Studies Of Spatial Self-interference Cancellation In MIMO Full-duplex Relays Systems

With the development of high-speed, wideband, ubiquity of wireless communication, the situation of the scarce radio spectrum resources becomes increasingly prominent. The paper further study FDR(full-duplex relay) technique,which as one of the key technologies of 5G. The traditional HDR(half-duplex relay) systems are gradually unable to keep up with the demand for wireless communication due to its low spectral efficiency. FDR systems attracts wide attention owing to its characteristic of wider coverage rage, higher system throughput and more effective spectrum efficiency. However, due to the sending and receiving messages on both sides at the same time and frequency caused leaks of signal from relay’s transmission to its own reception. And the serious loop interference make the system performance is greatly reduced. The goal of this article is to find a effective scheme of self-interference cancellation in the full-duplex relay system to improve the system performance.At the first, the paper shows the existing self-interference cancellation scheme and makes a simple classification of them. Then it focus research the zero forcing and maximum signal-to-noise ratio algorithms, and points out the zero forcing algorithm cannot be used in the interference channel with no full rank.Next based on the above study, the article proposes a new spatial scheme of self-interference cancellation, that is zero forcing scheme based on maximum signal-to-noise ratio. The idea of the new algorithm is an optimization model that build with the system SINR as the objective function,relay power limitation and the interference zero force conditions as constraint conditions. And by solving the optimization problem to obtain the matched filter solution. The through the simulation prove that this new scheme greatly improved the performance of the system.The capacity of bidirectional full-duplex relay system is theoretically two times of one-way full duplex relay system. But it also exits the self-interference. So studies the interference suppression scheme of the bidirectional full-duplex relay system is very valuable. This article on the basis of zero forcing algorithme and terminal power allocation realize the interference elimination.Finally, the simulation results show the system performance after the use of spatial method.