TOKYO Kyodo KDDI Corp. said Monday that voice and data communications have been restored nationwide after the Japanese telecom giant has suffered disruptions on up to 39 million mobile connections during maintenance work.
Users of its au mobile phones were having difficulty making calls Monday due to a temporary limit on network traffic, even after internet and data communication services were largely restored.
The disruption happened around 1: 35 a.m. Saturday and affected up to 39.15 million mobile connections, disrupted banking systems, the transmission of weather data, parcel deliveries and network-connected cars.
Deputy Chief Cabinet Secretary Seiji Kihara said at a press conference on Monday that the problem is extremely regrettable as mobile networks are important infrastructure for the public and their activities, and he has demanded an in-depth explanation for users from the carrier.
The government is pushing for digitalization as one of its top priorities, and KDDI's problems come at a time when it is pressing 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 the Ogaki Kyoritsu Bank in central Japan were out of service on Monday morning. Yamato Transport Co. saw its system for confirming deliveries disrupted, while drivers using Toyota Motor Corp. s connected-car service could not reach a call center or other tasks.
The Japan Meteorological Agency said it did not have a significant impact on its weather forecast work as of 8 a.m. even though a typhoon approached Japan.
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 switch 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.
The carrier experienced a cascade of technical problems that further prolonged the connection difficulties during that time.
Internal Affairs and Communications Minister Yasushi Kaneko believes that the disruption should be classified as a serious incident. It 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 on Sunday, admitting it was the largest outage in its corporate history. He said that the carrier is considering compensating individual and corporate users.
The latest service outage comes after a system failure at NTT Docomo Inc. Japan's largest mobile carrier, in October last year, that lasted around 29 hours and affected 12.9 million users.
SoftBank Corp., the country's third largest mobile carrier, suffered an outage in December 2018 that affected around 30.6 million users.
KDDI shares fell by 1.7 percent to 4,241 yen on the Tokyo Stock Exchange, after dropping as much as 4 percent during Monday trading.