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Author Topic: Drop outs, now N/A in some Noise Margin stats....???  (Read 696 times)

cosrush

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Drop outs, now N/A in some Noise Margin stats....???
« on: July 07, 2019, 11:13:55 AM »

Hi,
I hope somebody can explain what the following may mean.

I've had a good and stable connection for sometime with the very occasional drop out (which I guess is to be expected) however, last week we had a number of dropouts all within the space of about 2 hours.
The net result is I have lost 14Mb speed and notice that in my router stats it now shows the following 'N/A' in the Noise margin stats.

Anyone know what this means?
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re0

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Re: Drop outs, now N/A in some Noise Margin stats....???
« Reply #1 on: July 07, 2019, 11:22:25 PM »

U3 and U4 are not used, so normal for it to not be applicable. D2 (which I actually think should be D3) can be utilised, but the conditions of your connection appear not to allow for allocation of bits.

How long have you had the connection for?
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burakkucat

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Re: Drop outs, now N/A in some Noise Margin stats....???
« Reply #2 on: July 07, 2019, 11:25:50 PM »

A VDSL2 (ITU-T G.993.2), Profile 17a, circuit has a number of bands for each direction of the data flow. Looking at the entire spectrum, from low to high frequencies, they are US0, DS1, US1, DS2, US2 & DS3 in that order. (Where US is upstream, transmit or go and DS is downstream, receive or return.)

For some reason, your modem/router has incorrectly labelled the downstream bands as DS0, DS1 & DS2 rather than the conventional DS1, DS2 & DS3. That's not a problem, though it can be source of confusion. Now I don't recognise the output . . . what make and model is it, please?

So from looking at that image, all I can say is that something has happened such that no signal is being carried in those bands which are marked "N/A". With less signal being received, the throughput speed will be reduced and there's nothing else that can be said.

I've just had a sudden thought. Are you located in the UK? If not, that would account for why I do not recognise the output from your modem/router.

Edit: I see that re0 has posted whilst I was typing the above.
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cosrush

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Re: Drop outs, now N/A in some Noise Margin stats....???
« Reply #3 on: July 08, 2019, 07:27:41 AM »

Thanks for the replies :)

Router is a Netgear D7000. I'm fairly certain that the bands now marked as N/A had populated figures in them previously.

And yes in the UK.

Is a reboot likely to do anything? Is it worth a try?
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kitz

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Re: Drop outs, now N/A in some Noise Margin stats....???
« Reply #4 on: July 08, 2019, 08:58:19 AM »

I suppose it won't harm giving the modem a reboot now since it was several days ago that you had the period of instability.

re0 & b*cat have already explained the bands.   

D3 (or what your modem has marked as D2) uses the highest frequencies and the tones in this band are most likely to be affected by noise and therefore at the time of last sync there was just too little SNRm in D3 to be able to load any bins in that band.  I note atten of 64.8dB recorded in that band so it could be possible that sometimes you can load some tones in D3 and sometimes you can't.

SNRM in the other DS bands is still only at 3.1dB (so I'm assuming you are on a Huawei cab with xdB) so it doesn't look like things have improved too much overall - unless the previous period of interference was only affecting those tones in D3.   However, if you are on an ECI cab - which has a target SNRM of 6.3dB  - then you could end up with even less sync speed than you have now. :/


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tubaman

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Re: Drop outs, now N/A in some Noise Margin stats....???
« Reply #5 on: July 08, 2019, 09:00:30 AM »

Could this be a bad case of crosstalk from a new FTTC subscriber killing the previously usable DS3 ('D2') band?
As you are already at 3dB SNR on the DS I doubt that a reboot will make any difference, but it wouldn't hurt to try.
 :)
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cosrush

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Re: Drop outs, now N/A in some Noise Margin stats....???
« Reply #6 on: July 12, 2019, 09:34:36 AM »

Ok so I think I 'may' have found an issue.

My ISP package of 55/10 has been switched to 40/10 as they 'no longer provide a 55/10 package'.

Explains my speed drop.

 >:(
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flilot

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Re: Drop outs, now N/A in some Noise Margin stats....???
« Reply #7 on: July 12, 2019, 02:40:18 PM »

Ok so I think I 'may' have found an issue.

My ISP package of 55/10 has been switched to 40/10 as they 'no longer provide a 55/10 package'.

Explains my speed drop.

 >:(
They did this without e-mailing or sending you a letter to let you know? 
Who is this ISP, for future reference?
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re0

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Re: Drop outs, now N/A in some Noise Margin stats....???
« Reply #8 on: July 12, 2019, 03:31:15 PM »

But the sync rate in your initial attachment is more than 40 Mbps - it was showing approx. 42 Mbps. Unless this weirdly refers to the attainable, which it doesn't look like at all since it clearly indicates that it is the link rate.

My assumption is that they have not changed your package at all, but rather they wouldn't be able to supply 55/10 to you if you ordered now due to your estimates. Your speed loss likely stems from new subscribers creating crosstalk - this has been mentioned before in this thread.
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j0hn

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Re: Drop outs, now N/A in some Noise Margin stats....???
« Reply #9 on: July 12, 2019, 03:42:52 PM »

Ok so I think I 'may' have found an issue.

My ISP package of 55/10 has been switched to 40/10 as they 'no longer provide a 55/10 package'.

Explains my speed drop.

 >:(

Sounds like waffle.
Not aware of any ISP giving "free" downgrades. Plenty doing the opposite.

That would surely only be possible if they were to contact you and offer to release you from your contract as they are removing your current package.
Alternatively ISP's can do this when you recontract with them.

But the sync rate in your initial attachment is more than 40 Mbps - it was showing approx. 42 Mbps. Unless this weirdly refers to the attainable, which it doesn't look like at all since it clearly indicates that it is the link rate.

My assumption is that they have not changed your package at all, but rather they wouldn't be able to supply 55/10 to you if you ordered now due to your estimates. Your speed loss likely stems from new subscribers creating crosstalk - this has been mentioned before in this thread.

Definitely the sync rate shown.

ISP running a GEA Test should show the line profile as 55Mb.
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anything