Improvement And Implementation Of DSR Routing Protocol In Wireless Mesh Network

Wireless Mesh network is a multi-hop wireless network,which has the characteristics of no center,self-organization and dynamic network topology.It reduces the cost of network access and expands the scale of wireless network.But the frequent mobile nodes in some application scenarios will cause changes in network topology,which increases the complexity to design wireless Mesh network protocol and especially the factors to be considered in the design of routing protocol.Now,wireless Mesh networks use many routing protocols,such as AODV,DSR and other topology based routing protocols,and location based routing information such as LAR and GPSR.Routing criterion is the main basis for routing protocol,and its selection has a great influence on the efficiency of routing protocol.The most commonly used routing criteria in wireless Mesh network contains RTT,ETX,ETT and so on.ETX(Expected Transmission Count,expected transmission times)takes the average expectation send times of nodes transmit packets successfully as a metric of link state,then take the path that least expected transmission times as the optimal routing between nodes.It is very effective in reflecting the link state and reducing the cost of routing.It not only can greatly reduce the number of data transmission in the link,but also can greatly improve the link throughput.The ETX routing criterion periodically broadcasts the detection packet through the node,calculating the link forward direction transmit rate of df and reverse forwarding relay rate of dr,using the formula to calculate the ETX value of the link.When the nodes in wireless Mesh networks move frequently or have large motion speed,they will often cause changes in network topology.The routing chosen by ETX routing protocol may occur that nodes are not in communication with each other.Therefore,we need to improve this problem.Based on the ETX routing criter:ia which using DSR,exploiting Markov location prediction model,calculating the distance between nodes,then estimating whether the routing nodes selected by the ETX criteria are within the communication range of each other.In this paper,the motion rate and service rate of the node are changed on the NS2 simulation platform,comparing the performance of the network before and after the improvement.It can be concluded that:Compared with the origin DSR routing criteria,the improved ETX routing criterion distinctly reduces the packet loss rate and the average delay,and evidently improves the network throughput,That is to improve the performance index of the network from all aspects.