Occupancy Estimation Through Visible Light Sensing (VLS)

Abstract

Visible light is everywhere around in our daily life. The part of the electromagnetic spectrum that is visible to the human eye is called visible light; it is in the range between 350-750 nm, which is roughly between 400-750 THz in terms of frequency. Visible light sensing and communication (VLS and VLC) are considered two of the most emerging fields in sensing and wireless communication areas, where light emitting diodes (LEDs) are used as the transmission unit (Tx). LEDs have a number of advantages, some of which are extended life expectancy, illumination, lower energy dissipation, and eco-friendly. As a result, visible light can be used in several sensing applications in our life such as occupancy estimation.

In this thesis, a new occupancy estimation method based on VLS is presented. A visible light source (e.g., LED) is utilized as the transmitter and a photo-detector (PD) used as a receiver, forming a visible light sensing system. Depending on the number of people in the room crossing the line-of-sight LOS (between the light source and PD), the received power at the receiver change. Consequently, probability density function (PDF) and cumulative distribution function (CDF) of the received power at the receiver change. First, a theoretical analysis of the received power is developed to incorporate the impact of room occupancy on the PDF and CDF of the received power. Second, these received power PDF and CDF expressions are compared with simulation results. Both results are in perfect agreement that verifies the theoretical analysis. In addition, Kullback-Leibler divergence (KL-divergence) method to analyze measurement data to detect the number of occupants in an environment. In this method, the stored PDF of the received power in the database is compared with the measured received power PDF, which reveals the estimated room occupancy. It was shown how a slight variation in room occupancy can dramatically alter the statistics the received power. Theoretical analysis and simulations are performed. In addition, we have conducted experiments in the Wireless Communication and Sensing Research Lab (WCSRL) located in Engineering South (ES) 408 at Oklahoma State University. As a future work, we are planning to study the impact of scattering on estimation accuracy. Multiple LEDs and PDs (i.e., multiple transmitters and receivers) can also be considered in future tests. Developing a complete system that can control and regulate buildings HVAC (heating, ventilation, and air conditioning) and lighting to improve sustainability and energy efficiency will be one of our promising research direction in the future.