btw there was also an image with this [see attatchment below].
As I mentioned in my earlier post there was no actual definitions of the figures, but from the image it allows 6 different configurations.
Below are the 6 different profiles. The figures in italics being my assumption of what they are most likely to be.
1) Interleaving OFF - Normal profile (
likely 6dB Target SNR)
2) Interleaving OFF - Stable profile (
probably 9dB Target SNR?)
3) Interleaving OFF - SuperStable profile (
probably 12dB SNR?)
4) Interleaving ON - Normal profile (
likely 6dB Target SNR)
5) Interleaving ON - Stable profile (
probably 9dB Target SNR + possible increased depth of interleaving?)
6) Interleaving ON - Super Stable (
probably 12dB Target SNR + possible further increased depth of interleaving?)
>> It's absolutely not a way of decreasing the target SNR...
Since the profiles are also available for non interleaved lines... then surely that means that it must involve changing the Target SNR.
If a line is non-interleaved.. changing interleaving depth would be a complete waste of time!
Based on the fact that a 3dB Target profile change will make a difference of anything from 400kbps to 1200kbps of sync speed depending on how many bits are loaded per bin.. this ties in very nicely with what James from adsl24 has said about each step lowering the sync speed by about 800k.
(800kbps is a fair figure to quote as average for 3dB of target SNR).
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btw forgot to mention - increasing interleaving depth adds to delay (increased latency). Therefore increasing interleaving depth doesnt effect your sync speed.. but it does increase your ping times. Latency != speed.
Theres also one other configurable attribute that also hasnt been mentioned and thats error correction, which is turned on when interleaving is applied. Theres little (read none) information from BT how they handle this, but they certainly do appear to have different levels of
error-correction.
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