The Prediction Of Link Expiration Time And Improvement Of AODV Routing Protocol Based On Group Mobility Model

Mobile Ad Hoc Networks have been applied widely in the goal places of special occasions, with the nodes mobile group and collaborative, and the dynamic changing of network's topology, Such as the rescue, meeting, battlefield and exploration. At present, most of the routing protocols of Ad Hoc networks are based on small change in network topology and random mobility model. They can't meet the routing protocols'performance characteristics based on group mobility model.Link expiration time between nodes can reflect the strength of the network topology changes and stability of the routing to a certain extent. Base on the Link expiration time, the routing protocol of the Ad Hoc networks with group mobility model are studied. The paper introduces nodes'mobility models and mobility prediction methods of Ad Hoc networks, and then the group model and Gauss-Markov group mobility model are detailed mathematical modeling. Base on the characters of Group Mobility Model, under the condition of non-replying on GPS to get nodes'relevant parameters, the paper propose an improved prediction mechanism for Link expiration time.In this paper, we point out the limitations of AODV protocol in the environment of network topology changes rapidly through in-depth analysis the process of AODV's routing establishment and maintenance. To solve this Problem, an improved AODV protocol is presented in this paper. In the process of route choosing, LET-AODV try to pick up the path having the longest Link expiration time in order to reduce the influence that topology change has brought. In routing maintenance, it takes the proactive handoff and proactive optimization strategy to enhance the ability to adapt dynamic changing of network topology and the stability of the path.The improved LET-AODV protocol proposed in the paper and AODV protocol are simulated on the NS2 network simulation software. Compared with the AODV Protocol, the result of the simulation indicates that LET-AODV protocol can reduce the repeating operation efficiently, as well as decrease the ratio of losing packages and delaying between terminal nodes so as to enhance the adapt ability of the routing protocol and network performance.