Research On Key Technologies Of Maj Orization Design For Opportunistic Routing In Wireless Mesh Networks

Wireless Mesh Networks (Wireless Mesh Networks, WMNs), with its high reliability, high-bandwidth, strong self-organization and self-healing, is being payed more and more attention. Wireless Mesh network usually adopts distribution method to maintain the communication between the nodes, and generally require multi-hop to forward the packets, the nodes in the network can be either as terminal node or as network routing node. The feature of wireless link dynamic, time-varying and loss result in poor wireless link quality and lower stability, which poses a challenge to improve the throughput of Wireless Mesh Networks and transmission reliability. Therefore, the research of efficient wireless routing protocol is one of the core issues in Wireless Mesh Networks. As a routing technology for wireless environment, opportunistic routing (OR) can adapted to the characteristics of the wireless link better, and improve the wireless network end-to-end throughput performance and data transmission effectively, so it quickly became one of the hot research direction in recent years.In this paper, a series of key technologies of the optimal design for opportunistic routing in Wireless Mesh Networks are studied in depth, including opportunistic routing routing metric design, algorithm design in multi-radio multi-channel environment, forwarding candidate node selection and sorting mechanism design as well as the design with encoding mechanism, The major innovative works of the dissertation can be summarized as follows:Firstly, throughput-oriented routing forwarder selection algorithm is proposed to establish constraint mechanism to forwarders selection, and we also analyze the optimal forwarders selection ability theoretically. Besides, we propose an Effective Successful Acknowledgement (ESA) mechanism which solves the problem of conflict between the packets effectively; ESA not only reduces ACK packet transmission time, but also inhibit the retransmission and copy transmission of the nodes. Simulation results show that the algorithm can select better forwarders, so there will be a big improvement to the throughput and packet transmission number. With the ESA mechanism, the ACK acknowledgment can achieve better performance of the average delay, average probability of replication and the average probability of transmission.Secondly, Multi-Radio Multi-Channel Opportunistic Routing (MRMCOR) mechanism is proposed. According to the characteristics of multi-radio mtlti-channel, we derive the End-to-End Optimal Channel Assignment Delivery Probability (EEOCADP) channel allocation algorithm. Then the best solution of finding the best channel allocation scheme which can achieve maximum end to end delivery probability is simplified to obtain the routing metric of Channel Assignment End-to-End Delivery Probability (CA-EEDP) to select forwarders and sorting. Finally, combined with the characteristics of multi-radio multi-channel mechanism, the routing protocol also introduces Reliable Acknowledgement (RA) mechanism. Simulation results show that compared with the the EXOR, the throughput performance and delay performance of MRMCOR are significantly improved.Thirdly, In view of the problems that present opportunistic routing metrics can’t accurately measure the maximumu transmission throughput from current node to destination node, this chapter adopts the Markov chain model to establish a set of transmission theory which used to estimate the maximum throughput performance of the opportunistic routing in wireless mesh network. Then we translate the problem of solving the Maximum Transmission Throughput (MTT) into the problem of solving the Minimum Transmission Number (MTN) in Markov chain theory. Finally, MTN-MTT forwarder selecetion and sorting algorithm is designed. From the simulation results, the results showed that the MTN-MTT algorithm can get better forwarders than ExOR, and the performance of average packet transmission delay, throughput and average packet transmission number is improved significantly contrast with the the ExOR.Finally, In view of the problem that present network coding opportunities routing protocol discard the damaged packets which waste the network resources, Frame-level Random Linear Coding Opportunistic Routing (FRLCOR) is proposed. In FRLCOR, node divide the data frame into a plurality of sub-frames before sending them, then encode (random linear coding) the sub-frames on the same position of different frames and sends them after forming a new data frame. Unlike other routing protocols with coding mechanism, in FRLCOR, even if the data received have been interferenced, the node will not discard them, but take good advantage of the non-interference sub-frames and sends the sub-frames after re-encoding them. Thus FRLCOR saves the network resources, improve the network performance. The simulation results show that compared with the MORE and tranditional routing protocol, FRLCOR improves the throughput, and greatly reduces the data transmission number.