RIS-NOMA-Assisted Short-Packet Communication with Hardware Impairments

To address the stringent demands of next-generation networks for massive connectivity, ultra-low latency, and ultra-high spectral efficiency, the win-win integration of reconfigurable intelligent surface (RIS) and nonorthogonal multiple access (NOMA) is considered as a promising solution. In this paper, we investigate a downlink RIS-empowered NOMA system with short packet communications (SPC) in the presence of hardware impairments at the transceiver nodes. To characterize the performance of the proposed network, the approximate and asymptotic closed-form expressions of average block error rate (BLER) at far and near users are derived and analyzed. Based on asymptotic average BLER in high signal-to-noise ratio regime, the diversity order, minimum blocklength, and optimal power allocation are examined. RIS exhibits an improvement in diversity order and minimum blocklength. The achieved results show that users with poorer channel conditions have less sensitivity to hardware impairments whether for near users or RIS-assisted far users. Furthermore, our results manifest the benefits of NOMA and RIS in SPC over the benchmark orthogonal multiple access (OMA) scheme.