The head of mobile phone operator O2 has apologised to customers who were unable to make calls after the group's network was swamped by people using smartphones, it was reported today.
Ronan Dunne said he was disappointed with the group's network performance in London since the summer, according to the Financial Times.
But the group said the situation improved during December after it invested £30 million in improving the network capability.
O2 experienced network problems in London during the second half of 2009 as customers with smartphones, such as Apple's iPhone, increased their use of applications that repeatedly pull data off the internet at short intervals.
Some O2 customers in the capital were sometimes unable to make or receive calls or download data because the network had become clogged up.
Mr Dunne said the difficulties had been caused by an "explosion" of demand for data services on smartphones, although the problems were restricted to London.
The group said data traffic across the UK was doubling every four months, adding that watching a typical YouTube video through a smartphone used the network equivalent of sending 500,000 texts.
Mr Dunne said: "Where we haven't met our own high standards, then there's no question, we apologise to customers for that fact. But it would be wrong to say O2 has failed its customers en masse."
He added that the "short-term blip" in O2's network operations was being address by three separate solutions.
The group has been working with its infrastructure supplier Nokia Siemens Networks on software modifications that will ensure it can better manage the combination of voice and data traffic on its network.
It has installed 200 additional mobile base stations in London to increase the traffic load the network can bear.
It is also working with handset manufacturers, including Apple and Research in Motion, the group behind the BlackBerry, to learn more about applications that could place heavy demands on its network.
O2 is the UK's largest mobile phone operator, with 21 million customers.
The UK's second largest mobile phone operator Vodafone has claimed its network can cope far better with the rapidly increasing number of smartphones.
It is thought network quality will become a key battleground among mobile operators.