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BBC White Paper Claims HD Over Low Bandwidth Signal
Kelten Miynos writes "According to CNet, the BBC has written a white paper in which they claim it's possible to double the available Freeview TV bandwidth by using some clever technologies. 'Doubling the space would mean we could easily have HD channels on Freeview, although everyone would need to buy a new receiver and aerial to pick them up. The key to all this is something called MIMO, which stands for multiple-input multiple-output. MIMO works using two transmitters, and two receivers. The two transmitters mean the two sets of data — sent on the same frequency — will arrive at the receivers at different times. Different arrival times are what allow the receiver to differentiate between the two separate signals and subsequently decode them.' These procedures could then be transplanted abroad to other countries with similar services."
Even with two transmitters, it doesn't sound too prone to break downs, this could be a not-too-costly winner.
MIMO isn't exactly news though, but it's of course interesting to see it being used in this context.
I wonder how long this new found bandwidth will be enough, as we tend to expand usage right along side available resources at a disturbingly linear rate.
This wouldn't just require new equipment to view the new transmissions, it would also require throwing out all the freeview kit that the BBC and the digital alliance have spent years convincing the public to buy. This idea could only really be implemented in an unused frequency band - the space vacated by the analogue switch-off seems ideal for it to me, if only the UK government can be prevented from selling it for some other use.
As the article says, a far simpler solution to the badwidth issues of freeview would be to ditch the huge number of junk channels and use the bandwidth to provide a HD signal for the ones that people actually watch.
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In the UK, we are moving over to digital TV region by region, starting next year. Already, people have had to go out and buy Freeview boxes, and in many cases new ariels (I needed one). Somehow, I doubt anyone will go for buying a new box and ariel just for the lucky minority to have HDTV.
Anyway, if you are going to have a new box, why not move to MPEG4 as well? That would double the number of available channels again.
const int one = 65536; (Silvermoon, Texture.cs)
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The BBC announced the world premier broadcast of Finding MIMO
My take on this is that standard def freeview will continue, but if you want a HD version you need 2 boxes?
liqbase
But who cares when we are going to get free HD via satellite ?
MIMO is an intriguing technology but unfortunately the acronym is used loosely to refer to many unrelated things.
The most exciting MIMO technology is also known as "space multiplexing," which lets a system with N transmit and N receive antennas transfer data at N times the rate of a system with just 1 transmit and receive antenna. The marketing departments like to use MIMO to refer to any old system with multiple antennas, because technically the definition is correct. However, most of the time those systems can't get this kind of performance gain. I believe most of the pre-n hardware out there just does fancy antenna selection; the language is usually careful to say that "802.11n supports space multiplexing," even though it is optional, and there are no performance numbers yet. Someone please correct me if I'm wrong, which I'd love to be!
The way space multiplexing works is counterintuitive: each transmit antenna sends an independent stream of data on the same frequency. The "magic" that makes it work is the fact that multiple receiving antennas observe the combined signal at different times (the article summary got it surprisingly right here); specifically, the phase offsets observed at different RX antennas should be random. This can happen when the signals bounce off a lot of objects like walls indoors, or buildings etc. outdoors.
Here is a simplified example that illustrates how this can work. Suppose we have 2 transmit antennas. Suppose at a given time we send two signals a and b. If we only had one receive antenna, we would observe (a+b), and there would be no way to extract the individual signals. However, if we have a second antenna, AND the phase offset happens to be such that the other antenna gets (a-b), we can clearly extract the original signals.
There are environments such as open outdoor fields with line-of-sight, where the received phase offsets are not random and don't happen to be "nice" like in the above example; in that case MIMO performance falls back to 1x1, or a little better if the phase offsets have some degree of randomness.
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Just a little question: ...
... so i know at least a little bit about it ...
Same frequency, different signals does equal noise, doesn't it?
Different frequencys for different signals (frequency multiplexing) would do the job, but if you send two or more different signals on the same frequency you get inter symbol interferences and high chance for errors while decoding (as in 'actual watching tv') the signal.
This white paper sound like BBC-made BS or the description here is faulty
btw: part of my course of study is transmission technology and multiplexing for radio and fiber optics
Freeview and all the rest have pitfull quality compared to a good analog signal...
How could they not, seeing as the image is DVD-resolution and framerate (and coding, MPEG2) but at something like 1/4 to 1/8 of the bitrate..
It's pathetic.
The new digital television technologies are a net _loss_ for consumers. Power-hungry settop boxes, lower quality, possibility for DRM. What's to like?
