Research On HARQ Technology Based On Network Coding

Hybrid automatic repeat request (HARQ) technology which combines the advantage of forward error correction (FEC) and feedback repeat request (ARQ) can improve the system reliability by using retransmission and error correction mechanisms. Employing relay cooperative technology in the wireless communication network can provide extra diversity gain, which can improve the overall network performance. This thesis studies the network coding based on HARQ schemes, with emphasis on the combination of the HARQ technology with the LDPC network codes to improve the throughput of the wireless relay network.A HARQ protocol based on network LDPC codes is proposed for the multiple access relay network model where two users communicate with the base station with the assistance of the relay node. According to the base station's repeat request, the relay node encodes the two users'information with network LDPC codes and then forwards the coded information to the base station, which jointly decodes the signals received from the source nodes and relay node. Compared with the traditional HARQ protocol, the proposed cooperative HARQ protocol based on network LDPC codes can achieve better performance on the AWGN channel, and the throughputs of cooperative HARQ protocol are increased obviously.A HARQ protocol based on cooperative network is also proposed, which aims at the model where single user communicates with the base station with the assistance of the relay node. The relay node responses to the base station's repeat request, encodes the user's current frame information and previous frame information with network LDPC codes and then forwards the coded sequence to the base station. The base station adapts multi-user joint detection and joint soft decision into the received signal. Compared with the HARQ protocol based on network coding, the HARQ protocol based on cooperative network can achieve better performance on the AWGN channel.