Details have emerged about some of the technology choices adopted for the Copenhagen ‘T2-Lite’ trial, for which Danish operator Open Channel was awarded a licence in August last year.
The trial, which launched on January 1st this year and could run for up to three years, uses UHF channel 39 in Copenhagen, and claims coverage of more than 700,000 households.
In contrast to the BBC R&D trial last year, which squeezed a T2-Lite channel designed for mobile reception into the gaps between a fully-fledged HD service transmitted in standard DVB-T2 mode (now dubbed ‘T2-base’), the Copenhagen trial consists entirely of T2-Lite TV and radio channels carried on up to 16 Physical Layer Pipes (PLPs). As their name suggests, each of these can be regarded as a separate data-pipe with its own bit-rate and robustness characteristics, a notable feature of the second-generation DVB DTT standard.
Open Channel’s calculations show that configured in this manner, a T2-Lite multiplex can match the data-rate offered by a DVB-T one (see table below), yet still offer good mobile reception (unlike DVB-T as generally configured).
|Stationary reception||DVB-T||20 – 22 Mbit/s||DVB-T2||37 – 40 Mbit/s|
|Mobile reception||DVB-H||10 – 13 Mbit/s||DVB-T2 Lite||20 – 25 Mbit/s|
Source: Open Channel
The difference between the T2-base multiplex data-rate (40.2 Mbit/s in the UK) and that of a T2-Lite mux (20-25 Mbit/s) is explained by the fact that the PLPs within it are configured to be much more robust for mobile reception purposes, so run at lower bit-rates (the DVB-T2 spec sets a maximum of 4MBit/s for PLPs when T2-Lite is used).
But that in turn means that they can easily be captured by fixed aerials, too: in other words, the same channel offer is receivable on either living-room displays fed from a fixed rooftop antenna or handheld devices equipped with a T2-Lite tuner (the DVB predicted last September that soon, all [DVB-] T2 chipsets will support T2 Lite).
These channels will, of course, not be HD quality, but that has to be set against the fact that no separate (expensive) mobile TV network needs to be constructed.
One of the interesting assertions made by Open Channel is that DVB-T2 Lite is not only suitable for mobile TV. It is, the company says, “also highly suitable as the future standard of digital radio in place of DAB & DAB+ [...]. With the DVB-T2 / T2 Lite profile you get 2.7 to 3.7Mbit/s capacity (~ 40 / ~ 55 HE AACv2 radio stations) compared to the DAB / DAB+ 1.1 Mbit/s capacity (~ 6 mpeg1 layer II / ~ 16 HE AACv2 radio stations) with the same propagation model.”