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From: rpw3@redwood.UUCP (Rob Warnock)
Newsgroups: net.physics
Subject: Re: purplexing multiplexing question....
Message-ID: <175@redwood.UUCP>
Date: Wed, 27-Feb-85 18:18:59 EST
Article-I.D.: redwood.175
Posted: Wed Feb 27 18:18:59 1985
Date-Received: Sun, 3-Mar-85 05:26:42 EST
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Organization: [Consultant], Foster City, CA
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> can anyone explain the difference between "time-division" and
> "frequency-division" multiplexing in laymans' terms?
> mail: ihnp4!drutx!grm
[then follows a nice reply by Jeff Sonntag ]

Just to complete the orthogonalization, let us not forget "space-division"
multiplexing, which allows multiple communications to proceed at the
same time on the same frequencies, but at different places. Examples
are: multiple wires in a bus, multiple T-1 trunks between COs, tight-beam
point-to-point microwave or laser links, and (very important!) multiple
lanes in a road.  ;-}  (Polarization-division multiplexing, widely used
in satellite transmission, is generally viewed as a form of space-division,
but can be thought of as frequency-division by choosing a suitable definition
of "vector frequency".)

Note that highways exhibit both time- and space-division muxtiplexing,
but as the discrete nature of the objects carried thence implies an
extremely wide spectrum in the DeBroglie-wave representation, frequency-
division cannot be usefully employed while maintaining the identity of
the wave packets. Of course, from time to time some unfortunate experimenters
do (unsuccessfully) try...  ;-} ;-}


Rob Warnock
Systems Architecture Consultant

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