About Digital Communication Methods for Visible Light Communication

TL;DR

This paper proposes two methods for adjusting threshold values in visible light communication systems using pulse wave modulation, enhancing signal detection accuracy through slot counting and signal level measurement, validated by experiments.

Contribution

Introduces two novel threshold adjustment techniques for VLC using pulse position modulation, improving detection reliability without complex amplification.

Findings

Threshold adjustment via slot counting improves signal detection accuracy.

Average signal level measurement aids in optimal threshold setting.

Experimental results confirm the effectiveness of the proposed methods.

Abstract

The visible light communication (VLC) by LED is one of the important communication methods because LED can work as high speed and VLC sends the information by high flushing LED. We use the pulse wave modulation for the VLC with LED because LED can be controlled easily by the microcontroller, which has the digital output pins. At the pulse wave modulation, deciding the high and low voltage by the middle voltage when the receiving signal level is amplified is equal to deciding it by the threshold voltage without amplification. In this paper, we proposed two methods that adjust the threshold value using counting the slot number and measuring the signal level. The number of signal slots is constant per one symbol when we use Pulse Position Modulation (PPM). If the number of received signal slots per one symbol time is less than the theoretical value, that means the threshold value is higher than the optimal value. If it is more than the theoretical value, that means the threshold value is lower. So, we can adjust the threshold value using the number of received signal slots. At the second proposed method, the average received signal level is not equal to the signal level because there is a ratio between the number of high slots and low slots. So, we can calculate the threshold value from the average received signal level and the slot ratio. We show these performances as real experiments.