While many of us were distracted by the glittering technoproducts at the CEDIA Show in September, the FCC was voting to finalize rules for use of the White Spaces spectrum, those controversial spectra in between the recently established digital television transmission channels.
The fact that many of those glittering CEDIA products were themselves wireless was ironic icing on the cake. The future will be largely wireless, and there will inevitably be a growing number of entities competing to use the available spectrum.
The Rules
The ruling, handed down on Sept. 23, finalizes some legal and technical issues that have remained unresolved since the previous FCC ruling was issued in November 2008. The new order establishes a set of operating protocols that will enable both small and large users of wireless microphones to operate without interference from new TV-band devices. You may have seen the updated procedures elsewhere since then, but it's useful to summarize them here (from Shure's synopsis of the new ruling):
- The majority of wireless microphone users (who typically use fewer than 20 wireless systems) will be able to operate in "reserved" TV channels that are off-limits to TV-band devices, thus eliminating the potential for interference.
- A minimum of two TV channels in each market will be reserved for wireless microphone use. These channels will be the first TV channel above 37 that is not occupied by a TV station and the first TV channel below 37 that is not occupied by a TV station. If channels above and below 37 are not available, the two channels closest to 37 will be reserved. Because occupied TV channels vary by market, the Reserved Channels will vary by market also.
- Additional TV channels between 14 and 20 will also be off-limits to TV-band devices due to the technical restrictions that govern their operation. For example, channels in the 14-20 range that are adjacent to those occupied by TV stations are also effectively reserved for wireless microphone use.
- Large-scale wireless mic users will be able to achieve expanded protection for specific events through the (still to be compiled) geo-location database prescribed by the FCC in 2008.
- Portable devices will be prevented from transmitting on TV channels used by wireless microphones in the database when they are within a 400-meter "exclusion zone" around that location; fixed TV-band devices are subject to a larger 1-kilometer exclusion zone.
- Venues must request database registration at least 30 days in advance, and must certify that at least six to eight wireless microphones are operating in each of the reserved TV channels on which wireless microphones can practicably be used at that location.
The ruling ends two years of speculation, apprehension and blatant lobbying on both sides. But like most things bureaucratic, its implementation will be slow; a number of issues still must be resolved, including selection of database administrator(s) and registration and device access procedures must be finalized. Manufacturers must design new devices and submit them to the FCC for testing and approval. But it does open the door for what will likely ultimately be a flood of devices for the spectrum.
Moving On
The White Spaces have been the apple of the eyes of big-name consumer tech products makers like Microsoft, Motorola and Google, whose software and hardware products expect to use the White Spaces as an enormous wireless playground. These devices range from cell phones to iPads and other e-readers to stuff that hasn't been invented yet. (But since when has vaporware ever stopped Microsoft?) They're also establishing real-world pilot operations: Microsoft has set up a campus-wide high-speed wireless network using White-Space frequencies at its Redmond, WA HQ; Google has done the same for a medical complex in Ohio, under an experimental one-year license granted by the FCC. It's worth noting that in the Microsoft instance, the company is using only two base station transmitters, thanks to the fact that signals that use the White Spaces spectrum travel at least three times further than signals transmitted over other unlicensed spectrum, such as WiFi, and at lower frequencies, which allows them to penetrate vertical obstacles. This part of the spectrum is efficient and cost-effective, which is why broadcasters wanted to hold onto it. Conventional commercial wireless users, particularly broadcasters, continue to battle these plans, however. Their nomenclature speaks volumes: the White Spaces that the consumer electronics industry calls the greatest opportunity since Marconi are referred to by the NAB as "interference zones."
The bottom line is that while the FCC's conclusions aren't as comprehensive as many wireless users had hoped – for instance, spectrum sensing technology that would have made consumer devices proactively agile in avoiding professional wireless systems was eliminated from the mandate – it does provide a set of ground rules that service the aims of both types of White Spaces users. As Mark Brunner, who has been Shure's technology point person during the lengthy White Spaces debate, put it to me, "Pro audio has always had to work within the Swiss cheese of the spectrum." Now, at least, everyone will know where the holes are.
