LiFi-based Sensing: From Single to Multi-modal and Cross-modal Integration

Sensing and localization are envisioned to play a key role in shaping the future of the sixth-generation (6G) of wireless networks by enhancing their ability to make intelligent decisions. Existing research efforts have primarily focused on utilizing radio-frequency (RF) signals to facilitate sensing tasks, thereby contributing to the heightened strain on the already congested spectrum, due to shared hardware and frequency bands. Additionally, with the explosive growth in the number of connected devices and the diverse sensing scenarios envisioned, exploring alternate frequency bands becomes of paramount importance. Within this context, it has been demonstrated that Light Fidelity (LiFi), which utilizes existing lighting infrastructure, stands out as a promising technology due to its highly accurate 3D sensing and localization capabilities. Motivated by this, in this paper, we explore a forward-looking perspective wherein LiFi-empowered wireless networks integrate illumination, communication, and sensing capabilities. Specifically, we thoroughly review LiFi-based sensing and localization principles, highlighting technologies set to enhance its performance. Subsequently, we introduce the concept of LiFi-empowered multi-modal sensing as a promising technological advancement achieved by integrating LiFi with other sensory data sources. This fusion empowers sensing systems to effectively adapt to environmental conditions. Finally, we shed light on potential research directions and challenges that are set to realize the full potential of LiFi-empowered multi-modal sensing.