DSL Noise Margin

damienf1

Hi,

I was wondering if anyone could tell me about the readings that i took for my broadband package (Eircom) i am on 8mb. Are the readings good for bad

Line Attenuation (Down/Up) 34 dB /18 dB

DSL Noise Margin: 9 dB /24 dB

Speed 8128 kbps /512 kbps

Thanks.

jor el

http://www.kitz.co.uk/adsl/linestats.htm
http://www.kitz.co.uk/adsl/max_speed_calc.php

Those readings are fine. 34dB attenuation is probably right on the edge of being able to support the full 8Mbps, but apart from that they're good.

Are you experiencing any problems?

Vic Vinegar

Hi, sorry for the mild hijacking...

What are these stats like? they don't seem too good from what little i know

relative capacity occupation: 96% 
noise margin upstream: 7.0 db
output power downstream: 19.5 dbm
attenuation upstream: 28.5 db

relative capacity occupation: 124% 
noise margin downstream: 6.5 db
output power upstream: 12.0 dbm
attenuation downstream: 40.0 db

We're supposed to be on 12mb but we are getting constant disconnects

jor el

http://www.kitz.co.uk/adsl/max_speed_calc.php
Your attenuation is way to high for 12Mbps, there's no way it'll be stable at that speed. The SNR margin is also very low. Your speed should be reduced to 6M or lower.

Vic Vinegar

jor el wrote: »

http://www.kitz.co.uk/adsl/max_speed_calc.php
Your attenuation is way to high for 12Mbps, there's no way it'll be stable at that speed. The SNR margin is also very low. Your speed should be reduced to 6M or lower.

I thought as much! i'll see about getting it reduced to 6mb or something, the router keeps disconnecting and resyncing at a lower speed each time until it's less than half of 1mb, is that normal for the line noise situation?

lucernarian

It's possible that the modem itself is not doing a very good job of being "rate adaptive" but the main problem is the line speed, you would be doing reasonably well to get 6mbits on ADSL1 which is what you will be reduced to if you get the speed moved down to 6mbps max. If they initially sold you up to 12 mbps on that line, possibly the line quality has deteriorated since then for some external reason.

There is another possibility, that local electrical interference is causing intermittent dropouts. I have used 17mbit ADSL2 connections with a signal margin of 6dB but I never got any dropouts. Local line conditions will vary. Still, I suspect using a different brand/model of modem would help. Along with a speed downgrade!

number_1

My line stats are:

ADSL 1
Speed: 3072 kbps /384 kbps
Line Attenuation (Down/Up): 7 dB /4 dB
DSL Noise Margin: 28 dB /12 dB

There is 430m of copper wire to the exchange.

Eircom have told me that my line can't support broadband speeds higher than 5 Mbps. Does that sound correct? The above links suggest that I should have no problem receiving speeds up to 24 Mbps!

Can the Eircom line test result be wrong? If a 24 Mbps product was ordered could it work regardless of the line test result, or does the line test result mean that the line has been physically throttled to max out at 5 Mbps? ISPs don't seem to even consider providing the higher speed products due to the low line test result.

kaahooters

number_1 wrote: »

My line stats are:

ADSL 1
Speed: 3072 kbps /384 kbps
Line Attenuation (Down/Up): 7 dB /4 dB
DSL Noise Margin: 28 dB /12 dB

There is 430m of copper wire to the exchange.

Eircom have told me that my line can't support broadband speeds higher than 5 Mbps. Does that sound correct? The above links suggest that I should have no problem receiving speeds up to 24 Mbps!

Can the Eircom line test result be wrong? If a 24 Mbps product was ordered could it work regardless of the line test result, or does the line test result mean that the line has been physically throttled to max out at 5 Mbps? ISPs don't seem to even consider providing the higher speed products due to the low line test result.

id love to know this too, my bb is syncing at 5 mb, but, kitz says its on adsl 2 adn capable of 24mb.

eircom just lazy or really not know?

daffy_duc

ADSL2+ can go further faster on lower signal than ADSL1 can with the same SNR.
So keep that in mind when Eircom tells you your ADSL1 line can only do 5Mbit when an ADSL2+ can do 24Mbit on the same figures.

number_1

Granted ADSL 1 has lower speeds than ADSL 2, but the links above suggest that a downstream attenuation of 7 dB should still allow speeds up to 8 Mbps on ADSL 1, not 5 Mbps.

jor el

daffy_duc wrote: »

ADSL2+ can go further faster on lower signal than ADSL1 can with the same SNR.
So keep that in mind when Eircom tells you your ADSL1 line can only do 5Mbit when an ADSL2+ can do 24Mbit on the same figures.

