DSpace at VNU: Cooperative communication techniques for cluster size expansion in cluster based Wireless Sensor Network

Cooperative Communication Techniques for Cluster Size Expansion in Cluster Based Wireless Sensor Network Tuan-Duc Nguyen, Truong-Minh Nguyen Ngoc and Vo Nguyen Quoc Bao International Uni

Cooperative Communication Techniques for Cluster Size Expansion in Cluster Based Wireless Sensor

Network

Tuan-Duc Nguyen, Truong-Minh Nguyen Ngoc and Vo Nguyen Quoc Bao

International University, Vietnam National University Post and Telecommunication Institut of Technology, Vietnam

Email: ntduc@hcmiu.edu.vn

Abstract—In the context of energy constrained wireless sensor

networks where individual nodes can cooperate together to

deploy the cooperative communications, Relay and cooperative

Multi-Input Multi-Output (MIMO) techniques can be used to

exploit the diversity gain to increase the performance or to

reduce the transmission energy consumption Based on the energy

efficiency of cooperative communication, a new scheme of using

cooperative MISO and Relay techniques for two way data

transmission in cluster based Wireless Sensor Networks (WSN) is

proposed in this paper The energy consumption of the multi-hop,

Relay and cooperative MISO transmission have been investigated

in this paper Simulation and energy calculation results show

that the proposed cooperative scheme has a much lower energy

consumption than the traditional multi-hop transmission scheme

and the proposed scheme can be used to increase efficiently the

size of WSN cluster

I INTRODUCTION

In distributed wireless sensor network where some

indi-vidual sensor nodes can cooperate for the transmission and

the reception in order to set up a cooperative communication,

Relay techniques have been known as a simple and energy

efficient technique to extend the transmission range due to their

simplicity and their performance for wireless transmissions

over fading channels [5], [9]

Beside the relay technique, cooperative MIMO technique

can cooperate individual nodes in order to deploy a MIMO

transmission using space time codes [3], [6] Cooperative

MIMO technique can exploit the diversity gain of space time

coding in order to reduce the transmission energy

consump-tion It has been shown that cooperative MISO and cooperative

MIMO techniques have a lower energy consumption than the

traditional SISO and multi-hop SISO techniques [2], [7]

In WSN, cooperative communications can be used to

re-duce efficiently the transmission energy consumption which

is important for medium to long distance transmission where

transmission consumption is dominant in the total energy

consumption In various applications, such as environment

monitoring, area surveillance for agriculture or intelligent

transportation systems, middle and long range transmissions

are indeed often required because of the weak density of

the wireless sensor networks Relay and cooperative MISO

techniques are very useful for this wireless sensor network

applications where the energy consumption is the important constraint

Clustering has been proved to be an energy-efficient method

of network planning in many kind of WSN The cluster based network is divided into many clusters, each cluster has a cluster head and many member sensor nodes Energy efficiency of cluster based wireless sensor network have been reviewed in [8], [4]

In cluster based wireless sensor network, the size of cluster depends on the maximum transmission distance between the cluster header and outer wireless sensor node The application

of cooperative communication in cluster based WSN reduces not only the energy consumption, but also helps increase the maximum transmission distance of cluster head The energy efficiency of cooperative MISO transmission in cluster based WSN has been studied in [10]

In this paper, we propose an energy-efficient cooperative transmission scheme in which cooperative MISO technique is used for data transmission from cluster head to sensor nodes and Relay technique is used for data transmission from a sensor node to cluster head This proposed technique exploits the diversity gain of cooperative MISO va Relay techniques

in order to reduce the energy consumption or increase the transmission distance between cluster head and sensor nodes

In cluster based WSN, this techinque helps increase the size

of one cluster for the same energy consumption of all wireless sensor nodes

The rest of the paper is organized as follows The clus-ter based wireles sensor network model and the proposed cooperative communication scheme are presented in section

II The energy comsumption model and the energy consump-tion calculaconsump-tion of multi-hop, cooperative MISO and Relay techniques are presented in Section III In section IV, the result of performance simulation and energy consumption comparison of all cooperative techniques are shown Finally, the conclusion is given in Section V

