IEEE Wireless Communications - April 2017 - page 8

IEEE Wireless Communications • April 2017
6
B
ook
R
eviews
E
dited
by
S
atyajayant
M
isra
Cognitive Radio: Interoperability Through
Waveform Reconfiguration
By Leszek Lechowicz and Mieczylaw Kokar;
Artech House; 1st Edition; 2016; ISBN-13:
978-1608077533; hardcover, 270 pages
Reviewer: Satyajayant Misra
The proliferation of mobile and wire-
less devices and the complementary
increase in their bandwidth demands
are presenting real challenges to push
the envelope of wireless communica-
tions. This has resulted in the building of
new wireless technologies, such as soft-
ware-defined radios (SDRs), cognitive
radios (CRs), and MIMO antennas. There
have also been accompanying improve-
ments in software methods, such as net-
work virtualization and protocol design
to leverage multiple wireless interfaces
simultaneously. CRs, SDRs, or CR+SDR are
being explored in the research domain
presently to meet the needs for higher
spectrum bandwidth and wireless reli-
ability. CRs are specifically designed to
be aware of the radio environment in
their vicinity and choose a frequency
and bandwidth for communication that
is allocated to a primary user (e.g., TV
station), but is not in use at the moment.
In that sense, CRs cannot only help
improve wireless bandwidth utilization,
but also help meet applications’ band-
width demands with more success.
The big challenge in CR communica-
tion is for the two communicating radios
to talk to each other. In many cases, the
two radios cannot communicate despite
being unobstructed on account of them
not having a set of common waveforms
(QPSK, BPSK, etc.) to communicate
with. This sometimes requires the radi-
os to negotiate and one radio to inform
the other radio device how to recreate
the waveform to enable communica-
tion. This is termed dynamic auto con-
figuration or interoperability. Often, such
interoperability requires the creation of
an ontology for describing the different
parameters needed for efficient negotia-
tion and also to perform accurate nego-
tiation to learn the waveform. This book
discusses the concepts that are needed
for understanding and realizing a cog-
nitive radio that implements dynamic
interoperability via waveform reconfigu-
ration. The book is organized into nine
chapters with each chapter ending in
useful references.
The first chapter introduces the
notion of automatic reconfiguration and
static/dynamic waveform reconfigura-
tion. The chapter discusses the need for
dynamic reconfiguration with an exam-
ple, illustrates how such a reconfigura-
tion can happen, and the challenges
thereof. The chapter also presents a
summary of what the other chapters in
the book deal with. Chapter 2 provides
an introduction to the digital signal pro-
cessing (DSP) approaches used in the
domain. It will serve as a good refresher
for readers who know the concepts and
is also a good starting point for readers
who are not that well versed. The chap-
ter presents various signals, namely dis-
crete-time, complex valued, and periodic
and aperiodic. It covers Fourier analysis
and discrete and linear time invariants.
Chapter 3 presents an overview of the
SDR technology. It starts with a brief his-
tory of the origins of SDR, several key
SDR characteristics, such as multi-func-
tionality, global mobility, compactness
and power efficiency are discussed.
The chapter also includes a discussion
of SDR hardware and software architec-
tures.
Chapter 4 deals with CR. Again, the
chapter starts with an introduction of
the concept of CR, which is followed
by a discussion of the cognitive theo-
ries and architectures. The chapter also
includes a discussion of cognitive radio
architectures and also of CR ontologies.
The authors discuss a CR as an intelli-
gent self-controlling agent. The chap-
ter discusses dynamic reconfiguration
in CR and does not consider dynamic
spectrum access or policy manage-
ment. Chapter 5 presents a broad dis-
cussion of interoperability in terms of
the different definitions. The authors
introduce four main levels of interop-
erability: machine, syntactic, semantic,
and organization. The discussion in this
book centers on semantic interopera-
bility where the radios can communi-
cate and understand each other. The
discussion begins with the need for two
radios to understand each other’s wave-
forms for interoperability. The idea of
reconfiguration based on assembling
of the waveform for reconfiguration is
also discussed. The discussion includes
the need for physical layer reconfigu-
rability, a review of interoperability and
reconfiguration literature, and the cor-
responding requirements.
In Chapter 6, the authors discuss
the languages that can be used for CR
reconfiguration. Several languages such
as OWL, Rules, Metaslang, CL, LTL, and
Accord are discussed, along with the
selection decision for the choice of the
language used. Several concepts such as
declarative versus imperative languages,
web ontology language, negation and
open versus closed world reasoning, and
functional equivalency are discussed.
The chapter concludes with a discussion
of the problem with most formal lan-
guages — they are functional and lack
the memory property, whereas, the rep-
resentation of behavior in CR requires
results from prior operations and also
have a temporal aspect. The chapter
provides a very good background for
looking into CR ontologies.
Chapter 7 deals with component
based software development (CBSD).
The development of software to codify
a waveform can be best done by break-
ing the implementation into different
components, which is what the authors
suggest is the best way to develop SDR
software. CBSD provides a good way to
abstract the functionalities for ease of
representation and code development.
This chapter presents concepts used for
CBSD, such as process algebras, the
software communication architecture,
the SpecC language, which is used for
embedded systems coding, the service
oriented architecture, and the waveform
definition language. Chapter 8 discusses
ontology based cognitive radio recon-
figuration and waveform reconstruction.
The chapter starts with a representation
of the waveform components, and the
process of construction of the compo-
nents from ontological specifications is
described. The chapter concludes with
code generation that includes the behav-
ioral aspects modeled by state machines.
The chapter presents a base SDR ontol-
ogy, the general system architecture,
discusses the overview of the waveform
reconfiguration, and the components
and state machines and their inherent
designs.
Chapter 9 presents an example
implementation, which serves as a proof-
of-concept system built for the ontolo-
gy-based reconfiguration of the CRs. The
implementation, in Java, consists of two
CRs communicating over the network in
a master-slave arrangement. The chapter
presents several lower-level implemen-
tation details, the waveforms used, the
testing harness, and details of the experi-
ments performed.
This book provides a multi-faceted
view of the CR and SDR domains and
their overlap. It is a good book for begin-
ners and also a decent reference book
for practitioners.
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