ZyXEL Communications Prestige 642 User Manual page 20

Prestige 642 ADSL Internet Access Router
For example, if there were no constraints of the Internet backbone or if fast servers were located in every
telephone central office, an ADSL modem could download the entire Encyclopedia Britannica to a user's
laptop in 16.6 minutes, compared to 6.4 days using a typical modem speed of 14,400 bps.
3. ADSL enables use of real-time, interactive multimedia and broadcast-quality video for such new
services as collaborative computing, video conferencing, distance learning and video-on-demand.
4. ADSL gives you the facility to have both voice and data services in use simultaneous and all over one
phone line. Both residential and businesses properties around the world are already running out of
spare lines on existing installed telephone cables so effectively doubling your capacity in this way is a
real benefit.
5. ADSL provides a private, secure channel of communications between you and the service provider.
6. Your data travels along you own line, unlike cable telephone and modem services where the line is
shared with others.
7. Because it is your own dedicated line, transmission speeds are not affected by other users going on-
line. With cable modems, transmission speeds do drop significantly as more users go on-line.
8. ADSL is "always on" and connected - just like your telephone. This means that there is no time wasted
dialing up the service several times a day and waiting to be connected - ADSL is on standby, waiting
ready for use whenever you are.
Full Rate (G.dmt) and G.Lite Standards
Full rate ADSL, with transmission speeds of up to 8 Mbps downstream and 832 Kbps upstream, was
originally intended for video applications but is now also targeted at bringing high-speed Internet access to
residential and small business users in the hope of generally accelerating widespread deployment of ADSL.
For this new market, access speeds at 10% of full ADSL capabilities are quite adequate. This reduction in
speed also means a reduction in complexity. Telephone companies saw a reduction in speed as a way to
simplify installation of ADSL service and thus eliminating the need to send a technician to install ADSL
service, enabling users to install ADSL modems just like they do with typical dial-up modems.
One major difference between ADSL modems and dial-up modems is the need for a telephone splitter
which keeps the telephone and ADSL signals separated, giving it the capability to provide simultaneous
Internet access and telephone service on the same line (you cannot do this with a dial-up modem). Splitters
also eliminate the destructive interference conditions caused by telephone sets. The telephone splitter has to
be installed on the line at the point of entry to the residence and would still require a technician to install. A
reduced rate ADSL modem would sacrifice the full speed in favor of operating without a splitter improving
widespread deployment of ADSL services. Thus, a new version of ADSL that would be consumer
installable was born. The Universal ADSL Working Group (UAWG) developed the G.Lite/DSL Lite
standard (also referred to as "splitterless" DSL or as Universal DSL) to create a universal, splitterless, and
therefore easy to install lower-speed version of ADSL. In October of 1998, G.992.2 was adopted as the
standard that began as the G.Lite standard.
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