The 2012 International Conference on Advanced Technologies for Communications (ATC 2012)

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Fig 1 Cluster based WSN

II COOPERATIVECOMMUNICATIONS FORCLUSTER

BASEDWIRELESSSENSORNETWORK

A WSN Cluster Model

As illustrated in Fig 1, consider that one cluster in cluster

based WSN has a head Sensors in one cluster collect data

and send its back to the cluster head and data communication

between cluster head and sensors is two way communication

Cluster head play also as a role of network router in order to

send data to other clusters In this kind of cluster based WSN,

the size of one cluster depends on the coverage area of the

cluster head, ie the maximum two way transmission range

between the cluster head and outer wireless sensor nodes

The transmission distance depends on the maximum power

consumption of cluster head and sensor nodes

As the transmission power increases with the power function

of transmission distance and the power path loss factor k

(k value is typically from 2 to 5 for wireless channel),

transmission power is significant for medium to long distance

transmission and dominates the total energy consumption of

a wireless node In order to reduce the transmission power

consumption, multi-hop technique is a traditional approach

to reduce the transmission consumption of wireless node

As illustrated in the top picture of Fig 2, cluster head can

send data to outer sensor node over 2 hops transmission

through a middle sensor node between the cluster head and

the destination sensor

B Cluster Size Expansion using Cooperative Communication

Beside the multi-hop transmission, cooperative

communica-tion likes cooperative MIMO or Relay techniques can also be

employed in WSN in order to reduce the transmission power

consumption In this paper, we propose a cooperative

trans-mission scheme using cooperative MISO and Relay technique

for cluster based WSN of cluster head and wireless sensor

nodes

Consider that one cluster has a head, and this cluster head

can choose a cooperative node near it (cluster head is maybe

generated randomly to form clusters and cluster head can

choose a nearby node as a cooperative node) This cluster head

can cooperate with the cooperated node in order to deploy the cooperative MISO and Relay transmissions

As illustrated in Fig 2, consider that the cooperative node

is nearby the head (it is easier to set-up a cooperative node nearby the cluster head than father from the cluster head) Instead of using 2 hops transmission (like in the top picture

of Fig 2), the proposed scheme uses cooperative MISO and relay transmission to send and receive data between cluster head and outer sensor node as illustrated in middle and bottom pictures of Fig 2

Fig 2 Multi-hop, Relay and cooperative MISO transmissions between the cluster head and sensor node in cluster based WSN

In this proposed scheme, cluster head cooperates with cooperative node to deploy a cooperative MISO transmission using Alamouti STBC in order to sent data to sensor node for forward link transmission There are two phases of communi-cation:

• Phase 1: cluster head sends a data sequence to the cooperative node in the first time slot The cluster head and this cooperative node encode data sequence into space time code sequences

• Phase 2: Two nodes send this space time code sequence

in the second time slot to the reception wireless sensor node node The reception node combines the received space time sequence and decodes the signal

For reverse link (data transmission from sensor node back

to cluster head), because the cooperative node is far from the sensor node, it is not efficient to deploy a cooperative MISO transmission So that, the cooperative node will play as

a relay node in order to deploy a relay Amplify and Forward transmission for data sending from sensor node back to the cluster head There are also two phases of communication:

• Phase 1: Sensor node sends data sequence to the cluster head and the cooperative node in the first time slot

• Phase 2: Cooperative node plays as a relay node and forwards it received signal to the cluster head by using the Amplify-Forward technique in the second time slot Cluster head combine the received sequence from the sensor node and relayed sequence from the cooperative

f c = 2.5 GHz η = 0.35

G t G r = 5 dBi N0

2 = −174 dBm/Hz

¯

P f ilt = P f ilr = 2.5 mW P LN A = 20 mW

TABLE I

node by using Maximum Ratio Combining technique and

decodes the signal

Fig 2 illustrate two phases of communication of the

coop-erative MISO and Relay transmission technique Continuous

line and dash line are stand for the first and second phase of

transmission

Cooperative MISO and Relay technique can exploit the

diversity gain in order to increase the performance or

re-duce the energy consumption for the same performance In

comparison with multi-hop technique, It can increase the

transmission distance for the same energy consumption By

using the cooperative MISO and Relay technique for two way

communication in a cluster, the transmission distance between

the cluster head and outer sensor node can be increased for

the same energy consumption, leading to the cluster size

expansion in cluster based WSN

III ENERGYCONSUMPTIONMODEL

For energy consumption estimation, evaluation and

compar-ison purposes, the reference power consumption model in [1]

