White spaces news
When the DTV transition happens in Feb. 2009, channels 2 through 51 will remain allocated for television transmission. Few of the nation’s television markets actually use 49 channels. Indeed, most use less than half of that number. The “white spaces” are these unused television channels, which amount to approximately 300 MHz of frequencies. According to Blair Levin, “[e]stimates vary, but most of the population (between 73% and 97%) lives in areas with access to 24 MHz or more of white space. Rural areas in particular, have a great deal of white space as they generally have fewer television broadcasters.” Rules for the “white spaces” are now on the Commission’s agenda.
This is a proceeding about almost 300 MHz of spectrum (and all the fighting over the 700 MHz C Block concerned just 22 MHz). It will be in “swiss cheese” (non-contiguous) form, but there will be a great deal of it.
Today, with Congress in recess, leaving less room for last-minute-Lucy-with-the-football lobbying gambits, the FCC appears to be poised to release a report saying the white spaces can be used without necessarily causing interference to existing broadcasts.
There are still many questions to be answered -
(1) Will permitted uses of the white spaces have to be licensed, or can they be unlicensed? Unlicensed uses could unleash the creation of an entire ecosystem of new devices and new uses, as we’ve seen in the “junk band” use of wireless hotspots. With machines making their own etiquette decisions (subject to power-level certification by the FCC), the capacity of the white spaces (potentially enormous) could be used far more effectively. This could provide a much-needed end-run around last-mile bottlenecks, particularly for mobile and rural users.
(2) Will devices have to be fixed, or can they be portable?
If portable devices are allowed, a much larger market for these new gadgets will be created - which means they’ll be cheaper (because they’ll be sold in enormous numbers), which means that innovation will move much more quickly, which means many more interesting mobile uses will be possible. You can’t use a fixed device in a car moving at 60mph down the highway.
(3) What kind of spectrum sensing will be required?
Will devices be permitted to carry out their own sensitive etiquette so as to avoid interference? Or will they need to check against authoritative databases and/or send out foghorn-like “beacons” so that existing actors will know they’re interested in transmitting? Google has proposed a hybrid solution that includes the use of databases and beacons (and protects those holy wireless mics); other groups are more interested in pure spectrum sensing.
More coming, but this is a very interesting first step.
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3 Responses to “White spaces news”
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“The “white spaces” are these unused television channels, which amount to approximately 300 MHz of frequencies.”
Not quite: There is only 288MHz of post transition TV broadcasting spectrum, both VHF and UHF. Given a nationwide average of approximately 70% usage by all types of Part 73 broadcasting operations, this leaves roughly 84MHz of white spaces. As the only spectrum being considered for “white space devices” is channels 21 - 36 and 38 - 51 (180MHz), with only about 25% on average not used by Part 73 broadcasting operations, this leaves about 42 - 48MHz, or about six to seven channels worth of white space on average, without weighting for the 13 MEA’s.
“This is a proceeding about almost 300 MHz of spectrum (and all the fighting over the 700 MHz C Block concerned just 22 MHz). It will be in “swiss cheese” (non-contiguous) form, but there will be a great deal of it.”
If you’re talking about OET 04-186, the spectrum in question is only channels 21 - 36 and 38 - 51 or 180MHz.
Henry Cohen
Production Radio Rentals
I don’t agree. I understand that the typical DMA has only between 7 and 8 full power stations in operation (out of 49). So there’s a lot of spectrum left. I suppose if you assume that all stations continue broadcasting on both their analog and digital channels (something that won’t be true after Feb. 17, of course) AND that all the channels next to those channels aren’t available (something that isn’t true either), you could constrain the amount of spectrum available - but those are counterfactual assumptions.
According to a 2006 New America/Free Press study, the share of the DTV band (channels 2-to-51) that will be vacant after the February 2009 turnoff of analog transmission ranges from 30 percent or more in the most congested, coastal markets (e.g., Trenton N.J.) to 80 percent or more in small town and rural markets (e.g., Fargo N.D.)
So I stand by my numbers.
As I indicated previously “post transition TV broadcasting spectrum”, meaning I considered the shut down of full power analog transmitters. But what you must remember is there are other Part 73 transmitters than full power stations that will operate post transition: Translators, boosters and LPTV. Further, the DTV Border Fix Act of 2007 permits full power NTSC within 50 miles of the Mexican border to continue operations until 2014.
Additionally, since white space devices are only going to be permitted to operate in channels 21 -36 and 38 - 51, that’s only 180MHz of spectrum before TV transmitters are considered. Even if one were to look at all VHF and UHF post transition Part 73 broadcast spectrum (why?), that’s only 288MHz. Using NAF’s number of 80% availability in rural areas (which is somewhat disingenuous as most of the population, and thus most of the whitespace use, will occur in major metropolitan and surrounding areas), that leaves 230MHz.
Last time I looked, 180 and 230 is noticeably less than 300. (Must be that ‘new’ math thing.)
Henry Cohen
Production Radio Rentals