NOMA-Based Cooperative Relaying with Receive Diversity in Nakagami-m Fading Channels

TL;DR

This paper analyzes the performance of a NOMA-based cooperative relaying system with multiple antennas in Nakagami-m fading, deriving closed-form expressions for ergodic rate and outage probability, and demonstrating its superiority over OMA in low-SNR regimes.

Contribution

It provides the first comprehensive performance analysis of CRS-NOMA with receive diversity schemes in Nakagami-m fading, including closed-form expressions and diversity order insights.

Findings

CRS-NOMA outperforms OMA in ergodic rate even at low SNR.

Full diversity order achieved with both SC and MRC schemes.

Optimal power allocation minimizes outage probability effectively.

Abstract

Non-orthogonal multiple access (NOMA) is being widely considered as a potential candidate to enhance the spectrum utilization in beyond fifth-generation (B5G) communications. In this paper, we derive closed-form expressions for the ergodic rate and outage probability of a multiple-antenna-assisted NOMA-based cooperative relaying system (CRS-NOMA). We present the performance analysis of the system for two different receive diversity schemes - selection combining (SC) and maximal-ratio combining (MRC), in Nakagami-m fading. We also evaluate the asymptotic behavior of the CRS-NOMA to determine the slope of the ergodic rate and diversity order. Our results show that in contrast to the existing CRS-NOMA systems, the CRS-NOMA with receive diversity outperforms its orthogonal multiple access (OMA) based counterpart even in the low-SNR regime, by achieving higher ergodic rate. Diversity analysis confirms that the CRS-NOMA achieves full diversity order using both SC and MRC schemes, and this diversity order depends on both the shape parameter m and the number of receive antennas. We also discuss the problem of optimal power allocation for the minimization of the outage probability of the system, and subsequently use this optimal value to obtain the ergodic rate. An excellent match is observed between the numerical and the analytical results, confirming the correctness of the derived analytical expressions.