energy efficient routing protocol using local mobile agent for large scale wsns

7/30/2019 Energy Efficient Routing Protocol Using Local Mobile Agent for Large Scale WSNs

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Energy Efficient Routing Protocol Using

Local Mobile Agent for Large Scale WSNsAli Seirafi, Mohammad Hadi Moazzam, Farshad Kabiri Samani

Abstract The energy consumption is always an important topic for research on routing protocols of wireless sensor networks.

Many algorithms are introduced in this field and each of them can propose solutions in order to improve the energy consumption

issue. Energy Efficient Cluster Head Selection (EECHS) is one of the most well known protocols in WSN, but its performance

decreases with increase of the network scale. To solve this problem, we introduce an improved routing protocol uses a new

multi hop transmission method to balance energy consumption among the whole network. This approach reduces the time

distance between failing of the first and the last nodes at minimum and keeps network coverage until the last moments. The

simulation results performed in MATLAB, show that the proposed algorithm is more efficient and increases the network lifetime.

Index Terms Local Mobile Agent, Clustering, Routing Protocol, Network Lifetime.

1 INTRODUCTION

n the WSN, the network composed of a huge number ofsmall self-contained devices with computational, sens-

ing and wireless communication capabilities coveringthe monitoring area.Energy consumption is one of the major challenges andmany studies have attempted to tackle this problem.Nodes are powered by a small battery, which may runout in a short time [1]. Hence, an efficient routing protocolcan increase the network lifetime.

According to the final topology, the routing protocols ofWSN are categorized into two types; flat routing and hi-erarchical routing protocols. As flat routing protocolsneed to maintain large routing table information, they areunsuitable for large-scale sensor networks. Hierarchicalcan solve this problem to a certain extent.

Low Energy Adaptive Clustering Hierarchy (LEACH)[2] is one of the first major algorithms based on hierar-chical method. LEACH is a completely distributed rout-ing algorithm which does not require any global infor-mation for cluster formation and routing. The clusteringstrategy is mainly depends on the randomly selected clus-ter-heads and does not consider the residual energy ofnodes. [3]

Many clustering algorithms are based on LEACH ar-chitecture and improve the network lifetime. Energy Effi-cient Cluster Head Selection (EECHS) [4] is one of them.It considers the factor of residual energy, distance from

the Base Station and the number of consecutive rounds inwhich a node has not been a cluster head.

In this study, EECHS algorithm is improved by theaddition of two factors; distance between cluster headsand minimum energy that each node require to be a clus-ter head.

Simulation result shows that proposed protocol hasbetter performance than LEACH and EECHS.

2 RELATED WORK

2.1 LEACH

LEACH is a time division multiple access based ondistributed clustering approach in homogeneous WSNs.[5] The algorithm is self-organized, employs a single hopapproach and the data combination technique can de-crease the rate of data transfer. This algorithm is dividedinto two stages; setup stage and steady stage.

During the first stage, all nodes are organized intosome clusters through communicating with short mes-sages and one node is selected as a cluster head accordingto the cluster head selection algorithm. At the beginningof this phase every node in the network must decidewhether it will become a cluster head or not. This deci-sion is made by the node n choosing a random numberbetween 0 and 1. If the number is less than a thresholdT(n), the node becomes a cluster head for the currentround. [6] The threshold value T(n) is calculated by (1),where p is the predetermined percentage of cluster heads,r is the current round number, and G is the set of nodesthat have not been cluster head in the last 1/p rounds.

GnifnT

Gnif

prp

pnT

0)(

mod1

)(

(1)

Ali Seirafi is with the department of Electrical and Computer Engineering,Lenjan Branch, Islamic Azad University, Isfahan, Iran.

Mohammad Hadi Moazzam is with the Engineering Faculty, Payam NoorUniversity, Tehran, Iran

Farshad Kabiri Samani is with the department of Electrical and ComputerEngineering, Lenjan Branch, Islamic Azad University, Isfahan, Iran.

I

JOURNAL OF COMPUTING, VOLUME 5, ISSUE 2, FEBRUARY 2013, ISSN (Online) 2151-9617

https://sites.google.com/site/journalofcomputing

WWW.JOURNALOFCOMPUTING.ORG 1


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After the setup stage, cluster heads simultaneouslybroadcast TDMA scheduling messages using spreadingcodes to start the steady stage, which involves data signalsending from non-CH nodes to the CH nodes by TDMAscheduling, aggregation and routing to the Base. LEACHuses a single hop routing algorithm and each CHs sendthe aggregated data to the Base Station in a single hopmanner. [7]

LEACH is based on rounds and the system repeats theclustering and transmission for each round. LEACH hasits own defects, but improved algorithms will definitelysolve these problems. Some of these problems are as fol-lows:

1. Cluster heads are predefined in LEACH protocoltypically taken as 5% or 10% of total deployednodes. If sensor nodes in the network are not uni-formly distributed, specified number of clusters

might not be sufficient to cover the entire area.2. Cluster heads send aggregated data to the Base

Station in a single hop manner, so consume a lotof energy.