Not quite. A line that is only capable of 5Mbps on ADSL would not be capable of much more than that on ADSL2+. The difference in speed is only apparent at low line lengths with low attenuation.

The line stats quoted though should be well capable of 8M on ADSL, or close to 24M on ADSL2+. If there's a problem with that line that is restricting the speed to 5M, then 24M is not going to be possible either.

Solair

You might squeeze a few extra dB of noise margin out of the line if you simplify your internal wiring.

Basically, disconnect absolutely everything except the first eircom-branded socket. Then plug your DSL splitter in there and plug your modem and cordless base station in there. With modern cordless phones, you really don't need lots of extension sockets all over the house, and they just add noise to DSL lines.

Check the line for any audible crackles too. Pick up the phone (preferably a simple non-cordless), dial any digit to silence the dial tone and listen for any loud crackles.

If the line's noisy, ring your phone provider and tell them that you occasionally can't hear people on it due to the noise. They'll then have to investigate and fix it.

It's possible the line's just too long to provide decent DSL signals. If that's the case, you might be better off looking at some of the fixed antenna wireless systems that put a little ariel on your roof. Some of them, like Nova Networks in Cork are excellent and very comparable to a good quality DSL line.

Don't go with anything that is working on 3G or WiMax other "mobile broadband" devices. They are simply not suitable for serious broadband and won't provide a good enough connection for gaming or VoIP etc.

lucernarian

The signal margin on those stats is very substantial. If eircom are saying it can't do more than 5 mbps, you're being limited due to capacity problems at the exchange or else eircom's testing system has simply made a mistake. There was a thread about this before where someone lived 100m from the exchange and wasn't allowed to connect at the full 8 mbps initially. Nag and pursue this, post on the Talk to: Eircom forum if necessary.

arctan

could be like my situation and the cable from the DP to my house is in ribbons ...

do you hav a cable that comes into the house through the concrete floor ?

I'm in an 8 meg area, but my line struggles to get 1.6 megs, copper round my way is fooked ...

even the eircom line stats say I'll only get 1.8 max .. although i'm hoping to get that tested from the socket out, soon, to verify the remote test

Vic Vinegar

jor el wrote: »

http://www.kitz.co.uk/adsl/max_speed_calc.php
Your attenuation is way to high for 12Mbps, there's no way it'll be stable at that speed. The SNR margin is also very low. Your speed should be reduced to 6M or lower.

We got all new cabling coming into the house now to replace the older faulty wires. The line is much improved

How are these stats now and what speed can the line support?

relative capacity occupation: 59% 
noise margin upstream: 21.0 db
output power downstream: 19.5 dbm
attenuation upstream: 14.0 db
carrier load: number of bits per symbol(tone)

relative capacity occupation: 66% 
noise margin downstream: 21.0 db
output power upstream: 12.0 dbm
attenuation downstream: 28.5 db
carrier load: number of bits per symbol(tone)

We're on 6mb at the mo but we can increase it now the line is sorted.

jor el

That should be good to about 16Mbps on ADSL2+, or the full 8Mbps on ADSL. The downstream attenuation is the number you want (28.5dB), and plug that into the the website linked. It'll tell you the rest.

Noise margin is also important, in that if it's less than 6dB you can have disconnection issues. At over 20dB, you're doing well. Your old margin of 6.5dB would have been OK, but not great. Could be prone to problems, especially with the high attenuation.

number_1

To_be_confirmed wrote: »

The signal margin on those stats is very substantial. If eircom are saying it can't do more than 5 mbps, you're being limited due to capacity problems at the exchange or else eircom's testing system has simply made a mistake. There was a thread about this before where someone lived 100m from the exchange and wasn't allowed to connect at the full 8 mbps initially. Nag and pursue this, post on the Talk to: Eircom forum if necessary.

Persistant nagging works. Lo and behold they suddenly reckon we're able to get ADSL 2 with estimated speeds of at least 11 Mbps!

brian ireland

Can you have a look at this and tell me what you think. I tried to look at the Kitz site but its all double dutch to me.
My internet is slow, most youtube videos buffer three or four times during playback.
Statistics Downstream Upstream
Line Rate 1376 Kbps 256 Kbps
Noise Margin 6.8 dB 22.0 dB
Line Attenuation 63.0 dB 31.5 dB
Output Power 16.2 dBm 11.4 dBm

Thanks

Simi

Those stats would seem to indicate that you're either living miles from the exchange or something is very wrong with your line.

