Research On Interference Alignment In Wireless Cellular Systems

Interference Alignment(IA) is a remarkable technique for the wireless sys-tem to achieve higher capacity than previously believed. The key for IA is to align the interferences at the receiver into the fewest possible spatial di-mensions to maximize the number of interference-free dimensions for desired signals. In this paper, we first give a short show on the basic of interference alignment, and then consider the scheme that can be easily used in practice. Furthurmore, we consider the scheme with limited feedback to reduce the link consumption and the scheme with opportunistic scheduling. The main contri-butions contain:Firstly, we propose an iterative scheme to design the precoding and decod-ing matrices iteratively. At the transmitter, we design the precoding matrices to reduce the leakage interference for the undesired receivers, the decoders are designed for further reducing the interference, and it is based on MMSE crite-rion. Distributed implementation and computational complexity is given in this paper to prove that the proposed scheme is better than the previous schemes.Secondly, we consider one kind of scheme with lower complexity, which means opportunistic IA (OIA). And by combining the OIA scheme and tradi-tional algorithm, we give the more practical schemes, which taking account of the complexity and system performance. Analysis on complexity and link over-head is considered is given in this paper to show the proposed scheme performs better than the previous schemes.Then, we study the limited-feedback-based interference alignment schemes, and propose two kinds of limited-feedback-based interference align-ment schemes in the MIMO-MAC. The former work is extended to the K-user cases and the performance is improved. For the first kind of limited feedback schemes, we consider to quantize the precoding matrix based on the IA solu- tion. For the second kind of schemes, the feedback value is obtained by con-sider IA measure directly. We also propose an feedback bits allocations scheme to improve the overall throughput. At last, we analyse performance and give a summary.Finally, The works of IA are summarized and the following works is fore-casted.