Research On Network Coding In Two-way Relay Channel

Traditional wireless communication network can achieve multi-hop gain byemploying cooperative relay communication which realizes high-bandwidth andhigh-speed wireless transmission and improve network coverage performance.While in the case of multi-user, if the relay node only employs traditional workmode, system throughput performance will be decreased, which is a bottleneck toimproving system performance. This paper introduces the idea of network codinginto cooperative relay communication, and obtains throughput gain by doingnetwork coding operation on different user’s information packets which improvesthe performance of cooperative relay communication system.This paper applies network coding in two-way relay channel which is the mosttypical cooperative relay structure. First of all, the article describes the basicprinciples of network coding and structure of two-way relay channel model, reviewsencoding and Viterbi decoding process of convolutional code, states the concept ofsoft information and soft network coding, as well as two soft information quantizer--Lloyd-Max quantizer and equal probability output quantizer.Secondly, the paper derives theoretical performance of traditional relay schemeand network coding schemes in TWRC model, and gives simulation results underdifferent channel conditions. On this basis, channel coding is introduced toNCS-TWRC model. Firstly, CNCS-TWRC model which uses hard decision isanalyzed and its system structure is presented, and the influence induced byconfiguration of basic type or exchanged type of relay node on system performanceis discussed. After software simulation, it has been proved that CNCS-TWRC modelwith basic type of realy has better throughput and BER performance than that ofexchange type of relay, and those CNCS-TWRC models are superior to CTS-TWRCmodel in throughput performance, with a worse BER as the cost.Finally, this paper proposes two types of SCNCS-TWRC models. The first oneis a link-by-link model which employs SIHO channel decoder in relay node and thesecond one is an end-to-end model which performs channel encoding and decodingonly at the end nodes. Detailed system structure of these models are presented.Simulation results show that when using equal probability output quantizer and Lloyd-Max quantizer, the first type of SCNCS-TWRC model has better output inBER and throughput than that using uniform quantizer, what’s more, the end-to-endSCNCS-TWRC model outperforms end-to-end CTS-TWRC model in throughputbut has a worse BER performance.