One-/Two-Way Relay Transmission Schemes And Their Performance Analysis In Wireless Communication Systems

Relay technology has been a key technology in wireless communication system because it can effectively combat channel fading, extend coverage, and improve system capacity and so on. On the one hand, reasonable and efficient transmission schemes, such as relay selection, antenna selection and so on can effectively reduce power consumption and the complexity of signal processing. More importantly, at the same time, it can bring significant performance improvement. On the other hand, theoretical performance analysis is an important tool to guide the actual communication system design and performance optimization. By optimizing the analysis results, such as minimization of outage probability, maximization of average rate etc., some optimal system parameters can be obtained to guide the transmission scheme design, power allocation and so on. This thesis aims at relay transmission scheme and performance analysis. To be more specific, the transmission scheme and performance analysis for one-/two-way relaying in wireless communication system are studied in this thesis.Firstly, an exact performance analysis of two-way single relay scheme under independent but not necessarily identically distributed (i.n.i.d.) Nakagami-m fading channel with integer and integer plus half fading parameter m is conducted. Closed-form expressions for outage probability and average sum-rate are obtained. Using the unified moment generating function (MGF)-based approach, the exact average symbol error rate (SER) of various M-ary phase shift keying (M-PSK) is determined. It has been proved that the above analytical results include the previous research results in Rayleigh fading channel as a special case. Simulations have verified the correctness of the analytical results. The analytical results can be used to guide the two-way relay system design and optimization.Then, consider multiuser two-way relay scheme, this thesis analyzed its capacity performance over i.n.i.d. Nakagami-m fading channel with integer fading parameter m. Closed-form lower bound of the system capacity is obtained. It has been proved when m=1, the analytical result is in a good agreement with previous research results in Rayleigh fading while it has a wider range of applications. Simulation results have been presented to verify the theoretic analysis. The research results provide a theoretical basis of system design for multiuser two-way relaying network under Nakgami-m fading channels.Thirdly, this thesis studied the performance of two-way multi-relay communication system when different schemes are adopted. The main results are as following:(1) When all participate relaying (APR) scheme used, this thesis analyzed the asymptotic performance at high SNR region, presented the closed-form expressions for outage probability and average bit error rate (BER), and then the diversity gain and coding gain are obtained. The validity of the analytical results has been confirmed by simulations.(2) When dual relay selection amplify-and-forward (DRS-AF) scheme has been adopted, the closed-form lower and upper bounds of outage probability and the exact averge symbol error rate (SER) are derived. Numerical and simulation results are presented to corroborate the analytical analysis. The analytical results can be used to guide the two-way multi-relay system design and optimization.Next, consider multi-antenna two-way single relay scheme, a new efficient transmission scheme, called joint antenna selection and data exchange (joint AS-DE) scheme based on antenna selection and data exchange technologies, is proposed. Furthemore, the outage probability performance for it is studied and its lower and upper bounds are derived. It has been proved that this scheme can achieve full diversity and it outperforms the conventional max-max AS scheme and max-min AS scheme in any SNR regions. This research result can be applied in multi-antenna two-way relaying to improve performance.The last part of the thesis is based on HARQ technology and its throughput performance study in one-way relay scheme, we obtained the following results:(1) Based on ACKnowledgement/Negative AcKnowledgement (ACK/NAK) feedback signaling, a new SNR estimation method at transmitter is proposed. The influence of the errors in the feedback channel on the achieved SNR estimate is addressed. Simulation results are presented to verify the applicability of the proposed SNR estimate scheme over both the AWGN and the Rayleigh fading channels.(2) Consider asymmetric fading environments in one-way relaying where MSâ†'RS and RSâ†'BS undergo independent Rayleigh and Rician fading respectively, delay-limited (DL) throughput for three HARQ protocols (ALO, RTD and INR) is stuied. Furthermore, the impact of different parameters on the achievable DL throughput, such as the maximum HARQ round number L, line-of-sight (LoS) signal K, information rate R etc., is analyzed, and then compare the performance when the adaptive optimised information rate and fixed information rate adopted. The research results can be used as a novel SNR estimation method and are helpful for designing HARQ system.