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From: tnixon@hayes.uucp
Newsgroups: comp.dcom.modems
Subject: Re: Telebits "PEP" protocol
Message-ID: <3693.2768a08e@hayes.uucp>
Date: 14 Dec 90 09:51:10 GMT
References: <1990Dec8.025415.2920@amd.com> <8sHZT4w163w@mudos.ann-arbor.mi.us> <3592@jaytee.East.Sun.COM>
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Organization: Hayes Microcomputer Products, Norcross, GA
Lines: 57

In article <3592@jaytee.East.Sun.COM>, gsteckel@vergil.East.Sun.COM
(Geoff Steckel - Sun BOS Hardware) writes: 

> Open letter to Telebit:  if you think PEP is worth anything, licence
> it (with or without fee).  Otherwise it will be bypassed by a (possibly
> inferior) but widely available standard.  V.32 is coming up fast.

It's clear that most people are not aware of activities in CCITT 
Study Group XVII (the international standards committee on modems) 
and TIA TR-30 (the US national standards committee on modems) 
related to PEP.  I'm an active participant in these and other 
standards organizations, and maybe I can shed some light on it.

Telebit has been trying for at least five years to get the standards 
community to buy into multicarrier modulation, and have failed.  
There are many technical reasons:  the long propagation delay
through a multicarrier system, the half-duplex nature (echo
cancellation capability is claimed, but has not been demonstrated
even on paper), the complexities of supporting synchronous 
communications and async comm without buffering and flow control,
etc.  Telebit's persistence in trying to get multicarrier considered
as the modulation standard for "V.asym" (asymmetrical modem
standard) stalled, and eventually killed, that project.  It turned
into "V.17", an application-specific modulation technique for
high-speed Group 3 fax, rather than the general-purpose low-cost
high-speed modem it was intended to be. 

Now, the CCITT is working on the "V.fast" standard (full-duplex
modulation above 14,400bps), and once again Telebit has proposed
multicarrier. The schedule calls for test results of a full-duplex
system to be available at the SG XVII meeting in April; the group
can't wait any longer than that, or they won't be able to complete
work by the end of 1992 (the scheduled completion date for V.fast). 
The Codex's, General Datacomm's, and Racal-Milgo's of the world 
won't let this project be stalled the way V.asym was stalled.  I 
sincerely hope that Telebit can demonstrate multicarrier echo 
cancellation, because I'd like to see multicarrier get fair 
consideration; but I'm not optimistic.  

The problem is not that Telebit has been unwilling to license their 
patents related to multicarrier modulation, or has been keeping it
secret.  In fact, they've been quite open about how it works (in 
multitudinous contributions to TIA and CCITT) and actively trying to
sell licenses, but have been met with a resounding yawn.  A couple
of companies licensed the technology, including Ven-Tel and
Anderson-Jacobsen, and Intelligent Modem Corporation (Forval)
apparently has come up with a different multicarrier scheme (and is
supporting multicarrier in SG XVII for V.fast).  But most modem 
companies want their products to serve a broad spectrum of 
applications, and this means providing true full-duplex modems with 
low propagation delay.

-- 
Toby Nixon, Principal Engineer    | Voice   +1-404-449-8791  Telex 151243420
Hayes Microcomputer Products Inc. | Fax     +1-404-447-0178  CIS   70271,404
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