Research On Key Technologies Of Non-Orthogonal Multiple Access In 5G Mobile Network

Nowadays,the explosive growth of mobile data,massive device connectivity,and emerging new services and applications have become key drivers for the development of the fifth-generation communications networks(5G).Non-Orthogonal Multiple Access(NOMA)has been proposed as an important candidate for improving system capacity and adapting to the needs of the Internet of Everything.Compared with the traditional orthogonal multiplexing of individual user information into different orthogonal resources,the core of non-orthogonal multiple access is that multi-user information can be multiplexed into the same orthogonal resource,which can further improve system performance.Therefore,non-orthogonal multiple access technology has an important application significance for 5GFirstly,the paper studies the application of 5G mobile network architecture and non-orthogonal multiple access technologies in the future 5G application scenarios.And then it analyzes the research status of power domain and code domain non-orthogonal multiple access technologies respectively and their technical characteristics.Secondly,the paper focuses on the non-orthogonal multiple access system model based on power domain non-orthogonal multiple access,building a 3-user non-orthogonal multiple access system model.The model of multi-user transmission and reception is analyzed theoretically.Based on this,the corresponding successive interference cancellation(SIC)receiver is designed to detect each user information,and the process of user signal detection and reception is analyzed.From the mathematical derivation,it is concluded that the power factor assigned to each user affects the accuracy of the final receiver signal detection.In order to further reduce the overall bit error rate(BER)of the system,the paper focuses on the problem of lack of adaptation to channel variation that exists in the traditional NOMA power allocation algorithms,such as,full search power allocation(FSPA)algorithm,fixed power allocation(FPA)algorithm,fractional transmit power allocation(FTPA)algorithm.Then,a new dynamic power allocation scheme:improved fractional transmit power allocation(I-FTPA)scheme that can calculate power allocation coefficients for users based on their channel conditions is proposed to enhance the overall performance of system.Finally,this paper builds a system simulation platform and carries out simulation verification.Under the condition of transmitting the same bit information,the argumentation of system simulation in this paper is mainly divided into two parts:firstly,BERs of users of NOMA system and traditional orthogonal frequency division multiple access(OFDMA)system is compared.The simulation results show that with the increase of the energy per bit ratio noise power spectral density(Eb/NO),BER of each user in the NOMA system based on FPA,FTPA and I-FTPA is much lower than that in OFDMA system.Meanwhile,different power adjustment factors in I-FTPA have different effects on the users of the NOMA.By adjusting different power adjustment factors,it can be used for power allocation according to different application scenarios.Secondly,simulation results of NOMA I-FTPA are compared with NOMA FPA and NOMA FTPA.It is proved that with the increase of Eb/NO,the performance of NOMA I-FTPA is better than the latter two in improving the overall system reliability.The results of this paper have guiding significance for the deployment of NOMA in 5G.