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Author Topic: FTTC - Distance from the Cabinet - Realistic speed estimate  (Read 254030 times)

Greybeard33

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #600 on: June 08, 2012, 10:40:04 PM »

Paul,

Having now found time to set up your excellent scripts, I have attached one(!) day's stats harvested from my modem for comparison. My line is probably longer than yours (I am about 1000m by road from the cabinet), yet consistently manages max attainable rates above 40Mb. I do recall that, a few months before the original rollout of ADSL broadband, BT carried out a major refurbishment of the infrastructure in our area, replacing all of the dropwires, many of the wooden poles and at least some of the underground cables. I suspect that, as a result, I may have an all-copper circuit. My attenuation figures appear to be significantly better than yours, even after all the remedial work on your line.

Interestingly, the re-sync at 23:34 on the 6th was triggered by me manually saving the modem log file from the web interface (the last entry in the saved file is “2012-6-7 23:34:21 Notice 104500 DSL deactivate” and the file is timestamped 07/06/2012 23:34). Looking back, I realised that a re-sync the previous day had also occurred during an interactive login, although I had not noticed it at the time. My impression is that the modem processor is running near its max capacity, so extra tasks can cause a glitch.

It can be seen that the re-sync caused an increase in the downstream sync speed even though the downstream SNRM also increased back up to the target. Presumably this was because the Quiet Line Noise was slightly less than during the previous re-sync. However, the interleaving depth increased slightly – possibly due to DLM reacting to the re-sync?

GB33
                   
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Bald_Eagle1

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #601 on: June 08, 2012, 11:40:22 PM »

Hi GB33,

That really is interesting.
Thank you for sharing that information with us.

I have fairly recently measured my line with a surveyor's trundle wheel & allowing a few metres here & there for slack coils in joint chambers, up one pole & round the back of my house, I now believe my line to be a little short of 1000m.
It could perhaps be as short as 900m, depending on exactly where it crosses the main road to get to the cabinet.

I am hopeful that the exact route, materials used, cable diameters etc, will be confirmed in the not too distant future, so any remaining ifs & maybes can be put to bed once & for all.

How confident are you about 1000m being the realistic length of your own connection?

I was unable to see my stats when FTTC was installed 24th June 2011, but as you will be aware, I achieved really good speeds & stability for the first month.

My issues started immediately on my telephone & broadband services being reinstated following a sudden loss of service for 4 days at the end of July.

Since then all sorts of works have been carried out, including rerouting & providing a brand new drop wire, directly to my master socket, rather than being via an extension cable from the point of entry at the front of the house.

I can't imagine that any extra length has been introduced to my D-side cable, so the lower speed issue MUST be due to higher resistance in the cable or joints than was initially present.

In theory, as in your case (if memory serves me right from one of your other posts), speeds should have increased when switched to the 17a profile last October.
There was no immediate improvement at all.

I wish there were plans for a major refurbishment of the infrastructure in my area.
They could even site a cabinet or two in my garden at no charge, not even a peppercorn rent.

That was an interesting note regarding the saving of the modem's log file causing resyncs.

I don't usually bother to save it as my own logs contain plenty of detail, but I have thought of doing so to use as an easy reference of all known resync events.

I have saved it a couple of times (a long time ago), but can't recall if it is saved in some default location or we are offered the chance to browse to a location.
Could you confirm? I don't want to cause a resync at the moment.

I will soon be releasing updated scripts that will add more data to the ongoing log file without overwriting it.
I am just trying to finalise some error checking to combat what I believe is some sort of an occasional clash with AVG, during its daily virus scanning process.

Some days (not every day), a few minutes worth of data are missing from the ongoing modem_stats.log.
I have rescheduled the timing of the virus scans & the timing of the missing data moves with the new AVG schedule.
It's not that important really & it doesn't cause any other issues, so if I can't find a solution I'll either just accept it, or change to a different virus scanner, possibly giving Avast another try.

I see you are also on the recently adjusted band plan (now up to DS tone 3959 from 3939).
Do you have any before & after stats records from that adjustment?

