Brian's Brain

The last time I discussed the 'white space' spectrum scuffle in detail was last October, as part of my Audio Engineering Society Convention coverage and, specifically, as it related to UHF- and VHF-transmitting wireless microphones. The issue was front-and-center again two weeks ago at NAB, as these snapshots I took during a presentation given by Shure's Chris Lyons make clear:

Chris emailed me his entire presentation yesterday, which I've posted as a 681 KByte PDF for your perusal. He also provided several other PDFs which I've loaded online:

• The Microphone Interests Coalition's response to Google's recent spectrum-sharing proposal (19 KByte)
• A UHF spectrum map (18 KByte), and
• A summary white paper (39 KByte)

Keep in mind as you review the material, of course, that it reflects only one side of this contentious topic. On that note, I'll related one interesting past datapoint that Chris shared during his presentation, not directly documented in the PDF. In the early days of wireless microphones (which post-dated NTSC television), the broadcasters were concerned that mics might interfere with television reception. Therefore, the FCC drew up plans for a nationwide database of wireless microphone users and the specific channels their equipment inhabited so that, if a television viewer complained about poor reception, the source of the offending interference could be identified by the local network affiliate.

It was quickly determined, however, that this was a moot point; television signals were so strong that they overwhelmed any coincident-spectrum wireless microphone transmissions (not to mention that wireless microphones, by virtue of their portability, would only rarely be in use at their registered-user addresses). It's a bit amusing, given this historical precedent, to now see the 'shoe on the other foot', as the saying goes. Pre-existing wireless microphone vendors are now up in arms about upstart white-space equipment providers coexisting in 'their' spectrum. Admittedly, given that the broadcast signal strength of both 'competitors' is more equivalent this time around, the argument carries greater validity, but still...

I'd planned a detailed post-NAB post (pun intended) on 'white space', but yesterday I happily discovered that Electronic Business contributing editor Tam Harbert already covered a lot of the same ground I'd planned to traverse. I strongly encourage you to peruse Tam's writeup, for which I'll only offer a few additions and clarifications:

• In my mind, the pending NTSC-to-ATSC transition is only peripherally related to the 'white space' market opportunity. In fact, as Chris Lyons' material points out, the recently concluded 700 Mhz auction will result in less overall UHF spectrum being available for both wireless mics and 'white space' devices. On the other hand, stations will no longer be broadcasting on both NTSC and ATSC channels (as is the case in this time of transition), making more post-700 Mhz-auction spectrum a 'white space' candidate on a per-region basis. Also, because the ATSC signals' spectrum usage will on average be more precisely bounded than in the NTSC past, more in-between-channel spectrum will be a practical 'white space' candidate.
• 'White space' detractors such as the NAB and CTIA are now cleverly suggesting to the FCC that it auction off the available 'white space' spectrum. Such a proposal is, of course, compelling to a revenue-strapped government that just raised $19.6B in a similar auction 1.5 months ago. But, aside from the fact that it runs counter to the fundamental free-when-available point of the 'white space' coalition's vision, the resultant bureaucracy and region-by-region spectrum specificity would both dramatically slow the rollout and limit the ultimate usability scope of 'white space' equipment. Which, I'd argue, is the NAB and CTIA's fundamental aspiration.
• Hospital telemetry systems are also existing 'white space' squatters, and since not all of them employ UHF channel 37, even Google's recent coexistence proposals won't solve this particular problem. 'My microphone won't work', with all due respect to Shure, isn't near as compelling a pitch as 'my patients' heart monitors have failed'. Frankly, therefore, I bet Shure's happy to have the hospitals on its side.
• Don't get me wrong; my personal to-date experience with supposed spectrum-nimble gear that avoids other existing transmitters is, best case, 'indeterminate' (I could use harsher words). However, as an excellent writeup in April's Broadcast Engineering points out, existing spectrum users might want to consider something other than a purely defensive strategy. They just might benefit from the spectrum technology enhancements that the 'white space whipper snappers' are proposing, too.

I'll close with the inquiry hinted at in this writeup's headline. With my late May microprocessor cover story filed as of a few weeks ago, I'm now figuring out what I should write about for my early-August cover story slot. Having followed the 'white space' debate for quite some time now, I'm tempted to give the topic an in-depth technical print treatment, in spite of the fact that a FCC ruling on the technology isn't due until October at the earliest.

On the one hand, EDN generally tries to focus its coverage on here-and-now technology that will influence your current (and near-future) design activities. On the other hand, a favorable 'white space' ruling will have a profound impact on PAN, LAN and WAN wireless communications going forward, and 'white space' backers suggest that they'll be able to turn vision into products in fairly short order, both factors suggesting to me that a goodly number of you are already closely following the 'white space' debate at least on a conceptual level, if not already working on functional prototypes.

So when do you think I should devote precious EDN print pages to this particular topic? Now? Later? Or never? Thanks in advance for your observations and suggestions!