Research On Cooperative Retransmission Algorithm Based On Network Coding For Multi-hop Wireless Networks

In the system of Internet of Things and mobile Internet,wireless transmission is the most important transmission method,and then wireless transmission is applied to various fields.Multi-hop wireless network is a special wireless network.Due to the instability of the wireless link and the multi-hop factor in the process of data transmission,it often brings high channel error rate,which makes data easy to be lost or damaged.Therefore,in order to improve transmission success rate and transmission efficiency of the wireless channel,the retransmission technique has become one of the important methods to solve the above problems.In this thesis,the cooperative retransmission algorithm based on network coding were studied and analyzed deeply for multi-hop wireless network.Two noval algorithms are proposed to solve the problems of more retransmission times and longer transmission delays.The main results and innovations including the following two aspects:First,to solve the problem that the low utilization of coding opportunity,the waste of node transmits buffer space and low efficiency of coding combination selection in the existed cooperative retransmission based on network coding(CR-NC)algorithm,a dynamic continuous cooperative retransmission based on opportunity network coding(DCCR-ONC)algorithm is proposed.In the DCCR-ONC,an optimal cooperative node is selected a cooperative node according to the wireless link quality between node and previous-hop node and the wireless link quality between node and netxt-hop node;and after the first transmission of original data is finished,the original packet is transmitted using a continuously strategies with dynamic number of original data;a hash hamming method is used to search for the optimal coding combination to maximize the retransmission gain value each time.And theoretical analysis and simulation verification show that the DCCR-ONC algorithm has decrease retransmission times and complete time effiencicy.Second,for the problem of the high computational overhead,high complexity and larger completion time in current multi-point cooperative retransmission based on network coding,a multi-point cooperative retransmission based on hybird network coding(MCR-HNC)algorithm is proposed.In the MCR-HNC,selection of thecooperative sender set according to the the packet receiving state of each receiver and the communication coverage range.A hybrid code retransmission strategy is proposed according to the number of all original loss packets.For the partial original packet with less loss number,a random linear network coding retransmission strategy is used.For another partial original packet with less loss number,an opportunity network coding retransmission strategy is used.When selects the coding combination,the optimal coding combination selection problem is transformed into the maximum group search problem by combining the undirected graph.Theoretical analysis and simulation verification show that the MCR-HNC algorithm has decrease retransmission times and complete time effiencicy.At the end of the article,the full text is summarized and the further research direction is given.