Clustering Protocol

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An Agent Based Clustering Protocol for Energy

Efficient Wireless Sensor Network

Kumar Vivek, Ashok Kumar, Nilesh D. MakwanaElectronics & Communication Engineering Department

National Institute of Technology, Hamirpur

Himachal Pradesh, [email protected], [email protected], [email protected]

Abstract — Limited power resource is one of the major

constraints for wireless sensor networks (WSNs). As the

network life time is directly depends on power efficiency of

a network, so the prolonging the network life time is one of

the most important challenge for research community

from the beginning of this technology. Various techniqueshave already proposed for increasing power efficiency of

WSNs based on duty cycling, data driven techniques, or

mobility based approaches. In this paper we have

proposed an Agent Based clustering Protocol (ABCP) for

WSNs which will not only enhance the energy efficiency of

the network but also increases the overall throughput of

the network as compared to other clustering-based

schemes such like Low Energy Adaptive Clustering

Hierarchy (LEACH). Simulation results show that ABCP

is better in terms of energy efficiency and throughput as

over its comparative.

Index Terms — Duty cycling, Data driven, Mobility,

Throughput.

I. I NTRODUCTION

Typically wireless sensor network composed of largenumber of low cost sensor node having limited power, low-

communication distance (as energy is limited), limited

processing capability and small in size are deployed in a region

to sense the data like temperature, humidity, pressure etc. from

an area of interest and send them to sink by means of single

hop and/or multi hop technique. Sink is nothing but theultimate destination of data sensed by any node. The way of

communication between sink and a sensor node is depends on

the routing techniques, there are several routing protocol for WSNs [1, 2, 3]. If there is a cluster head present the sensor

node will send the data to cluster head and then cluster head

can send the data to sink, or in other hand sensor node may

communicate directly to sink node in some scenario. In some

cases the sensor node may processed the some of the sensed

data and/or cluster head can process the data too, as the energy

availability is limited, so unnecessary transmission can be

avoided by processing the sensed data. For example consider

the case of a network where node is mean to be implementedfor sensing the temperature as temperature can increase or

decrease gradually or may remain constant. So transmitting the

same temperature information or small difference intemperature periodically may not desirable because by doing

this the senor node may exhaust their energy, leading to

decreased life time of the network. So sensor node or/and

cluster head may process the data and see if there is significant

change in temperature then it will send the data to destination

otherwise it remain inactive with respect to transmission.

By use of clustering we enable a sensor network to work in

more efficient way in terms of energy efficiency and thus

leading to increased life time of the network [4]. In this casethe main function of a cluster head is to act as a link between a

sensor node and the sink, i.e. all node of a cluster first sense the

data and send it to cluster head and cluster head forwarded the

data to sink with or without data processing as requires. In this

case a cluster head issues a time division multiple accesses

(TDMA) for its member node to avoid collision as discussed in[3]. For case of homogeneous network where each node is

same with respect to power source, processing capacity,memory etc. and cluster is formed by considering some

definite number of nodes together and a cluster head is selected

among them. All other node of the cluster will communicatewith the cluster head and cluster head is responsible for

sending the all data gather from the nodes of the cluster to sink

then due to more data transmission by cluster head it will soon

exhaust its energy. This is a major problem where the cluster

head is fixed. This problem is largely studied by research

community and accordingly there are various protocols tosolve this particular problem. In LEACH [5] protocol the

author came to a solution in which the each time a cluster head

are selected among the member of a cluster by use of priori

optimal probability. This approach provides the guarantee thatthe energy load is well distributed among all the nodes of a

cluster by changing the cluster head role uniformly among allthe nodes, leading to almost same residual energy of a node

after a long run of time. Although LEACH performs well in

homogenous network however this protocol is not considered

good for heterogeneous networks as shown in [6]. In this paper

we are proposing a protocol for enhancing network life time byusing heterogeneous clustering approach using some agent

node. Particularly there are number of WSNs applications

which can be benefited by this technique. We will deploy some



agent node with the normal sensor node in the network field.

We are assuming that the agent node is not limited by power

(or at least the energy of agent node is much more than thenormal sensor node) i.e. either there is some energy harvesting

techniques are available or the battery are replaceable.

The rest of this paper is organized as follows, in Section IIwe have discuss the surveys and related work with respect to

proposed routing protocol. Section III will give the energy and

network model for proposed protocol. In Section IV we willdiscuss our proposed model. Simulation and results are

provided in Section V. At last in Section VI we will conclude

our paper.

