Noises that recently came out of DVB Project executive director Peter MacAvock saying that DVB-T2 would be ‘groundbreaking’ can offer little comfort to anyone considering a double, triple or quadruple play right now.
The effect on IPTV by DVB-T take up across Europe has been at the very least negative, and in some cases, notably in the UK where BT felt it couldn’t launch a multicast IPTV service at all, downright off putting.
Alarms should have gone up in April when the first call for technologies went up, but at IBC and in other speeches, MacAvock has been heard saying that the system will be groundbreaking. For groundbreaking you might want to read ‘disruptive’ if you happen to be working in any other video technology.
The clues are all in the specification that was released at the time of the call for technologies, but this drew scant notice from the world’s technical press and we thought that perhaps it needs another look.
The framework says that technologies should offer 30% better propagation distances, 30% improvement in the amount of data that it will carry in any given situation and that it should cover MIMO (multiple antenna or spectral diversity capability) offer flexible multiplexing to including ‘burst’ multiplexes which are time interleaved, so as to allow mobile TV (oh no, not another mobile TV technology) and use the lightweight LDPC FEC coding scheme used in DVB-S2 the update to the satellite DTH standard.
MacAvock is cited by EE Times this week saying that any technology might be considered, even China’s DMB-TH as the DVB Project looks at everything from spread spectrum, single carrier and OFDM multiplexes which go beyond the 8K used in DVB-T.
The DVB logic is that it gets one chance at re-engineering the global TV spectrum, and when the bidding starts for any UHF spectrum freed up by taking TV digital, DVB needs to be in good shape to help broadcasters.
Thinking about this there’s a lot to what he is saying. The world wants High Definition TV to come over terrestrial networks, whether this is free to air or paid or a combination. When DVB-T was being specified over ten years ago there was little thought given to multi-mode transmissions where HD signals, multiple SD signals and also multiple ‘burst’ mobile TV signals, could all be sent in one 8 MHz or smaller channel. For one thing mobile TV had not settled, or come close to settling, on a standard, and HD signals were being thought about as great 15 Mbps MPEG2 signals back then, but the world has changed. Also electronics and antenna technology has changed, and the combination of video fragmentation into multiple markets, improvements in codecs and carrier technologies all points to the potential for vastly different broadcasting networks.
The Japanese ISDB-T standard has shown the way somewhat, and the US ATSC standard has followed this.
Today a 64 QAM modulation with a very small guard interval gives a total throughput to a single 8MHz UHF DVB-T channel of just under 32 Mbps. This can vary down to far slower data rates depending upon climate and geography and what they dictate as a viable modulation scheme, but essentially in Europe, where DVB-T has taken off the usable data rate is around 18 to 24 Mbps. The lower rates are really due to power considerations because digital channels would interfere with analog channels when used at full power, so there is going to be a shift gradually across Europe anyway, with roughly an additional throughput increase of about 30% without adopting DVB-T2, when analog switch off happens. So that’s 32 Mbps for every multiplex. Convert to a new DVB-T2 and it’s up to over 40 usable Mbps per multiplex.
A couple of 5 or 6 Mbps high definition signals, not uncommon in H.264, and perhaps 15 or more 1.5 Mbps Standard Definition signals, would still only take up 32 Mbps, but with modern statistical multiplexing, that could be far lower. That leaves 8 Mbps for mobile channels, enough for a DVB-H style version of every one of the other channels, and all of this in a tiny 8MHz slice of spectrum. Even Cable only has around 1 Gbps to play with and that includes back channels for internet connection etc’ so it would not be long before free to air and paid DVB-T2 services began to offer the same type of channel numbers as a cable system. That immediately damages cable, IPTV, the existing DVB-H method for conducting mobile TV, and will create a potential for multiple hybrid triple plays, using the new system.
In the UK, which was the first commercially successful DVB-T multiplex, there are already 6 multiplexes which currently deliver 64 TV channels, though it could no doubt handle more. The problem for the UK, France, Spain and Italy is that these markets have already seen the take off of DVB-T and there are millions of set tops and antennas in operation. It’s not here that the biggest changes will be seen because of the domestic cost of upgrading rooftop antennas (roughly $150 plus labor to buy and install a completely new type of antenna, as a one off cost). Also set tops mostly don’t use H.264 capable chipsets, so the signals are MPEG2.
So it is the new countries where labor is cheaper and where there has been little in the way of established digital TV that will see huge multiplexes coded in H.264, offering multiple HD channels, numerous SD channels and perhaps adopting the same platform for mobile and portable TV channels, instead of DVB-H.
About 84 countries have trials or services using DVB-T, with more than 30 with live services. At least another 30 are already committed to launching a service while others are still making up their minds.
This makes the reach of DVB-T likely to rise over the coming few years to something over 2 billion people. The rest are either covered by China’s new system, Japan’s ISDB-T, the USA’s ATSC, or they have no digital terrestrial system in place or planned, except perhaps satellite using DVB-S2.
It likely makes the reach of DVB-T2 over half that figure, because in many countries their systems won’t come on line until new equipment is out, which embraces the new standard. So that’s places like India, Indonesia, the Philippines, parts of South America, where this new video effect will hit first and hardest.
We can speculate about the technologies, it might be that 16,000 or 32,000 subcarriers will be used and that 256-QAM modulation will come into play. We already know that the DVB-S2 LDPC (low density parity check) error correction coding is likely to be mandated and highly efficient and the technology request implies MIMO which means new designs of antennas. It also means that one or two of the submissions that DVB receives will go way beyond its minimum target of a 30% hike in data rate, because MIMO has already been shown to be capable of so much more.
Of course it depends just how far DVB wants to go. It won’t want antennas that are too expensive to make, too cumbersome or which need fine adjustments so it’s likely to accept minimal MIMO we expect.
The system will be accepted and ratified before the end of this year, and even with a conservative period for design and manufacturing, should be in operation in its first countries during 2009 which is just in time for newly freed up UHF spectrum.
In our opinion DVB-T2 does two key things. One it will fill the first generation of digital TV multiplexes with far more video than anyone ever anticipated, creating a downturn in pay TV attractiveness and therefore pricing. Second it will create a higher value for spectrum when purchased by a broadcaster, and therefore give a counter offensive to those that believe that all freed up 700 MHz class spectrum will be bought by cellular operators. If broadcasting can attract a similar number of dollars of revenues per MHz as cellular operators can, or just get a lot closer to it, then more channels will go to broadcasters.
Having said that, the DVB-T2 spec once agreed could have the opposite effect. It could shut the mouths of all those people calling for gifted HD spectrum for digital terrestrial TV, and make their need for spectrum less urgent than the cellular community, which desperately needs it for the mobile web.
When 8VSB solutions began appearing in the US, the method of getting better performance out of an ATSC signal, so that it can include a mobile TV version of the stream in existing spectrum, it begged the question of just how broadcaster were going to get portable devices out there that received mobile TV, without the help of the cellular carriers.
This new DVB-T2 system, if it accepts proposals that offer decent mobile reception in bursts (to save battery life on the radio, DVB-H channels are sent in a faster than real time burst and then played out slowly), then it sets up an alternative method for mobile TV that is NOT controlled by cellular operators. There is already a perception that DVB-H is built for broadcasters not cellcos, and that MBMS is a better option for most cellcos. This spec has the potential to create an even greater rift between broadcasters and cellular operators, one that is likely to see them go head to head in the area of mobile TV.