Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!uunet!aurs01!whitcomb
From: whitcomb@aurs01.uucp (Jonathan Whitcomb)
Newsgroups: comp.dcom.modems
Subject: HST implementation of V.32/V.32bis
Keywords: echo cancellation, constellations, Trellis
Message-ID: <59490@aurs01.UUCP>
Date: 31 Jan 91 16:29:05 GMT
Sender: news@aurs01.UUCP
Distribution: na
Organization: Alcatel Network Systems, Raleigh NC
Lines: 29

I am trying to understand the differences between HST and the
V.32/V.32bis standards.  I understand that HST does not have
echo cancellation, and instead uses a low speed channel for
full duplex operation.  I also gather that HST can change the
high speed channel from the caller to receiver by retraining.

I am still fuzzy on the following:

1.  Does HST high speed channel use V.32 modulation specs for
constellation mapping and Trellis decode algorithms?

2.  What are the specifics of the low speed channel?  I assume that
it is an FSK channel, and if so, what are the mark and space frequencies?
Is it correct that the 9600 uses a 300 baud channel and the 12000 uses
a 450 baud channel?  Do both have the same mark and space frequencies?

3.  Are there any other modem manufacturers that are implementing
pseudo-CCITT implementations of V.32/V.32bis?  It seems like folks
are jumping through all kinds of hoops to avoid echo cancellation and
Trellis code implementations.

4.  Is the HST modem popular enough to worry about, or will it vanish
once V.32/V.32bis catch on?

Thanks.
**********************************************************************
Jonathan Whitcomb                    UUCP: <...!mcnc!aurgate!whitcomb>
(919) 850-6231                       I'm not a software engineer,
Raleigh, NC                          but I play one on TV.