Error Performance Analysis of Multi-user Detection in Uplink-NOMA with Adaptive $\mathcal{M}$-QAM

TL;DR

This paper analyzes the error performance of multi-user uplink NOMA systems with adaptive QAM, demonstrating that a joint maximum-likelihood detector can eliminate error floors and achieve full diversity in Rayleigh fading channels.

Contribution

It introduces a closed-form upper bound for BER in uplink NOMA with adaptive QAM and shows the effectiveness of the MRC-JMLD detector in diverse conditions.

Findings

MRC-JMLD completely eliminates the error floor.

The detector achieves full diversity order.

Analytical results match simulation outcomes.

Abstract

This work provides a generalized performance analysis for the multi-user uplink-NOMA system with adaptive square quadrature amplitude modulation (QAM) over Rayleigh fading channels. Motivated by the massive IoT connections and unavailability of orthogonal resources for each node, we consider a multi-access scheme where multi-users with single-antenna transmit data to a multiple-antenna base station through the same resource block. By taking advantage of combining diversity paths with the proposed joint maximum-likelihood detector (JMLD), a closed form expression for the upper bound of bit error rate (BER) is obtained. Despite the number of users or the order of modulation, the analytical results endorsed via computer simulations reveal the ability of the MRC-JMLD detector to discard the error floor completely. Moreover, the simulation results show that the MRC-JMLD surpasses its counterparts significantly and ensures a full diversity order.