White Spaces Geolocation Database

For now, all White Spaces devices will use a geolocation database to avoid interfering with licensed spectrum users. The latest FCC Memorandum and Order on TV White Spaces says that it is still OK to have a device that uses spectrum sensing only (one that doesn’t consult a geolocation database for licensed spectrum users), but to get certified for sensing only, a device will have to satisfy the FCC’s Office of Engineering and Technology, then be approved by the Commissioners on a case-by-case basis.

So all the devices for the foreseeable future are going to use a geolocation database. But they will have spectrum-sensing capabilities too, in order to select the cleanest channel from the list of available channels provided by the database.

Fixed devices (access points) will normally have a wired Internet connection. Once a fixed device has figured out where it is, it can query the database over the Internet for a list of available channels. Then it can advertise itself on those channels.

Mobile devices (phones, laptops etc.) will normally have non-whitespace connections to the Internet too, for example Wi-Fi or cellular data. These devices can know where they are by GPS or some other location technology, and query the geolocation database over their non-whitespace connection. If a mobile device doesn’t have non-whitespace Internet connectivity, it can sit and wait until it senses a beacon from a fixed whitespace device, then query the geolocation database over the whitespace connection. There is a slight chance at this point that the mobile device is using a licensed frequency inside the licensee’s protected contour. This chance is mitigated because the contour includes a buffer zone, so a mobile device inside a protected contour should be beyond the range of any whitespace devices outside that contour. The interference will also be very brief, since when it gets the response from the database it will instantly switch to another channel.

Nine companies have proposed themselves as geolocation database providers. Here they are, linked to the proposals they filed with the FCC:

Here’s an example of what a protected contour looks like. Here’s an example database. Note that this database is not accurate yet.

Actually, a geolocation database is overkill for most cases. The bulk of the information is just a reformatting of data the FCC already publishes online; it’s only 37 megabytes compressed. It could be kept in the phone since it doesn’t change much; it is updated weekly.

The proposed database will be useful for those rare events where the number of wireless microphones needed is so large that it won’t fit into the spectrum reserved for microphones, though in this case spectrum sensing would probably suffice. In other words, the geolocation database is a heavyweight solution to a lightweight problem.

Genuine Disruption from PicoChip

Clayton Christensen turned business thinking upside-down in 1997 with his book “The Innovator’s Dilemma” where he popularized his term “disruptive technology” in an analysis of the disk drive business. Since then abuse and over-use have rendered the term a meaningless cliche, but the idea behind it is still valid: well-run large companies that pay attention to their customers and make all the right decisions can be defeated in the market by upstarts that emerge from low-end niches with lower-cost, lower performance products.

PicoChip is following Christensen’s script faithfully. First it made a low-cost consumer-oriented chip that performed many of the functions of a cellular base station. Now it has added in some additional base station functions to address the infrastructure market.

Traditional infrastructure makers now face the prospect of residential device economics moving up to the macrocell.
From Rethink Wireless

FCC to address White Spaces at September 23rd Meeting

The agenda for the September 23rd FCC Commission Meeting lists:

TV White Spaces Second MO&O: A Second Memorandum Opinion and Order that will create opportunities for investment and innovation in advanced Wi-Fi technologies and a variety of broadband services by finalizing provisions for unlicensed wireless devices to operate in unused parts of TV spectrum.

Early discussion of White Spaces proposed that client devices would be responsible for finding vacant spectrum to use. This “spectrum sensing” or “detect and avoid” technology was sufficiently controversial that a consensus grew to supplement it with a geolocation database, where the client devices determine their location using GPS or other technologies, then consult a coverage database showing which frequencies are available at that location.

Among the Internet companies this consensus now appears to have evolved to eliminate the spectrum-sensing requirement for geolocation-enabled devices.

The Register says that this is because spectrum sensing doesn’t work.

The Associated Press predicts that the Order will go along with the Internet companies, and ditch the spectrum sensing requirement.

Some of the technology companies behind the white spaces are fighting a rearguard action, saying there are good reasons to retain spectrum sensing as an alternative to geolocation. The broadcasting industry (represented by the NAB and MSTV) want to require both. It will be interesting to see if the FCC leaves any spectrum sensing provisions in the Order.