Thanks for the reply..


connection was 78mb ish back in July..

Now its down to 57mb... Openreach are saying its cross talk on the line..

Leaving the Cab 400m away its 80/20..

Of course it will be 80/20 at the cabinet - there will be minimal cross talk at that point and any that is there will only change the max attainable (at the cabinet) to be slightly reduced.

So when the ISP come back to me today I should be asking for the SNR to be looked at?

ISP's can't modify the SNRM on FTTC.

We need the exact sync/connection speed/(actual) rate reported by your router. That can give us a clue as to whether or not it is banded. That's why I asked for it at the end of my explanation about the two possible reasons for the high noise margin.

Cross-talk does not cause a high noise margin. It simply reduces the strength of the signal so reduces the maximum attainable.

How noise margin works was written for ADSLx but the basic principles apply to FTTC as well. What doesn't apply is that on FTTC ISPs cannot alter the noise margin, and can't ask for it to be altered, for the simple reason I ave earlier - it isn't used that way. A high margin is a result of banding or a sync at a noisy time.

Edit: On looking through the thread I notice MrSaffon has pointed out that a sync of 80/20 at the cabinet means the line is not banded. So - how long is it since you rebooted the router?

Edited by RobertoS (Mon 30-Jan-17 12:35:12)

I will get the numbers when I get home...

Understand the ISP cant change it, but they do have a case open with OR..

Last reboot was Sunday. We had a power cut for about 3mins..

So you are still having power cuts. How often?

Do you also have flickering lights sometimes, without a full power cut?

In reply to a post by scorpiouk:

on the SSE router there is no SNR number given, but there is a Noise Margin..

Thats currently sat 9.6db does that sound right for a FTTC line?

Cheers

What modem have SSE provided you? Does it give an exact sync figure? A banded line always syncs at the exact same figure, like 59,999 (it can change to the likes of 59,997 with interleaving). Some modems don't provide a correct sync figure though.

Line stats:

DSL Type VDSL2
DSL Mode Interleaved
Line Rate 20 Mbps 57.83 Mbps
Data Transferred 1365.11 MBytes 3651.34 MBytes
Output Power 5.6 dBm 5.6 dBm
Line Attenuation 0 dB 0 dB
Noise Margin 9.6 dB 6.2 dB

That doesn't look like banding, but the interleaving will be causing a loss of 8Mbps-11Mbps in your connection speed. It will also have added at least 8ms to your latency (ping). The engineer saying the line profile was 80/20 Fast simply means it wasn't banded at the time but I'm not sure if that "Fast" refers to Fast Path which you are not on or a lower level setting.

I may have asked this before - how long since you rebooted the router? I gather it was disconnected on Thursday but was it turned off at the time?

Your 9.6dB noise margin was a false alarm . That is the upstream value. The downstream is 6.2dB, pretty well exactly what it should be. I have my doubts about the correctness of the power figures - cheap router GUIs often get in a mess .

I think you are just suffering from bad cross-talk I'm afraid. That (or something) seems to be causing a high number of errors on the line which is why interleaving has kicked in.

There isn't an electricity substation close to the cabinet, your house, or the likely cable route is there? Or your television or anything else electronic near the DSL system?

Edited by RobertoS (Mon 30-Jan-17 23:36:41)