Research On Transmit Antenna Selection And Beamforming Design For Wireless Communication System

With the development of the Internet of things technique,the communication performance of access devices is becoming more and more demanding,and the number of access devices in communication systems is exploding.Improving the communication performance of access devices and the access capability of communication systems has become a topic of wide concern.In the case of the same transmission power and the same bandwidth,the multiple input multiple output(MIMO)technique can achieve several times the channel capacity of the single-antenna benchmark scheme,thus significantly improving the communication performance of access devices;the non-orthogonal multiple access(NOMA)technique can access multiple users simultaneously within the same physical resource block(such as time and frequency),thus significantly improving the access capability of communication systems.This thesis presents an in-depth study of the system model,resource allocation optimization scheme,achievable sum rate or total transmit power,etc.based on downlink MIMO NOMA communication system.MIMO communication systems with a relatively large number of transmit antennas lead to high hardware cost and power consumption because each transmit antenna is connected to a dedicated RF chain,so it is necessary to activate some of the antennas by transmit antenna selection(AS)to balance the system performance,hardware cost and energy consumption.To this end,this thesis first investigates the joint design of transmit antenna selection and multi-stream beamforming for downlink MIMO NOMA communication systems.The achievable sum rate are maximized subject to the quality of service(Qo S)constraints for weak users,the transmit power constraint and the transmit antenna selection constraint.An algorithm combining the penalty dual decomposition(PDD)method with the weighted minimum mean squared error(WMMSE)method is proposed to solve this optimization problem and obtain a local optimal solution.The simulation results show that the proposed communication scheme has higher achievable sum rate and good convergence compared to the benchmark schemes.Intelligent reflecting surface(IRS)technique can optimize the signal transmission path.The performance of downlink MIMO NOMA communication system can be further improved by applying the IRS technique.To this end,the joint design of active multi-stream beamforming and passive beamforming for downlink MIMO NOMA communication system assisted by the IRS is also investigated in this thesis.Subject to the successive interference cancellation(SIC)decoding rate constraints and the unit-modulus constraint,the active multi-stream transmit beamforming of the transmitter and the passive beamforming of the IRS are jointly optimized to minimize the total transmit power of the transmitter.An efficient alternating optimization(AO)algorithm is proposed to solve this non-convex optimization problem to obtain a local optimal solution.Under the assumption of fixed passive beamforming,a WMMSE-based algorithm for solving the multi-stream transmit beamforming subproblem is proposed.On the basis of fixed active multi-stream transmit beamforming,the passive beamforming subproblem is solved by using matrix lifting method and an algorithm based on difference-of-convex(DC).Simulation results show that the proposed communication scheme has lower total transmit power and good convergence performance compared to the benchmark schemes.