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Page 1
Executive Summary
Extraordinary growth is evident in capabilities for
''untethered" communications, the union of wireless and mobile
technologies. An example is cellular telephones, which were
virtually unheard of in 1980 and are now used by almost 200 million
subscribers worldwide. The subscriber base for wireless
communications services is growing 15 times faster than the
subscriber base for wired services; by 2010 wireless and wired
systems are expected to serve equal numbers of users. The vigorous
public demand for wireless services is fueling intense industrial
and government activity, including research and development
(R&D) aimed at improving the quality and reducing costs of
wireless technology, design of innovative systems and services, and
implementation of new technical standards and policies. This
dynamic environment is producing diverse wireless technologies and
standards, in stark contrast to other areas of communications
marked by a convergence toward uniformity. All this activity will
bring the reality of the next century close to the vision of
"anytime, anywhere" communications.
Historically, U.S. national defense needs have stimulated many
advances in wireless communications technologies, and the
Department of Defense (DOD) has been among the first users. Today,
however, some DOD systems lag the state of the art. Whereas the
commercial sector has greater incentives than ever before to push
the technology envelope—at a cost driven down by a growing
mass market—some military wireless equipment is based on 1970s
and 1980s technology. The adequacy of the current defense
communications infrastructure was called into question
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Page 1
Executive Summary
Extraordinary growth is evident in capabilities for
''untethered" communications, the union of wireless and mobile
technologies. An example is cellular telephones, which were
virtually unheard of in 1980 and are now used by almost 200 million
subscribers worldwide. The subscriber base for wireless
communications services is growing 15 times faster than the
subscriber base for wired services; by 2010 wireless and wired
systems are expected to serve equal numbers of users. The vigorous
public demand for wireless services is fueling intense industrial
and government activity, including research and development
(R&D) aimed at improving the quality and reducing costs of
wireless technology, design of innovative systems and services, and
implementation of new technical standards and policies. This
dynamic environment is producing diverse wireless technologies and
standards, in stark contrast to other areas of communications
marked by a convergence toward uniformity. All this activity will
bring the reality of the next century close to the vision of
"anytime, anywhere" communications.
Historically, U.S. national defense needs have stimulated many
advances in wireless communications technologies, and the
Department of Defense (DOD) has been among the first users. Today,
however, some DOD systems lag the state of the art. Whereas the
commercial sector has greater incentives than ever before to push
the technology envelope—at a cost driven down by a growing
mass market—some military wireless equipment is based on 1970s
and 1980s technology. The adequacy of the current defense
communications infrastructure was called into question
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during the Gulf War, when voice and data systems failed to keep
up with rapidly moving front-line troops. Only 10 percent of
soldiers currently have voice communications capabilities, and only
satellites, certain aircraft, and "smart" missiles carry sensors
for still imagery or video.
Changes in military operations are stimulating DOD interest in
untethered systems. U.S. military personnel now need to be prepared
to move quickly throughout the world to respond to rapidly evolving
regional conflicts and carry out a variety of noncombat roles, such
as peacekeeping and humanitarian response. Just as past hardware
advances (e.g., aircraft carriers, long-range jet aircraft) shaped
the military conflicts of yesteryear, information technology is now
shaping plans for the nation's future defense. Plans are being made
for a digitized battlefield in which sensors are widely
distributed, and rapidly deployable, multimedia wireless systems
extend from front-line soldiers all the way to the Pentagon and the
North Atlantic Treaty Organization (NATO). Advanced command,
control, communications, computing, and intelligence (C4I) systems will make it possible to
monitor an adversary on a computer screen, target specific threats,
and neutralize them with the press of a button.
The DOD is taking a dual approach to meeting its future
communications needs by funding selected R&D and demonstration
projects, focusing primarily on components, while also relying
increasingly on commercial off-the-shelf (COTS) technologies. In
the Gulf War, for example, the military obtained
satellite-transmitted positioning data using commercial receivers,
which were rapidly fielded to meet an urgent military need. On the
other hand, for some military applications, commercial products do
not meet stringent requirements for security, interoperability, and
other capabilities. And yet, with defense budgets flat or
declining, the DOD can no longer rely solely on military suppliers
to provide defense-unique solutions. The military needs to find a
way to ride the wave of commercial technology advances while
maintaining technical capabilities that exceed those of any
potential adversary.
