IEEE Communications Magazine • April 2008
72
0163-6804/08/$25.00 © 2008 IEEE
The views presented here
are those of the authors
and do not necessarily
reflect the views of the
IEEE SCC41 or its pro-
jects.
INTRODUCTION
The idea of cognitive radio (CR) as an alterna-
tive wireless communication paradigm, capable
of managing and executing itself in real-time
without human intervention, was first proposed
by Joseph Mitola III and Gerald Q. Maguire, Jr.
[1]. In the utopian world of ubiquitous comput-
ing, each device would be equipped only with
CR, thus empowering it to communicate on any
available spectrum. The question, however, is
where to look for the unused spectrum with the
myriads of wireless devices employed around the
globe and with a status quo in spectrum regula-
tions. As demand for radio resources increases,
industry and academia are searching for efficient
methods to share the spectrum — the wireless
domain real-estate.
Essentially, there are two models of spectrum
allocation and usage:
•
Owned — where spectrum is sold or allo-
cated to service providers or agencies who
have the sole ownership of the spectrum.
• Common — where anyone can use the spec-
trum with an agreed upon etiquette.
The first model is dominating the current wire-
less world, but it is inefficient. This observation
was strengthened by a study of the New Ameri-
can Foundation with the cooperation of the
Shared Spectrum Company to find the extent to
which the spectrum is currently used [2]. Mea-
surements in the 30–300 MHz band show that
utilization of some of the radio channels is less
than one percent, whereas the average occupan-
cy over all the frequency bands is only 5.2 per-
cent. Surprisingly, the maximum total spectrum
occupancy for New York City during one such
measurement was found to be only 13.1 percent.
Even during the peak hours of usage, one could
find free spaces in the spectrum of the public
bands. Thus, we may conclude that dividing
spectrum into blocks is inefficient and the rigid
allocation policies of regulators have resulted in
an artificial scarcity of radio resources [3]. For
this reason, dynamic spectrum access (DSA)
concepts such as spectrum pooling and oppor-
tunistic spectrum access (OSA) are gaining
momentum in academia and industry. Compa-
nies like Vanu, Inc. and Shared Spectrum Com-
pany, projects like the DARPA XG, the EU
E2R, the Dutch Adaptive Ad Hoc Free Band
Wireless Communications (AAF) project, and
research groups in numerous universities are
focusing on CR.
Since many technical, managerial, and finan-
cial aspects are associated with CR concepts
(including software-defined radio (SDR)), there
is a need to standardize processes, terms, and so
on. Further, the efforts so far by many individual
groups are incoherent due to the lack of com-
mon understanding. Therefore, strong coordina-
tion is required between regulators, academia,
and product developers. To some extent, this
coordination currently is lacking. To foster CR
development, the IEEE Standards Coordinating
Committee (SCC) 41 Standards Committee on
Next Generation Radio and Spectrum Manage-
ment has initiated a series of standards, the
IEEE 1900 series. This article attempts to give
an overview of IEEE SCC41. Some of the cur-
rent thoughts with respect to harmonization of
ABSTRACT
This article discusses recent standardization
efforts related to cognitive radio focusing on the
work of IEEE Standards Coordinating Commit-
tee 41, formerly known as IEEE 1900. Some
important tasks to be performed by the CR stan-
dardization community also are presented. These
tasks will expedite the introduction of CR
devices to the market while promoting a fair use
of scarce radio resources. Some avenues for
using the currently available standards for rapid
deployment of CR devices, such as ISO stan-
dards, also are discussed.
COGNITIVE RADIO COMMUNICATIONS
AND NETWORKS
R. Venkatesha Prasad and Przemyslaw Pawelczak, Delft University of Technology
James A. Hoffmeyer, Western Telecom Consultants, Inc.
