The Internet of Things has the potential to cover every inch of Earth, thanks to the reach of cellular and satellite-based communications technologies. However, around 70 percent of the planet is underwater and, therefore, currently outside the IoT’s reach. But Chiara Petrioli, a professor of computer science at the University of Rome La Sapienza, is leading an international research project focused on developing communications protocols for a submersible Internet of Things.
The research, called the SUNRISE project (while it’s a bit lost in translation, “SUNRISE” is derived from a longer title: Sensing, monitoring and actuating on the UNderwater world through a federated Research InfraStructure Extending the future internet) is developing protocols for transmitting and receiving data via acoustic signals by autonomous underwater vehicles (AUVs), also known as underwater drones. Developed three years ago, SUNRISE receives the majority of its funding through the European Commission’s Future Internet Research and Experimentation (FIRE) program. The communication technology has already been put to use during an effort to locate a cargo container that had fallen into the sea near a port in Portugal, and is currently being evaluated for a wide range of other applications for the oil and gas industry, port security, and environmental testing and monitoring.
“Our approach is [to use] multiple technologies and to be adaptive,” Petrioli says. She and her team are building a software-defined communication stack known as SUNSET (a nickname derived from the Sapienza University Networking framework for underwater Simulation Emulation and real-life Testing), designed to test protocols for underwater sensor networks and then evaluate these through software simulation and in-lab emulations, followed by underwater trials. This is done independent of specific underwater hardware platforms.
Drones can be outfitted with a range of sensors that measure carbon dioxide, pH, pressure, conductivity, salinity, methane or oxygen levels. They can also be outfitted with cameras and microphones. If the drones are fitted with mesh-networking radios, they could communicate with each other, passing data up to and receiving instructions from a central gateway on the water’s surface.
The earliest adopters of such underwater drones, Petrioli says, will likely include oil and gas companies, which could use the drones to monitor the health of offshore drilling platforms or pipelines and alert the companies to signs of weakness— by detecting air bubbles escaping from pipes, for instance—that require preventative maintenance. In fact, the project has spun off a commercial provider of underwater sensor network technology, called WSense, which is working with a team of researchers in the Netherlands to test an underwater drone that could monitor leaky oil pipelines.
Drones might also be used to scan the underwater areas at a port, either to identify security threats or to locate lost items. A network of drones deployed in Portugal was employed to find a high-value cargo container that had fallen from a ship. “You can imagine, after a disaster or shipwreck, underwater drones could be very valuable,” Petrioli states. In the case of a shipwreck, plane crash or oil leak, they could quickly identify wreckage or environmental risks. The drones could be spread over a wide area, communicating via a mesh network and surveying the area much faster than humans could.
According to Petrioli, using drone networks to perform underwater environmental monitoring also holds tremendous potential, and will likely generate a great deal of data for environmental scientists and policy makers.
Underwater drones, such as those made by Sunnyvale, Calif.-based Liquid Robotics, are already being used in commercial deployments. However, such drones are tethered to a floating base station. Untethered drones can travel much deeper and range farther from the base station.
“Overcoming the limits of underwater communications is our biggest hurdle,” Petrioli says. Broadly, there are three options for wireless communication underwater: radio, optical and acoustic. “Radio has limits because it suffers from very strong attenuation underwater. So if you want a limited size of antenna, you need to operate at frequencies that are high enough, and you get just a few meters of read range. It is very different than using radio with terrestrial systems.” Optical systems require a clear line of sight between the drones, which is far from a guarantee since water is often quite turbid. This leaves acoustic systems, which support the longest underwater read ranges—around 1 kilometer (0.6 mile)—but have a disadvantage in terms of the rate at which data is transmitted.
“The acoustic modems have data rates of about 10 kilobits per second,” Petrioli explains. “That’s slower than Internet modems in the ’90s.” In addition, the acoustic signals are prone to interference from a range of factors, including waves, water temperature and salinity.
Much of the group’s research efforts focus on improving the speed and performance of acoustic modems. The drones communicate via acoustic transmissions with a modem located either on shore or in a boat, or floating on a buoy. The data is collected from the modem and then transmitted, either via a 2.4 GHz or 2.5 GHz radio signal, to an Internet-connected gateway located on shore—or, if the buoy is far offshore, the data is sent to a central server over a satellite communication link.
SUNRISE-based projects are being developed through a consortium of universities and commercial partners, including the NATO Science and Technology Organization‘s Centre for Maritime Research & Experimentation; EvoLogics (a manufacturer of acoustic modems); the University of Porto, in Portugal; the University of Twente, in the Netherlands; Turkish underwater drone maker SUASIS; the University of Buffalo, in New York; and Nexse, a software company that is developing an integration platform to store, analyze and present the data that the drones generate.
Petrioli says the acoustic signaling technology used was actually developed by studying the ways in which dolphins and other marine animals communicate. The military, as well as oil and gas exploration companies, use sonar technology—which employs acoustic signals to detect objects underwater—to chart undersea resources. However, sonar’s acoustic transmissions have been implicated in harming marine life by disrupting their communication patterns or hunting ability.
Sonar systems, Petrioli says, “operate at higher power than our acoustic communication system does.” She adds that such solutions also typically transmit at lower frequencies (as low as 20 hertz) than do the acoustic signaling systems for which SUNRISE is developing its protocols. As such, she says, they propagate further and affect marine life more significantly.
According to Petrioli, the drones could also be used to record underwater sounds as a means of studying marine science. Additionally, the researchers are developing systems that could detect noise indicative of marine species’ communication, and automatically silence the drones’ acoustic signaling until the marine mammals leave the area. Oil and gas companies, or other entities that create underwater noise pollution, could utilize the same technology to silence or reduce their own activities in order to avoid conflict with marine life.