MetaLink: Extending Air-to-Water Wireless Communications Using Passive Bianisotropic Metasurfaces

Reliable cross medium (e.g., air-water) communication using radio frequency (RF) has remained an open-problem for decades. Currently, underwater devices cannot communicate directly with land-based or airborne devices. Typical solutions are inadequate when communicating through the boundary due to cross-medium boundary reflection/refraction/attenuation effects. We present MetaLink, an RF wireless communication system that enables underwater radios to communicate with airborne ones using novel underwater antenna design and 3D printed bianisotropic metasurface. MetaLink leverages bianisotropic structures that can correct for the severe boundary reflections/refractions between the air/water mediums, opening up the air/water medium as a viable communication channel without the need for multiple types of signals. We further exploit the electromagnetic properties of water to drastically scale down MetaLink's meta-atom size, and improve communication range. To examine real world communications performance from water to air, we prototype MetaLink and measure in a 14 ft deep swimming pool. Moreover, we push the robustness, reliability, and performance of MetaLink to its limit under various real-world circumstances. Our experiments demonstrate that MetaLink can communicate through the water/air boundary with SNR improvements of more than 35dB using WiFi modulation at distances of 14 ft and reach a simulated maximum of 95 ft within water using commercially available equipment and measured data.