Research On Two Way Relay Technology For Wireless Network Coding

Network coding breaked the traditional way of route node that is“storing-and-forwarding”,and introduced the new mode which supposed forwarding the coding combination of different information flows,it provides a new idea to solve the problem of communication.As we know wireless two-way relay system is a basic model in wireless relay networks.Because of the two-way data transmission flows,application of network coding in two-way relay system can obtain higher throughput compared to traditional relaying.Under this background,this thesis aims at combining network coding with two-way relay system,making a deep research on the problem of power allocation,relay selection and forwarding protocol,and then to analyze the performance of the system.The outline of this dissertation is described as follows:(1)Under the two cooperative scenarios of single relay and multi relay,the power allocation problem is studied for the AF-MABC protocol system.For the single-relay cooperative scenario,the optimal power allocation is achieved by using SNR balance technology.For the multi-relay cooperative scenario,the quantum genetic algorithm is introduced to find the optimal solution and reduce the complexity.And the simulation results show that the proposed power allocation scheme has better performance than the equal power allocation in the two scenarios.(2)The problems of relay selection and power allocation are investigated for the AF-MABC protocol system with asymmetric rates.The corresponding outage probability and the optimal power allocation values of each node are derived.On this basis,an optimal relay selection criterion based on minimum outage probability is proposed,besides the channel condition,the proposed scheme also takes each node’s output ability into consideration.Finally,the detailed implementation steps of joint optimization are summarized.And the simulation results show that the proposed relay selection scheme can significantly decrease the system outage probability,and the joint optimization scheme can improve the system outage performance.(3)For the asymmetric channel AF-MABC protocol system,the outage probability of four kinds asymmetric two-way relay channel with traditional three nodes network structure are analyzed,and simulation results show that downlink asymmetry is the worst case.Inorder to minimize the downlink asymmetry system outage probability,a new power allocation scheme based on channel state information is proposed.In this scheme,the power allocation value is a piecewise function of the symmetric factor.The node can adjust the transmission power adaptively according to the variation of the channel state.Simulation results show that the proposed power allocation strategy can improve the outage performance of the asymmetric two-way relay system.(4)For the TDBC protocol system,we investigate the relay forward protocol.Because of the NOR-MIF and the SC-MIF to adapt to different channel conditions.We proposed an adaptive forwarding scheme with varying channels which enables the dynamic switch between the two protocols in order to enhance the system performance.Simulation results show that under the proposed scheme,the bit error rate of the system is reduced.