II. R ELATED WORKS

We have already discussed that in wireless sensor network

it is desirable that a routing design needs to guarantee thedelivering of data from sensor node to sink in energy efficient

way because energy consumption and network life time are the

most important features in designing of the wireless sensor

network. There are several clustering based protocols are

available.

LEACH [5] is a clustering based routing protocol where the

overall network field is divided into number of cluster and in

each cluster head is elected based on optimal priori based probability by doing this the energy loads of the cluster head

can evenly distributed among all the nodes of a cluster, and for

long run the residual energy of all the sensor nodes of a cluster

will be almost equal, leading to larger lifetime of the network.

It is well suited for homogeneous network but not for

heterogeneous network as LEACH depends on spatial densityof the network [6].

TL-LEACH [7] the author proposed a two levels Hierarchy

for low energy adaptive clustering hierarchy. There are two

level of cluster heads present primary cluster heads andsecondary cluster heads. Secondary cluster head connect with

their corresponding sensor nodes of the cluster they are

associated with and primary cluster head is cluster head of the

cluster formed by secondary cluster heads. This mechanism

provides the well distributed load of the network to each sensor node.

In PEGASIS [8] the author proposed a chain based routing

protocol by forming chain form each node or by base stationfor sending data from sensor node to sink. Each node only

communicate with its close neighbor and turn wise transmit to

base station thus reducing the amount of energy spent each

round. But this protocol requires the global knowledge of the

network topology, makes this protocol difficult to implement.The SEP [9] is a two level heterogeneous network which

has two types of node, the advance node and the normal node.

The rotating epoch and election probability is depends on theinitial energy of the nodes. But SEP is not good for multilevel

heterogeneous network, when this type of heterogeneity is due

to the network operation of the WSN.

DEEC [10] is another protocol which is used for energy

saving in heterogeneous network using distributed energy

efficient algorithm, in which the cluster head election

probability is based on the ration of residual energy of the node

and the average energy of the network.

In EEUC [11] the author stress the fact that as the cluster

heads cooperate with each other to send the data to the sink so

the cluster head closer to the sink has more burden that the

cluster head situated far away from the sink as the nearer cluster have to forwarded the more data coming from other

cluster head. So the nearer cluster head may exhaust their

energy soon and die. The author came to solution in which hedivide the cluster in unequal size i.e. cluster closer to sink have

small size than the cluster farther to sink. By doing so the

protocol balances the energy consumption well among all the

sensor nodes.

III. RADIO ENERGY MODEL AND NETWORK MODEL

In this section we will discuss energy model used for our proposed protocol and also the network model of proposed

protocol.

A. Radio Energy Model

We are considering a very popular radio energy model [5, 9,

12] for our proposed protocol. For reception and transmissionof a bit there is always energy expenditure associated with it

also if we are using sleep mode scheduling for a particular

model then the turning on and turning off of transmitter andreceiver also requires some energy also processing of data also

requires energy. Here we are considering the energy used for

reception and transmission of data as major chunk of energy is

utilized in this only. According to energy model proposed in

Fig. 1 in order to maintain an acceptable Signal-to-Noise

(SNR) in transmitting N-bit message over a distance of d, theenergy require by the transmitter is given by:

2

N.E +N.E .d if d<delec fs 0E N,d =Tx 4 N.E +N.E .d if d delec amp 0

(1)

Here Eelec

is the energy loss per bit to run the transmitter or

receiver circuit and it depends upon factor like coding

technique used, modulation, filtering and spreading of the

channel. fs

E andamp

E depends upon transmitter model

used. d is distance between transmitter and receiver. In this

model we have consider both model of energy consumption

describe in the above equations. Now equating the above to equation for d ═ d0 we get

Efs=0dEamp

(2)

To receive bit message receiver requires energy of

E =N.ERx elec (3)



Figure 1.Radio Energy model

If the packet size of massage is of bits then residual energy

( EResidual ) of a node after one round of transmission can be

found by the following equation

2E -{ E +E +E ×d }B if d<d0 T DA fs 0XE =Residual

4E -{ E +E +E ×d }B if d d0 T DA amp 0X

(4)

Where, 0 E is the initial energy provided to each sensor node.

E E E,T f ,E ,sx A ampDis per bit transmission, compression,

free space loss and multipath loss respectively.

B. Network Model

In this section we will describe ABCP network model for

wireless sensor network which is composed of some agent

node i.e. heterogeneous network with respect to the initialamount of energy. We are deploying sensor node in an area of

interest with some agent node as shown in Fig. 2.

