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[Arksun]

So I finally joined the world of FTTC this year after my little village at last got brand new cabinets installed (previously all phone lines in the village were all direct to the exchange)

Service started in July and the stats for the whole of first month were excellent:


                      Upstream    Downstream
    Current Rate(kbps)   19999    79987
    Max Rate(kbps)        36029   126406
    SNR Margin(dB)         23.3    19.4
    Line Attenuation(dB)    0    10.4

However in August I started to notice the SNR Margin was dropping, by 17th of August the stats were:


                      Upstream    Downstream
    Current Rate(kbps)   19999    79999
    Max Rate(kbps)        34310   108765
    SNR Margin(dB)         15.1   13.1
    Line Attenuation(dB)    0    10.4

Fast forward to today 16th Sept the stats are currently:

                      Upstream    Downstream
    Current Rate(kbps)   19999    79999
    Max Rate(kbps)        33984   107937
    SNR Margin(dB)         15.1   12.8
    Line Attenuation(dB)    0    10.4


So my concern is this gradually shrinking SNRm which also reduces the potential Max rate.  Whilst this isn't encroaching into my 79999 sync rate yet, what if it continues to go down and does start reducing it?

Any ideas on why its been decreasing?  Could it be because when I signed up for FTTC I was one of the very first customers to get his line through the cabinet but more and more people are getting it now causing some interference?

Or could it be weather related, as things get cooler and more rain about. 
My VR26000 modem router has been on the same firmware and settings throughout, packet loss seems minimal.

[skyeci]

Probably more users being connected to the cab and reducing your lines performance. Crosstalkers...
Could eventually hit your sync if it gets really bad. My line was at 78mb. Now syncs at 70mb...

[Ronski]

As Skyeci says it's most likely caused by cross talk, given you're initial attainable values you are probably pretty safe 

Temperature and weather can also play a part in it, as can slowly developing faults. I'm pretty sure that BT also fiddles with power settings, masks to protect ADSL signals and other settings, I've seen my downstream fluctuate up and down, but basically stay the same, but my upstream has dropped substantially. What can you do about it, pretty much nothing unless there's an actual fault.

[skyeci]

Yeap agreed...oddly my us snrm was 12 last week. Had a resync and its now at 9.4..rather large drop...

[j0hn]

Your 1st guess sounds spot on, it's called crosstalk. Given your initial snrm and attainable I would be surprised if it ever dropped low enough to stop you syncing at 80/20.
Do you know if your cabinet is part of BDUK? You may be lucky enough to get vectoring enabled on your cabinet, which is a technology that mitigates the effects of crosstalk.

[Arksun]

Yeah suspected as much, thanks guys. Hopefully there won't be too many other new users going to it, they did install quite a few cabinets through the village and as they're no apartment blocks it hopefully won't get too overloaded!

I've no idea if its part of BDUK, how do I look it up?

[j0hn]

https://www.telecom-tariffs.co.uk/codelook.htm
lookup your postcode, note your cabinet number, click on the locality/name link, then click on show all xx fibre cabinets
It should tell you what cabinets are BDUK on that list

[skyeci]

http://www.kitz.co.uk/adsl/cabinet-lookup.htm#fttc_cab_info

[Arksun]

Thanks,  according to that website, my cabinet P7 is:

Phase:  Phase BDUK H&G 14b              
Properties Passed:  196      
Vendor:  Huawei