Disconnect all sky boxes, phones etc. from the the line and reset your dsl modem/router. Then check your stats again to see if they've changed any. If not, that's the best your gonna get sorry.

Gipo3

What about this?
Vodafone day cant get speed increase??

Current(kbps) Down 3072, Up 384;
Max Rate(kbps) Down 7968, Up 1048;
Noise Margin Down 22.3db, Up 24db;
Attenuation Down 27db, Up 47db;
Power Down 19.6dbm, Up 11.9dbm

brian ireland

Simi wrote: »

Those stats would seem to indicate that you're either living miles from the exchange or something is very wrong with your line.

Disconnect all sky boxes, phones etc. from the the line and reset your dsl modem/router. Then check your stats again to see if they've changed any. If not, that's the best your gonna get sorry.

That was a test with everything disconnected but the Mac.

lucernarian

brian ireland wrote: »

That was a test with everything disconnected but the Mac.

Disconnect everything else from the line itself, not the router.

exaisle

I have a faceplate ADSL filter connected and my SNR is 15.4dB. Without the filter connected, it's 11.2dB.

Am I right in thinking that the filter is reducing the noise on the line(ie filtering part of bandwidth out that includes noise, hence a better ratio)?

I'm quite a distance from the exchange so attenuation is 55dB but I'm happy enough with a 2mb connection....as long as its stable.

Solair

Yeah the higher the SNR margin the better.

It's measuring how much louder the signal is compared to the background noise on the line.

* 6bB. or below = Bad and will experience no line synchronisation and frequent disconnections.
* 7dB-10dB. = Fair but does not leave much room for variances in conditions.
* 11dB-20dB. = Good with little or no disconnection problems
* 20dB-28dB. = Excellent
* 29dB. or above = Outstanding (you actually live in the exchange)

BigGeorge

Folks - sorry to drag up an old threat but am having intermitent BB problems & need to eliminate. There has been fibre works going on in the area at the same time

Stats off the router ( zyxel p660hw-t1 v3) are :

DSL Mode: ADSL_G.dmt Speed: 4352 kbps /512 kbps Line Attenuation (Down/Up): 59 dB /31 dB DSL Noise Margin: 6 dB /21 dB
Any suggestions great appreciated

bealtine

BigGeorge wrote: »

Folks - sorry to drag up an old threat but am having intermitent BB problems & need to eliminate. There has been fibre works going on in the area at the same time

Stats off the router ( zyxel p660hw-t1 v3) are :

DSL Mode: ADSL_G.dmt Speed: 4352 kbps /512 kbps Line Attenuation (Down/Up): 59 dB /31 dB DSL Noise Margin: 6 dB /21 dB
Any suggestions great appreciated

Didn't you read the last post before yours?

Your noise margin is 6db meaning disconnects, get onto your supplier

BigGeorge

There is a crackle on the line, I need to have a look at the wiring in the house to make sure that the filters are all in place

bealtine

BigGeorge wrote: »

There is a crackle on the line, I need to have a look at the wiring in the house to make sure that the filters are all in place

disconnect all extensions and all phones except for the main socket and measure from that again, if the noise margin goes up you'll know if the problem is with your extensions inside the house or not

BigGeorge

OK, so

Called Eircom tech support who did a line test & said that the line was only capable of delivering 4MB, not 5, & did a line test. he said he turned the speed down to 4MB & I quickly saw that the noise increased to 7dB - he confirmed this from the line test. Better but not good

So, I took your advice, disconnected absolutely everything & plugged the modem directly into the master socket with everything else cut off. results are now:

Speed: 3872kbps /384 kbps
Line Attenuation (Down/Up): 56 dB /31 dB
DSL Noise Margin: 6 dB /26 dB

At least I now know that the wiring in the house is not at fault. I can see the nearest green cabinet - it is 150m away & the fibre cabinet has just been installed besides the old one. It is a new line installed by Eircom 20 months ago. What do I do next?

bloodyhawk

What in the world, could someone help me on this?
My SNR Margin: Just dropped from 15.0 dB 21.3 dB to 14.0 dB 14.3 dB

bloodyhawk

My Attainable Net Data Rate: Also dropped from 35.974 Mbps 137.364 Mbps to 34.388 Mbps 115.376 Mbps I have no idea whats going on. Does anyone perhaps know why this has happened?


I am on E-fiber 70mb by the way.

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