“Other than downloading an app to their phone, people just need a waterproof phone case rated for the depth of their dive,” says Chen.
Researchers transmit energy wirelessly over 30 meters using infrared light
Here’s how Apple’s original iPhone changed the smartphone industry forever
“The underwater scenario introduces new problems compared to airborne applications,” explains Chan. “For example, fluctuations in signal strength are amplified by reflections from the surface, ground and shore. The movement caused by people, waves and objects nearby can disrupt data transmission. In addition, microphones and speakers have different characteristics depending on the smartphone model. We had to adapt to these and other factors in real-time to ensure AquaApp would work in real-world conditions.”
These other factors include the tendency of devices to rapidly change position and proximity in the current, and the various noise profiles the app may encounter due to the presence of ships, animals, and even low-flying aircraft.
The team created an algorithm that allows AquaApp to optimize the bitrate and acoustic frequencies of each transmission in real time based on certain parameters, including distance, noise and variations in frequency response between devices. When a user wants to send a message to another device, their app first sends a short note called a preamble to the other device. AquaApp on the second device runs the algorithm to determine the best conditions for receiving the preamble; It then instructs the first device to use the same conditions to send the actual message.
Researchers developed a network protocol to share access to the underwater network, similar to how WiFi networks route internet traffic to support messaging between multiple devices. AquaApp can host up to 60 unique users on its local network at the same time.
The team tested the real-world utility of the AquaApp system in half a dozen locations with varying water conditions and activity levels, including under a bridge in calm water, in a popular riverside park with strong currents, next to the fishing port by a busy lake, and in a bay with strong currents Waves. In a series of experiments, they evaluated AquaApp’s performance at distances of up to 113 meters and depths of up to 12 meters.
“Based on our experiments, up to 30 meters is the ideal range for sending and receiving messages underwater and 100 meters for sending SoS beacons,” Chen said. “These skills should suffice for most recreational and professional scenarios.”