Navigating the White Spaces

By Mitch Gallagher

Guglielmo Marconi would be quite proud. Could he possibly have imagined that his work on the development of the "radiotelegraph" would impact the world as much as it does? Yes, he won a Nobel Prize in physics, so clearly he had a clue that he was on to something big, but could he have foreseen how far his wireless technology would reach?

Whether we know it or not, we live, at least partially, in a wireless world — and thank heavens for that fact! As musicians and engineers, wireless has certainly made our lives much easier — once you experience the thrill of having no cables to trip over and the freedom to move around (on stage), you'll never want to go back to being tethered by your microphone, guitar, bass, in-ear monitors, or mobile keyboard. Life is good...

...at least until the government decides to muck things up. In the case of wireless, this "mucking" has come about in the upcoming FCC deadline (slated for February 17, 2009, though there are rumorous rumblings that this may be pushed back) for the federally mandated switchover to digital television. As part of the changeover, the FCC has approved the use of "white spaces" — TV channels that are not used by local broadcast stations — for delivering wireless broadband internet service to consumer wireless devices (examples could include cell phones, wireless laptop computers, broadband internet equipment, and so on). Basically, this means that public emergency broadcast and telecom companies will take over those frequencies.

There's a switchover coming, so why should you care? If you're using a wireless system that operates in and around the 700MHz band (covering TV channels 52-69, from 698 to 806MHz), then you should definitely care, as the FCC is pushing to prohibit the use of wireless mics in this range in the very near future. Sounds dire, but will this really affect you? And if so, what can you do?

Read on...

The Situation

The good news is that your wireless microphones aren't going to just stop working on February 18th. There are also guidelines that the new white spaces devices must adhere to:

• White spaces devices can potentially be put on sale by manufacturers on February 18, 2009. The reality is, though, that it will take some time before any appreciable quantity will be used by the public. Before any new white spaces items can be released, they must pass FCC certification and public review and commentary. Shure, for example, does not expect the first of these white spaces devices to hit the streets until the end of 2009.
• White spaces devices cannot transmit on channels being used by TV stations, wireless microphones, and other devices. Before transmitting, a white spaces device must find its precise location and find a "safe" channel to use from a proposed database.
• If a white spaces device is within one kilometer of a wireless system that is known to be in use, it must find a different channel or cease transmitting.
• White spaces devices must consult the channel database whenever they are turned on, their location changes, or at least once per day.
• If you're going to be using a wireless system for a program or event, then you can register the event in the database — this can be a one-time (a concert), a recurring (a series of meetings or shows), or a permanent (a weekly church service) event.
• All white spaces devices must use spectrum sensing to detect TV stations, wireless microphones, and other devices — whether or not they are registered in the proposed database — in order to help prevent interference.
• Only fixed devices can operate in channels 2-20, and they may not use adjacent channels.
• There will be selected channels between 14 and 20, and between 21 and 51 that can be used by public safety agencies.

Navigating the Transition

As mentioned previously, your wireless system isn't just going to stop working on February 18th. Here's how to survive the changeover:

• If your wireless can operate on other bands, then you'll be fine. It is still legal for wireless systems to use VHF channels 2-13 and UHF channels 14-51.
• There will be channels available adjacent to local TV channels — remember that only fixed devices can operate on channels 2-20, and they may not use adjacent channels. This leaves channels available for wireless use.
• Use the FCC database to register the events where you will use your wireless systems, to protect them.
• You could continue to operate in the 700MHz band, but it's likely that your ability to do so in the future will be restricted.
• Obviously, it's more important than ever to follow best practices when using wireless equipment.

The Good News

Perhaps the best news for users of wireless systems that fall into the 700MHz band is that most wireless system manufacturers have created programs that will allow you to upgrade your system to a new one.

Here's where the leading wireless manufacturers stand:

	Sennheiser has multiple systems that operate outside the 700MHz band. In addition, Sennheiser has a program in place to help owners of 700MHz systems switch to a new system in the range below 698MHz. Rebates will be offered for purchases made between December 1, 2008 and December 1, 2009, for new Sennheiser wireless systems with the trade-in of an old 700MHz wireless system from Sennheiser or a competing brand. Single components will be rebated at half the system rebate value. The rebate values are tiered depending on the system and when it was purchased, and will range from $40 to $2,000.
	Shure has multiple systems that operate outside the 700MHz band. In addition, a trade-in program is in place for all owners of 700MHz frequency band wireless units, which applies to all qualifying Shure units purchased prior to February 1, 2007, and to any competitive 700MHz wireless systems. Trade in your old wireless system against a new one and receive up to a $1,000 mail-in rebate. For information on wireless systems purchased on or after that February 1, 2007, contact Shure at 800-257-4873.
	The ATW UHF systems operate outside the 700MHz band.
	Samson VHF systems operate outside the 700MHz band.
	The XDR wireless systems operate in the "frequency clear" 900MHz band.

Additional Information

Audio-Technica and Shure have released useful white papers that deal with frequency reallocation.

Download Audio-Technica White Spaces Fact Sheet - 1.8 MB
Download Audio-Technica White Spaces Update - 92 KB
Download Shure "The Truth About Wireless Microphone Technology" - 56 KB