[644] in Commercialization & Privatization of the Internet
Re: Perhaps dismissal of packet radio in the classroom is unwarranted
daemon@ATHENA.MIT.EDU (Dennis Ferguson)
Sun Apr 28 19:58:58 1991
From: Dennis Ferguson <dennis@utcs.utoronto.ca>
To: bill@tuatara.uofs.edu
Cc: com-priv@psi.com
Date: Sun, 28 Apr 1991 19:08:38 -0400
> I don't think Part 15 or the current crop of 900 Mhz Spread Spectrum boxes
> is the answer. The answer lies in proving that the technology exists to do
> the job today (it does) and then go after spectrum to do the job right. An
> unused UHF TV channel come to mind immediately.
I may be missing some context, but why is 900 MHz Spread Spectrum
inappropriate? I think that spread spectrum digital radio is quite
attractive technology for the application. It is robust and noise
immune, and this is an important property in a metropolitan area
if installations are uncoordinated and are possibly not of high
quality. You can build both short-distance multiple access and longer
distance point-to-point connections with the same hardware. It provides
a certain degree of security (insufficient, but a start). You can run
several systems in close proximity in the same frequency allocation
with minimal interference between them. It minimizes the cost of the
RF components, and puts the complexity in silicon where it is sure
to get cheaper.
If we can agree that spread spectrum is advantageous, then what is
wrong with 900 MHz? Spread spectrum requires a lot of bandwidth (the
more the better). Many of the 900 MHz boxes run with a 20 MHz
spread, if you want to use this technology in the UHF television
bands you are going to need 4 TV channels. 900 MHz requires no
licensing and coordination, hence no paper work. You can build
the RF hardware somewhat cheaper if you can design for a fixed
frequency range. The power limits at 900 MHz (1 watt, commercial
microwave transmitters are usually more like a tenth of that) are
generous enough that you can maybe afford to scrimp a little on
other things, like antennas and installation. And the big plus
is that everyone can use 900 MHz gear, whereas only schools could
use the hypothetical television band stuff. The bigger market for
900 MHz equipment has got to make it cheaper.
I agree that a lot of the first generation 900 MHz spread spectrum
hardware isn't quite right (either too expensive or done "wrong"),
but I don't see any problems which aren't fixable. Am I missing
something?
Dennis Ferguson
