Study On The Unicast And Multicast Routing Protocols In Mobile Ad Hoc Networks

Mobile Ad hoc Network (MANET) is gaining increasing popularity in recent years because of its ease of deployment. Ad Hoc Network owns some characteristics like self-organization, multi-hop and a frequently changed topology. MANET is useful when infrastructure is not available, impractical, or expensive.The uniqueness of Wireless Ad Hoc Network made it impossible to adopt the technologies utilized in traditional networks. So some new protocols and technologies need to be developed specially for Ad Hoc network on channel access, network security and routing. We focused on the routing protocols and algorithms of Ad Hoc network in this paper, and we chose the unicast and multicast routing techniques as our main research points. The main research works and results are listed as follows:In this paper, the unicast protocols are analyzed and compared against each other. Our study shows that AODV is better suited for mobile networks than other routing protocols. A major aspect of ad-hoc networks is that the nodes can move randomly, which requires the routing protocols in ad-hoc network to respond quickly to the network topology change in order to guarantee successful data packet delivery. But AODV can't find the link error and repairs the invalid path in time, which results in the longer end-to-end packet delivery latency and much more control overhead. The link state prediction algorithms by received data signal strength is proposed to resolve the problem. A link state prediction method can predict the exact link breakage time of an active path. In this thesis, two enhanced route maintenance algorithms of link state prediction method on AODV are proposed. The first one aims to find the to-be-broken link by link state prediction and then notify the corresponding source nodes before the breakage occurs actually. So the invalid paths are avoided to be used. The second one is called preemptive algorithm which is associating the proactive and reactive protocol. This algorithm not only finds the to-be-broken link but also takes response to repair the invalid path corresponding to the link in the local area. So the packet transmission is not affected by the broken link. Simulation results demonstrate that these two algorithms reduce the end-to-end delivery latency and increase the packet delivery ratio at the heavy traffic load with slight overhead increase.We provide a detailed description and comparison of Ad Hoc multicast protocols. By this, we conclude that ODMRP is a suitable protocol for MANET in the situation of node moving frequently. Its performance is well in most condition, but the network overhead increases drastically because of the numerous redundant data packet to be relayed, which in turn results in the network performance degration quickly. Two data forwarding algorithms are introduced in this paper to resolve this problem. The two algorithms are probability-based data forwarding algorithm which intents on reducing the probability of forwarding the data packet, thus the redundant data packets in the network are reduced accordingly.The first one uses the number of neighbor forwarder to determine the relay probability. Then the forwarding nodes relay data packet following the probability. The second one is used to determine whether the packet should be relayed or be discarded...