Indoor positioning systems based on visible light communication (VLC) using white light-emitting diodes (WLEDs) have been widely studied in the literature. In this paper, we present an indoor visible-light positioning (VLP) system based on red–green–blue (RGB) LEDs and a frequency division multiplexing (FDM) scheme. This system combines the functions of an FDM scheme at the transmitters (RGB LEDs) and a received signal strength (RSS) technique to estimate the receiver position. The contribution of this work is two-fold. First, a new VLP system with RGB LEDs is proposed for a multi-cell network. Here, the RGB LEDs allow the exploitation of the chromatic space to transmit the VLP information. In addition, the VLC receiver leverages the responsivity of a single photodiode for estimating the FDM signals in RGB lighting channels. A second contribution is the derivation of an expression to calculate the optical power received by the photodiode for each incident RGB light. To this end, we consider a VLC channel model that includes both line-of-sight (LOS) and non-line-of-sight (NLOS) components. The fast Fourier transform (FFT) estimates the powers and frequencies of the received FDM signal. The receiver uses these optical signal powers in the RSS-based localization application to calculate the Euclidean distances and the frequencies for the RGB LED position. Subsequently, the receiver’s location is estimated using the Euclidean distances and RGB LED positions via a trilateration algorithm. Finally, Monte Carlo simulations are performed to evaluate the error performance of the proposed VLP system in a multi-cell scenario. The results show a high positioning accuracy performance for different color points. The average positioning error for all chromatic points was less than 2.2 cm. These results suggest that the analyzed VLP system could be used in application scenarios where white light balance or luminaire color planning are also the goals.

PIN (positive intrinsic negative) photodiodes and analog-to-digital converters (ADC) are commonly used on visible light communication (VLC) receivers in order to retrieve the data on detected signals. In this paper, a visible light communication receiver based on a light to frequency converter (LTF) is proposed. We characterized the LTF and derived an equation for signal-to-noise ratio (SNR) estimation in terms of its input optical power, and the frequency of the output periodic signal. The experiments show that the periodic signal of the LTF converter has a maximum output frequency of 600 kHz at a distance of 6.2 cm. In this setup, measured SNR reached 18.75 dB, while the lowest obtained SNR with 1.1 m length was roughly −35.1 dB. The results obtained suggest that a bit rate of 150 kbps can be achieved with an on-off keying (OOK) modulation format. We analyzed the results and discuss the advantages and limitations of the LTF converter for optical wireless communication purposes.

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.

Visible light communication (VLC) technology allows data to be transmitted using the optical power emitted by light-emitting diodes (LEDs). The optical receiver usually employs light sensors such as photodiodes, image sensors, photoresistors or solar panel. In the last decades, VLC technology has explored the use of solar panels as data receivers, since they offer the service of power generation, in addition to, a larger surface area to capture the light beam. In this paper, we present the performance evaluation of a VLC system based on solar panel and automatic gain control (AGC) with application in access control systems. Three experiments are proposed to evaluate the uses of the solar panel as information receiver in VLC systems: bandwidth (BW) estimation, VLC system performance and panel viewing angle variation. As a result, we were able to determine a BW of 10 kHz and 190 kHz considering the panel without AGC and with AGC. In the context of digital modulation, a RS-232 module of an Arduino UNO development system was used in order to execute the technique of intensity modulation and direct detection IM/DD. The NRZ line code of the serial interface was used to modulate the electric current of the LED with a maximum symbol rate of 38400 baud with a data effectiveness of 91%. Furthermore, we found that AGC improves the dynamic range of the solar panel's viewing angle and the performance of the VLC system.

A visible light positioning (VLP) system for multi‐cell networks based on multi‐colour LED that combines frequency division multiplexing with the received signal strength and a trilateration method is proposed. First, it employs experimental measurements to model the designed visible light communication (VLC) system under the characteristics of the target scenario. Second, it introduces a low‐cost VLC transmitter that exploits the chromatic space to transmit the VLP information. Third, it characterizes the VLC transmitter and proposes a linearization for electro‐optical responses of RGB LED. An RGB digital colour sensor and simple method calibrate the chromatic emission. The experimental results show that the proposed VLP multi‐cell architecture achieves a positioning accuracy lower than .

Visible light communication (VLC) is an emerging technology that uses white light-emitting diodes (LEDs) to transmit information and provide illumination simultaneously. Recently, solar panels have been proposed as optical detectors at the receiver to retrieve data from light signals. However, very few studies have addressed the behavior of the solar panel bandwidth at different wavelengths. In this paper, we propose the design of a low-complexity VLC system with a red-green-blue (RGB) LED transmitter and a solar panel receiver whose bandwidth is modified using a parallel load resistor. We define a set of experiments to validate the performance of the VLC system using an RGB LED source and a solar panel as the optical receiver. The VLC systems performance is evaluated across various baud rates (4800, 9600, 19200, 38400, 57600, and 115200 bits/s) at a free space transmission distance of less than 105 cm. Our measurements indicate that the solar panels highest bandwidth is achieved with the red channel, yielding a maximum data rate of 57600 bits/s at a bit error rate (BER) of 5 103. These results are analyzed and discussed to highlight the benefits and limitations of using solar panels for VLC purposes.