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[waltergmw]

Hi kai and welcome,

Your performance certainly doesn't look outstanding. Could I suggest you run routerstats and DMT tool so we can see what sort of noise profile you have and what frequencies, if any, are causing a particular problem.

http://www.kitz.co.uk/routers/log_routerstats.htm

http://www.kitz.co.uk/routers/DMTv7.htm

Kind regards,
Walter

[kai]

Thank you for the quick response. I've attached a screenshot of DMT to my original post. I've just this moment taken a look at RouterStats. I understand it's a logging program to track changes in my line stats over a period of time.

What exactly should I be logging? Just  the RX and (downstream) sync values? And also for how long and what kind of interval should it be set at to give a good insight of what's going wrong?

Many thanks for your help so far.

[waltergmw]

Hi Kai,

(Sorry I missed your DMT off the bottom of my page.)
Do you believe your actual line length is within the figures quoted by DMT ?

You might monitor the downstream noise margin to look for variations and spikes over weekdays and weekends.

The Gurus will probably have some other ideas.

Kind regards,
Walter

[jid]

Hi Kai,

Looking at the stats, your line had only been up for just under an hour and it is experiencing a lot of CRCs in that short space of time, works out about 14 per minute.

The more CRC errors you have, the slower your throughput becomes, CRCs are data that need to be resent as the router cannot "hear" the exchange. The presence of Upstream CRCs also shows there is noise present on the line.

As walter has already mentioned, there is noise present. However, looking at those stats, I am not sure what your Target SNR margin is, however if its 6dB then you have 0.5dB spare which obviously isn't enough for your line.

Now in my opinion, your line is very long for ADSL2+ to have any difference, and you may benefit from just using ADSL on the line.
Any line over 40dB (I believe) doesn't have any huge difference in speed compared to ADSL. As ADSL2+ uses higher frequencies which are more prone to noise, you are seeing the CRC errors and possibly slow speeds.

I am sure some of the gurus on here will correct anything I have mis-interpreted. 

Regards

Jamie

[Weaver]

I'm assuming that you've already tested with your router straight into the test socket (front plate of NTE5 removed).

Your point about voice being poor is a good one. Test with a phone straight into the test socket, and of course try two phone models. If other people can't hear you, but you can hear them, then it could be a rubbish phone (my BT Diverse DECT phone had this problem, me being inaudible to other people). If the speaking clock sounds quiet to you, phone up your voice/home phone service provider and ask them to turn up the gain.

I don't know if the (voice) voltage gain being low might be linked to a DSLAM tx power being also set too low for you too?

[Mick]

Looking at the stats, your line had only been up for just under an hour and it is experiencing a lot of CRCs in that short space of time, works out about 14 per minute.

This is a bit of a moot point.  The threshold at which the modem/BT exchange will consider that the link is too noisy and resync to stabilise the line is not published anywhere (AFAIK).  Furthermore, the CRC threshold is different depending on the line's Service Setting.  In the past, on a "super stable" setting I have experienced resyncs at counts lower than 14 per minute.  Now on "stable" setting I reached 11,520 (yes!  11.5k per minute) as a result of a noise burst and despite this the line did not drop.  I am not clear how the loss of signal is established, but I am assuming that algorithm that considers the absolute count as well as the rate of increase/duration.  So short bursts may be OK, but prolonged noise storm may produce a resync at lower maximum counts of CRCs.  To top it all up the modem/BT exchange combination of chipsets also has an influence on all this.  This is why I am saying that this is a moot point.  Notwithstanding this, and to state the obvious ... the higher the CRCs the noisier the line.

The more CRC errors you have, the slower your throughput becomes, CRCs are data that need to be resent as the router cannot "hear" the exchange.

Theoretically yes, but practically I think that your modem will drop the line before you are able to notice a slow down in troughput on the basis of CRC counts alone.