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

Wireless communication network is a kind of communication system which uses electromagnetic wave to transmit and receive signals.Compared with traditional wired communication network,it has the characteristics of wide frequency band,high capacity and flexible use.It can effectively solve the disadvantages and shortcomings of traditional wired communication network.At present,it is widely used in industrial production,network communication,personal communication and other fields.With the development of the times,the wireless communication network has experienced explosive growth.The communication technology has developed rapidly from 2G to 3G and 4G and the 5G era is coming,the achievable rate and accessible users in 5G era are about one hundred times or even one thousand times of 4G.However,in order to achieve higher speed and larger bandwidth,the energy consumption is also growing rapidly,which leads to the decline of energy efficiency.Therefore,how to improve energy efficiency has become an urgent problem in the field of communication.In order to solve this problem,Simultaneous Wireless Information and Power Transfer(SWIPT)came into being.This technology can absorb the radio frequency(RF)signals of the surrounding environment to decode information and harvest energy at the same time.This technology not only guarantee the required target rate of the system,but also can be used to supplement the energy consumption of the system,thereby improving energy efficiency.There are three commonly used methods of SWIPT technology: Power Splitting(PS),Time Switching(TS),and Antenna Selection(AS).However,these three methods need to provide an additional distributor at the receiver,which increases the design and implementation complexity of the communication system.In wireless communication networks,this paper combines Orthogonal Frequency Division Multiplexing(OFDM)technology with SWIPT technology,and uses different subcarriers to simultaneously implement information decoding and energy harvesting.Not only reduces the design and implementation complexity of the receiver,but also maximizes the harvested energy under the condition of meeting the minimum transmission rate of the user,which significantly reduces system energy consumption and significantly improves system energy efficiency.The main work and achievements of this paper are as follows:(1)Aiming at the problem that the existing methods based on SWIPT technology to improve the system energy efficiency need to add additional distributors,this paper first presents an energy efficiency optimization method based on OFDM Simultaneous Wireless Information and Power Transfer.In this method,we consider the energy efficiency optimization in single user system and multi-user system.In the single user system,the base station sends information directly to the user.The user uses different subcarriers to achieve parallel transmission of information and energy.We study how to optimize the power and subcarrier allocation,so as to maximize the system energy efficiency when the user reaches the minimum transmission rate.Furthermore,we study how to improve the energy efficiency of multi-user system.Similar to single user system,each user has the minimum transmission rate.We also jointly optimize the power and subcarrier allocation to maximize the system energy efficiency.The simulation results show that the proposed method can significantly improve the energy efficiency of the system without increasing the complexity of the system.(2)In the actual communication process,when the distance between the two sides of the communication is large,the energy efficiency of the system is often not ideal.So we use the characteristics of cooperative relay technology to effectively improve the transmission rate and expand the coverage and then propose an energy efficiency optimization method based on OFDM Simultaneous Wireless Information and Power Transfer Relay Cooperative Communication to further improve the system energy efficiency.We equally divide the transmission time into two time slots.In the first time slot,the base station transmits information to the relay node,the relay node utilizes SWIPT technology to decode information by using a part of the subcarriers,and uses the remaining subcarriers to harvest energy.In the second time slot,the relay node uses the energy harvested in the first time slot to help forward information to the user.We study how to jointly allocate resources such as power and subcarriers to maximize the system energy efficiency while guaranteeing the user can reach the minimum transmission rate in two cooperative relay modes: Decode-and-Forward and Amplify-and-Forward.The simulation results show that the proposed method can achieve higher energy efficiency than other algorithms.