O2 supplier Ericsson has said it is working with the mobile network to identify the outage which has left O2 customers unable to make phone calls, send SMS or access the Internet.
The downtime, which began at 13:30 yesterday, has so far been attributed to "a fault with one of our network systems " by O2, meaning that its customers were unable to correctly register mobile phone numbers with the network.
"The fault is not related to signal strength or network availability from our mobile masts, which is why phones may still be showing full signal," O2 said in an explanatory blog post. "The fault is due to a problem with a network system, which works to register specific mobile phone numbers to the network."
Sources told Information Age that the fault was in a core network element called the home location registry (HLR). BBC news also reported that a fault in O2’s HLR was responsible for the outage.
A set of documents describing Oracle’s mobile subscriber services from 2007 lists Ericsson and Nortel Networks as the providers of O2’s HLR at the time, although Nortel has since been liquidated. An Ericsson spokesperson couldn’t confirm whether the company still provides O2’s HLR, but did say that the company is a key supplier to O2.
"We have been working with [O2] to identify the original cause of the fault and take the necessary actions to ensure the service provided is restored as quickly as possible," an Ericsson spokesperson said.
This morning, O2 said that it had been working "through the night" with its "central supplier" to fix the issue, announcing that it had restored voice and SMS service for all customers at 8am. O2 said that it had extensive continuity plans which had been "brought into effect to restore service as quickly as we could".
Various parts of O2’s network are managed by companies such as Eriksson, Nokia Siemens Networks (NSN) and Huawei.
In May, Chinese communications company Huawei signed a five year deal to manage O2’s core mobile network. However, spokespeople from O2 and Huawei said that the outage was not related to Huawei’s work.
"The managed service contract we won recently is to design and plan O2’s future network and we are not managing O2’s current network," Huawei said in a statement. "However, we are ready to offer support if requested by O2."
An NSN spokesperson declined to comment and directed Information Age to the O2 press office.