Outage Performance of A Unified Non-Orthogonal Multiple Access Framework

TL;DR

This paper proposes a unified NOMA framework applicable to code-domain and power-domain NOMA, analyzing outage probabilities and throughput, considering imperfect and perfect SIC, and demonstrating the impact of residual interference on performance.

Contribution

It introduces a comprehensive framework for NOMA, deriving exact and asymptotic outage expressions, and analyzing the effects of residual interference on system performance.

Findings

Outage probability converges to an error floor with imperfect SIC at high SNR.

CD-NOMA outperforms PD-NOMA in outage behavior.

Residual interference significantly impacts the diversity order.

Abstract

In this paper, a unified framework of non-orthogonal multiple access (NOMA) networks is proposed, which can be applied to code-domain NOMA (CD-NOMA) and power-domain NOMA (PD-NOMA). Since the detection of NOMA users mainly depend on efficient successive interference cancellation (SIC) schemes, both imperfect SIC (ipSIC) and perfect SIC (pSIC) are taken into considered. To characterize the performance of this unified framework, the exact and asymptotic expressions of outage probabilities as well as delay-limited throughput for CD/PD-NOMA with ipSIC/pSIC are derived. Based on the asymptotic analysis, the diversity orders of CD/PD-NOMA are provided. It is confirmed that due to the impact of residual interference (RI), the outage probability of the n-th user with ipSIC for CD/PD-NOMA converges to an error floor in the high signal-to-noise ratio (SNR) region. Numerical simulations demonstrate that the outage behavior of CD-NOMA is superior to that of PD-NOMA.