Let us consider we are deploying N number of sensor nodesin M×M region as shown in Fig. 2. Where, M denotes the

length and breadth of the network field. Let us say node is

represented by Si = {S1, S2, S3, S4….S N}. Also we are

deploying P number agent nodes at fixed places, which will act

as local sink for the some of the nodes let us say agent nodes

are represented as A j = {A1, A2, A3, ……AP}. We are taking

negligible number of agent node as compared to sensor node.

I.e. P << N. We will place the agent nodes in network field in

such a way so that sink can create some logical area by

dividing the network field in smaller sub-field, which will

efficient in terms of energy saving. That sink is associating

maximum number of nodes which can directly send its senseddata to an agent node or sink.

The assumptions used in the proposed routing techniques

are as follows:

Sensor nodes are randomly deployed in our

network field and it is using uniform random

distribution, and each of the sensor nodes has same

computational power as well as energy.

The Sink is located outside of our network field and

we know the co-ordinate of it.

Agent nodes are rechargeable and the placement of

agent node is not random (we will fix the coordinate

of agent nodes) i.e. either the node is deployed

manually or the agent node is movable.

Each sensor node assigned a unique ID.

IV. AGENT BASED CLUSTERING PROTOCOL

We will discuss our proposed routing models in this

section. As sensor node has to send the sensed data to sink. If

the sensor node send the data to directly to sink or with help of

multi hop technique the sensor node may exhaust their energy

soon as they have to send their own data as well as they have to

work as transit node too for the data forwarding for data of

other nodes. Although clustering technique like LEACH is

good and able to increase the life time of network considerably

but with the help of our proposed model we will able to

increase the life time of network almost double as compared to

LEACH. For increasing the network life time and throughput

we deploy some agent node at some fixed location in the

network field such that a virtual maximum area network sub-

field can created such that all the nodes within that sub-fieldcan communicate with an agent node directly as well some

sensor node can communicate with the sink directly while

considering energy efficiency. The function of agent nodes is

to collect data from the nodes near to it and can also collect the

data from the cluster heads of the other cluster forming by the

nodes which have not any agent node nearby. The agent node

work is forwarding the overall aggregated data collected by

other cluster heads and the data gathered from the sensor node

associated with it to the sink. Our result will reflect the increase

life time and throughput with the expense of addition of agent

nodes because adding rechargeable agent node is cheaper than

the price of sensor node itself. We can broadly identify our

proposed network implementation as following steps: A. Initial Phase

We will use homogeneous sensor node with respect toenergy and deployed it in our network field in uniformly

random distributed way. The sink broadcast a hello packet; in

response of this packet each sensor node will forward its

location and other information to the sink. Now the sink has

sensor node ID, energy information of the node, and

information about sensor node euclidean distance from itself

and also from agent nodes.

Figure 2.Network field



B. Middle Phase

Now as sink has required information for dividing the

whole network field into logical region based on location of

sensor node in the network field. Sink now divided the whole

region in three type of region the first type of region will

directly send its gathered data to sink, the second type of region

will communicate directly with agent nodes and the third typeof region will not associated with any agent node or sink

directly but they are divided into number of clusters and they

choose their cluster head depending upon priori based probability, and the cluster head can communicate and send

their data to agent node or sink node directly i.e. via single hop

or multi hop as required.

C. Final Phase

Now sink divided the network field into three types of

logical region. The node residing in first type of region, which

will be close to sink itself, can send their sensed data to sink

directly leading to energy saving. The node residing in second

type of region i.e. region closed to any agent node will forwardtheir data directly to an agent node which leads to energy

saving. The third type of area which is not associated with any

agent node or sink directly, is divided in to small regions

(cluster) by sink. So the cluster formed by third type region

needs a cluster head for energy efficient communication whichis chosen by LEACH protocol. Each node of particular cluster

has probability of p to act as cluster head, i.e. each node will

elect as cluster head at least once after 1/p rounds as proposed

in LEACH. The 1/p round is referred as epoch. The 1/p round

is referred as epoch. Initially all the nodes of third type of

region has equal energy level and has equal chance to became

cluster head and the probability of being so is p. On an average

(N–K).p of cluster head present in the network field apart fromagent nodes, Where K is number of sensor nodes which are

associated directly agent nodes or sink. Nodes that are elected

to become cluster head in the current round cannot become

cluster head in same epoch. At the start of each round a node Si

from the third type of region autonomously choose a number

between 0 and 1. If chosen number for node Si is less than a

predefined threshold T(S) then that node will be act as cluster

head for that round.

pif S C

1-p×(r×mod(1/p))T(S)=

0 otherwise

(5)

Where, r is the current round number starting from round 0.C is the set of nodes which have not been cluster head in the

last 1/p rounds. Using this threshold level each node of a

particular cluster head have a chance to became cluster head

once in each round.