This report, the result of a one-year study by the Computer
Science and Telecommunications Board (CSTB) of the National
Research Council, recommends strategies and R&D to help the DOD
field state-of-the-art, cost-effective untethered communications
systems that meet military needs. The report concentrates on
wireless technologies that use the radio frequency (RF) part of the
electromagnetic spectrum. The study was funded by the Defense
Advanced Research Projects Agency (DARPA) to address the following
questions:
•
What technologies, products, and services will the commercial
industry make available on its own, and when?
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•
What are the military requirements and needs in mobile wireless
information technology?
•
To what extent will commercial technology development support
military needs?
•
Where can DARPA have the greatest impact in technology
development or acceleration of technology development to support
the military?
Answers to those questions are outlined in this summary, which
contains two major sections. The first section presents the
report's five conclusions and summarizes the supporting facts and
analysis contained in Chapters 1 through 3 of the report. The
conclusions represent the expert judgments of the 15 members of the
CSTB's Committee on the Evolution of Untethered Communications. The
second section presents the committee's 12 recommendations, which
are based on the conclusions and the supporting facts and analysis.
The recommendations, which are directed to DOD and DARPA, are
discussed in detail in Chapter 4. It should be noted that although
the report focuses on military needs, it also contains a wealth of
information about commercial technology developments as well as a
primer on the many technical challenges involved in designing
wireless systems. The report therefore should also interest a
wider, civilian audience.
Conclusions
A large gap remains between public expectations for mobile
communications and the available technology. Voracious
consumer demand is stimulating many advances in wireless
communications technology, particularly cellular and cordless
telephones. As of 1997 there were more than 50 million cellular
subscribers in the United States. The portfolio of wireless
services now available in the commercial marketplace includes a
wide range of telephony, paging, and data applications delivered
over a variety of service offerings, ranging from land-based mobile
radio to cellular and satellite communications. Each service offers
a unique combination of coverage region, bandwidth (i.e.,
capacity), subscriber equipment features, and connectivity.
In the aggregate, commercial wireless capabilities are
considerable. Yet many technical challenges remain. Wireless
systems, especially those serving mobile users, are extremely
complex. A network needs to be capable of rerouting information
seamlessly and efficiently as users move, and sophisticated digital
signal processors (DSPs) and antennas are needed to minimize
interference, distortion, jamming, and interception without undue
power burdens on portable devices. The cost of wireless voice
systems remains high compared to that of wired networks, and
transmission quality and security could be improved. Specialized
wireless data networks
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have not taken off as yet, perhaps because they are not powerful
enough or because two-way mass market applications have yet to
emerge.
For a worldwide operator, the management and coordination of
diverse systems are complicated by the absence of any trend toward
convergence toward a single standard in wireless communications.
One digital wireless technology, global system for mobile
communications (GSM), is deployed throughout Europe and in more
than 100 countries worldwide, whereas the Japanese use their own
technology, the personal handyphone system (PHS), and the United
States supports three competing technologies: GSM, a time-division
system (IS-136), and a code-division system (IS-95). The diversity
of technologies in the United States is a result of spectrum
regulation policies, which require only that systems not interfere
with one another. These policies leave interoperability and other
system properties such as quality and efficiency to be settled in
the marketplace.
Over the next 10 years or so, market forces will fill the
gap between public expectations and the available technology by
developing new technologies for commercial wireless
communications. Fueled by the success of cellular
communications and projections of ever-expanding markets for
wireless services, U.S. and foreign industries are performing
extensive R&D to overcome remaining technical challenges in
wireless systems. For example, efforts are under way to enable
portable devices to communicate at the high bit rates needed for
advanced information services. In addition, to foster economies of
scale in R&D and manufacturing in a world of diverse and
changing technical standards, considerable effort is dedicated to
advancing the technology of software radios. These radios, by
downloading different types of operating software, can serve as
single platforms that transmit signals conforming to a variety of
standards.
The European Union, which supports cooperative research leading
to development of precompetitive technologies, has a vision of the
future extending beyond 2002, when universal mobile
telecommunication services are scheduled to be deployed. That
vision and various industry road maps suggest that, by early in the
twenty-first century, commercial wireless communications will
achieve the "anytime, anywhere" paradigm.
