Low Overhead Interference Alignment For Femtocell Networks

According to research, 70% of Communications business take place indoors,poor indoor wireless coverage and wireless networks interference are key factors that affecting network performance. Therefore, to enhance the quality of wireless networks, the challenges of networks coverage inadequate and interference management difficulties must be met. Femtocell communication system is an effective solution to the macrocell covering problem. However, the deployment of femtocell will increase network interferences, resulting in lower quality Services. So,how to restrain and eliminate the interference has important significance to improve the performance of communication system.As a new interference management strategy, interference alignment had attracted significant attention. The core idea of interference alignment is designing precoding matrix and zero-forcing matrix to construct interference signal lies in a subspace and been eliminated. Prior works prove that interference alignment can effectively suppress interference and approach higher capacity. This paper mainly analyzes the multi user interference alignment in a femtocell communication system,researches on reducing system overhead, the main work are as follows:Firstly, from the background of interference alignment and statue of research,this article analyses the significance of the study, and introduce the basic knowledge of femtocell, introduce the degree of freedom and research interference alignment deeply. At the same time, the traditional interference management strategy is analyzed, combined with dynamic power control, a dynamic power control based interference alignment algorithm is proposed. The interference alignment algorithm based on dynamic power control is reasonable to allocate the transmission power of the femtocell, and the interference leakage power can be reduced after the iterative calculation. Through simulation, the conclusion is proved.Then, a modified distributed interference alignment is studied. The distributed interference alignment can reduce the interference of the network step by step, but each iteration will generate great computational overhead. In order to cope with the challenge of high load computation overhead, this paper studies the modified distributed interference, which can reduce the computation overhead by optimizing the computation of the precoding matrix and the zero-forcing matrix. Based on thechannel estimation, the performance of the modified distributed interference alignment is analyzed, and the simulation results show that the algorithm has good performance.Finally, in order to reduce the feedback overhead, this paper studies the optimization method of the interference alignment feedback structure. Prior works found that a large number of channel state information is needed for the implementation of the classical interference alignment and distributed interference alignment, and the feedback overhead of CSI is one of the key reasons for the high load of the system. Femtocell receivers are used to process channel state information,change the feedback link and optimize feedback structure. The simulation results show that the optimized feedback structure can reduce the feedback overhead.