Intelligent Rate-Splitting Multiple Access-Enabled Coordinated Direct and Relay Transmission

In this letter, we propose an intelligent rate-splitting multiple access (RSMA)-enabled coordinated direct and relay transmission (CDRT) scheme, in which transmissions from a pair of the far and near users to a base-station are coordinated by a decode-and-forward relay. In contrast to existing published concepts, near-user (NU) is switched on/off intelligently across the two time phases to exploit RSMA to enhance transmission reliability and improve throughput of far-user (FU), while ensuring the desired performance at NU. The optimal transmit power allocation factors that maximize the achievable rates of the dual-hop transmissions are derived, respectively. For the delay-limited transmission mode, closed-form expression is extracted for the end-to-end outage probability of FU and asymptotic outage performance is studied in the high signal-to-noise ratio region. For the delay-tolerant transmission mode, analytical expression is also derived for the end-to-end ergodic rate of FU, and the effective sum rate is characterized. Numerical results validate the theoretical analysis and highlight the superior performance of the proposed RSMA-enabled CDRT scheme over the existing benchmark schemes in terms of reliability and throughput.