South African researchers developed world-leading underwater Wi-Fi technology
The Council for Scientific and Industrial Research (CSIR) has developed underwater Wi-Fi technology to transmit sonar images almost instantly.
This will enable underwater drones to broadcast high-resolution sonar images of ocean pipelines, subsea cables, and hidden underwater mines faster than ever before.
They conducted a recent sea trial in Simon’s Town, which tested the technology, and are now fine-tuning two critical technologies that make this possible.
“One technology is synthetic aperture sonar (SAS), and the other is underwater Wi-Fi using sound waves,” said CSIR lead researcher Kiri Nicolaides.
Mounted together on an unmanned underwater vehicle, the two complementary systems will solve a double problem that has limited underwater exploration.
- Poor-quality sonar images of the ocean and dam floors taken at a distance.
- The need to wait for the vehicle to surface to retrieve and process image data into useful maps and high-quality visuals.
The CSIR team is solving the first problem in imaging using specialised signal and image processing algorithms.
They also employ novel transducers, electrical components that act as underwater antennas to transmit and receive sound waves.
Compared to traditional transducers, these locally developed, wide-bandwidth components give the CSIR’s SAS systems four times more bandwidth.
More bandwidth means higher data rates with fewer errors, which translates into higher-resolution images.
“SAS is like the high definition television version of sonar,” said Josiah Jideani, a senior engineer in the CSIR’s ultrasonics research group.
“SAS shines when you’re looking for very small targets or objects that conventional types of sonar won’t be able to detect.”
In the oil and gas industry, SAS can be used for underwater pipeline inspections to check for small leaks or damage.
It can also be used for mineral prospecting, geological surveys, marine archaeology, buried underwater mine detection and undersea internet cable monitoring.
Using drones and towed underwater platforms
The sonar system can be mounted on Autonomous Underwater Vehicles (AUVs) or on a towed underwater platform.
The challenge is maintaining a stable speed and straight trajectory, both of which are essential for synthetic aperture processing.
Light boats and surface waves introduce motion that must be corrected algorithmically, in addition to imaging and autofocusing algorithms.
At the CSIR underwater testing facility in Pretoria, the sonar team calibrates the underwater transducers and electronics.
They also fine‑tune signal processing algorithms and evaluate performance under controlled conditions.
The team then performs ocean and dam tests that introduce uncontrollable variables such as waves, currents, speed changes and platform instability.
Data collected during field tests are returned to the facility, where the team adjusts the algorithms to account for real‑world conditions.
This iterative cycle between controlled testing and field deployment is central to the technology development process.
In parallel, researchers are tackling the second problem: how to retrieve information from the surface while a system remains submerged.
CSIR senior engineer Elna Niemann explained that radio waves used for high-speed communication above water typically don’t travel well underwater.
“You can’t just submerge a wireless modem underwater and get the same kind of performance you would on land,” she said.
However, sound waves travel very well underwater. Her team is developing an underwater wireless acoustic communication system.
Also known as Broadband Underwater Data Communication, this is, in essence, underwater Wi-Fi using sound.
The novelty lies in a specialised ultra-wide bandwidth transducer that provides up to five times more bandwidth than commercial acoustic modems.
“We can offer internet-like speeds compared to the commercial offering, which is more in line with telegraph speeds,” she said.
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