Mine changed during the early hours of 24th May & I can see quite a large increase in US line attenuation from that time, along with a more gradual increase in attenuation since I started logging every minute back in late November (as can be seen in my 190 day stats).

It is at the higher frequency tones that neither of us can use due to attenuation over distance from the cabinet, but it does appear to have reduced my attainable DS & US rates a little.

It could be interesting for us to compare our stats occasionally, especially as we have such similar line lengths.

Cheers,

Paul.

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Greybeard33

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #602 on: June 09, 2012, 09:47:52 AM »

Paul,

Thank you for your interest. Taking your questions in order:

1. 1000m (actually more like 995+/-10) is a rough estimate, made using Google Maps Pedometer, of the distance by road from my house to what I know is the correct cabinet (the OR installation engineer confirmed it) over what I believe is the correct route. It does include an estimate of the distance from the PCP to the FTTC cab (which is diagonally opposite on the other side of the wide road) but not any allowance for zigzags across the roads, coils in joint chambers etc., so is likely to be an underestimate. The route is not the only possible one, but is the shortest and most logical, considering the locations of the joint chambers and the other cabinets in the area. Before I ordered FTTC, I tried putting a string of addresses along this route into the BT Wholesale speed estimator, and the speeds progressively increased from my house up to the maximum near the cab - this was not the case for the other possible routes.

2. The modem web i/f has "Save" and "Save As" options for the log file - I chose Save As, then browsed to a suitable folder on the PC hard drive. When I clicked Save in the dialog box, I was thrown back to the modem's login page and had to log in again, so clearly there was a major hiccup. I do not know what the Save option does, and am not keen to try it!

3. I use Microsoft Security Essentials not AVG, but am unable to account for the 35 minute gap in the stats I posted yesterday - there was no virus scan at the time. The Task Scheduler Task Status record shows Task Result - Success every minute until 12:25:00, then nothing until 12:59:13 Run Start, 12:59:13 Run End, Result - Stopped; then 12:59:13-12:59:16 Stopped, repeated once; then 12:59:13-12:59:17 Success, repeated 30 times; then 12:59:59-13:00:00 Success and continuing normally every minute thereafter. The modem_stats.log just skips from 12:25 to 12:59 (single entry only). The PC was idle but awake and the Windows Event Log shows no events at all during this period. Incidentally I had to tweak the Task Properties to get it to run automatically after a reboot  - Googling the error turned up the solution of changing, on the Settings tab, the setting for "If the task is already running, the following rule applies:" to "Stop the existing instance". Don't ask me why this works! (I'm running Vista SP2)

4. Unfortunately my earliest stats are from 1st June and the band plan had already changed to tone 3959 by then. Therefore I cannot say if the change had any significant effect, although in some recent speed tests my upstream rate has been a little better than I have ever seen previously.

I hope your persistence will eventually see you triumphantly posting stats better than mine!

Cheers,

GB33
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Bald_Eagle1

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #603 on: June 09, 2012, 10:16:45 AM »

Hi GB33,


2. The modem web i/f has "Save" and "Save As" options for the log file - I chose Save As, then browsed to a suitable folder on the PC hard drive. When I clicked Save in the dialog box, I was thrown back to the modem's login page and had to log in again, so clearly there was a major hiccup. I do not know what the Save option does, and am not keen to try it!

Mine (version 2B) just has a Save Log button - screenshot attached.
I'm not keen to keep experimenting at this stage either & it's not of tremendous importance anyway.
 
Quote
3. I use Microsoft Security Essentials not AVG, but am unable to account for the 35 minute gap in the stats I posted yesterday - there was no virus scan at the time. The Task Scheduler Task Status record shows Task Result - Success every minute until 12:25:00, then nothing until 12:59:13 Run Start, 12:59:13 Run End, Result - Stopped; then 12:59:13-12:59:16 Stopped, repeated once; then 12:59:13-12:59:17 Success, repeated 30 times; then 12:59:59-13:00:00 Success and continuing normally every minute thereafter. The modem_stats.log just skips from 12:25 to 12:59 (single entry only). The PC was idle but awake and the Windows Event Log shows no events at all during this period. Incidentally I had to tweak the Task Properties to get it to run automatically after a reboot  - Googling the error turned up the solution of changing, on the Settings tab, the setting for "If the task is already running, the following rule applies:" to "Stop the existing instance". Don't ask me why this works! (I'm running Vista SP2)

That's strange, but very handy to know.
It's not necessary on Windows 7 & XP.

