Retransmission Scheme Based On Instantly Decodable Network Coding In D2D Communication

The core mechanism of network coding technology is the middle node of the network encodes the data received and transmits the encoding information to the downstream nodes to improve transmission efficiency and achieve the maximum network capacity.The encoding and decoding method of the instantly decodable network coding is simple,and the decoding time delay can be effectively controlled.D2D(Device-toDevice)communication is a short-distance direct communication technology under the control of a cellular system and it uses the authorized frequency band to realize communication,which can effectively save system resources.In order to improve the transmission efficiency,and in view of the characteristics of the instantly decodable network coding and D2 D communication technology,the retransmission scheme based on instantly decodable network coding is designed for D2 D communication networks,which will give full play to their advantages in wireless network retransmission and improve the network performance.First,a delay minimization retransmission scheme based on an instantly decodable network coding is proposed to solve the conflict problem when multiple devices cooperatively retransmit in D2 D wireless networks concurrently.This scheme makes full use of multiple devices cooperative transmission advantages in D2 D wireless network,combined with the packet receiving state information of each devices,taking all of the influence factors of delay into account,and then the packets with smaller incremental delay for each retransmission are selected to generate encoding packets to minimize the retransmission delay.At the same time,the devices conflict graph is constructed and the maximal independent set is searched in the graph.According to the encoding package weight value of each device,the maximum weighted independent set are selected as the concurrent cooperative retransmission devices to reduce the number of retransmission.The data of simulation results show that the proposed scheme can achieve the purpose of improving the transmission efficiency of the D2 D network.Secondly,to achieve the further decoding achievement an instantly decodable network coding retransmission scheme based on cache is proposed.According to the packets receiving state feedback matrix of each terminal in the D2 D network and the connection status of each terminal,a conflict graph model is constructed to select the concurrent cooperative retransmission terminal and the encoding packet in the same conflict graph model to reduce the total calculation of the system during the retransmission phase.At the same time,each terminal buffers the undecoded encoding packet received to make full use of its decoding gain in the subsequent retransmission process,and reduces the number of retransmissions.The simulation experiments results show that the cache-based instantly decodable network coding scheme can effectively reduce the number of retransmissions in D2 D networks with different connectivity.