Download Primary User Protection Using MSP in Cognitive Radio Networks

ISSN: 2277 – 9043
International Journal of Advanced Research in Computer Science and Electronics Engineering (IJARCSEE)
Volume 3, Issue 3, March 2014
Primary User Protection Using MSP in Cognitive
Radio Networks
Rekha Raj. R, Reeja. R. Rajan

Abstract – Cognitive Radio Networks (CRN) provides a
promising solution to solve the scarcity of radio spectrum by the
investigation of Medium Access Control (MAC) protocols. MAC
protocols are used to sense the channels for data transmission
and are considered for the secondary users to efficiently utilize
and share the spectrum licensed by the primary user. One
important issue associated with MAC protocol design is how the
secondary users determine when and which channel they should
sense and access without causing harmful interference to the
primary user. Normal Spectrum Sensing (NSS) is used at the
beginning of each frame to determine whether the channel is
idle. Then the secondary users employ CSMA for channel
contention on detecting the available transmission opportunity.
Fast Spectrum Sensing (FSS) is inserted after channel
contention to promptly detect the return of the primary users. So
the primary users can benefit from more protection by using
FSS. In addition, this work investigates how the performance of
the proposed protocol will be if there are different Selfish Attacks
and Detection in Cognitive Radio Networks. CRN have several
intrinsic security threats due to the opportunistic exploitation of
the bandwidth in cognitive radio network. In particular,
jamming is one of the most challenging security threats for
Cognitive Radio Networks. So in this proposed work Intrusion
Detection Systems are used for combating these threats against
Cognitive Radio Networks.
Keywords-cognitive radio networks, MAC protocol, fast
spectrum sensing (FSS), Jamming attack, intrusion Detection
system (IDS)
I. INTRODUCTION
In the recent years the scarcity of spectral resources while
most of the allocated spectrum is underutilized. What may
look like a paradox it is only the waste of spectral resources.
Most of the useful spectrum is allocated to licensed users (e.g.
mobile carriers, TV broadcasting companies) that do not
transmit at all the geographical locations all the time. If this
spectrum is opened for unlicensed use (e.g. private users,
short range networks ...) then a vast array of new services will
Manuscript received March, 2014.
Rekha Raj. R, Department of Computer Science and Engineering,
Jawaharlal College of engineering and Technology, Palakkad, India, Mobile
No. +919633215100
Reeja. R. Rajan, Department of Computer Science and Engineering,
Jawaharlal College of Engineering and Technology, Palakkad, India,
Mobile No. +919846387054
appear in the network. For example the huge innovation that
has occurred in WiFi and Bluetooth operating in unlicensed
bands, even though these two standards share just scraps of
undesirable spectrum with many other technologies.
However, before opening the licensed spectrum to new users
in a Dynamic Spectrum Access (DSA), it is necessary to
guarantee the primary users; they are having the rights over
these bands, that they will not be interfered.
For future communication and networking Cognitive
radio networks (CRNs) are one of the enabling technologies.
In order to improve and optimize the radio electromagnetic
spectrum CRNs have been developed. A cognitive radio
system is a 'smart' network that can observe, learn from, and
adjust to changing environment conditions. CRNs’ users can
be divided into two classes: primary users-they are the license
holders of the radio spectrum; and, secondary users-they are
allowed for using the temporarily unused licensed spectrum.
Whenever the primary users directly access the radio
channel, secondary users must carefully monitor the
spectrum availability to hold unused portion of it. There by
avoiding
any
interference
on
primary
users’
communications. To secure this goal, secondary users
perform a continuous spectrum sensing and analysis, and
when they find a “spectrum hole”, they tune their radios in
order to perform the communication in the available
spectrum. Therefore, secondary users opportunistically
access the free spectrum bands when they are free, while
releasing them back when needed by primary users. In order
to achieve this, secondary users are asked to continuously
sense the radio environment Figure 1 shows a typical CRN
spectrum utilization: primary users are the license holders,
and therefore, they directly access the wireless spectrum;
nevertheless, for large time spans, the frequency bands are
not used, and they might be accessed by secondary users with
an opportunistic behavior, i.e., using a free frequency band
till no primary users Requests it, and jumping to a new
unused frequency band as soon as a primary user intends to
access the band in use. Thus A common assumption in
cognitive radio systems is that the licensed users which are
having the spectrum rights are unaware of the presence of
secondary users. Hence the burden of interference
management relies mainly on the secondary system. In
particular, either there is a maximum interference level that
133
All Rights Reserved © 2014 IJARCSEE
ISSN: 2277 – 9043
International Journal of Advanced Research in Computer Science and Electronics Engineering (IJARCSEE)
Volume 3, Issue 3, March 2014
the primary system is willing to tolerate, and the secondary
powers/activity are to be adjusted within this constraint,
A. CRN architecture
hence both primary and secondary users transmit in the same
The CRN system model is depicted in Fig. 2. For easiness,
band, or secondary users are allowed to opportunistically
the
figure contains only one television broadcasting tower
access the spectrum on the basis of no-interference to the
primary (licensed) users. These two paradigms referring to whereas multiple broadcasting towers may also be present.
