Need advice on DSL attenuation and Signal-to-Noise Ration Margin on DSL connection

Forums › New Zealand Broadband › Need advice on DSL attenuation and Signal-to-Noise Ration Margin on DSL connection

spacedog

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#100263 6-Apr-2012 11:04

Hi,

I have a friend who is connected to the main Ponsonby exchange and has been having DSL issues.

In order to help them test, I brought over my modem which reports a 0db attentuation and 12db SNR margin (I'm located about 100m from my cabinet in Parnell so my attenuation is super low).

We disconnected the the lines going into their house and connected both his/my DSL modem directly to the line that goes straight into the network thus eliminating any possibility of issues with inside wiring.

His attenuation was 28.5db

His SNR was 8db

I was very surprised to see his attenuation so high. As he is in Central Ponsonby I thought the attenuation would be quite a bit lower.

I also feel like that SNR is not looking too good at all.

I have ADSL out at nearly the end of the network at my business on Waiheke. Our Attenuation there is 57db and our SNR margin is still 12db.

I have suggested they file a fault because the line to me doesn't look too pretty given their location. Their ISP told them that those numbers are just fine and there is nothing to worry about.

I noticed that his, and my, modem is slow to synch on his connection and he cannot attain anything above 7-8mpbs and he still experiences issues with disconnects.

I would have thought most people connected to the main ponsonby exchange would be getting better speeds and reliability? I get 20mbps line synchs and 17mbps actual throughput.

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Biddle Corp

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#606058 6-Apr-2012 11:22

Who is the ISP, is it a ULL or wholesale connection, and is the person in a 10Mbps or VDSl2 zone? You can tell this by looking at the Chorus SAT.

spacedog

482 posts

Ultimate Geek

#606068 6-Apr-2012 11:56

They are with Telstraclear and have phone and internet with them.

According to the telecom wholesale map and their address it appears they are in a VDSL2 zone. If you are curious to know the street, I'll PM it to you.

spacedog

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#606324 7-Apr-2012 09:22

any other comments on this thread?

sbiddle

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#606330 7-Apr-2012 09:41

You'll need to privide more information if you want more help. Without anybody on here knowing more details including an address there is unfortunately nothing anybody could do to help you.

Is the person definately connected to the exchange or are they connected to a cabinet? The Chorus SAT will tell you this. Are they on a ULL connection or wholesale? TelstraClear can tell you this? What sort of sync rate should you be getting at the door? A TCL (or any other ISP) doing a Chorus prequal will be able to tell you this.

And lastly did you definately eliminate all wiring in your testing? You could also read my blog on ULL and mid span injection issues which may be of some help, but I'm not aware of TCL hooking up customers to ULL gear who were going to be cabinetised.

spacedog

482 posts

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#606335 7-Apr-2012 10:04

sbiddle: You'll need to privide more information if you want more help. Without anybody on here knowing more details including an address there is unfortunately nothing anybody could do to help you.

Is the person definately connected to the exchange or are they connected to a cabinet? The Chorus SAT will tell you this. Are they on a ULL connection or wholesale? TelstraClear can tell you this? What sort of sync rate should you be getting at the door? A TCL (or any other ISP) doing a Chorus prequal will be able to tell you this.

And lastly did you definately eliminate all wiring in your testing? You could also read my blog on ULL and mid span injection issues which may be of some help, but I'm not aware of TCL hooking up customers to ULL gear who were going to be cabinetised.

Sorry what is the "Chorus SAT"?

I did definitively eliminate all wiring issues before posting here.

The address is between 50-60 Norfolk street.

As for being connected to the exchange or a cabinet, I can't really tell for sure other than using the telecom wholesale map tool. Using that tool with that address it appears to be going to the exchange? But if you look at it using the VDSL it looks like it might be to a cabinet??? Really not sure about that...

What about the SNR margin they are getting. Is there any scenario you mentioned above where an SNR of 8db is perfectly fine? That seemed to be low to me and suggest a possibly bad/dirty copper loop?

Zeon

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#606342 7-Apr-2012 10:29

Looks like he is within the main exchange area and not serviced by a cabinet. However he is quite close as he is also within the VDSL area so should be getting far better signal than that. Could you try the modem directly at the mushroom (the Telecom thing sticking up outside the gate?).

