I think the point you make about DMB as a technology is entirely valid, but you haven’t considered the existing roll-out of DVB-T (and T2) and DAB in the UK.

Both of the national DAB multiplexes are full. This is good news for radio, which is exactly what they were rolled out to carry. The commercial mobile TV service on Digital One peaked with around, I think I’m right in saying, around 50,000 users. That’s not a technical failure, but it certainly wasn’t a great use of bandwidth on Digital One.

If someone wanted to roll-out a new mobile TV service using Eureka 147, they’d need to build a brand new national multiplex. That gives you a maximum of 1184kb/s to play with at PL3. If you were going to roll-out a new multiplex, DVB-H could be considered as it’s standardised for Band III.

With DVB-T2-Lite, you get 4Mb/s to play with and robust error correction.

It sounds to me like BBC R&D have looked at this idea and developed it based on the reality of the current DVB/DAB roll-outs in the UK.

Despite the lack of chipsets and users of DVB-T2-Lite (well, it has only just been standardised!), that’s no barrier to it’s use. As you said a few weeks ago, DAB’s constantly been poked as it’s “not a global standard”, but it that’s not a very constructive argument against it as a system.

The benefit for DVB-T2-Lite is that DVB-T/T2 is becoming, at least, a continental standard and DVB-T2-Lite is designed to sit within it.

The existing DAB multiplexes are full. But the transmitter network is there, and the coverage is – unlike DVB-T – specifically built for mobile reception in mind. Add another nationwide multiplex for DMB and you’re laughing, because you can simply add another multiplex to the existing transmitter network: one that could do DMB, DAB+ and DAB on the same multiplex. You can also use local multiplexes for local television: in a way that’s impossible using existing digital television transmitters.

DMB already is a continental standard: and is in production in many parts of the world. What does DVB-T fix that DMB hasn’t already?

The DAB family – even DMB – uses some now pretty old error-correction schemes. Ofcom’s recent DAB Coverage Planning consultation includes a document http://stakeholders.ofcom.org.uk/binaries/consultations/dab-coverage-planning/annexes/annex-g.pdf suggesting a carrier-to-noise ratio of 7 dB for a Gaussian channel and 14-15 dB for a Rayleigh channel (no line of sight to transmitter, multiple reflections). The mode that the BBC are using for the ‘mobile’ part of this DVB-T2 trial requires only 0.7 dB in a Gaussian channel and, significantly, only 2.0 dB in a Rayleigh channel. These are the figures to deliver a bit error rate of 10^-7, 1000 times better than the 10^-4 given for DAB. At a spectrum efficiency of 0.87, this should give a raw capacity of 1,479 kbps in 1.7 MHz, similar to the DAB capacity.

DVB-T2 was defined for 1.7 MHz bandwidth specifically in order to fit into nominal DAB allocations in VHF Band III and L-Band, in addition to the 5, 6, 7 and 8 MHz widths used for TV around the world. (They also added a 10 MHz bandwidth for contributions). The 2006 Regional Radio Conference in Geneva agreed that other services could be used in the allocated/assigned frequencies and areas as long as it fits within the bandwidth profile of the service nominally assigned to that frequency – this is the basis for DVB-T2 being allowed in DVB-T assignments!

Predicted received signal level on an ideal half-wave dipole is substantially less for UHF dipoles than for Band III, as the aerial is so much smaller. However, few mobile receivers actually have a sufficiently large aerial – the ideal dipole aerial is around 60cm long for DAB! The active element of UHF aerials is 20-30cm. My knowledge of aerial theory isn’t great, but I’m not sure the difference bears out with a much shorter aerial.

The point of this trial may be to figure out a better way of carrying the national radio stations on Freeview: in their current home, they’re only practical for rooftop reception, while mobile capacity would be possible if moved to a DVB-T2 service set up this way. It does come at the cost of about 20% of the multiplex’s capacity for HD TV services, so it’s unlikely to be done on the current Multiplex B. Channel 5 gets first refusal on any new capacity on that mux (found by increasing compression on the other four services); under Richard Desmond they’re unlikely to turn it down a second time.

