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Abstract-Wireless sensor networks have gainedconsiderable attention in the past few years. They have

found application domains in battlefield communication,

homeland security, pollution sensing and traffic

monitoring. As such, there has been an increasing need

to define and develop simulation frameworks for carrying

out high-fidelity WSN simulation. For our simulation

based study we have considered three different scenarios

where a Adhoc routing protocol can be applied, namely a)

Phenom nodes with Mobility, Sensor nodes with mobilitywhile the SINK node is stationary b) Phenom nodes with

Mobility, Sensor nodes are stationary and Sink node is

stationary c) Phenom nodes are stationary, Sensor nodes

are stationary and SINK node is stationary. We have

considered AODV and DSR as the Adhoc routing

protocols for comparison in these scenarios.Simulation

has been carried out by using qualnet 5.0.2 simulator.

The matrices used for this simulation are packet Deliver

Ratio to SINK, Average End to End Delay to SINK,

Overhead, Throughput. Finally, through our analysis we

show the various intricacies that are associated with

Adhoc routing protocols when used in a sensor

environment. We also list the various problems we faced

while simulating the routing protocols in each of the

scenarios.

Keywords- Sensor networks, Adhoc routing protocols,

scenario study, simulation, AODV, DSR.

I. INTRODUCTION

A Wireless Sensor Network (WSN) contains

hundreds or thousands of these sensor nodes. These

sensors have the ability to communicate either among

each other or directly to an external base-station (BS).

A greater number of sensors allows for sensing over

larger geographical regions with greater accuracy.

Even though sensor networks are a superset of ad

hoc routing protocols, the routing protocols proposed

for ad hoc routing protocols cannot be used as it is for

sensor networks because of various reasons as given

in [1, 2]. But surprisingly we found out that there is

lack of simulation based study or research work [5] as

to show why ad hoc routing protocols cannot be used

in a sensor network environment. The main

contribution of this paper is that we have carried out a

simulation based study of ad hoc routing protocols to

understand their behavior when used in a sensor

network environment.

This paper is organised as follows. In the second

section 2, we give brief introduction of AODV and

DSR [6] routing protocol and in section 3 deals the

simulation setup and results obtained on the execution

of simulation. Finally we draw the conclusion in

section 4.

II. DESCRIPTION OF ROUTING

PROTOCOL

A. Ad-Hoc on Demand Distance Vector (AODV)

We give brief description of routing protocols andthe simulator, which we have considered for studying

the behavior of ad hoc routing protocols in WSN [7].

Adhoc On Demand Distance Vector (AODV) Routing

Protocol: AODV routing protocol uses on demand

approach for finding routes. In AODV the source

node and the intermediate nodes store the next hop

information corresponding to each flow for data

packet transmission. To find a route to the destination,

the source node floods the network with

RouteRequest packets. The RouteRequest packets

create temporary route entries for the reverse path

through every node it passes in the network. When it

reaches the destination a RouteReply is sent back

through the same path the RouteRequest was

transmitted. For route maintenance, every routingtable entry maintains a route expiry time which

indicates the time until which the route is valid. Each

time that route is used to forward a data packet; its

expiry time is updated to be the current time plus

Active Route Timeout. A routing table entry is

invalidated if it is not used within such expiry time.

AODV [5] uses an active neighbor node list for each

routing entry to keep track of the neighbors that are

using the entry to route data packets. These nodes are

notified with routeerror packets when the link to the

next hop node is broken. Each such neighbor node, in

turn, forwards the routeerror to its own list of active

neighbors, thus invalidating all the routes using the

broken link. The main advantage of this protocol is

that routes are established on demand and destinationsequence numbers are used to find the latest route to

the destination. The disadvantage of this protocol is

that the intermediate nodes can lead to inconsistent

routes [3].

