[10838] in Commercialization & Privatization of the Internet
Re: Two-way Internet service from Continental Cable?
daemon@ATHENA.MIT.EDU (Martin L. Schoffstall)
Fri Mar 11 22:06:21 1994
Date: Fri, 11 Mar 1994 18:02:39 +0000
From: "Martin L. Schoffstall" <marty@psilink.com>
To: "David Herron" <david@twg.com>, "Jeffrey K. MacKie-Mason" <jmm@merit.edu>
Cc: com-priv@psi.com, fellows@farnsworth.mit.edu
A TV channel is 6Mhz.
In Cambridge we are using two.
In the bad old days of cable you exclusively had one bus with a billion
aplifiers on it, but then along came the ability to run analog tv signals on
fiber and opportunities arise.
In cambridge there are at this moment 22 seperate segments to 22 "super
neighborhoods" these super neighborhoods can be subdivided (but not
infinitely of course) to additional segments. Each segments runs back to the
the headend.
For the individual service we use one complete channel, the current RF gear
lets us sub-divide (frequency domain multiplexed specifically) that 6Mhz into
4 "subchannels".
So for the individual service you have "peak" capability of
(SubChannelBandwidthZZ) Times 4 SubChannels Times 22 segments
for total Cambridge Wide MAN bandwidth.
This is using the current modular RF technology, the next generation
technology might have SubChannelBandwidthYY and 10 SubChanels.
Marty
> So it is certainly possible for Cable TV to be in the business of
> providing ethernet to houses. However if there's only one ethernet
> speed channel for the whole cable system, it can rather quickly get
> swamped. Think about connecting 90,000 nodes to a single ethernet
> segment. It will quickly fail.
>
> Perhaps since PSI is right here on the mailing list they can give a few
> technical bits about what PSICable is and how it's done. If I'm way
> off base here it'd be great if they'd say so ...
