[e2e] Bandwidth Estimation workshop

Michael B Greenwald mbgreen at dsl.cis.upenn.edu
Fri Oct 3 15:41:47 PDT 2003

   Fri, 03 Oct 2003 16:54:55 -0400
   "David P. Reed" <dpreed at reed.com>

   At 10:38 AM 10/3/2003, Susan Harris wrote:
   > > I believe you but I am surprised.  Is the distinction so hard to
   > > explain?  If the discussion about units doesn't enlighten them, what
   > > about the fact that often (all other things being equal) it's
   > > desirable to minimize one and maximize the other?  (This won't explain
   >Beginner's question - why is it desirable to minimize the Hz variety of
   Well ... this is actually not so simple, because the "good" direction on 
   bandwidth (in Hz) of a signal is not obvious at all.   ...
   [interesting explanation of why wider bandwidth has advantages, deleted]
   Wider bandwidth radio architectures can fix all of these and more.   That's 
   what spread spectrum, code-division multiple access, orthogonal frequency 
   division multiplexing, and ultrawideband technologies all do, in
   various ways. 

   In general, I would say that the wider the bandwidth of a signal, the 
   better the system can be, at least these days it seems to be true. 

All true, and I won't argue, but I meant something slightly different
(I should have been more clear).  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.  In that sense,
when you say that "the wider the bandwidth of a signal the better the
system can be", the same can be said of cost (in dollars).  The more
you are willing to spend, or the more expensive a system is, the
better a system can be.  Still, *all other things being equal*, we'd
like to minimize cost.  You can, metaphorically, consider bandwidth
(hz) to be cost and bandwidth (bps) to be value. [I deliberately chose
to use "bandwidth" for both terms because this particular subthread
was answering a question about how to instruct people that bandwidth
has two meanings.]  I didn't mean to imply that systems using narrower
bandwidth necessarily were better systems.


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