DSL Noise Margin

bloodyhawk

The SNR margin. Dropped yet again.
Its on: 13.9 dB 13.3 dB
I am getting little bit frustrated now

bealtine

BigGeorge wrote: »

It is a new line installed by Eircom 20 months ago. What do I do next?

Well you have crackle on the line and have disconnected everything at your end
By that I mean disconnected the extension cable at the master socket and have only the eircom line connected right?

If so, you'll have to get onto eircom, do not complain about DSL performance...only talk about crackle/noise on the line...DO NOT MENTION broadband at all...you can ask the engineer when he arrives about broadband.

ED E

Bealtine is correct, sent it to the Repair Service Center. Its Faults-Phone Faults on 1901.

BigGeorge

thanks all, called it in, it would appear there is a short somewhere on the line on the way into the house - engineer coming out next week apparently. Thanks for all the advice

Bog Standard User

the snr margin on both down and up must be 7.0db or better for stable net anything less will result in intermittant sync.


the higher the profile speed the more noise generated

its a matter of finding the right balance on your line

ie increasing speed until the snr margin db noise drops to 7.0db

anymore increases of speed will mean your noise level will be too high for a stable connection

fasterbetter

Hi

I wonder does the attainable rate (as seen on the F1000) reduce as more people get efibre installed off a particular cabinet... Mine has dropped from 115Mbps to 100Mbps in about 2 weeks since launch..the only thing that is changing is that new users are being connected....Given they are in the same bundle of copper coming through the estate from the nearest cab it seems likely that there is some additional crosstalk between copper pairs causing the SNR of everyone to be impacted...

I gather vectoring when it is turned on next year will help with this too.

In general I reckon there is no need to worry if your SNR drops a few DB as long it is well above the 6 or 7 threshold for stability..exception to this being if you are on 50Mbps and hoping to go to 70Mbps...

Does anyone know how much that speed bump takes off the SNR?

fasterbetter

BigGeorge

Looks like eircom were tinkering with the line, i.e. slowing it down, and now have the following stats:

eircom broadband: Connected

DSL Mode: ADSL_G.dmt Speed: 2464 kbps /384 kbps Line Attenuation (Down/Up): 58 dB /31 dB DSL Noise Margin: 12 dB /25 dB So they have turned down the speed from 5 to 3 to 2.6MB - is the reasonable?

lucernarian

2464 isn't a profile set by eircom. If you turn off and back on the modem it should work at 3072.

How are voice calls? Any crackling anymore? Call them back and ask for what's been done and make sure to tell them of any problem with voice calls whatsoever (they have to act on voice quality, not so much on broadband speeds).

BigGeorge

OK, reset the modem & have the following. I had been getting a mild electric shock from the phone line ( sounds crazy I know) but am not getting this anymore - tech support did say there was a short in the line. Called tech support who turned the BB speed up to 4MB & the noise margin imediately dropped to 5dB...so they turned it down again - this was all whilst I was on the line. They said there is no note on my file of any work taking place at all. Next job is to check the call quality....

Is any of this going to impact my ability to get good speeds off the efibre? thats my real concern ; am 150 m from a new cabinet & its is new copper to the cabinet

Speed: 3072 kbps /384 kbps

Line Attenuation (Down/Up): 58 dB /31 dB

DSL Noise Margin: 8 dB /25 dB

arctan

your line is fine there.... if you're 150m from cab you should be able to get 70megs no problem

bealtine

BigGeorge wrote: »

Is any of this going to impact my ability to get good speeds off the efibre? thats my real concern ; am 150 m from a new cabinet & its is new copper to the cabinet

Like arctan says you should get excellent speeds if you are really only 150 from the cabinet, also the speed you have now has no relationship to the speeds you are likely to get with VDSL, currently your line is about 4km from the exchange and the length will drop to about 150m so most of your problems should disappear when VDSL becomes available...

Techno Mick

Hi, hoping people are still reading this thread

After a 4 month wait for Eircom to install a landline, it was finally done last week, new copper from pole to point, new socket too.

By this time I had changed provider, annoyed with the wait time and Eircom's no-shows for numerous appointments.

Anyway, just wondering if they have either throttled my line or installed a lower grade of line/cable, as they did once claim that they would only install a phone carrier line if i wanted them to hurry up, bah!!!

My line now has a max of 2meg which really conflicts with these stats:

Characteristics of the current connection

Status: Connected

ModulationType: G.DMT

Upstream Downstream

CurrRate(kbps) 256 2048
MaxRate(kbps) 928 4384
NoiseMargin(dB) 25.0 17.9
Attenuation(dB) 56.0 31.5
Power(dBm) 11.9 18.3


Now, I'm not sure if there is a cabinet close to me, but I believe that I am approx 5 - 5.5km from main exchange, yet these stats (Attenuation) suggest that I am 2.2km from an exchange.

speedguide.net and kitz both recon up to 14meg down...

Any thoughts or suggestions appreciated here please.

lucernarian

You're probably on a longer line and eircom will tell you that "your line can't handle any more speed" even though the stats on your modem will clearly say otherwise. Above a certain distance, eircom's systems enforce these kinds of limits and this has been the case for any DSL provisioned line for the past 3 years or so. I think it was when they launched NGB that this happened.

It's set by the "unified gateway" i.e. eircom wholesale's line management systems for use by operators and usually, changing provider won't change this.

Your stats are good enough that the line may be short enough to offer some flexibility on max speed but then the attenuation figures do suggest a line at least 6km long. My family's line got 54dB and clocked in at 6.5km when eircom tested it.

