Uma Rathore Bhatt, Abhishek Dangarh, Akanksha Kashyap, Aishwarya VyasDepartment of Electronics &Telecommunication Engineering, Institute of Engineering & Technology

Devi Ahilya University, Indore -452017, India

Abstract— The advancement in wireless technology in the present era have created networks with low cost and low power consumption. One of such networks which exist is called as Mobile Ad-hoc network which is characterized by wirelessly connected nodes with frequent change in network topology. As the nodes are connected wirelessly a routing mechanism (routing protocols) is required for successful transmission of packets. Sometimes two or more nodes sending the information simultaneously results in collisions. Hence medium access controls (MAC protocols) are required for efficient transmission and avoiding collision. In this research workperformance of various attributes like throughput, average jitter, end-to-end delay for two Routing protocols (AODV and DSR) is analyzed by increasing the mobility of node, applying different MAC layer protocols (CSMA and ALOHA) and changing the type of scenario.Index Terms— AODV, ALOHA, CSMA, DSR, MANET, MAC

ACRONYMS

Abbreviations Full meaning

MANET Mobile area networkAODV Adhoc on demand distance vector Routing protocol DSR Dynamic source routingWRP Wireless routing protocolFSR Fisheye state routingDSDV Destination sequence distance Vector CSMA Carrier sense multiple accessMAC Medium access control

I. INTRODUCTIONThe Mobile Adhoc Network is described by random movement of mobile nodes in wireless scenario, in order to find the best possible path between sources to destination; routing protocols are used in wireless communication. Asthere is no dedicated path between the nodes a routingstrategy is helpful in exploring the shortest path. Thewireless networks are mainly composed of two types-infrastructure based network and Ad-hoc network. In case of infrastructure based networks there is a central station called access point (AP) which provide a wireless link between AP and a mobile data terminal equipment having antenna (can be a laptop or notepad computer).The routing procedure is also controlled by these access points, in such environment range of transmission is fixed. While in case of Ad-hoc networks the base station or access point is absent. Everynode present in the network performs all the functions of

base station and routing decisions are also taken by them.MANET or the mobile ad-hoc network is a flexible and self configuring network containing large number of wirelessly connected independent nodes. The most widely used routing protocol in ad-hoc network is AODV & DSR due to their reactive nature in topology change may. A lot of works on this network is done by researchers in order to have energy efficient routing protocols [1]. This paper further extends the research work in different scenario as discussed below.

1.1 PROACTIVE PROTOCOLS

A proactive routing protocol is table driven, it means each node has a table corresponding to every other node present inthe network and the shortest path from source to destination is found using these tables. In ad-hoc networks each node keeps on evaluating its table and consistently maintain it by continuously updating all the routing information’s [2].If due to mobility it may happen that the network topology changes or sometimes nodes get out of order or some link fails then the corresponding updates are propagatedthroughout the network in order to inform all the nodes regarding it, to change the information entered in their tableExamples of proactive protocols are Wireless Routing Protocol (WRP), the Destination Sequence Distance Vector (DSDV) and the Fisheye State Routing (FSR).

1.2 REACTIVE PROTOCOLS

The Reactive protocols are on demand routing protocols, it means whenever a node has any information to send to some other node then only it finds the most suitable path. For this the node initiates a route discovery process. In the route discovery procedure the source node broadcasts route request packets or RREQ packets to all the neighbor nodes. When a node that has a route to the destination receives the RREQ packet, a route reply (RREP) packet is created and forwarded back to the source. Each node usually uses hello messages to get information about their neighbors. When there is no reply of a hello packet then it means that a particular node is not working when a node discovers a link disconnection, it broadcasts a route error (RERR) packet to its neighbors, which in turn propagates the RERR packet towards nodes whose routes may be affected by the disconnected link. Then, the affected source can re-initiate a route discovery operation if the route is still needed. Compared to the proactive routing protocols, less control overhead is a distinct advantage of the reactive routing protocols. Hence an advantage of reactive

