The Audio Engineering Society Convention: Spectrum Auctions And White Space Matter Mightily To Wireless Mics

As a quick Google search will assure you (assuming you even need assurance, that is), I’ve long followed the pending NTSC-to-ATSC analog-to-digital television transition in the United States, from a variety of viewpoints:

• The Broadcast Flag fair-use threat
• Required infrastructure revamps, both by broadcasters (cameras, mixers and editors, transmitters and antennas) and consumers (tuner-inclusive displays, standalone settop boxes and other acquisition options)
• Variances in digital reception characteristics versus the longstanding and familiar analog baseline benchmark
• etc.

As part of this transition, and as I specifically mentioned at the beginning of this year, a FCC plan known as Core Spectrum will phase out UHF channels above 51, among other things freeing up 60 MHz worth of ‘upper band’ spectrum that the FCC will subsequently allocate to the winner(s) of what’s expected to be an extremely lucrative bidding war (aka the ‘700 MHz wireless spectrum auction‘).

One product category that’s significantly affected by the Core Spectrum channel reassignment and more general NTSC-to-ATSC changeover, but which (based on my observation of online and print editorial over the years) has been woefully under-represented in the debate, is the wireless microphone industry that was present en masse at the recent AES Convention. Many wireless mics broadcast on UHF and VHF bands, at precise ‘white space‘ frequencies in-between television channels’ spectrum as well as within a particular channel’s spectrum (only if, of course, that particular channel isn’t already being used by a television station at a given location).

At minimum, wireless mics that transmit on UHF frequencies above channel 51 will (as is the case with their television broadcast brethren) need to phase out by early 2009. That particular issue aside, it might seem at first glance that the NTSC-to-ATSC transition would be a good thing for wireless microphone manufacturers. ATSC signals, after all, generally tend to be less spectrum-’sloppy’ than their NTSC predecessors, thereby creating more useable ‘white space’ in-between them.

White space…aye, that’s the rub. The White Spaces Coalition is also eyeing potentially unoccupied spectrum for reuse in a location-adaptive manner, for WAN, LAN and PAN applications (at varying achievable bandwidths and reception ranges). In theory, at least, hardware (and its supportive software) developed by Coalition member companies and their partners would adaptively seek out and leverage spectrum that isn’t already occupied. By avoiding the broadcast signals of wireless microphone systems and other UHF and VHF equipment, it’d thereby prevent interference that, if present, would hinder the performance of all concerned parties.

Does the theory pan out in real world testing? The FCC says ‘no’, as do wireless microphone suppliers (the NAB isn’t thrilled with the idea, either). The White Spaces Coalition counters that the FCC evaluated a faulty prototype and, by also disregarding a submitted backup unit, thereby didn’t give the concept a fair shake(out). Who’s right? Who knows? The AES sponsored a special session on the topic late Saturday afternoon, which I unfortunately wasn’t able to attend because I was elsewhere in New York City at the time. If anyone out there attended the session and can provide a synopsis, I welcome your comments.

p.s…check out the linked graphic in this Digg post for a comprehensive U.S. spectrum allocation chart. Pretty mind-boggling, huh?

Followup: I forgot to mention that Audio-Technica is now marketing an UWB (ultra-wideband) wireless microphone set called SpectraPulse that, among other things, addresses "white space issues", in the vendor’s words.