Death of Mobile TV: Long Live Mobile TV

watty · 11-01-2011 04:45PM #1

Comreg has abandoned plans to auction spectrum for DVB-H

http://www.techtir.ie/blog/watty/end-of-dvb-h

Mike 1972 · 11-01-2011 06:22PM

What exacty is (was ?) the point of DVB-H

Dont we have enough platforms already ? Doesnt it go against the whole notion of digital being more efficent if broadcasts have to be duplicated on another platform and isint mobile/portable equipment for recieving DVB transmissions now widely available anyway ?

Sponge Bob · 11-01-2011 08:34PM

Mobile operators thought they could charge for it circa 2005/2006. They slowly realised they couldn't. Comreg could have abandoned it in 2008 but clung on hoping for a hail mary pass from the market.

I never thought it would work here, the pullout by the recently granted DVB-H licencee in France last week probably convinced even Comreg ....and Comreg are not good at spotting reality or even admitting that there is a reality.

No doubt they will bore us all next year by going through the same long tedious process with DVB-NGH ....which still won't work here there being no market for it

DVB-T2 would be a far better 'unification' play, we don't have any fast trains or buses here which would cause the Doppler problems the DVB-H standard was designed to overcome

watty · 11-01-2011 09:29PM

DVB-T will work on our trains. The BBC version of DVB-T2 probably doesn't, smaller guard timing = more capacity. Both versions can have timing that works on a German High Speed Train. The Doppler thing can be a problem, but the US ATSC supporters overstated it.

watty · 11-01-2011 09:37PM

Mike 1972 wrote: »

What exacty is (was ?) the point of DVB-H

It was mooted long ago when a DVB-T only fitted in a Set-box and the receiver took 10W. The there are 11 Time slots instead of a single DVB stream in DVB-H (for handheld). Thus the receiver powers off for 9/10ths of the time (needs a short while to power up). Also the idea was you would use MPEG4 and 1/4 size video resolution.

But now you can fit a DVB-T tuner in one chip and use low enough power for a phone. Now a mobile device can easilly be 800 x 400 or more rather than 320x240 and you can have H.264 L4 HD even in a phone ARM SoC. So no point to it any more. I played with a Nokia demo of it.

The idea of Pay version of lower quality of the Free channels wasn't going to work once a phone maker could put an ordinary DVB-T receiver in a phone.

byrnefm · 11-01-2011 11:09PM

Just wondering - are there any DVB-T phones out there? I guess we'd have to find one then that works with MPEG-4, which I'm guessing would be pretty scarce..

Sam Russell · 11-01-2011 11:31PM

byrnefm wrote: »

Just wondering - are there any DVB-T phones out there? I guess we'd have to find one then that works with MPEG-4, which I'm guessing would be pretty scarce..

Big problem is the need for an aerial. Can you imagine walking down Grafton Street with a self directing Yagi on your hat. The mobile aerials are everywhere, while the DVB aerials are on top of mountains. The infrastructure is not there. The aerial is determined by the transmitter power and distance.

watty · 12-01-2011 09:23AM

People have sold analogue Portable TVs for years. You can get GSM phone with Analogue TV. Obviously a little whip aerial (6" / 15cm) only works in good signal areas.

Japanese ISDB Digital TV phones are common.

I know LG had phone selling in Germany some years ago with DVB-T MPEG2, no MPEG4.

There is not a big demand. In USA the main sales are for Sport.

MPEG2 only Portable DVB-T TVs http://www.pixmania.ie/ie/uk/10225/xx/xx/8/3/criteresn.html?srcid=391&mctag=gu_goog_513&gclid=CN3H78SqtKYCFY9O4QodW2xDGA

2.8" DVB-T (MPEG2 only) Portable Digital TV http://www.primesale.com/2.8-Inch-DVB-T-Portable-Digital-TV-with-MP3-Player--8GB-Built-in-Memory-_p6255.html

7" DVB-T allegedly with H.264 HD http://www.diytrade.com/china/4/products/6558849/Portable_DVB-T_MPEG4_H_264_TV.html

I think there will be high end phones with MPEG4 TV. Nokia and others have phones with full HD playback on HDMI! The actual tuner is down to a single low power chip.

