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

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spacedog

482 posts

Ultimate Geek

#606559 8-Apr-2012 01:20

eXDee: 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.

So if they are on gear other than Telecom that is trying to boost their synch rate by using a lower SNR, I'd expect to see a synch rate better than ~7mbps?

If ~7mbps is the best you can get in a city central location like Ponsonby that is pretty abysmal if you ask me.

I guess all those folks have to wait another decade before the concept of convergence becomes a reality?

Ragnor

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#606560 8-Apr-2012 01:21

spacedog:

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.

Telstraclear have not put any of their own gear in cabinets as far as I know, so if you're on a cabinet your Telstraclear connection will be using Chorus equipment.

Telstraclear does have their gear in >60 exchanges though, so it's likely your friends connection is being served off their own gear.

Ragnor

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#606562 8-Apr-2012 01:30

spacedog:

So if they are on gear other than Telecom that is trying to boost their synch rate by using a lower SNR, I'd expect to see a synch rate better than ~7mbps?

If ~7mbps is the best you can get in a city central location like Ponsonby that is pretty abysmal if you ask me.

I guess all those folks have to wait another decade before the concept of convergence becomes a reality?

28dB line attenuation is roughly the equivalent of ~2km of copper, I would not expect better than ~7-8Mbit line rate at that distance/attenuation.

It would actually be ~600Kbit-1200kBit lower on chorus gear instead of Telstraclear LLU due to the larger buffer/noise margin.

The FTTN "cabinet" program (which cost 1.4 billion!) had a goal to reduce line distances to enable 80% of premises to achieve >10Mbit.

Unfortunately it sounds like your mate is is the 20%....

The French have an expression for this kind of thing: Cest La Vie (Such is life).

spacedog

482 posts

Ultimate Geek

#606563 8-Apr-2012 01:35

Ragnor:
spacedog:

So if they are on gear other than Telecom that is trying to boost their synch rate by using a lower SNR, I'd expect to see a synch rate better than ~7mbps?

If ~7mbps is the best you can get in a city central location like Ponsonby that is pretty abysmal if you ask me.

I guess all those folks have to wait another decade before the concept of convergence becomes a reality?

28dB line attenuation is roughly the equivalent of ~2km of copper, I would not expect better than ~7-8Mbit line rate at that distance/attenuation.

It would actually be ~600Kbit-1200kBit lower on chorus gear instead of Telstraclear LLU due to the larger buffer/noise margin.

The FTTN "cabinet" program (which cost 1.4 billion!) had a goal to reduce line distances to enable 80% of premises to achieve >10Mbit.

Unfortunately it sounds like your mate is is the 20%....

The French have an expression for this kind of thing: Cest La Vie (Such is life).

Once again, sir, you prove to be supremely helpful and worthy of your 'uber geek' status.

Spyware

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#606614 8-Apr-2012 10:38

28 dB attenuation is most likely in a 10 Mbps zone. I get 11577 kbps sync @ 33 dB with Telecom.

Line Attenuation:        33.0 dB                  6.8 dB
Signal Attenuation:      33.0 dB                 16.9 dB
Noise Margin:            11.5 dB                 11.5 dB
Attainable Rate:        13136 kbits/s            894 kbits/s

                  DS Channel1     DS Channel0   US Channel1       US Channel0
Speed (kbps):             0            11577             0               945

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Ragnor

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#606837 8-Apr-2012 21:24

You're quite right 28dB attenuation should achieve >10Mbit it should be around 14-16Mbit... must have been sleepy when I made my earlier post.

I suspect you'll have to be persistent with the help desk, if you can convince them to send a tech to investigate the exchange end of the connection, maybe switch to a different port or re-terminte the line to rule out a bad line card or dodgy termination... same at the house end that could solve the problem.

Otherwise if it's something along the line it's unlikely they will be willing to do much about it.

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