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Author Topic: Strange blip on my line ?  (Read 9615 times)

AArdvark

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Strange blip on my line ?
« on: September 23, 2014, 11:07:20 PM »

I have noticed a strange blip on my FTTC line at 22:35 23/09/2014.

My max attainable and SNRM jumped up by a large amount for 3 mins then dropped again.

Very odd.

I only noticed when I looked at a 24hr graph by random luck.

Any comments explaining what might be happening would be appreciated.

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Bald_Eagle1

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Re: Strange blip on my line ?
« Reply #1 on: September 23, 2014, 11:11:52 PM »

Maybe a neighbour rebooted or switched off their modem for 3 minutes, allowing you to experience a glorious 3 minutes worth of relatively crosstalk-free connection.

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AArdvark

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Re: Strange blip on my line ?
« Reply #2 on: September 23, 2014, 11:22:43 PM »

Maybe a neighbour rebooted or switched off their modem for 3 minutes, allowing you to experience a glorious 3 minutes worth of relatively crosstalk-free connection.

Would this be conclusive proof that I am suffering quite heavy crosstalk ?

My neighbours are only on ADSL2 at the most, would it improve if they were on VDSL2 as well or get worse ?

I am trying to anticipate the future as some of my neighbours are looking to get 'Superfast Broadband' so more is yet to come.  :(
 
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Bald_Eagle1

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Re: Strange blip on my line ?
« Reply #3 on: September 23, 2014, 11:40:09 PM »

Maybe a neighbour rebooted or switched off their modem for 3 minutes, allowing you to experience a glorious 3 minutes worth of relatively crosstalk-free connection.

Would this be conclusive proof that I am suffering quite heavy crosstalk ?



I think it would take a number of similar results that could be intentionally initiated & repeated at will by switching off/on a neighbour's connection before any 'real' conclusions could be drawn.

It might just have been an unexplainable one-off event.


Quote
My neighbours are only on ADSL2 at the most, would it improve if they were on VDSL2 as well or get worse ?


ADSL crosstalk only affects the lower of the available VDSL2 frequencies, so your higher VDSL2 frequencies are currently probably not being 'interfered' with.

As an increasing number of neighbours sign up for VDSL2 connections, I can only imagine that crosstalk will increase rather than decrease.


Quote
I am trying to anticipate the future as some of my neighbours are looking to get 'Superfast Broadband' so more is yet to come.  :(


I don't think anything can be done to avoid increasing crosstalk, at least until vectoring is introduced.

Just keep an eye open for smallish, but sudden & sustained reductions in SNRM, probably followed a few days later by a resync at lower speeds with SNRM back to 'normal' levels.

That's exactly what I have seen on my connection over 12 months or so, causing me to gradually lose around 1/3 of my DS sync speed.

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kitz

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Re: Strange blip on my line ?
« Reply #4 on: September 24, 2014, 12:24:38 AM »

I can only concur with what BE has already said... and also add that cross-talk doesnt have to come from an immediate neighbour, it could be in a different street.
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Chrysalis

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Re: Strange blip on my line ?
« Reply #5 on: September 24, 2014, 09:24:28 AM »

a large disturber probably temporarily went offline.
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WWWombat

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Re: Strange blip on my line ?
« Reply #6 on: September 24, 2014, 07:09:15 PM »

In Ireland, the reports of changes to SNRM when vectoring was turned on were of the order of 10-12dB, suggesting that was the kind of crosstalk being suffered.

The change you saw could well have been from one of your significant disturbers turning off.
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Chrysalis

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Re: Strange blip on my line ?
« Reply #7 on: September 24, 2014, 08:50:59 PM »

thats huge.

Its a real shame BT appear to not be too bothered about crosstalk.
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kitz

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Re: Strange blip on my line ?
« Reply #8 on: September 24, 2014, 09:06:28 PM »

Ive no doubt they are bothered..  but in their usual manner, they will be looking at existing technology then coming up with their own way of doing things. 

10-12dB may seem a lot..  but then again look how much some of us on this forum have seen our speeds reduced by.   BS has seen 25Mb, Ive seen 20Mb and I wasnt even first on the cab.   Aardvark hasnt been enabled that long and already hes seen some pretty steep losses :(
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Chrysalis

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Re: Strange blip on my line ?
« Reply #9 on: September 24, 2014, 09:37:45 PM »

10-12 db on my line is about 28mbit attainable, its a lot.  I would go from a 73 sync to full 80 with about 101 attainable so about 10db or so snrm with max sync.

