Generalized Spatial Pulse Position Modulation for Optical Wireless Communications

In this paper, we investigate the performance of a spatial modulation scheme that combines the energy efficiency of pulse position modulation (PPM) with the spectral efficiency of generalized space shift keying (GSSK) for optical wireless communication system. The combined scheme is called generalized spatial pulse position modulation (GSPPM). We present the error performance analysis and validate the results through simulation. Error performance results show that the upper bound derived in the theoretical analysis is tight for all cases when the symbol error rate is below 0.1. The influence of parameters such as channel path gain and number of PPM slots on GSPPM's performance is illustrated. GSPPM is compared with some of the existing spatial modulation techniques, and results show that GSPPM provides an attractive trade-off between energy and spectral efficiency.

I. Introduction

In today's era of ubiquitous communication, optical wireless communication (OWC) employs the vast and unlicensed infrared and visible light spectrum to provide relief to the congested radio frequency (RF) spectrum without affecting the emitted light quality [1], [2]. As in RF communications, parallel transmission can be achieved in OWC using multiple-input multiple-output (MIMO) techniques. In visible light communication (VLC), the multiple light emitting diodes (LEDs) which are required to provide sufficient illumination within a space are potential transmitters that can enable optical MIMO. In this regard, several low bandwidth channels with high signal-to-noise ratio can be combined in optical MIMO to achieve high speed and spectral efficient VLC [3].