There is no analogue TV in the US now
"to carry one analogue channel or a digital multiplex"
Not any more. Analogue TV in the states was switched off in June.
The CTIA and CES have produced a white paper outlining how to extract 180MHz of TV-broadcast spectrum without impacting TV quality or coverage, and it's worth reading. The Cellular Telephone Industries Association (CTIA) and Consumer Electronics Association (CES) co-authored the paper (pdf) which proposes replacing centralised …
Actually, when using digital transmission multiple synchronised signal sources can be used to improve the Signal-to-Noise ratio.
3G does that - it applies convolution filter to its input - the input is multiplied by a coefficient and added to itself at an offset. This is done several times with different offsets and different coefficients. The signal contains "easily recogniseable" patterns which can be used to optimise the coefficients. As a result the more multipath - the better. The entire thing is half a page of linear algebra and it delivers several times better S/N and spectrum efficiency than the "engineering marvel" also known as GSM. Classic case of "Math meet Engineering, Engineering - meet Math. Engineering - you lose".
So if the multiple sources are really synchronised to a level where this can be applied the S/N will actually be better the more ghosts you get. This will require fairly "hard sync", but most radio sites will get that for LTE anyway.
How gradual developments in one tech trigger cross fertilisation in another.
From cellular phones to cellular TV.
One small detail. Are they expecting this to be done as a software upgrade to the boxes or a replacement of the boxes?
The latter (I suspect) would run a bit more than $2bn.
Worth a deeper look by the powers that be.
"Modern boxes accept the strongest signal and are capable of disregarding the others."
Really? How's that work and could you please explain it to the authorities? I have a RX listening on a specific frequency; if another transmitter pipes up on the same frequency, I have no mechanism *within the receiver* of discriminating between the two analogue signals – if I could interference would, generally speaking, be a thing of the past!
What I think you mean is this: Because these smaller transmitters are localised they won't need to radiate anything like the hundreds of thousands of Watts the big 'uns do at present - so the chance of even hearing a non-local repeater is massively reduced. Couple that with a slightly directional antenna on the receiver and you're on a winner: with the unwanted signal some 30-40db below the desired one, you have a half-decent chance of losing it in the noise (making the RX slightly deaf will be the manufacturers dream - it's cheaper to construct anyway).
>> Classic case of "Math meet Engineering, Engineering - meet Math. Engineering - you lose".
I don't know if this is New Model Schooling, but when I was at university, applied math was actually what engineering was all about. Sadly to say, some of my cow-orkers consider math a "black art" best to be avoided and created to confuse people, but then again they correlate with antivaxers, GSM-gives-you-cancer and Climate Change Deniers...
Are you just trolling? :)
"immediate end of civilization predicted"
- these are the 2 polar opposites of the debate - definitely not tarred by the same brush.
The math is what the sceptic / denier issue is all about:
Chicken Little says, "The sky is falling."
Johnny Sceptic says, "Really? Can some show me some emperical evidence to back that claim?"
Chicken Little repeats, "The sky is falling. The IPCC authorites say so."
Johnny Sceptic says, "Okay, but that's not evidence, that's Argument by Authority. I can show you a petition from 31000 scientists (petitionproject.org) who say that you're wrong. Can you show me some actual cause and effect methodology or some observational evidence to support your argument? I don't want to see your flakey computer models which couldn't even predict the global cooling we've had for the last 9 years - they aren't emperical evidence, either."
Chicken Little repeats, "The sky is falling. The debate is over."
Johnny Sceptic asks, "Political debate? What debate, did I miss it? Last I heard Al Gore still refuses to debate Lord Monckton, despite growing pressure to do so. If it's scientific debate, bring your evidence and let's have it out!"
Chicken Little repeats, "The sky is falling. We must act now!"
Johnny Sceptic says, "You mean act before we discover a reason not to? One word - climategate."
Chicken Little says, "We're polluting too much and that's going to cause to the sky to fall, we need to invest in research in renewable resources."
Johnny Sceptic says, "I agree that researching renewable resources is a good idea! So let's do that for the right reasons. Taxing the wrong thing (CO2) is a lousy way to solve a problem. 80 billion dollars in the US alone has been spent so far researching climate change. How many schools, hospitals, roads, disease research grants, etc. could have been funded with that same money."
Chicken Little repeats, "The sky is falling."
Johnny Sceptic says, 'Go away!"
Personally thinking of that day pisses me off still. My grandma had to get direct TV due to it, and calls up non stop asking how to work it... every day...
Before the switch she got every local station. After the switch she got absolutely nothing(she had the craptastic converter box, along with a $90 antenna that claimed it was specially made to get digital signals...), along with everyone else I know.
