LONDON British mobile operator O2 said it had resumed full service on Thursday, 24 hours after a third of customers were hit by a network failure that raised concern about how it will cope with a jump in demand during the London Olympics later this month.
O2, owned by Spain's Telefonica, said it restored its 2G network, enabling customers to make and receive calls, early in the day and took a few more hours to fix its 3G network.
"Following previous updates, our tests now show that all our 2G and 3G services have been fully restored for affected customers," the company said.
The problem had started when some O2 customers found difficulty making or receiving calls, sending texts or using data.
"It was a fault with one of our network systems which has meant some mobile phone numbers are not registering correctly on our network," said a spokesman for the company, which has 23 million British users.
More than 7.5 million customers were affected, although the outage did not hit all users at the same time or in the same location, a spokesman said.
The disruption was more severe than the company had earlier estimated and also had an impact on mobile services provided by retailer Tesco and GiffGaff, another O2 brand, both of which use the O2 network.
"The first priority is finding the root cause of the outage and making sure it does not happen again," the spokesman said. "The second step, once we established what went wrong, is to make it up to our customers."
Britain's mobile networks will come under pressure in the next few weeks from visitors to the Olympic Games, many of whom will be wielding smartphones to take and send pictures and video and to access the Internet.
O2 has been subcontracted by BT, the official Olympics communications supplier, to provide mobile services within the Olympic Village.
Analyst Steven Hartley at Ovum Telecoms Strategy said the outage raised concerns about the Olympics' impact on Britain's telecoms infrastructure.
"The huge influx of visitors to London ... will cause network traffic spikes, putting pressure on the UK's mobile networks," Hartley said. "While UK mobile operators claim to be prepared, they have not yet given indication of the scale of their plans."
Hartley added that while mobile capacity upgrades at key transport and crowd hotspots would undoubtedly take place before the Games, an unexpected spike in demand at less well-prepared peripheral sites could prove disastrous.
O2's outage came just days after France suffered its biggest telecommunications failure since 2004, prompting a call from the government for an audit of key nation telecoms infrastructure.
Some 26 million France Telecom customers were left with no service for 10 hours over the weekend after an overload occurred on Alcatel-Lucent equipment two days after a software update was carried out.
The bug also disrupted the network's ability to locate and identify customers as they made calls, which was similar to the problem that hit O2.
An Alcatel-Lucent spokesman said its equipment was not involved in the O2 outage. Ericsson said it had helped O2 to recover, but it declined to comment on whether its equipment was to blame.
"We have been working with the customer through the night to get the network back up," said an Ericsson spokeswoman.
Bengt Nordstrom, CEO and co-founder of telecommunications management consultancy Northstream, said outages happened from time to time in all networks.
Nordstrom said it was difficult to draw any conclusions at this stage, but added that network quality in Britain and France was not great compared with the Nordics.
"Some of that can be explained by the difficulty for the operators, in the UK and France, and Germany for that matter, to get sites (for mobile transmitters)," Nordstrom said.
Mobile operators were also trying to keep investors happy by keeping a lid on capital spending, he said. "(Analysts) are looking at how much operators are investing in networks, and most of them don't like that figure to be too high."
(Additional reporting by Stephen Mangan, Tarmo Virki and Leila Abboud; Editing by Sophie Walker)