I .INTRODUCTION:

Mobile Ad-hoc Network (MANET) [1] is a multi-hop temporary autonomous system which consists of a set of mobile nodes with wireless transceiver devices. It is used to meet the demand of emergency communications and military mobile communications, such as expeditionary operations, advance on the battlefield and rescue after earthquake or flood, etc.[2] In a MANET, no such infrastructure exists and the network topology may dynamically change in an unpredictable manner since nodes are free to move. As for the mode of operation, ad hoc networks are basically peer-to-peer multi-hop mobile wireless networks where information packets are transmitted in a store-and-forward manner from a source to an arbitrary destination, via intermediate nodes Mobile ad hoc networks (MANETs) are a rapidly evolving telecommunications technology. Their popularity is connected with their easy deployment and fast configuration. These features make them ideal for average users, Internet service providers, and reacting to emergency situations in which normal communication is impossible [3]. Traditional routing protocols [4, 5, 6] are proactive and they maintain routes to all nodes. Alternative reactive routing protocols [7, 8, 9] determine the route when they explicitly need to route packets.

The scope of this paper is to evaluate and compare the performance of CBR and TCP Traffic model using AOMDV routing protocol by varying pause time in MANET using NS-2 which is discrete event simulator.

II. AOMDV ROUTING PROTOCOL:

Ad-hoc On-demand Multi path Distance Vector Routing (AOMDV) protocol [10] is an extension to the AODV protocol for computing multiple loop-free and link disjoint paths. AOMDV shares several characteristics with AODV [11]. The routing entries for each destination contain a list of the next-hops along with the corresponding hop counts. All the next hops have the same sequence number. This helps in keeping track of a route. For each destination, a node maintains the advertised hop count, which is defined as the maximum hop count for all the paths, which is used for sending route advertisements of the destination. Each duplicate route advertisement received by a node defines an alternate path to the destination. Loop freedom is assured for a node by accepting alternate paths to destination if it has a less hop count than the advertised hop count for that destination. Because the maximum hop count is used, the advertised hop count therefore does not change for the same sequence number. When a route advertisement is received for a destination with a greater sequence number, the next-hop list and the advertised hop count are reinitialized. AOMDV can be used to find node-disjoint or link-disjoint routes. To find node-disjoint routes, each node does not immediately reject duplicate RREQs. Each RREQs arriving via a different neighbor of the source defines a node-disjoint path. This is because nodes cannot be broadcast duplicate RREQs, so any two RREQs arriving at an intermediate node via a different neighbor of the source could not have traversed the same node. In an attempt to get multiple link-disjoint routes, the destination replies to duplicate RREQs, the destination only replies to RREQs arriving via unique neighbors. After the first hop, the RREPs follow the reverse paths, which are node disjoint and thus link-disjoint. The trajectories of each RREP may intersect at an intermediate node, but each takes a different reverse path to the source to ensure link disjoint ness. The advantage of using AOMDV is that it allows intermediate nodes to reply to RREQs, while still selecting disjoint paths. But, AOMDV has more message overheads during route discovery due to increased flooding and since it is a multipath routing protocol, the destination replies to the multiple RREQs those results are in longer overhead.

SIMULATION ENVIRONMENT:

The simulations were performed using Network Simulator 2 [12] (NS-2.35) in Linux based Fedora 15 Operating System. The areas of simulation were 1000mx1000m, pause time 20, 40, 50 and 100 second. Number of nodes 50 and simulation time 300 second are taken for the entire scenario. NS-2.35 is chosen as the simulation tool because NS-2 supports networking research and education. NS-2 is suitable for designing new protocols, comparing different protocols and traffic evaluations. NS-2 is developed as a collaborative environment. It is distributed freely and is open source.

Table 1 Simulation scenario

Parameter	value
Seed	1.0
Simulation time	300 second
Simulation area	1000m x 1000m
Rate	1.0
Pause time	20,40,50 and 100 second
Packet type	CBR, TCP
Number of node	50
Routing protocol	AOMDV

III PERFORMANCE METRICS:

A. The Packet delivery ratio (PDR):

The packet delivery ratio (PDR) is defined as the fraction of all the received data packets at the destination over the number of data packet sent by the sources. PDR can be obtained with the formula mentioned below:

Packet Delivery Ratio = (total data packets received/total data packet sent)*100

B. End to End Delay (EED):

The packet end-to-end delay (EED) is the time of generation of a packet by the source up to the destination reception. The formula given under can be used to arrive this parameter:

Average end-to-end delay = (time received –time sent)/total data packets received.

C. Dropped packets:

Data packets are pieces of data that are disregarded by network sensors when they are overwhelmed. A dropped packet affects quality of service for network based applications like VOIP

IV RESULT ANALYSIS AND DISCUSSION:

In this section, we compare the two traffic models CBR and TCP using AOMDV routing protocol in same simulation environments with different pause times.

