Research On Key Techniques Of Joint Transceiver Optimization In Wireless Energy Transfer Systems

With the rapid development of the key standard technology in 5G mobile communication,limited energy storage limits the lifetime of wireless networks.Energy consumption has become a key problem to be solved in the rapidly developing wireless communication technology.As a new solution to provide convenient and permanent energy for wireless networks,wireless power transfer(WPT)is considered to be a promising technology to achieve permanent transmission in traditional energy-constrained systems.This paper proposes a series of WPT systems under 5G environment.Combining full duplex technology,relay technology and MIMO,the conventional beamforming and magnetic beamforming of transceiver are carried out by convex optimization methods,so as to improve the power transmission efficiency(PTE)and capacity of long-range communication and mid-range power transfer systems.The main contents and innovations of this paper are as follows:1.Full-duplex Relay Systems Where Destination Node Equipped With Power TransferA MIMO amplify-and-forward(AF)relay system based on full-duplex communication mode and WPT technology is proposed,which realizes the uninterrupted transmission of information and energy at the same frequency in a real sense.The mean square error(MSE)minimization problem under perfect channel state information(CSI)is established to optimize the joint design of beamforming matrix of transmitter and relay as well as the decoding matrix of receiving node.We introduce the idea of alternating optimization(AO)method to decouple the original problem into three sub-problems,and solve the sub-problems through the idea of successive convex approximation(SCA).In addition,a new low-complexity algorithm based on channel parallelization(CP)and singular value decomposition(SVD)theory is proposed to reduce the computation complexity.The minimum MSE and bit error rate(BER)calculated under different algorithms are compared by simulation,which verifies the validity of theoretical analysis.Main innovations:Aiming at the problem of time delay and self-interference in a full-duplex WPT relay system,a solution is proposed to minimize the negative impact of full-duplex.An optimization algorithm based on SCA is proposed.Aiming at the high complexity of the algorithm,a CP and eigenvalue decomposition algorithm is proposed to greatly improve the performance of the algorithm.2.Full-duplex Relay Systems Where Relay Node Equipped With Power Transfer.Considering the existence of channel estimation error,we propose a full-duplex MIMO AF relay system with a PS receiver at relay to study the robustness of the relay system.Based on MSE,the beamforming matrices of transmitting node,relay node and receiving node are optimized jointly by guaranteeing the transmission power and receive power constraints of transmitting node and receiving node.Using the idea of semi-definite relaxation(SDR),the NP-hard problem is solved by an alternating iteration algorithm which can be proved to be convergent.Also,we give a closed-form solution for the transmit beamformer to reduce the computational complexity.Finally,the robustness of the whole system against channel uncertainties is discussed.Main innovations:An optimization algorithm based on SDR is proposed,and it is proved that an optimal solution can always be obtained through the proposed algorithm.A closed-form algorithm is proposed to reduce the complexity,and the original non-convex problem is solved by proposing and proving an effective theorem,so as to improve the robustness of the system.3.Half-duplex Bidirectional Relay Wireless Power Transfer SystemsIn order to further improve the spectrum efficiency,this paper proposes a two-way MIMO AF relay WPT system under half-duplex mode,which can effectively improve the spectrum efficiency and transmission range of the system.In order to solve the problem,an AO algorithm based on generalized singular value decomposition(GSVD)is proposed to jointly optimize the beamforming matrices of source nodes and relay node guaranteeing the transmit and receive power constraints.In addition,in order to further optimize the performance of the system,we propose an iterative refinement algorithm based on SCA.Finally,the simulation results show that the proposed two algorithms can achieve satisfactory MSE performance.Main innovations:Introducing CP method into the complicated two-way relay system analysis,the high-dimensional vector problem caused by two-way relay and multi-hop relay can be scaled.Unlike the existing scalar CP algorithms,this study simplifies the original problem directly to a linear convex problem,which greatly reduces the complexity of the algorithm.4.2x2 Magnetic Resonance Charging SystemsA 2x2 magnetic resonance charging system for biomedical field or wearable devices is proposed.The influence of phase difference between transmit currents,currents in transmit coils and resistances of receive coils on PTE is analyzed.Adjusting amplitude of the currents in transmit coils and resistances of the receive coils at the same time,the total power of receive coils is maximized.The electric and magnetic fields are simulated by MATLAB and COMSOL from different aspects.The numerical results show that the proposed system and optimization algorithm can effectively improve the PTE in mid-range application.Major innovations:Adjusting amplitude of the currents in transmit coils and resistances of the receive coils at the same time,the total power of receive coils is maximized.The proposed algorithm is based on iteration to solve a series of geometric programming(GP)problems,where the optimal solution can be obtained without decoupling the original problem with multi-variable coupling.