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25th Anniversary of FCC Decision Enabling Wi-Fi and Bluetooth

25th Anniversary of FCC Decision Enabling Wi-Fi and Bluetooth
A series of posts describing how this all came about. (Click on picture above)

Wednesday, March 26, 2008



Google Flip-flops on White Space

Google filed a new letter at FCC on 3/21 changing its position on the Docket 04-186 TV white space proposal. After developing a listen-before-talk (LBT) detector, showing pictures of it, and leaving its antenna at the FCC Lab, they have decided to focus on the other two alternatives in the FCC's NPRM to avoid controversy. These alternatives were: geolocation (e.g. GPS) with database lookup and a local beacon to indicate what channels are available in a local area.

Google says,
"Under our own enhanced protection proposal, a TV white space device will not transmit on a channel until it first has received an "all clear" signal for that channel, either directly from a database of licensed transmitters in that area, or from a geo-located device with access to that database. That “permission to transmit” signal (at a maximum power level of 4W EIRP) would be sent on channels the geo-located device already knows are clear of licensed users. Any device without geo-location and database access would not transmit at all, unless and until it has successfully received advance permission from such a device."
If Google thinks this will make the controversy go away, I fear they are naive. While MSTV and NAB has focused on LBT as their main enemy, they have clearly dissed the other alternatives too: "The Notice’s Other Proposed Interference Prevention Techniques Would Be Ineffective" NAB and MSTV Reply Comments at p. 8

And even if the "immovable object" of the broadcasting community gives in to the "irresistible force" a little on the other two options, we then get into a question that has been lurking under the surface since the beginning of this rulemaking: where do you draw the line on the area where white space devices can operate?

MSTV has been cryptically talking about "protected contours" but has never defined that term or given a reference to any FCC rules that define it. In reality, FCC has defined the coverage area of TV stations in various ways for various purposes. Which definition would make MSTV happy? Remember MSTV has already said that there isn't any spectrum available for WSD use in major urban areas using their acceptable conditions. That says something about their thinking and is a hint of what will happen if Google and friends try to reach a negotiated understanding with MSTV.

NAB, however, has already blasted the Google letter/olive branch saying,
"We are pleased that Google now seems to realize that spectrum sensing alone won't protect viewers against interference from unlicensed devices. Unfortunately, simply adding geolocation and beacon sensing does not mean that mobile operation is suddenly feasible. Portable, mobile personal device operation in the same band as TV broadcasting continues to be a guaranteed recipe for producing interference and should not be allowed under any circumstances."
Google also hopes that they can make the wireless microphone problem go away also.
"Further, all TV white space devices would be blocked from transmitting by any wireless microphone beacon in that channel, using signals specifically designed to be easy to reliably detect, and coded to be identifiable to prevent abuse. These beacons should be quite inexpensive, and would be used in conjunction with existing wireless microphones, so there would be no need to replace legacy devices.

In addition, we are proposing a "safe harbor" for wireless microphones in channels 36-38. No TV white space device would be permitted to transmit in these channels. This will also protect medical telemetry devices and radio astronomy services, which are licensed to use channel 37."
Medical telemetry does indeed use "Channel 37" -- which is really a passive radio astronomy band. But this is an agreement FCC worked out, actually I was the one who proposed it, based on the fact that the medical telemetry equipment used is quite expensive, sold only to hospitals, and has a good history of compliance with licensed operation and rules. By contrast, the wireless microphone business is basically a "wild west" of spectrum squatters who are violating criminal laws in doing so and manufacturers who aid and abet this lawlessness. This is the group you want to share with medical telemetry and radio astronomy? Did anyone check if there is even enough capacity on channels 36-38 for broadway shows and live concerts with large numbers of microphones in major urban areas that may have TV stations on channels 35, 36, 38 and/or 39?

I suppose FCC would do anything to avoid making a decision here on spectrum policy and hopes that the Google position will be the basis of consensus. I suspect it will just introduce more controversy.

However, I hope that the ongoing FCC Lab tests will show that WSDs really do work with reasonable protection to the few (and ever decreasing) households that actually receive over-the-air television. As I wrote previously, the wireless mic problems should be addressed by more efficient wireless mic technology (not just ancient FM) and relocation to bands they can share with easier.

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Related post by Sascha Meinrath

1 comment:

Henry Cohen said...

"Did anyone check if there is even enough capacity on channels 36-38 for broadway shows and live concerts with large numbers of microphones in major urban areas that may have TV stations on channels 35, 36, 38 and/or 39?"
Yes; the entertainment production wireless community does on a regular basis. The answer is 18MHz, or even 24MHz, is not nearly enough for current FM based equipment. But you knew that.