New DTT standard '49% more efficient'

DVB-T2, the new transmission standard that will be used as part of a package of configuration changes designed to permit the carriage of high definition services on Freeview, may yield as much as a 50% capacity enhancement over the existing DVB-T standard, it has emerged.

During the design process, DVB-T2 had been tasked with delivering a minimum 30% capacity enhancement for a multiplex transmitted using DVB-T. However, the specification that was recently approved by the DVB Project - and now successfully tested in Guildford - is mathematically projected to attain a 49% improvement.

Nick Wells, who chairs the DVB TM-T2 Group and is also the acting head of Future Media Research at BBC Research and Innovation, wrote in the DVB Project's magazine DVB-Scene: "T2 is expected to provide a very significant increase in capacity, whilst simultaneously improving the ruggedness of the transmission system.

"Both of these features make it an ideal system for the broadcasting of High Definition television."

The new standard could even lower the cost of transmission by permitting "a reduction in peak amplifier power rating of around 25%".

Ofcom's plans for the future of multiplex B - on which high definition services will be carried - are based on it having a total capacity of close to 30Mbps. DVB Project calculations comparing the 24.1Mbps capacity of a DVB-T multiplex using 64QAM with those achieved by a DVB-T2 multiplex using 256QAM show the capacity of the DVB-T2 channel to increase to 35.9Mbps.

The precise figure has yet to be confirmed by laboratory or field trials; however, the successful development of a DVB-T2 compatible demodulator by BBC Research and Innovation will permit such tests to begin, and it is expected that a demonstration at this year's IBC will confirm the 35.9Mbps figure.