A few months shy of seven years after I first proposed the idea that has become known as (television broadcast band) "White Spaces", a report by the FCC validates the concept. I'm kind of proud that I was so far ahead of the curve on this particular implementation of Broadband Wireless Internet Access.
I told this story in a previous article, but in a different context, so perhaps it bears "reprinting" here.
My article, retitled to Wireless Smart Radio, Heavy Lobbying Would Bring Wireless ISP Band and poorly edited, appeared in Boardwatch Magazine Online - then at URL http://www.ispworld.com/boardwatchonline/2002/jan02/technology-wireless.htm. Boardwatch is no more, and Light Reading, the subsequent owner of boardwatch.com removed all the former content, but fortunately this article, at least, is available on the wonderful Internet Archives.
In a sense of Deja Vu... only in the last few months have Wireless ISPs actually begun to rally to this cause, though nowhere near the unified front that I recommended they would need to assume.
Note that my proposal/article, I "start" at Channel 14, since all the Digital Television conversion proposals at the time stated that as part of the transition, Television Broadcast Channels 2-13 would also be surrendered because their spectrum is far more valuable for communications use. Unlike Channels 14 and up, Channels 2-13 are not continuously located in the UHF band. Apparently the Television Broadcasters were able to maneuver themselves into retaining Channels 2-13.
I've subsequently learned that Channels 14-20 are used in some urban areas for public safety two-way radio communications. Such usage would be much more difficult to detect than television broadcasting, so unless the Smart Radio can be made "smart enough" to detect such usage, I may remove Channels 14-20 from consideration for license-exempt sharing. In my research at the time that Channels 52-59 would also be reallocated into the "Lower 700 MHz Band". My last mea culpa is that Channel 37, while allocated, is reserved for Radio Astronomy nationwide and thus no transmissions of any kind are allowed there. So, now my math on the available spectrum is Channels 21-51, minus Channel 37, equals 29 channels, for a total of 174 MHz of Television Broadcasting Spectrum - 512-608 MHz and 614-698 MHz, that is potentially available for license-exempt communications use. That's an incredible amount of spectrum, especially given that most... and often all of that will be available in rural areas where the propagation characteristics of this spectrum will be the most useful.
Below is the text of that article, as it appeared in Boardwatch Magazine Online, January, 2002.
Technology
Wireless Smart Radio, Heavy Lobbying Would Bring Wireless ISP Band
Operating in the 2.4 GHz band can be a difficult challenge for many ISPs because of interference issues. An oft-mentioned "cure" for such problems is reserved spectrum for wireless ISP (WISP) use. The technology is there, the obstacles are political. Broadcast lobbying forces, such as the National Association of Broadcasters, in Washington would fight the proposal, and it would take a united effort by service providers to push it to fruition.
The idea of a WISP band has merit and is achievable, especially in the context of local ISPs providing a cost-effective service to address the digital divide issue in non-metropolitan areas. The basic idea is to share, strictly on a non-interference basis, unused television broadcasting channels 14 to 59.
Channels 14 to 59 are the 470-746 MHz range and contain 276 MHz of contiguous spectrum reserved for television broadcasting. (Channels 2 to 13 and channels 60 to 69 are already slated for reallocation.) In contrast, the 2.4 GHz band is only 83.5 MHz.
Such a sharing scheme would only be possible with the emergence of a new type of radio - a smart radio. A WISP smart radio (WSR) is programmed to survey the 470-746 MHz spectrum. On any television channel where transmissions are heard, that channel is automatically "locked out" from being used by the radio.
A smart radio can make such a decision (whether or not there is a potential interference problem on a channel) in milliseconds, versus humans making the same decision in weeks, months or years.
One of the prime reasons for trying to make use of 470-746 MHz is that it has good penetration characteristics (trees don't stop signals at this frequency). Reasonable transmission power levels at 470-746 MHz are possible, with reasonable safety. A maximum power limit of 10 watts should be ample.
The technology to build a WSR certainly exists. Frequency Hopping Spread Spectrum (FHSS) modulation seems most applicable to WSR, as it can simply "hop over" television broadcast channels that are in use. I further propose that WSR be designed as a consortium, and standardization between manufacturers would insure interoperability and drive down costs.
Generating Revenue and Acceptance
There is a very real expectation that any new use of spectrum must generate some income for the government. A revenue generating approach that seems applicable to WSR is for a one-time "spectrum tax" applied to the final purchase price of each WSR.
The more use made of spectrum (the more units sold), the more government revenue generated. The expense is directly proportional to use, and the expense is incurred only after the additional business is generated.
The main obstacle in developing WSR is not technical. Television broadcasters and their industry organization, the National Association of Broadcasters (NAB; www.nab.org), are powerful forces in Washington, D.C. Any non-broadcasting use of television broadcasting spectrum will be fiercely resisted.
Wireless ISPs could overcome this obstacle with effective representation in Washington, D.C. To accomplish this, the WSR will require time, sustained effort, financial support and experienced lawyers. The Wireless Communications Association International (WCA; www.wcai.org) fulfills many of those requirements, and is an established, effective presence in Washington, D.C., representing wireless broadband service providers and equipment manufacturers.
