Mobile Phone Technology

O2 is one of the 3 UK mobile phone operators in the UK. It is owned by Virgin Media, under the VirginMedia-O2 brand. O2 is the smallest of the UK operators with 26% of the market share. This includes the customers of Virgin Media Mobile as well as the O2 customers.

O2 has a number of available frequencies including 800MHz for 4G; 700 and 3.4-3.8GHz for 5G. Plus they have some mid range frequencies (1800MHz, 2100MHz) that they use for 4G or 5G and was re-farmed from 2G and 3G. Currently (2025-12-31) O2 still operate some 3G communications but this will be switched off very soon for consumers.

O2 is one of the two original mobile operators in the UK, called CellNet originally and owned by BT at the time. They ran a 1G analogue network throughout the UK. On the release of the digital 2G network, Cellnet were one of the 4 mobile network operators. The network was later sold to Telefonica who changed the name to O2. O2 were also part of the 3G auction and were one of the four 3G operators in the UK to be allocated a 3G contract.

O2 also run a significant 4G network over the whole of the UK. Over the years, due to various spectrum auctions and OfCom allocations, O2 have accumulated a lot of frequency over a number of spectrum areas. Perhaps because of this O2 did not purchase any of the 2.6MHz frequency with which to run their 4G network. But as part of the latest 5G auctions purchased some spectrum within 2.3MHz to expand their 4G capacity.

Within the 5G auction they purchased spectrum at 3.4GHz and 3.6GHz to provide 5G capacity as well as 700MHz to provide the 5G coverage. Subsequent to the auction and some moving about of frequency, O2 have a continuous block of 80MHz for 5G use. O2 was the last to switch on a 5G network, but now have a "full" 5G service throughout the UK. Uniquely amongst the mobile operators O2 did not have a significant exposure to Chinese (Huawei and ZTE) equipment and were not exposed to the cost nor the delays caused by the removal of this equipment from the network.

Recently the O2 network was sold to Virgin Media creating the VirginMedia-O2 brand. Under the ownership of Virgin Media, O2 are part of an organisation that has a significant digital entertainment offering as well as their own broadband, with their own fibre in the streets as well as being a mobile operator. Due to the range of offering VirginMedia-O2 is a direct competitor to BT/EE

O2 have a large online and retail presence selling mobile phones, and other online devices, that can be attached to their network.