Techno Mick

Hi TBC, thanks for fast reply.

Yes we are on NGB, from Digiweb, who only offer up to 8meg here.

I was working off an attenuation of 31.5 and not 56, as I was of the belief that you calculated from the down value??

Apart from this, do you see any point in raising this with Digiweb or Eircom in the hope of getting more speed?

lucernarian

Techno Mick wrote: »

Hi TBC, thanks for fast reply.

Yes we are on NGB, from Digiweb, who only offer up to 8meg here.

I was working off an attenuation of 31.5 and not 56, as I was of the belief that you calculated from the down value??

Apart from this, do you see any point in raising this with Digiweb or Eircom in the hope of getting more speed?

31.5 is the upstream, 56 is the downstream. Unless the attenuation is somewhere around 5 dB or less, or the line is faulty, downstream has higher attenuation than upstream.

Also modems can only report a max attenuation of 31.5 dB upstream and 63.5 dB downstream attenuation when using plain old ADSL. Your real upstream attenuation is possibly higher.

Techno Mick

To_be_confirmed wrote: »

31.5 is the upstream, 56 is the downstream. Unless the attenuation is somewhere around 5 dB or less, or the line is faulty, downstream has higher attenuation than upstream.

Also modems can only report a max attenuation of 31.5 dB upstream and 63.5 dB downstream attenuation when using plain old ADSL. Your real upstream attenuation is possibly higher.

Hmm, ok, seems my router is displaying up as down and vice versa so....

fat-tony

Techno Mick wrote: »

Hmm, ok, seems my router is displaying up as down and vice versa so....

Or else there is something wrong with the cabling. Your other downstream figures seem consistent. It's just that you would never have downstream attenuation lower than upstream if there wasn't some sort of cabling issue - could be even in your house environment.

Techno Mick

Thanks Fat Tony,

Seeing as the line was installed last Monday, from pole to socket, as there was no line in this house, where do you think the (possible) fault could be?

As for house environment, it runs no more than 15 feet from outside to socket, overground from pole, 25 feet approx. Another 35 feet to their 'main pole and connection'.

fat-tony

Your house environment would only be an issue if you had extension spurs all over the house and theoretically the new master socket (NTU) should isolate you from such issues. But this would not seem to be the case in your situation as you have described. Can you grab the screen on your DSL status page and post that? It would be unusual in the extreme to have higher upstream than downstream attenuation.

Techno Mick

hey Tony,

I couldn't do a screen shot of stats, but the stats I posted are the exact c&p from the router screen.

Characteristics of the current connection

Status: Connected

ModulationType: G.DMT

Upstream Downstream

CurrRate(kbps) 256 2048
MaxRate(kbps) 928 4384
NoiseMargin(dB) 25.0 17.9
Attenuation(dB) 56.0 31.5
Power(dBm) 11.9 18.3

fat-tony

Yea but 56dB upstream vs 31dB downstream doesn't make sense

If you want to capture a screen shot, just press cntrl and Print and then paste it into Paint or whatever image manipulation program you use. Then save it as a png or jpg.

Techno Mick

fat-tony wrote: »

Yea but 56dB upstream vs 31dB downstream doesn't make sense

LOL, idk mate, but that's what it says....

Techno Mick

hope it posts this time

fat-tony

Something wrong with the line connection (or your modem) if the upstream attenuation is higher than downstream.

lucernarian

Just a programming mistake in the modem. Upstream cannot be reported as greater than 31.5 dB under g.DMT (ADSL 1).

fat-tony

To_be_confirmed wrote: »

Just a programming mistake in the modem. Upstream cannot be reported as greater than 31.5 dB under g.DMT (ADSL 1).

Upstream is 56dB - downstream is 31.5dB

lucernarian

fat-tony wrote: »

Upstream is 56dB - downstream is 31.5dB

That's not possible under the g.dmt spec. It's a modem reporting error. They swapped around the downstream and upstream values in that column by mistake. I bet you that a telnet session with the modem would report the values correctly.

I did some googling and found this webpage (http://www.thinkbroadband.com/faq/sections/radsl.html#301) which supports my conclusions.

I should correct one thing I said earlier, the G.dmt spec reports signal attenuation values up to 63.5 dB for both upstream and downstream but countless reports of line stats show 31.5 dB is a frequently encountered max ADSL upstream attenuation limit, perhaps implemented by a not-quite-compliant handling of g.dmt. There is one line I've used which went from an ADSL upstream attenuation of 31.5 dB to 33.4 dB when ADSL2 was switched on.

fat-tony

I thought the router had reversed the values or the values had been cut and pasted incorrectly somehow (which is why I asked the OP for a screen print), but it may well be that the router is reporting incorrectly as you say and that the downstream attenuation is actually 56dB and @Techno Mick is probably correct in his assumption that he is 5km from the exchange and that the speed is probably correct for that distance.

fat-tony

To_be_confirmed wrote: »

There is one line I've used which went from an ADSL upstream attenuation of 31.5 dB to 33.4 dB when ADSL2 was switched on.

This may well be related to the reporting limit you referred to for upstream attenuation in some routers. A move from ADSL to ADSL2 would increase attenuation (for the same length of cable) due to the higher frequencies involved.

lucernarian

fat-tony wrote: »

This may well be related to the reporting limit you referred to for upstream attenuation in some routers. A move from ADSL to ADSL2 would increase attenuation (for the same length of cable) due to the higher frequencies involved.

Not in the case of upstream channels (depending on the annex, and Annex A as used in Ireland uses same upstream channels as ADSL1. It's simply reported differently for ADSL2 or ADSL2+