Research On Two-Way Full-Duplex Amplify-Forward Relay Systems

The current mobile communication system and wireless local area network(LAN) are either based on time-division duplex(TDD) or frequency-division duplex(FDD), in which the terminals are not allowed to transmit and receive simultaneously over the same frequency band, thus leading to loss of transmission and spectral efficiencies. However, the bottleneck is breached by the self-interference cancellation(SIC) technique, where wireless terminals to transmit and receive simultaneously are enabled over the same frequency band, offering the potential to double the spectral efficiency. With this benefit, the full-duplex radio integrating the two-way relaying has the potential to further improve the spectral efficiency, where two-way full-duplex(TWFD) amplify-and-forward(AF) relay systems attract wide attention due to its simplicity.In this dissertation, we mostly focus on the TWFD AF relay system under rigorous residual self-interference(RSI). The various performance of the TWFD single-relay system is analyzed, and the optimal power allocation and hybrid duplex scheme of the TWFD multiple-relay system is also studied, under sub-optimal relay selection. In addition, the impact of the RSI on the diversity-multiplexing tradeoff is researched. The specific contents of this dissertation are as follows:(1) Closed-form expressions for the outage probability of TWFD AF relay systems is achieved, over Rayleigh fading channel, and the n-order moment of end-to-end signal-to-interference-and-noise-ratio(SINR) is derived based on moment generating function(MGF). Moreover, calculation of ergodic capacity is simplified by using Jensen’s inequality and closed-form upper bound expression for the ergodic capacity is also given. The simulation results show that: a) Under rigorous hypothesis of self-interference channel, system performances, such as outage probability, end-to-end SINR and ergodic capacity are difficult to improve when signal-to-noise-ratio(SNR) increasing to a certain degree, due to the power of RSI increases linearly with transmission power. b) Ergodic capacity for the TWFD relay system is infinite approach to two times of that for two-way half-duplex(TWHD) relay system, while the power of self-interference tends to zero.(2) To the best of our knowledge, no prior work has research on the TWFD multiple-relay system over Nakagami-m fading channel. In this dissertation, we make a comparison between TWFD and TWHD multiple-relay system on outage performance. The analysis results show that only two methods, where one is power allocation and the other is to enhance the ability of SIC, improve the performance if the channel parameters, relay number and the target transmission rate are invariable, in high-SNR conditions. Moreover, power optimization can only play a limited role, and the truly restrict of the system performance is the ability of SIC. Given this, a hybrid duplex scheme is proposed, combined with optimal power allocation and relay selection, and the experiment results show that the hybrid duplex system, which absorbs the advantages of two kinds of systems, performs well.(3) Since the RSI has great influence on full-duplex system, the impact of the RSI on diversity-multiplexing tradeoff is studied. According to the results, we first define the RSI coefficient and RSI exponential, and point out that system diversity gain can be attained, only if self-interference is completely eliminated or the sum of the RSI exponential and system multiplexing gain is less than 1.