Experimental Assessment of the Accuracy of Modulated and Unmodulated Visible Light Positioning

Abstract

To feature a Light-Emitting Diode (LED) illumination infrastructure as a received signal strength (RSS)-based Visible Light Positioning (VLP) system's beacons, each LED's driver currently needs to be retrofitted. As a consequence of the intensity modulation (IM) retrofit, the LEDs' average radiant flux decreases. To remain adherent to the required illuminance levels, additional LED sources are required, which significantly raises the roll-out cost. The goal of unmodulated VLP (uVLP) is to refrain from modulating the LEDs by exploiting an inherent characteristic of the LEDs' light signals, namely the characteristic frequency (CF). This paper shows the aptitude of using the spectral magnitude at the CF to infer accurate positioning in photodiode (PD)-based RSS uVLP. Compared to regular VLP, uVLP displays a limited increase in median and 90th percentile root-mean-square error of 3.52 cm (8.72 cm vs. 5.20 cm) and 7.54 cm (16.96 cm vs. 9.42 cm) respectively, during trilateration in a 4 m by 4 m lab setup. This shows uVLP's potential as an indoor localisation system.