Abstract
Abstract The synthesis of visible light communication (VLC) and lighting state control necessitates data-light modulation that can accommodate intensity control. A number of techniques that enable both optical wireless data transmission and intensity control of light-emitting diodes (LEDs) have been proposed as a response to this need. Relevant schemes leverage amplitude modulation (AM)/continuous current reduction (CCR) and/or pulse-width modulation (PWM) for dimming capability. Two-level schemes related to PWM, such as on-off keying with compensation time (OOK + CT), variable pulse position modulation (VPPM), and multiple pulse position modulation (MPPM), are most commonly investigated. In this paper, we survey and compare OOK + CT, VPPM and MPPM. Moreover, we propose a novel approach towards dimming and data transmission through the variation of codeword weights in overlapping pulse-position modulation (OPPM). The proposed approach has comparatively high spectral efficiency. Using realistic constraints of a practical VLC system, analysis reveals that OPPM can increase data rates by more than 20Mbps over expected performance of related, two-level schemes, when using LEDs suitable for lighting that have relatively low modulation bandwidths.
Highlights
Future lighting systems will be expected to be optimized to meet strict energy efficiency and light rendering quality goals
We propose a novel operation through the variation of codeword weights of overlapping pulse position modulation (OPPM) to achieve dynamic dimming and data transmission at higher data rates compared to well-known common two-level modulation and dimming schemes
The analysis aims at incorporating realistic constraints of a practical Visible light communications (VLC) system
Summary
Future lighting systems will be expected to be optimized to meet strict energy efficiency and light rendering quality goals. They will increasingly have new functions providing adaptability, self-provisioning capabilities, and intelligence to react to human needs. These functions will be provided by embedded control and communications. Visible light communications (VLC) seeks to provide high-speed optical communications as an additional function, delivering additional capacity in indoor wireless networks. These functions leverage one another (embedded control, communications, and VLC), the common lighting task of intensity control (dimming) is in conflict with achieving optical data modulation. VLC systems, which stream data wirelessly by high frequency modulation of LED drive currents, must incorporate new modulation schemes for compatibility with lighting control [1]
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