| Full-Duplex(FD)and massive multiple-input multiple-output(MIMO)provide the potential of boosting spectral efficiency performance.Incorporating FD in massive MIMO systems,called the FD massive MIMO system,can obtain the advantages of both technologies and further improve spectral efficiency.However,the problems of strong self-interference,high cost and high hardware resource consumption are considered to be the main obstacle for the FD massive MIMO systems applications.In thesis,we present a transmit-beamforming-based architecture for the FD massive MIMO digital self-interference suppression systems without additional hardware.To reduce the cost and the hardware resources required,a simplified structure for the FD massive MIMO digital self-interference suppression systems is studied.Moreover,theoretical analysis and simulation of the above two architectures is carried out,respectively.The main work and contributions are as follows:Firstly,the key technologies for FD massive MIMO systems are investigated.The operating principle and research status of FD,massive MIMO and FD massive MIMO systems is described.The self-interference cancellation(SIC)technologies of FD massive MIMO systems are classified and introduced,including analog SIC technologies,digital SIC technologies and digital-analog hybrid SIC technologies.Secondly,a transmit-beamforming-based structure for the FD massive MIMO digital self-interference suppression systems is introduced.A transmit-beamforming-based digital SIC algorithm under the structure is adopted,which divides the traditional digital precoding matrix into two submatrices to achieve traditional digital beamforming and self-interference cancellation,respectively.It can achieve self-interference cancellation without additional hardware.The methods to improve the SIC ability of the algorithm is theoretically analyzed.The performance of the architecture is simulated.Simulation results show that the structure with 2.6 GHz,100 MHz bandwidth and 96 transmit/receive antennas can achieve the average suppression ability of 171 d B.In addition,the sum rate achieved by combining 50 d B antenna isolation is 1.7 times that of half duplex.Thirdly,a simplified structure is proposed for the FD massive MIMO digital selfinterference suppression systems,which can reduce the required number of radio frequency channels by two-thirds.In this structure,each transmit or receive RF channel is connected with three transmit or receive antennas.The design method and the influencing factors of SIC ability for the beamforming-based SIC algorithm under simplified architecture is introduced and analyzed.The system performance under simplified architecture is simulated and analyzed.The simulation results show that the simplified structure with 2.6 GHz,100 MHz bandwidth and 96 transmit/receive antennas can achieve the average suppression ability of 43 d B.Furthermore,the sum rate achieved by combining 50 d B antenna isolation is 1.56 times that of half duplex.This thesis mainly focuses on balancing the performance,cost and hardware resources required of the FD massive MIMO systems.The proposed structures can be applied in engineering practice and have reference significance. |