So in all truth I doubt its 10% anymore probably closer to the 3% that live right next door to the transmitter towers.
The use of "FCC" means we're talking about television in the USA, where all of the TV stations (except for some low power types) were forced to switch from analog to digital earlier this year.
Therefore, there's no problem of discriminating between two, or more, NTSC (USA analog) signals on the same frequency, because there isn't going to be even one NTSC signal there.
Mine's the one with the beat-up, well-thumbed 30-something year old copy of the Kaufman-Kiver book weighing down the one pocket, and my equally old Third Class Ticket in the other.
Lots of channels, near endless bandwidth (just put up more satellites like the pile at 19.2E), no need for transmitters all over the place, and fairly immune to weather which is more than can be said for a lot of DTT. And while it might seem expensive to put a satellite into space and maintain it, it would appear to be a more appealing option than to try to roll out decent DTT to everybody - especially those in unpopulated areas - hence the BBC's support of Freesat. One central broadcast source instead of hundreds.
for high bandwidth broadcasts needing no return channel, i.e. TV, satellite transmissions are the only sensible choice. for the small number of households shadowed by hill or mountain, a reflector or repeater would be relatively cheap. the receiver technology is proven and now cheap, apart from the inconvenience of a dish - even DVB-S2 high-def receivers are less than GB£80 discounted.
if you want a back channel for, say, internet service, then cable makes sense even though it's quite expensive to roll-out a network.
meanwhile what happened to DVB-H?
Nobody wants more radiation in their neighborhoods.
Keep the TV stations centralized, where they can provide emergency information no matter what.
There is plenty of little used spectrum from 225-380 MHz. It already belongs to the government. Give that to the dweebs.
It is not quite the same as the UK, we are getting relay stations carrying DTT but the higher power sites are still needed to provide a feed for many of these relay stations and also people in remote areas not fed by a relay station.
It is possible to use lots of small sites in urban areas but not feasible for scattered rural communities.
The big problem in the US is that you have lots of small TV stations all competing with each other. It might be difficult to get them to cooperate to install a large network where every station is received equally in the area. There were similar objections to using a digital radio system like DAB where a number of different stations share one transmitter and are all the same at the receiver.
like making sure everyone who gets over-the-air TV can still receive it under this plan, it is a really good idea Homeland Security-wise, as well. 9/11/01 took out a lot of TV broadcast capability for several hours, during an attack on the US, in a broadcast area covering about 20 million people. Decentralization of this magnitude would greatly help communications in times of attack or rumored attack.
They could simply build a small transmitter into each power transformer along the roadway, but then it might be easier to just finish the job and run the last 5 meters of cable right to the house. I don't think I'll be looking forward to broadcast TV as clear and reliable as mobile coverage currently is. Then again, if CTIA can con the FCC into pushing its infrastructure costs on to TV operators, perhaps mobile coverage would improve. No really, I wrote that with a straight face... mostly.
TV 2-dot-0x7DA is also made of badger's paws.
In fact, the ability to run Single-Frequency Networks was one of the design criteria for DVB-T. The UK runs a Multi-Frequency Network because it was first to implement, but many countries are on SFN. The bandwidth savings are substantial.
The way this works is that each symbol in the signal has a "guard time" around it to allow for the "ghosts". It works really rather well. It doesn't fit nearly as well in the substantially less sophisticated 8VSB modulation used in the ATSC system, but with enough DSP at the receiver it can be made to work; indeed, for digital TV to work in cities with their multipath-intensive propagation environment it *must* be made to work or most people will not have service.
First I'll lose the 9 US stations I can receive from across the lake.
The talk about this in Canada includes the key words "where numbers warrant". That is if you don't live in a city too bad (they say "only" 5% of people using over the air TV would be cut off).
I think it's really a step towards NO free over the air TV, everyone has to pay for cable or sat. In Canada most of the Cell phone companies are also into cable or sat TV. No surprise that they would love to dump free TV and give them the bandwidth for cell phones.
How would this free up bandwidth for the mobile operators?
If TV transmission moved to lower powered transmitters mounted on mobile phone towers, how could the mobile phone operators use it? There might be less RF energy bouncing around the planet in total, but there's just as much in the bands they want in the local areas they want.
To restate: they want to replace huge, powerful area-blanketing transmitters using frequencies they want for phones with networks of small, relatively weak transmitters operating on the same frequency, in *precisely* the same locations as mobile phone customers?
Or have I missed something?
The DVB-T standard actually allows you to create a mesh network using a bunch of low power transmitters all broadcasting on the same frequency. That's one of the benefits of using QAM. So in Europe, this would be a great idea.
