Performance Research Of Cooperative NOMA System Based On Full-duplex Multi-relay

With the application of the fifth-generation mobile communication technology,the number of intelligent terminals has increased rapidly,showing explosive growth,thus proposing higher requirements for the utilization of spectrum resources.Fullduplex communication technology is an effective communication mode that can effectively utilize spectrum resources.At the same time,Non-Orthogonal Multiple Access(NOMA)technology can improve spectrum efficiency while ensuring user fairness.Combining NOMA technology with full-duplex communication technology can provide a more efficient communication mode.Therefore,this thesis focuses on the impact of relay selection strategy on system performance for collaborative NOMA systems based on full-duplex communication mode.The main work is as follows:(1)For the two-user NOMA system based on full-duplex multi-relay,this thesis analyzes the impact of two-stage relay selection and partial relay selection strategies on system interruption performance.The theoretical expression of user interruption probability is derived,and simulation is used to reveal the impact of relay quantity,relay forwarding protocol(Amplify-and-Forward,AF and Decodeand-Forward,DF),and relay working mode(half-duplex and full-duplex)on system interruption performance.Simulation results show that the two-stage relay selection strategy can improve system interruption performance when using AF and DF protocols.In addition,compared with the half-duplex mode,using full-duplex can significantly improve system interruption performance.When the number of relays increases,the two-stage relay selection strategy can significantly reduce the system’s interruption probability,but when the number of relays is greater than two,the system’s interruption probability remains basically unchanged when using partial relay selection strategy.(2)For the cognitive non-orthogonal multiple access(NOMA)system with full-duplex multi-relay,expressions for the system interruption probability were derived under the amplify-and-forward mode,considering two-stage relay selection and partial relay selection strategies.Simulations were conducted to investigate the impact of AF and decode-and-forward relay protocols on system performance.The results demonstrated that as the number of relay nodes increased,the system interruption probability gradually decreased when employing the two-stage relay selection and partial relay selection strategies.Comparatively,the full-duplex mode for relays achieved better system interruption performance than the half-duplex mode.Additionally,due to the amplification of both the signal and noise,the interruption performance was slightly inferior for the AF protocol compared to the DF protocol.This indicates that selecting an appropriate relay forwarding protocol plays a crucial role in enhancing system interruption performance.