Performance Research For NOMA Cognitive Relay Networks Under Imperfect Conditions

Non-orthogonal multiple access(NOMA)has become one of the key technologies of 5G due to its advantages of low latency and wide connectivity.Cognitive radio(CR)can achieve dynamic spectrum sharing,which is an effective way to improve spectrum utilization.Simultaneous wireless information and power transfer(SWIPT)can effectively improve system energy efficiency.The combination of NOMA,CR,and SWIPT technologies can achieve dual improvements in spectral efficiency and energy efficiency,which has been widely studied by scholars.However,most of the existing studies have been conducted under ideal conditions.In practical environments,channel estimation errors and imperfect sequential interference cancellation are inevitable.To provide a more accurate basis for performance evaluation,this paper considers non ideal sequential interference cancellation and imperfect channel state information when modeling the system,which is more suitable for practical application scenarios.The main research work includes the following two points:1.For cognitive wireless networks based on non-orthogonal multiple access(CR-NOMA),considering both non ideal sequential interference cancellation and channel state information,a closed expression of the secondary user outage probability is derived,and the correctness of the theoretical derivation is verified by Monte Carlo simulation.Simulation results show that both non ideal CSI and imperfect SIC can reduce user interrupt performance,and imperfect SIC has a greater impact on interrupt performance.Secondly,compared to orthogonal multiple access(OMA),using NOMA access can achieve higher access rates and lower outage probability for secondary users,indicating that NOMA technology can effectively improve the effectiveness and reliability of information transmission.2.Aiming at cognitive relay(SWIPT-NOMA-CR)networks based on wireless portable communication and non-orthogonal multiple access,considering the actual situation of imperfect sequential interference cancellation and channel state information,the outage performance of secondary users in the system using three relay transmission schemes,namely ideal,time switching,and power division,was studied.The analytical expression of the sub user outage probability is derived,and the correctness of the theoretical derivation is verified by Monte Carlo simulation.The experimental results show that non ideal SICs and CSIs can lead to a decrease in the interrupt performance of secondary users,and compared to imperfect CSI,imperfect SIC cause a greater loss in system interrupt performance.In addition,the outage probability of users using the PS relay transmission scheme is lower than that using the TS scheme.When changing the imperfect SIC and CSI factors,the outage probability difference of users using the PS scheme is smaller than that using the TS scheme,indicating that the reliability of the PS relay transmission scheme is superior to the TS scheme.