Tag Archives: T2-Lite

Danish T2-Lite trial goes for all-mobile channel offer

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.”

IBC 2011 – DVB hopeful ‘T2-Lite’ will do better than DVB-H

Europe’s digital TV standards body, DVB, has formally unveiled its new ‘T2 Lite’ profile, designed to provide a subset of the full DVB-T2 specification which is optimised for mobiles and handheld devices.

DVB is hoping it will succeed where the first-generation mobile broadcast standard DVB-H failed, in part because – in the words of chairman Phil Laven – “mobile operators are going to have a serious problem of congestion on their networks” if video consumption on mobile devices continues to increase at current rates.

But Laven also pointed out that the new stripped-down, rugged profile allows the technology to be easily tested in the marketplace, because it can be integrated into a DVB-T2 multiplex without the need to build a dedicated network. This potentially makes its use more cost-effective than DVB-H.

BBC R&D experiments have shown that using a DVB-T2 multiplex normally carrying 40.2MBit/s (as in the UK Freeview HD profile), a T2 Lite channel could be squeezed into a 1.02MBit/s stream, with the DVB-T2 channels taking up the remaining 33.6MBit/s (the loss of 5-6 MBit/s is explained by the extra capacity devoted to making T2 Lite more robust).

Peter Siebert, DVB’s project director, promised that “very soon, all [DVB-] T2 chipsets will support T2 Lite.”

‘T2-Lite’: a new candidate for mobile broadcasting

European digital TV standards body DVB has introduced a new, slimmed-down profile as part of the latest version of its next-generation DVB-T2 standard, targeting ‘low-capacity’ applications such as mobile broadcasting.
Known as ‘T2-Lite’, the new profile avoids processing- and memory-heavy modes, allowing more efficient receiver designs to be used – e.g. for a DVB-T2 tuner in a smartphone or tablet.
T2-Lite is limited to a maximum bit-rate of 4MBit/s, whereas the full HD-centric profile can run up to 48MBit/s (in the UK, DVB-T2 uses around 40MBit/s for DTT HD – see here.)
DVB says that “One possible use for T2-Lite enables the simulcasting of two different versions of the same service, with different bit-rates and levels of protection, which would allow better reception in fringe areas.”
According to a post on the BBC’s R&D blog, the BBC has been testing T2-Lite since July 7. In the trial, an HD signal for fixed reception and a T2-Lite version are combined within a single multiplex, with the T2-Lite frames placed in the gaps between the HD ones.
The concept that a single DVB signal could contain different versions of a broadcast which could be extracted by different receivers with different capabilities was proposed by the ‘god-father’ of DVB, Prof Ulrich Reimers, when DVB was originally set up, but has yet to prove popular in practice.
The BBC solution will be demonstrated at the forthcoming IBC exhibition in Amsterdam.