Research On Reliable Multicast Technology Based On Network Coding

With the continuous development of communication technologies,applications on wireless networks are gradually increasing.Due to mutual interference between communication nodes in a wireless network,packets are partially lost when transmitted.Most applications require a reliable transmission over a wireless network,so how to ensure a reliable packet delivery is a critical issue.In a wireless network,the transmitting node sends a batch of packets to the receiving node,and the receiving end feeds back the packet receiving situation to the transmitting end,and the transmitting end determines the packet that is not successfully received according to the feedback information of the receiving end.The main content of this paper is how to retransmit the packets that the receiver does not receive successfully on the basis of network coding,so that the receiver can receive all the packets completely.In this paper,different coding schemes are used for optimization.The optimized content minimizes the total number of retransmissions at the transmitting end,minimizes the delay caused by the excessive dimension of the coding matrix,and minimizes the delay caused by the excessive dimension of the decoding matrix.The main work of this thesis is embodied in the minimum group segmentation reliable transmission algorithm,the fixed length sliding window group segmentation algorithm and the variable length sliding window reliable transmission algorithm.The existing minimum group segmentation reliable transmission algorithm is analyzed.Finally,the algorithm is simulated.The simulation results show that the algorithm can reduce the total number of data transmitted by the sender,which can effectively improve the reliability of the wireless network.Although the minimum group segmentation reliable transmission algorithm can reduce the total number of times the transmitting end transmits data,if the amount of data transmitted at one time is too large,the encoding matrix dimension will be too large,which will bring about coding delay.In order to solve the above problems,a fixed-length sliding window group segmentation algorithm is proposed.You can set the size of the sliding window,send all the data in batches,and use the minimum group split reliable transmission algorithm for each batch of returned information.Finally,the algorithm is simulated.The simulation results show that the algorithm can effectively reduce the total number of retransmissions at the transmitting end and reduce the delay.The algorithm is suitable for use in environments with poor network performance.Considering the delay caused by the excessive dimension of the decoding coefficient matrix in the transmission process,a reliable transmission algorithm of variable length sliding window is proposed.Based on the current bit error rate and packet length,the algorithm calculates how many packets should be sent for each batch of multicast.After each batch of unencoded packets has been sent,the encoded package is sent(all packets of the batch are XORed).Since the probability of a single packet error and complete success is dominant in each batch,the receiving end can decode the lost packets according to the encoded packet.Finally,the algorithm is simulated.The simulation results show that the algorithm can effectively reduce the total number of retransmissions at the transmitting end and reduce the decoding delay.The algorithm is suitable for use in environments with good network performance.