Research On The Application Of Nonlinear Precoding Algorithm In 5G

With the development of mobile communication,the demand has already shifted from the initial analog voice communication to high-quality multimedia services and mobile Internet services.To better support the aforementioned business needs,the 5th generation(5G)mobile communication system emerge as the times require.Multiple input multiple output(MIMO)is the key technology of the fourth generation(4G)mobile communication system,the superior technical performance makes it continue to shine in 5G.In MIMO systems,multiple antennas are configured at the transmitter and receiver,it will introduce inter-antenna interference,so it is necessary to pre-eliminate the interference at the transmitter,namely,the precoding technology.The precoding technique has the distinction between linearity and nonlinearity.Linear precoding is simple to implement,but it will cause power loss and reduce the equivalent SNR at the receiving side,this can be solved by introducing vector perturbation technique.This technique performs nonlinearity on the transmitted signal,the processing can minimize the norm of the pre-encoded signal while eliminating the interference in advance.Therefore,the core content of this paper is the application of nonlinear vector perturbation precoding technology in 5G MIMO systems.The core content of this paper is mainly divided into two parts,which are the research of vector perturbation precoding based on sparse coding non-orthogonal multiple access system and the research of digital-analog mixed vector perturbation precoding under millimeter wave architecture.In this paper,we firstly introduce the MIMO system structure and the related precoding techniques.The advantages and disadvantages of the linear zero-forcing precoding and the nonlinear vector perturbation precoding are compared and analyzed,the BER performance of the above precoding algorithm is simulated.Subsequently,sparse coding and non-orthogonal multiple access techniques are introduced.The application of vector perturbation precoding techniques in MIMO-SCMA systems is studied.The corresponding MIMO transmission scheme has been designed in the high-dimensional modulation system,three optimization scheme has been proposed for the modul loss which caused by the non-uniform transmission constellation of the transmission vector,which are extend constellation soft demodulation,constellation rotation and the extension of module interval,the ber performance of the system has been improved.Finally,the digital-analog hybrid vector perturbation precoding technology in millimeter wave communication system has been studied.The wideband millimeter wave hybrid precoding system is introduced.A new type of digital-analog hybrid vector perturbation transmitter structure is proposed at the transmitting side,and a good ber performance has been achieved.Aiming at the feature that each subband in the wideband millimeter wave system use the same analog precoding,a precoding switching scheme based on the subband equivalent channel matrix condition number is proposed,which can achieve the compromise between complexity and ber performance of the system.