Research On Self-interference Suppression In Full Duplex MIMO Relay Systems

Based on the increasingly tense situation of contemporary wireless communication spectrum resources,how to use limited spectrum resources to provide faster transmission rate,higher spectrum efficiency and greater network capacity is the key issue that next generation of mobile communication must face.Traditional half-duplex relay(HDR)technique transmits and receives signals in different time slots,resulting in low spectrum efficiency.FullDuplex(FD)relay technology has become one of hot topic of wireless communication,thanks to its high spectral efficiency and high capacity characteristics.However,its simultaneous transmission and reception of signals cause serious self-interference(SI)problem at relay node,greatly affecting the system performance.So how to effectively suppress the SI signal has become the core problem of full-duplex relay(FDR)system,which must be solved urgently.In this paper,we focus on the SI suppression of FD MIMO relay system,aiming at not only eliminating the SI,but also improving the capacity performance.The main work of this paper is listed as follows:(1)This paper analyze the system capacity of one-way/two-way FDR system with SI cancelled or not in the time domain and compare it with half-duplex relay(HDR)system.The simulation results show that the performance of the FDR system which eliminates the SI is always better than HDR system,and the performance of the FDR system which doesn't eliminate the SI is much worse than HDR system.It also proves that for two-way FDR system,the SI need to be suppressed not only in the relay node but also in the two source nodes.(2)The SI suppression of one way FD MIMO relay system is studied.Firstly,existing SI suppression schemes,including ZF scheme and SVD scheme is briefly introduced.Then,a new SI suppression scheme which is a maximizing capacity scheme based on SI zero is proposed for one-way FD MIMO relay system.The specific idea of this new scheme is establishing an optimization model and designing the transmission/reception precoding matrix pair to solve the optimization problem.The simulation results prove that the proposed scheme has an obvious advantage in system capacity over the existing ZF and SVD scheme.(3)The SI suppression of two way FD MIMO relay system is studied.This paper modifies the exisitting two-way FD MIMO relay system and proposes a new maximizing capacity beam selection scheme based on SVD decomposition for the modified two-way FD MIMO relay system.Unlike existing schemes which only suppress the SI at relay node,ignoring the SI at the two source nodes.The proposed scheme not only eliminates the SI at relay node,but also deals with the SI of two source nodes.The specific idea of this new scheme is first establishing an optimization model.Next,it designs the transmission/reception precoding matrix pair to suppress the SI at two source nodes.Then,the transmission/reception precoding matrix pairs are designed to eliminate the SI of relay.Finally,the optimal transmission/ reception precoding matrix pair is chosen from relay transmission/reception precoding matrix pairs which satisfy SI zero to maximize the system capacity.Simulation results show that the proposed scheme has better capacity performance than ZF scheme and HD.