Hello Tristan
I don't know how BT where able to go ahead with fibre installation with a revised estimate of 5Mbps, How far are you from the Large Green cabinet (Fibre) ?
Until recently, the protocols were that if once installed, the engineer had to ring the Fibre SMC if it ended up as a sub 15Meg product. Now, the proviso is that if the finished article is less than half the predicted speed. At 1.4Meg, the OP obviously has a shout.
- We are now getting ~1.4 mbps on a good day, 0.7 mbps on a bad...
Hello Tristan,
Welcome to kitz.co.uk!- We are now getting ~1.4 mbps on a good day, 0.7 mbps on a bad...
What speeds were you getting on ADSL? At a guess, the poor performance may be due to a faulty line rather than the extended distance. Notice the heavy noise even on the lowest subcarriers.
Can you beg, borrow or steal a Mole, Hawk or similar to run some TDR tests? They would reveal the loop length and could reveal a high resistance fault causing that high attenuation and noise.
cheers, a
When it was windy or rainy (typical for our bit of Northern Ireland) the connection would drop, but we could live with that!
Alas, I doubt I'd be able to get any kit to do TDR tests. Your point about the attenuation and noise is what I'd like to be able to take to BT to state my case about getting something done.
I am getting called back tomorrow by someone who has raised a fault with BT wholesale, and I'd like to be able to direct the discussion somewhat. He has stated that our connection measurements were the worst he has seen...
We were getting a whopping 512 down and 256 up. But at least it was pretty constant. When it was windy or rainy (typical for our bit of Northern Ireland) the connection would drop, but we could live with that!
If it is going to be a protracted case, it's maybe worth getting a Mole (as little as £40 from ebay). Useful to point the engineer towards the likely location of the fault, if there is one. You still only got 512Mbps with ADSL (1?). How far is the exchange?
Based on your estimated loop length, maybe plot a graph of attenuation vs frequency, using the BT cable reference model. With ideal parameters, i.e. a loop formed from one continuous, homogenous pair of 0.5mm copper, the graph should illustrate the magnitude of the attenuation you might expect.QuoteI doubt I am alone in this - we are not the only people in my area (countless farms etc) who are probably less technically adept and resorting to satellite connections.
Kudos to the late Sir Arthur C. Clarke..
Arthur C Clarke, king of sci-fi and 'inventor' of the 'geostationary satellite' :D
Would it be possible for you to post a copy/copies of your xdslcmd log(s) for us to have a closer look? Windows or Linux format would be O.K.
The Windows version of the scripts also uses "xdslcmd info --stats" for data.
It would be good to include that too.
All the relevant data results in a Windows log file of around 330KB in size (too large to upload to this forum).
However, zipped, the filesize is around 61KB, so can be uploaded here.
Actually - was able to get in and generate the attached file. Is this any use? I can change my script to get any other figures.
And a 2nd set after doing a remote reboot (using equipcmd 33) as the download speed is truly terrible... 281 kbps. Unbelievable.
I am getting called back tomorrow by someone who has raised a fault with BT wholesale, and I'd like to be able to direct the discussion somewhat. He has stated that our connection measurements were the worst he has seen...
The BT Care forum didn't seem too helpful:-
"we cannot advise on problems of this nature as the openreach modem is a locked device and it is against forum rules to advise on hacked devices
In terms of RF pollution, it looks like BBC Radio 4 has the slight lead over RTE Radio 1.
It's time that BBC Radio 4 (AM) was told to pipe down with its pips. My sympathies - we suffer constant online harassment from Edwina Currie (BBC Radio 5 on 693kHz).
On a serious point, it's difficult to see what you could do. Are you on very elevated ground? Does BT ever shield pole-strung cable to solve RF ingress?
However, BT Wholesale (or whoever it is that comes out) . . .
