Digital terrestrial TV (DTT) in the UK will get a technology upgrade which will allow more channels and high definition (HD) broadcasts, if a proposal by communications regulator Ofcom gets the go-ahead.

Ofcom said the upgrade could allow HD TV on Freeview "as early as 2009" and "by making better use of the valuable spectrum reserved for broadcasting could bring benefits worth £4bn to £6bn to the UK economy over 25 years".

The upgrades would mean changing the coding standard used for DTT from MPEG2 to MPEG4, which is claimed to be twice as efficient. It would also mean using the DVB-T2 European transmission standard which should increase capacity by at least 30 per cent.

The plan is to clear one of the multiplexes by moving the TV broadcasts it carries to spare capacity in another multiplex, and then upgrade it to use the new technologies and standards.

It was previously feared that a change to MPEG4 would mean the MPEG2 signal being switched off, making current DTT boxes obsolete. This proposal means MPEG2 signals will still be transmitted and users will be able to receive the existing Freeview services.

However, in order to receive the upgraded services, users will have to purchase a DTT set-top box or TV which is compatible with MPEG4 and DVB-T2.

Ofcom said the technology changes "could in time more than double the capacity of DTT".

The four terrestrial broadcasters, BBC, ITV, Channel 4 and Five, recently agreed on providing HD channels on Freeview by 2012, with the potential for channels starting between late 2009 to early 2010.