service or organization. This, however, would 
15

require drastic changes to the current DOD processes as 

well as extensive coordination across a number of federal 

entities, both of which would be very time-intensive endeavors with potentially uncertain results.

Changes in the testing of systems under development 

offer another possible answer to spectrum supportability. 

Systems acquired as commercial, off-the-shelf products are 

normally tested using US commercial spectrum; when used 

by the military, they still maintain the lower priority given to 

nongovernment systems and may be prohibited for use outside the United States.96 To decrease fielding and operational 

problems, we should implement plans to transfer these systems to military-use spectrum or to limit their purchase if 

different spectrum support cannot be obtained. In discussing communications challenges and bandwidth constraints 

in his area of responsibility, the CENTCOM/J6 remarked 

that systems should be designed and tested “in a bandwidthconstrained environment first, as opposed to running them 

in the Beltway or running them just over fiber.”97

Developing Better Management Tools and Processes

If a commander is not aware of spectrum- and bandwidth-availability problems that affect mission accomplishment, he or she cannot prioritize use of available resources 

to best support the overall mission. Much like programs 

that provide airspace situational awareness, spectrummanagement functions must have tools available to provide 

needed situational awareness in order to track this valuable 

resource and provide needed information to leadership. 

CENTCOM communicators see the need for tools to manage 

and deconflict spectrum, based on priorities established by 

theater leadership.98 Operational trade-offs have been made 

in UAV operations when multiple systems must share the 

same frequencies—one mission must end so that another 

can get airborne.99 Planners not only need automated tools 

to allocate available bandwidth to achieve the best possible 

result, but also require the ability to conduct a “what if” 

analysis of various scenarios to identify potential problems 

and solutions.100 We should also conduct research to develop new tools for this purpose or to modify existing ones 

in order to provide an accurate, real-time, usable representation of electromagnetic-spectrum resources.
16

Conclusion

The success of future UAS operations depends on the 

availability of needed frequencies and bandwidth. Both 

short- and long-term solutions to current challenges are 

possible and must be implemented to mitigate the negative 

effect of these limited resources. By looking at the basics 

of electromagnetic spectrum, spectrum management, and 

UAS operations, this paper has shown the critical relationships among them. Examples of difficulties experienced in 

military operations dealing with spectrum and bandwidth 

issues illustrated their importance. We must evaluate 

short-term solutions, such as purchasing bandwidth from 

commercial vendors, and long-term solutions, such as using optical data links or acquiring permanent frequencies 

for military use. Moreover, we must integrate them into an 

immediate remedy for the current problems with UAS operations and optimize the use and availability of spectrum 

support for UAS operations in the future.

Development and deployment of UASes continue at an 

ever-increasing rate and appear to assume not only that 

needed spectrum and bandwidth will be available for these 

systems when needed, but also that commanders understand how this finite resource will affect their operations.101

The tremendous capabilities that these systems can bring 

to support the war fighter demand that we address and mitigate the current problems and challenges with spectrum 

and bandwidth availability. Electromagnetic-spectrum constraints should not drive the future of UAS employment.

Notes

1. Gordon England, deputy secretary of defense, to secretaries of the 

military departments; chairman of the Joint Chiefs of Staff; undersecretaries of defense; commanders of the combatant commands; assistant secretaries of defense; general counsel of the Department of Defense; director, Administration and Management; and director, Program Analysis and 

Evaluation, memorandum, 13 September 2007.

2. Ibid.

3. Unmanned Aircraft Systems (UAS) Roadmap, 2005–2030 (Washington, DC: Office of the Secretary of Defense, 4 August 2005), 1.

4. Defense Science Board Study on Unmanned Aerial Vehicles and Uninhabited Combat Aerial Vehicles (Washington, DC: Office of the Under 

Secretary of Defense for Acquisition, Technology, and Logistics, February 

2004), cover memo.
17

5. Unmanned Aircraft Systems (UAS) Roadmap, 45; and Defense Science 

Board Study, cover memo.

6. Department of Defense Directive (DODD) 4650.1, Policy for Management and Use of the Electromagnetic Spectrum, 8 June 2004, 9.

7. Ibid.

8. Ibid., 2.

9. Ibid., 10.

10. Ibid., 2.

11. Mark Long, “Frequencies for Satellite Communications,” 1, http://

www.mlesat.com/Article9.html (accessed 13 December 2007).

12. Ibid., 2.

13. Ibid.

14. Ibid., 3.

15. Ibid.

16. Wikipedia: The Free Encyclopedia, s.v., “Bandwidth (Signal Processing).”

17. Unmanned Aircraft Systems (UAS) Roadmap, C-17.

18. Lt Col Kurt A. Klausner, “Command and Control of Air and Space 

Forces Requires Significant Attention to Bandwidth,” Air and Space Power 

Journal 16, no. 4 (Winter 2002): 72.

19. Ibid.

20. Mario Lucchese, Dr. C. Leslie Golliday Jr., and Dr. Anil N. Joglekar, 

“Operational Evaluation of Electromagnetic Environmental Effects (E3): 

New DOT&E [Director, Operational Test and Evaluation] Policy Calls for 

More Systematic Assessment of E3,” PM, May–June 2000, 42, http://

www.dau.mil/pubs/pm/pmpdf00/luccm-j.pdf.

