Sunday, March 23, 2008

Google Seeks Open Spectrum Sharing in White Space TV Broadcast Bands

Google filed comments with the FCC presenting its plans for mobile broadband services using the TV "white space," along with an enhanced spectrum protection proposal aimed at addressing concerns about the merits of using the white space for unlicensed personal/portable devices. Google is predicting that advanced spectrum sensing technologies enabled by low-cost processors in communications devices will pave the wave for a much more efficient use of spectrum. Beginning with the TV whitespaces, this spectrum sensing technology could be extended to other bands, and perhaps ultimately to all bands.

Some key elements of the Google plan include:

  • (1) Google envisions a network that combines elements of both fixed/access unlicensed devices and personal/portable unlicensed devices. This "hybrid" approach will join together the tangible benefits of mobility, low cost, and ease of installation and use.

  • (2) Coupled with the "Android" open source platform for mobile consumer devices, TV white spaces can provide uniquely low-cost mobile broadband coverage for all Americans. As announced last fall, over thirty other companies are working with Google through the Open Handset Alliance to develop a fully open source software stack, including the operating system, middleware, and user applications. Android-powered handsets should begin appearing commercially later this year, and would be an excellent match for the TV white space.

  • (3) In the 700 MHz auction proceeding, Google advocated for openness at various network layers.3 In the context of TV white space, consumers will be able to enjoy robust access to the Internet, including the ability to download and utilize any lawful applications or content that is desired.

  • (4) Google also would be willing to provide, at no cost to third parties, the technical support necessary to make these plans happen; this could include intellectual property and reference designs for underlying technologies, open geo-databases maintained by Google, and other supporting infrastructure.

As for Google's enhanced protection proposal, the company said a TV white space device should 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. 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. Google is also 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.