International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013
Spectrum Sharing In Cognitive Radio
Networks
[1]
Varaka Uday Kanth, [2] Kolli Ravi Chandra ,
[3]
[1],[2]
[3]
Rayala Ravi Kumar
Associate professor,Dept.of ECE KLUniversity
B.tech Final Year Students (ECE) ,KL University, Vaddeswaram, Andhra Pradesh, India.
II.
Abstract: According to Federal Communication
Commission (FCC), more than 70% of the available
spectrum is not utilized optimally. Cognitive radio is
a better technique to fulfill the utilization of radio
frequency spectrum. Both licensed and unlicensed
users can use the frequency spectrum using cognitive
radio technique. Licensed users are the primary users
and unlicensed users are the secondary users.
Secondary user requests the primary user for some
amount of spectrum. Primary user allocates the
spectrum to the secondary users by itself without
degrading its own performance using spectrum
sharing techniques. This paper deals with different
types of spectrum sharing techniques.
FEATURES OF COGNITIVE RADIO
1. Cognitive capability: Using this feature the
cognitive radio dynamically scans the whole
spectrum and finds portion for its transmission.
Spectrum sensing, spectrum management and
spectrum sharing are the components of the
cognitive capability.
2. Reconfigurability: It is the parameter adjustment
capability without any modification in the
hardware components. The parameters are
Operating frequency, Modulation and Transmission
power etc.
III.
Keywords: Cognitive radio, Primary user,
FUNCTIONAL BLOCKS OF
COGNITIVE RADIO
Secondary user, Licensed user.
I.
INTRODUCTION
The software defined radio and the cognitive radio
both are introduced to improve the efficiency of
spectrum usage. Software radio has a
programmable software platform for wireless radio
transceiver. The radio receiver in the software radio
operates at multiple frequency bands by using
multiple transmission protocols. Cognitive radio is
the extension of the software radio. Cognitive radio
changes its transmission parameters and
intelligently adapt to the wireless environment.
Using this ability of cognitive radio spectrum can
be shared between primary and secondary user. The
performance of the primary user should not be
degrading by the opportunistic behavior of the
secondary user, so we use the dynamic spectrum
sharing mechanism.
Cognitive radios are basically two types. One is full
cognitive radio in which every possible parameter
observable by a wireless network is considered and
the other one is the spectrum-sensing cognitive
radio in which only radio frequency spectrum is
considered.
ISSN: 2231-5381
Cognitive radio includes five main functional
blocks: spectrum sensing, spectrum management,
spectrum sharing, spectrum mobility and
transmitter-receiver handshake.
1. Spectrum sensing aims to determine spectrum
availability and the presence of the licensed users
(Primary users), a secondary user can only allocate
to a portion of the spectrum if that portion is not
used by a secondary user.
2. Spectrum management predicts how long the
spectrum holes are available for use to the
unlicensed user (secondary user).
3. Spectrum sharing is to distribute the spectrum
among the secondary users according to the usage
cost.
4. Spectrum mobility is used to maintain seamless
communication during the transition to better
spectrum. if the portion of spectrum which is in use
is required by the primary user the communication
needs to be done in another portion, so spectrum
mobility is required for the cognitive radio.
5. Once a portion of the spectrum is allocated for
the communication, the receiver of the
communication should also know about the
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International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013
indicated spectrum. Hence a protocol known as
transmitter-receiver handshake protocol is required
for the communication between the cognitive radio
nodes.
IV.
SPECTRUM SHARING
ASPECTS&TECHNIQUES
The main challenge after detecting the available
spectrum is to access or share the spectrum among
the secondary users of the cognitive radio. The
solutions for spectrum sharing in cognitive radio
networks can be mainly classified in three aspects
a)
Architecture Assumption
b) Spectrum Allocation Behaviour
c)
Spectrum Access Technique
The first spectrum sharing technique in the
cognitive radio is based on the architecture, which
is of two types; more specifically spectrum access
can be centralized and distributed as explained
below
1. Centralized spectrum sharing: In this solution, a
centralized entity controls the spectrum allocation
and access procedures. Each entity in the cognitive
radio network forwards the measurements of the
spectrum allocation to the centralized entity. Using
these measurements, the centralized entity
constructs the spectrum allocation map
2. Distributed spectrum sharing: the distributed
spectrum sharing is used where the construction of
an infrastructure is not necessary. In this case there
is no presence of the centralized entity, each and
every node is responsible for the spectrum
allocation and access is based on local policies
The second classification for spectrum sharing
techniques in cognitive radio networks is based on
the access behavior, which is of two types:
1. Cooperative spectrum sharing: cooperative
spectrum sharing is also called as the collaborative
spectrum sharing. it considers the effect of the
node’s communication on other nodes, in this case
the interference measurements of each and every
node shared among the other nodes. All the
centralized spectrum sharing solutions are
considered as the cooperative spectrum sharing.
2. Non-cooperative spectrum sharing: this is also
called as the non collaborative spectrum sharing
(selfish) solution; it considers only the node at
hand. The nodes will not share the measurements to
the other nodes, so it is referred as the selfish
ISSN: 2231-5381
solution. By using this method, spectrum utilization
can be reduced.
Both cooperative and non-cooperative solutions are
compared through their fairness, spectrum
utilization and throughput, both the approaches are
considered such the cooperative approaches also
consider the effect of the channel allocation on the
potential neighbors. The results show that
cooperative spectrum sharing outperforms the non
cooperative spectrum sharing.
