36 / 2021-06-22 21:33:50

A General Model for Dimmable Optical Camera Communication

Special Session > SS8 - Machine Learning for Industrial Internet of Things (IIoT)

Supporting dimming control is very improtant in optical camera communication (OCC), because the LED transmitter in an OCC system is envisoned for both communication and illumination. In particular, there is a specific chapter to highlight dimming techniques for OCC in recent EEE std 802.15.7-2018. To this end,  a mathematical model for building the relationship between the illumination and the grayscale is proposed in this paper. Basically, we choose the Pulse Width Modulation (PWM) for dimming control thanks to its simplicity and practicability, and first investigate the relationship between the duty cycle of PWM and the LED luminous intensity  based on the spatial distribution of the LED radiation. We then analyze the received signal strength after light propagation via the Lambert's law, and finally derivate the grayscale relationship by combining theoretical analysis for the camera receiver and field measurements. With extensive evaluations, the similarity coefficient between the calculated results and measured value reaches 95%, strongly confirming the effectiveness of the proposed model.