Thanks, Mike.

“The DAB family – even DMB – uses some now pretty old error-correction schemes.” – you’re at the limits of my technical knowledge here, but it’s my understanding that while “original DAB”‘s error correction schemes are old, the ones used for DAB+, DMB and DVB-T use additional Reed-Solomon FEC coding to the inner convolutional coding in a similar way. The technical paper I’ve just read talks about 10^-10 to 10^-12. Not sure I fully understand any of it, but I’m not entirely sure the error-correction scheme is particularly important here.

Technically, I don’t doubt that DVB-T2 on Band III would be an interesting idea. But I cannot think of a single practical reason why you’d use that instead of DAB+ on Band III. Given the economies of scale in running one single transmission network for all mobile broadcast media, whether it’s radio or television, surely the Eureka 147 family makes the most amount of sense? It’s tried and tested, and it’s already here. Why do we need another wheel when we’ve already one that works perfectly?

I’ve heard about this technology before. Let’s face it, it can’t be that far away now when you’ll be able to watch TV and listen to radio on the move. Without the use of a Wi-fi hot spot.

Isn’t this already in development though with the 4G network? And doesn’t it have some kind of super download speed? Personally, I think this is the future, people want to access their material on the move, they don’t want to be confined to Wi-fi routers.

What I think will be interesting is how this changes radio, I think the car radio will cease to exist in 10 years and will turn into a kind of in-built music and video portal. Primarily because the technology in phones is far more superior to anything you can now buy at your local Halfords.

I should get my crystal ball out more often.

Peter: “Let’s face it, it can’t be that far away now when you’ll be able to watch TV and listen to radio on the move. Without the use of a Wi-fi hot spot.”

My point is: it’s possible now. Other countries are doing it (the TV bit). We can stick that service live tomorrow: the transmitter network exists, and the receivers already exist (I own one).

A future for radio and television, however, has to have broadcast as its main backbone. Putting everything onto 4G simply won’t work. The coverage won’t be there, it’ll cost ludicrous amounts, it won’t be uncapped, and research in other countries paints a dim picture of using 3G/4G instead of broadcast radio/tv.

Interesting times ahead me thinks James.

However, have the BBC, the big phone operators, ISP’s and commercial TV and radio ever sat down to discuss this.

Let’s be honest, they all play a part but it seems as if they all have their own agenda. First past the post wins kind of mentality – rather than what’s good for the team.

Yes, they do, regularly. Mobile phone operators don’t want the extra traffic, and can’t even cope with it (look at O2 giving every iPhone user free access to BT Openzone and The Cloud for a clear and obvious example).

The BBC iPlayer on mobiles won’t work via 3G because the mobile phone companies have requested it doesn’t.

The future is FM/DAB and IP all playing its part. Leave the millions of users of live TV and radio using broadcast technology: it’s what it was designed for. And EVERYONE – the broadcasters and the mobile phone companies – agree on that point.

Whatever the arguments, citing the bt/microsoft/digital one/virgin mobile DAB tv effort is unfair. The tech was poor owing to the microsoft-centric solution which used windows mobile video in a transport nothing like DMB.

The result was a hopelessly fragile video stream which constantly dropped and buffered on the move. Also it didn’t take me long to realise that watching TV pictures shot for living room sets on a 3″ mobile screen on the bus wasn’t really a worthwhile experience.

The other thing about the Digital One mobile TV service was rights issues between the broadcasters. What you would get on the mobile service would not always resemble what would be broadcast on the ‘usual’ TV channel.

The digital one mobile TV service was also hampered by incredibly low quality video (I think it was only 64 kbit/sec per service).

Launching any viable mobile broadcast TV service is expensive and most attempts outside of Korea and Norway have not succeeded. ( A viable mobile service would of course need several channels rather than just one). The really hard part is always getting the Consumer technology in place. DVBT2 will be technically advanced – but it will be hard to source recievers until broadcasters start broadcasting a number of channels in a number of countries. The huge advantage of DMB is, as pointed out above, that there is already a large array of consumer receivers available. There is even an Android DMB equipped tablet http://www.theidag.org/2011/03/tablets-with-dmbdab-to-new-markets.html. There is at least one android/dmb phone developed for the Korean market – as well as countless other phones and media player type devices.

