Reliability and Sensing Analysis of IRS-Assisted NOMA ISAC for IoT Networks

Future intelligent wireless networks require reliable and spectrum-efficient communication while simultaneously supporting environmental sensing. Integrated Sensing and Communication (ISAC) enables this integration through shared wireless resources; however, multiuser communication in dense and blockage-prone environments remains challenging. This paper proposes a full-duplex Intelligent Reflecting Surface (IRS)-assisted Non-Orthogonal Multiple Access (NOMA)-ISAC framework for simultaneous uplink/downlink communication and target sensing. Considering co-channel, self-loop, and target-induced interference, outage probability (OP) and probability of detection (PoD) are derived over Nakagami-m fading channels. The analysis shows that increasing transmit power and IRS elements improves far-user reliability and sensing performance, whereas IRS-enhanced multiuser interference can degrade uplink near-user performance, revealing a fundamental reliability tradeoff. Simulations validate the analysis and demonstrate superior communication and sensing performance over conventional NOMA-ISAC systems. The proposed framework offers a promising solution for reliable and energy-efficient intelligent wireless networks.