| With the booming development of the Internet of Things(Io T),wireless radio frequency(RF)energy transmission has proposed a new solution to solve the energy supply problem that wireless Io T devices face.However,due to the wireless channel Path loss,shadow and multipath attenuation,as well as long distance transmission,leads to inefficient energy transmission and poor system availability.Intelligent reflecting surface(IRS)technology is capable of reconfiguring the wireless propagation environment by adjusting the phase-shift of a large number of integrated low cost passive reflecting elements.It can significantly improve the energy transmission efficiency and signal transmission quality.IRS-assisted wireless powered communication is a promising solution for future Io T communication networks.To quantify the gain achieved by IRS in the RF powered Io T communication network,this paper considers an IRS-assisted RF powered Io T communication network.A theoretical framework for performance analysis of the IRS-assisted RF powered Io T communication system is proposed,which provides a theoretical basis for the deployment of the actual system.The main work content of this paper includes the following aspects:(1)Aiming at the IRS-assisted large-scale RF powered Io T communication network operating in Sub-6GHz band,considering the spatial random distribution characteristics of Io T devices and IRS as well as the random fading characteristics of wireless channels,a theoretical framework for network performance analysis was constructed by using mathematical tools such as stochastic geometry and probability theory.Firstly,the cascaded channel with IRS is modeled,and the power distribution of the receiving end energy signal and data signal,as well as the interference signal,is analyzed after typical IRS adopts beamforming technology.Furthermore,easy expressions for important performance indicators such as energy coverage probability,uplink coverage probability,overall coverage probability,average spatial throughput,and power efficiency were derived to quantify the gains of IRS in the energy harvesting stage and uplink data transmission stage.(2)Aiming at the IRS-assisted RF powered Io T communication network working in the millimeter wave band,taking into account the high path loss characteristics of millimeter wave,directional beamforming is used at the base station side and the user side,and passive beamforming is adopted at the typical IRS side,so as to construct the theoretical framework of network performance analysis.First,the cascaded channel with IRS is modeled to analyze the power distribution of the receiving end energy signal and data signal,as well as the power distribution of interference signal.Furthermore,simple expressions for important performance indicators such as energy coverage probability,uplink coverage probability,overall coverage probability and average spatial throughput are derived to quantify the gains of IRS in the energy harvesting stage and data transmission stage respectively in the millimeter wave frequency band.(3)Aiming at the theoretical analysis framework of network performance constructed in research contents(1)and(2),this paper used Mathematica software to calculate the numerical results and MATLAB software to build a simulation platform to verify the correctness of the theoretical analysis.Further,this paper quantitatively analyzed the influences of IRS density,IRS reflection element,charging and transmission time slot ratio and other key system parameters on network performance indexes,and provided some guiding suggestions for the actual system deployment.The results show that,compared with traditional RF-powered Io T communication networks that do not consider IRS,beamforming of IRS-reflected signals can significantly improve the network’s energy coverage probability and uplink coverage probability of successful transmission,and the charging and transmission time slot ratio,which aims at maximizing spatial throughput,remains unchanged. |
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