Has anyone done any research into what the actual demand for mobile TV is? Where and how are people going to consume it? Passenger/back seats of cars maybe? Are the kids going to watch Breakfast News on the way to school? On the bus/train? Maybe.. but what does broadcast add to pre-downloaded content which won’t drop out in tunnels and can be paused when you go to the toilet/buffet or need to change train/bus? Live events are a definite possibility but are they enough to sustain a whole platform?

Even with on-demand content – I travel on Great Western trains out of Paddington quite a lot and I don’t think I’ve ever seen anyone actually watching their seat back on demand TVs. If everyone wants mobile TV why is it so poorly consumed in this most obvious setting? Is it the cost? It’s less than a cup of coffee on the train.

I wonder if the S Korean experience is working because they’ve no culture of radio, and actually what most people are doing with DMB is listening more than watching it. The screen is just giving them a cultural-technological context – something they’re ready to buy because they don’t “get” what radio is.

Paul: the research into the DAB trial a while back seemed to show that while people were buying those phones for the TV, they actually used them for radio, with radio achieving twice as many listening hours as TV. Difficult to know whether this was because of the content of the mobile tv channels, of course.

I watched South Koreans on the subway, as they were glued to their DMB-equipped mobile phones. But you’re right: they’ve no culture of radio, and use TV much as we’d use radio (a visit to an office showed a television in the corner).

I played with a DAB trial phone during the, um, trial. Sky News was useful in a few scenarios; Channel 4 offered a collection of short excerpts of Channel 4 programming which was less useful; and I believe the pay-per-view porn did well (I didn’t get that on my trial). I can’t remember ever watching live BBC One – the point of scheduling rubbish through the day is that it’s rubbish.

I had one of those lobster phones for about a year until it literally fell to bits. My summary when people asked me was always along the lines of “Hopeless as a TV, terrible as a phone, good as a radio”. Never saw the point in watching Bargain Hunt or whatever on the bus; the news channels were ok but the pictures were kind of superfluous; any worthwhile visual detail was lost on the tiny screen; and the stream kept dropping if you were in any way on the move so it was much less painful to switch to a radio channel and put the device in a pocket.

“suggesting a carrier-to-noise ratio of 7 dB for a Gaussian channel and 14-15 dB for a Rayleigh channel (no line of sight to transmitter, multiple reflections). The mode that the BBC are using for the ‘mobile’ part of this DVB-T2 trial requires only 0.7 dB in a Gaussian channel and, significantly, only 2.0 dB in a Rayleigh channel.”

That’s quite a difference! What would the figures be for DAB+?

Now where do I start?

Firstly just because the current DVB broadcast are not good for mobile reception, that doesn’t mean that DVB can not be designed for mobile reception. Obviously there is a trade off between robustness and capacity, and for a TV system designed for reception at home, they are going to go for capacity rather than for robust mobile reception. So no surprise that it is not good for mobile reception, but that doesn’t mean that DVB can not do the job with a different choice of options.

Also bear in mind that DVB-T2 has greatly improved error correction, which could be used to make the signal far more robust. (At this time it’s not used that way, as it’s used for HDTV and so it’s used instead to allow higher capacity transmission)

You say a broadcast system should be cheap to broadcast, and then you suggest using Eureka 147 based systems. This is an outdated in efficient broadcast system which is expensive to broadcast. Hardly the cheap broadcast option, especially when you want bit rates high enough for watchable video. One of the main reasons why it is expensive, is that it’s based upon a rather poor error correction system. The only advantage I can see is that it is already used in Band III. However I’d bet that the error correction used in DVB-T2 would make it work equally well in uhf and DMB does in Band III. Actually I’d like to see DVB-T2-Lite used in Band III, but that’s another matter.

