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[Mick]

I have been holding my breath for the last few days now.  As the days are growing longer signal strength has been improving all the time.  I am still waiting in hope that the DLM will auto-reduce my 9dB SNRM to 6dB.  Over the last couple of days I noticed that during day time the SNRM increases from 9dB to 10dB and during the night it does not drop as low as it used to.  If I were to resync now I would probably increase my sync speed and profile.  However, I am not sure if the higher SNRM that I now see will lead to an autoreduction - what shall I do?  Resync, or wait?

PS.  Green in the graph is the 9dB that I obtained last time I sync'ed.  The blue line indicates the real time changes in SNRM.

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[roseway]

I think it's best to re-sync as rarely as possible during this period, because each one will be a small extra item on the debit side, so to speak. Also, if you were to re-sync at a higher speed, this would quite possibly increase your error rate, which would be another debit.

[Mick]

Thanks roseway, I'll wait.  I hope that the error rate will otherwise stay low and eventually SNRM will reduce to 6dB.  18 days and counting ...

[Mick]

(Apologies for resurrecting this old thread, but I thought that my somewhat delayed conclusions may help others too).

So, I waited, ...  and waited ... and waited ... 

and nothing happened! 

Following the change of my service level from 'Super Stable' to 'Stable' my target SNR reduced down to 9 and I stayed there for ever.  Then months later with no target SNR auto-reduction I gave up and contacted my ISP once more.  I asked them to change my 'Stable' setting down to to 'Normal'.  Well, within 14 days I received the automatic resync from the exchange and suddenly I found myself running at 6dB SNRM and sync'ing at a full 7616Kb/s, which gives me a BRAS ADSL 6500.   

The error count has gone ballistic (see graph) at times higher than what I had previously experienced during lightning storms!  However, with the new setting of 'Normal' the line seems to have been stable, not losing its sync at all.  This is despite some line cross talk which significantly increases the error count during 4-5 days a week.  I have been running now for more than a month and have a stable connection and the highest sync speed that my 20CN connection will support with Interleaving on.

So, having been around the houses I have concluded that the first thing to tweak for achieving and holding onto higher sync speeds is the service stability level.  'Super Stable' requires a very quiet line/strong signal, or you'll soon find yourself locked at a high SNRM and not being able to get rid of it.  If you have a high attenuation you may not be able to hold onto a 'Normal' setting and a 6dB SNRM, in which case a 'Stable' setting with 9dB is the best you can hope for.

Hope this helps others and their deliberations with their ISP. 

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[waltergmw]

Hi Mick,

If you can hear audible cross talk you should be able to report a telephone line failure to BT, not mentioning the broadband service at all.

The fact you have lots of forward error correction counts shows that the modem is working hard for you.
It's the other error types which can be more of a nuisance.

Kind regards,
Walter

[Mick]

If you can hear audible cross talk ...

Thanks Walter,

I'm afraid that the cross talk is in the inaudible range.  The only way I know that it is/not happening is when the offending household are on holiday, or have switched their modem off.  At those times I can see my errors dropping from hundreds or thousands down to zero and consequently my sync speed and SNRM improving.  These guys are costing me 1dB in terms of SNRM and a couple of hundred of kb/s sync speed, but there's nothing much I can do.  When I spoke to a BT guy he said that they have no spare loops in the pipe for my area.

Anyway, with the 'Normal' option setting I can get full speed at last, which makes me a very happy camper.

[4candles]

On theory I have is that, because my line is so much improved (just by cutting the bell-wire) since the 10-day period, DLM can increase the target without me getting anyware close to my FTR.  And just maybe, because I'm syncing at a long way above my recorded FTR, DLM is less inclined to give back my margin.

I'd be inclined to believe that. After a line fault in May 2009, my target margin went from 6 to 12dB. Despite holding sync for long periods with low error rates, nothing happened for nearly 6 months, until I lost service due to a MUX fault in the exchange. When that was fixed, the target margin reduced to 9dB almost immediately, then to 6dB within a few hours.

Earlier this year it occurred to me that as my wiring arrangements were less than ideal on commencement of ADSLMax, my FTR would be pretty low - 2278 as it turned out, though my sync is now around 5000. I therefore asked Plusnet for an SNR reset, after which the FTR was 4096.

A few weeks ago, I had a short period of temporary and unexplained high errors, which upped the target margin to 9dB. When the errors returned to the normal low rate, the target margin went back to 6dB in about 14 days.