ALLOCATION OF POWER IN RELAY NETWORKS FOR SECURED COMMUNICATION

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International Journal of Advanced Research in Engineering and Technology
(IJARET)
Volume 6, Issue 8, Aug 2015, pp. 135-144, Article ID: IJARET_06_08_012
Available online at
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ISSN Print: 0976-6480 and ISSN Online: 0976-6499
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___________________________________________________________________________
ALLOCATION OF POWER IN RELAY
NETWORKS FOR SECURED
COMMUNICATION
R. Revathi
Assistant Professor, ECE Department,
Sri Aravindhar Engineering College, Pondicherry
S. Sinthuja
AMET University, Chennai
Dr. N. Manoharan
Research Director, AMET University, Chennai, India
N. Rajendiran
Assistant Professor, Dept. of EEE, Bharath University, Chennai, India
ABSTRACT
Secured communications in the presence of eavesdropper node is grave for the
successful operations in the wireless relay networks. In the proposed work,
choose two hop wireless relay networks to enhance security against the
eavesdropper node. This paper considers four node networks, they are one
source, and three decode and forward relay, one destination and one
eavesdropper node. To transmit the information from source to relay node,
eavesdropper interrupt and try to capture that relay node messages. To
prevent the eavesdropper interception, destination sends artificial jamming
noise to the relay node. This jamming noise has the ability to jam the
eavesdropper node. According to the channel state information present at the
destination, the four types of jamming power allocation methods are
introduced; (i) Fixed jamming power allocation, (ii) Rate optimal power
allocation, (iii) Outage optimal power allocation, (iv) Statistical optimal
power allocation method. The maximum achievable data rate at the
destination is also estimated.
Key words: Artificial Jamming Noise, Cooperative Communication, Decode
and Forward Relay, Optimal Power Allocation Scheme, Physical Layer
Security.

R. Revathi, S. Sinthuja, Dr.N.Manoharan and N.Rajendiran
Cite this Article: R. Revathi, S. Sinthuja, Dr.N.Manoharan and N.Rajendiran,
Allocation of Power In Relay Networks For Secured Communication.
International Journal of Advanced Research in Engineering and Technology,
6(8), 2015, pp. 135-144.
http://www.iaeme.com/IJARET/issues.asp?JType=IJARET&VType=6&IType=8
1. INTRODUCTION
Security plays an essential role in numerous wireless relay network applications. Due
to broadcast the messages through a wireless medium, receiving secured information
at the destination node in presence of possible eavesdroppers is of increasing
importance. A relay network is performed well means to satisfy the conditions of
higher reliability, higher data rate and a secured communication system. Wireless
relay network is used to help increase the rate of communication between the
transmitter and the receiver. The motivation of these relay networks is to provide
secure data access with anytime and anywhere. When implement the wireless devices,
power consumption have taken an important role. Therefore, power allocation is one
of the important issues in wireless communication technology, to overcome this
problem by using various power allocation methods. Wireless information theoretic
security was proposed in [1]. This paper considers a two channels are main channel
and wireless wiretap channel.
This encryption method provides the less security in a network. Collaborative
relay beam forming with perfect CSI Optimum and distributed implementation was
proposed in [2]. The optimal power allocation at the relays has been analyzed in
different strategies are partial CSI allocation, full CSI allocation and eavesdropper
node CSI allocation.
Secure wireless communication via cooperation was proposed in [3]. In an
optimal beam forming scheme is used to minimize the jamming power consumption
and also maintain a maximum secured communication in a relay network.
Cooperative communications based decode and forward relay is considered here.
Outage probability based power distribution between data and artificial noise for
physical layer security was proposed in [4]. It provides the security in physical layer,
communicating with many sources, one relay and one destination node was performed
here. Consider two types of broadcasting strategies are spatial beam forming and
noise forwarding techniques. This technique is used to minimize the outage
probability in the network and also improve the quality of service at the destination
node.
Consider the two beam forming techniques are optimal beam forming and robust
beam forming design was discussed in [5]. Optimal beam forming is performed well
in the presence of perfect CSI, and it is used iterative algorithm to obtain the
maximum secrecy rate. Robust beam forming schemes are investigated, when the
imperfect CSI is present at the node. The two hop wireless relay networks of half
duplex communication with different optimal power allocation schemes under the
Rayleigh fading channel was investigated in [6]-[8]. Here single relay is used, which
acts as an Amplify and forward relay protocol manner. Consider an Amplify and
forward relay strategies, to amplify the communication data and forwarded to the
destination. To maintain a secure communication against the eavesdropper node, relay
transmits the code words to confuse the eavesdropper node. The outage probability
and ergodic capacity was investigated in [9]. The partial band allocation provides the
less secrecy rate when the outage probability achieved the level of zero.

