Research On Transmission Technology And Fading Performance In Non-Orthogonal Multiple Access

The multiple access technology is the basic technology of wireless communication evolution,and its breakthrough often promotes the upgrade of wireless communication system.The 1st generation mobile communication to 4th generation mobile communication are based on OMA technique,that is,one orthogonal resource is allowed to be allocated to one user,which severely limits the throughput of the network and the number of device connections.However,with the rapid development of Internet of Things and mobile Internet,the contradiction between limited spectrum resources and increasing demand for system capacity is becoming more prominent,and OMA technology is limited by spectrum efficiency and access capability to meet future mobile communication system needs.In order to face the challenges of 5G such as massive links,and lower latency,many technologies are proposed successively,such as LS-MIMO,UDN,SCN and NOMA.NOMA has received extensive attention from academia and industry for its ability to greatly improve spectrum efficiency and access capability.The NOMA DH AF downlink cooperative relay system under hardware impairment is studied.The closed-form expressions of OP and ESR for two users and the asymptotic results under high SNR are obtained.The analysis results show that,with the increase of hardware impairment coefficient,the system's outage performance is degraded regardless of the far user or the near user.As SNR increases,the ESR has an upper bound in the hardware impairment condition,which means that the system ergodic performance does not improve with SNR increased;Under the same SNR,ESR gradually approaches to zero with the increase of hardware impairment coefficient,which shows that the NOMA DH AF cooperative relay system does not work properly.Finally,the performance of the NOMA DH AF downlink cooperative relay system based on hardware impairment and ICSI is studied,and the different links adopt different fading channels.At this time,information decoding is used rather than user decoding.The corresponding closed expression of OP and approximate performance under high SNR condition is obtained,and then the throughput under the system is analyzed.The simulation results show that the outage performance under ideal conditions is better than that under hardware impairment and channel estimation error,and it is shown that the hardware impairment and channel estimation error cause the system's outage performance to worse.When the channel estimation error is not equal to zero,the OP of two user information has an error floor with the increase of SNR,which means that the impact of the channel estimation error on the system is worse than that of the hardware impairment.