Well, my connection is now in sync at only 20764/4859 Kbps.
It has reduced in 3 steps to that level since December 2012.
In December, sync speeds were 29430/5704 Kbps, where they had more or less been for the 7 months since my connection was finally repaired near the end of May 2012.
DS Attainable rates have gone from 34Mb to 21.5Mb
Here's a before & after set of snapshot graphs:-
The really obvious differences are Bitloading, QLN & SNR.
However, I can also see slight deterioration in the Hlog graph, along with slightly increased attenuation as reported via the pbParams data.
I also notice that TX Power has reduced slightly.
Right up to May 1st 2013, Interleaving depth had been around 400-500 DS & 1 US since it was applied a few days after DLM was reset back in May 2012.
When the connection resynced on the fly at 04:54 May 1st at speeds of 24802/5172 Kbps, DS Interleaving was switched off completely.
INP & delay were also set to zero at the same time.
This was quite surprising as my 1000m connection does usually seem to need Interleaving, INP & delay to be applied at reasonably low levels.
There had been quite a few resyncs since 1st May, until appearing to settle at such low sync speeds.
I presume such low speeds no longer require Interleaving, INP & delay setting.
I disconnected all internal extension telephony wiring, switched the mains power off in my house & actually ran the connection for a while via a car battery & a battery powered laptop.
This made absolutely no difference to the stats obtained when fully mains powered, so I assume nothing in my own house can be causing such deterioration in speeds & stability.
Now, my question is, can this really all be down to increased crosstalk or is it possible that either something else has gradually caused QLN to deteriorate or is some sort of a line 'fault' brewing?
I have no idea how many users between the cabinet & my house have broadband connections or even which flavour(s) of DSL they are using.
I also have no idea how to discover if there has been an increase in the number of broadband users, coinciding with the dates I noticed a deterioration.
Does anyone have any ideas/suggestions?
I don't believe requesting DLM to be reset would have any mileage (even in the unlikely event that such a request would be granted), particularly as Attainable rates are so low & there doesn't really appear to be much in the way of spare SNRM.