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Author Topic: VDSL2 - No Sync BT Checker says all ok 2.5KM from cabinet  (Read 12486 times)

VSDL_NoSync

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VDSL2 - No Sync BT Checker says all ok 2.5KM from cabinet
« on: March 23, 2012, 08:49:00 PM »

Hi There,  sort of hoping that the BT expert comes along and see this or if anyone can help or point me int he correct direction.  I just had an order for Infinity nightmare, engineer came out and tried to install but no sync on the line.  To cut a very long story short I am being told that I am to far from the cabinet.  Even though the checker says i am fine and tells me I can get 24Mbits.  And to rub salt in it i just got an email saying hello you can get Bt infinity now.

The tech guys checked the line and said its 6KMm i have walked the line its all overhead well a mixture of overhead and some small underground parts.  But I know where it is as i can see it walk measures 2.5KM.  There are however a few posts with about 5 meters of looped cable up there sigh is this my missing distance every few posts has at least 5 meters of loop on the cable.

The have told me the attenuation on the line is 70DB apparently this is not good

How do i get open reach to fix the line shorten it to its true distance and then fix the attenuation.  I get 1M adsl just now so cannot understand why I cannot get VDSL2 my hair is starting to fall out.

I live in the back of beyond and need a decent connection

Please help me me Nice Bt expert
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burakkucat

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Re: VDSL2 - No Sync BT Checker says all ok 2.5KM from cabinet
« Reply #1 on: March 23, 2012, 10:16:12 PM »

Well, we cannot have your hair falling out -- it will make a mess on the floor.  ::)

I think we need to start at the beginning, as you currently do have an ADSL service.

What make and model modem/router are you using? Please post the full statistics from that device. Ideally we would like to see (at a minimum) the reported attenuation, the sync speed and the signal to noise margin for both downstream & upstream.

Would you be willing to tell us the approximate area of your "back of beyond"?
Would you be prepared to enter your telephone number into the checker at Sam Knows and then post the link to the result page?
Would you also use the BT Wholesale Broadband Availability Checker and the BT Performance Tester, posting (via a copy/paste) the results (less any confidential information).

Finally, would you be willing, via a PM, to tell me your postcode?

Certainly a 70 dB DS attenuation is extremely poor but I am encouraged to read that you achieve a 1 Mbps DS sync.
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VSDL_NoSync

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Re: VDSL2 - No Sync BT Checker says all ok 2.5KM from cabinet
« Reply #2 on: March 23, 2012, 10:58:08 PM »

Hi There

here are the web page results for the echange postcode check and the phone number checker.  I am not using a modem as the BT engineer never got that far he could not find a sync on the line coming into the house.  The lines are mostly overhead and a couple of bits underground.

http://www.samknows.com/broadband/exchange/ESLVS
http://www.dslchecker.bt.com/adsl/ADSLChecker.TelephoneNumberOutput
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burakkucat

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Re: VDSL2 - No Sync BT Checker says all ok 2.5KM from cabinet
« Reply #3 on: March 23, 2012, 11:30:39 PM »

Thank you for posting the link to your telephone exchange. I see that Livingston Station has been classified by Offcom as a "Market 3" exchange and there are a number of suppliers available.

Unfortunately the other link does not provide anything useful. You will need to make a copy and then paste that copy within quote tags, to enable us to see the results.

In you initial post, you make mention of 1 Mbps DS sync (erm, actually "I get 1M adsl just now"), which implies that you must have some form of modem/router connected to the line. Or have I mistaken what you were trying to tell us?  ???

As it is nearly 2330 hours, I feel a cat-nap coming on. Let's now wait for daylight and perhaps others will have some useful suggestions and advice. Certainly Walter will be able to say something about excessively long and manky lines!
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VSDL_NoSync

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Re: VDSL2 - No Sync BT Checker says all ok 2.5KM from cabinet
« Reply #4 on: March 23, 2012, 11:38:46 PM »




 on Exchange LIVINGSTON STATION

Your exchange is ADSL enabled, and our initial test on your line indicates that your line should be able to have an ADSL broadband service that provides a fixed line speed up to 512Kbps. However, due to the length of your line, an engineer visit may be required, who will, where possible, supply the broadband service.

