Research On Retransmission Scheme Based On Network Coding In Wireless Network With Imperfect Feedback

Network coding technology is an effective way to improve transmission performance of wireless network.Network coding technology allows the network intermediate nodes to encode the received packet,and then forward the encode packet to the next network nodes.Network coding can benefit multi-destination nodes through one transmission,which can improve the network throughput effectively.The broadcast characteristics of wireless network and the particularity of wireless network transmission media make it important to apply network coding technology to wireless network retransmissions.The effective transmission of wireless network is dependent on the feedback information of the sending node to some degree,if the feedback information from the receiving node is lost,which will cause the sending node cannot achieve the real accepting status of receiving node,and the wireless retransmission efficiency will be reduced.This thesis focuses on transmission schemes based on network coding with imperfect feedback in wireless networks.First,a retransmission scheme based on network coding with imperfect feedback(NCIF)for imperfect feedback scenarios of single-source and single-relay wireless multicast networks is proposed.The retransmission procedure with imperfect feedback is modeled based on POMDP(Partially Observable Markov Decision Process)theory.According to the system observation status and the maximum confidence degree,the source updates the system estimation status.And the source gives preference to select the encoding packet that can recover the earliest lost packet and the most lost packets according to the packet sending sequence.To increase the coding and decoding opportunity the destination can buffer the encoding packets that cannot be decoded.During retransmission procedure the source focuses on the destination requirements.In the same conditions the relay with higher transmission reliability is preferentially selected to improve the transmission efficiency.Simulation results show that the scheme proposed can effectively improve the retransmission efficiency compared with the traditional retransmission scheme with imperfect feedback in wireless multicast network.Secondly,to the problem of retransmission of multi-source multi-relay wireless multicast networks with imperfect feedback,based on the related research,a retransmission scheme based on network coding with imperfect feedback is proposed.The source node retransmission stage,according to the source node feedback state matrix to calculate the maximum confidence degree,and then update the estimate receive state of relay node and destination node.The source node retransmission the packet which is lost at relay node and the destination node according to the estimate receive state.Relay scheduling recovery phase,according to relay node feedback state matrix to calculate the maximum confidence degree,and then update the estimate receive state of destination node.Select a relay node retransmission code packet that can successfully transmit more linearly independent coded packets theoretically.Simulation results show that using the confidence status to estimate the receiving status of the destination node can effectively reduce the dependence of the sending node on the feedback information,and improve the retransmission effectiveness.