The Spectrum Efficiency Optimization Methods Based On Precoding Design For Wireless Communication

With 5th-generation mobile communication system having been put into service,research on the 6th-generation mobile communication system has been put on the agenda.The 6th-generation networks aim to further increase the average data rate and the edge rate,decrease in energy consumption and cost,and be able to transfer the energy at the same time.Precoding technology is one of the core technologies to achieve above goals.However,the precoding optimization methods used in current research usually have problems such as unsatisfactory iteration results,inability to guarantee convergence to a local optimum,slow convergence speed,and high complexity.This paper conducts indepth research on spectrum efficiency in energy-harvesting(EH)communication scenarios,Reconfigurable Intelligent Surfaces(RIS)-aided communication scenarios,and uplink and downlink synchronous transmission scenarios under precoding optimization methods.The precoding based optimization model for max-min throughput is developed,and corresponding fast convergence joint iterative algorithms are designed:This thesis considers energy-harvesting enabled networks,which serve more users by a lesser number of transmit antennas.By transmitting energy and information over different fractions of a time-slot,it employs conjugate beamforming(match filtering)to amplify the power of received signals for EH and regularized zero-forcing(RZF)beamforming to suppress the multiuser interference for information decoding(ID)and takes full use of time slots,improving the spectrum efficiency.The simulation results indicate the proposed algorithms in the thesis improves the user's spectrum efficiency compared with the traditional Simultaneous Wireless Information and Power Transfer(SWIPT).In the multi-cell and multi-user communication scenario with energy harvesting,combining the fractional time method and the improper Gaussian signaling(IGS)precoding,an iterative algorithm is designed to optimize the user's max-min throughput in the optimization of spectrum efficiency.While ensuring the security of user information,the max-min throughput to users is improved.Furthermore,a simplified improper Gaussian signaling precoding optimization algorithm is proposed,the algorithm reduces the complexity of the algorithm under improper Gaussian signaling,ensures the security of users' information and improves the user's max-min throughput.The simulation results demonstrate that the proposed algorithms in this paper has better spectral efficiency and information confidentiality than traditional Proper Gaussian signaling(PGS).In the reconfigurable intelligent surface-aided communication scenario,according to the feature that the reflection coefficient of the reconfigurable intelligent surfaces can be compiled,this paper proposes a joint design of reconfigurable intelligent surfaces and transmit beamforming under proper and improper Gaussian signaling,and introduces the Unit-Modulus Constraints of the reconfigurable intelligent surface reflection coefficient into the objective function which reduces the complexity of the algorithm.In simulation section,we consider with direct channels and without direct channels situation in reconfigurable intelligent surfaces-aided communication scenarios,and the performance of the proper Gaussian signaling algorithms and the performance of the improper Gaussian signaling algorithms are compared,numerical results demonstrate that communication with reconfigurable intelligent surfaces is better than communication without reconfigurable intelligent surfaces,and the algorithms under improper Gaussian signaling outperform the algorithms under proper Gaussian signaling.In view of the fact that inter-link interference and full-duplex(FD)loop-interference are hardly suppressed to a necessary level for the communication effectiveness,this paper proposes a joint design of precoding matrix for base station and uplink users,and optimize the coefficient of time fraction in the same time.The proposed method can use all antennas for transmission,and improve the spectrum efficiency and energy efficiency of the system.This paper also proposes a joint design of precoding matrix for base station and uplink users,and optimize the allocation of downlink and uplink bandwidth in the same time.The proposed method improves the spectrum efficiency by eliminating FD loop-interference.The simulation results confirm that the spectrum efficiency and energy efficiency of the above two methods are better than that of full-duplex,halfduplex frequency division multiplexing and half-duplex time division multiplexing.In summary,this paper studies the optimization of precoding for wireless communication systems,and proposes algorithms for joint optimization of precoding and time slot allocation,which effectively improves the spectrum efficiency of wireless communication systems.The method proposed in this paper has certain significance for the theoretical research and technical realization of wireless communication systems.