Enhancing the Performance of Mobile Ad Hoc Networks with Internet Gateways

ACKNOWLEDGEMENT I would like to express my sincere indebt ness and gratitude to my thesis advisor Dr. Chansu Yu, for the ingenious commitment, encouragement and highly valuable advice he provided over the entire course of this thesis. Kalubandi and Wissam Chedid for their encouragement and feedback during the entire course of this thesis. ii ABSTRACT Mobile ad hoc networks allow mobile nodes to communicate with one another without the aid of infrastructure thus forming temporary networks on the fly. For such networks to be operational a special routing protocol has to be designed due to possibility of frequent node mobility. Each node in the network acts like a host as well as a router, thus forwarding data on behalf of other mobile nodes in the network. While such networks are gaining immense popularity, they are prone to scalability issues when the network size (number of nodes) increases, causing the path length between the source and destination to increase linearly. Hence a large number of intermediate nodes are burdened with the forwarding load imposed by other mobile nodes, drastically affecting the performance of ad hoc networks. In this thesis, a technique to enhance the capacity of ad hoc networks is implemented. The technique exploits the existing infrastructure by placing gateways at fixed locations in the ad hoc network. They are originally placed to provide Internet access to mobile nodes in an ad hoc network, but they can also be utilized to facilitate communication among nodes in the ad hoc network. Those gateways serve as relay nodes, thus taking responsibility of relaying most of the burden (packets) imposed by the mobile nodes in the network. The presence of such gateways is transparent to the mobile nodes and hence the ad hoc routing protocol does not require any complex modification. While it is not surprising that those gateways improve the MANET performance significantly, the main theme of this thesis is to analyze the performance gain quantitatively so that a network designer can decide on the number of gateways as well as the location of gateways in the MANET. iii The technique is implemented and simulated based on the Qualnet simulator with Ad hoc On-demand Distance Vector (AODV) protocol as the underlying ad hoc routing protocol. The simulation shows that the capacity of ad hoc networks increases significantly with the introduction of the proposed gateway.