Shure comments on whitespace

Whitespace use is where Google and Intel want to transmit data on unused TV channels. It used to also include transmitting in the 10kHz guard bands between channels, but it looks like even digital engineers can see that it is not really possible to have a 5 Watt transmitter in your living room at the same time your TV is trying to pick up microwatt signal a few Hertz away. I see white-space proposals as bullying by the big trendy companies with tons of cash and high-tone lobbyists [1, 2, 3, 4, 5]. They can charge by the minute and people are stupid enough to pay by the minute. So now the cell phone companies and anyone else that can enforce these rapacious rates wants the entire spectrum in the whole country. The TV stations are not too enthusiastic about having millions of intentional interferers put into their bandwidth. Neither is the Shure microphone company. Like Dennis Monticelli over at National Semitold me: “White spaces are really gray.” One of the gray areas is wireless microphones. These are professional wireless mics, not the cheapo ones. The pro mikes use the TV bands and they are a licensed application. If your theater company or rock concert wants to use them, you fill out paperwork and send it to the FCC. That way there is a paper trail on all the intentional interferers. If a TV station has some problems, the FCC can check to see who has wireless mics and what channels they are on.

When I went to AES last year I met up with Chris Lyons, Shure’s manager of technical and educational communications. He showed me a summary of Shure’s comments on the FCC whitespace order. We both agreed that the FCC order was not as bad as we feared nor as good as we hoped. Summarizing from the document:

• Wireless Microphones Remain Legal Throughout TV Bands. The White Spaces Order does not alter the ability of wireless microphones, in-ear monitors, intercom systems, and related equipment to operate in the TV bands.  Wireless microphone users may continue to operate, with or without a license, on any VHF or UHF TV channel (2-51, except 37) that is not assigned to a local TV station or Public Safety agency.

The summary goes on to mention that there will be two channels around channel 37 reserved for microphones, as well as several channels between 14 and 20. The summary notes the large-scale wireless mike users can use the geo-location database to protect their channels from the data-hogs that have muscled in. Also, there will be no spectrum-sensing requirement on the data-hogs. The FCC says that this is because it would add too much cost to the data hogs. Fact is it simply didn’t work. The problem arises because your TV antenna may be 30 meters up on your roof. It is pulling in a microwatt signal that your TV can demodulate. But down in your house or apartment, the TV signal could be attenuated by 60dB or more. So the data hog could do spectrum sensing and never see the TV station, and then go and blast out its 5 watts and wipe out the TV station up at your antenna, not to mention all your neighbors’ antennas. So that is why the FCC just requires the data hogs to check in with the geo-location database, which will have all the TV stations in your area.

I find it so amusing that the digital and software engineers at Google and Intel that proposed this whitespace insanity really do thing RF spectrum come in little boxes, like in a wall chart. In their honor, and in honor of all the grief and misery and interference they will create, here is my little chart of the RF spectrum as viewed by different types of engineers. Skirts? What are skirts, said the digital engineer.

And thank Silicon Labs and Marvell and a bunch of other companies for making TV tuners that will at least have some tiny chance of rejecting all these near-channel blockers.