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Print 10 comment(s) - last by Kary.. on Oct 22 at 10:49 AM

Chairman Martin gives tentative stamp of approval

FCC Chairman Kevin Martin weighed in his support for “white space” wireless devices, allowing unlicensed (e.g. free-for-all) usage of vacant Digital TV channels.

Backers of the white space wireless call it “Wi-Fi on steroids,” noting that TV frequencies, which generally cover the 55 MHz to 800 MHz chunk of wireless spectrum, excel at broadcasting signals over a large distance and penetrating obstructions – a difficult feat for today’s 2.4 GHz networks.

White space wireless faces stiff resistance from TV broadcasters concerned about signal interference. Unlike analog, where low-quality signals produce an acceptable-but-snowy picture and image ghosting, digital signals will cut out entirely at worst, or exhibit heavy distortions at best.

The response, so far, has been to develop “smart” wireless transmitters that limit themselves only to DTV channels available by a given margin, and actively scan the frequency to determine what areas are free. To that end, the FCC recently wrapped up Phase II of its test program for prototypes, and the results went so well that backers received Martin’s endorsement.

An executive summary of the test results (PDF), posted on the FCC website, notes that “fixed location” white-space devices are already set to be allowed into the TV spectrum in February 2009, immediately after analog TV signals cease broadcasting. Instead, the FCC’s testing pertains specifically to portable devices, such as laptop Wi-Fi cards, that roam from area to area. The “smart” features of these devices work in a variety of ways: open channels are could be located through a TV-style auto-scan, and/or through a nationwide database of TV channel assignments.

White space-scanning technology isn’t yet perfected, however, although the FCC certified that it officially reached “proof of concept” status. Prototype devices submitted by five companies – Adaptrum, the Institute for Infocomm Research (I2R), Microsoft Corporation, Motorola Inc., Philips – were able to scan the TV spectrum in anywhere from 0.1 to 130+ seconds per channel, and on average were able to detect a “clean” channel’s availability on signals as weak as -126 dBm. Real world testing didn’t fare as well, however, as devices both required a stronger signal and exhibited a higher rate of false positives and – more importantly – negatives.

A false negative would mean the auto-scan detects an occupied channel as vacant – a scenario that TV broadcasters and wireless microphone manufacturers deeply fear. It’s a scenario they fear so much, in fact, that some have gone so far as to request a two-channel buffer on either side – meaning 5 consecutive, unoccupied channels – for a device to determine a channel as “empty”. The technology’s backers say 5 channels are excessive, and fear it might cripple the tech’s usefulness.

White space’s backers include heavy hitters like Microsoft and Google – who offered to host the channel database – while its opponents include the National Association of Broadcasters and Shure, Inc, makers of wireless microphones used at concerts and sporting events.

The transition to digital TV means a substantial overhaul to the U.S.’ wireless spectrum allocations: with the dust just beginning to settle over the hotly-contested $19.6 billion 700 MHz band, manufacturers of devices for the overly-crowded 800 MHz, 2.4 GHz, and 5.8 GHz wireless bands will receive a much-needed boost to the amount of spectrum available to them.

The FCC is scheduled to vote on whether or not to allow personal white space devices November 4.



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This seems like it can only turn out bad
By the goat on 10/20/2008 7:28:44 AM , Rating: 3
Fundamentally it seems to me that the TV spectrum should be reserved for TV transmissions. Putting other signals in there will result in interference with broadcast channels. Even with a two open channel buffer.

Imagine I live on the edge of station Wxxx. I can just barely lock onto the signal. My neighbor (who lives further from Wxxx) can not lock onto the signal. So he sets up his network to operate on that frequency. Suddenly I can no longer maintain a stable lock on Wxxx even though at the neighbor's house it is an open channel.

Also what happens when a city with thousands of these networks operating on "open channels" gets a new TV station? Is there a way to force all the devices to rescan? Sounds like the new TV channel would have to broadcast over the interference until the device's owners get around to reconfiguring them.




RE: This seems like it can only turn out bad
By Kary on 10/20/2008 12:01:11 PM , Rating: 2
As I understand it, the data Google and Microsoft hope to host is geographical data of what stations are where which will be dynamically updated and used to determine what is white space and what isn't.

In rural areas this would be extremely nice. We have 4 TV channels (2 are actually on the same digital channel) where I live with maybe 5 more you can get with a large antenna. Out of a possible 99 => 6-Mhz "channel slots"?

Some areas we have 2 possible ISPs, but in most areas we have Zero.

So, while I agree the TV spectrum should be reserved for TV I also don't see a reason to throw away the leftovers.


RE: This seems like it can only turn out bad
By the goat on 10/21/2008 7:14:45 AM , Rating: 2
quote:
Out of a possible 99 => 6-Mhz "channel slots


Where did you get 99 channel slots from? There are only 68 broadcast TV channels: 12 VHS and 56 UHF. The 99 channels are for cable TV which does not use the same frequencies as broadcast.


By Kary on 10/22/2008 10:49:59 AM , Rating: 2
I couldn't find the number of channel slots so I guessed and put a ? after it to show it was a guess.

12VHS and 56UHF. Can you tell me where you found that?

(The exact number wasn't important to my point, 99 or 68, if there are only 10 channel slots used that still alot of waste.)


RE: This seems like it can only turn out bad
By Ammohunt on 10/20/2008 1:55:49 PM , Rating: 2
Open air transmission of TV signals is antiquated(Digital or otherwise) and in my opinion a waste of valuable spectrum. Switch it over entirely to data and multicast stream TV via the resulting wireless network.


By Spuke on 10/20/2008 2:36:28 PM , Rating: 2
quote:
Switch it over entirely to data and multicast stream TV via the resulting wireless network.
Because wireless doesn't use open air transmission.


By the goat on 10/21/2008 7:18:43 AM , Rating: 2
quote:
Open air transmission of TV signals is antiquated(Digital or otherwise) and in my opinion a waste of valuable spectrum. Switch it over entirely to data and multicast stream TV via the resulting wireless network.


So we should have to pay for access for something that has been free for the last 50 years? That makes sense. Or is this new wireless network going to be free? If it is free I doubt it will support multicast streaming multiple high definition audio/video signals to millions of points at once.


By toyotabedzrock on 10/21/2008 4:28:18 PM , Rating: 2
I think they are planning low power consumer devices, that would only affect a very small area at worst.

The devices are going to be designed to rescan the channels surrounding its own in use channel often so that if need be it can jump to a diff channel.

The database is just a way to provide a quicker initial scan, basically hinting where there might be open unused spectrum.


Is it just me...
By Ordr on 10/19/08, Rating: -1
RE: Is it just me...
By mmatis on 10/19/2008 7:12:03 PM , Rating: 5
Actually, this is one of the few this the government OUGHT to have a hand in. Without frequency licensing, how would you know where what radio and TV stations were? Who would keep them from broadcasting on top of each other? In fact, that's one of the issues which may stop this from happening. If there is sufficient cross-talk between this frequency and the other adjacent frequencies operated by other users, Uncle ain't likely to let this proceed. But then I guess you could always go with "Whoever has the biggest transmitter wins!" Sorta sucks, though, when two or more stations fight for the same spot and you can't hear any of them. But then I guess you city boys probably haven't seen that.


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