Reading time : Cognitive Radio :…

Paper comes from
: IEEE Journal on Selected Areas in Communications, Special
Issue on “Cognitive Radio: Theory and Application”, vol. 26, no. 1,
January 2008.
Radio spectrum
resource is of fundamental importance
in wireless communications. Nowadays, the access
to radio spectrum is largely based on fixed
spectrum allocation principle.With the deployment of more wireless
applications/services,most of the available spectrum has been well
allocated, thus many countries are facing the
problem of spectrum scarcity. On the other hand,
measurement studies have revealed that most of the
allocated spectrum experiences low utilization
efficiency. These two facts motivate the
introduction of dynamic spectrum access, which
allows secondary users to reuse/share the same
radio spectrum originally allocated to the primary(licensed) users.
PS: Radio
spectrum is not enough for our life and most of the allocated
spectrum experiences low utilization efficiency. So we need use CR
to solve these problems.

Cognitive radio is the enabling technology for dynamic
spectrum access. The essential components in a cognitive
radio system include spectrum sensing, cognitive
medium access control and cognitive networking.
The research on cognitive radio technology however
involves interdisciplinary effort from various
technical societies, including, e.g., signal processing,information
theory, communications engineering, as well as
cooperation/game theory societies. This Special
Issue focuses on the state-of-art research results
on cognitive radio and its applications. We have
received a total of 54 submissions, and after a
careful review process to asses the quality of the
papers, we accepted 17 papers in this Special Issue,
covering spectrum sensing, physical layer aspects,
medium access control (MAC), networking and game
theory for cognitive radio networks.
PS: CR
components : The essential components in a
cognitive radio system include spectrum sensing,
cognitive medium access control and cognitive
networking.Next are some paper about reserch of CR
recently.
The first set
of three papers is related to spectrum sensing in
cognitive radio networks.
In “Spatiotemporal Sensing in Cognitive Radio
Networks,”Ganesan, Li, Bing, and Li exploit the spatial diversity
in multiuser networks to improve the spectrum
sensing capabilities of centralized cognitive
radio networks.

In “Cyclostationary Signatures in Practical Cognitive
Radio Applications,” Sutton, Nolan, and Doyle
explore the cyclostationary signatures of the
communications signals for signal detection,
network identification and rendezvous and
discuss these in the context of dynamic spectrum
access.

In “Defense against Primary User Emulation Attacks
in Cognitive Radio Networks,” Chen, Park, and Reed
consider the security aspects of spectrum sensing
in cognitive radio networks where a secondary user
may transmit signals whose characteristics emulate
those of incumbent signals; and in order to
counter this threat, they propose a transmitter
verification scheme, which uses both signal
characteristics and location of the signal
transmitter to verify the presence of
primary users.

The second set
of four papers deals with physical layer aspects
of cognitive radio.
In “Joint Beamforming and Power Allocation for
Multiple Access Channels in Cognitive Radio
Networks,” Zhang,Liang, and Xin study the problems of maximizing
the throughput or ensuring the Quality-of Service
(QoS) of the secondary users, yet to maintain the
QoS of the primary user; they
consider single-input-multiple-output multiple
access channel and propose joint beamforming and
power allocation schemes to solve these
problems.

In “Frame Synchronization for Cognitive Radios
with Variable-Length Packets,” Suwansantisuk,
Chiani, and Win study the problem of synchronizing
the variable-length frames in cognitive radio
systems; they propose two performance metrics for
frame synchronization.

In “Cognitive Radio Based Multi-User Resource
Allocation in Mobile Ad Hoc Networks using
Multi-Carrier CDMA Modulation,” Qu, Milstein, and
Vaman propose a cognitive radio based multi-user
resource allocation framework for mobile ad hoc
networks using multi-carrier DS CDMA
modulation over a frequency-selective fading
channel.

In “Low-Complexity Adaptive Transmission for
Cognitive Radios in Dynamic Spectrum Access
Networks,” Pursley and Royster IV propose an
adaptive transmission protocol for the use in
cognitive radio networks where the links have
unknown and possibly time-varying propagation
losses.

