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Message 1 of 42

Noise Margin Reduced.

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Not so much of a problem, but a comment.

My HH6 downstream noise margin has been reduced gradually, over 3 days, from an initial setting of 6.0dB down to what is now 3.0dB.

Reduction was definitely not in a 3dB step, so it seems to be a bit strange.

Uptream noise margin remains at 6.0dB. There were, however, reboots every 2 days.

 

There was a news article in November, not widely published, that BT would start reducing noise margin from March this year.

Infinity 2 speeds are now up from 51mbps to 59mbps.  The change isn't really noticed, but it may help in streaming HD.

 

Anyone noticed this?

 

 

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Distinguished Sage
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Message 2 of 42

Re: Noise Margin Reduced.

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No, but interestingly SIN498 has been updated with the following paragraph

 

1.2.2 VDSL2 noise margins


Currently the default target downstream noise margin is set to 6dB. From March 2017 the target downstream noise margin shall be set to either 3, 4, 5 or 6dB – the actual value shall be determined by the Dynamic Line Management (DLM) algorithm based on line stability.

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Message 3 of 42

Re: Noise Margin Reduced.

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Pretty common knowledge on other forums.
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Message 4 of 42

Re: Noise Margin Reduced.

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@licquorice wrote:

No, but interestingly SIN498 has been updated with the following paragraph

 

1.2.2 VDSL2 noise margins


Currently the default target downstream noise margin is set to 6dB. From March 2017 the target downstream noise margin shall be set to either 3, 4, 5 or 6dB – the actual value shall be determined by the Dynamic Line Management (DLM) algorithm based on line stability.


This fits with the events, as noted.

There's been a remote reboot evey 2 days since Thursday last.

Reboot ime is around 5-41AM, long before my electric shower time, street lights, etc.

There was a Sunday reboot at 9-10AM.

Otherwise the Hub itself performs well, after problems in the early days, before Firmware updates. 

 

"Other Forums" will be not BT probably?????

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Message 5 of 42

Re: Noise Margin Reduced.

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No but there's a number of posters who work with Openreach who have confirmed briefings, along with other posters whose DSL stats marry up to the trial that was announced a while back.

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Message 6 of 42

Re: Noise Margin Reduced.

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@Webby wrote:
No but there's a number of posters who work with Openreach who have confirmed briefings, along with other posters who's DSL stats marry up to the trial that was announced a while back.

Found your post on the Forums. (I remember it, but it didn't sink in at the time.)

Thanks.

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Message 7 of 42

Re: Noise Margin Reduced.

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Reducing the SNRm represents a two fold "gain" in my view. BT will use less energy by reducing margins, and EU's should see an increase in linespeed, proportionately. And DLM which will have clearly been adjusted to compensate ... will attempt to "mend" any troublesome connections. My guess is ... not all will benefit from it, as even with stable 6db margins some lines just don't hack it. And that is where line history will come into play, as to what margin is set by the MSAN/mux.
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Message 8 of 42

Re: Noise Margin Reduced.

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@Webby

 

Statistics for hub, as requested.

The downstream noise margin fluctuates during the day, but the HH6 has, in the past, proved to be reasonably tolerant.

There's going to be some more waiting time, to see if these speeds will hold!

They are now back to November 2015 levels for Infinity 2.

 

This is a list of your BT Smart Hub settings and current statistics.

BT Hub 6A

SG4B10002244

17-Dec-2016

-

1.0

1.32.0

2 Days, 3 Hours 59 Minutes 52 Seconds

12.98 kbps / 59.68 kbps

12982 / 58516

5.9 / 2.9

17.7

0 / 177

-

0/38

G_993_2_ANNEX_B

Fast Path

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Message 9 of 42

Re: Noise Margin Reduced.

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Hi,

 

Again no problem but just to add to what has already been said.  My noise margin used to be relatively stable at ~6.3/6.8.

Then a while back it dropped to ~4.9/4.4.  But it has now returned to 6.2/6.7.

As @RogerB explained elsewhere I guess i'm more of an amber than a green.

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Message 10 of 42

Re: Noise Margin Reduced.

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Just to keep things going:-

My noise margin has increased to 3.4db downstream. Only lost 1mbps speed, though.

This followed a routine remote 14 day reboot 2-00am Friday morning 10-03-17.

Had hoped that at this scheduled time the noise levels would be at their lowest, and would result in a lower daytime margin. 

Apparently not so!

 

There's more waiting yet...to see how long this 3db is to be maintained.

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