The telecoms regulator will auction off 40 MHz of spectrum within the 2.3 GHz band to support immediate delivery of 4G services and a further 150 MHz in the 3.4 GHz band for future 5G services.
Six companies were previously announced as having made successful applications to bid in the auctions. The big four mobile network operators (MNOs) in the UK, EE, O2, Three and Vodafone, as well as from Airspan Spectrum Holdings and Connexin, are those eligible to bid, although caps that Ofcom has imposed limit the amount of spectrum that EE and Vodafone will be able to acquire.
According to Ofcom, the outcome of the spectrum auctions may not be known for "a number of weeks".
Last week, Ofcom separately announced further plans for its intended auctioning off of spectrum in the 700 MHz band, scheduled for the second half of 2019.
The regulator has proposed requiring successful bidders in that auction to improve the coverage of their 4G services. It described the proposed auction as "an important opportunity to improve coverage". Competition alone will not drive the improved coverage it seeks, it said.
Ofcom said: "To ensure widespread improvements in mobile coverage across the UK, we are proposing to attach coverage obligations to some of the licences we will award for the 700 MHz band. These obligations will require winning bidders to roll out improved mobile coverage in rural areas and the nations. "
Ofcom's consultation is open until 4 May.