I think they have tried to hold on to this old in efficient Eureka 147 system for too long. It is just to in efficient and too expensive to broadcast. We need something better, and the DVB-T2 is in a completely different league from Eureka 147. I appreciate there is the problem with existing DAB receivers not supporting new broadcast systems, but that is no reason to rule out introducing a modern system for other uses, such as mobile TV. Then perhaps one day radio could be moved to a modern system like DVB-T2-Lite.

As for chipsets not yet being available, well that may be true now, but give it a few years and that situation may well change.

Firstly just because the current DVB broadcast are not good for mobile reception, that doesn’t mean that DVB can not be designed for mobile reception.

I’m not arguing that DVB itself is wrong. If you planned a transmitter network specifically for transmission for handheld devices used on the move, then I’m sure DVB would do a fine job. I’m arguing that there already is such a transmitter network for Eureka 147 throughout the country, and saying that it makes sense for this system to also be used for TV as well as radio.

A DMB solution would appear to be a pragmatic solution, since the transmitter network is already in place, chipsets and receivers are already available, and it would unite a transmission network for while-mobile radio and while-mobile television, creating dramatic cost savings.

Suggesting that we go for a brand new technology, with no chipsets, no receivers, and requiring a wholly new transmitter network is, in my view, slightly less than pragmatic. There is always better technology round the corner, or better technology than currently existing services. That doesn’t mean that what we use is wrong, however: nor that we should constantly wait for what’s round the corner.

Well from reading what they are trying with T2-Lite, it would seem that T2-Lite mobile transmissions can share a normal T2 multiplex. They just use some of the available time during the transmission, and that is effectively just like using some of the capacity. I don’t see this as being significantly different from using DMB to transmit TV on the DAB networks. Both methods would be taking capacity away from existing networks.

I accept your point about the chipsets, for the moment at least. Although I think that if they decided to go with T2-Lite, then chipsets would be developed. Presumably introducing a mobile TV system will take some time, new receivers will need to be developed and sold, so is it such a big deal if a little more time is needed to develop new chipsets.

Basically introducing a mobile TV system will require new receivers, and if everyone has to buy new receivers then why develop new receivers using outdated technology. Why not use the best (or close to best) system available at the time, and the difference between T2-Lite and DMB is huge. I think the disadvantage of needing to develop new chipsets should be pretty small compared to the advantages of a modern broadcast system.

Personally I think that introducing mobile TV using existing networks is going to be a bit problematic, as it’s going to take away capacity how ever you do it. However if you do decide to do it that way, I don’t see that using the DVB-T2 networks already being set up is any harder than using the DAB networks.

Although actually I think a better option would be new transmission using spectrum freed up by TV digital switch over, or using one of more of the Band III DAB channels that were allocated but never used.

I think that which ever way you look at it. New receivers will need to be developed and sold, so why build a load of new receiver using an outdated system. Why not build the new receivers to use a vastly better new system.

(Patiently) The signal strength and coverage pattern for TV’s transmitter network has been designed for rooftop antennas and not for “while-mobile” reception at street level. DAB’s transmitter network has been specifically designed to do that. So, mobile TV in the UK can work much, much better in Band III. As you say, DAB has additional unused frequencies available which means this need not take away any radio capacity.

Any currently-available DMB receiver will copy quite admirably with DMB transmissions in Band III. In short, you could add DMB to the existing DAB transmitter network at low cost, instead of planning a whole new transmitter network to use DVB-T2-Lite in the current TV frequency band.

“I think that which ever way you look at it. New receivers will need to be developed” – that’s the whole point. DMB is up and running in many areas. We’ve got the receivers (I’ve got one); we’ve got the transmitter network; we’ve got the frequencies. DVB-T2-Lite? Er, none of the above.

OK well we are obviously never going to agree on this.

Personally I think that all the problems of introducing a new system, can and will be solved, and the are pretty insignificant compared to the advantages of T2 over DMB.

