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Author Topic: Auto reduction in target noise margin  (Read 29855 times)

sevenlayermuddle

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Re: Auto reduction in target noise margin
« Reply #15 on: March 02, 2009, 04:25:49 PM »

At 10:30 this evening my target noise margin dropped by another 3 dB. There have been a couple of random re-syncs during the last couple of weeks, so clearly a continuous connection isn't needed; but the error rate has been consistently low (about 2 errored seconds per hour) and this appears to be the main requirement.

That's interesting. 

It's also interesting that it seems to reconnect automatically after a drop, so there's no need to manually reconnect once in a while (with the risk of appearing even less stable) to "see if it's changed yet", as I had believed to be the case?
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roseway

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Re: Auto reduction in target noise margin
« Reply #16 on: March 02, 2009, 06:35:04 PM »

Yes, on both occasions there was a re-sync which had no apparent reason from my side, so I'm assuming that it was triggered from the other end when the target was reduced. I can't say that for certain though, but it seems likely.
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  Eric

kitz

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Re: Auto reduction in target noise margin
« Reply #17 on: March 04, 2009, 12:47:41 PM »

Quote
so clearly a continuous connection isn't needed; but the error rate has been consistently low (about 2 errored seconds per hour) and this appears to be the main requirement.

Thanks for that eric, I had seen mention of this before...  and therefore thanks for confirming the first hand situation that you experienced.

Quote
there was a re-sync which had no apparent reason from my side, so I'm assuming that it was triggered from the other end when the target was reduced.

The auto resync is an interesting observation.


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roseway

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Re: Auto reduction in target noise margin
« Reply #18 on: March 17, 2009, 03:16:49 PM »

At about 15:00 my connection re-synced and came up with a further 3 dB drop in the target noise margin. It's now fallen all the way back to the default 6 dB. I've set the noise margin tweak value back to 100% (i.e. no tweaking).

The 3 dB drops occurred at just over 14-day intervals, so that certainly seems to be one of the parameters, together with a low error rate. This all tends to confirm that the oldish patent document which 7LM discovered ( http://www.freepatentsonline.com/EP1953959.html  ) does in fact describe the process.
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  Eric

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Re: Auto reduction in target noise margin
« Reply #19 on: March 17, 2009, 09:17:06 PM »

>>> It's now fallen all the way back to the default 6 dB.

YAY  :thumbs:

>> The 3 dB drops occurred at just over 14-day intervals, so that certainly seems to be one of the parameters, together with a low error rate. This all tends to confirm that the oldish patent document which 7LM discovered

Thank you ever so much eric for recording your observations :)
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BritBrat

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Re: Auto reduction in target noise margin
« Reply #20 on: March 18, 2009, 09:41:43 AM »

I have been getting these as well and I am also using the DGteam firmware.

Set at 110% Noise Margin 7 Connection Speed 6,500
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roseway

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Re: Auto reduction in target noise margin
« Reply #21 on: March 18, 2009, 10:31:20 AM »

Your stats look very similar to mine. I've certainly found that the DG834GT with DGTeam firmware seems to be an exceptionally stable combination on my line.
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  Eric

sevenlayermuddle

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Re: Auto reduction in target noise margin
« Reply #22 on: March 18, 2009, 10:54:21 AM »

One thing that worries me about all this might (note:'might' as I'm only speculating) be...

The evidence suggests that Eric's 2 ES per hour is categorized as 'very stable'.  We've no way of knowing where they draw the line wrt error rates and the 'very stable' category, but taking my own line as an example, I tend to get several hundred ES per day and I've given up all hope of ever seeing a target reduction, and that's with an effective target that's tweaked to around 11-12dB.

But forgetting about my specific line, and thinking about the general case... how likely is it that a long line (say circa 55dM attenuation) is ever going to get error rates like Eric's, even with SNR margin of 15dB...?   And hence how likely is such a line will ever get a DLM target reducion?

...which leads to my concern that we might have a situation where DLM would be a one-way ticket for long lines.  The 'instability' of ten resynchs in an hour gets you promoted to a high margin, but there may be very little chance of ever satisfying the 'very stable' criteria that gets it reduced again, ot at least not beyond the initial reduction from 15 to 12.


