Research On Energy Efficiency Optimization Technology Based On Simultaneously Wireless Information And Power Transfer OFDM Systems

Lately,with the vigorous progress of the Internet of things(Io T)technology,the Internet of everything is becoming a reality.Internet of things nodes like sensors and other wireless access devices have witnessed explosive growth,which facilitates human production and life,but also makes the system energy consumption increase day by day.On the other hand,sensors and other wireless access devices rely on internal battery power supply.Limited battery capacity restricts the service time of sensor nodes.Thus,how to decrease the energy consumption of the system and solve the energy limitation of wireless access devices have become urgent issue for human beings.Radio Frequency(RF)energy collection technology can convert the collected radio frequency signal energy into electricity thus realizing wireless energy transfer.Simultaneous Wireless Information and Power Transfer(SWIPT)is suggested based on RF signals’ advantages of conveying information and carrying energy concurrently.SWIPT technology can harvest energy while decoding information.The energy collected can be used to power the system,thus enhance the Energy Efficiency(EE)of the system and solve the energy limitation problem of wireless access devices.In this study,SWIPT is applied to Orthogonal Frequency Division Multiplexing(OFDM)systems,we study the transmission scheme of OFDM downlink systems based on Power Splitting strategy.Firstly,a point-to-point downlink system of OFDM with SWIPT is studied based on PS strategy,and an energy efficiency optimization algorithm of SWIPT enabled OFDM system based on ellipsoid method is proposed.Secondly,the cooperative communication technology is brought in,to further improving EE,the method based on the cooperative communication SWIPT enabled OFDM system is studied.The main research work of this study is concluded as follows:1.Aiming at the PS strategy for OFDM downlink system with SWIPT,an energy efficiency optimization algorithm for SWIPT enabled OFDM system based on ellipsoid method is proposed with the optimization goal of energy efficiency.This algorithm uses ellipsoid method to update Lagrange multipliers,which can effectively accelerate the convergence speed and strengthen the quality of the algorithm.The simulation results indicate that the proposed EE optimization algorithm based on ellipsoidal method can effectively solve the resource allocation problem with the optimization goal of system EE.Compared with the subgradient method,the ellipsoidal method has faster convergence speed and can significantly reduce the algorithm complexity.2.On the basis of point-to-point downlink system,the cooperative communication technology is applied to the system so as to further improve the EE of the system,and the DF protocol is adopted to propose a relay cooperative SWIPT enabled OFDM system model.The information transmission of this system is divided into two phases.Specifically,the relay node firstly uses SWIPT technology to implement ID and EH operation on the received signals,and then utilize the energy collected in the first phase to forward the information to the destination node in the second phase.We set the EE of the system as the optimization objective and considering several constraints,the maximum EE of the system was obtained by jointly optimizing the power distribution and power splitting factor of two phases.Finally,the simulation experiment realized by MATLAB verified that the introduction of cooperative communication further improved the energy efficiency of the system.