Abstract
Wireless technologies that are based on radio frequencies are currently widely used, with numerous applications around the world. However, they pose some disadvantages to human health. High frequencies can have potentially harmful effects on children, hospital patients, and even healthy people if the signal power exceeds the permitted standard. Conversely, the use of visible light for data transmission is a trend that presents new options, including optical wireless communication, optical camera communication, and visible light communication. This paper proposes a modulation scheme based on on-off keying in the time domain, which is applied to a monitoring system using optical camera communication. This scheme has various compatible supports for the global-shutter camera and rolling-shutter camera, which are popular commercially available cameras. Furthermore, this scheme facilitates a low-cost monitoring system. By using small light-emitting diodes (LEDs) and controlling the exposure time in a single camera, the camera, as a receiver, can simultaneously detect signals from up to 10 sensor devices in different positions at a maximum distance of up to 50 m, with a low error rate.
Highlights
The Internet of Things (IoT) is widely applied for various purposes in different areas such as system-monitoring systems for smart factories, smart agriculture, smart homes, and healthcare [1].The purpose of IoT is to connect physical devices with the virtual world, using internet protocol as the intermediary to communicate data [2]
Current techniques that involve IoT are mostly based on radio frequency (RF) technology, such as ZigBee, Bluetooth, and WiFi
We discuss a monitoring system that uses the optical camera communication (OCC) technique, which is a combination of RoI signaling waveforms and Multiple-input multiple-output (MIMO)-on-off keying (OOK) modulation
Summary
The Internet of Things (IoT) is widely applied for various purposes in different areas such as system-monitoring systems for smart factories, smart agriculture, smart homes, and healthcare [1]. Because of improvements in manufacturing technology, LEDs have the potential to become next-generation lighting sources, owing to their advantages in terms of long life, power consumption, and good visibility Their ability to switch on/off at a fast rate [7,8] facilitates high-rate transmission in OWC/OOC and VLC systems. Based on the rolling-shutter effect, in [21] the authors present camera on-off keying (OOK) modulation with a high data rate, but the rolling-shutter method has some drawbacks, including the limited transmission distance and high error rate. We discuss a monitoring system that uses the OCC technique, which is a combination of RoI signaling waveforms and MIMO-OOK modulation.
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