Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!ucbvax!decwrl!decvax!ima!cfisun!lakart!dg
From: dg@lakart.UUCP (David Goodenough)
Newsgroups: comp.dcom.modems
Subject: Full duplex / Half Duplex with Telebits
Message-ID: <630@lakart.UUCP>
Date: 26 Jul 89 01:25:58 GMT
Organization: Lakart Corporation, Newton, MA
Lines: 17

As is well recorded, when a pair of TB modems are PEP'ing at each other, only
one end gets to talk at a time. Now, the modulation used by the TB uses many
different tones, and presumably the demodulation does some real clever trickery
with DSP to achieve the equivalent of a bandpass filter with a *REAL* high
Q factor for each tone. Now, why is it not possible for one end to use some
of the tones, and the other end to use some others, and achieve full duplex
communicaions, at the cost of reduced transfer rates (i.e. 18000 in one
direction, or 10000 in one direction, and 8000 in the other).

Since the system is able to dynamically select a subset of the tones anyway,
it would seem that most of the ability is in place. However, it can't be
done, and I'll bet there is a good reason. What is that reason?
-- 
	dg@lakart.UUCP - David Goodenough		+---+
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