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Standard User Steve_D
(experienced) Tue 18-Jun-13 11:22:50
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Effects of crosstalk on FTTC


[link to this post]
 
Are there any reliable figures for how much crosstalk is affecting FTTC lines? In the last month or so I've seen around 20Mbit shaved off my speed, from a high of around 72Mbit to now being the low 50s. I've tried repeated early morning re-syncs, but it hasn't improved.

Edited by Steve_D (Tue 18-Jun-13 11:26:20)

Standard User Chrysalis
(legend) Tue 18-Jun-13 12:05:15
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Re: Effects of crosstalk on FTTC


[re: Steve_D] [link to this post]
 
no because its inconsistent.

I suggest you unlock your modem you can then see if there is any point in resyncing by checking your snrm.

BT Infinity 2 Since Dec 2012
Standard User StephenTodd
(experienced) Wed 19-Jun-13 00:08:59
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Re: Effects of crosstalk on FTTC


[re: Steve_D] [link to this post]
 
Have those been modem or router resyncs?

Best to leave the modem well alone; it's sync speed will increase automatically when (and only when) DLM permits.
Too may resets and DLM may lower your speed.

What is needed is a router PPPoE disconnect/reconnect; to force the IP profile to match the sync speed.

As Chrysalis says, if you have an unlocked modem, you will know when it is worth disconnect/reconnecting the router.
However, too much router disconnect/reconnecting or resetting won't do any harm.

--
Moved (with trepidation turned relief) to BT Infinity 2 for upload speed. Happy BE user for several years.


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Standard User Bradxscape
(learned) Wed 19-Jun-13 09:47:42
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Re: Effects of crosstalk on FTTC


[re: Steve_D] [link to this post]
 
I too have had a massive reduction in speed. I used to have around 78Mbits and now around 50's, I've been on to BT who sent three engineers out, the first two said that the speed I'm currently getting is the best I can get? Which I found extremely amazing as Iíve had a totally stable line and have always had good speeds. Anyway on the third visit the engineer told me that they only have 4 weeks of data to show what speeds Iíve been getting, so if you donít get onto them straight away you donít seem to be able to support your claim!! *very annoying* The engineer did resolve the issues by resetting something (no idea) and I was back to my Ďnormal speeds. A few weeks later and itís all happening again! ..the thought of having to go through the very tiring conversation with the Indian call centre and take more time off work to get another engineer round is draining!
Standard User BatBoy
(legend) Wed 19-Jun-13 12:13:12
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Re: Effects of crosstalk on FTTC


[re: Bradxscape] [link to this post]
 
What may have happened is that the engineer reset your profile without fixing the fault which caused DLM to lower your profile, so DLM has again lowered your profile.

You need an engineer to fix the fault.


__________________________________________________________________________The back pedalling starts here__________________
Standard User Bradxscape
(learned) Wed 19-Jun-13 14:26:31
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Re: Effects of crosstalk on FTTC


[re: BatBoy] [link to this post]
 
May be, what is strange is that its taken weeks for the fault to happen again?
Standard User Steve_D
(experienced) Wed 19-Jun-13 15:48:58
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Re: Effects of crosstalk on FTTC


[re: StephenTodd] [link to this post]
 
These have been modem resets. I really do need to bite the bullet and flash the modem to get some stats. I've not bothered before just because it was working fine, and I didn't feel the need to tinker for the sake of it. A far cry from the DMT days of tweaking my SNR margin to get the most from my 5Mbit line. The resets have been fairly infrequent, maybe once a week 3 or 4 times. Is that likely to cause trouble?
Standard User Bald_Eagle1
(experienced) Thu 20-Jun-13 22:58:38
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Re: Effects of crosstalk on FTTC


[re: Steve_D] [link to this post]
 
It's a shame you didn't manage to grab any stats & graph them when the connection was at its best as 'evidence' that it has now deteriorated.

My connection has dropped from a steady sync speed of just below 30 Mbps to just over 20 Mbps since December 2012.

I can see changes in in my QLN graph that points to it being increased crosstalk.

BT's response was to lower my speed estimate from 30 Mbps to 23.3 Mbps, so I am now no longer suffering from a 25% speed drop from estimated speed that is apparently some sort of fault threshold.

2 engineers have visited recently & carried out the usual PQT & Eclipse test, both passing with flying colours for line quality, but the most recent engineer did phone someone who confirmed that my cabinet is now almost at capacity - again indicating increased crosstalk as the likely culprit.
Standard User lockyatlrg
(fountain of knowledge) Thu 20-Jun-13 23:27:32
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Re: Effects of crosstalk on FTTC


[re: Steve_D] [link to this post]
 
From what ive seen, each line added to my cab shaved 0.6dB off my SNR.

BT Infinity
ROUTER:-Netgear WNDR37AV
JDSU Stats
Attainable 105977D 38659U
Sync 79999D 20000U
Attenuation: 5.4 SNR: Down 13.1 Up 24.3
Line Length 160meters
Standard User Chrysalis
(legend) Fri 21-Jun-13 03:28:17
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Re: Effects of crosstalk on FTTC


[re: lockyatlrg] [link to this post]
 
my cab is now full 6 months after it got made live.

I have 4 known instances of loss of snr/sync speed.

in order

#1 15mbit lost by 1 line.
#2 18mbit lost by 1 line
#3 2mbit lost by 1 line
#4 2mbit lost during fault period/engineer.

so first 3 crosstalk loss's by 3 lines, and the other 120 or so lines in cab no affect on my line.

on my line 3db of snr is about 13mbit of sync speed. so based on that can guess snr impacts.

BT Infinity 2 Since Dec 2012
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