All sensor nodes transmit their data to cluster head in

steady state phase. The cluster head collect the data from

member nodes and send it to nearest agent node. Agent node

received the data processed it and send it to sink.

V. SIMULATION AND R ESULTS

We have simulated our setup on MATLAB and check

performance of the protocol and compare it with one of

standard routing protocol of WSNs LEACH.

A. Performance Parameters

In this subsection we have consider the performance

parameter for our simulation. We have check and compare our

protocol based on following performance parameters:

1) Network Lifetime: Here we have considered the network

lifetime here as number of round till the last node of the

network died.

2) Throughput: It is one of the performance analyses for our

proposed protocol where we check the total number of packet

received by the sink.

3) Residual Energy: We will check the total amount of

energy left in the network. Because on this parameters our

network lifetime depends.

B. Simulation Parameters

In order to analyze and compare the above mentioned performance parameters with LEACH protocol with ABCP we

consider that there are 100 numbers of sensor nodes which are

deployed randomly in network filed of area

Four agent node is deployed at the

corner of a square sub-field of the

consider network field, and considered sub-filed diagonals are

whose diagonals bisecting each other at the same point where

the original network field diagonals are bisecting each other.

The sink is not situated in network field and sink and agentnode are stationary after deployment. Table 1 contains the

other simulation parameters used for performance analysis of

our proposed protocol.

C. Simulation Result and Analysis

In this subsection we will discuss the simulation result

obtained and compare it with leach and see how ABCP turn out

to be better compared to LEACH with respect to residual

energy, network lifetime and overall throughput at sink.

1) Residual Energy: We will analyze and compare the total

energy remaining in the network field after each round

assuming that each sensor node has equal energy of 0.5 J.Since, the network has total 100 sensor nodes, so total energy

of the network will be 50 J, shown in Fig. 3.

Table 1.Simulation parameters

Parameters Value0.5 J

10 pJ/bit

0.0013 pJ/bit

87.70 m

50 nJ/bit

5 nJ/bit

2000 bits



Figure 3.Number of rounds versus residual energy

Figure 3. shows the number of round versus residual energy

plot of the proposed protocol and its comparison with LEACH

protocol.

We can see from the Fig. 3 that by using our proposed protocol

the network has almost 8 J of energy remaining with it when

by using LEACH protocol the network is out of energy,i.e.16% of total energy of the network is still there when all the

sensor node using LEACH protocol exhausted their energies.

2) Network Lifetime: We can compare the overall network

lifetime of network as the total number of rounds till the lastnode of the network is alive. Figure 4 shows the number of

rounds and percentage of alive nodes at that time.

We found that after 3000 round there is no alive node in in

the network filed where the nodes are communicating using

LEACH protocol whereas by using our proposed technique

network can extend in terms of alive node till approximately

5000 rounds which is approximately 66 % more than LEACH.

I.e. we are significantly increasing network lifetime using

proposed routing protocol. Also we can see that there is suddenincrease in the number of dead nodes after 4000 round it is due

to fact that node communicating directly with agent nodes will

exhaust their energies almost at the same time.

3) Throughput: Here we will see the overall throughput of

the network i.e. the total number of packets received by sink.

Figure 5 shows that at the end of network lifetime the total

number of packets received by sink using proposed protocol is

almost 5 times more than the total number of packets received by sink using LEACH protocol.

Figure 4.Number of round versus percentage of alive nodes

Figure 5.Total number of packets received by sink

VI. CONCLUSION

In this article we have proposed an agent based protocol for

energy efficient WSN. As our result shows that the proposed

protocol is efficient in terms of lifetime, energy efficiency and

overall throughput. But flip coin of the side is that we aredeploying agent node in the network field which has better

energy resource or have energy harvesting technique with it,

also we have to manually deployed the agent node or we have

to take mote as agent node, which is costlier than generalsensor nodes but we know that providing better energy source

to a node is cheaper than sensor node itself. So we can use our

proposed routing protocol for better energy efficiency and high

throughput in expense of a little costlier deployment cost.

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