[7] is used in this paper as a reference The system parameters

of this model is presented in Table I

Let us consider multi-hop, cooperative MISO and Relay

transmissions like in Fig 2, the total energy consumption of

each transmission is calculated in this section by using this

reference consumption model

A Consumption multi-hop transmission scheme

Energy consumption of multi-hop transmission is the sum of

the consumption of each hop For each SISO transmission hop,

the total power consumption consists of two components: the

transmission power Ppaof the amplifier and the circuit power

Pc of all RF circuit blocks of transmitter and receiver

Ppadepends on the output transmission power Pout If the

channel is considered as a square law path loss channel (power

loss factor K = 2), the transmission power required for a

transmission distance d can be calculated as

Pout(d, ¯Eb,SISO) = ¯Eb,SISORb× (4πd)

2

GtGrλ2MlNf (1) where ¯Eb,SISOis the required mean energy per bit of SISO

transmission for ensuring a given error rate requirement, Rb

is the bit rate, d is the transmission distance Gt and Gr are

the transmission and reception antenna gain, λ is the carrier

wave length, Ml is the link margin, Nf is the receiver noise

figure defined as Nf = Mn/N0 with N0 is the single-side thermal noise Power Spectral Density (PSD) and Mn is the PSD of the total effective noise at receiver input Depending

on the Power Spectral Density (PSD) of thermal noise N0, the ¯Eb,SISO can be calculated based on Eb/N 0 value given

in Fig 3 for a specific FER requirement

The power consumption Ppacan be approximated as

Ppa,SISO(d, ¯Eb,SISO) = (ξ

η)Pout(d, ¯Eb,SISO) (2) where ξ is the drain efficiency of the RF power amplifier and η is the Peak-to-Average Ratio (PAR) which depends on the modulation and the associated constellation size

Consider that the consumption of digital signal processing block of transmitter and receiver is small to the connsumption

of other analof RF block, we neglect the consumption of this

on the calculation of circuit consumption The total circuit power consumption is given by

Pc,SISO= Pc,transmitter+ Pc,receiver

≈ (PDAC+ Pmix+ Pf ilt+ Psyn) +(PLN A+ Pmix+ PIF A+ Pf ilr+ PADC+ Psyn) (3) where PDAC, Pmix, PLN A, PIF A, Pf ilt, Pf ilr, PADC,

Psyn stand respectively for the power consumption values

of the digital-to-analog converter, the mixer, the low noise amplifier, the intermediate frequency amplifier, the active filter

at the transmitter and receiver, the analog-to-digital converter and the frequency synthesizer

The total energy consumption of the transmission of Nbbits can be obtained as

Ehop(d) = (Ppa,SISO(d, ¯Eb,SISO) + Pc,SISO)Nb

Rb (4) Energy consumption of a multi-hop transmission is the sum

of energy consumption of each hop

B Consumption of Cooperative MISO transmission in for-ward link

Energy consumption of a cooperative MISO transmission (with one cluster head and one cooperative node) is the sum

of the energy consumption of two communication phases Phase 1 uses a SISO transmission for data transmission from the cluster head to the cooperative node, so the the energy consumption of phase 1 can be calculated like the case of one hop transmission over a distance dmbetween cluster head and cooperative node The energy consumption of phase 1:

Ecoop(dm) = (Ppa,SISO(dm) + Pc,SISO)Nb

Rb

(5)

In phase 2, cluster head and cooperative node encode data sequence using Alamouti code and send it in same time to the destination sensor node The transmission consumption of phase 2:

Ppa,M ISO(d, ¯Eb,M ISO) = (ξ

η) ¯Eb,M ISORb× (4πd)

GtGrλ2MlNf

(6) where ¯Eb,M ISO is the required mean energy per bit of

MISO transmission which can be calculated based on Eb/N0

value given in Fig 3 for ensuring a given error rate

require-ment

Neglecting the power conmsumption of space time encoding

and combination process, the circuit consumption of phase 2:

