UK regulator Ofcom kicked off a long-awaited spectrum auction which sees five bidders vying for frequencies designed to bolster the country’s existing 4G networks and prepare future 5G services.

Ofcom confirmed in a statement the auction was now underway, with a total of 190MHz of spectrum available in two frequency bands.

The first band, 2.3GHz, can be used by companies as soon as it is released, to “increase broadband capacity for today’s mobile users”. The second, 3.4GHz, cannot be used by today’s mobile devices, but “is earmarked for 5G”.

In total, 40MHz of spectrum is available in the 2.3GHz and 150MHz in the 3.4GHz

The auction will see the five companies – EE, Vodafone UK, O2 UK, 3 UK and SoftBank-backed venture Airspan Spectrum Holdings – bid for spectrum lots over a series of rounds: the process could take a number of weeks, depending on the level of demand from bidders.

A sixth company, regional wireless broadband provider Connexin, was expected to take part but pulled out of the process last week.

The auction was supposed to be held in 2017, but was delayed by legal challenges from 3 and EE. Both operators argued against caps being imposed on the amount of spectrum a single operator could hold. Market leader EE argued against having a cap at all, while 3 fought for an increase to the cap to address competition concerns.

Courts ruled in favour of Ofcom in December 2017 and 3’s appeal against the decision was rejected last month, clearing the way for the regulator to launch the auction.

Ofcom added its duty during the auction will be to “manage the use of spectrum efficiently, rather than maximise the financial value of the auction”.

The regulator also outlined the two caps in place. EE, which currently holds the most spectrum, will not be able to bid for any spectrum in the 2.3GHz band, and a second limit relates to an overall cap on how much a single company can hold after the auction.

Philip Marnick, Ofcom’s spectrum group director, said the regulator wants to see the spectrum “in use as soon as possible.”

“We are glad the auction is now underway”, he added.