Performance Analysis of FD C-NOMA With Intelligent TS and Battery Management in Non-Linear Energy Harvesting Networks

Abstract

Driven by the demands of 5G/6G and internet of things (IoT) for extensive connectivity and enhanced spectral efficiency, this paper presents a full-duplex (FD) cooperative non-orthogonal multiple access (C-NOMA) framework that incorporates a battery-assisted practical non-linear energy harvesting (NL-EH) model. The three-node downlink network features a multi-antenna base station serving a near user (NU) (functioning as an FD relay) and a far user (FU) that employs maximal ratio combining (MRC) to process direct and relayed signals. We introduce an intelligent dynamic battery energy (DBE) management scheme that calculates the precise energy deficit per symbol required to exactly achieve target transmit power per symbol interval, ensuring stable QoS while minimizing the long-term ergodic battery energy consumption per symbol ( $\bar {Q}_{b}$ ) compared to fixed battery energy (FBE) methods. Concurrently, an adaptive dynamic time-switching (TS) protocol utilizes real-time channel state information (CSI) to optimize the EH time fraction, mitigating self-loop interference outages and adhering to energy causality constraints. A comprehensive mathematical framework derives exact closed-form expressions for outage probability, delay-limited throughput, ergodic capacity, and $\bar {Q}_{b}$ across these schemes. High-SNR asymptotic analyses demonstrate that, while an NL-EH architecture results in a zero-diversity error floor, integrating the direct link restores spatial diversity. Additionally, while perfect successive interference cancellation (SIC) enables continuous capacity growth, practical imperfect SIC leads to a zero high-SNR slope due to the dominance of interference. We found critical throughput starvation in the dynamic TS DBE scheme at high SNRs and propose enforcing a minimum IT fraction constraint or adopting a continuous non-linear mapping to ensure effective communication. We demonstrate selecting quantum of battery energy per symbol and TS parameter is crucial for achieving maximum FU throughput while ensuring a target throughput for the NU. Extensive simulations show the proposed dynamic TS and DBE frameworks outperform static benchmarks.