Performance Of Multi-RIS-Aided Uplink Wireless Systems With Short-Packet Communications

Abstract

Reconfigurable Intelligent Surfaces (RISs) have been recently recognized as a revolutionary technology for optimizing wireless propagation environments, offering significant enhancements in throughput, latency, and reliability. Concurrently, short-packet communications have gained prominence as a critical enabler for low-latency, mission-critical applications. This study investigates the performance characteristics of multi-RIS-based uplink transmission systems with short-packet communication over Rayleigh fading channels. Two base station (BS) combination schemes including maximal-ratio combining and selection combining, to determine the optimal RIS of the given distributed set, are analyzed. To evaluate system performance, both closed-form and asymptotic expressions are derived in two RIS phase-shift scenarios that are random phase-shift (RPS) and optimal phase-shift (OPS) for throughput, latency, and reliability. Our numerical analysis demonstrates that increasing the number of distributed RISs, along with additional passive elements, effectively mitigates the limitations of both RPS and OPS scenarios. Consequently, the BS can maintain the target block error rate (BLER) while reducing the antenna count. Finally, Monte-Carlo simulations are presented to validate the accuracy of the theoretical analysis with respect to throughput, latency, and reliability.