Realization of RF Signal over Bidirectional Optical Wireless Communication Links

Different from radio frequency (RF) signals which may use time division duplexing (TDD), frequency division duplexing (FDD) or other duplex techniques, visible light communications (VLC) have faced a critical issue in transmitting RF based wireless signals directly without changing any existing signal processing designs. As defined by the IEEE 802.11bb standard, transmitting and receiving the originally bidirectional duplex-mode RF signals from one antenna, e.g., the time division multiple access (TDMA)-like wireless fidelity (WiFi) signals, using two unidirectional VLC links is challenging. In VLC the light-emitting diodes (LED) and PIN diodes cannot work in a duplex mode. To address the mismatch problem between VLC and RF, while carrying RF signals on top of the VLC links, we propose a light-based RF transceiver design, named LiRF, capable of seamlessly converting RF signals into VLC. The proposed LiRF architecture, comprising a frequency detection module, a bidirectional signals separation module, and an optical transceiver module, is feasible for any RF communication system. To validate the real impact of LiRF, we build a prototype using separate components and two IEEE 802.11ax (WiFi-6) network interface cards (NICs) in the 5GHz channel. Compared with state-of-the art offline single-directional WiFi-over-VLC system (e.g., WoV), LiRF are designed for bidirectional data transmissions with real-time applications support capability. Experimental results indicate that LiRF links can support 720 Mbps data streams using a LED-PIN transceiver. LiRF is a transparent VLC system design supporting WiFi NICs, and it is proved to be able to bridge the gap between VLC and RF communications, which paves the way for the smooth integration of VLC into existing and future RF systems.