From the fig.1 the observable percentage of PDR in pause time 20 second is quite acceptable by CBR. The Average End to End Delay is observed very low by CBR as compare to TCP

From the fig.2 the observable percentage of PDR in pause time 40 second is quite acceptable by CBR. The Average End to End Delay is observed very low by CBR as compare to other results which are still is acceptable

From the fig.3 the observable percentage of PDR in pause time 50 second is quite acceptable by CBR. The Average End to End Delay is observed very low by CBR as compare to TCP

From the fig.4 the observable percentage of PDR in pause time 100 second is quite acceptable by CBR. The Average End to End Delay is observed very low by CBR as compare to other results which are still is acceptable.

In all above figure (1, 2, 3 and 4) we compare the PDR, End to End delay and dropped packet of all pause time taken for simulation results. CBR perform better than TCP, but while maximum pause time taken the dropped packet is poor in CBR Traffic model compare to TCP.

V. CONCLUSION AND FUTURE WORK:

In this comparative study of two different traffic models in MANET environment, certain considerable and realistic approaches of Ad hoc networks are systematically examined. CBR and TCP were made on the basis of attentive thoughts of related work in the same domain of Ad hoc networks. Similarly, for analysis purpose among the variety of available routing metrics, the options were prepared for packet delivery ratio (PDR), average end-to-end delay and Number of Dropped Packet. It was due to their classical and comprehensible differentiation in the context of routing measures. Using Ad-hoc On-demand Multi path Distance Vector Routing (AOMDV) we revealed that this protocol in CBR traffic model perform better than TCP in various conditions with less Packet Delivery Fraction, End to End Delay and appreciably less packet loss. As a future work we should compare other routing protocols, in order to analyze how effective and efficient these protocols are in response to TCP and CBR on MANET.

VI. REFERENCES:

1. D.B. Johnson, D.A. Maltz. “Dynamic source routing in adhoc wireless network”. Mobile Computing, 2001,263-270.

2. Ronghua Shi, Yongyan Deng” An Improved Scheme for Reducing the Latency of AODV in Mobile Ad Hoc Networks” IEEE 978-0-7695-3398-8/08, 2008.

3. Sarkar, S.K., Basavaraju, T.G. and Puttamadappa, C. “Adhoc Mobile Wireless Networks: Principles, Protocols and Applications”, ISBN 978-1-4200-6221-2, Hardcover, 312 pages, IEEE Communication Magazine May 2009.

4. C.E. Perkins, and TJ. Watson, "Highly dynamic destination sequenced distance vector routing (DSDV) for mobile computers," Proc. ACM Communications, Architectures, Protocols and Applications, vol. 24, pp.234-244,1994.

5. S. Sung, Y. Seo, and Y. Shin, "Hierarchical clustering algorithm based on mobility in mobile ad hoc networks," Lecture Notes in Computer Science. pp. 954-963.

6. C.-C. Chiang, H.-K Wu, W. Liu, and M. Gerla, "Routing in clustered multihop mobile wireless networks with fading channel," Proc. IEEE SICON'97 , pp. 197-221,1997.

7. C.E. Perkins, E. M. Royer, and S. Das, "Ad hoc On-Demand Distance Vector (AODV) Routing," RFC 3561, IETF, July 2003.

8. D. Johnson, Y. Hu, and D. Maltz, "The Dynamic Source Routing Protocol (DSR) for Mobile Ad Hoc Networks for IPv4," Internet experimental RFC 4728, February 2007.

9. O. Mazliza , O.Z.May, “Analysis of TCP-Reno and TCP-Vegas over AOMDV Routing Protocol for Mobile Ad Hoc Network”. ISBN 978-89-5519-146-2, Feb. 7-10, 2010 ICACT 2010

10. YuHua Yuan, HuiMin Chen, and Min Jia, “An Optimized Ad-hoc On-demand Multipath Distance Vector(AOMDV) Routing Protocol”, 2005 Asia-Pacific Conference on Communications, Perth, Western Australia, IEEE 0-7803-9132-2/05 October 2005., Pages 569-573.

11. S.R.Das, et al. “On-demand Multi-path Distance Vector Routing for AdHoc Networks”, ICNP2001.

12. David B. Johnson, David A. Maltz, Yih-Chun Hu, ”The Dynamic Source Routing Protocol for Mobile AdHoc Networks (DSR)”, draft-ietfmanetdsr-10.txt, july 2004.

Received on 17.10.2012 Accepted on 11.11.2012

Research J. Engineering and Tech. 4(1): Jan.-Mar. 2013 page 9-11