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Attainable rate

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Weaver:
Kitz has already talked about ‘attainable rate’ in the page on line stats. However I don't understand the point about DSLAM restrictions etc. Could anyone help me understand?

ejs:
The max attainable rate ignores any rate caps, such a banded profile applied by the DLM, or the FTTC speed tier (which, at this level, would be exactly the same type of cap).

The max attainable rate will take into account the target SNRM.

re0:
It may be worth noting that during periods where the background noise increases to a point where the noise margin for the communications (DSL) drops below the target margin then it is not unusual to see the modem showing a max attainable below that of the current sync. The max attainable usually gives a good indication of the best times to resync for the highest speeds at your current target margin.

Sorry if I am just repeating what you already have in knowledge.

aesmith:
I think attainable rate also assumes some standard distribution of frequencies.  Or maybe idealised for combination of attenuation and noise margin.   So for example my router at the moment is connected at 4000K, target noise margin is 6dB, actual is 5.4dB.   Attainable rate reported as 4544K.

ejs:
I'm pretty sure the modem will use the measured SNR per tone to calculate the attainable rate.

With FEC+interleaving, the attainable rate calculation does not need to meet the min INP constraint, but of course the actual rate will have to, so then the attainable can end up higher than the actual. You can gain more bandwidth from the FEC/interleaving coding than the bandwidth used to carry the FEC data.

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