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From: berger@clio.UUCP
Newsgroups: comp.dcom.lans
Subject: Re: Ethernet : Broadband vs Baseband
Message-ID: <18500001@clio>
Date: Tue, 17-Feb-87 11:25:00 EST
Article-I.D.: clio.18500001
Posted: Tue Feb 17 11:25:00 1987
Date-Received: Thu, 19-Feb-87 20:40:19 EST
References: <2334@sunybcs.UUCP>
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Nf-ID: #R:sunybcs.UUCP:2334:clio:18500001:000:1532
Nf-From: clio.Uiuc.ARPA!berger    Feb 17 10:25:00 1987


Briefly, the length of the cable is limited by capacitance and
the number of terminations.  Splices will change the SWR and
also affect performance and maximum length.

Baseband networks use the entire cable bandwidth for a single
channel.  A broadband cable of the same bandwidth might be
divided into dozens or hundreds of channels.  Although you
could theoretically squeeze the same performance out of either
system, high performance baseband systems are rare (and usually
wasteful, since every device would have to be very fast to take
advantage of the entire bandwidth).  If broadband networks are longer
than baseband networks, it's only because broadband repeaters are
easier and cheaper to build.

Data transfer rates, as noted above, are based on a number of factors.
A typical intra-city television cable may carry 150 channels, each of
which is several megahertz wide.  150 devices can thus use the cable
concurrently.  Only one device can use a broadband cable at a time,
thus, each of 150 devices would have to wait their turn (and possibly
arbitrate to decide who grabs the line, wasting more bandwidth).  Slow
devices tie up the bus for longer periods.

Your last question is sort of a non-sequiter - I'm not convinced that
broadband systems have inherently more bandwidth than baseband systems -
but you can see why it's easier to use all the bandwidth in a broadband
system.

		Mike Berger
		Center for Advanced Study
		University of Illinois
		{ihnp4|convex|pur-ee}!uiucuxc!clio!berger

is a non-sequiter.  Broadb