Bidirectional Visible Light Communication for Remote Indoor Air Quality Monitoring

Abstract

In this thesis, the author presents a design of visible light communication system for indoor positioning and remote air quality monitoring. The proposed system has two main components: base station and sensor module. For positioning, a novel high-precision positioning algorithm utilized visible light communication with only simple one receiver is proposed. Derived from the optical propagation model, an algorithm is demonstrated based on the relationship between perceived power, noise, and position. In addition, the proposed algorithm takes advance of the voltage difference from multi-level modulation as the input to minimize the noise’s negative impact. Furthermore, the minimum mean squares error algorithm and extended Kalman filter are adapted to improve the optical modeling accuracy and achieve high performance. For second purpose, indoor air quality, temperature, and relative humidity broadly refer to the environmental characteristics inside buildings that may affect a thermal comfort, healthy life, or labor productivity. Thus, monitoring these parameters is essential in order to understand and prevent air pollution, assess emission sources, and preserve health. Since there are several publications which support the existence of complex biological and neurological effects of RF communication even in weak non-thermal electromagnetic fields, the visible light communication system is applied as a wireless indoor environment monitoring system with EMI-free. An average-voltage tracking algorithm was adapted to allow the LED illumination to utilize for dual purposes as a lighting system and a communications medium. After collecting the sensing data from electrochemical sensors, each sensor modules wirelessly transmits these data to the base station via VLC with the distance of 6 m and error-free. Finally, the measured data are monitored by using a user interface in real-time.