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KDDI network disruptions continue to affect "au" mobile service

An "au" mobile phone service shop is pictured in Tokyo on July 4, 2022. (Kyodo)

TOKYO (Kyodo) -- Users of Japanese telecom giant KDDI Corp. mobile service continued to have problems making voice calls on Monday, two days after maintenance work disrupted up to 39 million mobile connections and a range of business activities.

    Internet and data communication services have been "largely restored," but users of "au" mobile phones are still having difficulty making calls due to a temporary limit placed on network traffic, according to the country's second-largest mobile carrier by subscribers.

    The operator did not have a firm timetable set for full service restoration as of 11:30 a.m.

    The disruption, which occurred around 1:35 a.m. Saturday, has affected up to 39.15 million mobile connections and disrupted banking systems, transmission of weather data, parcel deliveries and network-connected cars.

    Speaking at a press conference Monday, Deputy Chief Cabinet Secretary Seiji Kihara said the trouble is "extremely regrettable" as mobile networks are important infrastructure for the public and their activities, and that he has demanded an "in-depth explanation for users" from the carrier.

    KDDI's problems come at a time when the government is pushing for digitalization as one of its top priorities. It also highlights the risk of a large-scale communications breakdown as everything from cars to factory equipment becomes connected to the internet.

    Some automatic teller machines at Ogaki Kyoritsu Bank in central Japan remained out of service as of Monday morning. Transport company Yamato Transport Co. saw its system for confirming deliveries disrupted, while drivers using Toyota Motor Corp.'s connected-car service were unable to reach a call center or do other tasks.

    The Japan Meteorological Agency's weather data transmission remained partially inoperative as of 8 a.m. even as a typhoon approaches Japan, although the agency said it does not have any significant impact on its weather forecast work.

    The problem also affected the carrier's low-cost UQ Mobile brand and its lower-priced "povo" mobile customers, as well as smaller rivals leasing connections from the company, such as Rakuten Mobile Inc.

    The network failure occurred while the switching system for voice calls was replaced during regular maintenance, with repair work triggering a concentration of traffic that led the company to reduce user access.

    During that time, the carrier experienced a cascade of technical problems that further prolonged the connection difficulties.

    Internal Affairs and Communications Minister Yasushi Kaneko said Sunday he believes the disruption should be classified as a "serious incident." This requires a carrier to report details of the problem and relevant preventive measures.

    KDDI President Makoto Takahashi apologized for the disruption at a press conference Sunday, admitting it was the largest outage in its corporate history. The carrier is considering compensating individual and corporate users, he added.

    The latest service outage follows a system failure at NTT Docomo Inc., Japan's largest mobile carrier, in October last year that lasted around 29 hours and affected at least 12.9 million users.

    SoftBank Corp., the country's third-largest mobile carrier, in December 2018 also suffered an outage that affected around 30.6 million users.

    KDDI shares fell during Monday trading on the Tokyo Stock Exchange, ending the day down 1.7 percent at 4,241 yen after dropping as much as nearly 4 percent.

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