3. Probability function T(n) does not take residualenergy of nodes into account while selectingcluster heads, so if a less energy node becomesCH, it will fail and subsequently the cluster net-work becomes dysfunctional.

4. It consist of rounds while in each round, all sen-sor nodes take part in reconstructing new clus-ters and this action consumes a lot of energy. [4]

2.2 EECHS

EECHS [2] improves the LEACH protocol by improvingthe election strategy of the cluster heads, considering re-sidual energy, distance from the Base Station, number ofconsecutive rounds in which a node has not been a clusterhead.

In EECHS, stochastic cluster head selection algorithmis extended by adjusting the threshold T(n) denoted in (1),considering the residual energy of the nodes, distancebetween the nodes and the Base Station and the numberof consecutive rounds in which a node has not been acluster head as follows:

)]())(1()([

mod1

)( rdivsiDiE

prp

pnT

(2)

Here the residual energy factor is:E(i) = (Eresidual(i) /Einitial) Where Eresidual is the remainingamount of energy and Einitial is the initial energy of a nodebefore transmission and Variable i indicates the serialnumber of nodes.The Distance factor D(i)=diB/dfarthest Where debt is the dis-tance from node i to Base as shown in (3):

22)()( BSiBSiiB YYXXd (3)

And dfarthest is the distance of the farthest node from theBase Station. Here XBS and YBS are the location of the Base

Station.In the third parameter (s div r), s is the number of consec-utive rounds in which a node has not been a cluster headand r is the number of the current round.

Instead of considering these three important parame-ters, EECHS does not consider the factor that whether thenodes remaining energy are sufficient enough to send theaggregated data to the Base Station or not. Besides, inEECHS, there is no limitation for location of cluster heads.

3 PROPOSED APPROACH

In 2.1 and 2.2 sections, LEACH and EECHS Algorithmsare investigated along with problems existed in each ap-proach. A method will be presented in this part doesnthave any drawbacks of the two previous methods. Toimprove the insufficiency of LEACH and EECHS, we in-troduce an improved protocol in this paper. This protocollike LEACH and EECHS divided into two stages includesetup stage and steady stage.

Before describing the algorithm, network modelshould be investigated.

3.1 Network Model

For our proposed approach, we adopt a few reasonableassumptions as follows: [2, 3]

1. Sensor nodes are immobile.2. Nodes are not able to access Base directly.3. The Base Station is located at a far distance

from the sensor nodes and is immobile.4. All nodes are able to control their transmit

power to change the communication range.5. Access of nodes to the Base is performed by a

special node called Local Mobile Agent (LMA)located in the center of the network, in a circle

with L radius.6. All sensor nodes are homogeneous and have

the same hardware components except LMAwhich includes specific components.

7. The LMA is the only mobile node in the net-work.

8. Regarding to the access of Local Mobile Agentto the wireless charging equipment, the ener-gy of this node will be considered unlimited.

9. Radio and energy model is the same as radiomodel in [2], which is called first radio model.

3.2 Setup Stage1. CH selectionIn addition to the factors that EECHS algorithm is uti-

lized in the cluster head selection process, two other fac-tors that are ignored in this algorithm will be added to the





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previous set, although they have significant impact onenergy consumption.

The first factor is the minimum energy required. If thenodes remaining energy is not sufficient enough to sendthe aggregated data to the Base Station, then a flag varia-ble called MER (Minimum Energy Required) will be tak-en as 0. And if the remaining energy is sufficient, then itwill be taken as 1.Considering the additional factor MER with all three fac-tors as in [2] the modified threshold T(n) becomes:

)]()()(1()([

mod1

)( iMERrdivsiDiE

prp

pnT

(4)

This factor guarantees that if it doesnt have enough en-ergy for operation as a cluster head, but it can be operatedon the network as an usual node for a while doesnt be-

come a cluster head.Another factor is the distance between cluster heads inthe network. In order to prevent the congestion of clusterheads in a particular area, the distance between the CHscannot be less than d (d is an ideal radius, and its calcula-tion is given by (5) ), so it can ensure that the CHs will notbe assigned to a centralized location. [8]

k

yxd

(5)

Where x is the length of the sensor network , y is thewidth of the sensor network, the value of is 3.14 , k isthe number of CHs in the sensor network, the value of is between (1, 2), here we select 1.1.

