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From: lstowell@pyrnova.pyramid.com (Lon Stowell)
Newsgroups: comp.dcom.modems
Subject: Re: Inexpensive 9600 baud modems
Keywords: 9600, V.32, V.42, bis
Message-ID: <136548@pyramid.pyramid.com>
Date: 4 Dec 90 21:18:18 GMT
Sender: daemon@pyramid.pyramid.com
Reply-To: lstowell@pyrnova.pyramid.com (Lon Stowell)
Organization: Pyramid Technology Corp., Mountain View, CA
Lines: 21

In article <5435@navy19.UUCP> benyukhi@motcid.UUCP (Ed Benyukhis) writes:
>57 Kbps on the voice grade line that is band limited to 3.4 Khz is contrary
>to both Shannon and Nyquist rules.
>
>
>Ed Benyukhis


Maybe so, but the POTS line, with its 3.4 Khz limit can easily
handle 160 Kbit/second or so rates.  ISDN easily places 144 Kbit
USER rate on this 2-wire line, using 2B1Q signalling...

Don't confuse the Nyquist limit on "baud" or carrier signalling
interval over 3.4 KHz with the ability to encode and decode user
information as multiple bits/baud over the bandwidth limited
channel...   38.4 USER rate works quite nicely over V.32 modems
by using Trellis (5:4 redundancy) and QAM (4:1) signalling at a
baud rate of only 1200 on the analog channel...although the
"raw" bit rate is only 9600...and V.32bis will push this to 14.4
raw rate,,,should be able to use data compression to get 57.6
out of a V.32bis modem easily...