subject: V.92 - new modem standard posted: Tue, 19 Feb 2002 05:14:56 -0000
[sorry, URL lost.. article is mostly OK, although "downloading web pages is MUCH faster" seems to be an
overstatement, given the compression ratio only goes from 4:1to 6:1 - Stuart]
[...]
In order to better illustrate some of the key changes in the new standard we've listed them below:
-Faster Upstream (Upload) Transmissions
The v.90 standard limited you to 33Kbps due to only using an analogue method instead of the 90's
analogue/digital combo for downstream. The redesign of the upstream modulation to accommodate the
pulse code modulation (PCM) codec, which converts analogue signals to digital, represents the biggest
change and required the greatest technological effort. This now means that a theoretical maximum of
48Kbps is possible, although 44Kbps is the recognised standard.
-Quick Dial-Up Connect Initialise (Handshake)
Up until now all modems have a tendency to be slow when communicating the initial connection (dialling
up). This is usually the part where modems make those strange fuzzy sounds, as well as the speed at
which they physically dial the number. V.92 makes this almost as fast as ISDN by assuming that each
connection is from the same location. In reality, the same phone lines connect repeatedly. Quick connect
shortens a modem's time to learn a phone line's characteristics by reusing some information previously
learned.
-Modem-On-Hold
The modem-on-hold feature lets modems gracefully break a connection and stand by while another call is
taken. Clients can accept incoming calls without crashing the connection, so users can access the Internet
or corporate network without missing telephone calls, or pause browsing to make a call (with less need for
second lines at home). Used in conjunction with quick connect, the modem-on-hold feature can make
resumption of the data call quicker and more seamless.
-v.44 Compression Protocol
Not an official part of v.92, but nevertheless included with 99.9% of v.92 modems as standard. The v.44
compression protocol can achieve a 6:1 compression ratio, as opposed to the 4:1 compression ratio of its
predecessor, v.42bis. Depending on your data traffic, this means an increase in data throughput and
modem efficiency. Precompressed data, such as JPEG images, won't benefit much, but text data, such as
HTML, will benefit from effective compression.
The four features above are the primary additions, although such things as the v.59 diagnostic protocol
have also been included, yet aren't of any great interest. In summary a fully supported v.92 modem and
connection (ISP end) will allow you to connect almost instantly, have very increased upload speeds,
download web pages MUCH faster (compression) and pause your connection in order to talk on the phone.
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* Origin: [adminz] tech, security, support (192.168.0.2)
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