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roseway

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Re: Auto reduction in target noise margin
« Reply #23 on: March 18, 2009, 11:12:30 AM »

I think your concern is probably well founded. But there is a proposal to give users the capability to manage their own target noise margin to a certain extent. There's a discussion about it here.
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  Eric

sevenlayermuddle

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Re: Auto reduction in target noise margin
« Reply #24 on: March 18, 2009, 11:19:28 AM »

I think your concern is probably well founded. But there is a proposal to give users the capability to manage their own target noise margin to a certain extent. There's a discussion about it here.

Thanks for that link, I'd somehow failed to spot that entire discussion.  Fascinating stuff.
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joss

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Re: Auto reduction in target noise margin
« Reply #25 on: April 12, 2009, 06:03:30 PM »

Hello all

Just found this thread and found it interesting reading, however much went above my head.

With regards to the DG834GT and TeamDG firm ware and SNR margins, I make the assumption your talking about the advanced ADSL settings tab ?

I have looked, but not made any changes here. I would be interested to know what settings you have found work well under this tab.

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Joss

roseway

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Re: Auto reduction in target noise margin
« Reply #26 on: April 12, 2009, 08:27:28 PM »

What setting you use depends on where you're starting from. If you set the slider to the minimum position (1%) it reduces the target margin by about 5 to 5.5 dB. So if you're already at the default of 6 dB, then using this setting will almost certainly make your connection unstable. But if previous events have resulted in your target noise margin being increased to the maximum 15 dB, then the minimum setting on the slider will bring it down to about 9.5 dB which make a big improvement in your connection speed without seriously risking stability.

An in-between setting of 50% on the slider reduces your target noise margin by about 3 dB, which will give you maybe 400-600 kbps increase in your connection speed.

So if you want to have a play with the slider, what you really need to do is experiment with fairly small changes at a time. But don't do it too frequently (not more than once an hour, I suggest) otherwise you are likely to cause DLM to flag your connection as unstable, and raise the target margin further.

[Edited for English :) ]
« Last Edit: April 13, 2009, 04:13:25 PM by roseway »
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  Eric

joss

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Re: Auto reduction in target noise margin
« Reply #27 on: April 13, 2009, 10:03:38 AM »

What setting you use depends on where you're starting from. If you set the slider to the minimum position (1%) it reduces the target margin by about 5 to 5.5 dB. So if you're already at the default of 6 dB, then using this setting will almost certainly make your connection unstable. But if previous events have resulted in your target noise margin being increased to the maximum 15 dB, then the minimum setting on the slider will bring it down to about 9.5 dB which make a big improvement in your connection speed without seriously risking stability.

An in-between setting of 50% on the slider reduces your target noise margin by about 3 dB, which will give you maybe 400-600 kbps increase in your connection speed.

So if you want to have a play with the slider, what you really need to do is experiment with fairly small changes at a time. But don't do it too frequently (not more than once an hour, I suggest) otherwise you are cause DLM to flag your connection as unstable, and raise the target margin further.


Thanks Eric for the above.

I guess I am after line stability more than anything. Periodically I would lose sync in the early hours due to low SNR. What I hope to achieve is to try and prevent this drop of sync.
Hopefully if achieved my bras profile will become more stable, instead of fluctuating every few days.

0   6000   6816   adsl6000   Auto   06-Apr-2009 03:38   06-Apr-2009 03:38
448   7000   7968   adsl7000   Auto   03-Apr-2009 08:56   03-Apr-2009 08:56
0   5500   6240   adsl5500   Auto   03-Apr-2009 01:14   03-Apr-2009 01:14
0   7000   7968   adsl7000   Auto   02-Apr-2009 12:17   02-Apr-2009 12:17
448   7150   8128   adsl7150   Auto   29-Mar-2009 00:15   29-Mar-2009 00:15
0   6000   6816   adsl6000   Auto   22-Mar-2009 00:16   22-Mar-2009 00:16
448   7000   7968   adsl7000   Auto   16-Mar-2009 00:15   16-Mar-2009 00:15
0   6000   6816   adsl6000   Auto   12-Mar-2009 05:08   12-Mar-2009 05:08
448   6500   7392   adsl6500   Auto   06-Mar-2009 10:09   06-Mar-2009 10:09
0   5500   6240   adsl5500   Auto   28-Feb-2009 23:56   28-Feb-2009 23:56

