Research On The Enhancement Technology Of NOMA Relay System

With the rapid development of wireless mobile communication technologies,there's a sharp increase in the amount of user access and business types.How to improve the reliability of the communication system to achieve an efficient use of limited spectrum resources is still an important issue to be solved.The relay technology,which can be used to expand cell coverage,improves system capacity and reliability in the complex channel environment.In addition,Non-Orthogonal Multiple Access(NOMA)can achieve a robust performance gain and an efficient use of spectrum resources by introducing non-orthogonality in superposition coding.Given the reasons above,this paper mainly studies the combination of NOMA and relay technology.We propose different transmission strategies for different communication scenarios and different user Quality-of-Service(QoS)requirements.The main research contents and contributions of this paper are as follows: 1)Two transmission schemes are proposed for different communication scenarios in NOMA incremental relay system.Firstly,for the multi-user communication scenarios ordered by channel conditions,we propose a transmission scheme to combine the incremental relay with NOMA technology.The main idea is to enable relay and base stations to transmit information flexibly or remain silent by using the feedback information of high-power users,thus achieving a flexible cooperation of relays and improving the utilization of system resources.Then,an adaptive incremental relay transmission scheme is proposed for a two-user NOMA scenario ordered by the priority of QoS.The relay node realizes adaptive switching in different transmission modes by setting two thresholds.The proposed transmission scheme significantly improves the performance of high-priority users.Finally,we present different simulations of the proposed scheme in different communication scenarios to validate the theoretical analysis.2)For the two-user NOMA system,which have different QoS requirements,two transmission schemes are proposed considering the system with different number of relays and antennas.Firstly,for the communication scenario which includes one relay node and multi-antennas in the base station,a two-stage antenna selection transmission scheme based on CDRT,is proposed and can effectively improve the system capacity.The proposed scheme maximizes the instantaneous rate of low-priority users while satisfying the QoS of high-priority users.Then,we extend the transmission scheme mentioned above to a multi-relay communication scenario and propose a two-stage joint relay antenna selection transmission scheme based on CDRT.Finally,a simulation analysis for different schemes in different communication scenarios is made and the results verify the rationality and validity of the proposed schemes.In addition,some meaningful conclusions are obtained by studying the impacts of system parameters such as the number of antenna,the location of high-priority users,and the location of relay.