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Author Topic: Re: G.INP - Split to discuss Crosstalk.  (Read 6656 times)

kitz

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Re: G.INP - Split to discuss Crosstalk.
« on: August 21, 2015, 05:28:36 PM »

Split from the G.INP thread to discuss crosstalk

I'm not sure.   If they did advertise it then,  I think it would make those (1/3rd?) of users on ECI's a tad unhappy.

There's no fast rule about how much speed can be regained by the use of vectoring, but all I do know is that crosstalk has affected my line by 30Mbps so there are some big improvements that it could make.

Despite being on an ECI cab myself, I dont think that BT should use that as any excuse to stop roll-out to the Huaweis..  and although I'd be green if I couldnt get it, Im not so selfish as to realise that it could be of benefit to others.

BDUK is an area where it looks like they could utilise it effectively,  but saying that BDUK is strange and its not all out in the sticks. 

Look at this PCP near me - On the left is an ECI cab... on the right is a BDUK Huawei.   





I just wish that they could be a bit more open on whats going on with vectoring and let us know if there is something that can be done with the ECIs or not.


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ETA my reply was to ktz392837 - as Alec's reply wasnt there when I started to post.   

« Last Edit: August 22, 2015, 03:54:53 PM by kitz »
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Bald_Eagle1

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Re: Re: G.INP - Split to discuss Crosstalk.
« Reply #1 on: August 21, 2015, 05:50:08 PM »

There's no fast rule about how much speed can be regained by the use of vectoring, but all I do know is that crosstalk has affected my line by 30Mbps so there are some big improvements that it could make.


FWIW, I have gradually lost around 10Mbps or so DS since May 2012 on my 1100m line (from 30+Mbps to 20+Mbps) & around 2 Mbps US, but in percentage terms, that equates to around 33% loss.

That 10Mbps or so loss of speed is very noticeable here & anything that vectoring can do to improve matters would be most welcome indeed.



I'm on a legacy PlusNet product (40/10) & if I didn't need the US speed for transferring files over VPN when I work from home, I'd revert to the 40/2 entry level product that new users have to accept.

The reason for that is that when testing with PlusNet a few years ago, it was confirmed that lower US sync speeds (i.e. capped at 2Mbps) always resulted in higher DS sync speeds on my sub-40Mbps connection & vice-versa.

I more recently experimented by capping US sync speed directly via my HG612 modem, but that didn't have the same effect.



It also appears that removal of G.INP on US on my connection had a slightly negative effect on DS sync speed, but I don't have any other empirical evidence to state that as fact.
It could just be coincidental with a further increase of crosstalk.


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Chrysalis

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Re: Re: G.INP - Split to discuss Crosstalk.
« Reply #2 on: August 21, 2015, 06:29:27 PM »

likewise I dont want it to stop on the hauwei's as thats just been selfish, but like you said I would be annoyed if ECI didnt get it.

But unless BT raise the max speed, people like me and you kitz arent luckily losing too much from lack of vectoring, as I sync in the 70s and you at max speed, g.inp will make both our lines almost immune to DLM given we already have low ES counts.  The fear really with no vectoring is possible future crosstalk.

Plus to be fair I think you are the only person who has asked the question, everyone else tbb,elreg etc. dont ask or not published the answer.
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kitz

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Re: Re: G.INP - Split to discuss Crosstalk.
« Reply #3 on: August 21, 2015, 07:15:22 PM »

FWIW, I have gradually lost around 10Mbps or so DS since May 2012 on my 1100m line (from 30+Mbps to 20+Mbps) & around 2 Mbps US, but in percentage terms, that equates to around 33% loss.

That 10Mbps or so loss of speed is very noticeable here & anything that vectoring can do to improve matters would be most welcome indeed.

I'm almost at a 1/3rd loss too, and Ive noticed it on a few other lines, so I wonder if that 33% is of any relevance or just co-incidence?  I think even BS is heading for a third as last time he mentioned it he said he'd lost about 20Mb.

Quote
The reason for that is that when testing with PlusNet a few years ago, it was confirmed that lower US sync speeds (i.e. capped at 2Mbps) always resulted in higher DS sync speeds on my sub-40Mbps connection & vice-versa.

I more recently experimented by capping US sync speed directly via my HG612 modem, but that didn't have the same effect.

I wonder if that's anything to do with them making some changes to the bandplans last year - in particular the U0 band.   Previously that band could contain more of a mix.  Since they made those changes then Ive noticed on several short lines that it leaves less for the upstream. U0 has always been very heavily masked and theres not that much available for bit loading in that particular band now :(

The other bands ie D1, D2, D3, U1 & U2 are fixed and can only carry the relevant up or down tones..  so that means even if you did transfer to 40/2 it cant shift tones in or out of designated bands.... in exactly the same way that with adsl capping upstream wont affect downstream.  (obviously unless you change annex)
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NewtronStar

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Re: Re: G.INP - Split to discuss Crosstalk.
« Reply #4 on: August 21, 2015, 07:47:20 PM »

If i take my line it has crosstalk of 4dB and if vectoring removed it by 100% i would only gain 5Mbps that would take my sync rate to 40Mbps which would be just right for a 1000m line and G.INP gave 3-4 Mbps back, and on Bald_Eagles1 line G.INP made no difference.

