Research On Forwarding Scheme And Optimization Algorithm For Two-way Relay Systems

With the rapid development of wireless communication technology,data transmission rate,network coverage and service quality need to be improved.Relay cooperative technology has received extensive attention because it can effectively combat fading in wireless channel,increase transmission reliability and improve the system performance of relay network.Under the background of resource scarcity,two-way relay system is of great significance because it further improve the utilization of relay system spectrum resources.Unlike common traditional relay forwarding strategies,amplify-and-forward(AF)and decode-and-forward(DF),this paper mainly studies the product-and-forward.The main work of this thesis is as follows:First,the product-and-forward(PF)based on three-node relay system is introduced and received signal to noise ratio(SNR)is analyzed.The receiving SNR is approximate under high SNR and the closed expression of outage probability and symbol error rate is derived based on the approximation.The simulation results verify the derived expression.Meanwhile,the simulation results show that the PF scheme can provide better performance than AF and has greater performance advantage.Then,the problems of power allocation and relay selection based PF relay system are investigated to utilize system resources reasonably and further improve system performance.First,the power allocation to maximize the achievable rate is proposed.To solve the problem,the objective function of power allocation is reconstructed based on the lower bound of the achievable rate,and then a near-optimal closed-form solution is provided.Similarly,the power allocation to minimize the symbol error rate is proposed,and a closed-form solution is provided by optimization theory.The maximum-minimum received SNR relay selection for PF two-way relay system is proposed and the bit-error-rate(BER)performance is analyzed.Theoretical analysis and simulation results show that this algorithm improves the performance of PF relay system,and the proposed scheme performs increasingly better than the conventional AF scheme as the number of relays increases.Finally,based on two-way relay system,two relaying forward schemes are proposed.The soft information forwarding and product-and-forward scheme's advantage is combined to propose a novel soft information forwarding scheme.The adaptive forwarding and product-and-forward scheme's advantage is combined to propose hybrid-decode-product-forward scheme(HDPF).This scheme not only reduces the power of noise by decode-and-forward(DF)scheme but also provides diversity gain by PF scheme.Simulation results show that the former proposed scheme can provide better BER performance,and the latter proposed scheme offers better performance than AF,DF and PF scheme.