Wireless Network Retransmission Scheme Based On Opportunistic Network Coding

Network coding allows to encode packets from multiple links and to forward at encoding node.Compared with the traditional "store-and-forward" transmission mode,network coding has taken multi-user information into account to recover lost packets.One retransmission of coded packet can simultaneously recover the requested packets of multiple sink nodes,which can improve the network throughput effectively.Taking network coding advantages,wireless network broadcast nature and packets loss into consideration,introducing network coding into wireless network retransmission is feasible.The simple encoding-decoding operation and low computation cost of opportunistic network coding make it widely used in network coding based retransmission.Strict instantly decodable network coding(SIDNC)and memory-based network coding(MBNC)are two typical opportunistic network coding based retransmissions ideaes.For the low utilization rate of coding opportunities in SIDNC,and large cache overhead in MBNC,multi-stage retransmission scheme based on opportunistic network coding(MSRS)is proposed.MSRS recovers different characteristic lost packets during in two stages,the packet with complete decoding characteristic(CDC-packet)can be recovered with SIDNC,the packet with incomplete decoding characteristic(IDC-packet)can be recovered with the assistance of MBNC.MSRS combines the technical advantages of SIDNC and MBNC,making MSRS take full use of the encoding opportunity of CDC-packets,fully discover the potential encoding opportunity of IDC-packets,and reduce the cache overhead.The simulation results show that MSRS can effectively decrease the number of retransmission,under different packet loss probability,MSRS has better retransmission performance,and has better stability under different network environment.To further completely analyze the delay performance of opportunistic network coding based wireless network retransmission,the coding characteristics both of SIDNC and generalized instantly decodable network coding(GIDNC)are analyzed.To minimize decoding delay,weighted search algorithm based on SIDNC(WSAS)and weighted search algorithm based on GIDNC(WSAG)are proposed respectively.Both the two algorithms use heuristic strategies to generate coded packets.The delay performance comparison among WSAS and WSAG is conducted.The simulation results show that the delay distribution of retransmission algorithm based on SIDNC is more aggregated,the delay distribution of retransmission algorithm based on GIDNC is more scattered.The average delay of GIDNC is superior to SIDNC,and the system completion delay of SIDNC is better than GIDNC.