Wireless Ad-hoc Network Overlay Network In A Reliable Multicast Protocol

Recently, the group communication of wireless Ad-Hoc network has become increasingly important. A great number of scenarios require mobile nodes to work together in form of groups. However, there is no fixed topology and central control mechanism in wireless environment. Wireless nodes are also restricted by transmission range and the inherent shortcomings of wireless channel. As a result, the data transmission in wireless Ad-Hoc network will suffer different levels of packet loss inevitably. In order to meet the reliability requirements for some practical applications, reliable multicast has become an essential method of communication in the wireless Ad-Hoc networks.In order to provide reliable multicast services efficiently, we propose a new overlay reliable multicast protocol LORM (Lightweight Overlay Reliable Multicast) based on Lightweight multicast protocol. In our algorithm, the topology building process and data transmission reliability of Lightweight have been improved. The protocol is implemented in Java programming language and a comparative experiment between Lightweight and LORM in real network environment is carried out.In this thesis, we introduce the characteristics of wireless Ad-Hoc networks and problems about multicast in such environment at first. Then a detailed presentation on different kinds of multicast protocol and loss recovery mechanism for Ad-Hoc Networks is given. As has been mentioned, we point out that there is no ideal solution which combines the advantages of other types of multicast protocol. After that, we conduct an analysis on the details of Lightweight protocol. A conclusion about the lack of optimization for network topology and recovery strategy for data transmission is then reached. With regard to such situation, we propose LORM protocol based on Lightweight. The protocol is implemented in overlay network to achieve lower running load and easier deployment. Through the"forward plus reverse"route, the construction process of network topology has been optimized. And in order to solve the transmission reliability problem, LORM combines the local recovery and source recovery altogether. Finally, we have built a real Ad-Hoc network to conduct comparative experiment. The results show that LORM significantly outperforms Lightweight in terms of packet loss rate and data delivery delay.