KDDI network disruptions continue to affect mobile service “at”

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

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

Internet and data communications services have been ‘largely restored’, but ‘au’ mobile phone users are still struggling to make calls due to a temporary limit imposed on network traffic, according to the second mobile phone operator in the country by subscribers.

The operator had no firm timetable set for the restoration of full service from 11:30 a.m.

The disruption, which occurred around 1.35am on Saturday, affected up to 39.15 million mobile connections and disrupted banking systems, weather data transmission, package deliveries and cars connected to the network.

Speaking at a press conference on Monday, Deputy Chief Cabinet Secretary Seiji Kihara said the issue was “extremely regrettable” as mobile networks are an important infrastructure for the public and their businesses, and that he demanded a “thorough explanation for users” from the carrier.

KDDI’s problems come at a time when the government is making digitization one of its top priorities. It also highlights the risk of a large-scale communications blackout, as everything from cars to factory equipment is connected to the internet.

Some ATMs at Ogaki Kyoritsu Bank in central Japan remained out of service on Monday morning. Transport company Yamato Transport Co. has seen its delivery confirmation system disrupted, while drivers using Toyota Motor Corp.’s connected car service. were unable to reach a call center or perform other tasks.

The Japan Meteorological Agency’s weather data transmission remained partially inoperable at 8 a.m. even as a typhoon approached Japan, although the agency said it had no significant impact on its weather forecasting work.

The issue also affected the carrier’s low-cost UQ Mobile brand and its low-cost “povo” mobile customers, as well as smaller rivals leasing connections to the company, such as Rakuten Mobile Inc.

The network outage occurred as the switching system for voice calls was being replaced during regular maintenance, with repair work causing a concentration of traffic which led the company to reduce user access.

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

Internal Affairs and Communications Minister Yasushi Kaneko said on Sunday he believed the disruption should be classified as a “serious incident”. This obliges a carrier to report the details of the problem and the relevant preventive measures.

KDDI Chairman Makoto Takahashi apologized for the disruption at a press conference on Sunday, admitting it was the biggest outage in its history. The carrier plans to compensate individual and business users, he added.

The latest outage follows a system failure at NTT Docomo Inc., Japan’s largest mobile operator, in October last year that lasted about 29 hours and affected at least 12.9 million of users.

SoftBank Corp., the country’s third-largest mobile operator, also suffered an outage in December 2018 that affected about 30.6 million users.

Shares of KDDI fell on the Tokyo Stock Exchange on Monday, ending the day down 1.7% at 4,241 yen after falling nearly 4%.

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