Vodafone wrapped ads around British national newspapers on Friday touting the quality of its network ahead of rival EE's launch of next-generation 4G services next week.
The campaign, in The Daily Telegraph, The Independent and The Guardian nationals and in the Metro and City AM freesheets, cost more than 4.5 million pounds, according to a source close to the company.
It will be supported by outdoor advertising.
Since the arrival of smartphones, network quality has come to the fore as a point of differentiation between telecom operators, both in Britain and in other markets, according to analyst Thomas Wehmeier at Informa Telecoms and Media.
"All of these fancy devices that customers have, whether smartphone or tablets, simply don't work unless you have a decent level of connectivity," he said.
He said there had been little difference in network quality between UK operators but this would change with the arrival of 4G.
"The transition to 4G is significant because it opens the door for somebody to establish a beachhead as the UK's biggest and best 4G operator," he said.
EE, jointly owned by France Telecom and Deutsche Telekom, will launch Britain's first 4G network on Tuesday, offering five times faster connections than 3G.
It will be supported by a campaign costing tens of millions of pounds fronted by film actor Kevin Bacon.
Vodafone, as well as Telefonica's O2 and Three, must wait until next year to launch their own 4G services once they have obtained the necessary spectrum.
Wehmeier said Vodafone's campaign was a defensive move to stop customers who are willing to pay a premium for 4G defecting to EE.
"Those four to five months really are going to give EE a chance to attract a very interesting segment of customers," he said.
(Reporting by Paul Sandle; Editing by David Cowell)