Research And Implementation Of A Cross-Layer Routing Protocol Supporting High Dynamic Ad Hoc Networks

All the nodes in a Mobile Ad hoc Network(MANET)act as both terminals and routers.This kind of network can be quickly deployed without the need of fixed infrastructures.The capabilities of self-healing and self-adaption of MANET make them widely used in the fields of military and disaster relief.Since a MANET commonly uses the wireless channel as transmission medium,it features high mobility and the network topology maybe changes rapidly.Consequently,under this scenario,how to shorten the packet network delay and improve the successful packet delivery ratio becomes the research focus of the MANET's routing protocols.In the existing cross-layer routing protocols,the link state or packet delivery ratio is considered as the basis of routing,but they lacks timely prediction of the link state.The routing switch or repair will be performed until the route fails,which greatly weakens the overall performance and quality of the network.In order to solve these shortcomings,a cross-layer routing protocol LQAR with link awareness is proposed.Based on Time Division Multiple Access(TDMA),the LQAR calculates the link quality by the signal to interference plus noise ratio of the physical layer and the link transmission success ratio.Meanwhile the remaining capacity of the node and the queuing delay are incorporated into the routing metrics.Saving a primary path and multiple backup paths for each destination node not only enhances the stability and reliability of the route,but also implements load balancing of the network and shortens end-to-end delay.At the same time,a link quality prediction mechanism based on the current short-term state and past long-term state of link quality is proposed.According to the prediction result of link quality,the switching and local repair of routes can be started in advance,which shortens route convergence time under high dynamic networks.Because the performance of network layer is directly affected by the reliability of link layer,a slot collision and slot interference detection algorithm for TDMA is proposed.The slot table is detected by the link layer.If there is a slot conflict,it will be solved by the link layer.If there is a slot interference,it determines whether the route switching or repair needs to be performed according to the link transmission success ratio.This method further improves the adaptability of the protocol in the high dynamic network topology.Finally,the LQAR routing protocol is implemented and simulated on the OPNET simulation software.The packet delivery ratio,network delay and routing cost are considered as performance comparison indicators.Comparing with AODV-CLMP and DSDV at different node moving speeds respectively,the LQAR designed in the thesis can not only maintain a high successful packet delivery ratio,but also significantly improve network delay and routing overhead even though network topology changes rapidly.