Breaking the limitations of visible light communication through its side channel

Abstract

Visible Light Communication (VLC) is a promising technology for future wireless communications. By modulating the visible light - -that has about 10,000x larger frequency band than that of radios - -to transmit data, VLC has the potential to provide ultra-high-speed wireless connectivities. However, it also has limitations such as i) surrounding objects can easily block VLC links, and ii) intense ambient light can saturate the photodiodes of VLC receivers. In this work, from a different angle compared with state-of-the-art solutions, we utilize the side channel of VLC - -a Radio Frequency (RF) channel created unintentionally during the transmission process of VLC - -to break the above-mentioned VLC limitations. The key enabler is that the side RF channel also contains the data information transmitted in the VLC link. When the VLC link is blocked or saturated, we can utilize the side channel, capable of penetrating through blockages and not affected by ambient light, to assist VLC transmissions. Thus a user service relying on VLC transmissions will not be interrupted. Besides the simple Single-Input Single-Output (SISO) case, we consider challenging scenarios where multiple VLC chains are synchronized to form Multiple-Input Multiple/Single-Output (MIMO/MISO) transmission strategies. To make our system practical, we address several challenges spanning from hardware to software. Compared to state-of-the-art design, we reduce the size of the receiving coil by nearly 90%. Experimental evaluations show that our system can decode overlapped RF signals created by a 3X3 MIMO VLC network five meters away, with various blockages in between. Our system also works under intense ambient light conditions (> 100,000 lux).