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

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.