INTRODUCTION:

A mobile ad-hoc network or MANET is a collection of Mobile nodes sharing a wireless channel without any Centralized control or established communication backbone. They have no fixed routers with all nodes capable of movement and arbitrarily dynamic. These nodes can act as both end systems and routers at the same time. When acting as routers, they discover and maintain routes to other nodes in the network. The topology of the ad-hoc network depends on the transmission power of the nodes and the location of the mobile nodes, which may change from time to time [1].

I. ROUTING PROTOCOLS FORMOBILE AD-HOC NETWORKS

As shown in Figure.1, routing protocols for Mobile adhoc networks can be classified into two main categories:

• Proactive or table-driven routing protocols and

• Reactive or on-demand routing protocols.

A. Table-Driven Routing Protocols

Table-driven routing protocols attempt to maintain consistent, up-to-date routing information from each node to every other node in the network.

The routing information is kept in a number of different tables and they respond to changes in network topology by propagating updates throughout the network in order to maintain a consistent the way the routing information is updated, detected and the type of information kept at each routing table.

B. On-Demand Routing Protocols

On-demand routing protocols were designed to reduce the Overheads in Table-Driven protocols by maintaining information for active routes only. When a node requires a route to a destination, it initiates a route discovery process

within the network. This process is completed once a route is found or all possible route permutations have been examined. Once a route has been established, it is maintained by a route maintenance procedure until either the destination becomes in accessible along every path from the source or until the route is no longer desired. Route discovery usually occurs by flooding a route request packets through the network. When a node with a route to the destination (or the destination itself) is reached a route reply is sent back to the source node using link reversal if the route request has travelled through bidirectional links or by piggy-backing the route in a route reply packet via flooding.

Fig. 1 Classifications of mobile ad hoc routing protocols.

OLSR, the most popular proactive routing protocol for ad hoc networks and OLSR version 1 (OLSRv1), has been standardized as an experimental RFC [2]. It is a link state protocol in which each node will send out HELLO and Topology Control (TC) messages periodically. It decreases’ the overhead of flooding link state information by requiring just Multi Point Relay (MPR) to forward the TC messages.

A routing table is maintained to keep the next hop information to all the possible destination nodes.

Most of the proposed multipath protocols are based on the single-path version of an existing routing protocol: AODV and AOMDV [6], DSR and SMR [7].

Most of these protocols are based on a reactive routing protocol (AODV [4] or DSR [3]).and, reactive multipath routing protocols improve network performances (load balancing, delay and energy efficiency), but they also have some disadvantages:

Route request storm: Multipath reactive routing protocols can generate a large number of route request messages. When the intermediate nodes have to process duplicate request messages, redundant overhead packets can be introduced in the networks [8].

Inefficient route discovery: To find node-disjoint or link disjoint paths, some multipath routing protocols prevent an intermediate node from sending a reply from its route cache [9]. Thus, a source node has to wait until a destination replies. Hence, the route discovery process of a multipath routing protocol takes longer compared to that of DSR or AODV protocols.

Compared to reactive routing, and the proactive routing protocols sends periodic control messages. Hence, several researchers consider proactive routing protocols as not suitable for ad hoc networks [5]

RELATED WORK:

Amr M. Hassain et. al.[10] the results analyze DSR and DSDV in idealized and realistic simulation environments on their performance. Another paper in reference [11] gives conclusion in mobile ad hoc network that reactive protocols i.e. AODV and DSR perform well when the network load is moderate.

F. Bertocchi et.al.[12] the reactive protocols are saving many resources like energy and bandwidth. It analyze that the proactive protocols perform well in heavy network traffic load.

Md. Anisur Rahman et.al.[11], the simulation was done in QUALNET simulator. The author wrote that AODV shows best performance in low and medium node density but in high node density both OLSR and DSR outperforms. The author wrote that DSR is selected for file transfers where delivery and throughput are critical factors. OLSR performs well in both low and high node density.

Mohamed I. Youssef [13]they presents that the DSR and AODV perform better when the network load is normal and if the traffic load is heavy the link state outperforms reactive protocol OLSR. In order to study the simulation affects on the performance another author has analyzed the DSDV and DSR .

Patil et al. [14] simulated the performance of AODV and AOMDV. The results showed that AOMDV exhibited lower routing overhead and end-to-end delay, and alleviate congestion related issues which are quite common in uni-path routing.