the fact that secondary users need to fulfill the constraints The television companies have license to broadcast their
programs through the reserved band of the 54 to 806 MHz, so
imposed by the primary user.
One challenge faced by coexisting cognitive radio the television companies (along with their subscribers)
networks is how to reduce the internetwork media contention formulate the “primary users” of the system. On the other
(with primary user using spectrum sensing) and intranetwork hand, the IEEE 802.22 WRAN (Wireless Regional Area
contention (with other secondary users via, e.g., CSMA/CA Network) specification allows a number of “cells” and each
mechanism). The design of the optimal sensing-transmission of the cells are managed by a base station (BS). The WRAN
strategies on a single channel is investigated under imperfect cells form our considered CRN. The service coverage radius
sensing, where the total collision probability is restricted to of each of the WRAN cells featuring collocated CRNs varies
satisfy the protection required by the primary user. So the from 33 to 100km. Each CRN can support a number of
joint consideration of both MAC-layer sensing and channel “secondary users,” who may access the unused spaces of the
contention access has been introduced. The usual method, spectrum, which is usually reserved for the television
namely Opportunistic Spectrum Access-MAC or OSA-MAC companies, i.e. the primary users.
in short, which allows the secondary users to perform
channel contention before spectrum sensing and that may
result in contending unavailable channel and wasting system
resource. Another method is that spectrum sensing is carried
out at the beginning of each frame to detect the presence of
the primary user followed by channel contention. This will
benefit from the up-to-date sensing information. Due to the
random arrival of the primary packet, the primary user will
transmit without sensing and contention whenever it
becomes active. This may results in severe interference
between primary and secondary users, whenever a secondary
user gains the channel access and attempts to transmit its
packet in this busy scheme.
Radio spectrum use
100%
80%
Spectrum
currently
occupied by
primary users
60%
40%
20%
0%
t1
t2
t3
t4
White space for
secondary users
access
Time
Fig 1. Spectrum management in CRNs: Secondary users
exploit frequency bands left from primary users in order to
communicate.
Fig 2. Considered CRN architecture illustrating how the
licensed band with white spaces can be shared by the
secondary users.
134
All Rights Reserved © 2013 IJARCSEE
ISSN: 2277 – 9043
International Journal of Advanced Research in Computer Science and Electronics Engineering (IJARCSEE)
Volume 3, Issue 3, March 2014
available, intranetwork contention takes place where
These unused spaces of the spectrum might occur due to cognitive users compete for channel access.
different scenarios, e.g. when the television broadcast is
offline/ idle. The unused portions of the spectrum are referred
B. Carrier Sense Multiple Access (CSMA)
to as “white spaces.” Each secondary user is equipped with
software radio to sense whether the primary users are
On a half-duplex Ethernet network, multiple nodes share a
currently occupying a channel or not. If the channel is single transmission medium. A MAC protocol is used to
occupied, the secondary user has the ability to adapt his radio allow the nodes to gain access to the shared transmission
to another channel in order to sense the white spaces of that medium and to ensure error-free data transfer. CSMA/CD is
channel.
the MAC protocol used on half-duplex Ethernet networks. It
II. MAC SENSING-TRANSMISSION PROTOCOL manages the access to the shared transmission medium and
DESIGN
prevents multiple nodes from transmitting frames
This section deals with the design of MAC simultaneously. Before transmitting a packet, the cognitive
sensing-transmission protocol. As shown in Fig. 3, each user is required to monitor the channel to avoid collision with
cognitive user operates on a frame-by-frame basis, with each packets being transmitted by other cognitive users. If two or
frame of duration T. The cognitive user first senses the more nodes simultaneously transmit frames, CSMA/CD
channel for a duration TN. Then CSMA is invoked to contend ensures that the frames are detected and retransmitted.
