Performance Enhancement of Incremental Cooperative NOMA via Partial Relay Selection

Improving spectrum efficiency (SE) and energy efficiency (EE) remains a fundamental requirement for future wireless communication systems. To address this, we present a novel cooperative relaying strategy built on Incremental Relaying with Partial Relay Selection (IR-RS) using a Decode-and-Forward (DF) protocol (IR-RS-DF), tailored for Cooperative Non-Orthogonal Multiple Access (C-NOMA) networks. In this approach, a near user (NU) is selected dynamically based on its instantaneous signal-to-noise ratio (SNR) to serve as a DF relay for assisting a far user (FU), especially when the FU suffers from poor direct transmission conditions. To enhance energy utilization, the system incorporates a feedback-aided incremental relaying mechanism, which selectively engages relays only when necessary, thereby avoiding unnecessary retransmissions and reducing power consumption. We conduct a comprehensive statistical evaluation of key performance metrics such as bit error rate (BER), ergodic capacity (EC), system throughput, outage probability (OP), SE, and average energy savings over Rayleigh fading channels. Simulation outcomes validate that the proposed IR-RS scheme, when integrated with C-NOMA, consistently outperforms conventional IR-DF approaches across all evaluated parameters, showcasing its effectiveness for high-efficiency and energy-aware next-generation wireless networks.