Our test also indicates that your line currently supports an estimated ADSL Max broadband line speed of 1Mbps; typically the line speed would range between 750Kbps and 2.5Mbps.

Our test also indicates that your line currently supports an estimated ADSL2+ broadband line speed of 1Mbps; typically the line speed would range between 1Mbps and 3.5Mbps. Our test also indicates that your line could support an estimated ADSL 2+ Annex-M broadband upstream line speed of 500Kbps and downstream line speed of 1Mbps; typically the downstream speed would range between 1Mbps and 3.5Mbps.

Our test also indicates that your line currently supports a fibre technology with an estimated WBC FTTC Broadband where consumers have received downstream line speed of 20.4Mbps and upstream line speed of 5Mbps.

The actual stable line speed supportable will be determined during the first 10 days of use. This speed may change over time, to ensure line stability is maintained.

If you decide to place an order, a further test will be performed to confirm if your line is suitable for the service you wish to purchase.

Thank you for your interest.

Please note that postcode and address check results are indicative only. Most accurate results can be obtained from a telephone number check.
Note: If you have already placed an order for Broadband and now wish to change to a new supplier, then you will need to cancel the existing order with your service provider or your new request will be rejected. If you do not know who the current Service Provider is, please contact your new Service Provider, who would be able to help you to resolve this issue.
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VSDL_NoSync

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Re: VDSL2 - No Sync BT Checker says all ok 2.5KM from cabinet
« Reply #5 on: March 23, 2012, 11:46:35 PM »

Here is the information from BT tech team



Thanks for your patience whilst I went to the THD team.
 
They've taken a look and this is what they've come back with.
 
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.
 
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
 
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.
 
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Bald_Eagle1

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Re: VDSL2 - No Sync BT Checker says all ok 2.5KM from cabinet
« Reply #6 on: March 24, 2012, 08:24:43 AM »

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


Quote


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/2006/12/20130045/3

Although 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.
 
Quote
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]
« Last Edit: March 24, 2012, 08:44:43 AM by Bald_Eagle1 »
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Bald_Eagle1

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Re: VDSL2 - No Sync BT Checker says all ok 2.5KM from cabinet
« Reply #7 on: March 24, 2012, 08:50:42 AM »

Just for reference, the 2 attached graphs show a super speed connection (almost 130Mb attainable DS - currently capped at 40Mb) .
« Last Edit: March 24, 2012, 08:54:05 AM by Bald_Eagle1 »
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Black Sheep

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Re: VDSL2 - No Sync BT Checker says all ok 2.5KM from cabinet
« Reply #8 on: March 25, 2012, 10:21:41 AM »

Hi There,  sort of hoping that the BT expert comes along and see this or if anyone can help or point me int he correct direction.  I just had an order for Infinity nightmare, engineer came out and tried to install but no sync on the line.  To cut a very long story short I am being told that I am to far from the cabinet.  Even though the checker says i am fine and tells me I can get 24Mbits.  And to rub salt in it i just got an email saying hello you can get Bt infinity now.

The tech guys checked the line and said its 6KMm i have walked the line its all overhead well a mixture of overhead and some small underground parts.  But I know where it is as i can see it walk measures 2.5KM.  There are however a few posts with about 5 meters of looped cable up there sigh is this my missing distance every few posts has at least 5 meters of loop on the cable.

The have told me the attenuation on the line is 70DB apparently this is not good

How do i get open reach to fix the line shorten it to its true distance and then fix the attenuation.  I get 1M adsl just now so cannot understand why I cannot get VDSL2 my hair is starting to fall out.