Vectoring looks like it will help more on shorter lines than on longer lines.
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Bald_Eagle1

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Re: Re: G.INP - Split to discuss Crosstalk.
« Reply #5 on: August 21, 2015, 08:31:57 PM »

I wonder if that's anything to do with them making some changes to the bandplans last year - in particular the U0 band.   


My experiments with PlusNet were back in 2012, so perhaps not related.

I'm possibly being too cynical, but having seen the effect for myself of US sync speed being reduced at source rather than at an EU's modem, it immediately made me wonder if reducing service speeds to 40/2 is simply a ploy to increase headline DS speeds slightly as it is DS speed that is quoted when making claims of faster broadband, not the US speed.
« Last Edit: August 21, 2015, 08:35:15 PM by Bald_Eagle1 »
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GigabitEthernet

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Re: Re: G.INP - Split to discuss Crosstalk.
« Reply #6 on: August 21, 2015, 08:35:39 PM »

Wait, so Kitz your PCP has two cabinets - one BDUK and one commercial?
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Bald_Eagle1

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Re: Re: G.INP - Split to discuss Crosstalk.
« Reply #7 on: August 21, 2015, 08:44:18 PM »

If i take my line it has crosstalk of 4dB


Not sure what you mean there, NS.

How have you measured the level of crosstalk?

Quote
and if vectoring removed it by 100% i would only gain 5Mbps that would take my sync rate to 40Mbps which would be just right for a 1000m line and G.INP gave 3-4 Mbps back, and on Bald_Eagles1 line G.INP made no difference.

Vectoring looks like it will help more on shorter lines than on longer lines.

Bear in mind that my line is only 100m longer than yours.
If all my speed loss over the years is down to crosstalk & if vectoring removed its effect by 100%, I would regain around 10Mbps sync speed.

The activation of G.INP on my connection didn't increase speeds, but it did more or less completely eradicate errors, thus making it more stable.

I have been told by PlusNet that I am on the fastest speed profile available & I suppose the closeness of sync speeds/attainable rates confirm that.

So for my own connection, I have to hope that vectoring will increase sync speeds back to what they were & that G.INP helps it to remain stable & thus avoid unnecessary DLM intervention.


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kitz

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Re: Re: G.INP - Split to discuss Crosstalk.
« Reply #8 on: August 21, 2015, 08:50:40 PM »

Wait, so Kitz your PCP has two cabinets - one BDUK and one commercial?

The 2 FTTC cabs arent connected to the same PCP.  The PCP in the photo has an ECI cab. 
The Huawei cab belongs to a PCP which is on the other side of the road.
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GigabitEthernet

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Re: Re: G.INP - Split to discuss Crosstalk.
« Reply #9 on: August 21, 2015, 08:51:55 PM »

So they have two PCPs for one street?
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NewtronStar

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Re: Re: G.INP - Split to discuss Crosstalk.
« Reply #10 on: August 21, 2015, 09:34:33 PM »

Not sure what you mean there, NS.
How have you measured the level of crosstalk?

Yes i have if my crosstalk disturber is off my SNRM of 6dB will increase to 10-11dB and if i resync at that stage the sync rate will increase by 5Mbps.
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Chrysalis

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Re: Re: G.INP - Split to discuss Crosstalk.
« Reply #11 on: August 21, 2015, 10:21:59 PM »

my attainable was 110mbit when I first unlocked modem.
I currently sync at 72mbit
It was in mid to high 60s for several monthsm before dropping to under 50mbit which triggered the pair swap that got me back up to 72.

So in my case I am over 33% loss.
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licquorice

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Re: Re: G.INP - Split to discuss Crosstalk.
« Reply #12 on: August 21, 2015, 10:33:12 PM »

My attainable was about 60 Mbs at day one when I was one of the first to be connected to my cabinet, it is now about 42/44Mbs so about a 25% drop. Purely academic in my case as Infinity1 is sufficient for my needs.
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NewtronStar

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Re: Re: G.INP - Split to discuss Crosstalk.
« Reply #13 on: August 21, 2015, 10:37:28 PM »

my attainable was 110mbit when I first unlocked modem.

When did the attainable rate become more important than the actual sync rate think we discussed that the attainable rate is an unreliable target
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Weaver

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Re: Re: G.INP - Split to discuss Crosstalk.
« Reply #14 on: August 21, 2015, 10:54:44 PM »

As Newtronstar says, attainable rate is just a load of BT nonsense really. It doesn't say anything about your performance.
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