To ensure reliable frame transfer, CSMA/CD follows a
for channel access, whenever the channel is declared idle.
sequence
of steps. The first step for transmitting a frame by
Thereafter, the return of the primary user is detected by
performing FSS. The secondary users can use the idle using CSMA/CD is carrier sensing or listen before talking. A
channel for data transmission, if no active primary user is node that has to transmit a frame monitors the transmission
detected. This protocol design overcomes the limitations of medium to detect whether the medium is free. The node does
OSA-MAC that allows channel contention before spectrum this by sensing a carrier on the medium. A carrier is a specific
sensing by the contention of unavailable channel. Moreover, level of voltage used to transmit a frame. The presence of a
it will improve the efficiency of MAC protocols. The channel carrier on the transmission medium indicates that the
may become busy anytime due to the random arrival of the medium is being used. If a carrier is detected, the
primary user in the network. FSS can avoid causing major transmission is deferred until the carrier ceases and the
interference to the primary user. The detailed design of the transmission medium is free. The node continues to monitor
proposed MAC sensing-transmission protocol is described as the transmission medium until the carrier ceases.
However, if the node does not detect a carrier, it indicates
follows.
that the transmission medium is free. The node can then
transmit the frame. The node begins the transmission after
waiting for a minimum period of time known as an Inter
Frame Gap (IFG). At any specific point in time, multiple
nodes may sense a carrier on the transmission medium. At
times, more than one node may simultaneously determine
that the transmission medium is free and begin to transmit
frames.
In a situation where two or more nodes simultaneously
transmit frames a collision occurs. A collision corrupts the
frames that are transmitted together. To detect a collision, the
node that has initiated a transmission needs to monitor the
transmission medium for a possible collision. This process is
Fig. 3. The frame structure of cognitive user
known as listen while talking. During the process of listen
while talking, the transmission is complete if a collision is
A. Normal Spectrum Sensing (NSS)
not detected. However, if a collision is detected, the node
stops the transmission of the frame. This process is known as
NSS is carried out at the beginning of each frame. collision detection. After stopping the transmission of the
Efficient detection and identification of the availability of the frame, the node sends a collision enforcement jam signal to
primary channel which can be accessed by the cognitive user the other nodes on the network. When the other nodes receive
is focused in NSS. If the channel is indicated as occupied by the jam signal, they discard the frames that are corrupted by
the primary user, then the secondary user will keep silent the collision. After sending the jam signal, the nodes
until the next frame. On the other hand, if the channel is
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All Rights Reserved © 2014 IJARCSEE
ISSN: 2277 – 9043
International Journal of Advanced Research in Computer Science and Electronics Engineering (IJARCSEE)
Volume 3, Issue 3, March 2014
involved in the collision wait for an indefinite period of time
before retransmitting the frames. This process in which the
III. SECURITY THREATS AGAINST CRN
nodes wait before transmitting frames is known as backoff.
The backoff period is determined by a random number
In fact, CRNs suffer both traditional wireless security
generated by a collision counter located on each node. After a issues, as well as specific threats: many attacks have been
backoff, the nodes involved in the collision try to transmit recently introduced in order to prevent secondary users from
data again. This may cause repeated collisions. The accessing available spectrum slots. One of the most
possibility of repeated collisions is reduced if each node challenging security threat in CRNs is jamming, i.e.,
backs off for a different period of time. The value of the malicious signal transmissions. Jamming has been
backoff period is cumulative until a node retransmits a frame introduced in military scenarios to prevent an adversary from
without a collision.
communicating. The two principal goals of jamming in
Finally, the last step in the process of transmitting a frame CRNs are avoiding all the communications of primary and
by using CSMA/CD is retransmitting the frame that is secondary users, or preventing only secondary users from
corrupted because of a collision. This step is performed after accessing the free spectrum bands. The former goal is a
a collision is detected, and the node backs off for a period of general problem of standard wireless communications; while
time. If the retransmission is successful, the node clears its the latter one is specific to CRNs. In fact, recalling Fig. 1,
collision counter
consider several secondary users might compete to gain the
free spectrum access. A malicious secondary user could aim
C. Fast Spectrum Sensing (FSS)
at increasing the chances to use the free spectrum by
disrupting the other secondary users’ communications.