Performance analysis of AODV & DSR Routing protocols for MANET

2014 Fourth International Conference on Communication Systems and Network Technologies

978-1-4799-3070-8/14 $31.00 © 2014 IEEE

DOI 10.1109/CSNT.2014.56

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2014 Fourth International Conference on Communication Systems and Network Technologies

978-1-4799-3070-8/14 $31.00 © 2014 IEEE

DOI 10.1109/CSNT.2014.56

254

routing protocols over proactive ones is that, they have got better scalability. However, when using reactive routing protocols, source nodes may suffer from long delays for route searching before they can forward data packets[3]. Hence these protocols are not suitable for real –time applications.

1.2.1 DESCRIPTION OF REACTIVE PROTOCOLS

1.2.1.1 Ad-hoc on demand distance vector routing protocol (AODV)

AODV is an ad-hoc on demand distance vector routing protocol which is an on demand reactive protocol. It means whenever a node has some information to send then firstly it checks for a path. If the path exists then it sends the packets through it, but if not then a route discovery process is initiated. For this the route request packets (RREQ) are generated by the source nodes. RREQ packet contains the IP addresses of source and destination node and sequence number. Sequence numbers are used for loop prevention and as route freshness criteria. These RREQ packets (P) are broadcasted to all the nodes via flooding. Source node broadcasts the RREQ packets to all its neighbours. Each node, receiving P forwards to its neighbours. In this way it reaches to its destined node. As the RREQ packet is received by any node it sets up a reverse route entry for the source. Using the reverse route entry a node can send a route reply packet (RREP) to the source. These packets are sending by unicasting and not by flooding. Whenever an intermediate node receives the RREP it sets up forward path entry to the destination and hence a path is established for communication. In case of AODV a node gets information about its neighbour by exchanging hello packets. If no reply of hello packet is received then it means that node is out of order. If there is a breakage in the path then RERR i.e. route error packet is generated. It is propagated to all the affected destinations. When a source node receives RERR then it reinitiates the route discovery [4]. 1.2.1.2 Dynamic source routing (DSR)

DSR is dynamic source routing which is a reactive protocol or on demand protocol. Its routing mechanism is similar to AODV except it uses caches to store routes and it does not contain any periodic activity of transmitting hello messages. It utilises source routing means entire route is a part of the header. When a node wants to send a packet but it does not know a route to the destination, it initiates a route discovery by flooding route request packet (RREQ) [5]. RREQ packet consist sender’s and destination’s address. Each node appends its own identifier when forwarding RREQ packet. When the destined node receives RREQ packet then it acknowledges by sending route reply packet by reversing the route in header of RREQ and unicast it to the sender. On receiving RREP the source node caches the route included in

the RREP. When a source node sends a data packet to destination the entire route is included in the packet header hence the name source routing. Whenever any link of route is broken then the corresponding node generates RERR i.e. route error packet. If the node receives RERR packet then it searches its own cache to find an alternate route.

Fig 1.Types of protocols

II. PERFORMANCE PARAMETERS

• Average Jitter: Jitter is caused by network congestion, timing drift, or route changes and it is the variation in the time between packets arrival.• Average End-to-end delay: End-to-end delay indicates the time taken by a packet to travel from the source to the the destination. • Throughput: Throughput is the average rate of successful transmission of packet from source to destination.

Table1: Simulation parameters

Parameters ValueSimulation time 30secMobility mode Random WaypointChannel frequency 2.4GHzPause time 30secItem to send 100Item size 512bytesInterval 1sec

III. SIMULATION RESULTS

To analyse and simulate the different scenarios for comparison, the qualnet network simulator is been used. For this firstly the scenario is created then after simulation the results are analysed from the analyser option.

CASE1 - Comparison of AODV & DSR by changing thenode mobility.