But as with analogue handheld TV, the coverage will be poor. However, when there is coverage, it tends to work better than Analogue.

khumbu · 12-01-2011 08:52PM

Dropping dvb-h may not be any loss if comreg license a SFN nationwide VHF dvb-t mux. (VHF band part of saorview spec) It would then be possible to

1. transmit low definition versions of RTE1, RTE2, TV3 & TG4 (+ maybe News & 3e) on the VHF mux for mobile tv reception.

2. move the RTE radio stations from UHF mux to VHF. This would free up some space for maybe another TV channel on UHF mux.

3. add commercial national radio (if they're willing to pay) to this VHF mux.

4. abandon any further DAB rollout or even abandon DAB totally

This would allow nationwide reception of tv & radio stations on any portable dvb-t devices. As all services would be on one SFN no retuning would be required on devices used in car/train/bus travel.

Sam Russell · 12-01-2011 11:30PM

Well, they do have VHF in the spec. The compatible receivers (not the Freeview HD ones as they do not do VHF) would work. There could be audio only receivers for the radio stations. All this sounds like a good possibility, with winners all round.

watty · 13-01-2011 09:57AM

khumbu wrote: »

Dropping dvb-h may not be any loss if comreg license a SFN nationwide VHF dvb-t mux. (VHF band part of saorview spec) It would then be possible to
1. transmit low definition versions of RTE1, RTE2, TV3 & TG4 (+ maybe News & 3e) on the VHF mux for mobile tv reception.

2. move the RTE radio stations from UHF mux to VHF. This would free up some space for maybe another TV channel on UHF mux.

This would allow nationwide reception of tv & radio stations on any portable dvb-t devices. As all services would be on one SFN no retuning would be required on devices used in car/train/bus travel.

VHF is worse in a way for portable use. Aerial too big. Only OK for a Car/Coach. Existing DVB-T on UHF will work in Coach/train etc

Low definition is no use. Smaller than 4" devices are often 800 x 480 or more. Many 7" PMP etc are HD for video.

Over RTE's Dead body to move the new stations off existing UHF PBX. RTE Radio want those on everyone's TV and setbox. Via single UHF aerial.

Comreg will want to auction the VHF spectrum. I will be very suprised if any is used for PSB MUX.

Follow the MONEY
RTE has not got money to roll out more DAB
RTE has not got money to do ANY VHF PBX for DTT. Also issues of Aerials
Pay DTT is never going to happen.
Comreg can get money auctioning spectrum. They abandoned DVB-H because no-one is going to bid.

Look at France http://www.broadbandtvnews.com/2011/01/12/france-plans-to-switch-dtt-to-mpeg-4/
This is not about consumer, it's about money from Spectrum. Maybe they will drop the DVB-T2 idea because that would make even the TNT-HD and payTV boxes and TVs obsolete, but the scrapping of MPEG2 is likely.

Dropping DVB-H is no loss at all now. There was only any advantage 5 or 6 years ago. With low power single chip tuner and MPEG4 standard on DVB-T there is no point to it anymore. Cheaper to add another 20 DTT TX sites on UHF to improve coverage for all than rollout a VHF network for handheld devices. The existing VHF sites can't serve VHF DVB-H to handhelds. The mobile operators would have been expected to have 50 to 100 sites. Italy at DVB-H rollout years ago had 1,100 DVB-H transmitter sites.

Sam Russell · 13-01-2011 11:40AM

watty wrote: »

VHF is worse in a way for portable use. Aerial too big. Only OK for a Car/Coach.

Works very well on my FM radio. Strong signal allows for small aerial. Lower frequency has greater carrying power. Robust signal allows greater carrying power, smaller aerial. If you want handheld/portable TV and radio, then VHF is better that UHF. If a single channel SFN was setup for a large portion of the county (say 60% by population) it would only take 7mhz of the spectrum.

watty · 13-01-2011 01:08PM

FM Radio is only 100kHz bandwidth and below 110MHz. DTT is nearly 8MHz bandwidth so you need much more power. Also VHF TV is 185MHz to 275MHz approx, About 3 to 4 times poorer propagation as Band II radio. You are not comparing like.

RTE1 & RTE2 reception nationwide on Analogue VHF Band III is appalling. Apart from getting UK TV it's another factor in massive pay TV take up. This why in theory current RTE coverage is higher on Analogue than on DTT, in practice if you only consider "decent" reception the DTT coverage today is MUCH better than Analogue. RTE appear to count a snowy picture via 5 element VHF roof aerial as "coverage".