Allocation of Power In Relay Networks For Secured Communication
Flat fading half duplex system is considered where multiple input and multiple
output pairs communicate with the help of an Amplify and forward relay was
investigated in [10]. In a channel state information available at the destination, to
transmit the more number of data streams based on the linear precoding schemes
through a conventional relay system. A cooperative communication network consists
of a one source, one relay node and multiple eavesdropper system was discussed in
[11]. Cooperative networks are used to transmit the intended noise to the jammer
node. Here node cooperation is developed for achieving security in a relay network.
Jamming techniques which generate an intended interference at the imperfect user
node in order to diminish the outage probability of the related link appear to be a
motivating approach for practical applications [12]. Optimal power allocation for
recuperating the amplify-and-forward relaying network is proposed in [15]. Secure
communications via cooperating base stations was proposed. An addition of the work
offered in [16] for cooperative ad-hoc environments with jamming. [14] In difference,
where only one relay node is preferred to pledge security, here the problem
considered involves the selection of a relay and a jammer node.
The objective of this paper is discussed below.
 Minimizing the optimal jamming power with a fixed objective secrecy rate.
 Maximizing the secrecy rate with convinced power constraints.
 To find the excellent optimal power allocation by utilizing the method of JPA.
In our proposed work, we consider a two hop wireless relay networks in the
occurrence of an imperfect channel user with multiple decode-and-forward relaying
protocol. To achieve the maximum data received at the destination, we consider a
Quadrature phase shift keying modulation technique. [15] Here different types of
jamming power allocation methods are used to achieve a maximum security level in a
network.
The remaining paper is illustrated as follows: section II describe the system model
and channel capacity, section III discusses the cooperative jamming schemes, section
IV gives the numerical results with discussions and Conclusions are drawn in section
V.
2. SYSTEM MODEL AND CHANNEL CAPACITY
Here, we discuss the system model and channel capacity of the two hop wireless relay
networks system to achieve a maximum security level in a network.
2.1. System Model
Consider a two-hop four terminal wireless relay networks system consisting of single
source node S, single destination node D, one eavesdropper node E terminal and three
decode and forward relay protocol as shown in Fig. 1. In this communication model
all nodes are assumed to be half duplex transmission. So relay cannot be transmits and
receive the information simultaneously. There is no direct communication link
between the source to destination and source to eavesdropper node. Here the relay
node transmits the source messages in a decode-and-forward fashion to the perfect
channel user node. While transmitting the messages from source to relay node, that
instant jammer intercept and try to capture that relay node messages. To avoid that
jammer node interception, the destination sends an intended noise to the relay node,
through a cooperative jamming communication. Power allocation is done for this
network using different jamming power allocation scheme in which, noise allocated to

channels are taken into account and based on that power optimization is done. Decode
and forward relay is used to transmit the information from relay to destination node.
Figure 1 Block diagram of the two hop communication model.
Maximum secrecy rate can be achieved based on the signal to noise ratio rate and
the outage probability. If the received SNR falls below a certain threshold level, that
instance outage is occurred. If the received SNR is higher than the threshold, the
receiver is assumed to have an ability to decode the received information with
negligible probability of error in a network. In between these two nodes decode and
forward relay are placed. In order to allocate transmit power to the network terminals;
we first transmit the message from source to relay terminals. The source node having
the signal , to be added with noise is given by,
(1)
Where and are the source signal and impulse response of the source node
respectively. It can be transmitted through a Rayleigh flat fading channel. Then, the
signal received by the relay node is given by,
(2)
Where are the impulse responses between the base station to decode and
forward relay node and relay to mobile station node, and are the Transmitted
power and Transmitted signal from source to relay respectively. Rayleigh flat fading
channel can be modeled as complex Gaussian random variable. Zero mean
independent and identically distributed channels are considered to be Gaussian
channel. Then the signal received by the perfect channel user is given by,
(3.)
Where is the gain of the relay node securely protecting the information at the
destination against the jammer node, relay transmit the noise to the eavesdropper
node. It can be used to maximize the interference and minimize the SNR rate to that
node. Once protection is performed destination cancels the intended noise, because
it’s having the ability to confiscate that noise. Then the signal received by the mobile
station node is given by,