The third set
of three papers deals with the MAC design
for cognitive radio networks.
In “Cognitive Medium Access: Constraining
Interference Based on Experimental Models,”
Geirhofer, Tong, and Sadler consider a cognitive
radio coexisting with multiple parallel WLAN
channels while abiding by an interference
constraint; they propose a Cognitive Medium Access
(CMA) recasting the coexistence problem as one of
constrained Markov decision processes.

In “HC-MAC: A Hardware-constrained Cognitive MAC
for Efficient Spectrum Management,” Jia, Zhang,
and Shen study the problem of conducting efficient
spectrum management in ad hoc cognitive network
while taking the hardware constraints into
consideration; they propose a
hardware-constrained cognitive MAC to perform
efficient spectrum sensing and spectrum access
decision.

In “Cross-Layer Based Opportunistic MAC Protocols
for QoS Provisionings Over Cognitive Radio
Wireless Networks,” Su and Zhang integrate the
spectrum sensing at physical layer with the
packets scheduling at MAC layer, for the wireless
ad hoc networks.

The fourth set
of four papers addresses the spectrum sharing and
cognitive networking.
In “Distributed Rule-Regulated Spectrum Sharing,”
Cao and Zheng consider the problem of efficient
and fair spectrum access in dynamic spectrum
Networks; they propose a distributed spectrum
management scheme using implicit
coordination instead of requiring a common
communication channel.

In “Spectrum Sharing for Multi-hop Networking
with Cognitive Radios,” Hou, Shi, and Sherali
investigate the problem of multi-hop networking
with cognitive radio nodes, each node has a pool
of frequency bands that can be used for
communication; they develop a mathematical
formulation with the objective of minimizing the
required network-wide radio spectrum resource for
a set of user sessions.

In “Cognitive Wireless Mesh Networks with
Dynamic Spectrum Access,” Chowdhury and Akyildiz
propose a COgnitive Mesh NETwork (COMNET)
algorithmic framework which realizes an
intelligent frequency-shifting selfmanaged mesh
network.

The last set of
three papers is related to the applications
of game theory in cognitive radio
networks.

In “Multi-Stage Pricing Game for
Collusion-Resistant Dynamic Spectrum Allocation,”
Ji and Liu use multi-stage dynamic games to model
the spectrum allocation in wireless networks with
multiple selfish legacy spectrum holders
and unlicensed users; they propose a pricing-based
collusionresistant approach to optimize overall
spectrum efficiency, while not only keeping the
participating incentives of the selfish users but
also combating possible user collusion.

In “Competitive Pricing for Spectrum Sharing in
Cognitive Radio Networks: Dynamic Game,
Inefficiency of Nash Equilibrium, and Collusion,”
Niyato and Hossain study the problem of spectrum
pricing in a cognitive radio network where
multiple primary service providers compete with
each other to offer spectrum access opportunities
to the secondary users; they use Bertrand game
model to analyze the impacts of several system
parameters such as spectrum substitutability and
channel quality on the Nash equilibrium.

In “Spectrum Leasing to Cooperating Secondary ad
hoc Networks’, Simeone, Stanojev, Savazzi,
Bar-Ness, Spagnolini,and R. Pickholtz consider the scenario that a
primary link has the possibility to lease the
owned spectrum to an ad hoc network of secondary
nodes in exchange for cooperation in the form of
distributed space-time coding; they formulate
the investigated model in the framework of
Stackelberg games.

In closing, we would like to thank all of the authors
who have submitted papers to this Special Issue
and the reviewers who helped evaluate the
submissions. We would also like to express our
gratitude to Laurel Greenidge, Pamela
Cosman, Marlene Sealey-Frey and Sue Lange, who
have provided significant help and support
throughout the whole process. Finally, we hope the
contents of this Special Issue will inspire the
readers to investigate many of the challenging problems
in this emerging field.

PS: Above this
paper, now the CR's research is include spectrum sensing, physical
layer, MAC design, spectrum sharing and cognitive networking and
applications of game theory. I should study deeply and find some
interested aspects of CR. Then I can do some reaserch by
meself.