For handheld portable VHF DVB-T you would need MANY TX sites. I've been doing this kind of RF planning over 30 years and today use state of the art tools.

Sam Russell · 13-01-2011 01:17PM

watty wrote: »

FM Radio is only 100kHz bandwidth and below 110MHz. DTT is nearly 8MHz bandwidth so you need much more power. Also VHF TV is 185MHz to 275MHz approx, About 3 to 4 times poorer propagation as Band II radio. You are not comparing like.

Yes the TV signal is twice the frequency of the FM radio on VHF which means twice the gain. The bandwidth is 7MHz on the VHF band for DTT. Only one Mux would need to be be used, which could be a SFN for the whole country with a very robust form of coding to increase the reception possibility at the sacrafice of channels.

It is possible, but I agree, Unlikely. None of the likely proposers of such a system have any money and that is fatal for such a project, unless it is PayTV of course, where commercial rules are different.

watty · 13-01-2011 02:51PM

It's about 2.4 times on average. It does not have twice the gain. For a whip aerial of 1/4wave it's same gain. The Band III propagation (TV) is much worse than BandII (FM Radio). Also FM has two stages of degradion... (1) the receiver switches to Mono instead of Stereo and (2) the SNR increases before it falls of the Cliff in terms of FM demodulator working. DTT has much narrower sharper "cliff". That has been found to be a problem with DAB (similar Modulation) used Mobile as you get sudden "bubbling mud" artefacts and then sudden death. No graceful degradation. You need much better "fill in" of black spots than with FM.

SFN are not easy. You know why so few of the DTT sites are SFN?

There is even less likelyhood of PayTV than RTE doing it. PayTV has to actually make money!

Sam Russell · 13-01-2011 04:12PM

watty wrote: »

It's about 2.4 times on average. It does not have twice the gain. For a whip aerial of 1/4wave it's same gain.

I was of course talking about same size antenna, not proportional to wavelength. Most aerials used for portable radios in the VHF band are small compared to wavelength. Otherwise they are not portable.

In general, I agree with you, but the VHF mux for DVB could be useful in the future for some dvb situations. Dab radio is for the birds. Receivers are too expensive, coverage is iffy and quality is not great, because the greedy b......s want to squeaze too much out of it at the expense of audio quality. The FM VHF radio works, is dirt cheap, and better receivers and better aerials give better results that, at their best, are acceptable even to an audiophile.

reslfj · 13-01-2011 04:47PM

Sam Russell wrote: »

Works very well on my FM radio. Strong signal allows for small aerial. Lower frequency has greater carrying power. Robust signal allows greater carrying power, smaller aerial. If you want handheld/portable TV and radio, then VHF is better that UHF. If a single channel SFN was setup for a large portion of the county (say 60% by population) it would only take 7mhz of the spectrum.

watty wrote: »

DTT has much narrower sharper "cliff". That has been found to be a problem with DAB (similar Modulation) used Mobile as you get sudden "bubbling mud" artefacts.
SFN are not easy. You know why so few of the DTT sites are SFN?

DAB has a more gentle degradation as it uses only one FEC code level, but protects some of the bits less than others. DAB has a not robust signal and the "bubbling mud" sound is when the less protected bits loses their protection, but the frames are still included in the MP2 decoding.
DAB+ and DVB-T uses a two level FEC scheme and protects all 'audio/video' bits equally well. The digital cliff is 'steeper' and error packets are normally not used.
DVB-T2 and DVB-SH uses much better two-level FEC's and their digital cliffs are next to vertical.

SFN are used by all DAB/DAB+ and by DVB-T in very many countries in Europe. The 0dB echo* problem is, however, in some cases significant and gapfillers often uses another polarisation (H vs. V) to fight the problem. In some cases another frequency is used (moves outside the SFN).

With DVB-T2's rotated constellations, the 0dB problem is much, much smaller. In Sweden with SFN as large as 130 km between masts (with small/medium size relays even outside this area) all main transmitters are H polarised.
The MISO option in DVB-T2 is included to make reception possible under very difficult conditions.

watty wrote: »

FM Radio is only 100kHz bandwidth and below 110MHz. DTT is nearly 8MHz bandwidth so you need much more power. Also VHF TV is 185MHz to 275MHz approx, About 3 to 4 times poorer propagation as Band II radio. You are not comparing like.