Fig. 1. The distribution of nodes.

In the process of CH selection, CHs will broadcast theadvertisement messages, when other nodes receive themessages, they will calculate the distance from the signalstrength of the messages, and record the minimum value.If the value is greater than d, this node can turn into CH,otherwise, this node will not. As shown in Fig.1, two

nodes 21 and 47 have been acting as CH in the network.All nodes in the two circular areas have lost their eligibil-ity to turn into CH, as nodes 7, 15, 41, 68, 72, 94.The process of CHs selection is shown in Fig.2

Fig. 2. CH selection process.

2. Cluster FormationIn the process of CH selection, CHs will inform all nodesthat act as non-CH in this round by sending CH broadcastmessage. In order to avoid the collision of individualmessages, the CSMA mechanism is used to send broad-cast messages. The broadcast message is a very smallmessage including the nodes ID and a header that distin-guishes this message. Each non-CH node determines thedistance to CH node based on the received signal strengthof the broadcast message. In order to reduce the energyconsumption that communicates with CH, non-CH willchoose the nearest CH to join. After each node has decid-ed to which cluster it belongs to, they must inform the CHnode that it will be a member of the cluster by sending ajoin request message to the chosen CH using CSMAmechanism. CH node confirms the members of this clus-ter according to the join request messages that received.When all non-CH nodes are finished to join the cluster,CH will produce a slot table based on the members of thecluster using TDMA mechanism. At the same time, CH

will get a cluster channel based on the sequence of be-coming CH. In addition to these cluster channels, the im-proved protocol also assigned a common channel fortransmitting the control information in cluster setup stage

Y

Y

Y

Y

N

N

N

Node generates a random

number betweenzero and one.

This node serve as

CH and send

broadcast message

Measurement of the distance of node

from LMA and determination

of the farthest node to LMA

LMA placement in

the specified location

HasThe node been a CH

during this loop?

Number

of received broadcastmessage < k

The beginningof CH selection

Is this

number less than threshold

of T(n)?

Is the

distance between cluster heads

more than d?

This node can

not be a CH

CH selection

is completed

Nextnode

Nextnode

Cluster head

21

47

Member node

d

d

21

47

15

7

68

7294

41





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and the data between the CH and Local Mobile Agent.CH will send the message containing the slot table andcluster channel to each member of this cluster usingCSMA mechanism. The member node that received themessage containing slot table and cluster channel willdetermine to its transmitting data slot and transmittingdata channel based on the content of the message. Be-cause of using TDMA mechanism, each cluster membersends data in different time slot to avoid the data conflictwithin the cluster. The data transfer between the clustersusing different channels, so they will not influence eachother. At this point, the setup stage is completed and thesensor network enters the steady stage.

3.3 The steady stage

After setup stage, the sensor network will enter thesteady stage. In the steady stage, each non-CH sends datain the assigned time slot, using cluster channel. On the

other time, non-CH node will go to sleep in order to re-duce the energy consumption. The CH must be awake toreceive all the data from the member nodes in the cluster.Before CH receives the data that cluster members send,the CH must judge whether the working channel is clus-ter channel or not. If the working channel is cluster chan-nel, CH will directly receive the data, otherwise, the CHwill receive the data after switching the working channelto cluster channel. Once the CH receives all the data, itperforms data aggregation. After data aggregation andfusion which are performed by cluster heads, it is time forthe most important step i.e. sending data outside the clus-

ter.In LEACH data transfer phase, cluster heads send the

packages to the sink node directly as shown in Fig. 3.This aim is easy to be realized, but it is not suitable forlarge networks. In this case, we proposed an improvedprotocol and introduce how it works.

Fig. 3. Transmit style of LEACH.

When there are too many sensors in a large area, thenumber of cluster heads is also tremendous. So, we canmake these cluster-heads cluster like previous. Then thenew cluster-heads will be chosen, we can call them supercluster-heads. Now the super cluster-heads are used tosend data packages to the sink node. This can be de-scribed as follows in Fig. 4.c2 send packages to sink node with the help of c1.

Fig. 4. Transmit style of the proposed method.

