New Signal Designs for Enhanced Spatial Modulation

TL;DR

This paper introduces three innovative signal designs for Enhanced Spatial Modulation in MIMO systems, achieving higher SNR and spectral efficiency through new constellation interpolation techniques.

Contribution

The paper presents three novel ESM signal designs for multi-stream SM that improve SNR gains and extend applicability to systems with more antennas.

Findings

Significant SNR gains demonstrated through analysis and simulation.

New constellation interpolation methods enhance spectral efficiency.

Designs applicable to systems with more than four antennas.

Abstract

In this paper, we present three new signal designs for Enhanced Spatial Modulation (ESM), which was recently introduced by the present authors. The basic idea of ESM is to convey information bits not only by the index(es) of the active transmit antenna(s) as in conventional Spatial Modulation (SM), but also by the types of the signal constellations used. The original ESM schemes were designed with reference to single-stream SM and involved one or more secondary modulations in addition to the primary modulation. Compared to single-stream SM, they provided either higher throughput or improved signal-to-noise ratio (SNR). In the present paper, we focus on multi-stream SM (MSM) and present three new ESM designs leading to increasing SNR gains when they are operated at the same spectral efficiency. The secondary signal constellations used in the first two designs are based on a single geometric interpolation step in the signal constellation plane, while the third design also makes use of additional constellations derived through a second interpolation step. The new ESM signal designs are described for MIMO systems with four transmit antennas two of which are active, but we also briefly present extensions to higher numbers of antennas. Theoretical analysis and simulation results indicate that the proposed designs provide a significant SNR gain over MSM.