A decent CRT displaying a decent analog signal beats the pants of an LCD displaying DVB-T any day.
To increase bandwidth, cable companies used to have dual channel setups over analog cable (before digital). They used to have 'A/B' switches on the boxes and you could access double the amount of channels.
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Two is actually pretty small. There was a system proposed back in 2002 by the acronym BLAST (Bell Lab Layered Space Time) that used up to 8 transmitters. As was noted in another reply if we go with a new transmission method we might as well go for a different encoding scheme like MPEG4 as well and double the available bandwidth again. We might as well go with more than 2 transmitters as well to more than double the bandwidth. This stuff does require A LOT of horse power in signal processing to tease the signals apart especially when you factor in multpath reflection (which is considered somewhat of a plus by BLAST as it make the signals easier to discriminate).
Broadcast antennas have to be in far-flung locations, but receiving antennas need only be directional and can be put virtually on top of one another. To speculate on increasing the bandwidth more we could polarize the signal as well. Throw in a little time-shifted redundancy to the error checking and you could have a very robust system even with electrical noise and lightning, though this would take some SERIOUS horsepower to decode the signals. But Moore has shown bandwidth is precious and processing power will increase. I suspect we could easily pack full 1080P 60fps in 1 MHz channels now, it would just be expensive initially. Remember bandwidth and signal to noise ratios are just competing tradeoffs. With a strong enough signal now you could do HDTV in 1 MHz with no changes to transmission method. Multi Antenna Multi Receiver adds a new dimension to multiplexing the signal in. AM multiplexes one dimensionally in amplitude, FM one dimensionally in frequency, digital uses both for two dimensions. Now we can add spatial multiplexing and to go even more over the top with polarization (though multipath makes polarization crazy hard to decode).
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This wouldn't just require new equipment to view the new transmissions, it would also require throwing out all the freeview kit that the BBC and the digital alliance have spent years convincing the public to buy.
Anyone care to tell us yanks wtf freeview is?
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Well, I'm also a yank, but I have been following it. Freeview is digital tv over the airwaves. Basically all tv in the UK will be digital, starting a while back in limited areas. Anybody that isn't getting their signal through cable or satellite would have to use freeview. Which of course requires a different tuner than tvs already have.
http://www.freeview.co.uk/home
Judging by your UID, you're not new here. Might try clicking the link IN THE FUCKING SUMMARY that links to the Freeview wikipedia article . . . . . it might explain some things.
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Digital TV via an aerial.
Previously there'd been two competing digital TV providers: Sky, selling digital via satellite, and ITV Digital, selling digital via aerial. Although both carried the same basic menu of free-to-air channels, they were basically pay-TV providers trying to push subscription services, and didn't really achieve much. Sky Digital inherited the viewers from Murdoch's existing satellite operation, but didn't really expand the market AFAIK, and ITV Digital did very poorly, being a second-best offering as a pay-TV platform, and again failing to win over the majority who aren't really interested in pay-TV. ITV Digital folded after a while.
At this point a BBC-led group established the Freeview standard, which is based around a set-top box made as cheap and simple as possible, and which provides a comparatively small number of free-to-air channels. There's an expansion that allows encrypted pay-TV channels, but few exist and hardly anyone bothers. Because the box was very cheap and it was a one-off expense - no subscriptions, no registration - it became the standard very quickly. These days it's being built in to most new TV sets as standard, and supposedly we're on course to be able to switch off the old analogue broadcasts on schedule.
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This is COMPLETE RUBBISH.
Basically once you add a second transmitter on the same frrequency the noise floor increases. Basically the first transmitter adds noise to the second transmitter, and vice vera. Some people will argue that if you know what the first signal is then you can subtract it to find out the second signal. Things do not work like this since the first signal is distorted in the ether, meaning that you cannot properly subtract it.
If there was the bandwidth available to have the two different transmitters on the same frequency (such as with CDMA), according to Shannon you could then just use the original transmitter and double the amount of data you are sending from it. This might mean doubling the power to get the same energy transmitter per bit, or it may mean that there is already enough power being transmitted thanks to error detection and correction.
This scheme is NOT MIMO. I think you would call it MISO or SIMO.
With MULTIPLE FREQUENCIES this COULD work. It is not that hard. On the receieve side you have two receivers and two buffers, maybe up to 1/2 second long. The data being receieved comes in inside packets. What you then do is split things at the transmit side so that each transmitter is sending half the signal.
