Application of Expurgated PPM to Indoor Visible Light Communications - Part I: Single-User Systems

TL;DR

This paper introduces expurgated pulse-position modulation (EPPM) and interleaving techniques to enhance indoor visible light communication systems, addressing bandwidth limitations and inter-symbol interference for improved performance.

Contribution

It proposes EPPM with a correlation decoder and interleaving methods to reduce ISI, and introduces overlapped EPPM pulses for higher transmission rates in bandwidth-limited LEDs.

Findings

EPPM with correlation decoding is optimal for indoor VLC.

Interleaving significantly reduces error probability in dispersive channels.

Overlapped EPPM increases transmission rate with bandwidth-limited LEDs.

Abstract

Visible light communications (VLC) in indoor environments suffer from the limited bandwidth of LEDs as well as from the inter-symbol interference (ISI) imposed by multipath. In this work, transmission schemes to improve the performance of indoor optical wireless communication (OWC) systems are introduced. Expurgated pulse-position modulation (EPPM) is proposed for this application since it can provide a wide range of peak to average power ratios (PAPR) needed for dimming of the indoor illumination. A correlation decoder used at the receiver is shown to be optimal for indoor VLC systems, which are shot noise and background-light limited. Interleaving applied on EPPM in order to decrease the ISI effect in dispersive VLC channels can significantly decrease the error probability. The proposed interleaving technique makes EPPM a better modulation option compared to PPM for VLC systems or any other dispersive OWC system. An overlapped EPPM pulse technique is proposed to increase the transmission rate when bandwidth-limited white LEDs are used as sources.