If you want to compare like for like, DRM+ operates in 95 MHz channels in the FM band.
DVB-T2 has a 1.7 MHz mode that could easily operate in a DAB channel and would be very much more robust than DAB/DAB+ can ever be (7-10 dB).

The VHF band III is 174-230 MHz - with the 230-240 MHz band as an optional extension for broadcast.
Yes, the VHF antennas are large - but the real problem with VHF is not one antenna, but the needed separation (at least ~2/3 wavelength) between two antennas for diversity reception or MIMO reception. Even UHF has a wavelength that makes diversity and handheld less practical.
But VHF needs much less power compared to UHF and is much better inside houses.

watty wrote:

For handheld portable VHF DVB-T you would need MANY TX sites.

Even more so with UHF.
Some of the work - I believe - they are doing around DVB-NGH is related to eliminate the need for many gap-fillers for mobile reception.

Lars

* The 0dB problem is the situation where two signals are received with the same strength but with a 180 deg phase difference - effectively eliminating each other. For a OFDM signal only a limited number of the carriers will be close to being 180 deg out of phase and many more carriers will add together to enhance the signal. The missing or weak carriers will end up as bit-errors and be corrected by the FEC - but at the same time lowering the ability of the FEC to correct other bit-errors. The signal will be less robust.

watty · 13-01-2011 04:50PM

Aerials for portables don't work like that.

A yagi aerial might approximately be twice as good for same lenght at twice frequency if the boom is less than 1.5 wavelenghts on higher band. Beyond a certain point the increase is more gradual.

Sam Russell · 13-01-2011 04:58PM

watty wrote: »

Aerials for portables don't work like that.

A yagi aerial might approximately be twice as good for same lenght at twice frequency if the boom is less than 1.5 wavelenghts on higher band. Beyond a certain point the increase is more gradual.

I am not talking about yagi aerials, I think whips are used on portables.

watty · 13-01-2011 05:01PM

Yes lars but we are talking about hypothetical reuse of abandoned VHF Band III DVB-h (original post) for hypothetical VHF Band III DVB-T as per current specification (PDF link) . Not DVB-NGH, DAB, DRM+, DAB+ or DVB-T2.

My point is that we are unlikely now to use up the 6 allocated Multiplex channels on UHF. It will be amazing if we use three of them.

So NO-ONE is going to roll out the existing RTE NL DVB-T spec on VHF band III.
Comreg wants to auction Spectrum.

For "portable" or "handheld" TV use extending the current two PBX mux makes more sense and is cheaper. Even the existing five VHF sites on Band III Analogue used as a SFN on VHF DTT would not give useful "portable" or "handheld" TV covereage on existing spec. There would need to be much more than five sites.

So better instead to forget VHF and if you want better "portable" or "handheld" TV coverage just improve the coverage of the current DTT network. There is not any point of a simulcast of UHF content on VHF.

If we need more content for Free TV, then RTE NL should get a 3rd PSB Mux out of the 6 UHF allocations. Only two are in use. The other four are reserved for payTV that will never ever happen.

watty · 13-01-2011 05:09PM

Sam Russell wrote: »

I am not talking about yagi aerials, I think whips are used on portables.

Yes. and you can't make a handheld whip have more gain at 250MHz than 95MHz.

Valid sizes are 1/4 and 5/8. The 5/8ths has maybe 2dB more gain but is easily detuned so usually only used on car/van roofs etc.

1/2 wave is possible, very awkward to match and easily detuned. Less gain than only slightly bigger 5/8ths

a 7/8ths is about possible. But not handheld.

Co-linear 5/8th + 5/8th works. Pretty big and easily detuned. Only for vehicle roofs. About 5dB more gain on good day. Needs good groundplane. So no use for hand held.

1/4 + 1/4 co-linear is possible. It needs complex feed compared to a stacked pair of 5/8ths. 3dB more gain. Only possible on a mast. A pair of dipoles more normal.

You can't get more signal simply by having a longer whip.

Death of Mobile TV: Long Live Mobile TV

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