Research On Multi-cell MIMO Interference Suppression Techniques

With the development of wireless communication system,the user-service demands and the requirement for the transmission rate-and-quality of wireless communication system continue to grow.The introduction of Multiple-Input Multiple-Output(MIMO)technology in multi-cell system can significantly improve the system throughput.However,the inter-cell interference has become one of the main reasons that restrict the performance of multi-cell MIMO system.Therefore,for the scenario of inter-cell interference based multi-cell MIMO system,the contents of this thesis are summarized as follows:Firstly,this thesis mainly studies the problem of co-channel interference and uplink and downlink cross-interference in the multi-cell MIMO system,and investigates and analyzes the formation mechanism of these two inter-cell interference and some common interference suppression methods.In this thesis,we study interference suppression optimization schemes for multi-cell MIMO system,according to the basic principles of interference alignment technology.Secondly,to deal with the co-channel interference in multi-cell MIMO system,we propose a joint optimization scheme based on interference alignment for the transceiver precoding matrices.On the basis of the matrix chord distance theory,the precoding matrices matched with the best eigen-subchannels are selected at the transmitter.Moreover,the receiver matrices matched with the equivalent target channels are preferably selected at the receiver to achieve interference cancellation and improve the target signal strength at the receiver.Simulation results verify that the proposed scheme can improve the received signal strength and the throughput of entire MIMO system.Thirdly,to tackle the uplink-downlink cross-interference in multi-cell MIMO system,especially the cross-interference between base stations,a transceiver precoding iterative optimization scheme is designed together with power allocation,interference alignment and water-filling method.In this scheme,an iterative interference alignment algorithm based on the minimum weighted interference leakage power is used to optimize the design of the transceiver precoding matrices of the downlink cells,as well as the receiver matrices of the uplink cells.Then according to the water-filling method,the transmit power is allocated to the eigen-subchannels that owning excellent transmission quality,which can effectively suppress the cross-interference between base stations.Simulation results show that the proposed algorithm can improve the signal to interference plus noise ratio of the uplink receiver,and the uplink cell throughput and system throughput are increased as well.