Downstream RX
Noise Margin:     6.9   dB
Connection Rate:  7680  Kbps
Line Attenuation: 28.0  dB
Power:            19.8  dBm
Max Rate:         8416  Kbps
 
SF:               74634
SF Errors:        1
Reed Solomon:     10150288
RS Corrected:     879
RS Un-Corrected:  25
HEC:              1
Errored Seconds:  186
Severe ES:        1
Interleave Depth: 64

Upstream TX
Noise Margin:     21.0  dB
Connection Rate:  448   Kbps
Line Attenuation: 15.5  dB
Power:            12.0  dBm
Max Rate:         1112  Kbps
 
SF:               75813
SF Errors:        0
Reed Solomon:     644410
RS Corrected:     0
RS Un-Corrected:  0
HEC:              0
Errored Seconds:  0
Severe ES:        0
Interleave Depth: 4

Totals
Total Up Time (As Reported):
 1 days 41 min 0 sec
 
CRC:  387
LOS:  0
LOF:  0
ES :  186


Bytes Transferred (ppp0):
  Tx: 68378802 (65.2 MiB)
  Rx: 688845447 (656.9 MiB)

  IP address: 82.69.119.122
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Joss

jeffbb

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Re: Auto reduction in target noise margin
« Reply #28 on: April 13, 2009, 12:39:16 PM »

Hi

It is a mystery how the SNR margin changes . these are some of my stats
Noise Margin:     6.3   dB   lowest 5.9 highest 9.1
this varies in  steps of 1 to 2 db as if something/s is coming on or off no fixed times
Connection Rate:  6912  Kbps
Line Attenuation: 33.0  dB
Power:            19.8  dBm
Max Rate:         7712  Kbps


Total Up Times (From SF counts):
 WAN:   12 days, 02:03:09
 LAN:   12 days, 02:03:43
 
CRC:  58
LOS:  0
LOF:  0
ES :  45

And before this I had a 4week run with similar error rates  rates. I rebooted to see if the marging had dropped .It hadn't . My target is still 12 db.I have tweaked it down to 9db using Routerstats .So altogether its been over 6weeks since the last Target change from 15 to 12 . :(
regards Jeff
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Mick

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Re: Auto reduction in target noise margin
« Reply #29 on: April 13, 2009, 03:50:32 PM »

I have a loose theory on the automatic reduction of the target SNRM (or should I say a loose understanding of it?  :P )

So, here goes: 
it seems that the 14 days intervals will work as has already been reported by roseway and a lower SNRM will arrive including a resync at a higher connection speed, but this is affected by the current service option setting at the local exchange, of 'normal', 'stable', 'super stable'.

I believe that the counts of FECs, CRCs, or errored seconds, etc. are not absolute, but relative to the service option that the line has assigned to it.  So, with the same error counts you could have a higher sync speed (and achieve an automatic resync to a lower SNRM) if your service option is 1, but won't if your service option is 3.  Now if you live next to the BT exchange a setting of 3 will not affect your speeds, but on a longer line you'll probably be on a loser and will soon be bounced to a high noise margin with no chance of achieving an automatic reduction (because your error counts will be deemed unacceptably high on a service option of 'super stable').

I moved ISPs and the new ISP mentioned somewhere in their literature that all new connections are as a default set to 'super stable' for maximum line stability.  I didn't pay attention to this, but within a week or two from moving I started having resync events and in no time at all ended up with an unshakeable 15dB SNRM.  Even when I asked the new ISP to manually reduce the target SNRM from 15 to 9dB, within a couple of days the DLM jumped up to 15dB in a single step.  I am assuming that my previous ISP had reset my connection to normal after I asked them to reset my target noise margin to default 6dB, because I used to have 6dB SNRM and 7616 kbps sync speeds for months and months on end, until I joined the new ISP.

I have now asked my new ISP to change the service option from super stable to stable - will report back how it goes.

Using routerstats or modem commands to force the SNRM lower than what the DLM is offering is essentially working against the logic of the system.  If my theory is correct then it may be a better solution to reset the service option to 2 or 1 via the ISP support desk - unless the line is soooo noisy that it will soon end up dropping the connection.  If the latter is true then the line will have drop outs with routerstats anyway and a 'stable' or 'super stable' choice may be necessary to make the connection usable.
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Regards,
Mick
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