Hi,
I had ADSL switched over to FTTC about a month ago and have been trying to get a very low upstream rate diagnosed. I'm 1.9km from the cabinet and downstream is very good at 16M (was ~9M on ADSL), but upstream is very poor at ~538k (was double that at ~1037k on ADSL).
So trying to figure out this upstream loss has been very interesting. Since the copper hasn't changed, and the downstream is very good, and Plusnet have been very good at trying to isolate any faults (including an unbalanced phone line to the exchange), I'm left with "that's all the line can do". But of course I know it can do more, since ADSL was better on a ~3km line. VDSL2 uses the same US0 bins as ADSL2+, and even has a higher potential power level, so what could be going wrong?
Well I've noticed that the upstream PSD, as reported by my Draytek 2860, does vary quite a lot - despite the upstream rate never really changing. The table below hopefully shows this:
Date PSD SNR kbps
18/1/17 9.6 7 528
3/2/17 9.6 7 528
6/2/17 9.0 7 528
11/2/17 8.7 8 538
11/2/17 9.4 8 538
12/2/17 9.6 7 535
14/2/17 8.9 8 542
17/2/17 9.6 7 538
19/2/17 9.1 7 538
19/2/17 9.2 7 538
20/2/17 9.5 7 531
21/2/17 9.8 7 535
22/2/17 9.5 7 528
(The Draytek modem doesn't give a decimal point value for the SNR, so '7' could be '7.9'.)
So, despite the PSD varying from 8.7dB to 9.8dB, the upstream rate only varies from 528k to 542k.
It's as if the ECI cabinet (yes, I know... I'm already damned...) has 'decided' that ~530k is what should be aimed for and the PSD for my modem is adjusted to achieve this (using Upstream Power Back Off?).
Does this sound right? Anyone come across anything like this. ECI firmware is 0xd086, with no G.INP.
Thanks,
Richard