12.05.2012 04:50 AM
Germany pushes for digital terrestrial DVB-T2 upgrade

Germany is preparing to migrate to the second-generation DVB-T2 digital terrestrial architecture, following the lead of the UK, Italy, Finland and Sweden.

The country’s Conference of Directors of the media authorities (Direktorenkonferenz der Landesmedienanstalten — DLM), which effectively controls licensing and technology choices for commercial radio and TV, has called for preparations to upgrade Germany’s digital terrestrial television network to DVB-T2. This move comes just after ARD, Germany’s regional public-service broadcaster consortium, announced its transition to DVB-T2 beginning in 2016.

This will affect the 4 million Germany households that currently receive terrestrial TV via the first-generation DVB-T standard, particularly the 2 million of those for which it is the primary means of TV reception. DVB-T2 has about 66-percent greater capacity than DVB-T, enabling delivery of 5-6 HDTV channels using MPEG-4 compression as required by the standard. Several technical advances have been combined to deliver this increased throughput, one being notably improved Forward Error Correction (FEC) to increase the number of digital bits that can be carried over a given symbol modulated onto the carrier wave. Another improvement is in shortening the guard interval that protects against interference from echoes and progagation delays from 1/32 to 1/128 of the symbol period. This liberates a bit of spectrum for data.

There is scope for achieving even further performance gains as broadcasters or terrestrial distributors get to grips with some of DVB-T2’s more arcane features, such as spreading a large multiplex of signals across several linked frequencies. This will increase the savings that can be achieved by statistical multiplexing through having more channels in the mix. As the number of channels increases, the less headroom has to be allowed to cater for the ever-more remote possibility that nearly all channels will be consuming peak bandwidth at precisely the same time.

Yet from Germany’s point of view, an equally big attraction of DVB-T2 is its increased robustness against difficult propagation conditions, which makes it suitable for delivering mobile TV. Germany was one of the first to deploy DVB-T services initially, but this failed to translate immediately into tangible benefits for viewers, such as HDTV, for various reasons. Then, Germany was also a pioneer of DVB-H for mobile TV services, but it abandoned this in common with other European countries that had adopted the standard when it turned out it would cost too much because it required deployment of a completely new network infrastructure.

This left Germany scratching around for a new mobile-TV strategy, which now seems to be DVB-T2 since the technology has pulled off a neat trick by being capable of being optimized for both HDTV and lower-bandwidth mobile services at the same time. This has been made possible by introduction of a feature called MPLP (Multiple Physical Layer Pipes), which effectively means that the terrestrial infrastructure can provide several virtual physical layers, each supporting different QoS classes.

One such layer can be optimized for delivering HD to fixed antennae, where the requirement is for high bandwidth but with tolerance for low robustness. Another layer can be for delivery to moving smart phones, where bandwidth can be traded off for the high robustness needed. Yet another layer can be optimized for indoor reception.

Germany has also added some features of its own to optimize DVB-T for mobile reception, with its DVB-T ‘handover’ technology having been tested by the country’s Deutsche TV Platform for reception by terminals in cars. There was a pilot held in 2011 organized by the German TV Platform in cooperation with IRT (the technology institute of the German public broadcasters), Hessischer Rundfunk (HR) and BMW (on behalf of the Association of the Automotive Industry, VDA).

A move to DVB-T2 would dovetail with this handover technology to enable even more reliable mobile services for in car reception.



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