Outage probability and throughput analysis of rate-splitting multiple access in shadowing environments

In this paper, a two users Rate-Splitting Multiple Access (RSMA) system is considered under shadowing environments that follow the log-normal distribution. The RSMA scheme offers an improved interference management capability and low complexity when compare to the Non-Orthogonal multiple access (NOMA) and Orthogonal Multiple Access (OMA) schemes. Closed-form analytical expressions are derived for the outage probability and system throughput of the proposed RSMA system. To minimize the system outage, we propose two distinct optimization algorithms, such as a dual-loop nested bisection algorithm and a gradient-driven joint power and rate splitting algorithm. Numerical results shows that the proposed system achieves better outage performance and system throughput when compare to the NOMA and OMA schemes especially in high interference environments. Furthermore, a fundamental trade off between the target data rates and system reliability is studied which is crucial for designing the next generation wireless communication system under shadowing regions.