FSS is introduced as a preliminary step before NSS. The
The attack taxonomy presented in [4] classifies these
aim of FSS is to quickly determining whether a subsequent threats based on the layer in which they are carried out. The
spectrum sensing is required in a network. FSS is performed transport layer threats usually disrupt the transport control
before the cognitive user attempts to transmit packet during protocol (TCP). An example of this attack is “Lion” attack.
the channel contention phase whenever its backoff counter Sinkhole and HELLO flood attacks are the network layer
reaches to zero. The primary packet may arrive at any attacks against CRN. The link layer attacks comprise
instant, and be transmitted without sensing and contention; spectrum sensing data falsification and a denial of service
therefore the channel may become busy again, and need to be (DoS) attack by saturating the control channel of the CRN.
completely used by the primary user. Thus spectrum sensing Meanwhile, the physical layer attacks against CRNs consist
is required to be carried out frequently to protect the primary of primary user emulation (PUE) attack, objective function
user. Due to the random value of Tc, Tc may be very large, attack, and the jamming attack and physical layer attacks are
such that the return of the primary user will occur with high more challenging to deal with.
probability. Thus, it is necessary to perform FSS with
duration TF < TN after the channel contention phase.
A. Primary User Emulation (PUE) attack
The FSS is provided with threefold purpose. First purpose
is to declare the channel busy if any misdetection happens in
NSS. Second is to quickly detect the return of the primary
user after the Tc period. The secondary user will utilize the
available channel to transmit its packet, if the channel is still
declared idle in FSS and it can also prevent the secondary
user from transmitting on busy channel due to the return of
primary user after Tc. Third, if the channel is declared as
busy, then the backoff counter is reaches to frozen at a special
stage for a duration which is equal to the ON period of the
primary packet, TON; then keeps sensing until the channel is
declared idle. FSS is a continuous sensing strategy. If the
secondary user senses the channel as busy, it will leave the
channel for TON duration, and then keeps sensing until the
channel is declared idle due to its short sensing time.
Therefore, the remaining available transmission opportunity
can be utilized by the secondary user. This will results in a
more effective utilization of the available channel.
In this attack, competitive secondary user aims at
preventing authorized secondary users from using the white
spaces in the spectrum. For example, the competitor may
exploit the “quiet periods” of the CRN during which no
secondary user should transmit in order to facilitate spectrum
sensing. If the competitor transmits during the quiet period,
then the other authorized users will back off by considering
that a primary user (i.e. the competitor) is accessing the
spectrum. There is realistic possibility of PUE attacks since
CRs are highly reconfigurable. There are a number of other
techniques by which the adversary may pretend to be a
primary user and trick the authorized secondary users.
B. Objective function attack
Cognitive radio is capable of sensing the spectral
environment. CRN learns from previous history, and making
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ISSN: 2277 – 9043
International Journal of Advanced Research in Computer Science and Electronics Engineering (IJARCSEE)
Volume 3, Issue 3, March 2014
smart decisions for adjusting its transmission parameters flow, primary user access time, packet delivery ratio (PDR),
based on the current environmental conditions.
signal strength (SS), and so forth. To make it clear, an
By solving objective functions these parameters are example of a physical layer attack, i.e. the jamming attack, is
computed by the cognitive engine. Consider a simple considered. In order to identify the jamming attack, consider
objective function to find the radio parameters, which a simple observation made by a secondary user involving its
balance the data rate and security. Assume the impact when PDR and SS. The PDR of a user indicates the ratio of the
an intelligent malicious attacker performs a jamming attack number of packets received by the user to that of the packets
every time an authorized secondary user attempts to transmit sent to him. This is an example case of the IDS learning
data with high security. So this makes the authorized phase (which arises from a specific jamming attack against
secondary user’s cognitive engine to experience that the the CRN), but IDS is not limited to learning this feature only.
network conditions are unfavourable for secure transmission. If the IDS is designed appropriately by taking into
As a result, the user drops his security level and transmits consideration the CRN system specifications, wireless
data with low/no security. Thus, the malicious attacker forces protocol behaviour, and so on, it can learn various modes of
the victim radio to use a low security level, which can be operation of the CRN. The acquired information can smooth
eavesdropped or hacked.
the detection phase of the IDS to discover unknown
intrusions or attacks against the targeted CRN.
