Impact of RIS on Outage Probability and Ergodic Rate in Wireless Powered Communication

TL;DR

The paper addresses reliability challenges in wireless powered communication (WPC) for energy-constrained users and proposes a reconfigurable intelligent surface (RIS) to jointly boost energy transfer and information reception. It develops a RIS-WPC framework with phase-aligned RIS reflection, derives closed-form outage probability and ergodic rate under Rayleigh fading using a Gamma approximation for the cascaded channel sum $T$, and validates the results with Monte Carlo simulations. The contributions include a Gamma-based channel model with parameters $k$ and $w$, tractable expressions for $P_{Out}$ and $R_u$, and practical guidance on RIS size $M$ and power/time-splitting factors. The findings demonstrate substantial improvements in reliability and energy efficiency, enabling parameter optimization for RIS-WPC systems in future networks.

Abstract

Wireless powered communication (WPC) combines information and energy transmission for energy-constrained nodes. Reconfigurable intelligent surfaces (RISs) are capable of controlling radio signals in a dynamic and goal-oriented manner. This paper investigates the combination of RIS and WPC to enhance the performance of an energy-constrained user. Using an RIS, a base station, and a wireless user transmit energy and information signals, respectively. We derive closed-form expressions for outage probability and secrecy rate to analyze the performance of the proposed framework. Based on the theoretical analysis and simulation results, valuable insights are revealed and parameter selection is demonstrated.

Figures (3)

• Figure 1: RIS-WPC network with a generalized transmission frame structure.
• Figure 2: Outage probability vs. Number of RIS elements ($M$) for different transmission power of BS ($P_b$)
• Figure 3: Ergodic rate vs. Number of RIS elements ($M$) for different transmission power of BS ($P_b$)