Enhancing the performance of active and passive systems in visible light communication

Abstract

Communication technology has continually adapted to new challenges. RF communication, with its established infrastructure, supports technologies like Bluetooth, Wi-Fi, and LoRa. However, the rise of IoT devices has lead to problems in traditional RF communication such as increasing spectrum congestion and interference. In this context, Visible Light Communication (VLC) emerges as a promising alternative to traditional RF systems. VLC uses the unlicensed light spectrum, modulating light intensity at speeds invisible to the human eye to transmit data, which is then received and decoded by photodetectors. While RF communication can also utilize unlicensed bands, VLC operates in an entirely separate region that experiences fewer regulatory constraints and interference issues compared to the crowded RF spectrum.
VLC systems can be classified based on their light source into active VLC and passive VLC. Active VLC systems use LEDs to transmit data through rapid light modulation controlled by circuitry, enabling fast communication. A key advantage of active VLC is its dual-purpose function, serving both illumination and communication, thereby maximizing resource use. However, the illumination of LEDs is often obstructed by walls or furniture affecting the coverage of active VLC systems. On the other hand, passive VLC systems use sunlight for data transmission, offering a pervasive and energy-efficient communication method, as sunlight provides a continuous source of illumination without additional energy costs. Passive VLC systems use external modulating surfaces to modulate ambient light properties to transmit data but face challenges due to the variable nature of ambient light, leading to links with lower performance compared to active VLC.
In this thesis, we address the obstruction challenges of active VLC and the low performance of passive VLC through a comprehensive approach that combines novel hardware designs and strategic system integration.