Research On Multi-relay Cooperative Wireless Communication System Based On NOMA Technology

Since its emergence,5G has seen rapid development of advanced application scenarios such as smart cities,telemedicine,and virtual reality,which demand network to offer higher spectrum efficiency and enhanced system reliability.As a wireless access technology,nonorthogonal multiple access(NOMA)technology can effectively improve spectrum efficiency and become a promising access method to be applied to 5G networks.The combination of relay cooperation technology and NOMA are expected to further improve system reliability and stability of edge users.Therefore,this work proposes a novel system model of direct connection and relay link cooperation based on NOMA technology for a wireless mobile system.In such a system model,a partial relay selection transmission scheme is proposed to select the optimal relay station for signal transmission.I employ a practical full-duplex residual self-interference model at the relay station and study the performance of the system model.In addition,in a multi-relay cooperative communication system,since cancellation technologies of the selfinterference,which is inherent in full-duplex relays,are not yet mature,our work further proposes in a NOMA-based wireless system,multi-collaborative virtual full-duplex scheme is employed for cooperative communication.The system performance is comprehensively analyzed in terms of the inter-relay interference.This work proposes a novel NOMA-based multi-relay cooperative wireless communication system model,where user information is transmitted through full-duplex mode relay stations,and optimal relay station is selected based on the first hop channel information among multiple relays.The probability of user interruption and the ergodic rate of are analyzed based on this scheme.In order to reduce the computational complexity,I analyze the lower bound expression of the outage probability expression and the approximate expression of outage in high signal-to-noise ratio.Simulation data show that the use of multiple relays in the system can effectively increase the user's interruption performance.It is also observed that although full-duplex relays are affected by self-interference,NOMA-based wireless systems still significantly outperform than half-duplex relay particularly in the presence of low-tomedium signal-to-noise.Because the self-interference generated by the relay stations is inherent in full-duplex mode the cancellation technologies have in research is not mature enough,I further propose a virtual full-duplex transmission scheme based on the NOMA multi-relay system model.Based on this model,I derive user outage probability and expression of outage probability at high signal-to-noise ratio and optimize the power allocation coefficient to achieve higher transmission rates for edge users.The analytical and simulation data verify that our proposed virtual full-duplex relay selection strategy is effective and outperforms half-duplex scheme fullduplex scheme in outage probability for edge users.