Speak up, or get stepped on.
I don’t think I’ve ever written more than once or twice regarding the same subject, but the pending FCC/White Space issue recently discussed in the pages of FOH is progressing at an alarming rate, and there are new developments on a weekly basis. The latest is reflected in an article published by the New York Times on May 22, 2007. The author of the article, John Markoff, informs us that our friendly search engine folks at Google are calling on the FCC to allow companies to “allocate radio spectrum using the same kind of real-time auction that the search engine company now uses to sell advertisements.” In other words, Google wants the FCC to allow radio spectrum to be sold to the highest bidder. Trés capitalîst.
In February 2009, the FCC plans to sell off the spectrum known as “White Space,” i.e., the UHF TV channels that are “unused” except, of course, by those of us in the pro audio industry — but we don’t count because, technically speaking, we’re not on the radar. The sale of these frequencies is an auction-based event. Those who are most interested in purchasing them include cable, telephone and satellite providers, as well as groups interested in developing next-generation, nationwide digital wireless networks. In fact, this could increase competition and offer consumers alternatives to existing cable and telephone providers (never a bad thing).
Google maintains that the FCC allocation of frequencies is inefficient, so they propose that if the FCC were to allow companies to resell the spectrum (perhaps “re-auction” is a better word), actual use of the spectrum would increase. For example, a company could resell its spectrum to other service providers on an as-needed basis. “Hello I’d like to own 716.700 MHz for four days while my client performs at Madison Square Garden.” “Oh sure sir, that’ll be $10,000 per day. Will the artist be paying for that on his credit card?”
Google’s view is that this “wholesale auction” arrangement would allow more market-driven spectrum access, resulting in reduced retail prices — and they’re probably right. Except that it totally screws the pro audio industry because we can’t possibly compete on that playing field. We simply don’t have the cash. I suppose there might be something to be said for, perhaps, a major news network in New York wanting to rent a frequency for critical audio production applications, but that still gives them only one channel of audio.
I continue to feel that the only way Washington is going to really care about the pro audio industry’s stake in the White Space issue will be when some pompous politician is using a wireless mic to deliver a speech to his minions, and he’s interrupted with the sound of interference in his audio path. Speak up, or get stepped on.
Speaking of Wireless Audio…
One type of technology that may help alleviate the White Space problem is called “spread spectrum wireless technology.” Spread spectrum has been used by the military since at least the mid-1990s, but hasn’t really made its way into the pro audio market. Spread spectrum wireless devices operate in frequencies above UHF — specifically in the 900 MHz and 2.4 GHz bands. The unique concept behind spread spectrum is that a single channel of audio does not operate on one specific frequency. Instead, manufacturers have developed algorithms for “frequency hopping,” whereby both the transmitter and receiver change operating frequencies during broadcast. It’s sort of like synchronized swimming and is not as radical as it seems. For example, you manually initiate frequency hopping every time you press the channel button on your cordless phone at home. That simple press of a button tells the handset and base receiver “change to this channel in a certain number of milliseconds.” Your signal is briefly muted and then reappears on another channel, hopefully with less interference than the original. It’s that briefly muted part that scares audio pros.
Of course, automating the frequency-hopping process requires quite a bit of finesse. The system must first scan the local radio spectrum to determine the available frequencies and then process a routine that times the channel-hop for both transmitter and receiver. Sounds easy, but it isn’t, since an error in timing will cause the transmitter and receiver to be on different channels — resulting in a loss of signal.
Our friends over at Clear-Com are using spread spectrum technology in their Tempest 2400 and Tempest 900 series of wireless intercoms. Tempest systems use Frequency Hopping Spread Spectrum (FHSS) along with 2xTX Transmission Voice Data Redundancy to send each packet of audio data twice on different frequencies via different antenna in an effort to ensure uninterrupted, high-quality audio. The system can support up to five wireless BeltStations (remote packs) per BaseStation, and when operating in the 2.4 GHz band, up to 10 BaseStations and 50 BeltStations can be used simultaneously — accommodating far more users than if the system were operating in the FM band.
One Small Step for Intercoms
While Clear-Com’s FHSS is not being applied to wireless microphone and instrument systems just yet, it serves several important functions for the pro audio community. First, it enables a higher number of channels of Clear-Com to be used in production situations without the worry that users will interfere with each other (lighting companies rejoice). Second, since FHSS exists in 900 MHz and 2.4 GHz bands, it keeps the lower FM range clear for existing vocal and instrument RF systems. Third, spread spectrum technology decreases the average energy of RF signal at any one frequency, thus reducing the possibility of interference from any one particular transmitter. Finally, it gives the pro audio community hope that there’s alternative technology to our existing VHF and UHF wireless on the horizon. I’m optimistic that it’s only a matter of time before spread spectrum matures to a point where it can be applied to vocal microphones and wireless instrument systems.
As the tour manager and Front of House engineer for Blue Öyster Cult, Steve La Cerra will be frequently hopping around the country this summer. He can be reached via e-mail at Woody@fohonline.com
