Research On Key Technologies Of Simultaneous Wireless Information And Power Transfer In Full-Duplex Communication Systems

Recently,with the significantly increasing of transmission rate of wireless communication system and the wide application of Internet of Things(IoT),the energy consumption of wireless terminals is growing higher than ever,which also brings much more demands for the battery capacity of the wireless devices.Unfortunately,the development of the battery technology does not catch up with that of the mobile communication system.Therefore,how to extend the battery time of mobile terminals has become one of the critical and tough problems for the communication system.It has been revealed in some previous work that the technology of full-duplex(FD)simultaneous wireless information and power transfer(SWIPT)will harvest and store energy for the wireless communication system and prolong the lifetime of the chargeable devices while guaranteeing a certain quality of the wireless communication system.This thesis has studied the FD SWIPT bidirectional communication system from the perspective of energy and information transmission.Specifically,three types of optimization problems,including harvested energy maximization,weighted sum transmit power minimization and sum rate maximization problem,are deeply investigated for the system.Furthermore,in order to solve the above nonconvex optimization problems,different kinds of algorithms are designed based on convex optimization theory.The main contents and contributions are listed as follows:(1)In order to solve the problem of maximizing harvested energy in the FD SWIPT bidirectional communication system,an optimization scheme to enhance energy harvesting is proposed.Based on one-dimensional search and linear programming(LP),a closed-form optimal solution with low time complexity is obtained.In this scheme,the problem of maximizing harvested energy in SISO scenario is modeled.In order to maximize the energy harvested by the user FD-B while considering the constraints of signal-to-interference-and-noise ratio(SINR)and maximum transmit power at both nodes,we jointly design the optimal transmit power of FD-A and FD-B,as well as the power splitting ratio(PSR)of FD-B.Unfortunately,the primal problem is non-convex and is not always feasible with different parameters.Thus,we first present a set of conditions,under which the feasibility of the primal problem is guaranteed.Then,we derive the closed form of the optimal solution with the aid of analyzing the feasible region of the problem.Furthermore,the influences of the parameters on the maximum harvested energy are theoretically analyzed to reveal the relationship between the parameters and the maximum harvested energy.Finally,simulation results are provided to verify the optimality of the proposed closed-form solution,to validate the analysis of the impact of parameters on the maximum harvested energy and to show the effectiveness of the proposed design,respectively.(2)In order to solve the problem of minimizing the weighted sum transmit power of the devices in the FD SWIPT bidirectional communication system,an optimization scheme to reduce the transmit power consumption is proposed.Based on semidefinite relaxation(SDR),an iterative algorithm to solve the problem of minimizing weighted sum transmit power in the system is obtained.In this scheme,the problem of maximizing harvested energy in downlink MISO and uplink SIMO scenario is modeled.In order to minimize the weighted sum transmit power,we jointly design the transmit beamforming vector of full-duplex access point(FD-AP),the receiving PSR of full-duplex mobile station(FD-MS),as well as the transmit power of FD-MS.Since the original problem is non-convex,we apply SDR and obtain a new convex problem.We further prove that solutions for both problems are identical.Finally,simulations are provided to verify our analysis,and the comparison with a half-duplex(HD)system demonstrates the significant performance gain from self-energy recycling.(3)In order to solve the problem of maximizing the sum rate of the devices in the FD SWIPT bidirectional communication system,an optimization scheme to improve the sum rate of the system is proposed.Based on one-dimensional search and difference of convex functions(DC)programming,an iterative algorithm to solve the problem is obtained.In this scheme,the sum rate maximization problem under a SISO scenario is modeled.In order to maximize the sum rate of the system while considering the constraints of SINR,minimum harvested power by the user FD-B and maximum transmit power at both nodes,we jointly design the optimal transmit power of FD-A and FD-B,as well as the PSR of FD-B.Secondly,the feasibility of the optimization problem is analyzed to propose a set of feasible conditions,which guarantees the existence of the optimal solution for the original problem.Based on the feasibility of the problem,an iterative algorithm for solving the non-convex problem is obtained by combining one-dimensional search and DC algorithm.Finally,the simulation results reveal how different system parameters impact on the maximum sum rate of the system.At the same time,it is verified that the maximum sum rate of the FD SWIPT system is higher than that of HD SWIPT system.