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."

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[DaAdder]

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.

Fascinating technology, but useless for Freeview

[Andy_R]

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.

Re:The upgrade cost means it will never happen

[evilviper]

Somehow, I doubt anyone will go for buying a new box and ariel just for the lucky minority to have HDTV.

You aren't being forced to switch all frequencies to MIMO. You could just as well leave half the spectrum in-place for standard definition, and just broadcast MIMO on the other half.

Anyway, if you are going to have a new box, why not move to MPEG4 as well?

The PDF mentioned this test was done using h.264.

Re:Complete Rubbish

[DrMindWarp]

The BBC paper isn't rubbish. The Slashdot summary mangles things as usual so you need to go to the original source (dated December 2006 incidently). Even the paper itself says that this isn't news. The same frequency is used for two transmissions at but at different polarizations. So the noise floor is not raised to the levels that you might suggest (although originally orthogonal, reflections and refraction will cause some problems). Theoretically there are two independent channels and experimentally it works.

Re:Fuck DVB-T

[Anonymous Coward]

You can't blame DVB-T for picture quality issues unless you've got problems with radio interference. DVB-C/T/S is just the medium.

DVB-T in Australia transmits the SD TV (non-HD) channels at a rate of about 3 Gbyte/hour, which should provide a picture at least as good as your average DVD.

Assuming the realtime MPEG-2 encoders at the TV stations aren't junk.

Just like The BS of BluRay or HDDVD

[Lumpy]

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.

Re:What is MIMO

[markov_chain]

Pretty close, but not quite. MIMO doesn't rely in observing the combined signal at different times, but on the fact that in a multipath environment, there is some independence between an antenna at one location and one located a small distance (on the order of only one wavelength or less) away.

Yes, quite. The independence between antenna pairs arises from delay spread, caused by signals traveling different distances.

In some cases, the path lenghs of these signals are such that they all add in-phase (constructive interference) and the signal is strong. In other cases, they are out of phase and cancel each other (destructive interference) and you get static.

So they do arrive at different times. In your two examples they arrive either in-phase, or one half cycle apart in time. ;)

and each element of the matrix is the gain between the transmit and receive antennas

Usually the coefficients are complex, which means they represent both gain (or should I say attenuation) and phase distortion.

A true MIMO system can analyze the paths between all transmit and receive antennas, and effectively transmit different data on each path.

Not quite. This would imply that in a NxM system, we could transmit different data on N*M paths, which is not the case. Upper bound is min(N,M).