Two interesting developments have emerged recently under the heading of “white spaces”.

First, if you recall, the FCC authorized the development and eventual marketing of “white space devices” that have now come to be known as TVBDs (TV Band Devices).

However, the technical requirements for these devices are quite stringent; specifically, that they must sense other signals and take a lower priority in any given location than existing TV broadcasts and wireless microphones.

Microsoft, working with researchers at Harvard University, has announced that it has set forth protocols for networks that will use this “unlicensed spectrum”.

Wireless microphones pose a significant challenge to such devices and networks because they’re very low power, and also, are only on when they’re being used.

To deal with this, Microsoft’s approach includes an algorithm that detects available frequencies and switches to a backup channel if interference is detected.

In tests, the device has detected interference from a wireless microphone and moved to another frequency within three seconds.

Three seconds? That can be an eternity if you are experiencing a wireless system dropout, but it depends on the situation as to whether or not it would be a problem.

For instance, what if you turn on all the wireless transmitters for a particular scene in a stage production?

In that scenario, the TVBD or local network would recognize these transmissions and avoid them with plenty of time before the wireless mics would actually be used.

On the other hand, imagine there’s a person in the lobby of a theater, uploading a file to a network from his TVBD. Then, he walks into the theater in the middle of an ongoing performance, where his TVBD starts to interfere with a wireless mic channel being used for the show.

In this case, there might actually be a wireless mic dropout that would last a full three seconds.

Of course, this assumes that the signals did not interfere with each other from the lobby, but would do so the instant they were in the house together.

It seems that there is still major room for improvement before these devices are ready for prime time.

Second, a company called RF Venue has emerged, promising to “Refine Wireless Microphone Performance in the White Space Era”.

It’s not clear if this company offers hardware, software, system management or some combination of these elements. What is clear is that this may be the first new company to enter the market, post-white spaces.

Existing wireless microphone manufacturers have all done their part to increase reliability of their systems in light of re-allocated spectrum and the threat that there may be new, unlicensed devices sharing spectrum.

But I think we will see more of these new entries as the issue heats up. That is, along with more new entries from existing players.

The next couple of years ought to be very interesting indeed.

Related links:
http://www.telecommagazine.com/newsglobe/article.asp?HH_ID=AR_5577
http://www.rfvenue.com

Signing off for now…
Mike Wireless

Mike Wireless is the nom de plume of a long-time RF geek devoted to better entertainment wireless system practices the world over.

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