PERFORMANCE EVALUATION OF OUTAGE PROBABILITY IN COOPERATIVE NON-ORTHOGONAL MULTIPLE ACCESS NETWORKS WITH ADAPTIVE POWER SPLITTING

Abstract

The amalgamation of cooperative Non-Orthogonal Multiple Access (NOMA) with Simultaneous Wireless Information and Power Transfer (SWIPT) is a promising technology for addressing energy bottlenecks and extending the lifetime of wireless networks. The traditional Fixed Power Splitting (FPS) is the most widely adopted protocol in SWIPT-assisted cooperative NOMA systems due to its simplicity and ease of implementation. However, the fixed nature of its Power Splitting (PS) ratio makes it inefficient under dynamic wireless channel environments, leading to insufficient Energy Harvesting (EH) and reduced decoding capability, as it cannot adapt to fluctuating channel conditions. This study proposes an Adaptive Power Splitting (APS) protocol at the near user, where the PS ratio is dynamically adjusted in accordance with the instantaneous channel condition. This work considered a system model that consists of a single source, a near user acting as a Decode-and-Forward (DF) relay, and a far user. The APS protocol enables the near user to allocate energy for simultaneous EH and Information Decoding (ID). Closed-form expressions are derived for the Outage Probabilities (OPs) of the users under Rayleigh fading channels. Numerical evaluations are carried out to analyze the system outage performance in terms of Signal-to-Noise Ratio (SNR), energy conversion efficiency, user distance, PS, and Power Allocation (PA) ratio. Simulation results demonstrate that the APS NOMA scheme outperforms both the FPS NOMA and Orthogonal Multiple Access (OMA) schemes, reducing OP significantly across a range of SNRs, making it highly effective for reliable and energy-efficient communication in future wireless networks.