Research On Bandwidth Delay Constrained Routing Algorithm In MANET

When emergencies such as natural disasters or terrorist attacks occur,the communications infrastructures are often destroyed and communications are interrupted.At this time,emergency communication networks can be constructed quickly by MANET technology which needs no fixed infrastructures and boasts fast and flexible networking.MANET is mainly used to send rescue site related image,voice,video and other data information to the rescue headquarters,and the transmission of such multimedia services impose high requirements on network bandwidth delay.Therefore,this thesis first discusses how to accurately predict the available bandwidth of link.Then,the prediction result is added to the routing protocol in the network layer to realize crosslayer routing design and provide certain quality of service(Qo S)guarantee for the transmission of multimedia services.Link available bandwidth estimation is of significance for multimedia transmission.Given problems of the present MANET network bandwidth estimation,such as occupying extra bandwidth,packet collision back-off,transceiver nodes monitoring channel asynchronous,so this thesis puts forward the passive bandwidth estimation algorithm based on channel monitoring.The algorithm starts from the transmission probability of the node's unit time slot,and the available bandwidth of the link is obtained by analyzing the collision of data packets,the contention back-off process,the synchronization of the transceiver nodes listening to the idle Channel and the control message overhead.The accuracy of the algorithm is further improved without additional bandwidth consumption.In order to find a path that meets the real-time traffic bandwidth requirements in a MANET network with limited bandwidth resources,a cross-layer routing algorithm with bandwidth delay constraint is designed in this thesis.Firstly,with the algorithm mentioned above,link available bandwidth is accurately estimated at the MAC layer,and the bandwidth consumption of the multi-hop link is also predicted.Then this information is added to routing protocol in the network layer.In the process of route discovery,abandwidth delay admission control is introduced.When the link available bandwidth meets the required bandwidth of a certain service flow,this service flow is allowed to access the network.Then the path meeting bandwidth consumption and possessing fewer hops is selected as the best route,and the rest as a backup route.The cross-layer routing algorithm adopts the idea of “first optimization and then stability”,which not only ensures the bandwidth delay requirements of the service flows,but also improves route robustness.Finally,NS2 is used to verify that cross-layer routing algorithm has good performance in throughput,delay and packet delivery rate,which can effectively guarantee the service quality of existing traffic flows and new ones in network.