Electronic Technology and Reliability Department, Politehnica University of Bucharest, 061071 Bucharest, Romania.
Telecommunications Department, Politehnica University of Bucharest, 061071 Bucharest, Romania.
Sensors (Basel). 2022 Aug 9;22(16):5938. doi: 10.3390/s22165938.
Light emitting diodes (LED) are becoming the dominant lighting elements due to their efficiency. Optical camera communications (OCC), the branch of visible light communications (VLC) that uses video cameras as receivers, is a suitable candidate in facilitating the development of new communication solutions for the broader public because video cameras are available on almost any smartphone nowadays. Unfortunately, most OCC systems that have been proposed until now require either expensive and specialized high-frame-rate cameras as receivers, which are unavailable on smartphones, or they rely on the rolling shutter effect, being sensitive to camera movement and pointing direction, they produce light flicker when low-frame-rate cameras are used, or they must discern between more than two light intensity values, affecting the robustness of the decoding process. This paper presents in detail the design of an OCC system that overcomes these limitations, being designed for receivers capturing 120 frames per second and being easily adaptable for any other frame rate. The system does not rely on the rolling shutter effect, thus making it insensitive to camera movement during frame acquisition and less demanding about camera resolution. It can work with reflected light, requiring neither a direct line of sight to the light source nor high resolution image sensors. The proposed communication is invariant to the moment when the transmitter and the receiver are started as the communication is self-synchronized, without any other exchange of information between the transmitter and the receiver, without producing light flicker, and requires only two levels of brightness to be detected (light on and light off). The proposed system overcomes the challenge of not producing light flicker even when it is adapted to work with very low-frame-rate receivers. This paper presents the statistical analysis of the communication performance and discusses its implementation in an indoor localization system.
发光二极管（LED）因其效率而成为主要的照明元件。光学相机通信（OCC）是可见光通信（VLC）的一个分支，它使用摄像机作为接收器，是促进新的更广泛的公共通信解决方案发展的合适候选者，因为现在几乎任何智能手机都配备了摄像机。不幸的是，迄今为止提出的大多数 OCC 系统要么需要昂贵且专用的高帧率相机作为接收器，而智能手机上没有这种相机，要么依赖滚动快门效应，对相机的移动和指向方向敏感，当使用低帧率相机时会产生光闪烁，或者必须区分两个以上的光强度值，影响解码过程的鲁棒性。本文详细介绍了一种克服这些限制的 OCC 系统的设计，该系统专为每秒捕获 120 帧的接收器设计，并且易于适应任何其他帧率。该系统不依赖于滚动快门效应，因此在帧采集过程中对相机的移动不敏感，对相机分辨率的要求也不高。它可以使用反射光工作，既不需要与光源的直接视线，也不需要高分辨率的图像传感器。所提出的通信不受发射器和接收器启动时刻的影响，因为通信是自同步的，发射器和接收器之间不需要任何其他信息交换，不会产生光闪烁，并且只需要检测两个亮度级别（亮和灭）。即使该系统适应与非常低帧率的接收器一起工作，该系统也克服了不会产生光闪烁的挑战。本文提出了通信性能的统计分析，并讨论了其在室内定位系统中的实现。
