Outage Probability Analysis of RIS-assisted Wireless Powered Multi-user Communications

This paper investigates the outage performance of reconfigurable intelligent surface (RIS)-assisted wireless powered multi-user communication networks (WPMCNs) consisting of a base station (BS), an RIS, multiple users as well as a power beacon (PB). Depending on the availability of wireless channel state information (CSI) in the RIS-aided networks, we propose two energy-harvesting (EH) user scheduling schemes, namely the time switching (TS) based round-robin scheduling (TS-RRS) and the TS based maximum capacity scheduling (TS-MCS) scheme. By leveraging the central limit theorem (CLT) approximation, we derive closed-form outage probabilities (OPs) for the two schemes, based on which their OPs are further minimized through the optimization of TS allocation ratio in the WPMCN. Our numerical evaluations demonstrate that obvious outage benefit from large number of independent reflectors is observed in the TS-MCS scheme of the RIS-aided WPMCNs. Moreover, the outage performance of RIS-aided WPMCNs can be notably improved by proper joint design of information and energy transmission.