H. Steven Berger, TEM Consulting
Cognitive Functionality in Next
Generation Wireless Networks:
Standardization Efforts
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IEEE Communications Magazine • April 2008
73
the IEEE 1900 series of standards and their cur-
rent state of development are included here. A
discussion on how to standardize CR-related
processes with the currently available standard-
ization and accreditation means is also presented
here.
A LOOK AT THE HISTORY OF THE
DEVELOPMENT OF OPEN SPECTRUM
ACCESS SYSTEMS AND REGULATIONS
Before discussing issues related to CR standard-
ization, it is beneficial to look briefly at the his-
tory of CR systems. Dynamic or opportunistic
spectrum sharing is not a novel concept and is
probably as old as radio communication itself.
One of the first communication systems using
shared radio resources was maritime communi-
cation (1910s). Around 1960, the Federal Com-
munications Commission (FCC) allowed the use
of shared channels, citizen band, and in land
mobile communication systems. With the advent
of wireless data communication, the Aloha pro-
tocol, proposed in 1970, enabled sharing of the
radio channels for wireless data communication
without using a centralized entity. This indirectly
gave way to an FCC Rule Part 15 (1985) that
described the coexistence procedures for low-
power wireless devices in the industrial, scientif-
ic, and medical (ISM) bands. Even though the
Etiquette and the Listen Before Talk (LBT) pro-
tocols were not yet defined, their huge success
resulted in the opening of the 5 GHz band (U-
NII). The British Cordless Telephone Second
Generation Standard (mid 1980s) was another
example of a successful and distributed channel
management technique. SDRs were developed
and enabled even greater flexibility in radio
access.
The first attempt at realizing SDR was in
1987 through project ICNIA by Air Force Rome
Labs (AFRL), which was followed by the
DARPA and AFRL SPEAKeasy I and II pro-
jects (1990 and 1996). Later the U.S. Navy Digi-
tal Modular Radio (2000), and finally, the JTRS
HMS Radio (2004) projects were initiated. In
2002, the FCC issued the 98-153 docket on ultra-
wideband (UWB) communication. Recently
released FCC docket 03-122 revisited Rule 15,
allowing wireless data users to share channels
with radar systems on an LBT basis. Later the
FCC realized that CR techniques are the future
substrate that stimulates the full growth of open
spectrum (see FCC dockets 03-108 on CR tech-
nique and 04-186 on CR in TV spectrum). The
previous discussion is consolidated in Fig. 1.
Further information can be found in [4; 5, Chap-
ter 1].
IEEE SCC41 STANDARDIZATION
EFFORTS ON COGNITIVE RADIO
Realizing the importance of coordinated work
around CR standardization, the IEEE created
the IEEE SCC41 [6] to address the issues relat-
ed to the deployment of next generation radio
systems and advanced spectrum management.
IEEE SCC41 was preceded by the IEEE 1900
task force, which initiated the IEEE standards
setting effort in this area. The task force was
started in the first quarter of 2005, jointly by the
IEEE Communications Society and the IEEE
Electromagnetic Compatibility Society. Finally
on April 21, 2007, the IEEE created a new gov-
erning body for all IEEE 1900 standards and
named it SCC41 on Dynamic Spectrum Access
Networks.
IEEE SCC41 is divided into four working
groups (WGs) and one study group, each respon-
sible for evolving standardization processes for
different aspects of CR. WGs are identified as
IEEE 1900.x, where .x represents one of the
WGs. Each WG shall submit a document to
IEEE after finalizing the recommendations thor-
ough discussions. After the documents are final-
ized, they are submitted to a vote arranged by
the IEEE Standards Association (SA). During
■ Figure 1. History of CR-like systems, with a view of the future.
DSA radio
Software defined radio
Software controlled radio
Hardware radio
Abramson’s
Aloha
protocol
British cordless
telephone second
generation (CT2)
FCC docket 03-108
on CR techniques
and FCC docket
04-186 on CR in
TV spectrum
Integrated
communications
navigation and
identification
architecture
(ICNIA)
U-NII
proposal
by Apple
Corp.