But this is where things get fun. Each half of the signal need to be able to generate an OK signal by themselves. Think 128K MP3's Vs 64K MP3's. The 64K ones dound crap, but the 128K sound good. The trick is to define an algorithm to generate the 64's so that they can be combined to create a 128K that sounds good. Using Discrete Cosine Transforms this should not be too much trouble, for instance interleaving the data between the two output paths so that if only one is receieved you still have a picture....
Darryl...
I had a MIMO Netgear wireless card and router once. They claimed it doubled the bandwidth and range of your WLAN on the same principle. I thought using two signals was kind of cheating, but it worked.
Here's one of the routers.
Freeview is an initiative that aims to discourage us from watching television, specifically by making it really annoying to channel-hop. Let me explain. With our existing, analogue equipment, changing channels is nice and fast; it takes perhaps half a second. But the analogue transmitters are going to be shut off in a few years time. Once that happens, the only way to recieve television signals will be with a cable or sky box, or a Freeview box, each of which takes between two and five seconds to do whatever it is that they do to change channels. The result is that I abandon television out of frustration.
Quick nit-pick: you forgot Digital Cable in your list of Digital TV providers in the UK...
The "2 to 5 seconds" to change the channels on Freeview is nothing to do with decoding times or slow processors in the Freeview set-top boxes. Nope, it's simply because there's more than 9 channels and the channels can indeed be numbered up to 999, which means that up to 3 digits have to be pressed to change channel.
As anyone with a cable or satellite remote control already knows, multi-digit channel numbering means that if you want to hop non-sequentially between channels and the channel numbers are only one or two digits, then the set-top box will pause for a second or so to see if you are adding the second or third digit. If you don't, then it assume that the digits entered so far are the complete channel number and then jump to it.
This is why many Freeview remotes have a "channel plus" and "channel minus" button to get around this problem for channel surfers - just press that to cycle sequentially through the Freeview channels with no digit-delays. I find channel changing to be about one second on the Freeview and IDTV sets using the +/- buttons on the remote, which is OK (but I could believe slower boxes might take 2 seconds, but certainly not 5).
Channels not nicely numbered to allow such +/- surfing? Again, many Freeview boxes/sets allow you to reorder the channel numbering to your preference (e.g. I can only get Welsh Freeview, which insists on putting S4C on channel 4 and English Channel 4 on channel 8, so I swap those over!) and, even better, let you delete channels completely, which I do for all the pay channels, shopping channels etc.
And if it breaks, you can easily fix it by reversing the polarity.
There's a really simple solution to this that isn't very elegant:
Take one HD channel to transmit scaled down versions of all available channels for some given area. Keep one tuner constantly on this channel. When switching, briefly show the scaled down version while the main tuner switches over.
I'm sure this isn't the best solution however.
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Almost ALL indie makers are using divx on standard DVD for Hd content distribution. Hell they even MAKE set top dvd players that play DivxHD DVD's and they look fan-fricking-tastic. People like to toute you need insane bitrates for clean HD yet I see every day incredible looking HD content at DVD bitrates played off of DVD discs onto a 1080i projector to a 102 inch screen for customer demos in shop. WE demo HDDVD as well but the custom cant tell the difference.
You can get HD content on standard HD discs. a dual layer standard DVD can hold incredible 1080i content that looks fantastic on all HD displays available, but then it does not have DRM up the wazoo and is not making several companies morbidly rich with royalties.
Do not look at laser with remaining good eye.
(or would want to). I've got a flat in a listed building in the middle of a town.
Being in a town is great as I can get my Freeview reception and speedy ADSL2 - unfortunately I'm not allowed to slap a satellite dish on the outside of my building and as even the f'in pavement outside is listed, it was considered too expensive to lay cable. If I'm ever to get HDTV it's going to be using MIMO, after switchover, or IPTV.
Now I know I'm probably in a somewhat rare position, but loads of people find they can't receive stuff for all manner of reasons - more methods of getting HDTV into my house the better and competition is always nice.
If this sticks to adding a second signal at the same frequency at a different time offset, doesn't that make it time division multiplexing? Correct me.. I'm trying to remember like 15 years ago ;P
Darwin Hawking Blackmore
Indeed, however as it stands atm. UK Digital Cable = Virgin Media
No, because TDM would mean the two data streams were transmitted sequentially in allocated frames in one signal. MIMO transmits two signals simultaneously, and the receivers have the job of using phase information to separate them out.
So I don't get the issue - DVB-T in the UK has 8 MHz channels. They have access to 22 Mbps using COFDM even at the most reliable QAM level.
