Research Of Interference Alignment For MIMO Heterogeneous Networks

With the rapid popularization of smart phones,single voice calls service can not satisfy people's needs in recent years.The mobile data services such as multimedia,web browsing,and instant communication is becoming more and more popular.The demand of the rate and capacity of the wireless communication is higher and higher.Therefore,how to reduce the consumption,and improve the efficiency of data transmission and communication system capacity using limited spectrum resources at the same time is a problem for the new generation of mobile communication.The heterogeneous network consisted of macro and pico base stations can effectively improve the system capacity,and meet the needs of the intelligent terminal communications of high density.So the study of the heterogeneous network is of great significance.Multiple input multiple output(MIMO)wireless communication technology can improve the quality of data transmission,and achieve high rate of data transmission.These advantages make the MIMO technology has been widely used in the wireless communication system.Because the number of antennas is large in the MIMO technology,it will introduce a lot of interference.It is urgently to use interference alignment technology,to make the interference signal received the receiver aligned into a smaller dimensions,and to make the dimension of the desired signal of the receiver to be maximized.Besides the system can realize the useful signal transmission without interference.Firstly,we made an introduction for the basic idea and the existing results of interference alignment(IA)technology,and then analyzed the application of interference alignment to a simple X network.Secondly,we designed an interference alignment scheme based on user grouping for a MIMO heterogeneous network which consists of a macro cell and arbitrary number of pico cells.According to the constraints obtained in the process of interference alignment scheme design,we derived the expressions of degrees of freedom of the system.And we carried out a simulation analysis.The scheme is suitable for scenarios of multiple pico cells with a macro cell serving multiple macro user,it can be transplanted conveniently.Lastly,for a general X network,we proposed an IA scheme based on the decomposition of matrices.In the design process of the scheme,the base stations only need to know part of the user's channel state information(CSI).Compared to the scheme where base stations need to know the global CSI,the scheme cost lower and is more feasible in practical application.The scheme is considered under quasi static channel.Grouping the users firstly and then we designed the scheme.Due to the particularity of the last group of users,we conducted two similar IA scheme design according to the base station know the last group of user's CSI or not.Then according to the comparison of the two schemes,we choose the scheme which have better performance as the IA scheme for the X network.During the process,we derived the limitation of maximum number of users,and the expression of greatest degrees of freedom.In addition,we analysis the feasibility of the scheme,and the available of the maximum number of users.Besides,we made simulation for the degrees of freedom of system compared with the interference avoid scheme,and analyzed the advantages and disadvantages of the scheme.