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Administrator MrSaffron
(staff) Tue 26-Mar-13 20:07:15
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Re: Switching to BT - My Experiences


[re: matthewcl375] [link to this post]
 
Not weird at all, the noise environment is a fluctuating beast.

If you were to plot all the DMT bins you would probably be able to spot the variations, but that is going into detail I that would blow your mind

Andrew Ferguson, [email protected]
www.thinkbroadband.com - formerly known as ADSLguide.org.uk
The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User 4M2
(fountain of knowledge) Tue 26-Mar-13 20:17:14
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Re: Switching to BT - My Experiences


[re: matthewcl375] [link to this post]
 
I believe there are further complex factors involved other than attenuation, SNRM and power. But after a resync and the stat numbers look about right you should be fine.

Be patient and just allow the connection to settle.
Standard User XRaySpeX
(eat-sleep-adslguide) Tue 26-Mar-13 20:18:42
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Re: Switching to BT - My Experiences


[re: matthewcl375] [link to this post]
 
In reply to a post by matthewcl375:
the only thing that has changed is a 0.1dbM increase in downstream output power
You've been told repeatedly: stop concentrating on minuscule changes and even attributing significant effects to them. Just ignore them; they are effectively equal.

1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 20 Meg WBC


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Standard User matthewcl375
(member) Tue 26-Mar-13 20:54:32
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Re: Switching to BT - My Experiences


[re: 4M2] [link to this post]
 
I will. That's all I can do now tongue

FYI I have found out my sync time SNR Margin is definitely 9db, for some weird reason
Standard User 4M2
(fountain of knowledge) Tue 26-Mar-13 21:13:48
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Re: Switching to BT - My Experiences


[re: matthewcl375] [link to this post]
 
In reply to a post by matthewcl375:
I will. That's all I can do now tongue

FYI I have found out my sync time SNR Margin is definitely 9db, for some weird reason


That's normal: 3, 6, 9, 12dB's at sync time, then there will be some variation throughout the period of connection. As you previously found with C&W an after-dark margin may be less than a day time one during the same connection period due to noise.

Personally I like to sync when it's dark and then I get a larger margin which is great for stability but the downside is I loose a little sync speed.

As you can see http://farm9.staticflickr.com/8250/8592685799_490d8b... my line gets a little noisy at night smile

Edited by 4M2 (Tue 26-Mar-13 21:39:29)

Standard User matthewcl375
(member) Tue 26-Mar-13 22:01:39
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Re: Switching to BT - My Experiences


[re: 4M2] [link to this post]
 
Yeah I just thought 6db was the BT default which it would try first during the 10 days...

And lol that's quite some noise there
Standard User 4M2
(fountain of knowledge) Tue 26-Mar-13 22:06:53
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Re: Switching to BT - My Experiences


[re: matthewcl375] [link to this post]
 
A 9dB SNRM should be fine on your short line...sorry I don't know what the BT default margin is.

Ah, but my attenuation is 6x more than yours LOL!
Standard User ryant704
(regular) Tue 26-Mar-13 22:15:10
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Re: Switching to BT - My Experiences


[re: 4M2] [link to this post]
 
I believe 6 is the default(target) SNR.

Edited by ryant704 (Tue 26-Mar-13 22:15:21)

Standard User chris6273
(committed) Tue 26-Mar-13 22:56:02
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Re: Switching to BT - My Experiences


[re: matthewcl375] [link to this post]
 
In reply to a post by matthewcl375:
Yeah I just thought 6db was the BT default which it would try first during the 10 days...

And lol that's quite some noise there


It depends. The DLM will be trying your line on each Target SNR starting from 6/9dB and getting lower until it hits one which results in an unreliable connection/high error count; It's the way it works.

When I was transferred over to 21CN equipment I started off with a 7.4dB SNR Margin and after 3 days the DLM tried my line on a 3dB SNR Profile which I'm still on.

The DLM is programmed to try out each profile for a certain amount of time before it tries the next step; it's all a matter of waiting.

One thing I am interested in however is the Interleaving which is currently applied to your line. That indicates a high error count at some point has occurred or the connection has been unstable. As far as I know the DLM starts off connections on Fast Path and enables interleaving if there is a high error count or if the connection drops out too many times. Bearing in mind your Attenuation readings I would expect a fresh DLM profile to try you out on Fast-Path first...

-------------------------------------------------------------------
My Broadband Speed Test

Downstream Upstream
Connection Speed: 22494 kbps 1211 kbps
Line Attenuation: 16.0 db 9.7 db
Noise Margin: 2.6 db 6.7 db

Telewest (2004-2006): 256Kbps -> 512Kbps
BT (2006 - Present): 8128/448Kbps on 20CN Alcatel DSLAM -> 22494/1211Kbps on 21CN Huawei MSAN

Edited by chris6273 (Tue 26-Mar-13 22:59:52)

Standard User matthewcl375
(member) Tue 26-Mar-13 23:05:29
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Re: Switching to BT - My Experiences


[re: chris6273] [link to this post]
 
Not sure regarding the interleaving, I'm pretty sure my line could support fast path, I mean DSLs been up for nearly 5 hours, with only 2 FEC Events Down and 44 Up, so I see no need for interleaving but somewhere the DLM does crazy
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