The Performance Analysis Of Massive MIMO Multi-Pair AF Two-Way Relaying Systems

With the continuous development of wireless communication technology, high-speed data services and the widespread access demands are showing an explosive growth. The recent researches have shown that the base station deployed massive antennas array (hundreds antennas or more) takes lots advantages of performances. Massive multi-input multi-output (MIMO) technology becomes one of the core technologies in 5G wireless mobile communication for dramatically improving the data rates and decreasing the inferences among beamformings efficiently.In wireless communication, the relay technology becomes one of the key technologies of the next generation mobile communication for significantly improving throughput of system and cell edge signal coverage and reducing power consumption. The two-way relay transmission mode can transmit two data stream in the two time slot, and the mode of traditional one-way relay transmission in the two time slot can just achieve a data stream. Therefore, the two-way relaying transmission has higher spectral efficiency. Due to the advantage of the MIMO, the two-way relaying network combined with massive MIMO can dramatically improve system performances, such as spectral efficiency and energy efficiency.Firstly, a multi-pair massive MIMO amplify-and-forward two-way relaying system was put forward in this paper. In the two-way relaying system, K-pair single-antenna users communicated with each other by an intermediate relay station equipped with N antennas, where N 》 2K. Because the relay station could not achieve perfect CSI, the analyses in this paper was under imperfect Channel State Information (CSI). Moreover, adopting amplify-and-forward protocol in the relay station, the maximum ratio combining/maximum ratio transmission (MRC/MRT) and zero-forcing receive/zero-forcing transmission (ZFR/ZFT) beamforming pre-coding methods were used in this paper, then the signal to inference and noise ratio (SINR) at one user in one communication was derived, from which the asymptotic SE and EE could be obtained. Meanwhile, when the number of antennas at the relay station, the system performances, such as spectral efficiency, power efficiency and ergodic achievable sum rate were studied.Secondly, in order to save energy in two-way relaying system, a power scheme of different scale was proposed to ensure the system performance and reduce the transmit power of users and relay stations as far as possible. Meanwhile, utilizing MRC/MRT and ZFR/ZFT beamforming pre-coding methods, fixed and variable transmit power of pilot sequences, i.e., Pp with MMSE channel estimation were considered. When Pp was variable, it could perform power scaling schemes. The research analyses showed that, for a non-vanishing SINR with Nâ†' oo, the transmit power at each user and relay station could be both at most scaled down by 1/N with fixedPp, but could be further scaled down 1/N with variable Pp. It uncovers that the transmit power of users and relay station can both be significantly reduced without compromising the performance.Finally, the simulation results confirmed the validity of the analysis and the tightness between analysis and asymptotic results with fixed and variable Pp under imperfect CSI in this paper.