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Author Topic: horrible burst of errors then capped and strange stats  (Read 4221 times)

les-70

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Re: horrible burst of errors then capped and strange stats
« Reply #15 on: May 20, 2014, 07:00:31 PM »

  I understand the respective values of the syncs.  It is the change in the attainable values  that puzzles me.  The interleaved value was 5Mb/s higher.
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Chrysalis

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Re: horrible burst of errors then capped and strange stats
« Reply #16 on: May 20, 2014, 07:46:40 PM »

its something that always seems to occur, interleaved lines report higher attainable, I have some theories but they only theories.
Also I have only observed this behaviour on BT owned equipment not sky/easynet/BE.

1 - Interleaved lines get favourable power masking as they seen as needing a "bit of help" to work well.
2 - The modem miscalculates attainable rates.
3 - The interleaving technology actually gives superior snr. (this I observed when I used to use DMT on BT adsl max), I was watching my line one night when it was scheduled to go back to fast path, I watched it go offline for a couple of seconds, and then come back, the snr per tone was a few db lower across the entire range when it came back on fast path. this could be due to #1 tho.  This observation I had in DMT makes #2 less likely.
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Bald_Eagle1

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Re: horrible burst of errors then capped and strange stats
« Reply #17 on: May 20, 2014, 08:54:25 PM »

I think I understand all the values except the significance, if any, of the change in attainable from 78 to 83.  Maybe it is just a quirk of how the values are estimated in the two states?



I don't profess to understand why, but we always see such a difference whenever interleaving is applied.

It would appear to be physically impossible to ever achieve the higher speeds.


The only exception to this rule is when a connection resyncs at a particularly quiet period, when sync speed gets 'close' to attainable rate.

On those occasions, we often see sync speed maintained, but attainable rate becoming lower than sync speed when noise increases i.e. when SNRM reduces, currently below 6 dB in the case of VDSL2 connections.

Here's a recent example from my connection:-

Max:   Upstream rate = 4027 Kbps, Downstream rate = 21148 Kbps
Bearer:   0, Upstream rate = 4516 Kbps, Downstream rate = 22271 Kbps



DLM clearly didn't like that after approximately 24 days as the connection resynced & ended up like this:-

Max:   Upstream rate = 4216 Kbps, Downstream rate = 21268 Kbps
Bearer:   0, Upstream rate = 4245 Kbps, Downstream rate = 18858 Kbps



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NewtronStar

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Re: horrible burst of errors then capped and strange stats
« Reply #18 on: May 22, 2014, 06:07:16 PM »

I think the best time to resync the Hg612 would be when Max Attainable is at it's lowest value, this will give you a higher SNRM to overcome any evening noise though your Bearer will Sync lower thats the trade off.

But the DLM keeps butting it nose in and then retraining at silly times like 2am 4am or 7am when the lines are quiet so by the evening SNRM will start to drop and hay ho the errors start accumulating  ::)
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