Interference Alignment Technology In Multi-Cell Multi-User System

Interference suppression technology has been considered as one of the hotspots of wireless communication systems. The interference alignment (IA) technology, as a new way of interference suppression, has been attracted extensive concern, because it will not need to change the existing network architecture and compared to the conventional interference suppression method, it enables the system to get better performance, what’s more, using IA technology could make wireless communication system equivalent to a interference-free system. While the applications of IA has been attracted great interest of research institutions and even of communications equipment manufacturers. Considering the existing network topology, this paper focuses on the study of IA in multi-cell, multi-user system. In terms of applying the interference alignment to the cellular network or even to4G network, the work of this paper has a guiding significance.The main contents of this paper are as follows:First, investigating the origin, key performance indicators, the basic principle and the feasibility conditions of IA in depth. And then to enable readers to have a preliminary understanding of IA, we give some achievable schemes of IA in time, space and frequency domain. Secondly, we introduce the classical IA scheme in detail, mainly introduce distributed interference alignment that only needs local channel state information (CSI) and utilizes iterative algorithm, and interference alignment that with imperfect CSI, such as blind interference alignment. Finally, this paper focuses on research IA’s application in the multi-cell multi-user MIMO system, and propose a partial IA scheme that based on user grouping in multi-cell multi-user MIMO system. The main innovation of this thesis are as follows:1, users in one cell are grouped to several groups according to their location, and within the same user group, users jointly design the receiving processing matrix to align the strong interference from the same neighboring interfering cell, i.e., in one cell, part of the user align the interference from one of adjacent cells.2, after user feedback, in the view of BS in one cell, the interference at different direction to users in its neighboring cell will be concentrated in a few major interference subspace, i.e., achieving the effect of aligned to multi-subspace.3, When designing the transmit precoding matrix, the BS only eliminate the strong interference to users in its neighboring cells, thus, not only can reduce the leakage interference to neighboring cells, but could also reduce the need for the number of antennas.Simulation results show that, the partial IA scheme this paper proposed can not only reduce the number of antennas, and can also enhance the overall rate of each cell. Finally, the analysis shows that the proposed scheme can be applied to the large-scale cellular networks, and to the practical application of interference alignment technology, this scheme has some guiding significance.