Study And Design Of MIMO Relay System

MIMO relay system is a group of widely studied communication systems which combines MIMO and relay in recent years.MIMO relay system has been considered one of the key technology of future wireless communication systems since it can effectively improve the cell coverage and channel capacity.According to relay protocol,MIMO relay system can be divided into several classes:amplify-and-forward relay,decode-and-forward relay,demodulate-and-forward and compressed-and-forward relay.Among them,AF relay is considered as one of the promising MIMO relay technologies since it has a perfect trade between complexity and performance.Among the studies on AF-MIMO relay system,one of the key issues is the transceiver design.The transceiver design of MIMO relay system can be divided into two kinds of optimization problems according to the objective function of the optimal design problem.In the first kind of problems,the objective functions are functions of signal's mean square error and the constraints are transmission power.In the second kind of problems,the objective functions are transmission power and the constraints are signal's MSE.Since the signal's MSE reflects signal's quality,the second kind of optimization problems are also called QoS constrained optimization problems where QoS stands for quality-of-service.Compared with the first kind,the second kind of problems are currently much less studied.Meanwhile,the transceiver design of MIMO relay systems varies from different system models.Among the existing studies,the second class of transceiver design problems of MIMO systems with direct link have not been done yet.Therefore,we mainly focus on the study of QoS constrained problem of MIMO relay system with direct link.We firstly proposed a more complete MIMO relay system model compared with the traditional MIMO relay system model with direct link.Then base on the proposed system model,we proposed two QoS constrained iterative algorithms to optimize the system,both of which can effectively reduce the system total transmission power.The first algorithm is called multi-stream algorithm,which is based on KKT conditions,and has a better performance and lower complexity than the existing design of similar systems.While the second algorithm is called single-stream algorithm,which aims at single data stream case,and has a slightly better performance and a faster convergence but higher computation complexity compared with multi-stream algorithm.The single-stream algorithm is only available for single data stream case.We also perform tons of simulations.The simulation results showed effectiveness of both algorithms and also showed the advantage of the proposed system model.