C. Jamming attack
B. Detection Phase
Jamming attack is one of the most difficult security threats
The IDS detection phase is based on finding the point of
in CRNs. A jamming attacker may transmit continuous
change
in the CRN operation as quickly as possible under an
packets to force an authorized secondary user to never sense
an idle channel. This leads to a DoS type attack whereby the attack. First, consider a physical layer jamming attack as
follows. When a malicious user jams a secondary user’s
legitimate user is unable to access any white space.
connection, the following observations can be made. While
the SS measured at that secondary user remains high, his
IV. IDS FOR DETECTING THREATS
PDR usually drops.
Intrusion detection system (IDS) is effective to quickly
detect whether the secondary user are being attacked. Usually Algorithm: PDRSS_Detect_Jam
the IDSs follow either mis-use or anomaly based attack { PDR(N) : N € Neighbors} = Measure_PDR()
detection methods. The mis-use based detection method uses MaxPDR = max{ PDR(N) : N € Neighbors}
signatures of already known attacks. But, the mis-use based if MaxPDR < PDRThresh then
SS = Sample_Signal_Strength()
approach cannot find new types of attacks effectively. On the
CCheck = SS_ConsistencyCheck(MaxPDR, SS)
other hand, as its name suggests, the anomaly based
if CCheck == False then
detection methodology relies on finding the “anomaly”,
post NodeIsJammed ()
which represents an abnormal mode of operation in the
end
system. It may be possible to detect new attacks- which
generate some abnormal change in the CRN by designing an end
appropriate anomaly based intrusion/attack detection system.
This is the reason why it is better to use the anomaly-based Algorithm 1: Jamming detection algorithm that checks the
intrusion detection technique in the IDS for identifying consistency of PDR measurements with observed signal
attacks in CRNs. In CRN, single centralized IDS may not be strength.
able to detect a malicious attack and notify the secondary
This happens only because the secondary user never
users quickly enough. Therefore it is important to facilitate
lightweight yet effective IDSs in the secondary users’ receives some/all of the packets sent to him. Our point of
themselves.ie, each secondary user is assumed to have an interest is how to detect the change point in the PDR
IDS. The IDS operates in two steps, namely the learning or behaviour of a secondary user (targeted by a jamming
attacker). In other words, how can the IDS find when the
profiling phase and the detection phase.
PDR of the secondary user is dropping significantly enough
to reflect the impact of a jamming attack? In the following,
A. Learning Phase
the proposed IDS with anomaly detection is presented to deal
To effectively detect anomalies due to various types of with this issue.
attacks, the IDS needs to be designed in such a fashion that it
may learn the normal behaviour of protocol operation, traffic
137
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ISSN: 2277 – 9043
International Journal of Advanced Research in Computer Science and Electronics Engineering (IJARCSEE)
Volume 3, Issue 3, March 2014
Based on these observations this work proposes the
detection protocol shown in Algorithm 1. In the
PDRSS_Detect_Jam algorithm, a wireless node will declare
that it is not jammed if at least one of its neighbors has a high
PDR value. However, if the PDRs of all the neighbors are
low, then the node may or may not be jammed and we need to
further differentiate the possibilities by measuring the
ambient signal strength. Rather than continually sample the
ambient
signal
levels,
the
function
Sample_Signal_Strength() instead reactively measures the
signal strength values for a window of time after the PDR
values fall below a threshold, and the sampling returns the
maximum value of the signal strengths, which is denoted as
SS. The duration of the sampling window should be carefully
tuned based upon the traffic rate, the jamming model, the
Graph 1: Throughput versus Time
measuring accuracy, and the desired detection confidence
level. The function SS_ConsistencyCheck() takes as input
the maximum PDR value of all the neighbors, denoted as
MaxPDR, and the signal strength reading SS. A consistency
check is performed to see whether the low PDR values are
consistent with the signal strength measurements. If the
signal strength SS is too large to have produced the observed
MaxPDR value, then SS_ConsistencyCheck() returns False,
else it returns True.
V. EXPERIMENTAL RESULTS
The proposed work Protection to Primary User using MSP
in Cognitive Radio Networks by using NS2 in a personal
computer running Microsoft Fedora13 with the
specifications such as Pentium IV 1.13 GHz, hard disk of 40
GB and Cache memory of 512 MB. Simulated results are
analysed by using graph. Graph can be implemented on the
basis of packet delivery ratio, throughput and channel
contention.
