Japan's major mobile phone carriers agreed at a government panel meeting on Wednesday that they need to introduce roaming capabilities so their customers can use rival networks during service disruptions.
With the carriers warming to the idea following a recent widespread outage affecting one of them, a communications ministry panel of experts will advance discussions on the issue with a view to implementing the proposal from around 2025.
In early July, KDDI Corp. suffered a network outage that lasted over 60 hours, affecting at least 30.91 million people, with users unable to make emergency calls for an extended period.
While NTT Docomo Inc., SoftBank Corp., "au"-brand operator KDDI and Rakuten Mobile Inc. were unanimous at the first expert meeting on the need for a framework for roaming support in emergencies, there was disagreement on what form it should take.
The points of contention include whether the functionality should be limited to using emergency service numbers like 119 or widened to standard calls and whether it will come at a cost to users.
While KDDI and Rakuten Mobile maintained that standard voice communications should be part of the roaming service, Docomo expressed concern that it would place the onus on the network that is receiving an influx of users to provide a stable service.
Conversely, SoftBank put forward that it is realistic to offer roaming only for emergency contact services and cited dual-SIM phones as one example of other approaches that should be considered.
About 60 percent of Japan's emergency calls are now made by mobile phone, the meeting heard.
Reports emerged from the KDDI disruption of people with emergency health issues being unable to directly contact their local fire station and having to physically go to them, among other life-threatening cases.
KDDI was formally ordered by the communications ministry in August to do more to prevent another outage on the same scale.