High-Speed Visible Light Indoor Networks Based on Optical Orthogonal Codes and Combinatorial Designs

TL;DR

This paper proposes two innovative optical multiple access techniques for indoor visible light networks using LED illumination, optical orthogonal codes, and combinatorial designs to enable multiuser access and control power levels.

Contribution

It introduces two novel multilevel signaling methods based on OOC and BIBD for VLC, enhancing multiuser access and power control in indoor lighting networks.

Findings

The first method offers larger Hamming distances between user symbols.

The second method achieves higher bit-rates in bandwidth-limited LED systems.

Both techniques enable simultaneous multiuser access with power control.

Abstract

Interconnecting devices in an indoor environment using the illumination system and white light emitting diodes (LED) requires adaptive networking techniques that can provide network access for multiple users. Two techniques based on multilevel signaling and optical orthogonal codes (OOC) are explored in this paper in order to provide simultaneous multiple access in an indoor multiuser network. Balanced incomplete block designs (BIBD) are used to construct multilevel symbols for M-ary signaling. Using these multilevel symbols we are able to control the optical peak to average power ratio (PAPR) in the system, and hereby control the dimming level. In the first technique, the M-ary data of each user is first encoded using the OOC codeword that is assigned to that user, and then it is fed into a BIBD encoder to generate a multilevel signal. The second multiple access method uses sub-sets of a BIBD code to apply multilevel expurgated pulse-position modulation (MEPPM) to the data of each user. While the first approach has a larger Hamming distance between the symbols of each user, the latter can provide higher bit-rates for users in VLC systems with bandwidth-limited LEDs.