Research Of The Reliable Multicast Error Control In Wireless Mesh Networks

With the rapid development and the accelerating of commercialization process of theInternet, more and more applications are used in multicast because it has the advantage ofsaving network bandwidth and reducing load of server. Wireless Mesh Networks (WMNs) isone of the important technologies for the “last mile” broadband wireless access, withhigh-speed and low-interference, wide network coverage, flexible structure and so on. Theapplications of multicast in Wireless Mesh Networks are becoming more and more widely.But there is a challenge to the reliability of the multicast transmission because of wirelessnetwork itself with low bandwidth, high packet loss rate and poor stability.Therefore, theproblem to be solved is how to ensure the reliability of multicast transmission. Error control isone of the important methods to ensure multicast reliability.The error control protocols in MAC layer becomes the focus of the research because ofits short processing delay. Firstly, this paper analyzed the performance of the typical multicasterror control protocols in Wireless Mesh Networks, such as BLBP, LBLBP and HLBLBP. Theresults from the theoretical analysis and simulation showed that the above three protocols canensure the reliability, and HLBLBP is better than others in number of retransmission, channelholding time and average end-to-end delay.But these protocols exist the problem that the poorquality nodes affect the performance of the whole network. In order to reduce the number ofretransmission and network latency, this paper proposed a new protocol named CHLBLBP(Cooperative-Hybrid-Layer-BLBP), which was combined of the collaborative transmissionand forward error correction mechanism. In CHLBLBP, the data transmission was dividedinto two phases, the original sender transmitted packets in the first phase, and some relaystransmitted packets in the second phase to help the sender. The results from the theoreticalanalysis and simulation showed that CHLBLBP can improve the reception success rate of thepoor quality nodes through collaborative transmission, can reduce the number ofretransmission, and shorten the network latency, then improve the quality of the overallnetwork.For the multi-hop environment in Wireless Mesh Networks, with the increase of the number of hops, the route may select the poor quality channel, thereby increasing the errorcorrection times, which resulted in increased transmission times. So, with the improvement ofthe MAODV(multicast Ad-hoc on-demand distance vector protocol),it proposed the newmulticast routing protocol named MAODV-MT(Minimun number of Transmissions) which isbased on the minimun number of transmission. It improved the multicast routing mechanismto select the path from the multicast group leader to the current node which has a lowerpackect loss rate and a smaller number of transmission according to the real-time status of thelink.The simulation results showed that the MAODV-MT although slightly increased thecount of transmission hops, but it can effectively reduce the transmission times and reduce theend-to-end transmission delay.