Here in the U.S. we have 6 MHz channels for our terrestrial 8VSB DTV, we have 19 Mbps, and HD works just fine, thanks.
My understanding is that Freeview was SD only because the set-top-boxes had to be cheap.
There are more than 60 channels available in the spectrum, but there are NOT ever 60 TV stations.
Give every tv station 3 channels each so they can have a HD channel, SD channel, Repeat Channel. Along with that there are sub channels for each of those, but
thats like a much easier solution, which costs zero dollars.
But I forget, in this world, no one likes solutions that cost $0, because then no one can feed of the system and make more money out of it.
Liberty freedom are no1, not dicks in suits.
OT: There's another downer with these new type of entertainment boxes - something touched on in Dragons' Den recently. Many of these Freeview boxes eat 100% or near of their max power take even in standby. It got me thinking, why is that? These are effectively small computers decoding over-the-air MPEG - they need to boot up, test & calibrate, and many don't appear to have sufficient component sleep ability. Once again, it's a trade-off - a few seconds of boot-up time coming out of standby vs sucking more power than it needs. They went for the latter. The other digiboxes are not doubt the same, I know that if I crash my cable box I can knock it into standby and the display merrily goes on & off but the box remains crashed. The 'standby' appears to operate the front display and nothing more.
http://www.tv2me.com/
They already sell boxes that tansfer HD signals from 1 location to another. Yes, the context is different but the technology is already on sale.
I am absolutely certain that any of the 802.11-pren and 802.11-draftn implementations that use the Airgo Networks (now Qualcomm) chipsets do true spatial multiplexing with multiple input and output antennas (MIMO), NOT just "fancy antenna selection" as you put it. I know because I contributed to the design of their first-gen RX implementation. They've never NOT done it. Of course, the chip also supports non-MIMO modes for back-compatability with older access points.
I am almost as certain that other implementations use MIMO as well. But of course since I wasn't on the inside I cannot say. Still, it's pretty much the only way to get more than 54mbps over 802.11 without channel bonding.
MIMO, sounds too much like GIGO.
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People with UIDs that low don't just not read the article, they don't read the summary either. The longer you're here in fact, the less you read. The limiting case is the editors who can't read anything anymore, not even the warning labels on stuff. Which explains the high turnaround of editors we see.
I'm not sure I should even bother to type this, since your UID is much lower than mine.
If you read this far in fact, I'll reward you with this top tip: Avoid the "hard to open" jars in the cabinet in your bathroom. They are not candy.
echo -e 'global _start\n _start:\n mov eax, 2\n int 80h\n jmp _start' > a.asm; nasm a.asm -f elf; ld a.o -o a;
Yeah, get rid of the shopping channels (never watch then) and the +1 channels (who needs to watch Friends an hour late?) and the there should be enough space for some HD.
Of course we will have to buy new boxes to watch HD anyway.
One of the interesting points aboutthe ITV digital debacle was the fate of the World origami championships. ITV Digital di have the rights but they folded. It was left to Sky to put it on paper view.
Although there's been a relatively high take-up of Digital TV in the UK (about 19 million homes roughly split 45%/45%/10% DVB-S/DVB-T/DVB-C depending on whose figures you believe) there have been two distinct driving factors for this - one is consumer demand for a wider choice of channels and the other is government determination to shut down analogue terrestrial TV in order to make money from the spectrum space by auctioning it.
To a first approximation, the technologies are each presently operated by a separate single supplier: DVB-S by Murdoch's Sky TV, DVB-C by Virgin Media (formerly NTL/Telewest) and DVB-T by Freeview (a consortium in which the BBC is a main player).
The principle advantage of "Freeview" is that it provides a very simple marketing message: you buy a £30 box which plugs into your existing aerial (mostly) and TV and that's it. In exchange you get both a wider range of channels and protection against the "analogue switch-off".
That message is getting progressively less simple, though. Freeview has subscription channels (entertainment and sport) as a result of the legacy of the collapsed On-Digital/ITV Digital service that preceded it (needs box with a card slot). There is also some limited PPV (mainly porn) which interestingly requires no card but an access code obtained by telephone.
Furthermore, there is a significant demand from broadcasters for additional Freeview slots - recently there have been auctions for broadcast rights which have reached millions of pounds per channel. In order to prevent interference to analogue signals, the number and power of DVB-T channels is artificially limited at present leading to a seriously-constrained supply of channels. Partly this has been addressed by improving the encoding and stat-muxing process, partly by compromising on quality (some services average below 2MBit/sec video rate) but basically the available spectrum is full. Sky TV (which is also a content provider as well as operating a DVB-S platform) has 3 channels on Freeview which it has contemplated pulling and replacing with 4 MPEG-4 channels which existing Freeview hardware cannot receive in order to increase the number of channels it can provide on DVB-T.
