Saturday, August 27, 2005

I Could Do Better

Business Week Online has an article from a Standard & Poor analyst which does a good job of perpetuating several popular WiMAX myths, confusing various technologies, and generally confusing the hell out of anyone who's trying to understand broadband wireless access.

Let's start with the simple fact-checking that you would think a professional analyst writing in a respected publication would have been able to get right: WiMAX compatibility testing is being performed by CETECOM, el Centro de Technologia de las Comunicaciones, S.A., not "Cenecom, the WiMax Forum Certification Laboratory, which opened in early August". CETECOM has been around since 1991; it's the WiMAX testing that started in August.

Then there's the ever-popular, "has a service range of up to 50 kilometers and provides data rates of up to 280 megabits per second per base station." This is even more outlandish than the usual hype, which limits its irrational exuberance to 70 Mb/s and 50 kilometers.

That "up to" is a great two words. My car can go up to 200 miles per hour and get up to 100 MPG. If I pushed it off a high enough cliff; otherwise, its performance is somewhat less.

I suppose with 80 MHz of spectrum and subscribers within half a mile of the base station (with line of sight to the base station antenna) that would enable the base station to run all the subscribers on 64QAM you could get 280 Mb/s out of a single base station. And I suppose with a really tall tower, really flat terrain, and remote units with their antennas sitting in a window facing the base station antenna, you could push a signal 50 km. But in anything approaching the real world, you're not going to get either 280 Mb/s or 50 km.

Realistically, with a 5/5.5 MHz channel (US WCS or BRS spectrum), you'll get around 13 Mb/s user payload, and in something approaching normal suburban/rural terrain, you'll be able to push a reasonable signal out 3 to 5 miles. Useful? Sure, especially for DSL-equivalent services where you can run oversubscription of 25:1 or higher. But let's not get carried away.

And by the way, that WCS or BRS spectrum is licensed and usable for WiMAX (though the WiMAX Forum profiles for 2.3/2.5 GHz haven't been completed yet). So saying that "there's no authorized radio frequency spectrum from the Federal Communications Commission for the issuance of WiMax licenses" is, well, wrong.

The article also says, "AirBand, Clearwire, and TowerStream... believe bandwidth is adequate within 50 megahertz to 500 megahertz bands for Wi-Fi and WiMax without seeking radio frequency licenses from the FCC." Actually, AirBand and Towerstream use frequencies in the 5 GHz unlicensed bands (that's 5000 MHz); Clearwire is the second-largest owner of BRS frequency licenses and has leased additional licenses (some from Sprint/Nextel).

And I'm not even going to get into the butchering of OFDM, OFDMA, and FLASH-OFDM.

I do not pretend to be a professional analyst; I write about things that interest me. I have some knowledge from my day job, and I have half a dozen tabs open in Firefox as I write this to track down the rest. If I can get this stuff right, you'd think a professional analyst who gets paid to follow this stuff could.

Maybe I'm in the wrong line of work.