III. DYNAMIC SOURCE ROUTING (DSR)

Dynamic source routing protocol (DSR) [4]: DSR

is an on-demand routing protocol. The major

difference between DSR and the other on demand

routing protocols is that, it is beacon less and hence

Scenario Based Analysis of AODV and DSR ProtocolsUnder Mobility in Wireless Sensor Networks

Varsha Sahni Pankaj Sharma Jaspreet Kaur Sohajdeep singh

CSE Dept. CSE Dept. CSE Dept. CSE Dept.CTIEMT CTIEMT CTIEMT Jalandhar, India

Jalandhar, India Jalandhar, India Jalandhar, India [email protected]

[email protected] [email protected] [email protected]

2012 International Conference on Advances in Mobile Network, Communication and Its Applications

978-0-7695-4720-6/12 $26.00 2012 IEEE

DOI 10.1109/MNCApps.2012.42

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does not require periodic hello packets. Consider a

source node that does not have a route to the

destination. When it has a data packet to be sent tothat destination, then it initiates a RouteRequest

packet. This RouteRequest is flooded throughout the

network. Each node upon receiving a RouteRequest

broadcasts the packet to its neighbors if it has notforwarded already or if the node is not the destination

node. Each RouteRequest carries a sequence number

generated by the source node and the path it as

traversed. A node, upon receiving a RouteRequestpacket, checks the sequence number on the packet

before forwarding it. The packet is forwarded only if

it is not a duplicate Route Request packet. Thus, all

the nodes except the destination node, forwards aRouteRequest packet during the route construction

phase. A destination node upon receiving the

RouteRequest packet, replies to the source node

through the reverse path the RouteRequest packet hadtraversed.

IV. SIMULATION SETUP

We have used Network Simulator Qualnet 5.0.2in our evaluation. The simulated sensor area is

501*501m rectangle. The size of each of the message

sent is 100 bytes. We have simulated the sensor

nodes from 50 nodes to 100 sensor nodes. We havekept hte simulation time constant at 100 sec. The

transmission and recieving power of 175mW and

initial energy of about 5 joules is made available. The

sensing energy for the phenom nodes is kept at1.75mW. The parameters used for carrying out

simulation are summarized in the table 1.

Table 1: Simulation Parameters

Parameters Value

Routing

ProtocolsAODV, DSR

MAC Layer 802.11

Packet Size 100 bytes

Terrain Size 501m * 501m

Nodes 50, 100

Data Traffic

TypeCBR

No. of Source50,60,70,80,9

0,100

Simulation

Time

100

sec.

TransmissionPower

175mW

Energy 5 Joules

Transmission

Range50 m

V.PERFORMANCE METRICS:

We have used the following metrics forevaluating the performance of two on-demand

reactive routing protocols (AODV & DSR):

A. PACKET DELIVERY RATIO TO SINK

It is the ratio of data packets delivered to thedestination to those generated by the sources. It is

calculated by dividing the number of packet received

by destination through the number packet originated

from source. PDF = (Pr/Ps)*100

Where Pr is total Packet received & Ps is the total

Packet sent. The greater packet delivery ratio is, themore realiable the network is.

B. AVERAGE END-TO-END DELAY

(SECOND) TO SINK:This includes all possible delay caused by

buffering during route discovery latency, queuing at

the interface queue, retransmission delay at the MAC,

propagation and transfer time.

(Time packet received Time packet sent)Total No. of Connection Pairs

Where Tpr is receive Time and Tps is sent Time

C. OVERHEAD

It is the sum of all the control packets sent by allthe sensor nodes in the network to discover and

maintain routes to the SINK node.

D. THROUGHPUTThroughput can be defined as the :

Node Throughput Data Transmission

Total Number of Nodes

A high network throughput indicates a small error

rate for packet transmission and a low level for

contention in the network.

Result Analysis

We have considered three scenarios to study the

behavior of ad hoc routing protocols in wirelesssensor networks.

A. Scenario One

In scenario one, we consider Phenom Nodes withMobility, Sensor Nodes with Mobility and SINK

without Mobility.

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Figure 1. Number of Nodes vs. PDR to SINK

In fig 1 we have mapped the PDR to SINK v/s

number of nodes. As can be seen from the graph DSR

is having the highest packet delivery ratio to the

SINK. There is an increase and decrease pattern

among the packets delivered to the sink. The decreasein the packet delivery may be mainly due to the

collisions caused by the flocking of phenom nodes

and sensor nodes together. If the sensor nodes arelittle far away from each other, while getting the

phenom packets in large number then there will beincrease in the packets delivered to the SINK.

