[e2e] narrow vs. wide bandwidth (hz)

Michael B Greenwald mbgreen at dsl.cis.upenn.edu
Tue Oct 7 00:50:11 PDT 2003

   Mon, 06 Oct 2003 08:01:02 -0400
   "David P. Reed" <dpreed at reed.com>

   Michael - actually, metaphors are REALLY dangerous, and you are falling 
   into a trap here.

Definitely possible.  I'll try to explain the nature of my
[mis]understanding below.
   At 06:41 PM 10/3/2003, Michael B Greenwald wrote:
   >If you consider two systems that
   >have identical properties in all respects except that one has narrow
   >bandwidth than the other [I know this isn't always possible], I meant
   >that you'd prefer the system with narrower bandwidth.
   This is precisely the point I was saying is wrong.   You have fallen into 
   the trap of thinking that bandwidth is a resource that is consumed by a 
   communications system to produce its product.   Physically this is just not 
   true.  The metaphor persists in the minds of engineers because they have 
   been working for so long on FDM systems at the top level regulatory regime, 
   that they assume it must be true.
OK; I would not say "consumed" (as in a manner that "exhausts" the
resource, or uses it in some mutually exclusive way), but I *would*
say "utilized".  And I would obviously only consider narrowing
bandwidth(hz) relevant in systems where bandwidth (hz) is a limited
resource (due to sharing, or any other reason).  In that context I
assumed that if you have two implementations with all desirable
properties equal, and equal in all respects other than bandwidth (hz),
then the one that used narrower bandwidth (hz) would be better.  (And,
of course, if using a wider band yields a better system, I will prefer
the system that uses more bandwidth, but I thought I was clear that I
was speaking about the [sometimes hypothetical or mythical] case of
"all other things being equal".) If that's wrong, then I _have_ fallen
into the trap you are concerned about, and here's where I'd welcome
enlightenment (you can delete end2end-interest, but I may not be the
only one who has fallen into this trap).  And I'm aware of spread
spectrum, CDMA, etc., but perhaps I don't understand as well as I
thought, or I may be misunderstanding something fundamental about your

Awaiting enlightenment (or, at least, refinement of my terminology or
improvement of my metaphors) ...

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