Design and Implementation of a Multi-Colour Visible Light Communication System Based on a Light-to-Frequency Receiver

Abstract

Colour-shift keying (CSK) is a visible light communication (VLC) modulation scheme used in the existing IEEE 802.15.7 standard. In CSK, information is transmitted by changing the light intensities of the RGB LEDs. In this work, a low-complexity VLC system is proposed using CSK modulation and a novel receiver based on a light-to-frequency (LTF) converter. At the receiver, CSK symbols are interpreted and decoded in terms of frequencies, which are processed by a counter module of a generic microcontroller, thus avoiding the use of analog-to-digital converters (ADCs), which results in a low-cost VLC system. The main contributions of this work are summarized in the following key points: (1) A low-complexity receiver for CSK modulation is introduced; (2) A particle swarm optimization (PSO) algorithm for CSK constellation design is suggested considering the restrictions of the LTF based receiver; (3) Experimental and theoretical validation is perfomed for the proposed multi-colour VLC system. The results show that this system can provide a transmission speed of 100 kbps using a 4-CSK-LTF constellation for a symbol error rate (SER) of 10 − 4 and a signal to noise ratio (SNR) around 35 dB. These results suggest that the analysed system could find applications on those scenarios where low transmission speeds and ease of deployment are the goals.

An Indoor Visible Light Positioning System for Multi-Cell Networks

“…The optical receiver is based on the Thorlabs' PDA36A light detector model, where we exploit the sensitivity response of the photodiode for estimating the RGB light power as a function of the photocurrent. This process is similar to those utilized in [27,31]. Then, the PDA36A converts the photocurrent into a voltage signal with a transimpedance amplifier.…”

“…In every cell k of the network, each RGB LED will transmit a VLC signal with a unique identifier through a specific carrier frequency. Our approach allows for exploring the CIE 1931 RGB color space [32] to enable symbol mapping and constellation design in the same fashion as in color-shift keying (CSK) schemes [27]. Figure 4 illustrates an example of the color space constellation diagram for the 7-CSK modulation scheme with a triangular region denoted by the "RGB" vertices.…”

“…On the other hand, there are few existing works on multi-color transmission channels for VLP systems. Trichromatic WLEDs based on red-green-blue (RGB) LEDs have become promising in the VLP system because they offer the possibility to perform wavelength division multiplexing (WDM) and color shift keying (CSK) [26,27]. In [26], Vieira et al proposed a VLP based on RGB LEDs with WDM, a double PIN photodetector with two UV light biased gates, the RSS technique, and the multilateration method.…”

“…Each cell consists of three RGB LED transmitters and one photodiode detector located at the mobile user as the optical receiver. This method resembles the VLC system using color-shift keying (CSK) modulation, as proposed in the standard IEEE 802.15.7 [27][28][29][30]. Some important features of the CSK scheme are adapted to the localization problem in the VLP system of this work.…”

Doubly Orthogonal Wavelet Packets for Multi-Users Indoor Visible Light Communication Systems

“…">IntroductionWith unprecedented demand for high-speed multi-media mobile services, optimization of wireless communication systems has become critical. Due to the limited range of frequencies, radio-frequency (RF) technology is unable to fulfill the needs for the current demands of mobile users [1]. As we are advancing towards 5G, the necessity for the evolution in broadband communication technologies has grown to its peak.…”