Chinese submarine comms systems sets a new record and irks NATO

China has reportedly tested a HuaweiTechnologies’ polar code device that helps advance underwater communications. In tests done in the South China Sea, the People’s Liberation Army (PLA) transmitted a message 18.6 miles (30 kilometers) underwater while testing the communication equipment, according to a Chinese media outlet.

Scientists placed a small hydrophone 1,000 meters (3,280 feet) underwater and successfully received signals from a ship, achieving a data transmission speed of 4,000 bits per second (bps).

PLA conducted the experiments, working with Xiamen University, which recently tested the new underwater data transmission system in an undisclosed location in the South China Sea.

Although Ultra Low Frequency (ULF) radio waves can travel underwater, they only send a few characters of data every minute. Even though sound waves travel quicker, long-distance data transmission is difficult because of their susceptibility to disturbances from the seafloor, the sea surface, and ocean currents.

In 2008, Turkish academic Erdal Arıkan introduced polar code, a sort of error-correcting technique. By guaranteeing that the data is transferred precisely and error-free, it helps to increase data transmission, particularly when the signal is strong.

Implementing this technology is very challenging. Huawei is one of the few telecommunications companies that has advanced telecommunications using this method. A Chinese media source claims that Huawei’s newly tested technology breaks previous records for underwater acoustic communication devices.

According to the South China Morning Post (SCMP), China previously set the record for underwater data transmission in March 2022. Zhejiang University and China State Shipbuilding Corporation conducted a test that transmitted data over 14 km (8.7 miles) at a rate of 3,000 bps.

Polar Codes are widely adopted in 5G and consumer electronics and are revolutionizing data transmission. Huawei’s wireless headphones, which use this technology, achieve six times the data speed of the newest Bluetooth devices, with one-thirtieth the latency, twice the coverage, and 40 percent lower power consumption.

NATO has identified China as a key strategic focus and is expanding its influence into Asia, raising concerns in Beijing. NATO’s current underwater communication protocol for submarines, JANUS, launched in 2017, supports communication up to 28 km (17.4 miles).

However, the sound wave frequency drops to 900Hz at this range, allowing only limited data transmission. JANUS uses Orthogonal Frequency Division Multiplexing (OFDM), which splits data streams across multiple sound waves for short-distance, high-speed transmission.

According to SCMP, in China, OFDM is seen as outdated due to its high power requirements, complexity, and poor performance over longer distances. To address these limitations, a Chinese team has developed a new underwater communication system using Higher-Order Polarisation Weight (HPW) encoding, a method introduced by Huawei in 2017.

Unlike OFDM, HPW does not require data splitting and can encode information onto a single carrier wave, reducing power consumption and device complexity. The PLA’s 92150 unit, based in Quanzhou, Fujian, collaborated with Professor Tong Feng’s team from Xiamen University’s College of Ocean and Earth Sciences to create this advanced system.

In testing, they achieved error-free data transmission over 30 km (18.6 miles) at frequencies between 4,000Hz and 8,000Hz. SCMP reports the breakthrough, rooted in number theory, was published in the Chinese Journal of Acoustics in July and is part of a larger family of polar codes developed by Huawei.