A Study On Millimeter Wave MIMO Communication Non-orthogonal Multiple Access Technology

With the rapid development of the modern society,the demand for wireless mobile communication service is fast growing.Since the data rate of traditional orthogonal multiple access(OMA)is almost saturated,the new multiple access technology has attracted wide attention of researchers.Power domain non-orthogonal multiple access(NOMA)can provide simultaneous access of multiple users in the power domain,which is capable of further improving the data rate compared to OMA.Millimeter wave(mmWave)multi-input multi-output(MIMO)can provide highly directional analog beams but the number of radio-frequency chains is limited.MmWave MIMO-NOMA can serve multiple users by a single beam,which can effectively increase the number of simultaneously served users as well as the system overall performance.The detailed work is included as follows.MmWave MIMO-NOMA system based on lens antenna array is first studied.Regularized multipath matching pursuit(RMMP)algorithm is proposed by exploiting the sparsity of beamspace channel matrix.Then the user pairing method,equivalent channel construction method and power allocation algorithm are sequentially investigated.The simulation results show that the mean square error of RMMP algorithm under high SNR is much smaller than the orthogonal matching pursuit algorithm and orthogonal least square algorithm,while the running time is much smaller than the multipath matching pursuit(MMP)algorithm.In addition,the mmWave MIMO-NOMA system based on the lens antenna array can achieve better spectral efficiency and energy efficiency compared with the mmWave OMA system.Besides,the mmWave multi-subbeam MIMO-NOMA system based on phase shifters network is also studied.A NOMA method for dividing all transmit antennas into multiple sub-arrays to form multiple subbeams to simultaneously serve multiple users is proposed.In exisiting single-beam NOMA,each beam can simultaneously cover multiple users.However,mmWave analog beams are highly directional.In this context,we divide a single analog beam into multiple subbeams with each subbeam pointing at a different user,which is spatially more flexibile than the single-beam NOMA.Correspondingly,the uplink pilot-aided channel estimation,the downlink digital precoding design and the successive interference cancellation at the user side are also studied.In particular,a power allocation method for maximizing the system sum rate is also presented The simulation results show that the mmWave multi-subbeam NOMA system can achieve higher sum rate than the mmWave single-beam NOMA system.