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08/26/2004: "Vivato Goes Wide"

When I first read the headline to this story on Unstrung I thought that perhaps the voodoo of a 16 element system had returned, now that anyone who would point out the
essentially silly notion that paying for 2X the components for a 3dBi gain has left the building.

But no, its just more of the same old ... stuff.

The firm used six of these outdoor boxes and a "handful" of its microcells and picocells to cover 1,500 square miles in Walla Walla, Wash., according to Kevin Ryan, VP of marketing and business development.


Some basic calculations are in order. 1,500 square miles is what you get from an area that is 38.8 miles square. If Vivato's claims are to be believed, then each switch would need to cover 250 square miles (we'll ignore the 'hole-fillers' mentioned in the article).

250 square miles requires that each coverage area by each switch (wait, no, *basestation*) needs to illuminate a 15.8 mile x 15.8 mile area. The diagonal across this "square" is 22.4 miles. The LOS pathloss at 2.4GHz over 22.4 miles is approximately 131.5dB, and the strongest 11b client card I know of will only transmit 23dBm. This means that Vivato would have to, without using anything but antenna gain and receiver sensitivity, recover the signal at -108dBm when it arrives at the "basestation".

The claim is possible in-theory, but requires an environment about as pristine as that found inside an RF-shielded room, and allows for almost no fade margin. Perhaps Walla Walla, Wa. offers this, but the numbers look like the aftermath of a mastrubatory whiteboard session to me. Maybe they've put antennas on the "smaller units", and this is how they accomplish the somewhat fantastic ranges.

Or perhaps the coverage was not, in-fact, ubiquitous. The press release on Vivato's site only claims 2.5 miles of coverage from any product:


With Vivato's Wi-Fi base stations, which provide up to 2.5 miles of wireless coverage outdoors, and Vivato's Wi-Fi micro and pico cells for shorter ranges, customers can now access the Internet at broadband speeds.


and then, in the next paragraph:


"Constructing a wireless network covering 3,700 square miles is a challenging proposition, given the immense coverage area," said Tom Husted, chief executive officer of Columbia REA. "With Vivato's base station and micro and pico cell solution, we are able to provide up to 20 miles of wireless coverage outdoors - this enabled us to deliver a cost-effective wireless broadband service to our greater community - including residential home users, our rural farm customers, as well as our large, irrigated agriculture and commercial customers.


So the press release is in-conflict with itself. Which is it, 2.5 miles or 20 miles? 1,500 square miles, or 3,700 square miles? And why is it that these web-based "technology reporters" don't ask these questions?

Enquiring minds want to know.