FTTC just installed, speeds below the estimates, next steps?

So after a little negotiation with BTO and PlusNet, I am not connected to FTTC.

On ADSL I used to get connected at about 3Mb line speed. 55dB attenuation.

On VDSL I am now connected at about 1.9Mb line speed, I will show you the stats from an unlocked HG612 in a moment. Sometimes it will connect at 3.5Mb but it will not stay connected for long. Frequently the modem may sync at just 0.5 to 1.2Mb, the SNR per tone graph on dslstats shows there is periodic noise on the line.

There are 2 new BDUK funded cabinets in the village.

It is about 2km on the E-side of the cabinet and about 1.6km to my home via the road, and the phone lines mostly follow that road, if anything they take a shorter route cutting off one of the corners en-route. The JDSU used by the BTO guy also showed it was 1.6km.

So the stats from the HG612 are currently.

xdslcmd info --pbParams
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 2
Max: Upstream rate = 1061 Kbps, Downstream rate = 3164 Kbps
Path: 0, Upstream rate = 1065 Kbps, Downstream rate = 2276 Kbps

Discovery Phase (Initial) Band Plan
US: (0,95) (868,1207) (1972,2783)
DS: (32,859) (1216,1963) (2792,3959)
Medley Phase (Final) Band Plan
US: (0,95)
DS: (32,859) (1216,1963) (2792,3959)
VDSL Port Details Upstream Downstream
Attainable Net Data Rate: 1061 kbps 3164 kbps
Actual Aggregate Tx Power: 10.5 dBm 4.6 dBm
============================================================================
VDSL Band Status U0 U1 U2 U3 D1 D2 D3
Line Attenuation(dB): 16.7 N/A N/A N/A 32.4 66.4 0.1
Signal Attenuation(dB): 16.7 N/A N/A N/A 32.4 66.4 0.1
SNR Margin(dB): 6.5 N/A N/A N/A 8.9 0.0 0.0
TX Power(dBm): 10.5 N/A N/A N/A 4.6 -128.0 -128.0
#

Another person, the other side of the village (they are not an immediate neighbour) has an attenuation of 36dB and is getting about 5Mb line speed. So my D1 attenuation of 32dB is in the same kind of ball park to theirs, they claim their line is stable at 5Mb.

So thoughts on these stats please?

The estimated download speeds for me even on an impacted line were 5.1 to 2 Mb.

And how to progress with BTO to make improvements? There are few or more likely zero spare pairs in the D-side cable.

In reply to a post by godsell4:

So after a little negotiation with BTO and PlusNet, I am not connected to FTTC.

YES your are. Why do you think you are not connected to FTTC?


In answer to the attenuation question and speeds. Whilst 32 and 36 dB are not far apart in terms of line loss that is only half the story - you have to take into consideration the SNR (margin) too. If your line is picking up significantly more electronic noise on the route it takes - from other houses, factories, traffic lights, crosstalk from other users &c then then there will be less usable signal for the modem to work with, hence the lower speeds. Given their routing is probably way different to yours then it is entirely possible.

Edited by MHC (Wed 03-Jun-15 10:54:28)

In reply to a post by MHC:

Why do you think you are not connected to FTTC?

Most likely typo. The OP meant "now".

Yes I am now connected to FTTC, there was a typo in my original post.

It seems that VDSL2 aims for a target SNR value of 6dB on both the upstream and downstream connections when they go through the line training.

Despite this, my actual SNR appear to be between 9dB and 14dB whether it connects at 1Mb or 3Mb.

The routing of the other line is for sure 'different' but their line goes entirely over poles and is for sure in good condition, parts of my line are stuck in the ground and have been cut through and repaired a number of times. Also just this week BTO were working on a house near me and of course they claim the work they did had no affect on my line, I can be sure that the plost from dslstats says something very different.

So the achieved speed is less than the Impacted Range B values. Has anybody found that motivates BTO to do something?

A "perfect" type that completely reverses the meaning.

I am wondering if the SNR figures are above the 6dB margin because of the way they are calculated? A screen-shot of the bin plot using DSL Stats could be useful.

Make sure you get some screenshots of the BT DSL Checker showing the impacted figures - your actual figures will be fed back into te checker to help improve the accuracy so it is imperative to get some NOW.

When you have those you should be able to get PlusNet to persuade BT OR to investigate.

bitloading image http://postimg.org/image/8nc2vjo93/

SNRperTone1 http://postimg.org/image/6rlklnkyt/ which shows a periodic notch in the SNR plot

SNRperTone2 http://postimg.org/image/5m4n0o931/ which shows what the SNR plot looks like most of the time

Well as of this evening, I do not feel PN has really been fighting my corner here.

In fact at 16:11 PN updated my issue they have talked with BTO again and have "agreed with BTO that the line is too long to work", and they would arrange to move me back to ADSL, 10 minutes later my FTTC connection was disconnected, by BTO or PN I am not sure, but I have been left tonight without any kind of DSL ... great while I am working from home! I will be connected to ADSL again sometime tomorrow.

The most part of their message at 16:11 reads:

Thank you for your message. I called the suppliers again to ask for some further advice about how to best progress the situation and I have been advised that a team leader has been out to review the work and agrees that the line is too long to provide an effective fibre service.

They recommended that order be closed off so that we can provide ADSL services, because if the fibre is left connected it will constantly fault due to no sync and you would be left in a position of paying for a service that we cannot provide. The order will therefore be closed off in the next 48 hours so that we can regrade the service to ADSL.

I am sorry that I am not able to give a different answer, I have followed up as best I can with the suppliers to try and resolve this but the answer I am being given is that the line speeds will not improve and these are too slow to effectively sync the fibre service.

So the line stayed connected at about 2Mb all last night, the SNR plot looked pretty stable, much less noise on it than the ADSL the previous couple of nights.

The BTO speed estimator was this http://postimg.org/image/8gz3lykb3/ I am about 120-150m from the DP. At the DP, the JDSU managed a stable 8Mb.

If we assume BTO create the table based on knowledge of the line lengths and they have knowledge of what are acceptable performance for those lines, then we can say this line is of poorer quality than even BTO expect.

I can not fault the efforts of the two BTO engineers who did all they could while they were here.

We are now in the position where BDUK money has been used to build 2 new cabinets, at a cost of £15K each maybe, but due to poor line quality it is not possible to get connected according to BTO. Is this a reason why FTTC take up has been so low in some rural locations? And so making it harder for those claw back clauses to kick in?

Edited by godsell4 (Wed 03-Jun-15 22:41:43)

How often do you see that notch? That could be a local noise source.


As for BitLoading - there is certainly something odd from tones 120 to 310 where there is 10dB SNR which would normally allow 5 or 6 bits per tone. As to why there is nothing ... no idea or suggestion. The ISP needs to see and understand teh graphs - how you achivre that - it could be a long struggle,

And if Openreach have declared the line not fit for FTTC the chances of success probably zero.

Waiting to get an update from PN this morning to see if that is what has happened.