Quote
4. Unfortunately my earliest stats are from 1st June and the band plan had already changed to tone 3959 by then. Therefore I cannot say if the change had any significant effect, although in some recent speed tests my upstream rate has been a little better than I have ever seen previously.

Not to worry. My DS & US do appear to have taken a slight hit since the change.
It may just be pure coincidence that US LIne attenuation shot up at the same time. It doesn't look too out of the ordinary on your connection.

Quote

I hope your persistence will eventually see you triumphantly posting stats better than mine!



I'm not holding my breath on that one.

I would love to know though whether my stats are currently as good as they could ever physically be, or if they did indeed deteriorate following the 4 day loss of service (i.e. "something" just needs repairing).

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Greybeard33

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #604 on: June 09, 2012, 01:00:48 PM »

Mine (version 2B) just has a Save Log button - screenshot attached.
Mine is the same - my memory let me down. The Save As dialog must have come up after I pressed the button.
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Bald_Eagle1

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #605 on: September 19, 2012, 07:13:59 AM »

Just for fun, I attach the graphs from the latest 60 days connection.

During that period most of the resyncs were caused by me either rebooting the modem for testing purposes, or having to turn all the power off while I do some home refurbishing work.

I believe I have now exceeded the record for my connection's up time. It has now gone over 10 days without a resync.

Sync speeds aren't fantastic due to distance from the cabinet of up to 1000m or maybe a little less, but the connection is stable.



« Last Edit: September 19, 2012, 07:19:35 AM by Bald_Eagle1 »
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Darren

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #606 on: September 20, 2012, 11:48:29 PM »

You got your connection sorted then BE  :) What was the cause?
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burakkucat

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #607 on: September 21, 2012, 01:54:21 AM »

Quote
What was the cause?

Argh! Darren, no!  :no:  Please don't get Baldy_Bird started . . . he might just use it as an excuse to fill another 40 pages whilst explaining it to you!  :help:  :paperbag:
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Bald_Eagle1

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #608 on: September 21, 2012, 06:26:05 AM »

You got your connection sorted then BE  :) What was the cause?


In the end, it came down to a faulty faceplate filter that was causing disconnections simply by using the phone & a dodgy joint between the underground cable & the pole top DP across the road from my house that caused random disconnections, increasing in frequency as the weather became warmer & dryer.

Some of the other engineer/technician visits where "work" was done caused slight improvements (usually simply by re-making poor cable joints & onceover replacing/rerouting the drop wire from the pole).

I believe the dodgy joint had been the main issue all along & the faceplate issue being more recent as a number of faceplates had been replaced previously, with no real improvement seen.

We had a power cut yesterday morning that resulted in a slight increase in DS & US sync & throughput speeds:-


From experimenting with different things over the problematic months, I/Plusnet discovered that my DS sync speed increases by around 5Mb - stabilising at approx 33.5Mb when US is capped at 2Mb, rather than what has now become Plusnet's default "up to" 10Mb.

This also appears to be the position for other sub-40Mb users on being switched to the 10Mb US service.

Users capped at 40Mb but with higher attainable rates still achieve 40Mb sync speed with the benefit of increased US sync speed.

Even before 10Mb US became the default Plusnet offering, I chose to have the increased US throughput speed at around 4Mb instead of 1.67Mb, at the expense of some DS throughput speed due to the nature of how I work from home fairly often.

My gripes over this matter are about how long it took to actually find & fix the faults & the constant "your connection is working perfectly satisfactorily & within our supplier's" guidelines" type of comments, despite me providing graphical & raw data evidence to the contrary.

Even reporting a number of times that engineers simply climbing the pole to work on other users' lines caused disconnections, thus highlighting a probable loose joint issue took over 3 months to be even looked at & that was only because I begged the visiting engineer to check it out. It hadn't been mentioned to him by BT (or Plusnet's notes).
In the end, that turned out to be the main culprit.