The WCA certainly doesn't currently have budget to tackle a project as ambitious as WSR, nor the mandate. But if there were a groundswell of wireless ISPs joining WCA, then it could happen. If you are interested is joining the grass-roots effort, contact the WCA and find out how you can contribute.
One last suggestion is for manufacturers to build in the capability for WSR to work at 420-450 MHz with some reasonable substitution of components, with instructions on such a modification available only upon presentation of a valid amateur radio license. I, and my fellow 682,218 U.S. amateur radio operators, would greatly appreciate it.
(end of January, 2002 Boardwatch Magazine article)
The unedited version of the article (a bit longer, a bit richer in detail), as I submitted it to Boardwatch, appeared in Issue 004 (PDF) of my newsletter FOCUS On Broadband Wireless Internet Access, titled A Modest Proposal - My Last Boardwatch Column.
Back to late 2008...
The FCC's "TV White Space Phase II Test Report" - Public Notice (PDF), Executive Summary (PDF), and (full) Report (PDF) are now online, as well as eight appendixes to the report, at www.fcc.gov. (Those links will scroll off within weeks; the FCC doesn't do permalinks. I wish they published their main page in blog format with RSS...)
What's most important to understand about the FCC's test results is that they validate the concept of license-exempt, non-interference usage of vacant television broadcast spectrum. The devices tested were purely prototypes, designed to prove to the FCC that the concept that a license-exempt device could reliably detect licensed / higher-priority usage of the television broadcast spectrum and thus "choose" not to transmit on television broadcast channels that are in use, either by wireless microphones or television broadcasting.
While the National Association of Broadcasters, the wireless microphone manufacturers, major users of wireless microphones (Broadway, major sports events, etc.) will raise a hue and cry and question the validity of the FCC's results, to me it's now irrevocable that there will be license-exempt usage of vacant television broadcast channels. The concept has now been proven - not perfectly... but more than well enough.
What comes now is for the FCC to now propose rules for the technical and operational aspects of "white space" (I might was well bow to the popular nomenclature...) devices and systems. The rules will be strict, and onerous, and expensive to implement... at first. And that's OK.
That will get devices out there in the field. There will be glitches. But mostly there will be successes. And over time, two things will happen.
The first is that as volume, and competition, and technology inevitably improves, the performance of white space devices and systems will improve, radically. That's what I've come to call The Darwinian Effect of License-exempt Wireless. The vendors, users, and perhaps by then industry associations will lobby the FCC to relax the rules such as (likely required, at first) geolocation databases. If the devices can reliably detect when they would interfere with a higher priority usage "on the fly", geolocation databases aren't needed.
But the second point is perhaps more radical, but no less irrevocable - that there will be further consolidation of television broadcast spectrum, and eventually a cessation of television broadcasting as we know it. Here's a critical point that the NAB glosses over because it's something that they don't want the public to know - the reason that television "channels" are so "spread out" is that (analog) television receivers were designed so poorly (partly because the "vacuum tube" electronics technology of the 1950's and 1960's, and partly an artifact of making television receivers cheap) that when television broadcasts were transmitted on adjacent channels in the same geographic area, television receivers weren't "selective" enough to receive the transmission on only one channel - there would be "interference" within the television receiver! But with the advent of digital television tuners, and now the much-improved receivers inherent in the conversion to Digital Television Broadcasting, the adjacent channel issue is largely moot... entirely moot for the 90+% of the television viewing population that receives their television signals from cable television, digital television satellite, or... the Internet.
So we'll see yet another round, or two, of reallocation of television broadcast spectrum like with the reallocation of television channels 52-69 into the various "700 MHz" bands (hopefully better effect - that they'll actually get used to provide services instead of the current situation of 700 MHz spectrum being largely "warehoused" ).
But here's an even more radical idea... that the license-exempt usage of white spaces will prove to be so popular... so useful... so intensively used... so economically beneficial, that such the license-exempt usage will eventually "trump" the current "higher priority usages", and the FCC will bow to that reality and the license-exempt usage will become the priority usage when television broadcasting eventually ceases or at least further consolidates into the lower portion of the remaining television broadcast band.
Oh, and don't feel any pity for the wireless microphone manufacturers. They're dragging their heels in moving to far better technology because of their lucrative and demanding current high-profile customers and their comfort with their current (but archaic) technology. They'll eventually be forced to transition to a portion of spectrum and technology that lets the microphone systems themselves coordinate their usage and insure non-interference such as Ultra Wideband or 60 GHz; The Darwinian Effect of License-exempt Wireless applies equally to wireless microphones.
By Steve Stroh
This article is Copyright © 2008 by Steve Stroh except for specifically-marked excerpts. Excerpts and links are expressly permitted (and encouraged).
This article was written and posted via Broadband Wireless Internet Access (BWIA) ; Sprint Mobile Broadband service using a Sierra Wireless 595U USB modem - 1xEV-DO Rev. A on a MacBook Pro laptop.
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