LiRF: Light-Based Wireless Communications Supporting Ubiquitous Radio Frequency Signals

As the Internet of Things (IoT) becomes increasingly prevalent, there is a surge in wireless-connected devices. In this context, one technique that has garnered significant attention is visible light communication (VLC) due to its ultra-wide and license-free frequency resource. However, a critical issue in utilizing VLC in IoT lies in its lack of smooth cooperation with ubiquitous radio frequency (RF)-based wireless networks. RF signals can use duplex techniques to transmit and receive bidirectional signals with one antenna. In contrast, VLC's light-emitting diodes (LEDs) and PIN diodes cannot operate in duplex mode, posing challenges in establishing two unidirectional VLC links. To address the mismatch between VLC and RF, we propose a light-based RF transceiver design called LiRF, capable of smooth transmission of RF signals through VLC for IoT devices. To verify its feasibility, we first build a prototype using 802.11ax (WiFi-6) network interface cards (NICs) in the 5 GHz channel. Experimental results show that LiRF is compatible with the 802.11bb standard, supporting TCP/IP data streams at 750 Mbps with a 200 MHz Superluminescent Diode-PIN (SLD-PIN) transceiver and at 600 Mbps with a 180 MHz LED-PIN transceiver. To the best of our knowledge, this is the first real-time bidirectional VLC system utilizing WiFi NICs capable of achieving near-Gbps data rates for a single spatial stream without altering the RF designs. LiRF paves the way for seamlessly integrating VLC into upcoming IoT networks, supporting high-speed, low-latency applications like Virtual Reality and Augmented Reality.