The ATSC standard is a bit different. You can't use a mesh network because the current 8VSB modulation standard doesn't hold up to heavy multipath the same as QAM. That was the cost for having a modulation system that is 30% more efficient to transmit. Now, there is talk of adding additional error correction to the MPEG bitstream via the E-VSB addition to help out against multicast, but nobody really knows how well it'll help.
It might be time for the FCC to consider adding 4/16/64-QAM as alternate modulation standards to ATSC. They can roll it out as a requirement along with MPEG4-AVC/H.264 video compression for their "ATSC v2" standard. Then you can mesh away all you want. Best of all, everyone will get free converter box upgrades again because the wireless companies will have loads of spectrum to buy from Uncle Sam.
The ability of DVB-T to "mesh" or rather create a single-frequency network (SFN) is based on the guard interval of the OFDM (or COFDM in DVB-T parlance) and not QAM that is used to modulate the individual carriers of the OFDM signal. The guard-interval of an OFDM signal is what is used to protect the received signal from multiple propagation paths from the transmitter to the receiver and in most OFDM systems is a cyclic prefix or a copy of part of the original signal from the start to the end of the OFDM block. In the DVB-T systems the cyclic prefix can be between 1/32 and 1/4 of an OFDM block. The longer the guard interval the better multi-path rejection of the system. The rejection is the same interval as the cyclic prefix itself.
A synchronized OFDM system means that multiple transmissions just look like multi-path and so an SFN is implicitly allowed in any OFDM system. An 8k carrier DVB-T frame with a 1/4 cyclic prefix has a guard interval of 250 microseconds... Multiple that by the speed of light and you'll see that the multi-path rejection is 75km between the propagation path lengths of the signals.. You'll probably want your transmitters closer than that in a real SFN, but 50km transmitter spacing with an 8k carriers 1/4 cyclic prefix is possible
Pity that the US system doesn't use OFDM.
Do you REALLY think that the $$$ the government will make selling out the frequencies will go to pay for the TV stations upgrade. I have my EXTREME doubts. Once the government gets its hands on any amount of money (all governments are this way!) it is VERY reluctant to give anything back. More than likely they will stick it to the TV stations and mandate (just like the Digital TV mess we now have) they do the job themselves. And that will go over how well??
The cell phone people should just add digital TV receivers to their cell phones and off load the "Broadcast" traffic from their cell networks. Look why should there be any more than ONE stream of bits for a TV signal to any number of cell phones, not one for each as it is now, chewing up LOADS of bandwidth in the process.
CTIA should pound sand!
Oh, and analog TV worked MUCH better that the junk compressed bad signal stuff we have now. The only "feature" is wide screen and a not bery good one at that!
P.S. Just make it work in the SF bay area (loaded with mountains and LOTS of dead spots!
Nicely presented, but CTIA's proposal is still dog crap.
"The CTIA argues that modern set-top boxes are so armoured against receiving bounced ghost signals that they can cope with one coming from a different transmitter. Modern boxes accept the strongest signal and are capable of disregarding the others.
That assertion is the weak point,..."
Now there's a massive understatement. Having gone through the US conversion to DTV, I can tell you that the biggest (and as yet, un-addressed) problem with the DTV receiving equipment available in the US, is that the current equipment is extremely susceptible to losing sync with the packet stream due to multi-pathed signals.
During the change over to DTV, for a time we had simulcast analog and digital versions of the same broadcast channels back to back. We found that for best DTV reception, you had to use the analog channel to position the antenna so that ghosts (multiple signal paths) were effectively eliminated, and this would also produce the best DTV reception, as a clean single-pathed signal would not confuse that packet clocking logic the way a multi-pathed signal would.
So their contention that multi-pathing is not an issue for DTV reception with current equipment is simply a blatant lie, a fiction to sucker supposedly gullible FCC regulators into doing CTIA"s bidding.
"...but if the CTIA has its sums right then there's little reason why the system wouldn't work. The group reckons it will cost less than $2bn to built the new transmitter network"
I suppose the CTIA will underwrite the installation of this $2bn worth of repeater infrastructure on their towers? Yeah, right.
More likely, these s**tweasels will probably expect either the local broadcasters or the local and/or federal taxpayers to fund their repeater build-out. Then they'll find a way way to charge us all subscription access fee's to their repeater network, by helpfully providing DTV equipment, that "solves" all of those nasty multi-path issues which were so conveniently created by the presence of the CTIA sponsored repeater networks.
