Path: utzoo!attcan!uunet!zephyr.ens.tek.com!uw-beaver!rice!cs.utexas.edu!sdd.hp.com!decwrl!pacbell.com!pacbell!hoptoad!hsfmsh!daemon From: tnixon@hsfmsh.UUCP (Toby Nixon) Newsgroups: comp.dcom.modems Subject: Re: V.32bis ... what is it? Message-ID: <3395@hsfmsh.UUCP> Date: 2 Jul 90 17:19:57 GMT Sender: daemon@hsfmsh.UUCP Organization: Hayes Microcomputer Products, Inc. Norcross, Georgia Lines: 76 In article <8516@ubc-cs.UUCP>, rlin@cs.ubc.ca (Robert Lin) asks: - I just heard about V.32bis on this newsgroup, the wonderful 14.4Kbps - full duplex modem protocol. I have several questions: - - 1. How does it achieve this phenomenal speed? With some sort of - even more sophisticated constellation? How many points? CCITT V.32 uses 2400 baud modulation with a 32-point constellation (5 bits per baud; 4 data bits and 1 coding bit) to achieve 9600bps. V.32bis also uses 2400 baud modulation, with a 64-point constellation for 12000bps and a 128-point constellation for 14400bps. - 2. Does it have the adaptive nature of Telebit multi-carrier - protocol, that takes advantage of any extra bandwidth beyond - the promised standard? V.32bis doesn't use multicarrier modulation. It does, however, incorporate a rapid speed-change mechanism that allows the modem to change between the speeds supported (4800, 7200, 9600, 12000, and 14400) in under 100 milliseconds. I'm not sure what you mean by "takes advantage of any extra bandwidth beyond the promised standard"; either the phone equipment supports signals at a particular frequency, or it doesn't. Contributions to the CCITT have shown that attenuation and delay distortion of signals outside of the 300-3100Hz band is appreciable, making equalization very difficult. The CCITT is currently studying modulation techniques that may use more of this 2800Hz bandwidth to provide data rates in the 19200bps range (e.g., 2743 baud with a 256-point constellation would give you 19200bps; several existing modems for leased line use already do this). - 3. Is this a finalized protocol, formally adapted by CCITT, - and V.32bis is in an "agreed draft" form at this time, meaning that at the last CCITT Study Group XVII meeting in April 1990 there were no substantial objections to any of it. The Study Group will meet again in October, at which time it will consider adoption of V.32bis under the CCITT's accelerated procedures. If such adoption is unanimously supported by the Administrations attending the meeting, the standard will undergo a three-month written ballot of all CCITT member countries. If 70% of them approve, the standard will be formally adopted; the earliest we will know this result is around then end of February, 1991. - 4. has any one implemented this yet? If not, how many years can we - expect to wait before it is a reality? Forval America claims to have a V.32bis modem, but they can't possibly have incorporated the changes made at the April meeting (e.g., the rapid speed-change feature and modifications to the startup handshake). Therefore, and also because the standard is not yet adopted, the answer to your first question is No. There _are_ companies that have 14400bps duplex dial-up modems on the market today (e.g., British Telecom) who will certainly adapt them immediately to V.32bis compliance; at least two other companies have demonstrated 14400 duplex modulation. I suspect that we will see several V.32bis-compliant modems on the market around mid-1991, if the standard is adopted (most companies would not release a product then if the standard were still subject to change). -- Toby Nixon (Chairman, TIA TR-30.4; Special Rapporteur on Question 14 in CCITT Study Group XVII; Representative in the CCITT from Hayes Microcomputer Products, Inc.) ----------------------------------------------------------------------------- Toby Nixon, Principal Engineer Fax: +1-404-441-1213 Telex: 6502670805 Hayes Microcomputer Products Inc. Voice: +1-404-449-8791 CIS: 70271,404 Norcross, Georgia, USA BBS: 1-800-US-HAYES MCI: TNIXON Telemail: T.NIXON/HAYES AT&T: !tnixon UUCP: ...!uunet!hayes!tnixon Internet: hayes!tnixon@uunet.uu.net MHS: C=US / AD=ATTMAIL / PN=TOBY_L_NIXON / DD=TNIXON -----------------------------------------------------------------------------