-Originally published in IEEE Spectrum on June 22, 2020
Communicating underwater has always been a hassle. Radio transmissions, the ubiquitous wireless standard above the waves, can't transmit very far before being entirely absorbed by the water. Acoustic transmissions (think sonar) are the preferred choice underwater, but they suffer from very low data rates. Wouldn't it be nice if we could all just have Wi-Fi underwater instead?
Underwater Wi-Fi is exactly what researchers at the King Abdullah University of Science and Technology (KAUST) in Thuwal, Saudi Arabia, have developed. The system, which they call Aqua-Fi, uses a combination of lasers and off-the-shelf components to create a bi-directional wireless connection for underwater devices. The system is fully compliant with IEEE 802.11 wireless standards, meaning it can easily connect to and function as part of the broader Internet.
Here's how it works: Say you have a device underwater that needs to transmit data (for the KAUST researchers, it was waterproofed smartphones). They then used a regular old Wi-Fi signal to connect that device to an underwater "modem."
Specifically, they used a Raspberry Pi to function as that modem. The Raspberry Pi converted the wireless signal to an optical signal (in this case, a laser) that was beamed to receiver attached to a surface buoy. From there, established communications techniques were used to send the signal to an orbiting satellite. For the underwater device to receive data, the process is simply reversed.
Aqua-Fi stems from work that the KAUST researchers did back in 2017, when they used a blue laser to transmit a 1.2-gigabit file underwater. But that wasn't interesting enough, according to Basem Shihada, an associate professor of computer science at KAUST and one of the researchers on the Aqua-Fi project.
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