Efficient Grant-Free Uplink NOMA With Multi-IRS and Sidelink Relays for IIoT-Driven Smart Factories

Abstract

Industry 5.0 requires advanced communication systems to enable smart factories. These systems must ensure seamless and resilient communication alongwith efficient resource management. To address this, we propose a system model integrating intelligent reflecting surfaces (IRSs), grant-free non-orthogonal multiple access (GF-NOMA), and full-duplex (FD) sidelink relays to enhance reliability, connectivity and spectral efficiency. A dynamic penalty-based particle swarm optimization (DYN-P-PSO) method is adopted for power and phase-shift allocation across multiple IRSs, under Nakagami-m fading conditions aiming to maximize the sum rate of all the devices. The study also investigates the impact of IRS positioning, providing insight into improving communication in industrial internet-of-things (IIoT) deployments with reduced capability (RedCap) devices. The results show that the proposed approach achieves a significant sum rate gain upto ≈ 70% over conventional and comparable schemes. © 2025 Elsevier B.V., All rights reserved.