- G.lite is more than splitterless. There are power management & fast retrain procedures, as well as simplifications designed for more PC-oriented solutions.
Message 11519799
- Microfilters were envisioned awhile ago as part of g.lite to treat phones which required too much power cutback.
- G.lite's rate limit is artificial. The standard only sets the minimum maximum bit rate that can be supported (1.5 Mbps) while the actual max rate that can be supported (on shorter loops) is often over 3 Mbps and may be as high as 4.5 Mbps. At higher rates, performance is a bit less than you would get using full-rate ADSL. Its on short loops that the extra tones in full-rate kick in.
- (most importantly) they can't install an unlimited amount of microfilters since the line capacitance is additive. (eg., if a CPE has 5 phones ..fax, answering machine, etc... chances are with g.lite, 2 or more would need microfilters. And if you use more microfilters, then both modem & voice quality degrade from over-capacitance.
Also, some Loring detail clarifications (from info likely gotten from 2Wire's marketing dept)
"..John Cioffi at Stanford University revealed that the splitterless systems could see severely eroded data speeds when nearby phones were taken off the hook, and users heard significant noise when trying to place a voice call..."
Cioffi's tests were on prototype (ie., not standards-compliant) G.lite transceivers - subsequent work dramatically improved power back-off & fast retrain algorithms. Even so, microfilters are still often needed.
"..As a tactical response, Texas Instruments Inc. and Globespan Inc. designed microfilters * tiny devices that plug into every phone or fax in the home to demarcate voice and data traffic and keep the signals clean * to sell along with their chip sets".."
Globespan's (and possibly TI's) microfilters predated G.lite chips & were used with CAP ADSL - originally branded as "easy-DSL".
"..Peden, former chairman of the Universal ADSL Working Group, the ad hoc industry group that rallied behind G.Lite, said that any move to make DSL services cost-effective is a boon to the industry..."
Mark Peden was never chairman of UAWG. Not known as a technician, he was marketing committee chair.
"...G.Lite line cards use much less power than full-rate versions, and the densities are much higher," Aalaei said. "The whole goal of G.Lite is to reduce complexity and power dissipation..."
The power issue that centillium raises is implementation specific - the power savings are small when compared to that saved by using different implementations.
Multi-mode modems are thought by many to be the way to go since g.lite offers significant advantages when running at <1.5 Mbps which a large number of users are constrained to running at due to line length. |
