NTT DoCoMo Inc. said Thursday that the disruption of texting and mobile phone services the previous day happened because its packet-switching equipment doesn’t have enough capacity to handle the data traffic generated by smartphones.
The telecoms giant admitted to miscalculating the surge in data traffic that could be expected from smartphone users.
“Our estimate (of the communication volume) was insufficient . . . We apologize to our subscribers for causing the trouble,” DoCoMo Executive Vice President Fumio Iwasaki told a news conference.
Wednesday’s service collapse coincided with a major disruption in rail service that brought the Yamanote, Chuo and Sobu lines — Tokyo’s main commuter backbones — and other train lines to a halt for about an hour, triggering a flood of calls and email from delayed passengers.
DoCoMo said it will conduct a nationwide check of its 200 or so packet-switchers by mid-February.
DoCoMo estimated the volume generated by smartphones would reach about 12 million signals per hour. Although the packet-switchers are capable of processing 14.1 million signals an hour, volume actually swelled to 16.5 million Wednesday, overwhelming the equipment and causing the outage.
The problem started at around 8.30 a.m. and ended about five hours later, affecting 2.52 million subscribers.
At the time, the carrier was replacing equipment to boost processing capability to deal with the surge in smartphone use.
The Internal Affairs and Communications Ministry told DoCoMo to find the cause of the outage because it has had repeated trouble since last August, despite efforts to increase capacity.
The outage was exacerbated by the disruption to East Japan Railway Co.’s train services in the capital that occurred after a train driver spotted smoke on a bridge between Shinjuku and Shin-Okubo stations.
In a related development, KDDI Corp. said Thursday that its telecom services also were disrupted from 11:33 p.m. Wednesday to 3:03 a.m. Thursday in western Tokyo, affecting about 72,000 land lines.
KDDI said it is trying to ascertain how many users of its au mobile phone service were affected by the disruption.