Research On Joint Precoding Optimization Algorithms For Multiuser Two-way MIMO Relay Communication Systems

As the technical foundation of wireless communication,multiple input and multiple output(MIMO)technology uses the spatial diversity characteristics of multiple ant ennas at the source to provide significant performance to enhance channel capacity,and to improve the reliability of the system in data transmission.The combination of relay technology and MIMO technology can solve the problem of poor coverage caused by the distance problem in the process of information transmission,enhance the probability of receiving signals by edge users,and further improve the communication quality at the receiving end.In addition,some problems of transmission channel can be solved when precoding technology is introduced into MIMO relay system,suppress or eliminate signal interference,and improving the performance of the wireless communication system.In this paper,based on the research of relay as two-way transmission,a joint precoding optimization scheme is proposed for two different models of multi-user MIMO single relay,which can improve the performance of the system.First,In the scenario of two-way relay transmission mode,this paper proposes a novel joint precoding design algorithm for the two-way AF MIMO relay system with multiple transmitters / receivers.Under the power constraints of all nodes,the minimum and mean square error(MSMSE)design criteria are used to solve the non-convex optimization problem of the joint transmitting user,relay and receiving user,and the closed form The solution is difficult to directly calculate the optimal solution,for non-convex problems that cannot be solved directly,we need to transform them into convex optimization forms,and the semi-definite programming(SDP)design and second-order cone programming(SOCP)design are used to solve the sub-optimal problem.After that,the local optimization value of each sub-convex optimization problem is further solved through the alternating iterative method to achieve the purpose of optimizing all the node matrix variables.Finally,the simulation part will combine the CVX optimization toolbox to simplify the complexity of mathematical operations and solve the optimal value of the equivalent sub-convex optimization problem.In the simulation part,the sum mean-square-error(SMSE)and the sum-rate are used to show the improvement of the system performance.Last,in the scenario of two-way relay transmission mode,considering a transmitting / receiving multi-user MIMO relay communication including a direct transmission link,in order to ignore the problem that the direct transmission link between the transmitting end and the receiving end will cause system performance loss,an improved joint iteration Algorithm,in which Minimum and Mean Square Error(MSMSE)are optimized design criteria.After the objective equation is established,then for non-convex problems that cannot be solved directly,they need to be transformed into other form,and QR decomposition and quadratic constrained quadratic programming(QCQP)problems are used to solve the optimization values of the sub-problems.In the simulation part,the sum mean-square-error(SMSE)and the bit-error rate are used to show the improvement of the system performance.