Of course, CTIA members would sell such a service in the same way they routinely sell cell phones in the US. The equipment will be provided at low or no cost, under a minimum 2 year contract, with easy payments of "only" $19.95 per month. As with their cell service contracts, early termination fees of $250 or more will apply. (No need to change an existing, lucrative, and proven business model, right?)
Time to do some research and write some letters to the FCC.
Everything you say has the ring of common sense backed by real world experience actually trying to get the "better" digital TV tech working in the real world (instead of inside some computer sim or spreadsheet).
It is therefore inevitable that nothing you say will be taken into account when the simpering FCC hand over the keys (again) to the salivating wolves at the gate.
I even like the soup-briquette "s**tweasle", which I'd never heard before, but which fits so well the use to which you put it.
Keep up the good work, Geoff.
I was watching a US TV station last night and they are running commercials that alert viewers of special interests intentions to shut down free broadcast television. US TV stations are getting cash from cable companies to rebroadcast their signals, and now the same was just approved in Canada.
At the same time, with the switch to digital in Canada stations will only be required to broadcast in markets with 300,000 viewers (they say only 10% of viewers use antennas) so only cities with 3,000,000 people will get free TV.
If a station gets paid for every viewer on Cable, but gets nothing from over the air, they are going to want to force everyone onto cable/sat.
$35 a month (sure to go up once they have a monopoly) for Basic. Fewer stations then I get now (for free), over compressed, with some filler crap like the shopping channel. Looks like a crap deal to me.
1) providers should be all for this, as the energy required to get the signal to where it's received would both be less, and it would provide better signal in more places where it;s currently weak. Leet transmit power means less electricity bill dollars.
2) the FCC would pay for this out of pocket, on a short term low interest loan, and make back 10 times the loan amount when the frequencies go to auction.
3) the current range of frequencies available assumed more than 20 broadcast stations in each market. Most have far less since most moved to cable/sattelite leaving onle the big 5 networks on towers (and small time local chanels like eTV). We could easily shrink the entire frequency swath and still offer the same channels in the same or better quality on less air as there would be less crossover of channels from area to area.
4) smaller (shorter) towers may be able to operate underneath FAA tower limits, making them far less expensive to operate, and cost a fraction to have someone change beacon lights on. They each also need far less land. The land the current towers are on is also very valuable in many cases, with amazing views of the surrounding country, and could be worth tens of millions per big tower we can take down.
5) all new towers means no structural expenses for 25+ years, the expected life of broadcast TV.
6) the new digital boxes do handle signal mirroring much better, and everyone now has them (who wanted them) so there's no upgrade kickback issues like we had moving to digital in the first place.
Even if this cost 6 billion to pull off (triple the estimate), subsidized for 3 years at 1% during the build out, if it made back half their low estimate (which is very low already), it would triple the FCC's investment (posibly 10 times that profit if they hit the high number) and be a nice kickback into broadband stimulus money, cable subsidies, WiMax rollout, or a simple tax refund to those on subscription services. $30b could go a long way...
I'm for not only doing this, but in the process, let's compact the signals into a narrower swatch of band, changing what channels some networks are on, so that channels are less randomly scattered across the band. In rural areas with fewer frequencies available we could free up more airwave for wireless internet, something that costs too much to cable in some areas, and in dense cities, we'll have more air for cell phones. All this without dropping anyone from coverage of current broadcast TV, and for a large portion, it would turn static laden channels 30-40 miles from towers into cruystal clear signals.
The idea is that more TV stations will be able to share fewer frequencies because the radius of interference will be reduced. If you cut the signal strength in half you can reuse that frequency for another station in half as many miles as before (actually less than half due to how signals propagate). This allows you to use only half as many frequencies as before. The way it is now, New York can have channel 2 but Philadelphia won't, then channel 2 is used again in Baltimore, but not Washington.
It still seems like an incredibly dumb idea to me, despite the upfront costs they quote it seems to me the TV stations are being left with a distributed maintenance and upgrade nightmare. Plus when the repeater in East Mountaintop goes down the TV station will probably take weeks to fix it whereas when their one and only transmitter goes down now they must get it back up immediately or they are out of business.
It might have the advantage of making it easier/cheaper for new start-up stations to get in the business. Otherwise it seems like a big increase in complexity for little benefit.
due to the lower frequencies (54-500MHz) than those for cell traffic (900, 1800, 2000 MHz), and beefier to handle the higher power. Cell tower owners might be resistant to bearing them. Current FCC rules require both primary and backup transmitters at the big tower--and cost/benefit says broadcasters are not pleased when their $/second flow get broken. Satellites are neat, but look at what Sirius/XM had to do to provide fill in coverage for the city canyons. So does the thing just level out to putting the fiber optic cable fed one watt translators on the nearby power poles.
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