Abstract
This technical paper presents an optical camera communication system by using data as input collected from a sensor that continuously garners humidity and temperature information from the environment. A small light-emitting diode (LED) and an LED array are used as a transmitter and a low-speed rolling-shutter camera as a receiver. A modulation scheme standardized in IEEE 802.15.7, referred to as variable pulse-width modulation, is used to encode the data bits. The proposed scheme is flicker-free in different frequencies and applicable in both static and mobile scenarios. A neural network is designed for LED detection and improving the bit-error-rate in mobile scenarios. A new method based on the region-wise comparison and an existing method is used to remove the interference and noise generated from the neighboring light sources, respectively. The decoding procedure is performed and analyzed in Python 3.7. A data rate of 1.02 kbps is achieved using the single LED, which is further augmented to 64 kbps by using an $8\times 8$ LED dot matrix.
Highlights
Optical camera communications (OCC) operates in infrared or visible bands and exploit an image sensor as the receiver and light-emitting diodes (LEDs) as the transmitter
We have developed a function in Python to find the areas in which the source LED and the interfering light sources appear
The BER is measured in moving scenarios, and how it is improved with the employment of the neural network (NN) is illustrated
Summary
Optical camera communications (OCC) operates in infrared or visible bands and exploit an image sensor as the receiver and light-emitting diodes (LEDs) as the transmitter. The most significant things to be considered while using OCC are the channel characteristics, synchronization between the camera and LED, data transmission pattern, motion capture, modulation, and proper applications. A smartphone camera-based OCC system is implemented in [5] that achieve a communication distance of 7.5 m with a large LED (several cm in diameter). Most OCC implementations in the literature used low frequencies, and mitigated the flickering problem using under-sampling [7] and multiple-level modulation [8], [9] techniques. The BER will be substantial in mobile conditions Considering these limitations, in this paper, we propose an OCC system using an LED (3 mm outside diameter) and an LED array (comprising 8 × 8 dot matrix) as transmitter and a low-frame rate camera as receiver.
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