Research On Opportunistic Interference Alignment

Interference alignment (IA) has emerged recently as a brand new approach tomitigate interference and increase degree of freedom (DoF) of the system. The essenceof IA is compressing the dimension of interference signal to minimum, or forcing thedirection of interference signal fall into the predefined interference subspace to thegreatest extent, while the subspace of useful signal remains uncontaminated and is usedto transmit the useful signal. This article discusses the singular value decomposition(SVD) based opportunity interference alignment (OIA), which contains the main idea ofIA. Different from the iterative algorithms used by IA, OIA needs lower complexitywithin the multi-user to selection can achieve IA in multiple-input multiple-output(MIMO) multi-cell uplink networks.This article will focus on the outage probability (OP) and symbol error rate (SER)of SVD based OIA, under perfect and imperfect channel state information(CSI).Moreover,a new user selection scheme is provided to improve fairness in userselection progress. Many researches on OIA are aiming at the user selection mechanismdesigning, reducing the computational complexity, and system rate while few onreliability or with imperfect CSI. The theoretical analysis of OP and SER with perfectCSI is given in Chapter2. Chapter3studies the reliability of OIA with imperfect CSI,which is closer to the actual scenario. In addition, the existing literature mostly selectusers based on the maximum rate, or the maximumsignal to interference plus noise ratio (SINR), while the case that due to the channelconditions, some users may cannot meet the requirements to be selected, in other words,fairness is rarely taken into consideration. So, Chapter4introduces the pricingmechanism to the user selection process, making the new user selection schemeeffectively improves the fairness of the selection process, and more users have a chanceto communicate.Firstly, the metric of the interference leakage of the SVD based OIA MIMO multi-cell uplink networks under the ideal and non-ideal channel conditions are calculated. Byusing the distribution of the smallest eigenvalue of a Wishart matrix from random matrix theory and order statistics, the distribution of the power of interference at thebase station is obtained.Secondly, the ordered successive interference cancellation (OSIC) is utilized toeliminate intra-cell interference at the receiver. Using the distribution of interferencepower, the distribution of SINR of the system is derived, and the expression of OP andSER of the SVD based OIA scheme are also deduced. Simulation results validate theanalysis. Compared to IA in the Signal-to-Noise Ratio (SNR) regime of0-25dB, OIAshares the similar performance. In addition, two important conclusions are drawn fromthe theoretical analysis:1) the diversity gain is d=1for an SVD based OIA scheme;2)the amount of antennas owned by the base station, which are for addressing the usefuland interference space, is more than the amount of the selected users is enough.At last, the pricing mechanism is added in the traditional user selection scheme toimprove the fairness of the user selection process, so that more users have theopportunity to be selected by the base station to communicate. The lower bound of OPis obtained when system achieves maximum fairness and simulation results support theanalysis.