Performance Enhancement of Rolling Shutter Based Visible Light Communication via Selective Reception Using Dual Cameras

This study focuses on visible light communication (VLC) using dual rolling shutter (RS) cameras. In VLC using an RS camera as a receiver, called rolling shutter based VLC (RS-VLC), the transmitted signal is projected as stripes on the image when the information is transmitted by an LED at a modulation speed higher than the frame rate. Therefore, the RS-VLC can improve the data rate. However, non-uniform luminance distribution on the image causes communication errors. Because LED light sources emit light radially, the luminance between the center and the edge of the LED in the captured image differs. Specifically, the received signal intensity is strong and good channel conditions can be obtained in the center of the LED, whereas the received signal intensity is weak at the edges, making it difficult to recognize changes in signal amplitude and prone to communication errors. To solve this problem, this study aims to enhance the communication error using dual camera images with misaligned LED positions and selecting the one with the better channel condition from the two received signals.

I. Introduction

Visible light communication (VLC) is a wireless communication technique that transmits data by modulating the luminance or color of LEDs without perception to the human eyes [1], [2]. LEDs can not only be used for lighting and display, but also for data transmission such as providing wireless LAN access from room lamps [3], multilingual guidance from digital signage [4], and driving assist information from traffic lights [5]. Figure 1 illustrates an example of VLC services. Because the transmission signal is visible, cameras can be used as reception devices. This type of VLC is referred to as an image sensor based VLC (IS-VLC) [6]. Therefore, IS-VLC could be used as a communication technology suitable for the Internet of Things (IoT) [7].