This optimism does not extend to prospects for fully
interoperable wireless communications systems anytime soon. In the
United States, wireless communications research is performed by
individual companies in the context of their own product plans, and
coordination occurs primarily in standards-setting organizations
(e.g., Telecommunications Industry Association, Internet
Engineering Task Force). Moreover, in the past there was a
proliferation of proprietary rather than open network interfaces.
The trends toward open systems and digital components will make
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it easier to build customized systems, but the capabilities of
commercial services will continue to depend on consumer demand as
well as trade-offs between technology availability and costs.
The military has much to gain from positioning itself to
use COTS communications equipment to the greatest extent
possible. The civilian and military sectors have a long
history of interaction in the design and deployment of wireless
technology, such as mobile radios and satellite systems. Commercial
wireless technologies are now more attractive than ever in terms of
their performance, quality, and cost. By acquiring commercial
equipment when it meets military needs, the DOD can field
state-of-the-art equipment while also lowering its costs by
benefiting from the economies of scale achievable in mass-market
manufacturing. For example, software radios for military
applications can be built using many COTS components, such as
analog-to-digital converters, DSPs, RF amplifiers, displays,
batteries, and data-storage devices.
The insertion of commercial technologies into military systems
is not always easy. As an example, asynchronous transfer mode (ATM)
offers many attractive features, such as high-speed transmission,
fast switching, the capability to assign message priority, and
queue management. It could provide the basis for improved
situational awareness, enabling the DOD to provide real-time
imagery, cryptographic security, and low-cost devices for wide
distribution. However, the integration of ATM and Internet
protocols into wireless battlefield communications will require
sophisticated link protocols. Industry is addressing these issues,
but the DOD can ensure that its needs are met only by participating
in standards-setting activities to influence technology directions
and by testing emerging COTS products in battlefield exercises.
Some military needs for wireless communications
technologies will exceed or differ significantly from anticipated
commercial developments. For example, the military has unique
concerns with respect to network design, security,
interoperability, and multimode/multiband systems. Although
there is clearly overlap between the capabilities of commercial
technologies and the DOD's needs, they also differ in a number of
respects (see Table ES-1). For example, commercial R&D on
integrated (i.e., multimedia) systems is oriented toward
base-station-oriented network architectures, an efficient and
reliable design in which mobile users communicate with central
access nodes. An alternative is the easily reconfigurable
peer-to-peer architecture, in which network elements communicate
directly. It is not yet clear which architecture will be the most
appropriate in future military settings. Improved modeling and
simulation tools, especially for communications traffic and
mobility of network
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TABLE ES-1 Comparison of Commercial Wireless
Technologies and Future Military Needs
Feature
Commercial Systems
Future Military Needs
Architecture
Base-station oriented
Not clear at this time
Mobility
Mobile terminals, fixed infrastructure
Mobile terminals, many mobile infrastructure
elements
Deployment strategy
Site-specific planning and measurements
Rapid deployment at unpredictable locations
Modes/waveforms
Six at most
Currently 1 to 20; ideal is multimode systems
using adaptive waveforms
Frequency range (per system)
Narrowband (one band per system)
Multiband (e.g., 2 megahertz to 2 gigahertz)
Data rate
384 kilobits per second to 2 megabits per second
(Mbps) by 2002
Long-term goal is at least 10 Mbps
System access
Anyone who can pay
Universal
Interoperability of systems
Increasingly important
Required for all defense networks and foreign
allies
Security
Increasingly important
Critical
Antijam
May become an issue with widespread system use
Critical
Low probability of detection/interception
Not an issue at this time
Critical
Robustness of systems and equipment
Yes, under moderate conditions
Yes, under extreme conditions (e.g., extreme
temperatures, shock, vibrations, submersion)
Interference rejection
Somewhat important
Critical
elements, would support realistic analyses of complex military
networks and the design of appropriate protocols and optimization
algorithms.
Commercial capabilities and military needs also differ with
respect to the security of networks, radio links, and hardware.