So, all in all, it was a very astute decision on BT's behalf to supply locked modems where probably the vast majority of users have absolutely no idea how poorly their connections may be performing at any time & thus fault reports are kept to a minimum & it is incredibly difficult to dispute BT's claims that their aged infrastructure is "fit for service".

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JoshShep

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #609 on: January 17, 2013, 11:24:18 AM »

Hi Guys,

Long time no speak! It's been a while since I've been on here.

Just thought I'd check how your all doing? And this directed at Paul, how has your connection been?

You finally happy with your results?

Cheers,

Josh.

Bald_Eagle1

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #610 on: January 17, 2013, 01:02:36 PM »


Just thought I'd check how your all doing? And this directed at Paul, how has your connection been?

You finally happy with your results?



Yep, the connection has been really stable, albeit that I chose to have a higher US profile at the expense of a little DS speed as I transfer many large files between home & the office when working from home.

It did take a few Mb DS hit 31st December that I will look into at some time (no real urgency though).


How's you and your connection doing?


P.S. more efficient and robust compiled programs are about to be released (soon).

The output is basically the same appearance as the script versions, but there is more of it to look at & it is now all harvested & generated much quicker & reliably than the script versions, using a basic text based ini file for users to easily configure drive & folder locations, some colours, pauses/delayed harvesting etc.


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Chrysalis

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #611 on: February 05, 2013, 10:54:48 AM »

one thing i learned is so many people get their distances wrong.

I see people thinking they 200m then they post their stats which indicate they double that distance.

On google maps I am 200 metres but my attenuation indicates I am 400-450m instead.  At that distance I was estimated at 65.9 down and 20 up.  I initially got 80/20 with a attainable of 110/36, it went down to 90/36 after 2 weeks and then down to 73/22 after 3 weeks and I have been there since.  A few on this forum have found it odd I had such large drops tho.
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Theagg

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #612 on: February 06, 2013, 01:04:24 PM »

one thing i learned is so many people get their distances wrong.

I see people thinking they 200m then they post their stats which indicate they double that distance.

On google maps I am 200 metres but my attenuation indicates I am 400-450m instead.  At that distance I was estimated at 65.9 down and 20 up.  I initially got 80/20 with a attainable of 110/36, it went down to 90/36 after 2 weeks and then down to 73/22 after 3 weeks and I have been there since.  A few on this forum have found it odd I had such large drops tho.

Yes, as regards attentuation and SNR values reported in the logging software, can someone here give a rough guide, assuming the line itself has no problems, as to what values you can expect for a given distance.

Example, my cabinet is around 320m away. My SNR is 5.7db for this and my dowsnstream attentuation across the bands (D0, D1, D2) reads 12.9db, 30.8db, 48.1db. So would those be the expected ballpark values for that distance, or do those figures either indicate potential issues with the line, assuming approx 320m, or that the actual route the line takes is longer ?

(An Openreach engineer who visited shortly after installation noted that there were errors on the line, that required him to go check the cabinet, after which he would pop back. But I never heard anything from him after that, since he didn't return.)
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Chrysalis

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #613 on: April 20, 2013, 04:57:27 PM »

my guess is based on that attn your line is 500-550m.

Remember the twists add distance, spare cabling, possible indirect routes, distance up pole etc.  Also that the cable run goes from the normal cabinet to VDSL cabinet and then back again before heading to your house.
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Bald_Eagle1

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #614 on: March 02, 2014, 01:54:23 PM »

Resurrecting an old thread, but FWIW, I have just found a "Chart of BT fibre broadband FTTC (VDSL2) speed against distance from the cabinet"

http://www.increasebroadbandspeed.co.uk/2013/chart-bt-fttc-vdsl2-speed-against-distance

My line length has now been confirmed as between 1000m & 1100m & I currently see see sync speeds of around 22Mbps DS & 5Mbps US.

I was able to achieve around 30/7 before crosstalk kicked in as more users were connected via my cabinet, which was almost at full capacity when last checked by a visiting engineer.


Roll on Vectoring..................................


« Last Edit: March 04, 2014, 07:09:47 AM by Bald_Eagle1 »
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