BEIJING: Chinese researchers claim to have built and tested an underwater communications technology in the depths of the South China Sea that could allow drones and submarines to reach 30,000 square kilometers (11,600 sq mi), or roughly the size of Belgium. allows for. Will be able to maintain contact in the area.

A listening device picked up sound signals from 105 km (65 mi) away at a depth of 200 m (656 ft) during a field test in an essential route for submarines, according to the study by the team in northwestern China. . ,

When compared to the bandwidth of very low-frequency radios sent to nuclear submarines by Naval Command using the largest land-based antennas in the world, a data transmission rate of about 200 bits per second (bps) was achieved.

The researchers claimed that the encrypted messages were error free, despite the loud background noise.

Acoustic communication of this speed and quality is usually limited to a range of less than 10 km using commercially available technology.

Using British hydrophones, South Korean researchers conducted an experiment last year that noted a transmission rate of 128bps over a distance of 20 km.

Low-frequency sounds, such as whale calls, can travel hundreds or thousands of kilometers across the ocean, but identifying these signals and extracting useful information from them is challenging.

Sound waves can propagate in different directions and at different rates as they move through streams or hit an ocean mountain. The distortion and weakening of the signal when it reaches the receiver gets worse with increasing distance.

The results of the South China Sea experiment proved the new technology's "efficacy and good performance" in increasing underwater communication range and efficiency, said Professor Liu Songzuo, project lead scientist at Harbin Engineering University, one of the US government-sanctioned Chinese universities. Gave. , in a paper published September 6 in the domestic peer-reviewed journal Acta Acoustica.

The 3,800 m deep ocean floor lies between the tensely contested Paracel Islands, known as Zisha in mainland China, and the Taiwan-controlled Dongsha Islands, also known as Pratas in Taiwan. Is. , According to some military experts, the area serves as an important route for submarines to enter and exit the waters near China.

According to publicly available information, China has deployed unmanned surface and underwater ships to patrol the area and collect data.

The docking and recharging of a deep-sea robotic drone in the South China Sea will take place over the next few years, as planned by the Chinese government.

Chinese scientists are also working on drones powered by disposable nuclear reactors that can fly great distances as a swarm and smart weapons that can be buried in the ocean floor and activated during a conflict.

According to the researchers involved in the programmes, these AI-powered machines need to communicate continuously to share intelligence, plan routes or coordinate an attack.

According to Liu in the paper, in deep-sea long-distance communication, "Various techniques with low requirements on obtaining signal-to-noise ratio have been widely used and good results have been obtained."

The frequency available for long-distance underwater acoustic communication is band constrained, and the low efficiency of these technologies makes for a low achievable communication rate.

According to Liu, the test was conducted on a windy day in which the research ship was shaken by the waves, while a strong ocean current pushed the hydrophone array away from the best listening position.

Under water, there was unforgiving terrain with rocks and canyons, allowing sound waves to be absorbed, deflected and distorted.
According to Chinese researchers, more than 70% of the sensors failed to detect anything in such a difficult environment.

Some sensors could only detect signals that were a few decibels louder, or were barely audible when breathing. Additionally, they claimed that these signals were largely hidden by intense background noise generated by human and natural activities in the ocean.

To address these issues, Liu's team claimed to have created a new communication protocol.

The technology, which took its inspiration from mobile phone communication, can split signals into many separate but connected parts and emit them as sound waves in all directions.
Some of these waves can be picked up from different directions and, at times, by the receiver.

The receiver used an algorithm to recognise each of these waves and reconstruct the complete message using random information from the data collected.

With the help of actual data gathered from the South China Sea, the mathematical model used in this study was created and evaluated in order to perform better in the area.

Liu's team announced earlier this year at a conference that they were working on a new technology to transform sound signals into whalesong in order to conceal military channels.

Large-scale data transmission, like that of pictures and videos, is still a problem for sound-based communication. The development of laser communication devices for fast transmission over a shorter distance than 100 metres is the focus of an international competition among researchers.

After a 2017 underwater experiment by researchers from Fudan University in Shanghai achieved 1 gigabit per second over 63 metres (206 feet), China now holds the record.

According to some Chinese researchers, the speed and range of underwater laser devices will be significantly increased by next-generation communication technology.

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