Commercial users
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are concerned mainly with privacy and the prevention of
unauthorized access to their hardware and data. Some security
breaches are tolerated (in fact, analog cellular telephones
typically provide no link security). By contrast, the military
requires end-to-end encryption to prevent unauthorized access and
monitoring of network activity. The military also requires hardware
security to prevent an adversary who is opening a device from
discerning the hardware or software secrets. Military systems also
benefit from antennas and other technologies designed to make
signals difficult to detect, jam, or intercept.
Interoperability is another area in which the DOD's needs exceed
the interests of the commercial sector. Advanced military wireless
systems need to be compatible with the 17 legacy communications
networks as well as systems operated by NATO and the United
Nations. One means of achieving this objective is the software
radio. Now the focus of several military R&D programs, the
ideal military software radio is a multimode, multiband unit using
many different waveforms over a broad frequency range, whereas
commercial versions are likely to offer less flexibility and
operate in a single frequency band. To make optimal use of this
promising technology, the DOD needs to support specialized R&D
focusing on antennas, filters, and adaptive waveforms.
The commercial sector has its own incentives to produce
advanced communications devices, components, and subsystems as well
as complete systems. To use commercial technologies effectively,
the DOD will have to take special measures to promote the
development and acquisition of COTS products that can be integrated
into systems that meet specialized military requirements.
Current commercial R&D and standards activities seek to enable
the transmission of many types of information, including data,
video, and images, to and from portable wireless devices. Although
this work is certain to create new technology, the commercial
deployment of the technology is not assured. The availability of
the technology in the marketplace will depend on business, social,
and government policy factors. Military planners will need to
maintain a continuing awareness of the differences between what is
possible technically and what is available in the market to meet
military needs.
As part of this process, the DOD needs to translate its
operational requirements into technical specifications that can be
used to determine the suitability of commercial wireless
technologies for military applications. New approaches to
procurement, as well as technology demonstration and testing rather
than development, will help DOD obtain the greatest return on its
investments. In addition, by fully understanding the barriers to
synergy between the commercial and defense sectors, the DOD can
develop processes for accommodating or overcoming these
barriers.
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For example, the commercial sector tends to add functions to
equipment only if economically justified by customer demand; by
participating in standards-setting activities the DOD can encourage
the design of COTS products that can be more easily modified to
meet military needs.
Recommendations
The committee's 12 recommendations are organized from the
general to the specific. The first three recommendations identify
organizational changes that DOD should make to foster an
environment conducive to the absorption of state-of-the-art
commercial wireless communications technologies. The other nine
recommendations identify research that should be undertaken by
DARPA to fill gaps in commercial development efforts and ensure
that advanced wireless systems meet military needs. The research
recommendations are presented in order of priority, reflecting the
committee's view that top-level systems issues are paramount. The
remaining recommendations deal with subsystems and components.
Organizational Changes
1.
The DOD should participate in standards-setting activities for
wireless communications technologies and systems.
2.
The DOD should pursue a vigorous process of technology
demonstration and testing prior to extensive development and
procurement. In particular, the focus should be on systems concepts
based on commercial technologies and specialized military
enhancements.
3.
The DOD should plan a new approach to procurement that will
identify how commercial infrastructure systems and subscriber
equipment can best be used for military purposes and how to
purchase commercial equipment in the most productive way.
Systems Research
4.
DARPA should build on current research in modeling and
simulation to incorporate the communications traffic, mobility of
network elements, and radio propagation encountered in mobile
military information networks.
5.
DARPA should initiate research to produce network architectures
that incorporate commercial products in a manner that meets
military requirements.
6.
DARPA should conduct research aimed at understanding and
bridging the differences between security needs in commercial and
military networks.
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7.
DARPA should conduct research aimed at reducing co-site
interference.
Component Research
8.
DARPA should carry out research and demonstration projects
designed to field software radio technology for military
applications.
9.
DARPA should conduct the research needed to adapt smart antennas
for mobile military applications.
10.
DARPA should conduct research to produce transmission techniques
that adapt to a wide range of operating conditions.
11.
DARPA should conduct research to overcome the limitations of
current filter technology for use in military software radios and
high-density platforms.
12.
DARPA should develop novel components to enhance the flexibility
of software radios.
Representative terms from entire chapter:
commercial wireless
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