Research On Retransmission Scheme Based On Instantly Decodable Network Coding With Imperfect Feedback

Network coding allows network intermediate nodes to encode the data packets received and forward the encoding packets,to improve the effectiveness of network transmission.Among them,the stringent coding and decoding conditions of instantly decodable network coding,support the receiver decoding immediately,which can effectively reduce the system delay.There is a certain correlation between transmission effectiveness and feedback information reliability,and the loss of feedback information will cause the source to be unable to fully understand the reception status of the receiver,which will bring uncertainty to the selection of subsequent retransmission packets.In this paper,combining with the characteristics of wireless multicast network under imperfect feedback and instantly decodable network coding,the retransmission scheme based on instantly decodable network coding with imperfect feedback is studied in order to improve transmission efficiency and reduce system delay.Firstly,in view of the transmission delay problem of wireless multicast networks with imperfect feedback,a retransmission scheme based on instantly decodable network coding with imperfect feedback is proposed.In this scheme,the sender constructs a priority transmitting set by considering the reception state of each receiver and the packets loss rate of transmission link,and then the belief state of each receiver in the priority transmission set is calculated according to the partially observable Markov decision process.At the same time,the algorithm of code packet generation is optimized,and the model of instantly decodable network code graph is simplified to generate retransmission encoding packet quickly.The simulation results show that the proposed scheme can efficiently decrease the decoding delay and the completion delay compared with the traditional schemes,especially in the case of large number of receivers and packets.Secondly,aiming at the completion delay problem of wireless multicast networks with imperfect intermittent feedback,a completion delay minimization retransmission scheme based on instantly decodable network coding with imperfect intermittent feedback is proposed.In this scheme,the receiving state and the decoding delay of each receiver are considered comprehensively,a lossy and instantly decodable network coding graph model is established,and the receiving state of the destination receiver is estimated by graph-based update strategy.At the same time,according to the packet loss rate,request set and decoding delay,the completion delay of the destination receiver is calculated,the graph model is simplified by the fast generation algorithm,the sequence of sending encoded packets is optimized,and the encoding packet sending is selected to decrease the completion delay increment of the system.The simulation results show that the scheme proposed combined with the graph update strategy can efficiently decrease the system completion delay with different packet loss rates.