Research On Optimization Algorithm Of Swipt Full-Duplex User-Aided Coopertive NOMA System

Non-orthogonal multiple access(NOMA)technology is recognized as a potential technology to improve spectrum efficiency.Meanwhile,the emerging simultaneous wireless information and power transfer(SWIPT)technology harvesting energy while decoding information,which extends the life of energy limited wireless devices to a certain extent.Considering the non-uniformity of user distribution,the virtual pairing(VP)scheme is applied to the SWIPT-based cooperative NOMA system.The cell-center users with non-overlapping frequency bands are used to cooperate with one or more cell-edge users for information transmission.Therefore,this paper studies the implementation of VP scheme for downlink full-duplex(FD)multi-antenna cooperative NOMA system,in which the cell-center user equipped with power splitting architecture.In the scheme of two near users,the cell-center nearest to the base station is used as the FD cooperative NOMA relay to assist the base station and the cell-edge user transmit information.The goal is to maximize the data rate of user relay while satisfying the QoS constraints of two NOMA users.A joint optimization scheme of beamforming vectors and PS ratio is proposed.Because the optimization problem is highly nonconvex,an algorithm based on alternating optimization(AO)is proposed.Firstly,Dinkelbachs theory linearizes the objective function.Secondly,a successive convex approximation(SCA)-based method with semidefinite relaxation(SDR)and arithmetic and geometric means(AGM)inequality is used to jointly optimize the beamforming vectors and PS ratio.For the SWIPT downlink cooperative NOMA system,a VP scheme with one central cell user and two cell edge users is considered.Using FD multi-antenna cell-center user,with PS receiver as friendly relay.For the proposed system,we establish the joint optimization problem of the PS ratio,the transmit beamformers at BS as well as the receive and transmit beamformers at the cell-center user,to maximize the cell-center user data rate,while guaranteeing QoS requirement of the two cell-edge users,and the power constraints of BS and cell-center user.As the established joint optimization problem is non-convex and multivariable coupling,we propose AO-based strategy to transform the original problem into two subproblems.Specifically,SDR technique is applied to rank constraints of two sub-problems,and SCA is adopted to solve the reformulated problem of the beamforming and PS ratio.