# On the Achievable Spectral Efficiency of Spatial Modulation Aided Downlink Non-Orthogonal Multiple Access

## TL;DR

This paper introduces a novel SM-NOMA system that enhances spectral efficiency, providing theoretical bounds and asymptotic analysis, supported by simulation results to validate its performance improvements.

## Contribution

It proposes a new SM-NOMA system with a mutual information-based spectral efficiency analysis, including a lower bound and asymptotic properties, advancing understanding of its performance.

## Key findings

- Derived a lower bound for spectral efficiency of SM-NOMA
- Analyzed asymptotic behavior in low and high SNR regimes
- Validated performance through simulation results

## Abstract

In this paper, a novel spatial modulation aided non-orthogonal multiple access (SM-NOMA) system is proposed. We use mutual information (MI) to characterize the achievable spectral efficiency (SE) of the proposed SM-NOMA system. Due to the finite-alphabet space-domain inputs employed by SM, the expression of the corresponding MI lacks a closed-form formulation. Hence, a lower bound is proposed to quantify the MI of the SM-NOMA system. Furthermore, its asymptotic property is also theoretically investigated in both low and high signal-to-noise ratio (SNR) regions. The SE performance and its analysis of our proposed SM-NOMA system are confirmed by simulation results.