Pc,M ISO≈ 2(PDAC+ Pmix+ Pf ilt+ Psyn)

+(PLN A+ Pmix+ PIF A+ Pf ilr+ PADC+ Psyn) (7)

The energy consumption of phase 2:

EM ISO(d) = (Ppa,M ISO(d, ¯Eb,M ISO) + Pc,M ISO)Nb

Rb (8)

So, the total energy consumption of the cooperative MISO

transmission is

EcoopM ISO(d) = Ecoop(dm) + EM ISO(d) (9)

C Consumption of Relay transmission in reverse link

For the reverse link transmission from sensor node back to

the cluster head, there are two phase of Relay transmission:

phase 1 of transmission from detination back to header and

cooperative node (relay node), and phase 2 cooperative node

use amplify and forward to send data to cluster head The

total energy consumption ERelay is the sum of the energy

consumption of each transmission phase

The transmission power consumption and circuit power

consumption of phase 1:

Ppa(d, ¯Eb,Relay) = (ξ

η) ¯Eb,RelayRb× (4πd)

2

GtGrλ2MlNf (10)

Pc,Relay≈ (PDAC+ Pmix+ Pf ilt+ Psyn)

+2(PLN A+ Pmix+ PIF A+ Pf ilr+ PADC+ Psyn)(11)

where ¯Eb,Relayis the required mean energy per bit of Relay

transmission, which can be calculated based on Eb/N 0 value

given in Fig 3 for ensuring a given error rate requirement

The energy consumption of phase 1:

Erelay1(d) = (Ppa(d, ¯Eb,Relay) + Pc,Relay)Nb

Rb

(12)

In phase two, cooperative node amplifies the received

se-quence and uses a SISO transmission for data forwarding to

the cluster head The the energy consumption of phase 2 can

be calculated like the case of one hop transmission over a

distance dm between cooperative node and cluster head The

energy consumption of phase 2:

Erelay2(dm) = (Ppa,SISO(dm, ¯Eb,Relay) + Pc,SISO)Nb

Rb (13)

So, the total energy consumption of Relay transmission is

ERelay(d) = Erelay1(d) + Erelay2(dm) (14)

IV SIMULATION RESULTS

A Performance of cooperative MISO and Relay techniques Simulations of cooperative MISO technique (using Alam-outi code) and Relay technique are performed The system uses an uncoded quadrature phase shift keying (QPSK) mod-ulation, the channel is considered to be Rayleigh fading and independent for each frame of 120 symbols For the reliability

of result, 106 frames have at least been sent for assuring the frame-error-ratio F ER = 10−4

Eb/No(dB)

SISO cooperative MISO Relay A−F

Fig 3 FER of SISO technique, relay technique and cooperative MISO technique, non-coded QPSK modulation, Rayleigh fading channel,power path loss factor k=2.

Fig 3 represents the Frame Error Rate (FER) performance comparison of the traditional SISO technique, relay techniques (Amplify-and-Forward) and the cooperative MISO technique for two cooperative transmit nodes (one cluster head and one cooperative node) Fig 3 shows that performance of Relay and cooperative MISO techniques are better than the traditional SISO technique (for the same error rate requirement, received SNRs of relay and cooperative MISO is lower than SISO) At the typical error rate requirement F ER = 10−3 for Wireless Sensor Network, Eb/N0 of SISO, Relay and cooperative MISO techniques are respectively 36, 27, and 22 dB For medium to long distance transmission, the transmission power consumption is usually much greater than the circuit consumption and dominates the total energy consumption Cooperative MISO and Relay techniques help reduce the transmission consumption, leading reducing the total energy consumption of the transmission

B Energy consumption comparison

The energy consumption were calculated by using the

system parameters presented in Table I The following figures

represent the total energy consumption to transmit 107 bits

with the error rate requirement F ER = 10−3 between a

cluster head and a sensor node separated by a distance d

The channel is considered as a Rayleigh block fading channel

with the channel path loss factor k = 2 The relative distance

between cluster head and cooperative node is dm= d/10

0

0.5

1

1.5

2

2.5

3

6

Distance(m)

