A Rate-Splitting Non-Orthogonal Multiple Access Scheme for Uplink Transmission

In existing uplink non-orthogonal multiple access (NOMA) schemes, complicated user pairing schemes are required to ensure differentiated arriving power at the access point, which may incur considerable scheduling overhead. To address this issue, we propose a novel rate-splitting NOMA scheme in this paper. In particular, each user information is "split" into multiple flows, which equivalently form multiple virtual users. These information flows can be successively decoded with even the same arriving power, thus avoiding user paring and significantly reducing the scheduling complexity. We derive the exact closed-form expressions of the outage probability and achievable sum rate of the proposed scheme. Moreover, we provide a practical method to optimize the key parameters, i.e., rate splitting pattern and power spitting pattern, so as to further improve the performance. Finally, simulation results validate the effectiveness of the proposed scheme.