They communicate with sound just like dolphins and whales.
Autonomous underwater drones can find shipwrecks in no time and warn of imminent tsunamis. However, radio signals are slowed down in water, making it hard for drones to communicate. So, scientists will now link the oceans in an Internet of sound.
Asearch has been initiated on the Atlantic Ocean floor. A container fell off a ship, and the search team has begun to comb a major, marked out area of the ocean floor.
The search team does not include divers, coastguard vessels, or walkie talkies. The only indication of an extensive, coordinated effort is the weak humming of small, electrically powered propellers.
We are close to Porto, the harbour where the scientists behind the European Sunrise Project are testing whether their newlydeveloped underwater drones can cooperate to find a missing container without human interference. The three drones of the search party are autonomous, and they choose separate routes to search the area optimally with their integrated sonar.
As they work, they communicate with each other by converting their position data into an audio signal that they play under the water. The other drones pick up the sound with their microphones, converting it into digital data, which their computers understand. In this way, the three drones search the marked out area together without overlapping each other’s search patterns.
Very soon, the small group of people who have collected in front of a computer screen by the water’s edge cheer: They can clearly see the outline of the container in the blurred sonar image of the ocean floor.
DRONES MAKE UP SEA NETWORKS
The episode in Portugal is the first practical success of the Sunrise Project, which has so far consisted of a series of minor experiments in small basins. A total of 13 research institutes participate in the project, which aims to make all the participants’ equipment communicate and create a type of underwater Internet.
In the IT industry, people often talk about the “Internet of things”, an Internet, in which everyday items can communicate without human interference. Five minutes before your mobile phone alarm wakes you up, the phone could send a message over the Internet to your Wi-Fi-connected coffee machine to brew the first cup of the day, so it is ready when you enter the kitchen after taking a shower.
Similarly, communication buoys on the sea surface, drones in the water, and measuring instruments on the sea floor will be able to communicate and send data to each other. This means that scientists need not constantly be in contact with their underwater robots to tell them what to do. Scientists have named it the “Internet of Underwater Things”.
Over time, the growing numbers of undersea units will be able to create a worldwide network under the water, which will make of a series of tasks in seas, lakes, and rivers easier.
SALT WATER IS A PROBLEM
Today, big cities are so closely packed with wireless networks that it is a challenge to find areas without several available Wi-Fi networks. Even in the most remote corners of the world, where the closest mobile phone mast is far away, it is now possible to check your e- mail via communication satellites in space.
However, good Internet connections are restricted to people above the water. More than 70% of our planet’s surface are covered by oceans and lakes, and beneath the surface, traditional wireless networks cannot communicate via radio waves.
Although radio waves travel at the speed of light, they are very efficiently slowed down by water. In the sea, the problem is even bigger, as the electric conductivity of salt water will quickly spread a radio signal, so it will never reach the receiver. As radio is not practical to use under water, scientists had to use alternative methods for sending data below the sea surface.
SOUND SWIMS FURTHER THAN WI-FI
Their solution was inspired by the animal kingdom. Whales are famous for their songs, which they use to send messages across long distances. By using sound under the water instead of radio waves, the reach of the undersea communication is expanded from a few metres to several kilometres.
The audio signal underwater technology is very much like the modems that were used by many home computers 20-30 years ago. They sent data in the form of audio signals via an ordinary phone connection. When you lifted the receiver, as the computer was
transmitting data, you could hear a lot of noise. Unfortunately, the speed of the drone data transmission is also at the same level as in the early 1990s. They can only send about 20 kilobits per second, and that is much too slow to send a series of photos from a camera or sonar. So far, scientists have to settle for sending simple measuring data and individual photos.
If drones have to send large quantities of data back to the scientists , one of them can go to the sea surface and send the collected data via an airborne radio signal, using its integrated antenna.
So although the audio signals are have very long range, it does not change the fact that the drones can only send very brief messages to each other. Consequently, the scientists would very much like to integrate technology for transmitting data over short distances between the drones by means of light. That would all at once make the transfer up to 500 times faster than with the existing audio signals.