http://groups.google.com/d/topic/comp.dcom.modems/iLgcQrmo_hI/discussion
`comp.dcom.modems ›
`What is a PEP modem?
`6 posts by 5 authors
`D.J.Williams
`10/31/96
`What exactly is a PEP modem? Is it a proprietary standard or are they
`made by other folks?
`Where can I get more info?
`Sorry for the 20 questions :)
`Dale
`Charles Hyde
`10/31/96
`In article <55ak3i$i...@fohnix.metronet.com>, da...@fohnix.metronet.com
`(D.J.Williams) wrote:
`What exactly is a PEP modem? Is it a proprietary standard or are they
`>made by other folks?
`Where can I get more info?
`Sorry for the 20 questions :)
`Dale
`
`>P
`
`EP was Telebit's protocol for high speed transmission long before any
`other manufacturer. I believe it stands for Packet Encapsulated
`Protocol. It was designed for UNIX and its high volume traffic. In a
`nut shell, it transmitted data on different carrier signals allowing the
`modems to step up or down by 100 as line conditions varied. They were
`highly regarded, up to about two or three years ago. That is when they
`were surpassed in the marketplace by other less expensive and faster
`modems. Telebit's Trailblazer modems failed to keep up with market
`demand for more speed. If you want some, I can probably scrounge up a
`pair.
`Charles Hyde
`John Navas
`10/31/96
`[POSTED TO comp.dcom.modems]
`da...@fohnix.metronet.com (D.J.Williams) wrote:
`>What exactly is a PEP modem? Is it a proprietary standard or are they
`>made by other folks?
`Where can I get more info?
`<http://www.telebit.com/>
`--
`Best regards,
`John mailto:JNa...@NavasGrp.Dublin.CA.US http://www.aimnet.com/~jnavas/
`
`>>
`
`>>
`
`>>
`
`>>
`
`>>
`
`Page 1 of 3
`
`

`
` 28800 Modem FAQ: http://www.aimnet.com/~jnavas/modem/faq.html
`Chris
`11/8/96
`On 31 Oct 1996 10:28:34 -0600, da...@fohnix.metronet.com (D.J.Williams)
`wrote:
`>What exactly is a PEP modem? Is it a proprietary standard or are they
`PEP stands for "Packetized Ensemble Protocol", a proprietary modem
`standard introduced by Telebit in 1986 in their "Trailblazer" modems.
`I've heard that some other manufacturers use PEP under license, but I
`don't know who they are. PEP is patented by Telebit. Telebit was
`recently purchased by Cisco. I haven't seen (or heard the whale song
`of) a PEP modem in years.
`Telebit modem were (are?) popular among unix system administrators
`because of their ability to "spoof" uucp, kermit, xmodem and other
`file transfer protocols.
`PEP is a most excellent protocol for transmission over noisy lines.
`PEP uses many (up to 511) carrier frequencies as opposed to the single
`carrier frequency used by most of the V.x modems today.
`When two PEP modems negotiate a connection, they exchange carrier
`usability information with each other. Noisy carriers can be locked
`out. Each separate carrier will be modulated using 2 to 7 bit QAM.
`Data is packetized over the carrier spectrum. Packet (aka baud or
`symbol) transmission rate is very slow. Maximum throughput is about
`23K bits per second. PEP includes it's own error detection and
`correction protocol.
`This multi carrier approach is efficient over noisy lines because of
`PEP's ability to dynamically allocate data over the most useable
`carriers. Since each carrier only represents a small amount of data,
`the loss of a few carriers is relativity insignificant. When the
`going gets rough, PEP stops using the carriers that are unreliable.
`When the going gets rough for a conventional modem, the modem falls
`back to a lower baud rate. There used to be only a few baud rates, so
`each fall-back was a significant step backwards - 9600, then 7200,
`then 4800, then 1200, etc. So a narrow-frequency impairment could
`result in a 25% to 50% loss in throughput.
`V.fast and V.34 introduced lots more baud rates, so this is not as
`significant as it used to be.
`Since PEPs baud rate is very slow (around 10), PEP is much better at
`handling impulse noise since each baud will last such a long time.
`So how come PEP never made it to the big time? It was considered in
`the 1993 CCITT V.fast study group, but the single carrier technology
`won out. I'm not really sure why, but many improvements were made to
`single-carrier technology that narrowed the differences.
`I wonder what modems would be like if the multi-carrier technology was
`adapted as the V.fast standard.
`Tobias Erichsen
`11/9/96
`Chris wrote:
`> I wonder what modems would be like if the multi-carrier technology was
`
`Page 2 of 3
`
`

`
`> adapted as the V.fast standard.
`The multi-carrier approach has been taken out of the box again for
`use in modern ADSL-technology! Downlink range up to 8Mbits/sec and
`uplinks up to 768kbit/sec.
`I think I read somewhere, that one ADSL-modulation scheme has even be
`approved as ANSI-standard.. (but I´m not really sure about that..)
`Tobias
`Tobias Erichsen
`11/9/96
`Chris wrote:
`> I wonder what modems would be like if the multi-carrier technology was
`> adapted as the V.fast standard.
`The multi-carrier approach has been taken out of the box again for
`use in modern ADSL-technology! Downlink range up to 8Mbits/sec and
`uplinks up to 768kbit/sec.
`I think I read somewhere, that one ADSL-modulation scheme has even be
`approved as ANSI-standard.. (but I´m not really sure about that..)
`Tobias
`
`Page 3 of 3