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VL-Watchdog: Visible Light Spoofing Detection With Redundant Orthogonal Coding

With the rapid increase of smart devices in the Internet of Things, more and more visible light (VL) systems, e.g., VL communication (VLC) and VL sensing (VLS), are developed on the existing light fixtures to offload the current crowded spectrum, how to guarantee the authenticity of the VL signal in these systems becomes an urgent problem. This is because almost all of today’s light fixtures are unprotected and can be openly accessed by almost anyone and, hence, are susceptible to spoofing attacks. As such, ensuring received VL signals are coming from the authentic transmitters (LEDs), rather than from a spoofer, is the key in ensuring the quality and correctness of the VL communication and sensing outcomes. Existing authentication methods are either not directly applicable to signal-level authentication, or have poor scalability. In this article, by exploiting the intrinsic linear superposition characteristics of VL, we propose VL-Watchdog, a scalable and always-on signal-level spoofing detection framework that is applicable to both VLC and VLS systems. VL-Watchdog is based on redundant orthogonal coding of the transmitted VL, and can be implemented as a small hardware add-on to an existing VL system. A proof-of-concept testbed was developed to verify the feasibility of VL-Watchdog. The effectiveness of the proposed framework was validated through extensive numerical evaluations against a comprehensive set of factors.