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Stephen Chen

A milestone for underwater communication has been achieved following testing of new technology that features a powerful method of data encoding, according to scientists involved in the project.
The 92150 unit of the People’s Liberation Army (PLA) in collaboration with Xiamen University recently conducted tests on the new underwater data transmission technology at an undisclosed location in the South China Sea, with a water depth of 3,000 metres (9,842 feet), far from the Chinese mainland.
Scientists deployed a small hydrophone 1,000 metres below the surface and successfully received signals transmitted from a ship that was 30km (18.6 miles) away, achieving a data transmission speed of 4,000 bits per second (bps).
This sets a new record for the performance of underwater acoustic communication equipment in open reports.
Extremely low-frequency (ELF) radio waves can penetrate the water, but their efficiency is very low, with only a few characters being transmitted per minute. Sound waves are more efficient but susceptible to refraction from the sea surface and seabed, ocean currents, and other environmental disturbances, making it difficult to transmit large amounts of data over long distances.
The previous record was also held by China. In March 2022, Zhejiang University and China State Shipbuilding Corporation conducted a similar test, achieving a distance of 14km (8.7 miles) at a rate of 3,000 bps.
Benefiting from the booming telecommunications industry, China’s advantage in wireless communication technology is expanding from the air to the sea. These advanced technologies can support the large-scale application of underwater drones powered by artificial intelligence, and they could have a profound impact on future military and geopolitical power struggles.
This includes China’s response to Nato’s expansion.
Nato has identified China as a major target and is actively seeking to expand its reach into Asia – which has triggered alarm bells for Beijing.
The current underwater acoustic communication protocol for Nato submarines, JANUS, was launched in 2017. According to publicly available information, the longest communication supported by JANUS is 28km (17.4 miles), but at that distance the sound wave frequency drops to 900Hz, allowing only a small amount of information to be transmitted.


JANUS uses a method called OFDM to transmit signals. OFDM technology can split data streams and modulate them onto multiple carrier sound waves to achieve high-speed transmission over a short distance.
In China, though, OFDM is considered an outdated technology.
This is because communication devices using OFDM require higher operating power, and the related components are complex and expensive. Plus, as the communication distance increases, noise also increases, leading to a sharp deterioration in performance, which is not helpful to the large-scale deployment and collaboration of small unmanned platforms.
Instead, the Chinese team has used higher-order polarisation weight (HPW).
Underwater acoustic communication equipment using the HPW encoding method does not require data splitting and can modulate information onto a single carrier wave for transmission and reception, significantly reducing device power consumption and complexity.
The 92150 unit, based in Quanzhou, Fujian, specialises in unmanned underwater operations.
They collaborated with a team of scientists led by Professor Tong Feng at Xiamen University’s college of ocean and Earth sciences to develop the new device.
During testing, Tong’s team achieved zero error code transmissions over an ultra-long distance of 30km (18.6 miles) at frequencies between 4,000Hz and 8,000Hz.
Tong and his colleagues described Huawei’s encoding method as “precise and stable” in a peer-reviewed paper published in the Chinese Journal of Acoustics in July.


The HPW method originates from a significant breakthrough in number theory and was jointly developed by Huawei scientists from China, France and Canada. It can transmit information with unprecedented efficiency and eliminate noise.
Polar code was invented by Turkish scientist Erdal Arikan in 2008 and is the first algorithm that can elevate information transmission efficiency to the theoretical limit.
The implementation of this technology is very challenging. Huawei is one of the few telecommunications companies that support this path.
Professor Arikan received a special award from Huawei’s founder, Ren Zhengfei, in 2018.
“Without the vision and technical contributions of Huawei directors and engineers, polar codes would not have made it from lab to a standard in less than 10 years. And as engineers, there is no greater reward than seeing our ideas turn into reality,” Arikan said at an award ceremony in Paris.
Polar codes are now widely used in 5G communications and consumer electronic products. For example, Huawei’s wireless headphones using this encoding achieve a data transmission rate six times higher than the latest Bluetooth products, with one-thirtieth of the latency, double the coverage distance, and a 40 per cent reduction in power consumption.
Meanwhile, the underwater competition between China and the United States is intensifying.
In June, the US military proposed using unmanned surface and underwater drone swarms to transform the Taiwan Strait into an “unmanned hellscape” in its latest plan for a military intervention over the island of Taiwan.
China has also established a high-density underwater surveillance and communication network in the South China Sea and around Taiwan.
Some Chinese military researchers have also recently proposed planting unmanned underwater vehicles on seabeds near US ports or overseas military bases to perform tasks such as intelligence gathering or strikes – which could be activated following a potential US attack on China.


This story has been updated to clarify that the polar code is a widely used technology and not only owned by Huawei.


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Chinese scientists working with the PLA receive signals transmitted from 30km away, achieving data transmission speed of 4,000 bps


Chinese scientists working with the PLA receive signals transmitted from 30km away, achieving data transmission speed of 4,000 bps.


China sets a new record in South China Sea submarine communication test

.css-1mniedq{color:inherit;font-weight:inherit;font-size:inherit;font-family:inherit;line-height:inherit;}Chinese scientists working with the PLA receive signals transmitted from 30km away, achieving data transmission speed of 4,000 bps

Chinese scientists working with the PLA receive signals transmitted from 30km away, achieving data transmission speed of 4,000 bps