21. Unmanned Aircraft Systems (UAS) Roadmap, C-17.

22. DODD 4650.1, Policy for Management and Use, 10.

23. Ibid.

24. Ibid.

25. Ibid., 3.

26. Ibid.

27. Ibid.

28. Ibid.

29. Unmanned Aircraft Systems (UAS) Roadmap, C-17.

30. Ibid.

31. Joint Publication (JP) 1-02, Department of Defense Dictionary of Military and Associated Terms, 12 April 2001 (as amended through 4 March 

2008), 569, http://www.dtic.mil/doctrine/jel/new_pubs/jp1_02.pdf.

32. Ibid.

33. Renee Puels, “Unmanned Aerial Vehicles (UAVs) Enabled by Technology,” Student Publication for TCOM 598, Independent Study of Telecommunications (Fairfax, VA: George Mason University, December 2006), 

2, http://telecom.gmu.edu/studPub.html (accessed 18 October 2007).

34. Ibid., 2–3.

35. Ibid., 3.

36. Ibid.

37. Ibid.

38. Ibid.

39. Ibid., 4.
18

40. Ibid.

41. Ibid., 4–5.

42. Ibid.

43. Ibid., 20–21.

44. Ibid., 22.

45. Ibid.

46. Ibid.

47. Ibid., 24.

48. Ibid.

49. Unmanned Aircraft Systems (UAS) Roadmap, i.

50. Puels, “Unmanned Aerial Vehicles,” 6–7.

51. Defense Science Board Study, 23.

52. Ibid.; and Puels, “Unmanned Aerial Vehicles,” 6, 20.

53. JP 1-02, Department of Defense Dictionary, 142.

54. Puels, “Unmanned Aerial Vehicles,” 19.

55. Ibid.

56. Unmanned Aircraft Systems (UAS) Roadmap, C-7, C-8.

57. Ibid., C-7.

58. Ibid., C-7, C-8, C-14.

59. Ibid., C-8.

60. Puels, “Unmanned Aerial Vehicles,” 20–21.

61. Ibid.

62. Unmanned Aircraft Systems (UAS) Roadmap, C-2.

63. Ibid.

64. Ibid.

65. Ibid.

66. Ibid.

67. Defense Science Board Study, 23.

68. Ibid.

69. Klausner, “Command and Control,” 5.

70. Ibid.

71. Ibid., 3.

72. Quoted in Rita Boland and Robert K. Ackerman, “Innovation, Diversification Define CENTCOM Communications,” SIGNAL, November 2007, 22, 

http://www.afcea.org/signal/articles/templates/Signal_Article_Template 

.asp?articleid=1427&zoneid=219.

73. Klausner, “Command and Control,” 3.

74. Unmanned Aircraft Systems (UAS) Roadmap, C-11.

75. Ibid.

76. Ibid., 68.

77. John DeBerry, US Central Command Air Forces A6X, Shaw AFB, 

SC, to the author, e-mail, 29 October 2007.

78. Unmanned Aircraft Systems (UAS) Roadmap, 68.

79. The U.S. Air Force Remotely Piloted Aircraft and Unmanned Aerial Vehicle Strategic Vision (Washington, DC: Department of the Air Force, 2005), 

14, http://www.af.mil/shared/media/document/AFD-060322-009.pdf.

80. “Operation Outreach,” CALL [Center for Army Lessons Learned] 

News Letter, no. 03-27 (October 2003): 6, http://www.fas.org/irp/agency/

army/call1003.pdf.

81. Lucchese, Golliday, and Joglekar, “Operational Evaluation,” 42.
19

82. Brig Gen Gregory L. Brundidge, director of communications, Langley AFB, VA, to Air Combat Command (ACC)/CC and ACC/CC IOI mailing 

list, e-mail, 19 January 2007.

83. Puels, “Unmanned Aerial Vehicles,” 35.

84. Ibid., 25.

85. Ibid., 26.

86. Unmanned Aircraft Systems (UAS) Roadmap, 50; and Puels, “Unmanned Aerial Vehicles,” 27.

87. Defense Science Board Study, 23.

88. Unmanned Aircraft Systems (UAS) Roadmap, 50.

89. Frederick R. Wentland, associate administrator, Office of Spectrum 

Management, to Mr. John Giusti, Federal Communications Commission, 

memorandum, 7 November 2006, 1.

90. Ibid.

91. Ibid., 3–4.

92. Ibid., 2.

93. Ibid.

94. Klausner, “Command and Control,” 7.

95. Department of Defense Net-Centric Spectrum Management Strategy

(Washington, DC: Office of the Assistant Secretary of Defense [Networks 

and Information Integration] and Department of Defense Chief Information Officer, 3 August 2006), 9.

96. Unmanned Aircraft Systems (UAS) Roadmap, C-16.

97. Quoted in Boland and Ackerman, “Innovation, Diversification,” 24.

98. Ibid.

99. Klausner, “Command and Control,” 7.

100. Ibid., 7–8.

101. Ibid., 6.