Exact and Approximate Outage Analysis of Partial-CSI SWIPT Opportunistic AF Relay Networks over Rayleigh Fading

This work investigates the outage characteristics of a simultaneous wireless information and power transfer (SWIPT) opportunistic amplify-and-forward (OAF) relay network operating over Rayleigh fading channels. In the considered setup, each relay adopts a power-splitting (PS) protocol that divides the received radio-frequency signal for concurrent energy harvesting and data relaying. By formulating the partial channel state information (CSI)-based SWIPT OAF scheme as an equivalent generalized non-SWIPT relay model, tractable analytical expressions are derived to approximate the outage probabilities of both the indirect and combined transmission links, yielding reliable estimates of the true system behavior. Furthermore, an exact closed-form expression for the indirect link outage probability is obtained. Monte Carlo simulations confirm that the proposed analytical framework accurately captures the outage performance under a wide range of signal-to-noise ratio (SNR) conditions and relay selection scenarios. The developed analysis provides a convenient and insightful means for evaluating and optimizing SWIPT-assisted wireless sensor systems, thereby supporting their practical realization in energy-limited scenarios such as wireless sensor and Internet of Things (IoT) networks.