Throughput versus time is shown in graph1.The
throughput is the rate of successful message delivery over a
communication channel. This data may be delivered over a
physical or logical link, or pass through a certain network
node. As the time increases there is a gradual increase in the
throughput. After 50secs maximum sustained throughput is
obtained.
The graph 2 plots packet delivery ratio (PDR) in
Y-direction versus time in X-direction.
PDR illustrates the ratio of number of delivered data
packets to the destination .
Graph 2: Packet Delivery Ratio versus Time
It can be calculated by dividing the numbers of packet
receive to the number of packet send. The greater value of
packet delivery ratio means the better performance of the
protocol. i.e., if the value of PDR is less than one, then there
may be a chance of malicious attack and if the value of PDR
is equal to one, then there is no attacks happen.
The graph 3 illustrates the relationship between channel
contention and time. Normal spectrum sensing is carried out
during the time interval between 0-10 sec. 20 sec onwards
there will be high channel sensing and channel access takes
place. At an interval 40 sec the graph measures a peak
increase in the channel contention. After the 50 sec the graph
shows no channel access.
138
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ISSN: 2277 – 9043
International Journal of Advanced Research in Computer Science and Electronics Engineering (IJARCSEE)
Volume 3, Issue 3, March 2014
[2] Intrusion Detection System (IDS) for Combating Attacks Against Cognitive
Radio Networks Fadlullah, Z.M. , Nishiyama, H. , Kato, N., and Fouda, M.M.
Network, IEEE Volume:2 , Issue: 3, June 2013.
[3] Jamming Mitigation in Cognitive Radio Networks Di Pietro, R. ; Univ. of
Roma Tre, Rome, Italy ; Oligeri, G. Network, IEEE ,Volume:27, Issue: 3, 07
June 2013.
[4] Survey of Security Issues in Cognitive Radio Networks W. El-Hajj, H. Safa,
and M. Guizani, J. Internet Technology (JIT), vol. 12, no. 2, Mar. 2011, pp.
181–98.
Rekha Raj. R received her BTECH Degree
in Information Technology from SHM
Engineering College, which is affiliated to
Kerala University, Thiruvananthapuram,
Kerala. Now currently pursuing her Final
Year Masters of Engineering in Computer
Science
and
Engineering
from
Jawaharlal College of Engineering and
Technology, which is affiliated to University
of Calicut, Calicut, Kerala. Her area of
Interest is Computer Networks and cloud
computing.
Graph 3: Channel Contention versus Time.
VI. CONCLUSION AND FUTURE WORK
In this work, we study the design of MAC sensing
transmission protocol that inserts FSS after the channel
contention phase. For a real environment, the primary user
packet may arrive at any time, and utilizes the channel
without sensing and contention due to its higher priority.
Thus, the channel will become busy after the contention
phase. Therefore, inserting Fast Spectrum Sensing into the
MAC protocol design has significant impact in reducing the
collision probability and improving the primary user
protection. In addition, this work analyses several security
threats occurs in CRN due to the mis use of the bandwidth in
cognitive radio network. Specifically, jamming is one of the
challenging security threats for Cognitive Radio Networks.
This work also highlighted the importance of designing
appropriate intrusion detection systems to combat attacks
against cognitive radio networks. Also, we proposed simple
yet effective IDS, which can be easily implemented in the
secondary users. Our proposed IDS uses a Jamming detection
algorithm, which offers anomaly detection. Simulation
results clearly show the effectiveness of the proposed MAC
sensing-transmission protocol with FSS. In the future, our
work will perform further investigations of how to enhance
the detection sensitivity of the IDS.
Reeja. R. Rajan received her BTECH
Degree in Information Technology from
University of Calicut, Kerala and MTECH
Degree in Embedded System from Anna
University, Chennai. She is currently working
as an Assistant Professor in the Department of
Computer Science and Engineering at
Jawaharlal College of Engineering and
Technology, which is affiliated to university of
Calicut. Her area of Interest is Embedded
System, Data Mining, Data Compression and
Computer Networks.
REFERENCES
[1] A MAC Sensing Protocol Design for Data Transmission with More
Protection to Primary Users Wenjie Zhang, Chai Kiat Yeo, and Yifan Li , IEEE
Transactions On Mobile Computing, Vol. 12, No. 4, April 2013.
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