Wireless Transmission Theory And Method Of NOMA Assisted By Statistical CSI

With the large-scale deployment and commercial use of the 5th generation mobile communication system(5G),researchers at home and abroad have started pre-research on the future 6th generation mobile communication system(6G).6G is expected to provide global coverage,higher transmission rates,lower latency and energy consumption.Non-orthogonal multiple access(NOMA)is considered to be one of the key technologies to support future 6G wireless communication,which can reduce delay,improve spectrum and energy efficiency while ensuring user communication fairness.However,as the number of users and antennas increases,the acquisition of instantaneous channel state information(CSI)requires huge overhead.In comparison,statistical CSI is less expensive to acquire and can remain stable for a longer period of time.Therefore,the research on the theory and method of NOMA wireless transmission based on statistical CSI is conducted in this paper.The specific contributions are as follows:Firstly,in view of the difficulty of obtaining instantaneous CSI in practical application scenarios,a MIMO-NOMA downlink wireless transmission method based on statistical CSI is proposed.Consider a communication system with two multi-antenna users and a multi-antenna base station(BS),using the rician spatial correlation channel,and dividing the users into strong user and weak user according to the channel gain between the BS and the users.Based on statistical CSI,deterministic equivalent expressions for system ergodic sum rate are derived.Under the constraint of total transmit power of BS,by maximizing the deterministic equivalent expression,the transmit covariance matrices of strong and weak users with only statistical CSI are designed respectively,and the power allocation method between strong and weak users is proposed.The simulation results show that the derived deterministic equivalent expressions are highly accurate,and the proposed method can also effectively improve the communication performance of the system.Then,for the NOMA communication scenario where there is no direct link between the BS and the user,a RIS-assisted NOMA downlink wireless transmission method based on statistical CSI is proposed.Consider a communication system with two multi-antenna users,a multi-antenna BS,and a RIS with multiple reflection units.The rician spatial correlation channels are adopted,and the users are divided into strong user and weak user according to the channel gains of the BS to RIS and the RIS to the user’s concatenated channel.Based on statistical CSI,deterministic equivalent expressions for system ergodic sum rate are derived.Under the constraints of the minimum transmission rate of weak user and the total transmit power of BS,by maximizing the deterministic equivalent expression,precoding matrices for strong and weak users using only statistical CSI and phase shift matrices for RIS are designed respectively.The simulation results show that the derived deterministic equivalent expressions are highly accuracy,and the proposed design method can effectively improve the communication performance of the system while ensuring the fairness of user communication.