# xdslcmd info --pbParams
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 2
Max: Upstream rate = 1160 Kbps, Downstream rate = 2368 Kbps
Path: 0, Upstream rate = 1160 Kbps, Downstream rate = 410 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: 1160 kbps 2368 kbps
Actual Aggregate Tx Power: 10.4 dBm 1.5 dBm
============================================================================
VDSL Band Status U0 U1 U2 U3 D1 D2 D3
Line Attenuation(dB): 20.5 84.0 N/A N/A 35.5 0.1 0.1
Signal Attenuation(dB): 18.9 N/A N/A N/A 35.5 0.1 0.1
SNR Margin(dB): 6.2 N/A N/A N/A 19.5 0.0 0.0
TX Power(dBm): 10.5 N/A N/A N/A 1.5 -128.0 -128.0
# xdslcmd info --stats
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 2
Max: Upstream rate = 1164 Kbps, Downstream rate = 2384 Kbps
Path: 0, Upstream rate = 1160 Kbps, Downstream rate = 410 Kbps
Link Power State: L0
Mode: VDSL2 Annex B
VDSL2 Profile: Profile 17a
TPS-TC: PTM Mode
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 19.6 6.3
Attn(dB): 0.0 0.0
Pwr(dBm): 1.5 10.4
VDSL2 framing
Path 0
B: 57 31
M: 1 1
T: 4 51
R: 16 0
S: 4.4755 0.8620
L: 143 297
D: 7 1
I: 80 32
N: 80 32
Counters
Path 0
OHF: 1257032 15452
OHFErr: 0 0
RS: 15087415 1324715
RSCorr: 5889 0
RSUnCorr: 0 0
Path 0
HEC: 0 0
OCD: 0 0
LCD: 0 0
Total Cells: 13076794 0
Data Cells: 338654 0
Drop Cells: 0
Bit Errors: 0 0
ES: 32922 4787
SES: 423 0
UAS: 10283 10283
AS: 16949
Path 0
INP: 3.00 0.00
PER: 13.42 10.98
delay: 7.00 0.00
OR: 46.47 23.29
Bitswap: 16 3
$ R
library(MassSpecWavelet)
# Loading required package: waveslim
qlnDAT <- read.table("qln.txt", colClasses = c(rep("NULL",1), rep("numeric",1)), header=TRUE)
qlnMAT <- data.matrix(qlnDAT)
wCoefs <- cwt(qlnMAT, scales=seq(1,31,1), wavelet='mexh')
localMax <- getLocalMaximumCWT(wCoefs)
ridgeList <- getRidge(localMax)
majorPeakInfo <- identifyMajorPeaks(qlnMAT, nearbyPeak=TRUE, ridgeList, wCoefs, SNR.Th=1)
peakIndex <- majorPeakInfo$peakIndex
#
peakIndex
127 167 188 211 238 253 282 311 451 562 763
777 858 1216 1324 1391 1405 1430 1506 1604 1687 1704
1736 1791 1885 1962 2799 2819 2913 2970 3006 3099 3192
3286 3324 3380 3433 3472 3537 3567 3763 3959
plotPeak(qlnMAT, peakIndex, main=paste("identified QLN peaks"))
As far back as I can remember, we have always been known professionally as 'Technicians'.
I have been looking through your latest stats & a few of them look "strange" when compared against any other VDSL2 stats that I have looked at over almost a year now.
Tristan quoted ...................
"I get the impression the people called out are 'installers' rather than engineers".
As a qualified Electrical Engineer, I can understand your comments fully. But for pedants sake, the term 'Engineer' has been banded about for eon's when referring to 'us' Openreach guys. God only knows who or how it became so, but I can tell you that it wasn't from BT. As far back as I can remember, we have always been known professionally as 'Technicians'.
Only when I was on the 'Power & BES' group was I referred to as a 'Power engineer'. On this side of the fence, dependant on skill set, we are called Technician 2B (T2B), Technician 2A (T2A), and the following are grades that are still tagged to individuals, but are now obsolete and will be lost as and when the individuals retire. They are Technician 1 (T1), Senior Technician (ST) and Technical Officer (TO).
As you will see, nowhere in our descrip do we refer to ourselves as 'engineers'. So the term is protected as far as BT are concerned. ;) :)
The RF interference from AM broadcast radio looks dramatic, but when quantified by the number of tones affected by the ingress, it probably doesn't impact the overall DSL performance that badly.
Channel bandwidth in Europe for AM broadcast radio is only 9kHz, meaning that ingress from an AM radio station should only impact two or three DSL subcarriers.
Using a re-purposed wavelet-based peak-det algorithm:
The tones notably affected by AM broadcast ingress (and other RFI) are the following. From a total of some 4000 tones, it's not that many, really. The line attenuation is the real service killer...
Suggesting that the real problem, as Paul has already said, is the high attenuation on the line. A consequence, as you mentioned before, of suffering a loop of considerable length. An unfortunate property of the twisted pair. As such, even if every joint was re-made between your home and the cabinet, it still might not result in an improvement.
What can be done? It's optimistic to hope that any more tweaking by Openreach is going to improve the performance - short of running fibre to your doorstep. As such, I would be tempted to ditch DSL and look for another solution.
