Stability

Stability can be a bit subjective, and in general MaxDSL will be less stable than the fixed speed products with their conservative margins. G.dmt ADSL can only adapt to changes in noise or line condition by retraining, which the user sees as a temporary disconnection. ADSL2 and ADSL2+ have features like bit swapping and seamless rate adaption that can compensate for changes without requiring a retrain.

The response to question 6. "How stable is your connection, in terms of speed and disconnections. " was :-

Very stable. 53%
Occasional disconnections 30%
Frequent disconnections 13%
Totally unstable. 5%

so 83% are either very stable or have occasional disconnections.

48.5% of the "very stable" respondents knew they were on Fast path, and 16% knew they were interleaved. As 22% of the total knew they were interleaved this suggests that the interleaved lines were less well represented in the "very stable" category. 28% of the "occasional" and "frequent" disconnectors were interleaved, and the same in the "totally unstable" category, so the DLM had spotted them but the interleaving itself had not solved the problem.

For the speed ranges of 2M and over the "totally unstable" response covered about 4% of the lines. For lower speeds the % rose but the numbers reporting were small at 1 or 2 in each speed category.

5.8% of the fastest lines had "frequent disconnections", compared to 13% overall. 24% of the 4-6M, 18% of the 2-4M and 24% of the 1-2M sync speed lines also fell into the "frequent disconnection" category.

Looking at the influence of SNR margin, 70% of those with margins of 11 dB and higher said their connections were "very stable". In the 6-10 dB range this fell to 47.5% and in the 0-5 dB range to 41%.

There appears to be no substitute for having a good margin in terms of stability, which is why some are turning to tweakable routers to achieve higher SNR margins, lower speeds and greater reliability.