(4)
Where the minus operator in the above equation is referred to as relay only
transmits if decoded correctly, otherwise it can be idle and if the source to destination
and source to relay link is strength less link means, than that performance is restricted.
The decode and forward relay provides the received signal by a factor that is inversely
proportional to the received power, which is given by,
Then the signal received by the imperfect channel user is given by,
(5)
Where , is the impulse response of the relay node to imperfect channel user
node and is considered as artificial jamming noise.
2.2. Decode and forward relay protocol
In decode-and-forward relaying protocol, while transmitting the message from
source to relay node, the received signal at the relay node, it first decoded that
received messages by using Viterbi decoding Algorithm and re encodes after it can be
forwarded to the destination. In that procedure noise is decoded at the relay node,
instead of by using amplify and forward relay protocol, it only amplifies the source
message without any decoding and encoding procedure. A Viterbi decoding
Algorithm procedure is shown in below.
Algorithm 1: Finding an decoded information Initialization:
Step 1: Set time t = 0, initial state of PM – 0, and all other PM - ∞.
Step 2: Increase time by 1, t = i+1.
Step 3: Evaluate BM for each branch,
Step 4: Compute PM[s, i+1], based on the ACS procedure
Step 5: End: map the decoded sequence, otherwise go back to step1.
A Viterbi algorithm consists of three parts they are branch metric, path metric and
trace back calculation. In a path metric calculation depends on the procedure of ACS
(Add, Compare and Select). The distance between the transmitted input pair of bits
and received pair of bits is referred as branch metric calculation.
The expression for decode-and-forward relay is given by
(6)
Where the minus operator in the above equation is referred to as relay only
transmits if decoded correctly, otherwise it can be idle and if the source to destination
and source to relay link is strength less link means, than that performance is restricted.
The decode and forward relay provides the received signal by a factor that is inversely
proportional to the received power, which is given by,
(7)

The power is transmitted from the base station node is equal to the signal
transmitted from decode and forward relay node. Here demodulation process is
performed by using Quadrature phase shift keying technique to achieve a maximum
data rate at the destination.
2.3. Channel Capacity
While transmits the message from base station to perfect channel user node, decode
and forward relay sends an intended noise signal to imperfect channel user. It will
create the interference and confuse the eavesdropper node. It can be used to make a
difference between the channel capacity of the destination and eavesdropper node
channel and also improve the secrecy rate at the system
(8)
(9)
(10)
3. COOPERATIVE JAMMING
There are many different types of jamming power allocation methods such as RJPA,
Fixed JPA, OJPA, SOJPA method etc. Optimal power allocation method Optimal
power allocation method is used to maximize the secrecy rate at the two hop wireless
relay networks. Depending on the channel state information present at the perfect
channel user node, allocating the jamming power to each node. Jamming power has
the ability to jam the imperfect channel user node. To achieve an ideal secrecy rate,
we want to maximize the interference at the imperfect channel user node, but it cannot
be affect the destination node. Always maintain the destination capacity is higher than
the illegitimate channel capacity. In Cooperative jamming, to optimize the power at
each node is important one. For case, if we allocate maximum amount of jamming
power, it’s also creates an interference at the destination node. So, the network model
cannot be achieved the higher secrecy rate. In contrast, if we allocate minimum
amount of jamming power, the imperfect channel user node can receive messages to
break through the destination node. To achieve a perfect and constant secrecy rate, the
probability of outage value cannot be achieved the level of zero.
3.1. Rate Optimal Jamming Power Allocation method
In this method, considers to use an each and every nodes of channel state information
they are decode and forward relay to jammer node, source to relay and relay to perfect
channel user node. To achieve a perfect secrecy rate and reliable communication,
maximizing the destination secrecy rate and also reduce the level of outage
probability.
(11)
(12)
Where represents the measuring parameter, that increases the destination
secrecy rate. Zero power denotes that the, at for all time probability of outage occurs

