Rate-Splitting Multiple Access With Active RIS for Ultra-Reliable and Low-Latency Communication Enhancement

In this paper, we address the critical challenges posed by Ultra-Reliable and Low-Latency Communication (URLLC), a cornerstone requirement in 5G and future 6G mobile networks, where stringent latency and reliability constraints complicate the achievement of quality-of-service (QoS). To overcome these limitations, we propose a novel integration of rate-splitting multiple access (RSMA) and active reconfigurable intelligent surfaces (ARIS) within a short packet communication (SPC) framework. This design leverages SPC and ARIS to address latency and reliability challenges, while RSMA enhances spectral efficiency, mitigates interference, and ensures equitable resource allocation among users. By deriving the cumulative distribution functions (CDFs) of the signal-to-interference-plus-noise ratio (SINR) for common and private streams, we obtain closed-form expressions for the block error rate (BLER) and the average achievable rate (AAR) under the influence of imperfect successive interference cancellation (SIC), using linearization-based approximations. Numerical evaluations reveal that the proposed RSMA-ARIS framework significantly outperforms conventional RSMA-passive RIS and non-orthogonal multiple access (NOMA)-RIS systems in terms of both BLER and AAR. Furthermore, the impacts of power allocation, block length, and the number of RIS elements on system performance are systematically analyzed, leading to the proposal of several strategies for further BLER reduction. The accuracy of the analytical results is validated through Monte Carlo simulations, highlighting the robustness and efficacy of the proposed approach.