Energy Efficiency Analysis And Optimization Of SWIPT-based Full Duplex Relay Cooperative System

The worldwide spread of 5G and the further expansion of communication network scales have increased the demand for spectrum resources.Full Duplex(FD)technology can use the same frequency band to send and receive signals at the same time,which is expected to alleviate the problem of spectrum resource tension.Applying FD technology to the relay cooperative communication system can further improve the system transmission rate and spectral efficiency,and reduce transmission delay.In addition,due to the impact of the diversity of communication services,the demand for user data traffic has increased dramatically,and various network architectures has continuously expanded,which has greatly increased energy consumption and operating costs.The shortage of resources,coupled with the sharp increase in energy consumption,has caused widespread concern about the optimization of energy efficiency,and improving energy efficiency will become the trend of future wireless communications development.At the same time,as one of the important topics of green communication,Simultaneously Wireless Information and Power Transfer(SWIPT)technology has solve the problem that the life of wireless terminals is limited by battery capacity,and has attracted widespread attention from researchers.Therefore,this paper studies the energy efficiency optimization of a full-duplex relay cooperative system based on SWIPT technology.Firstly,a three-node SWIPT-based full duplex(FD)relay cooperative system model is established.The source and destination nodes are configured with a single antenna and are powered by the external device.The relay node is configured with two antennas and simultaneously implements information decoding and energy harvesting through SWIPT.For the power-splitting protocol,it is proved that the energy efficiency formula is a convex function with respect to the power-splitting factor,and the optimal power-splitting factor is obtained to maximize energy efficiency.At the same time,this paper studies the scheme to improve the energy efficiency of the system by optimizing the source transmission power.Furthermore,a joint optimization algorithm based on iteration is proposed to jointly optimize the power-splitting factor and transmission power.Compared with the maximum energy efficiency obtained by optimizing only the power-splitting factor or transmission power,the joint optimization algorithm can achieve higher energy efficiency.In addition,the algorithm has fast convergence speed,small system delay,low implementation complexity,and meets the requirements of real-time communication.Then,considering the impact of user's Quality of Service(QoS)requirements on maximizing energy efficiency,we study energy efficiency optimization for SWIPT FD relay cooperative system based on QoS guarantee.We set a constant Signal to Interference plus Noise Ratio(SINR)as QoS constraints,and re-determine the range of the system's transmission power and power-splitting factor to optimize the system energy efficiency.The objective function is more complicated,so fractional programming is used to transform the objective function of the fractional form into a subtractive form.Based on this,an iterative optimization algorithm based on QoS guarantee is proposed to maximize system energy efficiency.Finally,if the self-interference cancellation(SIC)processing efficiency is low,the relay will suffer severe residual self-interference due to its own transmitted signal,so the FD SIC is not ideal.In this case,it is assumed that the received residual self-interference signal power is much higher than the additive Gaussian noise power of the relay node,that is,the energy efficiency of the system is analyzed without considering the relay noise.The analysis shows that the optimization problem is equivalent to the maximum-minimum problem.Therefore,the conventional maximum-minimum solution can be used to determine the relationship between the optimal transmission power and the optimal power-splitting factor,and the optimization solution is solved by the Dinkelbach method.Finally,through analysis of simulation results,it is found that meeting a certain QoS requirement will cause a certain degree of energy efficiency decline,and as the minimum QoS constraint increases,the energy efficiency will also decrease to a certain extent.