For people who are dedicated to diving or other aquatic activities, hand signals are the only effective communication alternative, to transmit safety information or signaling instructions.
Although there are standardized signs as code for these situations, mastery of these generally falls more on experienced divers. To bridge this gap, a team of researchers proposed a smartphone-based solution.
Underwater communication using mobile
It is estimated that recreational divers usually master around 20 underwater communication signals. On the other hand, the vocabulary of professional divers can exceed 200 signals, including gestures ranging from the level of oxygen, to the performance of cooperative tasks or the notification of the presence of aquatic species.
As they are visual signals, their effectiveness is limited to the closest radius, provided that the appropriate visibility conditions are present. Faced with this, the implementation of alternatives has been proposed, such as bidirectional text messaging, whose practical implementation has been made difficult by the high cost associated with the custom hardware that is needed.
A different alternative was proposed by researchers at the University of Washington, United States. Through a recent project, they managed to show how to achieve underwater messaging on billions of existing smartphones and smartwatches, using only software.
The developed application is called AquaApp and was presented by his team as “The mobile app for acoustic communication and underwater networking that can be used with existing devices.”
“Smartphones rely on radio signals like Wi-Fi and Bluetooth for wireless communication. Those don’t propagate well underwater, but acoustic signals do.”commented the co-lead author of the research, Tuochao Chen. “With AquaApp, we demonstrate underwater messaging using the speaker and microphone widely available on smartphones and watches. Aside from downloading an app on their phone, the only thing people will need is a waterproof phone case rated for the depth of their dive.”.
Through AquaApp, its users have the possibility to select from a list of 240 pre-established messages, corresponding to manual signals used by professional divers, with the 20 most common gestures arranged in a prominent place for easy access. Users can also filter messages by categories, including directional indicators, environmental factors, and equipment status.
The application works with an algorithm developed specifically for this project, which gives it the ability to optimize the bit rate and acoustic frequencies of each transmission in real time, according to parameters such as distance, noise and variations in response. frequency between devices.
When a user wants to send a message to another device through AquaApp, your app first sends a quick note, called a preamble, to the other device. On the caller’s device, AquaApp runs its algorithm to determine the best conditions to receive the preamble. The app then tells the first device to use those same conditions to send the actual message.
The AquaApp team developed a protocol to share access to the submarine network, following a similar dynamic to how WiFi networks control Internet traffic, in order to enable messaging between multiple devices. AquaApp can host up to 60 unique users on your local network at a time.
“According to our experiments, up to 30 meters is the ideal range for sending and receiving messages underwater, and 100 meters for transmitting SoS beacons”Chen said, after successfully testing this system under various conditions of use. “These capabilities should be sufficient for most recreational and professional scenarios”.
Performance tests also showed that the impact on the battery does not impair the autonomy required for the maximum recommended dive time for recreational diving. Over the course of four hours, only 32% of the battery was reduced during tests carried out with Samsung Galaxy S9 mobiles, with the volume at maximum and with the screens always on.
The team behind this project shared through its website not only more technical details about AquaApp, but also presented a video demonstrating its use and shared the code of the Android app under an open source license.