What about establishing a private point-to-point microwave link from your community to the nearest town? It sounds very expensive or complicated but it's neither. Just a few hundred pounds and an afternoon's work can result in a surprisingly good job.
There is a specialist firm, Stella Doradus, in Waterford, [2] who sell all the kit needed. Helpful people too :) With a pair of high gain (22dBi) parabolic dishes and good quality transceivers, it is possible to form a decent microwave link of some miles. With the right antennas, a point-to-point wi-fi bridge of 25 miles even using domestic 802.11 kit, isn't unheard of ;)
It would indeed be interesting to know how much of the typical MW radio ingress into the line is due to the general line length E sides & D sides (underground) and how much is due to the last 50 yards of unshielded overhead drop wire.
Incidentally the specification for lay of the twists in std BT black sheathed drop wire is one twist every 89mm in the case of the orange/white pair and every 95mm in the case of the green/black pair.
It would indeed be interesting to know how much of the typical MW radio ingress into the line is due to the general line length E sides & D sides (underground) and how much is due to the last 50 yards of unshielded overhead drop wire.
Incidentally the specification for lay of the twists in std BT black sheathed drop wire is one twist every 89mm in the case of the orange/white pair and every 95mm in the case of the green/black pair.
So for the shortest possible path from cabinet -> home you would want green/black used? Although the difference would be small it could be significant in my case!
Tristan quoted ...................
"I get the impression the people called out are 'installers' rather than engineers".
As a qualified Electrical Engineer, I can understand your comments fully. But for pedants sake, the term 'Engineer' has been banded about for eon's when referring to 'us' Openreach guys. God only knows who or how it became so, but I can tell you that it wasn't from BT. As far back as I can remember, we have always been known professionally as 'Technicians'.
Only when I was on the 'Power & BES' group was I referred to as a 'Power engineer'. On this side of the fence, dependant on skill set, we are called Technician 2B (T2B), Technician 2A (T2A), and the following are grades that are still tagged to individuals, but are now obsolete and will be lost as and when the individuals retire. They are Technician 1 (T1), Senior Technician (ST) and Technical Officer (TO).
As you will see, nowhere in our descrip do we refer to ourselves as 'engineers'. So the term is protected as far as BT are concerned. ;) :)
That's interesting. Thanks for the input. Who would be the best person to get this escalated to? A TO? I'm not sure who has been coming out but as they are on their own they can't check any individual stretch of line for us (they need 3 people I think to operate the cherry picker?) - each says it needs escalated so I guess we are gradually working our way up the ranks!
Bear in mind this is BT we are talking about Tristan. It certainly does not follow that the higher the grading, the greater their level of knowledge. Maybe in other industries, but we seem to apply a 'Bottom-about-face' policy. This is a massive subject though, and not really for this thread. So in a nutshell, the chap/chapess you need is a 'Multi-skilled CSE with Broadband and Fibre skills'. These are actually T2A's (like myself), and although they are amongst the lower paid technicians, they actually know far more than the other obsolete ranks. Pole-testers are T1 ranks, but don't know their left from their right ;).
Unfortunately, it wouldn't make any noticeable difference to place you on the 'Green/Black', as it would only apply to the span from your house to the telegraph pole. The 'Green/Black' doesn't go all the way back to the PCP I'm afraid. :)
Sorry Tristan but at the very start of your thread I was amazed that OR/BT put you on Fibre with your very low line throughput at the start.
BT/OR should not have moved you to Fibre unless the your line was capable of 15megs +If this was my line with FTTC I would end the contract with BT give OFcom a call or email
http://www.ofcom.org.uk/
Sorry Tristan but at the very start of your thread I was amazed that OR/BT put you on Fibre with your very low line throughput at the start.
BT/OR should not have moved you to Fibre unless the your line was capable of 15megs +If this was my line with FTTC I would end the contract with BT give OFcom a call or email
http://www.ofcom.org.uk/
Incorrect. 'Sub 15 Meg' circuits have always been around, but once upon a time we had to ring every man and his dog to make sure everyone was happy for the circuit to remain on FTTC. The chap who had only ever got 0.5Meg was always more than happy to be getting (for example) 5Meg, and as such I have never reinstated a 'sub 15 Meg' product back to ADSL.
Plus, we don't need to ring anybody these days. If the EU is happy with 'Sub 15', then job done.
Newtron .......... I was merely pointing out that your comment about 'Sub 15 Meg' was incorrect. There are thousands of this kind of connection out there.
If I was going to buy a PC from you, I would expect definitives about it's operating specification. This is because every component within that PC will be a 'known value'.
