Research On Beamforming Design For Full-Duplex SWIPT Communication Systems

With the increment of wireless services and the explosive growth in the number of user equipment,wireless communication systems are faced with the double pressure of radio spectrum scarcity and sharp increase in energy consumption.As the candidate technologies for the 5G standards,full-duplex(FD)transmission and the technique of simultaneous wireless information and energy transfer(SWIPT)are expected to cope with the aforementioned stress.On the one hand,FD communication allows terminal devices to transmit and receive data at the same time and on the same frequency.On the other hand,SWIPT technique can achieve the effective transfer of wireless energy,and realize the information interaction in the meantime.Exploiting SWIPT in a FD system,which can make a simultaneous improvement in spectrum efficiency and the energy sustainability of communication systems.Accordingly,the joint optimization schemes of the beamforming vectors based on different goals are studied in the context of the FD SWIPT communications,and the main innovations of this paper are threefold:(1)A joint optimization scheme based on the dual goals which are the minimization of the power consumption and the maximization of the energy harvest was proposed for the multi-user FD cellular communication network.The proposed scheme used zero-forcing(ZF)algorithm to eliminate multi-user interference in the uplinks,in order to achieve the effective transfer of information and energy,the FD base station provided users with communication services via information beamforming and energy beamforming in the downlinks.Noting that the problem of power is non-convex,the original problem was transformed to a convex one via semi-definite relaxation(SDR).Simulation results show that the proposed scheme provides substantial power savings over traditional schemes,which improves power efficiency of the system effectively.(2)A joint optimization scheme of the beamforming vectors based on the maximization of the system sum rate was proposed for the SWIPT communication systems with a FD base station.The proposed scheme constructed the optimization model with the aim of maximizing the system sum rate while guaranteeing the transmitting power constraints in the uplinks/downlinks and energy harvesting requirement.Owing to the coupling among the optimization variables,the problem of rate became non-convex,we first turned it into a convex form by exploiting the techniques of SDR and first-order Taylor approximation,then the suboptimal information beamforming vectors and energy beamforming vectors were obtained by the iterative algorithm based on successive convex approximation(SCA),respectively.Simulation results show that the performance of the proposed scheme is better than those of the conventional schemes,and the proposed scheme makes effective improvement in the system sum rate.(3)A joint optimization algorithm of the beamforming vectors based on the maximization of the system sum-rate was proposed for SWIPT in a FD cellular communication system.We adopted a minimum mean square error with successive interference cancellation(MMSE-SIC)receiver to simultaneously suppress multi-user interference,self-interference and background noise in the uplinks.Due to the non-convexity of the formulated optimization problem,we applied SDR to linearize nonconvex constraints,and then solved the suboptimal information beamforming vectors and energy beamforming vectors based on the DC(Difference of Convex Function)programming reformulation and SCA iterative algorithm.Simulation results demonstrate that the proposed scheme with MMSE-SIC yields a significant system sum-rate gain over a baseline scheme with ZF,thus the proposed scheme with MMSE-SIC effectively improves the data rate for the system.