I live in the back of beyond and need a decent connection

Please help me me Nice Bt expert

Hi. Firstly, assuming your post is aimed ay myself, I can assure you I'm no 'Expert'. That accolade should be reserved for our boffins at Martlesham.  ;D

Secondly, unfortunately I haven't yet had the necessary 'hands on time' with regard to VDSL installtion/faulting to be of any great help to you. I've been involved in quite a few, but not enough to form opinions of speed - distance - attenuation - SNR factors. What I can tell you, is that Mr Bald Eagle (who has posted a great insight into VDSL on this thread) is probably more savvy with the technicalities surrounding these issues, than I. :)

Having never used a 'Speed guess-checker', I'm again not au-fait with the results given. There does seem to be a massive discrepancy between your calculation of 2.5Km and BT's 6Km ?? Are you a giant, or something ?? :lol:

Reading the results of circuit length being 8.1Km, and Distribtion Point being 6.5Km, I can only guess that the DP reading of 6.5Km is the actual main overhead pole ,(not to be confused with the carrier poles), which we commonly call the 'Distribution Point'. Therefore, you may be mistakenly thinking you are only 1.5Km from the Cabinet supplying VDSL ?

May I ask where you live (just the town/city from which your Exchange is based) just in case I can see our 'Network Records' for that area ??
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AdrianH

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Re: VDSL2 - No Sync BT Checker says all ok 2.5KM from cabinet
« Reply #9 on: March 25, 2012, 11:41:39 AM »



May I ask where you live (just the town/city from which your Exchange is based) just in case I can see our 'Network Records' for that area ??


http://www.samknows.com/broadband/exchange/ESLVS
Hi There

here are the web page results for the echange postcode check and the phone number checker.  I am not using a modem as the BT engineer never got that far he could not find a sync on the line coming into the house.  The lines are mostly overhead and a couple of bits underground.

http://www.samknows.com/broadband/exchange/ESLVS
http://www.dslchecker.bt.com/adsl/ADSLChecker.TelephoneNumberOutput

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burakkucat

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Re: VDSL2 - No Sync BT Checker says all ok 2.5KM from cabinet
« Reply #10 on: March 25, 2012, 10:33:16 PM »

Quote from: Black Sheep
May I ask where you live (just the town/city from which your Exchange is based) just in case I can see our 'Network Records' for that area ??

Thank you for posting the link to your telephone exchange. I see that Livingston Station . . .

b*cat is disappointed that b*sheep failed to notice the above quoted sentence and a half.  :P
« Last Edit: March 26, 2012, 12:41:24 AM by burakkucat »
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renluop

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Re: VDSL2 - No Sync BT Checker says all ok 2.5KM from cabinet
« Reply #11 on: March 25, 2012, 11:55:15 PM »

FWVLIW I did some calcs based on local knowledge and it suggests that the drop in speed is about 0.1MB/25m.
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VSDL_NoSync

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Re: VDSL2 - No Sync BT Checker says all ok 2.5KM from cabinet
« Reply #12 on: March 26, 2012, 12:21:43 AM »

Chaps, Many Thanks for all the great replies much appreciated.  I will keep you posted on the outcome.  I am really inspired by the possibility that there might be a fault on the line "High resistance fault"  Maybe just maybe there is a glimmer that I can get a connection.  Depending on the cost to get it fixed that is.
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Black Sheep

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Re: VDSL2 - No Sync BT Checker says all ok 2.5KM from cabinet
« Reply #13 on: March 26, 2012, 04:23:57 PM »

Quote from: Black Sheep
May I ask where you live (just the town/city from which your Exchange is based) just in case I can see our 'Network Records' for that area ??

Thank you for posting the link to your telephone exchange. I see that Livingston Station . . .

b*cat is disappointed that b*sheep failed to notice the above quoted sentence and a half.  :P

Not as disappointed as me buddy.  :-[ I have to practically speed-read the threads as I've got a lot on most of the time. That's my defence in court, should it get that far. :P
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Black Sheep

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Re: VDSL2 - No Sync BT Checker says all ok 2.5KM from cabinet
« Reply #14 on: March 26, 2012, 04:27:03 PM »

Chaps, Many Thanks for all the great replies much appreciated.  I will keep you posted on the outcome.  I am really inspired by the possibility that there might be a fault on the line "High resistance fault"  Maybe just maybe there is a glimmer that I can get a connection.  Depending on the cost to get it fixed that is.

If there is a 'HR Fault', it won't cost you a penny on the proviso you've tested at the 'Test Socket', and you know your own equipment to be working OK. The only disclaimer to that is if the wires feeding your premises, and actually within your curtiledge, have been accidentally or deliberately tampered with.
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