By the way I do agree BT do seem to waste money and time redesigning the wheel.
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NewtronStar

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Re: Strange blip on my line ?
« Reply #10 on: September 24, 2014, 10:38:34 PM »


By the way I do agree BT do seem to waste money and time redesigning the wheel.

It's not funny when you see are UK Broadband is years behind other countrys, who's to blame here BT or the government  :-\ 
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WWWombat

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Re: Strange blip on my line ?
« Reply #11 on: September 25, 2014, 12:50:41 AM »

Broadband Forum has produced this document as a description of vectoring:
http://www.broadband-forum.org/marketing/download/mktgdocs/MR-257.pdf

Figure 6 shows the effects of many competing VDSL2 lines, and the impact of crosstalk on speeds - and the improvement possible by vectoring. Note: I think it refers to 0.4mm copper, so isn't directly equivalent to UK lines.

For example, at 400 metres, in a heavily used system, the majority of lines will be running between 65 and 90Mbps, while the absolute worst case is around 45Mbps, and the vectored speeds are around 120Mbps.

That shows the huge variance - huge randomness - in the way crosstalk can affect lines. Plus, of course, the huge amount of speed that can be lost.
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Chrysalis

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Re: Strange blip on my line ?
« Reply #12 on: September 25, 2014, 12:58:46 AM »

both.

ofcom are anti progress, and the gov control ofcom. e.g. FTTP would be an issue for ofcom as it sort of breaks LLU.
BT are extremely cautious with spending money which seems to have been because of their past failures in the late 1990s.

Also remember the gov refused BT's deal to do a nationwide FTTP as they wanted competition instead. Which came in the form of the cable tv companies and sky.

BT's obsession with very long testing period's and wanting to use things not the way they originally designed is entirely their own fault tho.  I guess one of the obstacles for vectoring is that it is something entirely for the purpose of improving the customer experience but without extra revenue for BT, so there is arguably no business case for it other than higher customer satisfaction.  There is the possibility vectoring will reduce fault complaints which is a business case as engineer callouts cost money.

Dont under estimate the problem of lack of competition, although we suffering from the lack of wholesale competition it is there at the retail level, in america where it isnt there, they have issues with congested peering, netflix and co having to pay isp's to uncongest routes and lower speeds.

Also the UK is only behind in cities, in rural areas the UK is probably more advanced. So I do respect its not all bad.

I also think without ofcom wholesale BT line rental would be sky rocketing but thats regulated, so BT do it at the retail level instead, and of course other telcos are mirroring BT on the line rental rises effectively making a competition failure on line rental.
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AArdvark

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Re: Strange blip on my line ?
« Reply #13 on: September 25, 2014, 02:07:17 AM »

Thanks for all the comments.
I did not reply as there was little I could say in response.

You have all confirmed what I already know BUT I still try to find an alternative answer 'just in case' I am wrong !!!  ;D

I will not hold my breath for vectoring as it took me many years to get past 4Mbps.

['Tongue in cheek' mode on]

What is needed is for some 'cheap compatible hardware' to become available to provide the Vectoring Infrastructure which may encourage BT to spend some money.

['Tongue in cheek' mode off]

(Although I really expect another 'BDUK type event' will happen and we (Joe Public) will end up paying for BT to upgrade their network again  ;D :D ::) )

If you think the situation in the UK is bad, see Australia and their 'NBN'

http://en.wikipedia.org/wiki/National_Broadband_Network

(An alternative model to do a 'National Broadband rollout' the Hard/Expensive way .....[Telstra is the Australian BT])  ;D ;D :no:
« Last Edit: September 25, 2014, 02:24:02 AM by AArdvark »
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kitz

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Re: Strange blip on my line ?
« Reply #14 on: September 25, 2014, 10:46:12 AM »

10-12 db on my line is about 28mbit attainable, its a lot.  I would go from a 73 sync to full 80 with about 101 attainable so about 10db or so snrm with max sync.

Ive just had a quick look at some of my old stats - a very approx figure is 1dB of SNRm = 3 Mbps of bandwidth.  Obviously this figure wont be the same for everyone as it will depend on how many tones can be bit loaded throughout the full spectrum
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