FCC rule
part 15
issued
Shared channel
communication
(2.182 kHz band)
Shared channel
land mobile
communication
(i.e., CB radio)
Radio reconfiguration flexibility
1910 1960 1970 1980 1990
Predicted trend
2000 2010 20201900
SPEAKeasy I
SPEAKeasy II
XG program
present first
successful tests
of DSA network
FCC issues 98-
153 docket on
ultra wideband
communication
JTRS HMS
radio
Cognitive radio
Dynamic or
opportunistic
spectrum sharing is
not a novel concept
and is probably as
old as radio
communication itself.
One of the first
communication
systems using shared
radio resources was
maritime
communication
(1910s).
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IEEE Communications Magazine • April 2008
74
the balloting, IEEE SA members vote with their
comments. Negative votes will be carefully con-
sidered by the working group, and the issues
addressed by it go to the next round of discus-
sions and/or rewriting and balloting again. Thus,
a fair chance is given to interested organizations
and individuals to make the standards applicable
to a wide spectrum of products using CR.
IEEE 1900.1: STANDARD DEFINITIONS AND
CONCEPTS FOR SPECTRUM MANAGEMENT AND
ADVANCED RADIO SYSTEM TECHNOLOGIES
Many groups working on CR-related topics have
defined CR and other related terms differently.
Thus, IEEE decided to create a 1900.1 WG
responsible for creating a glossary of important
CR-oriented terms and concepts. It further pro-
vides explanations to germinate a coherent view
of the various efforts that are taking place in the
broad arena of CR. The key idea is to standard-
ize and explain technically precise definitions
related to CR. In fact, 1900.1 WG acts as a con-
nection to the other IEEE SCC41 WGs, tying
them together with common definitions of CR
terms.
Some terms used in the literature have differ-
ent meanings, depending on context and intent.
Although the term cognitive radio has been used
for years, many authors and institutions are try-
ing to coin their own definitions and meanings.
For example, Mitola III defines CR in his Ph.D.
thesis as “the point in which wireless personal
digital assistants (PDAs) and the related net-
works are sufficiently computationally intelligent
about radio resources and related computer-to-
computer communications to detect user com-
munications needs as a function of use context,
and to provide radio resources and wireless ser-
vices most appropriate to those needs.” Howev-
er, the SDR Forum explains it as “a radio that
has, in some sense,
•
Awareness of changes in its environment
• In response to these changes adapts its
operating characteristics in some way to
improve its performance or to minimize a
loss in performance.”
One can easily see the differences between the
previous definitions. This emphasizes the impor-
tance of having common definitions and expla-
nations, which is the role of IEEE 1900.1 WG to
provide.
IEEE 1900.2: RECOMMENDED PRACTICE FOR
INTERFERENCE AND COEXISTENCE ANALYSIS
In the light of new CR technology, many radio
systems coexist, and they try to optimize the uti-
lization of spectrum in space and time. The
accurate measurement of interference has thus
become a crucial requirement for the deploy-
ment of these technologies. The mandate of the
1900.2 WG is to recommend the interference
analysis criteria and establish a well-thought-out
framework for measuring/analyzing the interfer-
ence between radio systems. New technologies,
although attempting to improve spectral efficien-
cy — by being flexible, collaborative, and adap-
tive — also cause disputes. Therefore, this WG
intends to establish a common standard platform
on which the disputing parties can present their
cases and resolve them amicably.
The framework for interference analysis
addresses the context of measurements and the
purpose. Any new adaptive system has a trade-
off between cost and gain. Thus, the interference
analysis should make this gain explicit along with
the usage model for which this trade-off is
accounted. Apart from the interference power
measurements and the context, impact and reme-
dies also are to be mentioned for the analysis
and comparison. Finally, parameters for analysis
are derived from scenarios including the context
and harmful interference thresholds. Uncertainty
levels in measurements are compulsorily consid-
ered in the analysis.