METHODOLOGY:

To compare two on-demand ad-hoc routing protocol, it is best to use identical simulation environments for their performance evaluation

Simulation Environment:

We make use of ns-2.34 which has support for simulating a multi-hop wireless ad-hoc environment completed with physical, data link, and medium access control (MAC) layer models on ns-2.

The evaluation of performance of MANETs routing protocols AOMDV, DSR and OLSR are based on following metrics Simulation environment is as follows:

Parameter	Value
Simulation Time	200S
Pause Time	4S
Terrain Area	500m x 500m
Traffic Type	Cbr , tcp
Maximum speed	5m/s
No. of Node	40,50,60,70

SIMULATION RESULTS

We ran the simulation environments for 200sec for Different no of node with constant pause time and maximum connections. Packet delivery fraction, average end-to-end delay and Normalized Routing Load and throuput are calculated for AOMDV, DSR and OLSR. The results are summarized below with their corresponding graphs.

(A)Packet Delivery Ratio /Packet Delivery Fraction (PDR/PDF)

In AOMDV the PDR increase at network size 40,50and but decrease at network size 60 and 70, so that is carry some fluctuation. In DSR the PDR increases smoothly with less difference as well as number of nodes decrease. As well as DSR gives better PDR as compare to AOMDV and OLSR. In OLSR the PDR decrease smoothly with small changes.

Figure 1: Comparison of the three protocols of MANETs with respect to PDF

(B) Normalized Routing Load

In AOMDV, NRL increases with less difference smoothly with respect to number of nodes increase .In DSR, NRL decreases with less difference smoothly with respect to number of nodes increase , so that is carry some fluctuation. In OLSR, NRL increase as well as number of nodes becomes large.

Fig 2: Comparison of the three protocols of MANETs with respect toNRL

(C)Average End-to-End Delay

In AOMDV gives a zigzag curve for End to end Delay. Decrease at network size 60 so that is carries some fluctuation. In DSR Average end-to-end delay decreases with large difference at network size 50 then decrease smoothly with small changes in node 50 with
respect to number of nodes increase , so that is carry some fluctuation. In OLSR Average end-to-end delay increase smoothly with small changes in node 50.

Fig3: Comparison of the three protocols of MANETs with respect to End-to-End Delay

(D)Throughput

In AOMDV Throughput increase with fewer changes with respect to number of nodes become large. In DSR decreases with some fluctuation. In OLSR Throughput provide approximate same result with little difference.

Figure 4: Comparison of the three protocols of MANETs with respect to Throughput Evaluation of Results for TCP Traffic in MANET

(A)Packet Delivery Ratio /Packet Delivery Fraction (PDR/PDF)

In AOMDV is gives a zigzag curve, PDR decrease smoothly with less difference as well as number of nodes increases. As well as AOMDV gives better PDR as compare to DSR, and OLSR .In DSR the PDR are fluctuated that is gives a zigzag curve, because at network size 40 and 50 that is decrease but also at network size 50 to 60 increases and for network size 60 to 70 again increase so we can’t says the PDR increase or decrease with respect to network size. In OLSR the PDR decrease smoothly with small changes.

Figure 5: Comparison of the three protocols of MANETs (TCP)with respect to PDF

(B) Normalized Routing Load

In AOMDV the NRL Once again gives a fluctuated result. In DSR the NRL decrease smoothly with less difference as well as number of nodes increases. In OLSR the NRL shows continuous progress with correspond to number of Nodes.

Figure 6: Comparison of the three protocols of MANETs(TCP) with respect toNRL

(C) Average End-to-End Delay

In AOMDV the average end to end delay Once again gives a zigzag result. In DSR the average end to end delay increases at the point 50, 60 and decrease at the point 40, 70.

Ones again in OLSR the average end to end delay shows continuous progress with respect to number of nodes.

Figure 7: Comparison of the three protocols of MANETs (TCP) with respect to PDF

(D)Throughput

In AOMDV the NRL Once again gives a fluctuated result. AOMDV Throughput decrease in 40 to 50 nodes and 50 to 60 then again decrease 70.In DSR just opposite to the average end to end delay, here Throughput low at the point 50, 60 and high at the point 40, 70. In OLSR Throughput efficiently decrease as well as number of nodes increase.

