Research Of Interference Alignment For Multi-cell Massive MIMO Networks

With the increasing scarcity of spectrum resource and the explosive growth of exchanged data among equipments,faster transmission rate is required in future wireless system.Due to the severe co-channel interference in massive multiple-input multiple-output(massive MIMO)which is supposed to be one of the key technologies of the next generation wireless communication,interference alignment becomes a research hotspot.The interference alignment for multi-cell massive MIMO is studied in this thesis and algorithms are proposed from the aspects of reducing the complexity,improving the applicability and cutting down on the exchanged channel state information(CSI)among base stations.The research details and main contributions are as follows,(1)In the scenario of three cells and two users in each cell,a linear interference alignment algorithm is proposed for MIMO broadcast interference channel,which can align the inter-cell and intra-cell interference.According to the characteristics of the equivalent channel model based on the QR decomposition of the joint channel matrix,each user can achieve a degree of freedom(Do F)that is one-third of the channel space dimension with minimizing the interference leakage and zero-forcing.The simulation results show that the proposed algorithm can significantly decrease the complexity and guarantee system capacity.(2)For the interference network of multi-cell and multi-user massive MIMO,an iterative interference alignment algorithm(SLRINR IA)is proposed based on downlink interference alignment.The receiver interference suppression matrix is designed based on the ratio of the remaining and dominant interference as well as the interference channel's CSI,meanwhile,the transmitter precoding matrix is designed based on the principle of maximizing the SLRINR.Furthermore,the exchange of CSI among BSs is limited within a single cell,which can improve the SNR of MS and decrease the complexity of system.The simulation results show that the proposed algorithm can effectively suppress the inter-cell and intra-cell interference and converge quickly.(3)By introducing multi-cell clustering,clustering interference alignment algorithm is proposed.According to the interference strength among BSs,cells are formed into a group based on maximizing the intra-cluster interference.As a multi-layer interference management scheme,the SLRINR IA which extends to multiple dominant interferers is adopted within a cluster and simultaneously alternating minimization algorithm without iteration is applied for the inter-cluster interference.The simulation results show that the proposed algorithm can guarantee system capacity,reduce the amount of exchanged CSI and decrease the complexity of the whole system.