IEEE 1900.3: RECOMMENDED PRACTICE FOR
CONFORMANCE EVALUATION OF SOFTWARE
DEFINED RADIO SOFTWARE MODULES
On the software front, IEEE 1900.3 WG is devel-
oping test methods for conformance evaluation
of software for SDR devices. The aim is to define
a set of recommendations that help in assuring
the coexistence and compliance of the software
modules of CR devices before proceeding toward
validation and certification of the final devices,
as laid down in the IEEE 1900.2 and 1900.A.
Because SDR is an important component of
future CR networks, these recommended prac-
tices should help in creating high confidence in
the deployed SDR devices. These devices will
have multiple layers of software, each addressing
different functionalities. Therefore, it is all the
more essential to test the capability of SDR
devices a priori to installing the patches correctly
over the air, assuring secure execution of intend-
ed functionalities.
As an illustration, consider an implementa-
tion of the SDR device specifications into a pro-
gram. This can be verified with the formal
verification methods. However, formal specifica-
tions for software, mostly do not exist. There-
fore, testing in these cases becomes less formal
by focusing only on a particular subset of device
operations. The aim is to design testing proce-
dures that will comply with the semiformal soft-
ware specifications. One of the solutions is to
define checkpoints (mandatory and/or obligato-
ry) and assertions that will reflect the specifica-
tions. For these reasons, IEEE 1900.3 WG will
specify device management procedures. Because
many of those exist today (e.g., the Java Mobile
Device Management Server APIs), 1900.3 WG
will utilize other relevant standards to achieve its
goal.
IEEE 1900.4: COEXISTENCE SUPPORT FOR
RECONFIGURABLE, HETEROGENEOUS
AIR INTERFACES
Many mobile devices that are used today oper-
ate on multiple wireless networks. The study of
network and device architectures that can help
in distributed decision making for dynamic spec-
trum access (DSA) is an important area — com-
mercially, as well as academically. These
procedures particularly refer to reconfigurable
terminals (including SDR) capable of accessing a
The framework for
interference analysis
addresses the
context of
measurements and
the purpose. Any
new adaptive system
has a trade-off
between cost and
gain. Thus, the
interference analysis
should make this
gain explicit along
with the usage
model for which
this trade-off is
accounted.
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IEEE Communications Magazine • April 2008
75
multitude of radio access technologies. The
1900.4 WG will define the overall system archi-
tecture, splitting the functionality between termi-
nals and the network and also the information
exchange between coordinating entities. Its main
goal is to increase the overall system utilization
of reconfigurable terminals while increasing the
perceived quality of service (QoS). All 1900.4
enabled devices should operate in an oppor-
tunistic and dynamic manner such that they will
not degrade the performance of primary radio
access devices. The study of heterogeneity in
wireless access technologies and multi-homing of
the devices — with CR capability — differenti-
ates this WG from other WGs of SCC41. At
first, the 1900.4 WG will look into only the archi-
tectural and functional definitions. The corre-
sponding protocol definitions related to the
information exchange will be addressed at a later
stage.
IEEE 1900.A: DEPENDABILITY AND
EVALUATION OF REGULATORY COMPLIANCE FOR
RADIO SYSTEMS WITH
DYNAMIC SPECTRUM ACCESS
The topic of the IEEE 1900.A study group is
certification of DSA devices. Devices with poten-
tial cognitive capability bring new challenges for
the certification process. To prove that a radio
device always will remain within operational
boundaries is more difficult compared to tradi-
tional radios. Future hardware vendors must
know the design methodologies and testing pro-
cedures to affirm that their devices will not
interfere with a primary user of a given frequen-
cy channel. Many technical studies are involved
in this study group such as hazard analysis, list-
ing potential causes for out-of-compliance trans-
mission and description of previous
behavior-based certification efforts. In fact, its
most important task is to standardize the
dependability of a radio system vis-à-vis quanti-
fying the level of trust one has.
