Improving Congestion Control for Performance Enhacemnet in MANETs

A Mobile Ad hoc Network (MANET) is a collection of mobile wireless nodes that can dynamically form a network without necessarily using any pre-existing infrastructure. Due to the potential ease of deployment, it is widely used in civilian & military applications. Its multihop connectivity allows the transmission range to be extended infinitely. While its intriguing features enable MANETs to be installed in many situations where traditional networks are unavailable, destroyed or impossible, they pose several problems which arise due to the shared nature of the wireless medium, limited transmission range of wireless devices, node mobility and energy constraints etc.The transmission control protocol (TCP) is one of the most popular and widely used end-to-end protocols for the Internet today. Unlike routing, where packets are relayed hop-by-hop toward their destination, TCP actually provides reliable end to-end transmission of transport-level segments from source to receiver. As TCP was designed for wired networks it considers that all packet loss in the network is due to congestion. Wireless medium is more exposed to transmission errors and sudden topological changes. So in this thesis work, we have analyzed the performance of three TCP variants on DSDV and OLSR, which were designed to improve performance in wireless networks. An ns-2 based simulation analysis of TCP Tahoe, TCP Reno, and TCP Sack and TCP Vegas on DSDV and OLSR under random early detection (RED) active queue management techniique is done. The effect of network density on the TCP variants with RED was studied. Experimental studies show that TCP vegas with RED performs better than the other variants and the performance of DSDV routing protocol under TCP-vegas much better than DSDV under TCP-vegas while RED-active queue management technique is used.