Seven bidders for the auction of bandwidth for 4G mobile broadband services have been named by Ofcom.The bidders are Everything Everywhere, BT, Vodafone, O2 and Three, as well as Hong Kong conglomerate PCCW and UK network supplier MLL Telecom.

the auction would increase the amount of airwave available for mobiles by more than 75%.The auction is due to start next month, with licences granted by March and services launching in May and June.

The complete list of bidders is:

• Everything Everywhere (EE), which has already been permitted to launch the UK's first 4G service using existing bandwidth and did so on 30 October
• PCCW, a major Hong Kong telecoms conglomerate, operating through its subsidiary HKT
  
• Hutchison Whampoa, another Hong Kong conglomerate and operator of the 3 network
• MLL Telecom, a telecom network supplier founded in 1992 and based in Marlow, Buckinghamshire
• BT, via its subsidiary "Niche Spectrum Ventures"
• Telefonica, the Spanish incumbent telecoms company that owns the O2 network
• Vodafone
  

"New 4G services will stimulate investment, growth and innovation in the UK, and deliver significant benefits to consumers in terms of better, faster and more reliable mobile broadband connections," said Ed Richards, Ofcom's chief executive.

Ofcom aims to award licences to at least four "credible national wholesalers of mobile services".The auction aims to raise £3.5bn for government coffers - far less than the £22bn raised by the auction of 3G space, which was held at the height of the dotcom bubble in 2000Penetrating buildingsThe auction is making use of the 800MHz radio spectrum freed up by the switch from analogue to digital television, and also offers an additional higher-frequency 2.6GHz band.

Ultra-high frequencies - between 300MHz and 3GHz - are seen as a sweet-spot for mobile communications, as they combine acceptable signal range with adequate capacity for high data transmission, such as in the case of video streaming.Lower frequency radio waves travel further and penetrate buildings more easily, and are seen as better suited to rural areas.

The higher frequency band is better able to cope with heavy data transmission, and is seen as preferable in urban areas, although its more restricted reception area means that operators may need to set up more masts, including inside some public buildings.EE, which was formed from the merger of Orange and T-Mobile in the UK, is said to be taking part so that it can gain additional frequency bands to expand its recently-launched 4G service.

The EE network has made use of old 2G - non-broadband - 1.8GHz bandwidth, that the merged network inherited from its two predecessors, after being given a special dispensation from Ofcom in August.However, the network has been criticised for be patchy and unreliable. One test conducted in Manchester found that just 40% of tested locations got 4G reception from EE.

More 4G capacity will become available in the coming years.Earlier this month, the Ministry of Defence said that it would also auction off even higher frequency bandwidth - up to 15GHz - that it owns, but not until 2014.Meanwhile, a ruling by the European Union requires Ofcom to permit operators to switch existing 3G bandwidth they currently control over to 4G.The additional bandwidth is useful to operators, as individual 4G services take up a bigger chunk of spectrum than earlier mobile telephony, although 4G is also more versatile in the range of bandwidths that it can operate within.