Characterization of Light-To-Frequency Converter for Visible Light Communication Systems

Abstract

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.

Visible Light Communication and Positioning: Present and Future

“…For visible light communication, the published works focus on the devices, the physical-layer techniques, and system work aspects. In [20], the light-to-frequency converter for VLC is characterized. In [21,22], the physical-layer non-orthogonal multiple access and multi-color VLC, respectively, are addressed.…”

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

“…The dark frequency f D is generated by the LTF when irradiance is zero (E λ = 0) and it is also the result of leakage currents produced by the semiconductor material and affected by the temperature of the system [22]. The optical conversion gain R is given in (Hz/(µW/cm 2 )) and irradiance E λ = P in Ar is generated by the incident optical power P in and the photosensitive area of the photodiode Ar [19,23,24]. The irradiance units are given in µW/cm 2 .…”

“…The LTF was configured to operate at the maximum output frequency scale and only the channel with no filter was activated [30] to detect incident light optical power. In [19], an example illustrating the response of the LTF to an incident optical signal generated by a white light LED was shown. In order to measure the frequency generated by the LTF, at least half a period in high state is necessary to calculate its approximate value using a timer (depending on the resolution of the timer).…”

“…This work was evaluated by means of Monte Carlo simulation, and it was shown that the process to implement the receiver was decreased by 66% compared to the one described in the standard IEEE 802.15.7 [16].Although CSK modulation is functional for high speed rates, in some scenarios with lower transmission speeds requirements, using an architecture based on ADC results in an oversized solution because they are more complex and expensive, and there are simpler solutions which are worth to implement. In this study, a simple and cost-effective VLC-CSK system with off-the-shelf components is proposed.The contribution of this work can be listed as it follows: (1) It proposes the study, analysis, and evaluation of a low-complexity VLC system by using CSK and a Light-To-Frequency (LTF) converter as a receiver [19]. (2) It proposes a particle swarm optimization (PSO) algorithm to design the M-CSK-LTF constellations that considers the euclidean distance between frequencies generated in the LTF and the restrictions of the transmitter and the receiver.…”

“…The contribution of this work can be listed as it follows: (1) It proposes the study, analysis, and evaluation of a low-complexity VLC system by using CSK and a Light-To-Frequency (LTF) converter as a receiver [19]. (2) It proposes a particle swarm optimization (PSO) algorithm to design the M-CSK-LTF constellations that considers the euclidean distance between frequencies generated in the LTF and the restrictions of the transmitter and the receiver.…”