So, despite the current constraints, DVB-T has been a success. The danger is that the capacity constraints will cause the platform to fragment as different content-providers try to deal with this and the consequent increasing costs by invoking a range of incompatible technical solutions and payment mechanisms.
It was originally believed that the closure of analogue TV would enable a significant increase in the coverage and capacity of Freeview, but the government has since made it very clear that it intends to auction off the spectrum space rather than simply re-allocate it to Freeview as it becomes available. Consequently, the future expansion of Freeview is in doubt and the BBC in particular is concerned that it might only be able to provide HD programmes on DVB-T by sacrificing other channels.
This technical research by the BBC is very much a desperate bid to retain the future viability of DVB-T, in which it now has a significant stake, in the face of current government policy. So don't assume it's the BBC's preferred option: the recent DVB-T HD trials used rather more mundane and easily-deployable technology.
At the same time, there are consultations on switching off FM radio (about which there is a serious outcry as the DAB alternative is also seriously constrained by limited spectrum space meaning that the audio quality of FM is actually better; one possible consequence of which is that FM is switched off and DAB is enhanced incompatibly with current receivers) and trials replacing AM radio with DRM (that's Digital Radio Mondiale in this context!).
In almost 90 years of public broadcasting there has historically been only one major technology shift in Europe that has obsoleted consumer equipment - the move to colour TV (which led, after a decent interval, to the shutting down
No, don't get rid of the +1 channels. I can not get the standard channels, and have to watch +1. :(
Indoor aerials suck.
Wow, I should not post when knackered.
thats not a low user id......
Yeah, get rid of the shopping channels (never watch then)
Thing is that these along with the quiz (lottery) channels are likely to cost nothing to the broadcaster, possibly they even pay to be broadcast...
As the article says, a far simpler solution to the badwidth issues of freeview would be to ditch the huge number of junk channels and use the bandwidth to provide a HD signal for the ones that people actually watch.
Quite right. Why do I have to put up with that BBC1/2/3/4, ITV1/2/3, Channel4 and Five junk when I never watch it?
== Jez ==
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The move from analogue to digital has been bad enough. Many people have had to change their aerial, TV and purchase a box. I doubt many people will be willing to do this again anytime soon.
The tech savvy people might be willing to do so, therefore if this happens it should be in parallel to the existing system.
HD will be good news, but only if they don't compress it too much. The compression needs to deal with motion well too for sports events.
Isn't this called *multiplexing*?
We could start by only having one channel that plays friends and scrubs all day, instead of three.
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I wouldn't put it down too much. Freeview is extremely successful in the UK due to some shops managing to cut the prices of boxes to 20-30 pounds these days - plus, all new tvs have had the boxes built in for a long time. It's a very promising transition.
Take one HD channel to transmit scaled down versions of all available channels for some given area. Keep one tuner constantly on this channel. When switching, briefly show the scaled down version while the main tuner switches over.
Hey, maybe you could also use that channel as a video channel guide - simultaneously see all available channels, tiled onto one screen in low-res, then pick the one you want...
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Which would free up a channel for all the various flavors of "Law and Order" and another for "CSI-wherever", and I could program out both.
Of course what I really want is for anything to do with Donald Trump (and I mean anything, including any mention of him by others) to be confined to one particular channel, and then I can install a notch filter right where the cable hits the grounding block at the demarcation point.
I see even classic Slashdot is now pretty much unusable on dial up anymore.
Harold: Hurry up Martha, the cricket game is coming on the tellie
Martha: Oh Blimey Harold, you and your matches are gonna be the death of me.
Harold: Edwina, darling, are you ready for the game?
Edwina: Yes, Father, just climbing into position now.
Harold: Okay Martha, a little farther up and to the left..
Martha: (Mutters something unintelligible)
Harold: Now Edwina, my little flower, if you'll hold your antenna straight and turn ever so slightly towards the south, that would be lovely.
Edwina: Certainly Papa.
Harold: Martha! You old cow, I thought I told you to hold that bloody antenna still!
Martha: That's it Harold, I've had it. If you want anything more to do with this bleedin NEMO-- MINI-- NINI or whatever it is business, you're going to have to get up off your bloody arse and do it yourself!
Harold: How many times do I have to tell you, its MIMO!