Research On Ad-Hoc Routing Protocols With Rapidly Changing Network Topology

During recent years, as the mobility of users continues to increase and complex industrial control systems or emergency systems develops in a high speed, ad-hoc network, especially mobile ad-hoc network has being gained more and more attention because of its flexibility and practicality.Routing protocol is one of the key parts in mobile ad-hoc network technologies. It’s also a most influencing factor for network performance. Most existing routing protocols are focusing on finding a route with the shortest distance, without considering the impact on quality of service brought by the stability of the route. These routing protocols are more applying to the environment which network topology changes slowly. For the networks with rapidly changing topologies, their performances are quite unsatisfactory.In this paper, the research is made on the characteristics of mobile ad-hoc network with complex structure and rapidly changing topology. Then a summary on existing routing protocols’strengths and weaknesses is given, with some explanation on typical protocols followed. Among the different species of routing protocols, the geo-based ones are proven to have a good scalability and development prospect. In addition, link expiration time (LET), which can be calculated from location information, can be used to select a route instead of distance to improve the stability of the route. Therefore, we analyze and implement a routing protocol LET-Ad-Hoc On-Demand Distance Vector (LET-AODV), which is proposed based on location information and the studies on on-demand routing protocols.At last, based on the analysis of the network topology’s change rate, series of simulation scene are designed, and simulations on LET-AODV and AODV protocol are made based on NS2platform. The simulation result indicates that, with rapidly changing network topology, LET-AODV protocol can decrease the ratio of losing packages and the ratio of link failure, so as to enhance the routing protocol’s reliability and the ad-hoc network performance.