Different levels of trust can be defined for a
particular spectrum based on its primary user.
As an example, if a CR radio uses frequencies
assigned for avionics, it must have a high level of
confidence in its capabilities to detect the activi-
ties of the primary users. The capability assess-
ment of a radio system to adhere to the
regulations is the main focus of 1900.A.
The advantage of having this study is mani-
fold. For example, regulators may use these rec-
ommendations before certification, whereas
manufacturers may use them for the production
of systems that conform to the regulations. IEEE
1900.A has currently drafted a project authoriza-
tion request (PAR) for submission to the IEEE
Standards Association to become another inde-
pendent WG within IEEE SCC41 project.
RELATED STANDARDIZATION EFFORTS
Other IEEE projects related to next-generation
radio, like IEEE 802.{18,19,20,22} are the
sources of expertise for IEEE SCC41. As men-
tioned earlier, because active dialogue between
different standard bodies is crucial at this stage
of CR development, IEEE SCC41 has initiated
cooperation with the FCC, Federal Office of
Communication [UK] (OFCOM), SDR Forum,
and OMG Forum, to name a few. The relation
between different WGs of IEEE SCC41, as well
as different standardization bodies within and
outside IEEE are depicted in Fig. 2.
ADVANCES IN IEEE 1900.1:
A B
RIEF DISCUSSION OF COGNITIVE
RADIO FUNCTIONALITY AND
SOME DEFINITIONS
As mentioned earlier, there are many views on
what a CR is, and at times they conflict. Proba-
bly, the simplistic meaning of the term is a radio
that adapts to its surroundings. Many adjectives
were added later, often connecting CR with arti-
ficial intelligence, machine learning, and so on.
Now the horizon of CR is expanding with cogni-
tion entering many layers of the communication
stack. Therefore cognitive functionality is taken as
the basis here, whether the cognition is in the
radio, in the higher layers, or both. The idea is
to make communication devices tune their radio
and higher layer functions to utilize the available
spectrum efficiently. For academic purposes, the
unapproved (at the time of the writing of this
article) definition of CR is mentioned here from
the IEEE 1900.1 WG draft: “CR is:
•
Radio in which communication systems are
aware of their environment, internal state,
and location and can make decisions about
their radio operating behavior based on
that information
• Cognitive radio, as defined in the first, that
utilizes software defined radio, adaptive
radio, and other technologies to
autonomously adjust its behavior or opera-
tions to achieve the desired objectives”
In this context, CR is not limited to only the
radio layer. Until the time of having an agreed-
upon definition of CR from the IEEE 1900.1
draft standard, an alternative term called cogni-
tive functionality in wireless communication net-
work (CFWCN) is used here to represent the art
of efficient use of spectrum. This cognitive func-
tionality may be spread across the layers of the
communication architecture, resulting in coordi-
nation among the layers for an efficient use of
available spectrum. The implementation of cog-
nitive functionality includes technical, policy, and
regulatory issues.
Figure 3 explains the basic functional blocks
of a CFWCN node. Specifically, apart from a
reconfigurable radio, a CFWCN node has vari-
ous other components. The sensing block and
policies block (if available) are extensively used
in deciding the availability of spectrum. These
blocks also help to drive the learning and rea-
soning functions. The learning and decision
blocks may be implemented with fuzzy logic or
neural networks. The decision database along
with the input from the sensing block and poli-
cies block drives learning. The end result is that
the radio is configured based on input from dif-
ferent layers of the communication stack, as well
as the environment. Moreover, the view of IEEE
1900.1 WG is that the term cognitive radio used
in the literature generally means cognitive radio
Now the horizon of
CR is expanding with
cognition entering
many layers of the
communication
stack. Therefore
cognitive
functionality is taken
as the basis here,
whether the
cognition is in the
radio, in the higher
layers, or both.