When ordering Broadband (ADSL or VDSL) there are so many 'unknowns', that only an estimate can be given. Granted, the early estimate the OP was given of 20Meg was amazingly wrong, but an estimate nontheless.
If there is no possible further enhancement on this OP's circuit, then I'm absolutely certain the OP would get his money back, especially if he presents proof of the '20Meg estimate'.
...
As you can see the SNMR increases abruptly over 5 mins, just as the DS TxPwr drops along with the ATTDR. Would anyone care to hazard a guess why this would happen? Other than it being a long line of course...
Also, is there anything else I could plot to shed any light?..
Well thats it somehow tristan was given an estimate of 20.4megs for FTTC he may have used the BT web site http://www.dslchecker.bt.com/adsl/adslchecker.welcome which gave him a 20.4mbps false estimate, but by the time you have signed up for FTTC with BT and then an engineer comes round to install the HG612 to find your only going to get 5Mbps it's to late your stuck in a 18 month contract :'(
...
As you can see the SNMR increases abruptly over 5 mins, just as the DS TxPwr drops along with the ATTDR. Would anyone care to hazard a guess why this would happen? Other than it being a long line of course...
Downstream Transmitter Power is determined and controlled by the DSLAM. Why is it doing that? To mitigate DSL crosstalk onto other pairs, perhaps? If the DSLAM transceiver's output power is being cut back - i.e., that's not a reporting error - I can't think of any other reason.
Also, is there anything else I could plot to shed any light?..Maybe some physical tests with TDR equipment to discover whether there are any major points of impedance mismatch between your home and the cabinet. Those would cause reflection losses in the signal. The abutment of aluminium and copper conductors in your line, if that's what you've got, doesn't sound very promising.
Did you previously have better bandwidth with ADSL?
As you can see the SNMR increases abruptly over 5 mins, just as the DS TxPwr drops along with the ATTDR. Would anyone care to hazard a guess why this would happen? Other than it being a long line of course...Downstream Transmitter Power is determined and controlled by the DSLAM. Why is it doing that? To mitigate DSL crosstalk onto other pairs, perhaps? If the DSLAM transceiver's output power is being cut back - i.e., that's not a reporting error - I can't think of any other reason.
Would OR conduct such a test as a matter of course? ie, I assume they have a SOP/checklist they go through, and would this be on it? Anyhow, I've asked to have it done!
We got a solid 512 kbps down and 256 up. I never bothered to pay for a higher speed as there was no guarantee of getting it! But again, when it rained or was overly windy this would drop off too - but it work afterwards.
We are preparing a nice letter to OFCOM in NI detailing all this. There seems to be less pressure on BT to upgrade/maintain their infrastructure in rural areas to actually support infinity. They have received public money to install the cabinets, and it mustn't be economic to make them of any use (we aren't the only people in our area to have this issue, one of the OR folk confided...). And then public money is also being spent to try and get coverage by other means: http://www.nwewn.com (awful website, but seemingly our only hope without finding a friendly person who'll allow us to stick a microwave transmitter on their property).
As you can see the SNMR increases abruptly over 5 mins, just as the DS TxPwr drops along with the ATTDR. Would anyone care to hazard a guess why this would happen? Other than it being a long line of course...Downstream Transmitter Power is determined and controlled by the DSLAM. Why is it doing that? To mitigate DSL crosstalk onto other pairs, perhaps? If the DSLAM transceiver's output power is being cut back - i.e., that's not a reporting error - I can't think of any other reason.
Ahh, apparently, according to my mother, an engineer some engineers ago reduced the power on the line to make it more stable. The analogy he used was that of a leaky hosepipe. If you turn on the water pressure too high a lot of water will escape through the gaps. If you turn the pressure down you lose less along the way.
Is crosstalk a strong function of length? Or would, say, a really old bit of line that might have some damage along the way have higher crosstalk to a newer bit of line?
Great work, Tristan.
It looks like you've uncovered a clear (and close) correlation between SNR and temperature. The rises and falls of SNR closely relate to outside temperature. The transmission behaviour of the cable itself can't be responding so dramatically to temperature changes. So that points towards poor splicing at one or more joints along your loop.
And since, in terms of the speed at which those SNR changes occur, that probably eliminates water ingress as the fault. Ingressed water in the cable would take many hours or even days of warm temperature to dry out, with much more damped improvements in SNR than you have recorded.
A series of TDR taken at strategic points in time could locate the site of the errant joint(s). Is Openreach able to expend the manpower these days to do that? Maybe not.