SISO

cooperative MISO

Relay A−F

multi−hop

Fig 4 Energy consumption of multi-hop technique, relay technique and

cooperative MISO technique, power path-loss factor k = 2

Fig 4 shows the total energy consumption (in function of

transmission distance d) of the multi-hop (2 hops), relay and

cooperative MISO techniques in comparison with traditional

SISO technique (one hop transmission) for one way

trans-mission from cluster head to destination sensor node

Multi-hop transmission has a lower energy consumption than SISO

transmission It is also obvious that the energy consumption

of Relay and cooperative MISO techniques is lower than the

multi-hop transmission technique

Fig 5 shows the energy consumption of all techniques for

longer transmission distance from 100m to 300m The obvious

advantage of the cooperative MISO and Relay techniques over

multi-hop SISO technique is shown For the case of the path

loss factor k > 2, the transmission energy consumption will

be greater than the case of k = 2 Cooperative techniques help

saving the transmission energy consumption (because of the

smaller Eb/N0), so that the advantage of cooperative MISO

and Relay will be more significant

C Cluster size expansion using cooperative technique

Coverage area of one cluster depends on the maximum

transmission distance between the cluster head and sensor

node Consider a 2 way transmission between the cluster head

and sensor node (separated by a distance d), we calculate

the total energy consumption of the mutlti-hop transmission

scheme (2 hops and 4 hops transmission from cluster head

100 120 140 160 180 200 220 240 260 280 300 0

2 4 6 8 10 12 14

Distance(m)

cooperative MISO Relay A−F Mutlti−hop

Fig 5 Energy Consumption of multi-hop technique, relay technique and cooperative MISO technique, power path-loss factor k = 2.

to sensor node) and the proposed scheme where cooperative MISO and relay techniques are used for forward and reserve links

Based on the result of total energy consumption calculation

of two way transmission, Fig 6 shows the transmission distance in function of the total energy consumption of the proposed cooperative scheme and the traditional multi-hop scheme (using 2 hops and 4 hops transmission) Fig 6 shows that, with the same energy consumption,the proposed cooperative scheme always has a longer transmission distance between the cluster head and wireless sensor node ItÕs mean that, the cluster size can be expanded with the same total energy consumption of cluster head and sensor node

100 150 200 250 300 350 400 450 500 550 600

Energy Consumption (mJ)

Cooperative communication

2 hops transmission

4 hops transmission

Fig 6 Transmission distance in function of the total energy consumption

of cooperative scheme and multi-hop scheme.

For example, if the cluster head uses 2 hops transmission in

order to send and receive properly the data to wireless sensor

node and the cluster size (maximum distance) is 200m For the

same energy consumption, the cluster size can be increased to

500m by using the proposed cooperative scheme If the cluster

size of 2 hops scheme is 240m, the cooperative scheme can

increase the cluster size to 600m for the same total energy

consumption It can be also observed that multi-hop scheme

with 4 hops transmission has also a longer transmission

distance than 2 hops transmission, but still shorter than the

proposed cooperative scheme Another drawback of 4 hops

transmission is the transmission delay because it requires 4

phases of transmission instead of 2 phases of the proposed

cooperative scheme

V CONCLUSION Cooperative MISO and relay techniques provide attractive

benefits for distributed wireless sensor network when diversity

gain can be exploited to reduce the transmission energy

consumption The energy efficiency of cooperative MISO and

Relay can be employed in cluster based WSN in order to

increase the cluster size and the energy consumption in same

time

The energy efficient scheme using cooperative MISO and

Relay techniques for two way data transmission in cluster

based WSN has been proposed in this paper Simulation and

energy calculation prove that the proposed scheme has a much

lower energy consumption in comparison with the traditional

multi-hop transmission scheme In cluster based WSN context,

the proposed scheme can increase the maximum

communica-tion distance between the cluster head and sensor nodes for the

same energy consumption of multi-hop transmission scheme,

so increases the cluster size of network

ACKNOWLEDGMENT This research was supported by the Vietnam’s

Na-tional Foundationfor Science and Technology Development

(NAFOSTED) (No 102.01-2011.22)

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