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IEEE Communications Magazine • April 2008
76
systems — this has been reflected in the contri-
bution from IEEE 1900.1 to the initially drafted
study questions on CR to the International
Telecommunication Union-Radiocommunication
(ITU-R) Study Group 8, Working Party 8A
(approved later).
In fact, IEEE 1900.1 has recognized the pre-
viously mentioned view that cognition, aware-
ness, adaptability, and so on, may lie outside the
boundaries of the radio. This aspect is highlight-
ed by the additional word system.
In the following, other important definitions
from the current IEEE 1900.1 draft [7] are
reproduced. We note that some of these defini-
tions were developed after many rounds of dis-
cussion and are not yet approved by IEEE
officially; the authors claim no rights whatsoever
on any of these definitions.
Dynamic spectrum access: The near-real-time
adjustment of spectrum resource usage in
response to changing circumstances and objec-
tives; including interference experienced or cre-
ated; changes of the radio state (operational
mode, battery life, location, etc.); and changes in
environmental/external constraints (spectrum,
propagation, operational policies, etc.).
Opportunistic spectrum access: The method
by which spectrum users operating on a sec-
ondary (and possibly unlicensed) basis within a
frequency band with designated primary (and
possibly licensed) users exploit unused in-band
segments for their own purposes without causing
interference to the active interference-intolerant
primary users for the duration of the availability
of the spectrum in question.
Software-defined radio: A type of radio in
which some or all of the physical layer functions
are software defined. For example, it is feasible
that a radio has two or more modulation
schemes, each of which is implemented in hard-
ware. However, software control is used to switch
the radio characteristics. In the FCC and ITU-R
definitions, if such control is used in a radio, it is
considered to be SDR, even if the radio signal
processing is done entirely in hardware. IEEE
1900.1 does not consider software control to be
SDR.
Cognitive radio network: A network capable
of establishing links between its cognitive radio
nodes to establish connectivity and to adjust its
connectivity to adapt to changes in environment,
topology, operating conditions, or user require-
ments.
Quality of detection: A metric that implies
the quality of identification of spectral opportu-
nities that introduces a particular level of inter-
ference to the primary users of the channel but
not limiting a secondary network from accessing
it while it was vacated by the primary network
[8].
Spectrum broker: A device responsible for
dynamic assignment of particular frequency
channels to secondary devices [8].
Spectrum etiquette: A set of rules, policies,
and procedures that govern the behavior of a
collection of wireless networks.
■ Figure 2. Nesting of various IEEE SCC41 projects and their relation with other external organizations.
External bodies
IEEE SCC 41
IEEE 802 group
Software Defined
Radio (SDR) forum
IEEE 802.18: Radio
regulatory technical
advisory group
IEEE 802.19:
Coexistence
technical advisory
group
IEEE 802.21: Media
independent
handover services
technical advisory
group
IEEE 802.22:
Wireless regional
area networks
working group
IEEE 1900.2:
Recommended
practice for
interference and
coexistence
analysis
IEEE 1900.4:
Coexistence
support for
reconfigurable
heterogeneous
air interfaces
IEEE 1900.A:
Dependability and
evaluation of
regulatory
compliance for
radio systems with
dynamic spectrum
access
IEEE 1900.3:
Recommended
practice for
conformance
evaluation of
software defined
radio software
modules
International
Telecommunication
Union (ITU)
Object
Management
Group (OMG)
UK’s Office of
Communications
(OFCOM)
US Federal
Communications
Commission (FCC)
IEEE 1900.1:
Standard
definitions and
concepts for
spectrum
management and
advanced radio
system
technologies
Accreditation is to
provide confidence
in CABs through its
control function.
Similarly, ISO/IEC
17024:2003
specifies require-
ments for
organizations
certifying the
personnel, who in
turn oversee
conformity tests.
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