Transmission Scheme, Detection and Power Allocation for Uplink User Cooperation with NOMA and RSMA

TL;DR

This paper introduces two innovative uplink user cooperation schemes, C-NOMA and C-RSMA, utilizing full-duplex transmission, rate-splitting, and advanced detection to enhance spectral efficiency and fairness.

Contribution

The paper proposes novel cooperative schemes with optimized power allocation and detection methods, achieving improved spectral efficiency and diversity in uplink NOMA and RSMA systems.

Findings

Achieve diversity order of two.

Maximize minimum user rate with proposed algorithms.

Confirm performance improvements through simulations.

Abstract

In this paper, we propose two novel cooperative-non-orthogonal-multiple-access (C-NOMA) and cooperative-rate-splitting-multiple-access (C-RSMA) schemes for uplink user cooperation. At the first mini-slot of these schemes, each user transmits its signal and receives the transmitted signal of the other user in full-duplex mode, and at the second mini-slot, each user relays the other user's message with amplify-and-forward (AF) protocol. At both schemes, to achieve better spectral efficiency, users transmit signals in the non-orthogonal mode in both mini-slots. In C-RSMA, we also apply the rate-splitting method in which the message of each user is divided into two streams. In the proposed detection schemes for C-NOMA and C-RSMA, we apply a combination of maximum-ratio-combining (MRC) and successive-interference-cancellation (SIC). Then, we derive the achievable rates for C-NOMA and C-RSMA, and formulate two optimization problems to maximize the minimum rate of two users by considering the proportional fairness coefficient. We propose two power allocation algorithms based on successive-convex-approximation (SCA) and geometric-programming (GP) to solve these non-convex problems. Next, we derive the asymptotic outage probability of the proposed C-NOMA and C-RSMA schemes, and prove that they achieve diversity order of two. Finally, the above-mentioned performance is confirmed by simulations.