In order to compare AODV & DSR on the basis of mobility,

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random waypoint mobility model is selected for a scenario having 80 nodes as shown in figure 2 and the speed of nodes is gradually increased from 5m/s to 20m/s.

Fig 2. Qualnet Scenario

From the graph of throughput verses mobility, in fig 3, it is seen that DSR outperforms AODV when mobility of source node increases. As the mobility increases, the position of nodes changes at a higher rate so the path for sending packets from source to destination also changes every time soDSR performs well because of the route cache availability.

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In fig 4, since the Intermediate nodes in DSR use the source route included in a packet to determine to whom a packet should be forwarded so after the certain limit of mobility of

nodes the average amount of time taken by a packet to go from source to destination decreases.In DSR the packet header size increases with the route length therefore the processing time at intermediate nodes increases the average variation in time between packets arrival caused by increasing mobility of nodes which is shown in fig 5.

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Fig 4. End to end delay over mobility of nodes

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Fig 5. Average jitter vs. mobility of nodes.

CASE 2- Comparison by increasing the number of nodes for a scenario having Single source and multiple destinations.

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Fig 6. Throughput vs. destination nodes

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In DSR a single route discovery may yield many routes to the destination, due to intermediate nodes replying from localcaches which help them to use the route for other destination.

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Fig 7. No. of packet drops vs. no. of nodes

Use of route cache in DSR can speed up route discovery and can reduce propagation of route requests due to which no. of packet drop is less in it as shown in fig 7.

CASE 3- Comparison of AODV&DSR by changing MAC layer Protocols.

In order to compare AODV and DSR by correlating the MAC layer protocols, a scenario is created having 5 different wireless subnets sending packets to a single destination node as shown in figure 8.

Fig 8. Qualnet Scenario

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Fig 9.Throughput vs. MAC layer protocol

The above comparison is done on a scenario having multiple wireless zones and single destination. That is way the packet traffic on this destination node is very high and the rate of collision is also increased so a medium access is required to improve the performance hence MAC layer protocol is considered for comparison.In case of CSMA, AODV outperforms DSR due to the amendment of intermediate node addresses in the packet header of the latter so the channel is busy for a longer duration of time and thus the efficiency of DSR decreases. Secondly, in case of ALOHA MAC layer protocol, the throughput of AODV is better than that of DSR since no carrier sensing takes place here hence as the path is established the packets can be sent easily.Another point that is to be noted here is that in the previous two cases DSR was performing better as compared to AODV but not here, this happened may be due to the type of scenario which is considered. In earlier cases only one wireless subnet was taken but here five different subnets are present in the scenario.

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Fig 10.Average jitter vs. MAC layer protocol

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Fig 11. End to end delay vs. MAC layer protocol

In the above graphs of jitter and end to end delay it is seen that both the values are lower for AODV as compared to DSR because in case of DSR due to the increased packet length.

IV. CONCLUSION

In this paper, analysis of AODV & DSR routing protocols is done to understand that which one performs well in which set of conditions. Focus is mainly done on the network parameters like throughput, end to end delay and jitter. By changing the mobility, scenario, no. of nodes & MAC protocol it is seen that as the mobility is increased DSR performs well. Secondly, in the scenario with multiple zones & single destination for CSMA & ALOHA MAC layer protocols, AODV is far better. In the scenario with single source & multiple destinations, DSR outperforms, Hence DSR sustains well in increasing mobility & traffic at nodes.

REFERENCES

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[3] Elizabeth Belding –Royer, Routing approaches in mobile ad hoc networks, in: S. Basagni, M. Conti, S. Giordano, I. Stojemenvoic (Eds), Ad Hoc Networking, IEEE Press Wiley, New York 2003.

[4] C. Perkins, E. Belding-Royer, S.Das, Ad hoc On-Demand Distance Vector (AODV) Routing, RFC 3561, 2003,.

[5] Salman Abdullah Alhamoodi, Krishna Kumar Raman, International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622, vol. 2, Issue 5, pp.144-148, 2012.

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