Figure 2. Number of Nodes vs. EED to SINK

In fig 2 we have mapped the delay taken by thesource node packet to reach the SINK node in the

network. With both phenom nodes and sensor nodes

having mobility then the chances of link failure are

very much high. Link failures triggers new routediscoveries in AODV since it has at most one route

per destination in its routing table. The delay in

AODV is less than DSR since AODV finds the routes

only when it is needed. Also, as the number of nodes

increases, the time taken by the DSR to find theroutes to the SINK node in the cache increases. DSR

has longer delay because their route discovery

mechanism takes more time as every intermediatenode tries to extract information before forwarding

for reply.

Figure 3. Number of Nodes vs. Overhead

In fig 3 we have mapped the overhead occurring

in the network v/s number of nodes. The initial

overhead in DSR is high, but it decreases when the

nodes >80. This happens due to the cachingmechanism in DSR. Since DSR finds the routes

required to reach the SINK from its cache, the

overhead decreases. But as the number of nodes inthe network is large both AODV and DSR will have

more or less the same amount of overhead. The majorcontribution to the AODVs routing overhead is from

route requests, while route replies constitute a largefraction of DSRs routing overhead. Since DSR

replies to every request in source routing it causeshuge overhead than AODV.

Figure 4. Number of Nodes vs. Throughput

In fig 4 we have mapped the throughput to SINKv/s Number of packets. The initial throughput of DSRis more than AODV. But when the number of nodes

> 70, then the throughput of AODV and DSR slowly

starts to converge with each other. AODV has

difficulty in delivering the packets when the nodesare moving fast resulting in fewer throughputs than

DSR. In DSR the source routing reveals more

information in one route discovery than AODV.

Therefore, within the same time more routes arediscovered and so more packets are delivered. AODV

catches up when the mobility of the nodes gets lower.

This is because routes become more stable and so

eventually everybody can find all the routes it ever

needs.

B. Scenario Two

In scenario two, we consider Phenom Nodes withMobility, Sensor Nodes without Mobility and SINK

without Mobility.


In fig 5 we have mapped the number of packetsdelivered to the sink node. The packet delivery to

SINK of both AODV and DSR decreases as thenumber of nodes increases in the network. But the

number of packets delivered is low in DSR and startsto decrease once the number of nodes >70. But with

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high mobility, the chances of the caches being stale

are quite high in DSR. Eventually when a route

discovery is initiated, the large numbers of replies

received in response are associated with high

overhead and cause increased interference to data

traffic. Hence, the cache staleness and high overhead

together result in significant degradation inperformance for DSR in high mobility scenarios.

Figure 6. Number of Nodes vs. EED to SINK

In fig 6 we have mapped the delay taken by the

source node packet to reach the SINK node in the

network. The end to end delay of the DSR is more

than AODV when the number of nodes >70. DSR has

high end to end delay as its route discovery

mechanism takes more time since every intermediate

node tries to extract information before forwarding

the reply. Also, the routes become invalid due to the

phenom nodes movement. To adapt to this change,

each sensor node constantly monitors the links it uses

to forward the packets resulting in more end to end

delay.


In fig 7 we have mapped the overhead occurring

in the network v/s number of nodes. The overhead ofDSR is more than AODV when the number of nodes

>80. In DSR, a source node reaches the destination

by flooding the network with a route request (RREQ)

message. When a RREQ message reaches the

destination a route reply message is sent back to the

source, including the newly found route. This route

request and route reply messages increases as the

number of nodes increases leading to increasing in

the overhead of the network.


In fig 8 we have mapped the throughput to SINK

v/s Number of nodes. Throughput of both AODV and

DSR decreases as the number of nodes increases in

the network. But in DSR the decrease is very rapid

with the throughput of DSR decreasing to nearly 2%

when the number of nodes in the network is more

than 100.

C. Scenario Three

In scenario three, none of the nodes that is, the

phenom nodes, the sensor nodes or the sink nodes

have mobility.


