Research On Simultaneous Wireless Information And Power Transfer Based On Time Reversal

At present,wireless communication technology represented by 5G is speeding up its close integration with transportation,medical and energy industries,such as autonomous cars,medical Internet of things and simultaneous wireless information and power transfer(SWIPT).Among them,the SWIPT,which can simultaneously use the received signal for charging and signal processing,is firmly attracting people's attention because of its broad application prospect in the background of the new-generation energy revolution.However,compared to conventional signal processing or wireless charging,the simultaneous processing of SWIPT undoubtedly brings about the complexity of the processing and the equipment.The fundamental reason is that the power intensity used for signal processing or energy charging is reduced,so the operation like signal amplification and low power adaptation is needed,and different operations often depend on different hardware.In addition,like other wireless communication technologies,SWIPT also has problems with interference,security,and health.Time reversal(TR)is a signal processing technology that can enhance the intensity of predefined target signals by using space-time focusing,and has great research potential in anti-interference,anti-eavesdropping and medical health of wireless communication.Considering the introduction of TR in SWIPT,the main research contents of this paper are as follows:Firstly,SWIPT is a green communication technique that can decode information and collect energy simultaneously.However,the problems such as the antenna correlation,the feeble receiving signal power,the small collected energy,greatly restrict the area of rate-energy region and the accuracy of theoretical value.In order to solve these problems,this paper proposed an improved transmission scheme of TR-SWIPT technique.Considering a multiple-input and single-output(MISO)for wireless communication system,the proposed scheme introduces TR and Kronecker model into SWIPT,which uses unique spatial and temporal focusing effects of TR to improve the signal strength at receiving end,and uses Kronecker model to analyze the transmission process under antenna correlation by theoretical modeling.Monte Carlo simulation results verify the accuracy of the theoretical values under different conditions,and performance comparison with other transmission scheme proves that the proposed scheme has a larger area of rate-energy region and a better performance.Secondly,for the problem of energy efficiency(EE)in SWIPT,while meeting the constraints of communication service quality and harvesting energy,an optimization algorithm based on TR is proposed to maximize the EE.First of all,TR is introduced into the SWIPT to construct a new transmission scheme,and the closed-form expression of EE is derived.Secondly,through formulating and analyzing for the problem,finding it is a two-element fractional non-convex problem,and can be transformed into a convex optimization problem by mathematical transformation.Finally,this problem is solved by Dinkelbach algorithm and CVX.Simulation results show that when the search accuracy,decoding noise power,maximum transmit power,and signal-to-noise ratio(SNR)increase,the optimized EE will also increase,and when the constraints are met,the proposed algorithm can significantly increase the EE and improve system performance.Thirdly,for the problem of green-secure communication in simultaneous wireless information and power transfer network,a green-secure SWIPT scheme of TR with artificial noise(AN)is proposed.Under the general eavesdropping channel,the proposed scheme introduces TR into the SWIPT with AN to complete channel modeling,and utilizes TR's spatial-temporal focusing effect to improve the privacy signal received by the legitimate receiver.In addition,unlike the existing linear energy conversion and eavesdropping decision models,the proposed scheme considers non-linear energy conversions that are closer to reality and views the wireless energy charging behavior of energy receivers from the perspective of potential eavesdroppers.Simulation results show that increasing the SNR,number of antennas,antenna transmit power,privacy signal power,and power split ratio can improve the system's privacy energy efficiency,and the comparison with other transmission schemes verifies the green-secure features of the proposed scheme.