and in that cases not essential to optimize the power. RJPA method, should be meet
the four following conditions are,
1. If the decode and forward relay to perfect channel user node link is moderately
pathetic compared to the relay to jammer channel link, that cases intended noise
performing with maximum power from the destination node to the relay node.
2. For instance, if the R-D channel link moderately strapping, adjusted the power
depends on the strength of the channel.
3. When the R-D channel link is extremely strapping compared to the relay to
jammer links it cannot be adequately disgrace that jammer node and also
diminish the secrecy rate. So assume that the level of interference is maximized
at the destination node compared to the jammer node. Such a situation,
intended noise need not to be transmits at the destination.
4. Finally, the channel link is moderately strapping but not a lot, the perfect
channel user node should be send the intended noise to create the interference
and also diminish the SNR rate at the jammer node.
3.2. Outage Optimal Jamming Power Allocation method
In this method, to choose a node of channel state information for source to relay and
relay to destination links respectively. For that reason, destinations only have the
knowledge about the instantaneous channel. In this case, channel state information of
the jammer node is difficult to determine. The outage probability of secrecy rate is
given by,
(13)
Where and represents the gain of the destination and eavesdropper node,
denotes the secrecy rate. Taking inverse function of the probability of outage provides
the maximum secrecy rate at the network.
(14)
(15)
Where represents the relay gain and denotes that diminish the outage
probability. If the relay to perfect channel user node and source to relay node link of
the signal to noise ratio rate are strapping, that time only achieve an outage
probability If the relay to perfect channel user node link is moderately pathetic,
that time cannot be determine achieve an outage probability OJPA method,
diminish the outage probability level is zero. In this method destination requires
jamming power consumption at inferior rate compare to other JPA schemes.
3.3. Statistical Optimal Jamming Power Allocation method
In this method, perfect channel user node only has the knowledge about the jammer
node channel state information, rather than the instantaneous channel state
information.
(16)
Where represents the measuring parameter of statistical node channel state
information. To achieve SOJPA channel state information, calculate the difference
between perfect channel user node and jammer node.

TABLE 1: Comparison of the Jamming Power consumption among various JPA methods
Jamming Power Allocation Method
Relay Networks
OJPA RJPA SOJPA Fixed JPA
Single Amplify
and Forward 13 dB 19dB 19dB 21dB
Relay Protocol.
Three Decode
and Forward 7dB 8dB 8.5dB 10dB
Relay Protocol.
This table shows, an Outage optimal jamming power allocation scheme utilized in
minimum jamming power.
5. RESULTS AND DISCUSSION
In this section, simulations results are drawn based on the various jamming power
allocation method. Fig.2 depicts the performance of different optimal power
allocation schemes are RJPA, OJPA, SOJPA and Fixed JPA. It is observed that by
increasing the signal to noise ratio rate, and also minimize the power consumption, so
that the secrecy rate of the system have been improved. Comparing these various
power allocation schemes, fixed jamming power allocation method provides the most
terrible performance than further allocation schemes by using maximum amount of
jamming power.
Figure 2 Comparison of the various optimal power allocation schemes Vs
Average Signal to noise ratio rate.
Outage optimal jamming power allocation scheme provides the maximum secrecy
rate by using not as much of power consumption. Statistical optimal jamming power
allocation scheme provides the most terrible performance than other power
optimization schemes, using maximum level of signal to noise ratio gain. Rate
optimal jamming power allocation scheme have the slight loss in secrecy rate. Outage
is occurred, cannot be achieve a maximum secrecy rate at the destination.

Figure 3 Comparison of the maximum achievable data rates among different JPA methods.
Fig.3 shows the maximum data rate received at the perfect channel user node. It
can be observed that by using decode and forward relay protocol offers superior
performance, instead of by using amplify and forward relay protocol provides the
moderate secrecy rate. Because Amplify and forward relaying protocol, without have
a decoding and encoding procedure.
5. CONCLUSION
This paper has studied the analysis of various optimal power allocation methods with
maximum secrecy consideration. The proposed scheme achieves a one source node,
three decode and forward relay node, single jammer node and single perfect channel
user node to exploit the security level against the jammer node. Maximum secrecy
rate was achieved by using decode and forward relay protocol. Outage optimal
jamming power allocation scheme provides the maximum secrecy rate by using not as
much of power consumption. To get better the secrecy rate modulation was performed
by using Quadrature phase shift keying modulation scheme. It is clear from the
observation that for superior values of the signal to noise ratio and the power
consumption was minimized. This work can be additionally extended by escalating
the relay nodes and also the system can be additionally improved with different
modulation techniques. Secured transmission is a most important concern in wireless
relay networks, such as military network and mobile phone wallet applications.
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