One final point, you say that the TV transmitter networks are not designed for reception at street level. Well I seem to remember reading that when the BBC were developing DAB, they estimated much of the coverage based upon data about Band III TV, designed for reception using rooftop aerials. They simply adapted the data for street level reception by assuming signal would be a certain number of bd lower. In the same way I assume that signals from existing TV transmitters would be available at street level, at lower signal levels, but that is just another factor that the mobile broadcasts would need to take into account.

Richard, your argument is somewhat self-defeating. You say that it’s better to develop new, better technology for a few years’ time than use technology available now, and yet surely in a few years’ time you’ll be facing the same situation with another new technology.

James’ point remains that the TX network to support DMB is in place across the UK and a range of receivers are already being churned out of Chinese factories for Korea. A bit of investment in upgrading the transmission kit and marketing is all it would take, apart from content, to launch a DMB-based mobile TV network here. You could have it up and running with receivers in shops within 12 months – unlike T2, which we won’t be seeing much before 2020.

My wider point remains: show me the demand for it. I’m not in any way convinced that linear broadcast mobile TV has much consumer appeal in the UK. Nor am I convinced that by the time T2 is feasible we’ll still be in a world where people want to watch TV in the same way at all. Here’s food for thought: The first Augmented Reality glasses should be available within 2 years. What’d really kick ass is a mobile delivery system that can broadcast deliver live 3D overlay-ready content to them.

Better still; the future of broadcast is surely not in developing a series of proprietary systems that have an ever-decreasing lifespan, but in developing a universal open-ended way to deliver IP data. That way, software can handle the specific decoding of the day and be kept up to date as technology moves forward.

Oh and one more point I feel I need to make.

Some people would argue that we could end up always waiting for a newer better system to be developed. I disagree.

When Eureka 147 was developed, it was the 1980s, and I think that computing power was a major issue when dealing with OFDM transmission. Hence I think Eureka 147 had to be greatly compromised in order to allow reception without needing a huge computer system. Even the demonstration of DAB I saw on Tomorrows World, needed a Transit Van to hold the receiving equipment.

Today however lack of computing power is not really a significant issue. So today the limitations are physical limitations such as Shannon’s Limit. I think that when DVB-T2 was designed they were trying to push the physical limits as far as they reasonably could. They were not hampered by worrying about computing power. So I believe that what they came up with is probably pretty close to what is physically possible. So from now on I wouldn’t expect anything other than minor improvements and tweaks.

@Paul Merkham

I was just writing an explanation as to why we won’t be in the same situation with waiting for new technology in the future, as these days it is the physical limits that are limiting DVB-T2.

I accept your point that everything is already in place to use DMB. However I just don’t see that as sufficient justification for using such an old in efficient broadcast system. If we use DMB, then I think we will end up with a poor service, providing a limited number of channels, with poor picture quality, and with many reception problems, unless they spend a lot of money improving the current transmitter networks.

Perhaps you are deluding yourself that DMB is going to work on hand held devices, unless there is a very expensive upgrade to the DAB networks.

Richard, are you seriously arguing that “technology won’t ever get any better than this”? Seriously? And you think I’m deluding myself about something?

No matter; what about the wider question: who wants mobile TV now and who will want it in the 5-10 years it will take to turn T2 Lite into a mass market system? Where’s the demand for it? I’m not seeing any.

What I am saying is that the latest data transmission systems are now approaching the limits of how much data it is physically possible to push through a radio channel of a given bandwidth and signal to noise ratio. That is a physical limit, and I doubt that improvements in technology will improve on that. That doesn’t rule out other improvements in technology, such as better codecs, but in terms of data transmission, I would not expect any more large dramatic improvements on what is possible today.

According to the DTG website, a Danish operator are now going to use DVB-T2 in a T-DAB allocation: http://www.dtg.org.uk/n4190

@Mike Dimmick

Yes I heard about that trial in the newsgroup alt.radio.digital. I think this is good news, as T2-Lite in Band III could turn out to be about the best digital mobile broadcasting system possible.

What would be more interesting would be if we can compare the results of this trial with the performance of DMB. The comparison could be very telling.