Channel Statistics-Based Rate Splitting with Spatial Randomness

Multiple access schemes based on non-orthogonality are potential solutions to the requirements of the future wireless communications for enhancing the spectral efficiency. This paper investigates the performance of a generalization of the well-known power domain non-orthogonal multiple access (NOMA) scheme; the so-called rate splitting (RS). We consider fixed power allocation and by following a probabilistic approach, we provide an analytical framework on the RS scheme. Specifically, we capture spatial randomness and based on the channel statistics, we provide closed-form expressions for the distributions of the signal-to-interference-plus-noise ratio at the receivers. Furthermore, we derive the average rate achieved at each receiver and we show how the different design parameters impact the individual rates. Our results highlight the flexibility of RS against NOMA in terms of fairness performance.