China claims to have developed and tested underwater communications technology that allows drones and submarines to stay connected over more than 30,000 square kilometers.
The South China Sea served as a testing ground for the technology. According to reports, the The listening instrument picked up sound signals from a distance of 105 km at a depth of 200 meters during a field test in a passage important for submarines.
The results of the latest experiment demonstrated the usefulness and good performance of the new technology in extending the range and effectiveness of underwater communications.
The data transfer rate was around 200 bits per second (bps). This compares to the bandwidth of very low frequency radios associated with nuclear submarines by a naval command using the world’s largest land-based antennas.
The researchers claimed that the encrypted messages were error-free despite loud background noise. This could be seen as an important innovation as audio transmission of this speed and quality is often limited to a range of less than 10 kilometers with commercially available technology.
In 2021, South Korean researchers found a transmission rate of 128 bps over a distance of 20 km in an experiment using British hydrophones.
In 2017, researchers at Fudan University in Shanghai conducted an underwater experiment that achieved 1 gigabit per second over a distance of 63 meters (206 feet), setting a new record for China.
Low-frequency sound can travel hundreds or even thousands of kilometers in the ocean, but detecting these signals and extracting useful information can be challenging.
When sound waves cross rivers or hit an ocean mountain, they can travel in different directions and at different speeds. As the signal travels further, it becomes distorted and weaker by the time it reaches the receiver.
In a paper published in the domestic scientific journal Acta Acustica on Sept. 6, lead scientist Professor Liu Songzuo of Harbin Engineering University explained the technology’s effectiveness, the Chinese report added.
Harbin Engineering University is one of the Chinese institutions sanctioned by the US government.
The experiment was conducted by Chinese scientists on a 3,800-meter-deep seabed between the Taiwan-controlled Dongsha Islands, known as Pratas in Taiwan, and the hard-fought Paracel Islands, known as Xisha in mainland China.
According to some military experts, the area served as an important route for submarines entering and exiting the waters near China.
Steps taken by the Chinese team
It’s no secret that China uses unmanned surface vehicles and underwater vessels to monitor the area and regularly collect intelligence. Widespread use of drones gives Beijing a significant military advantage, allowing it to covertly collect hydrographic data in neighboring nations’ territorial waters.
China also plans to build a deep-sea station in the South China Sea that will be operational for robotic drone docking and recharging in the coming years. In June, the country also launched the world’s first unmanned drone carrier, which uses AI to autonomously navigate the open water.
The latest report also noted that the country is also developing drones powered by single-use nuclear reactors that can travel long distances in swarm formation, as well as smart weapons that can be hidden underwater and detonated during a conflict.
According to experts involved in the programs, these AI-controlled machines must constantly communicate to exchange information, plan routes or coordinate an attack.
The experiment was conducted on a stormy day when waves smashed against the research vessel and a strong ocean current pulled the hydrophone array away from the ideal listening position. Under the sea there was a rugged topography with cliffs and canyons that could absorb, deflect and distort the sound waves.
The Chinese media report found that more than 70% of the sensors could not detect anything in such a difficult environment. The signals picked up by the few sensors were barely a few decibels, or less than a breath.
These signals were generally drowned out by high levels of background noise caused by natural and man-made ocean activity. To address these issues, the team appears to have developed a new communication protocol.
Inspired by cell phone communications, the technique could pack the signal into many discrete but connected parts and emit them in all directions as sound waves. Some of these waves could be received by the receiver from different directions and at different times.
An algorithm helped the receiver identify these waves and reconstruct the entire message from random bits of the captured data. The mathematical model used in this study was constructed using real data from the South China Sea and evaluated to improve its performance in the region.