Rate-Splitting and NOMA-Enabled Uplink User Cooperation

Abstract

In this paper, we propose two novel transmission and detection schemes based on rate-splitting (RS) and non-orthogonal-multiple-access (NOMA) for uplink user cooperation. At the first mini-slot of these cooperative schemes, each user transmits its signal and receives the transmitted signal of the other user, and at the second mini-slot, each user relays the other user’s message with amplify-and-forward (AF) protocol. To achieve better spectral efficiency, users transmit their signals in non-orthogonal mode in both mini-slots. We propose two detection schemes for these proposed cooperative (C)-NOMA and cooperative-rate-splitting-multiple-access (C-RSMA) schemes in which we apply a combination of maximum-ratio-combining (MRC) and successive-interference-cancellation (SIC). Finally, we derive the achievable rates corresponding to the C-NOMA and C-RSMA schemes. Simulation results prove the superiority of the proposed C-NOMA and C-RSMA schemes rather than cooperative-orthogonal-multiple-access (C-OMA) and non-cooperative schemes.