Passengers wait for a subway train at Jamsil Station on Line 2 in Seoul, May 13, 2020. Korea Times file

By Baek Byung-yeul

The high output of 5G relay base stations is found to have caused frequent malfunctions of sensors on subway screen doors that detect obstacles, threatening the safety of passengers, a lawmaker warned Sunday.

Kim Young-joo, a lawmaker with the main opposition Democratic Party of Korea (DPK) and a member of the National Assembly's Science, ICT, Broadcasting and Communications Committee, said the 5G relay base stations installed in subway platforms by SK Telecom, KT and LG Uplus have caused the detection sensors of screen doors to malfunction.

Since the country commercialized 5G network services in 2019, the three telecommunications companies have installed relay base stations in order to let their customers use network services inside the subway station platforms and trains.

Screen doors are physical barriers that open and close automatically to ensure the safety of passengers as trains approach station platforms. According to state-run Korea Railroad Corporation (KORAIL), 99.7 percent of subway stations have installed the barriers nationwide.

After analyzing data received from KORAIL, the lawmaker said malfunctions caused by the 5G relay base stations occurred at 30 out of 38 subway stations in Seoul from June 2020 to August 2022.

KORAIL concluded that the cause of the problem of the screen doors was the high output of the 5G relay base stations and continuously requested the mobile carriers to fix the problem, because such malfunctions could lead to a fatal accident. In 2021, a passenger was trapped between the screen door and the train at Mangu Station on the Gyeongui-Jungang Line in Seoul.

Subway passengers at Jamsil Station on Line 2 in Seoul, May 24, 2021. Yonhap

The lawmaker added that KORAIL asked the three telecommunications companies to cut off power to all 5G relay base stations at the stations in January. In response, SK, KT and LG conducted investigations with Korea Radio Promotion Association (RAPA) and concluded in April that the high output of the base stations was the factor that caused the malfunction.

According to regulations, the output of the base stations cannot exceed 5 volts. But those 5G relay base stations have maintained theirs power output at 24 volts, which is about five times more than the standard.

Although it turned out that the high output of their machines were behind the malfunctions, the lawmaker pointed out that the three mobile carriers did not take proper actions, because they only adjusted the location and height of the equipment, instead of lowering the power output.

As the malfunctions continued, KORAIL asked the mobile carriers to block the output of all 5G relay base stations installed at subway stations on Sept. 19.

"It is regrettable that the three mobile carriers have been trying to maintain 5G service quality while ignoring the safety and lives of passengers," the lawmaker said. "For public safety, the companies should immediately come up with measures to lower the output of the devices or replace them with new ones in cooperation with the related government institutions."

Regarding the issue, an official from a telecommunications company here said it is closely working with the government and KORAIL to address the issue.

"Due to sensor malfunctions, three telecommunications companies have been blocking the output of some 5G relay base stations since this year. To this end, the three companies are actively cooperating with the Ministry of Science and ICT and KORAIL," a spokesman for a mobile carrier said on condition of anonymity.