But how do we choose the super cluster-heads? Asshown in the formula, we can draw a conclusion thatwhen is an obtuse angle (as shown in Fig. 5), it showsthat a2+b2


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by the average of neighbor nodes energy. In this way, theagent should be placed where the average of neighbornodes energy of that place is more than the previous lo-cation. If there are several locations with mentioned fea-tures, one of them will be chosen randomly.

Fig. 6. Distribution and transmit model.

Routing from a specified node to the Local MobileAgent includes two stages;

In the first stage, a node called forwarding node is se-lected that is in sender domain and has the least distancefrom the Local Mobile Agent. In the second stage of rout-ing, if there is a neighbor between the sender node andthe current forwarding node that its direction make ob-tuse angle with the two previous nodes, this node is nom-inated forwarding node. If there is no neighbor node withthese characteristics, transmission process occurs directly.This way goes on until the reaching of data to the LocalMobile Agent.

4 SIMULATION RESULTS AND ANALYSIS

The simulation environment is composed of 200 sensornodes and sensor nodes are distributed in a region of100m 100m randomly. Table 1 lists the simulationparameters.

Fig. 7 indicates the number of alive nodes in each threealgorithms. As you can see in the following figure, theproposed algorithm grantees the network coverage overtime more than the two previous methods. One of theconsiderable results in this paper is reduction of time dis-

tance between failing of the first and the last nodes atminimum. This way keeps network coverage until the lastmoments completely.

CONCLUSIONDue to the scarce energy resources of sensors, energy

efficiency is one of the main challenges in the design ofprotocols for WSNs. Our aim is to specify shortcomingsrelated to classical routing protocols and discuss someupdated algorithms which define new methods for pro-longing lifetime. In this paper we examined LEACH andEECHS protocols, then a new CH selection and multi hoprouting mechanism is proposed. We compared our algo-rithm with two other protocols. The simulation resultsshow that the proposed algorithm can effectively reducenetwork energy consumption and prolong the network

lifetime. In this study, the minimum distance betweencluster heads is fixed. This factor can be changed effec-tively by changing the network conditions. The findingsof this study will be utilized in future research.

Fig. 7. The network lifetime.

TABLE1SIMULATION PARAMETERS

Parameter Value

No. of nodes 200

Network size 100 m 100 mCluster Head probability 0.1

Initial energy of node 0.2 Joule

Node Distribution Randomly distributed

Data Packet 4000 bits

E elec 50 nJ/bit

mp 0.0013 pJ/bit/m4

fs 10pJ/bit/m2

d Farthest 84 m

The corrected path by proposed method

L

CH

Shortest path

LMA





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REFERENCES

[1] QU.Wei-Qing, Cluster head Selection Approach Based on

Energy and Distance, IEEE International Conference on

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[2] W.B. Heinzelman A.P. Chandrakasan, and H.Balakrish,

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[5] A.Azim and MM.Islam, Deterministic Cluster Head Se-

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an Conference on Electrical and Computer Engineering(CCECE), 2012.

[6] M.Arshad and M.Alsalem and F.Siddqui and N.Kamel,

Efficient Cluster Selection Scheme in Mobile Data Collec-

tor Based Routing Protocol, 4 th IEEE International Con-

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[7] S.H. Kang and T.Nguyen, Distance Based Thresholds for

Cluster Head Selection in Wireless Sensor Networks,

IEEE COMMUNICATIONS LETTERS, VOL. 16, NO. 9,

2012.

[8] Wang Yao, Liu Quanli*, Gao Guangen, An Improved

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Ali Seirafi received his B.S. degree in computer engineering(Hardware) from University of Najaf Abad, Iran in 2007 and M.S. incomputer engineering (Software) from PNU, Iran in 2013. He is cur-rently working as a lecturer and researcher in Electrical and Com-puter Engineering department of IAU, Lenjan Branch, Iran. His re-search interests mainly focus on wireless communication and net-work systems.

Mohammad Hadi Moazzamhas a PhD in Systems and Con-

trol Engineering. At present, he is an Assistant Professor at the Fac-ulty of Engineering of Payam Noor University, Tehran, Iran.

Farshad Kabiri Samani received his B.S. and M.S. degree incomputer engineering (Hardware) from university of Najaf Abad, Iranand university of Arak, Iran in 2007 and 2010 respectively. He iscurrently working as a lecturer and researcher in Electrical andComputer Engineering department of IAU, Lenjan Branch, Iran. Hisresearch interests mainly focus on computer arithmetic algorithmsand circuits, microprocessor architecture and VLSI hardware design-ing.




energy efficient routing protocol using local mobile agent for large scale wsns

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