Research On Theory And Method Of Wireless Transmission Based On NOMA

With the explosive growth of smart terminals and the rise of emerging demand such as the Internet of things,countries around the world have extensively carried out research on key technologies of the 5th Generation Mobile Communication System(5G).Compared with the existing mobile communication systems,5G will be significantly improved in terms of transmission rate,wireless coverage,transmission delay and user experience,and the increasingly scarce spectrum resources will make 5G have ultra-high spectral efficiency.Non-orthogonal Multiple Access(NOMA)technology,which provides services for multiple users at the same time-frequency resource,can effectively improve spectrum efficiency.In recent years,it has become one of the 5G technologies widely studied by scholars at home and abroad.Compared with traditional Orthogonal Multiple Access(OMA)technology,NOMA needs to balance system transmission rate and user fairness,and NOMA introduces more inter-user interference.Therefore,how to properly allocate wireless resources and realize the superior performance of NOMA technology has become an important research issue.According to the above problem,this paper has done the following research work.Firstly,the implementation principle,advantages and disadvantages of the current new multi-access technology are introduced.In view of the strong non-orthogonal advantages of NOMA,the key technologies adopted in NOMA are elaborated,and the wireless transmission process of NOMA and OMA systems in two-user scenarios are analyzed.It is revealed that NOMA is far superior than OMA in system performance when the number of users is larger than the number of base station's antennas.Secondly,for the scenario of imperfect Channel State Information(CSI),the NOMA-based downlink power allocation method is studied.Based on users' channel gain difference and correlation,an improved user selection method is proposed,which effectively improves the system performance,the base station adopts Regularized Zero Forcing(RZF)precoding,with system user fairness as a constraint,based on ‘system sum rate maximization',a multi-user NOMA downlink power allocation method using imperfect CSI is proposed,which can dynamically allocate the total transmit power of the base station according to users' channel gain.Compared with the existing method,the simulation results show that the proposed method can better maintain the fairness of users while ensuring system performance.Finally,a wireless resource allocation method based on NOMA is proposed for wireless energy-carrying communication scenarios.In the system,the part of user's signal use for decoding information,meanwhile,convert the rest of user's signal into energy for uplink pilot and circuit consumption.Under the constraint of system user fairness and effective use of energy collected by users,the optimal regularization parameters,power splitting coefficients,and power allocation coefficients are designed based on the principle of ‘system spectral efficiency maximization'.Compared with the existing method,the proposed method can effectively reduce the interference,and the user can coordinate the information decoding and energy collection with the optimal power splitting coefficient,which significantly improves the system spectral efficiency.