Research And Implementation Of TL-ODMRP Multicast Routing Protocol Based On Time Prediction And Local Recovery

Ad Hoc network is a special kind of multi-hop wireless network, which is independent on any fixed infrastructures, and each wireless network node is peer. Because of the flexibility and practicality of Ad Hoc network in recent years, and the rapid development of wireless communication technology, related researchers pay more and more attention to the Ad Hoc network investigation, in which the routing protocol and its performance analysis is becoming a research focus.With the increase of multicast technology development and application, more and more multicast protocols in Ad Hoc network are proposed, which can be classified into two categories:tree-based and mesh-based. ODMRP, abbreviated from On-Demand Multicast Routing Protocol, is one of the mesh-based multicast protocols. In Ad Hoc networks, as resource is limited, one of the biggest issues in Multicast protocol is the flooding of control message, which can lead congestion to network. Meanwhile in an environment of highly mobile nodes, the link may ocuur the breakage, which generally makes packet delivery ratio lower. If the source node repairs or rebuilds the interrupted link, it will increase many control messages, which incur the packet delivery ratio reduction and end-to-end delay increase.To solve these problems, the thesis presents a modified multicast routing protocol TL-ODMRP, which makes improvements in two ways. On one hand, during the route establishing process of the multicast routing protocol, if the link expiration time can be predicted, we can dynamically adjust the settings to send control messages, which avoid flooding messages and improve the packet delivery ratio. In the mechanism based on time prediction, the minimum link expiration time serves as route refresh time to reduce flooding control messages. On the other hand, after constructing the route, in the process of transferring data, the movement of nodes may cause the links interrupted. To solve the problem, we propose a mechanism called local recovery. According to the predicted expiration time of link mentioned above, the node which detects the breakage link will employ the local recovery mechanism, which can reduce the network control messages, improve packet delivery ratio and decrease the end-to-end delay.This thesis describes the TL-ODMRP multicast routing protocol in detail. Based on the expanded module of the NS2 network simulation software, we evaluate the TL-ODMRP and ODMRP multicast routing protocol, analyze and compare the experiment results. Compared with ODMRP, TL-ODMRP multicast routing protocol improves packet delivery ratio and decreases the route cost, which indicates the effectiveness of TL-ODMRP protocol.