Research On Beamspace Massive MIMO-NOMA System At Millimeter-Wave Frequencies

At present,the research on the fifth-generation mobile communication(5G)related technologies is at a critical stage,and the large-scale commercialization of 5G in the latter stage will make the Internet of Everything possible.Millimeter wave communication,massive multiple input multiple output(MIMO),non-orthogonal multiple access(NOMA)and wireless information energy simultaneous transmission(SWIPT)as the key technology of 5G has become a research hotspot.The combination of these technologies can improve the system's spectral efficiency and energy efficiency,and it is possible to accelerate the implementation of 5G.In this context,in order to reduce the complexity of the system and improve the overall performance of the system.In this paper,the massive MIMO-NOMA system of millimeter-wave frequency in beamspace is studied from the perspective of spectral efficiency and energy efficiency.Firstly,the beam selection scheme is improved by utilizing the sparsity of the millimeter-wave beam space channel.After performing the beam selection of the maximum amplitude,the beam is continuously filtered to achieve a lower-dimensional rank reduction of the channel,thereby enabling the system to reduce the number of radio frequency chains while ensuring high performance of the system.Then,the lens antenna is used to replace the traditional antenna to realize the analog beamforming,and the signal is directly converted from the spatial domain to the beam domain for processing,which reduces the complexity of the transceiver.Finally,the beamspace system performance under different precodings for the maximum amplitude beam selection scheme and the improved beam selection scheme is simulated.The simulation results show that the improved beam selection scheme achieves higher energy efficiency while ensuring high spectral efficiency compared to the maximum amplitude based beam selection scheme.Although the NOMA technology increases the number of access users,there are also large interferences when users share the same spectrum resource.In order to eliminate the interference between users,this paper uses the zero-forcing precoding scheme and successive interfrerece cancellation(SIC)to remove the inter-beam interferences and the intra-beam interferences.And in the user dense access scenario,a new user scheduling scheme is introduced.That is,select the appropriate users from all requesting users and pair the users to improve system performance.Compared with the user scheduling scheme based on maximum SINR and the user scheduling scheme based on the maximum matching user rate,the simulation results show that the proposed user scheduling scheme can obtain the highest spectral efficiency.Subsequently,the NOMA system using power allocation is further studied,and the performance of the system under user scheduling and power allocation is simulated.The simulation results show that the system performance of user scheduling combined with power allocation is significantly better than that of direct power allocation.In order to meet the needs of different access users,an adaptive scheme for judging whether to perform scheduling according to the number of users requesting access is formed.The simulation results show that the adaptive scheduling scheme ensures the stability of system performance.In order to effectively reduce the energy consumption of wireless communication devices in a 5G network,a power split based SWIPT technique is introduced in a beamspace system employing user scheduling and power allocation.The influence of equal power split on system capacity is analyzed,and two power segmentation schemes are studied based on the principle that strong users collect less energy and weaker users collect more energy.The simulation results show that the two schemes achieve better system performance than equal power partitioning.Then,in order to improve the problem of poor user performance caused by this segmentation principle,cooperative relay communication technology is adopted.A strong user with good channel conditions is used as a relay forwarding signal to weak users,which reduces the probability of interruption to a certain extent.The simulation results show that the use of cooperative relay communication not only improves the capacity of the system,but also improves the rate of weak users.