Fig 8: Comparison of the three protocols of MANETs (TCP) with respect to Throughput

CONCLUSION:

In MANET we have taken three routing protocols AOMDV, DSR, and OLSR and presented a comparative performance study among them for CBR and TCP traffic. According to our practical result we can say that in the CBR, DSR give better performance for packet delivery fraction and normalized routing load and AOMDV perform better for average end to end delay and throughput. But as well as performance of OLSR is very poor not reliable for packet delivery fraction and normalized routing load in MANET.

On the other hand we have taken three routing protocols in TCP traffic are AOMDV, DSR,OLSR and study the performance of these routing protocols. The result of our practical work done is the AOMDV perform better for packet delivery fraction, average end to end delay and throughput but not for normalized routing load. According to practical results the routing protocol AOMDV gives the better performance for TCP traffic in MANET. OLSR perform better for normalized routing load compare to AOMDV, DSR.

REFERENCES:

1. H.D. Trung, W.Benjapolakul, P.M.Duc, “Performance evaluation and comparison of different ad hoc routing protocols”, Department of Electrical Engineering, Chulalongkorn University, Bangkok, Thailand, May 2007

2. T. Clausen, P. Jacquet, IETF Request for Comments: 3626, Optimized Link State Routing Protocol OLSR, October 2003.

3. D.B. Johnson, Y. Hu, D.A. Maltz, IETF Request for Comments: 728,The Dynamic Source Routing Protocol (DSR) for Mobile Ad Hoc Networks for IPv4, February 2007.

4. C. Perkins, E. Royer, Ad-hoc on-demand distance vector routing, in: second IEEE Workshop on Mobile Computing Systems and Applications, 1999, pp. 90–100.

5. M. Tarique, K.E. Tepe, S. Adibi, S. Erfani, Survey of multipath routing protocols for mobile ad hoc networks, Journal of Network and Computer Applications 32 (2009) 1125–1143.

6. M.K. Marina, S.R. Das, On-demand multi path distance vector routing in ad hoc networks, in: Proceedings of the Ninth International Conference on Network Protocols, IEEE Computer Society, Washington, DC, USA, 2001, pp. 14–23.

7. S. Lee, M. Gerla, Split multipath routing with maximally disjoint paths in ad hoc networks, Helsinki, Finland, 2001, pp. 3201–3205.

8. Z. Yao, J.J. Jiang, P. Fan, Z. Cao, V. Li, A neighbour table based multipath routing in ad hoc networks, in: 57th IEEE Semi Annual Vehicular Technology Conference, vol. 3, 2003, pp. 1739–1743.

9. Z. Ye, S.V. Krishnamurthy, S.K. Tripathi, A framework for reliable routing in mobile ad hoc networks, in: IEEE INFOCOM, San Francisco, CA, USA, 2003, pp. 270–280.

10. Amr M. Hassain, MohamedI. Youssef, Mohamed M. Zahra, ‘‘Evaluation of Ad Hoc Routing Protocols in Real Simulation Environments’’, Electronics and Electrical Communications Department, Faculty of Engineering, AL-AZHAR University Cairo, Egypt.

11. Md. Anisur Rahman, Md. Shohidul Islam, Alex Talevski, ‘‘Performance Measurement of Various Routing Protocols in Ad-hoc Network’’.

12. F. Bertocchi, P. Bergamo, G. Mazzini, M. Zorzi, ‘‘Performance Comparison of Routing Protocols for Ad Hoc Networks’’, DI, University of Ferrara, Italy

13. Mohamed I. Youssef, Mohamed M. Zahra and Amr M. Hassan “Evaluation of ad-hoc Routing Protocols in Real Simulation Environments” The 2006 International Conference on Computer Engineering and Systems, 2006, pp. 288 – 293

14. Patil, V. C., Biradar, R. V., Mudholkar, R. R. and Sawant, S.R. On-Demand Multipath Routing Protocols for Mobile AdHoc Networks Issues and Comparison. International Journal of Wireless Communication and Simulation 2 (2010) 21–38.

15. “The Network Simulator - ns-2” ,available at http://www.isi.edu/ nsnam/ns/

16. The NS Manual (formerly ns Notes and Documentation), A Collaboration between researchers at UC Berkeley, LBL, USC/ISI, and Xerox PARC, May 9, 2010.

Received on 14.01.2012 Accepted on 13.02.2012

Research J. Engineering and Tech. 3(3): July-Sept. 2012 page 232-239