In fig 9 we have mapped the number of packets

delivered to the sink node. The packet delivery of

both AODV and DSR decreases when the number of

nodes increases in the network. But the decrease is

severe in the case of DSR. In DSR, routing is done

through source routing i.e. the sender of a packet

determines the complete route from itself to the

destination, and includes the route in the packet. And

since the whole route is carried in each data packet,

intermediate nodes have the opportunity to inspect

the whole route and extract information from it

resulting in more delay to reach the SINK node. Alsothis results in traffic congestion leading to loss of

data packets. When the nodes are stationary the

caching mechanism does not have much effect in

improving the performance of DSR.

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But when the route is discovered DSR spends

more time in replying to other intermediate nodes,

since it will be having more information to the

destination node. The delay in DSR is more when the

number of nodes increases >70 in fig 10. But AODV

will be having one single route and packets will be

delivered through that route resulting in less delay.


In fig 11 we have mapped the overhead occurringin the network v/s number of nodes. As can be seen

from the graph the overhead for DSR increases

astronomically when the number of nodes in the

network is >90. But AODV is having less overhead.

As we have discussed in previous section DSR makes

use of source routing. If there is a link failure, then

many nodes will be affected. Furthermore, there is a

possibility that a node extracts route informationfrom a stale source route. Using the invalid route

information causes unnecessary overhead. DSR

always generates more RREP( route reply) and

RREQ (route requests) than AODV resulting in more

overhead. It has been reported in various ad hoc

research papers that the overhead decreases as themobility decreases. But we found a contrasting

situation where even after all the nodes are stationary,

there was no decrease in the overhead of DSR but it

increased proportionally.


In fig 12 we have mapped the throughput to SINK

v/s Number of packets. Throughput of both AODV

and DSR decreases as the number of nodes increases.But in DSR, the fall in throughput is severe and it is

less than 5%, when the number of nodes is >90. Even

though DSR by virtue of its source routing can

maintain caching mechanism it does not matter when

the nodes are stationary.

VI. CONCLUSION

In this paper we have studied the behavior of thead hoc routing protocols in wireless sensor networks

under various scenarios (ref Table 1). Through

simulation and our analysis, we show that DSR is the

routing protocol to be used in an environment like

scenario one and AODV is the routing protocol to be

used in environments, where scenario two and

scenario three are considered. Also we list the various

problems we had to face while simulating the routing

protocols in a sensor network paradigm. Our future

work includes designing an energy efficient routingprotocol for Wireless Sensor Networks. With all

these research challenges we firmly believe that wehave a very exciting time ahead of us in the area of

Wireless Sensor Networks.

REFERENCES[1] I. Akylidiz, W. Su, Sankarasubramaniam, and E.Cayrici, A

survey on sensor networks, IEEE Communications

Magazine, Volume: 40 Issue: 8, August 2002, pp.102-114.

[2] K. Akkaya and M. Younis, A survey of Routing Protocols

in Wireless Sensor Networks, Elsevier Ad Hoc NetworkJournal, 2005, pp 325-349.

[3] C.Perkins, E.B.Royer and S.Das,AdHoc On-Demand

Distance Vector (AODV) Routing, RFC 3561, IETF

Network Working Group, July 2003.

[4] E.M.Royer and C.K.Toh, A Revisew of Current Routing

Protocols for Ad-Hoc Mobile Wireless Networks, IEEEPersonal Communications Magazine, April 1999, pp. 46-55.

[5] Bertocchi, F et.al, Performance Comparison of Routing

Protocols for Ad hoc networks, In proceedings of Global

Telecommunications Conference, 2003, pp 1033-1037.[6] H. Jiang and J. Garcia-Luna-Aceves,Performance

comparison of three routing protocols for ad hoc networks,

In Proceedings of IEEE ICCCN 2001.

[7] Gowrishankar. S, T.G. Basavaraju, SubirKumarSarkar,

Issues in Wireless Sensor Networks, In proceedings of the2008 International Conference of Computer Science and

Engineering, (ICCSE 2008), London, U.K., 2-4 July, 2008.

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