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Author Topic: Rural BT Infinity issue - help interpreting stats  (Read 27189 times)

tristan

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Rural BT Infinity issue - help interpreting stats
« on: July 15, 2012, 12:51:11 PM »

Hello all,

I'm looking for some help interpreting my line stats from xdslcmd for BT Infinity. The issue:

- Our house is in the middle of nowhere exchange-speaking so I am well aware we will never get the full speed (I had hoped to get >2 mbps download, however!)
- We were initially given an estimate of 'up to 20.4 mbps' which was revised to 5 mbps when the install was completed.
- We are now getting ~1.4 mbps on a good day, 0.7 mbps on a bad...

Attached are some graphs from xdslcmd over a few days.

Is my line just too bad?
Is there anything I can do?
Who would be best to contact at BT about this and how?
Will BT re-lay lines if it can be shown the connection is so bad?

I've posted to the BT forums (http://community.bt.com/t5/BT-Infinity/Rural-speed-issue-help-interpreting-xdslcmd-stats/m-p/573567/highlight/false#M54226), contacted the moderators and tweeted to try and get it looked into.

All help gratefully received.

Tristan
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NewtronStar

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Re: Rural BT Infinity issue - help interpreting stats
« Reply #1 on: July 15, 2012, 03:30:26 PM »

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) ?

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tristan

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Re: Rural BT Infinity issue - help interpreting stats
« Reply #2 on: July 15, 2012, 03:48:24 PM »

Hey - I'm just looking into that now. I was led to believe that we were at the top end of the range for ADSL (5 km?) so presumably the distance to the cabinet should be less. Trying to work out how to get the exact location of cabinet. Any tips?
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NewtronStar

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Re: Rural BT Infinity issue - help interpreting stats
« Reply #3 on: July 15, 2012, 03:57:00 PM »

If you know where the exchange is usually the line from the exchange runs under the roads to the Cabinet then again along the road to your telegraph pole.

there is a postcode cab checker out there but it does not show you the true location.

the problem is fibre is worse over long distances adsl is better over long distances
« Last Edit: July 15, 2012, 04:55:08 PM by NewtronStar »
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NewtronStar

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Re: Rural BT Infinity issue - help interpreting stats
« Reply #4 on: July 15, 2012, 04:12:41 PM »

If it helps Tristan you can compare my stats with yours and I am 0.53 miles (852 meters) from cabinet.


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Black Sheep

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Re: Rural BT Infinity issue - help interpreting stats
« Reply #5 on: July 15, 2012, 06:46:59 PM »

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.
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tristan

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Re: Rural BT Infinity issue - help interpreting stats
« Reply #6 on: July 15, 2012, 07:02:57 PM »

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.

Thanks for this. Are you suggesting that BT Wholesale / SMC might help to get a solution? I am quite nervous as, some years ago, I was under the impression that if the connection supplied wasn't over a particular level, BT would simply switch it off. Meaning no internet access for us!

On the ThinkBroadband forum I'm getting some help finding the cabinet and getting a rough distance.

http://forums.thinkbroadband.com/fibre/f/4140623-rural-fttc-issue-help-interpret-xdslcmd-stats.html#Post4140704
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asbokid

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Re: Rural BT Infinity issue - help interpreting stats
« Reply #7 on: July 15, 2012, 07:47:58 PM »

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
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tristan

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Re: Rural BT Infinity issue - help interpreting stats
« Reply #8 on: July 15, 2012, 08:20:43 PM »

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

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!

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...

I 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.
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asbokid

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Re: Rural BT Infinity issue - help interpreting stats
« Reply #9 on: July 15, 2012, 09:11:49 PM »

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.

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, homogeneous pair of 0.5mm copper, the graph should illustrate the magnitude of the attenuation you might expect.

Quote
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...

Don't worry. The dentist said the same about Our Wayne's teeth, but he soon had them whipped out  :-X

Not so sure that BT will be willing to remove your rotten cabling. Is there any evidence of a fault in the voiceband?  Crackling, hissing, etc?

Quote
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!

That is evidence of a fault.   In a rural area, much of your line is pole-strung?  With well-made joints, there still shouldn't be any disconnections, though.

cheers, a
« Last Edit: July 15, 2012, 09:31:43 PM by asbokid »
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tristan

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Re: Rural BT Infinity issue - help interpreting stats
« Reply #10 on: July 15, 2012, 09:33:22 PM »

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?

Thanks, I'll look one up. Yep, only 512... I believe we are just over 4 miles by road from the exchange. However, we are much closer to different exchange - I remember asking about being moved... It focussed the mind on what to download! Whilst I was doing my PhD I'd try to work from home over holidays etc. That's when all the time spent doing things from the command line paid off! I couldn't get enough bandwidth for a decent X forward or VNC.

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.

Quote
I 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

How right you are, sir. I'm loathe to give any of the satellite broadband companies my money, however, until they are more reasonably priced!

I hadn't realised you had developed the hacked firmware for the HG612 - excellent work! I'll read up on the BT reference model and get something coded up.

Thanks for your help.
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Bald_Eagle1

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Re: Rural BT Infinity issue - help interpreting stats
« Reply #11 on: July 15, 2012, 11:38:08 PM »

Looking at your pbParams stats, it is clear that your connection can only use some of the lowest frequency downstream band D1.

Signal & Line Attenuation is 35dB or so for that band in which a little less than 500 bit-loading tones are useable.

These lower tones are at ADSL2+ frequencies & with attenuation of 35dB, the Kitz ADSL calculator suggests a line length of 2.5km & a sync speed of 11712 kbps.

Even the typical attenuation of 13.81 dB per km, used for 0.5mm copper in calculations etc. suggests 2.5km or so line length (from the cabinet for FTTC).

I have attached the graphs from a 1600m or so connection for comparison purposes.
Again, only the lowest frequency D1 band is useable.
However, sync speed is much higher than on your connection.

I notice your DS TX Power seems quite low which no doubt has some effect on sync speed.
Mine is usually around 12dBmV to 13 dBmV over around 1000m & the graphed example reports 11.1dBmV.

If your cabinet is a long way from the exchange, nearby ADSL signals will already have weakened due to the copper distance from the exchange.
So to avoid your own FTTC connection drowning them with crosstalk, it could be that your power levels have been reduced accordingly, thus lowering your own sync speed.

There may also be other factors to consider such as very high error counts, high Interleaving depth etc.

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.

I have to admit that I have no realistic idea what FTTC sync speeds you should expect for your line length (assumed 2.5km).
However, I would have thought it could/should be a little better than you report.

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tristan

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Re: Rural BT Infinity issue - help interpreting stats
« Reply #12 on: July 16, 2012, 09:19:20 PM »

Cheers Bald_Eagle1, I'll get those extra logs posted tomorrow. I'm working remotely so I need to make sure someone leaves a computer on so I can ssh in to it!

This is all very interesting - I have a lot of reading to do!

Tristan
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tristan

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Re: Rural BT Infinity issue - help interpreting stats
« Reply #13 on: July 16, 2012, 10:25:14 PM »

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.

Thanks,

Tristan
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tristan

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Re: Rural BT Infinity issue - help interpreting stats
« Reply #14 on: July 16, 2012, 10:47:56 PM »

And a 2nd set after doing a remote reboot (using equipcmd 33) as the download speed is truly terrible... 281 kbps. Unbelievable.
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