Coming to the comparison of the centralized and
distributed spectrum sharing, the distributed
spectrum sharing closely follows the centralized
spectrum sharing. But, this is not always valid in
the cognitive radio networks.
To exploit the performance of the cognitive radio
spectrum access solutions game theory was
proposed, game theory is exploited to analyze the
behavior of the cognitive radio for distributed
adaptive channel allocation. The comparision
between the cooperative and non cooperative
spectrum sharing techniques has been presented
using the game theory
The evaluations reveal that Nash equilibrium point
for cooperative users is reached quickly and results
in a certain degree of fairness as well as improved
throughput, more over fairness and spectrum
utilization are degraded by using the non
cooperative spectrum sharing. The communication
and information exchange required by selfish users
is very low.
The third classification in the spectrum sharing of
the cognitive radio is based on the access
technique; these are two types as explained below
1. Overlay spectrum sharing: overlay spectrum
sharing is one of the spectrum access techniques. In
this method, the node accesses the network using a
spectrum hole which is not used by the primary
user (licensed user), so that the interference to the
primary user is reduced.
2. Underlay spectrum sharing: in the underlay
spectrum sharing the node accesses the networks
by observing the spread spectrum techniques
developed for the cellular networks. When the
spectrum allocation map is ready, the cognitive
radio begins transmission. Due to this, at certain
position, it will interfere with the primary user and
causes interference. This solution needs increased
bandwidth compared to the overlay technique.
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International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013
Fig.1 Underlay spectrum sharing
Fig.3 Centralized-intra-network spectrum sharing
2. Centralized-inter-network spectrum sharing:
The dynamics of the centralized-inter-network is
similar to the intra network but in this case
spectrum broker shares the spectrum among the
cognitive radio users.
Fig.2 Overlay spectrum sharing
When the interference between the users is high,
the non-cooperative users are analyzed using the
game theoretical framework. As a result, when the
interference among the users is high, overlay
approach is far better than the underlay approach.
the evaluations show that the performance loss due
to the lack of cooperation is small and vanishes
with increasing signal to noise ratio(SNR).when
interference avoidance is not considered into
spectrum sharing, the underlay scheme with
interference avoidance guarantees smaller outage
probability than the pure interference avoidance.
The overlay schemes show less performance due to
imperfections at spectrum sensing and in overlay
technique node will transmit from the channel
where it is in use by the primary user. If we use the
underlay with interference avoidance, the
interference to the licensed user will be minimized.
Fig.4 Centralized-inter-network spectrum sharing
3. Distributed-intra-network spectrum sharing: In
the distributed spectrum sharing technique no
single entity makes the own sharing decision. Each
cognitive radio user in the intra-networks plays
their role in spectrum sharing process.
The existing spectrum sharing techniques are
two types namely inter network and intra network
spectrum sharing, these are the combination of the
above three classifications.
1. Centralized-intra-network spectrum sharing: In
the centralized-intra-network spectrum sharing
there exist a spectrum server and the spectrum
server coordinates all the cognitive radio users. All
users in this case exhibit the cooperative nature.
ISSN: 2231-5381
Fig.5 Distributed-intra-network spectrum sharing
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International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013
4. Distributed-inter-network spectrum sharing: In
this case also each entity involves in the spectrum
sharing decision. Each cognitive radio network
plays their role in the spectrum sharing process.
[5] Cristian Ianculescu, Andy Mudra, Cognitive
radio and dynamicspectrum sharing, in:
Proceeding of the SDR 05 Technical
Conference and Product Exposition, 2005.
[6] R. Etkin, A. Parekh, D. Tse, Spectrum sharing
forunlicensed bands, in: Proc. IEEE DySPAN
2005,November 2005, pp. 251–258.
[7] G. Marias, Spectrum scheduling and brokering
based on QoS demands of competing WISPs,
in: Proc. IEEE DySPAN2005, November 2005,
pp. 684–687.
[8] D. Maldonado, B. Lie, A. Hugine, T.W.
Fig.6 Distributed-inter-network spectrum sharing
CONCLUSION
Rondeau, C.W. Bostian, Cognitive radio
applications to dynamic spectrum allocation,
in: Proc. IEEE DySPAN 2005, November
2005, pp. 597–600.
[9] Bongkyoung Kwon, and Brandon F. Lo,
The cognitive radio networks are developed to
solve the current existing problems in the wireless
communications. Efficient spectrum sharing is very
important in the cognitive radio networks. To
enhance the utilization of the frequency spectrum
the cognitive radio should follow optimal spectrum
sharing policies. Currently, dynamic spectrum
sharing is being used in the CR networks.
Spectrum sharing is the critical issue among all the
functional blocks of the cognitive radio, so it is
necessary to know about the spectrum sharing
techniques for efficient use of the frequency
spectrum.
Student Member, IEEE “Spectrum Sharing in
Cognitive Radio Network:A centralized Intra
network Approach” School of Electrical and
Computer Engineering ,Georgia institute
ofInformation and Technology, Atlanta, GA
30332, USA.
[10] Ian F. Akyildiz, Fellow, IEEE,Won-Yeol Lee,
Student Member, IEEE, Mehmet C. Vuran,
Student Member, IEEE, and Shantidev
Mohanty, Member, IEEE “A Survey on
Spectrum Management in Cognitive Radio
Networks” Broadband & Wireless Networking
Laboratory School of Electrical & Computer
Engineering Georgia Institute of Technology,
Atlanta, GA 30332.
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