Research On Wireless Cooperative Relay Technology Based On Network Coding

As a new type of space diversity solution, wireless cooperative relay technology not only can overcome the limitations of multi antenna in the practical application, but also can obtain diversity gain, expand the system coverage. In recent years, network coding has been widely studied by the academic community because it can get the upper limit of the max-flow and min-cut capacity. Due to the broadcast characteristic of wireless communication channel,network coding is more suitable for cooperative communication to improve the spectrum efficacy and system capacity. Therefore, the wireless cooperative relay technology based on network coding become a research hot spot in the field of communication.In this thesis, the theory and research progress of network coding and wireless cooperative relay are introduced. Then different wireless cooperative relay transmission scenario based on the network coding are studied. The mainly work include: In two-way relay cooperative and multiple-access relay cooperative transmission scenario, three-time slot,two-time slot network coding as well as traditional four-time slot relay forwarding scheme which Amplify-and-Forward and Decoded-and-Forward protocol are in relay node. The outage probability and bit error rate are analyzed with simulation. Simulation results show that, the transmission scheme can be selected by different requirements.Then, in two-way multi relays system, an improved bidirectional optimal relay selection scheme is proposed for the problem that the original scheme can not guarantee the quality of two channels at the same time. By two relay selections, the received signal to noise ratio at all relays and the channel gain to resource are both considered in proposed scheme. Based on the optimal relay nodes, two power optimal allocation schemes are proposed, which are aiming maximum achievable rate and minimum outage probability. Simulation results show that joint optimal relay selection and power allocation can further improve the performance of the system.To solve the problems of traditional relaying protocol: may forward the incorrect decoded signals and low reliability of decision at relay node, mutual information forwarding schemes based on network coding is suggested in multiple-access relay cooperative transmission scenario. The relay node forwards not only the hard decisions from two source nodes, but also the reliability of mutual information. Simulation results show that the proposed scheme gets better bit performance than AF, DF and EF protocol in AWGN channel and Rayleigh channel.