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Zeon

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#606343 7-Apr-2012 10:29

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spacedog

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#606424 7-Apr-2012 16:13

Already connected him straight to the Telecom plinth. That was how I isolated him from his internal wiring. I used to do lots of network admin stuff and I still have most of my tools. I jacked his modem straight in using my own custom made high quality solid core copper wiring leads.

The attenuation at 28db seemed kind of high to me as well, but I suppose he could be far enough away to justify that high of an attenuation (even though I found that surprising). It was the poor SNR that really caught my attention.

eXDee

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#606428 7-Apr-2012 16:34

Telecom typically uses 12db for SNR on all their wholesale equipment.

Im unsure of Telstraclears LLU status. Do they have their own equipment or are they using Vodafone or Orcons? Both the latter two use lower SNR to boost sync rates.

coffeebaron

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#606522 7-Apr-2012 21:57

TelstraClear have a lot of ULL around Auckland, so my guess is this would be their gear.

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Jaxson

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#606532 7-Apr-2012 22:32

When you 'jacked him in', did you disconnect the wiring heading off to his house?
You'd still get reflections from the internal wiring if you didn't, or didn't use a master filter/splitter.

Ragnor

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#606554 8-Apr-2012 01:06

spacedog:

What about the SNR margin they are getting. Is there any scenario you mentioned above where an SNR of 8db is perfectly fine? That seemed to be low to me and suggest a possibly bad/dirty copper loop?

FYI

Signal to Noise Ratio is NOT the same thing as Noise Margin

Signal to Noise Ratio (SNR):
This is the ratio between clean / clear (good) signal to background Noise (Bad), higher = better

Signal to Noise Margin (NM or SNM):
This is a buffer that allows for stability, lower = higher line rates & higher = lower line rates (but better connections stability)

Some modems label these poorly in their status pages which is the cause of a lot of confusion!

Noise margin is a target set on the line profile for the port in the ISAM/DSLAM:

12dB noise margin is the default on Chorus equipment
6dB is used by Orcon on their LLU gear and common overseass
9dB is used by Telstraclear on their LLU gear

Don't think noise margin is the problem.

spacedog

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#606555 8-Apr-2012 01:12

Jaxson: When you 'jacked him in', did you disconnect the wiring heading off to his house?
You'd still get reflections from the internal wiring if you didn't, or didn't use a master filter/splitter.

Yup. Disconnected everything.

I have to say, I really miss the USA when it comes to the networks here. So much easier...in the USA they terminate the network point leading into a property with an RJ45 block. If you want to isolate you go to your box, unplug the RJ45, it isolates your house, and you just plug-in. Makes life so much easier. I wonder when NZ will figure this one out.....they've only been doing that over there since the late 90's....

spacedog

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#606557 8-Apr-2012 01:16

Ragnor:
spacedog:

What about the SNR margin they are getting. Is there any scenario you mentioned above where an SNR of 8db is perfectly fine? That seemed to be low to me and suggest a possibly bad/dirty copper loop?

FYI

Signal to Noise Ratio is NOT the same thing as Noise Margin

Signal to Noise Ratio (SNR)
This is the ratio between clean / clear (good) signal to background Noise (Bad)

Signal to Noise Margin (NM or SNM)
This is a buffer that allows for stability

Some modems label these poorly in their status pages which is confusing.

12dB noise margin is the default on Chorus equipment
6dB is used by Orcon on their LLU gear and common overseass

If I remember rightly 9dB is used by Telstraclear on their LLU gear

Basically I think ~8dB noise margin is probably fine on Telstraclear LLU.

Ragnor..... +rep for a really useful post!

I was aware of the SNR margin vs. SNR an already accounted for that. I was speaking in terms of margin. It seems that is the prevailing stat that modern modems report.

Personally, I'm on telstra, but honestly I don't know if I am on Chorus or Telstra LLU. I get a SNR *margin* of 12db an 0db attenuation, but I got cabinetized just up the corner from my house.

Ragnor

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#606558 8-Apr-2012 01:18

spacedog:

I have to say, I really miss the USA when it comes to the networks here. So much easier...in the USA they terminate the network point leading into a property with an RJ45 block. If you want to isolate you go to your box, unplug the RJ45, it isolates your house, and you just plug-in. Makes life so much easier. I wonder when NZ will figure this one out.....they've only been doing that over there since the late 90's....

NZ builders and home owners will cry poverty at being forced to do things properly.

The TCF has pretty good premises wiring guidelines, but they are not mandatory (yet).

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