Hi VSDL_NoSync,
Infinity is a VDSL2 connection. It’s not just the length of line that can affect Infinity but also the quality. It could be that the line is part aluminium which has a higher resistance than copper and therefore isn’t as good as carrying a DSL signal. All the cabling is also overhead which can cause interference issues.
That statement regarding aluminium may raise a few eyebrows.
There has been a recent discussion regarding aluminium here:-
http://forum.kitz.co.uk/index.php/topic,10876.0.html
Your line is extremely long anyway and the celerity line loss is 78.9dB. We normally say it’s not possible to provide broadband at anything over 70dB, most other providers will say 65dB.
They checked the line and found it to be 8km long from the exchange, from the cabinet it’s 6.5km so it’s only a 1.5km reduction using Infinity.
Circuit line length estimate: 6907
Circuit line length calculated: 8110
Distribution Point Line length estimate: 6515
I have not previously seen the term “celerity line loss”.
On searching, I found this page via Google:-
http://www.scotland.gov.uk/Publications/2006/12/20130045/3Although ADSL related, it appears to clearly explain relevant matters in layman terms.
As VDSL2 uses very similar technology (apart from the fibre to the cabinet part), the information is still very relevant for FTTC connections.
The "previous" & "next" buttons also provide some useful information.
They have said that VDSL connections will work on long lines at a reduced speed in the same way an ADSL connection do, but your line is just far too long to give any form of adequate service. If we could connect it chances are it would be extremely slow and would probably disconnect frequently.
From monitoring a few VDSL2 (FTTC) connections, it appears that no useable data bits are loaded once attenuation reaches around 72dB.
My "problematic" connection loads data bits from the lowest frequency, right up to the frequency where attenuation exceeds 72dB & then stops loading.
My overall attenuation (as reported by engineers' JDSU meters is apparently around 22dB.
It was 30dB at one point, when my connection was only able to sync at around 20Mb & less.
Following a lot of engineer visits, my downstream sync speed now varies between 30Mb & (on a good day) up to 35Mb.
My own connection is anywhere between 800m & 1100m from the cabinet.
Apparently I am around 5300m from the exchange, hence I only ever saw a 1Mb ADSL connection.
I have seen 16Mb sync speed connections on distance from the cabinet of 1600m & also 40Mb sync speed on distances that are supposedly 1200m.
AS your overall attenuation is already reported as almost 79dB, it would currently appear to be a physical impossibility to achieve a VDSL2/FTTC connection at all.
Now, the question has to be:-Are the lengths quoted by BT accurate, or have they only been calculated by looking at attenuation/SNR values, thus giving a false impression of the lines' lengths?
When my connection's overall attenuation was around 30dB, an engineer's JDSU reported it as being 1100m from the cabinet.
Following engineering works that reduced my connection's attenuation value to around 22dB, my connection's length has been reported as 900m & 1000m.
I believe my connection is in reality closer to 800m, so I still believe attenuation is higher now than it was when FTTC was first installed & I was able to
maintain higher speed connections around a 35Mb sync speed.
If you really are only 2.5km from the relevant cabinet some level of VDSL2 connection "should" be possible (low speed, but possibly stable & higher speed than the 1Mb you are achieving via ADSL.
The stats quoted so far would indicate (to me) a physical HIGH RESISTANCE "fault" somewhere in your D-side connection, that (depending upon cost to BT) may, or may not be repairable.
Something like a TDR test conducted by an engineer should confirm matters one way or the other (unless one has already been conducted that does indeed confirm excessive line lengths).
HTH,
Paul.
EDIT:
In order, I have attached bit-loading graphs for a low speed FTTC connection & my FTTC connection, along with their respective attenuation over frequency graphs.[attachment deleted by admin]