Question about ADSL line attenuation and SNR

Apr 04, 2007 7 Replies
J
Question about ADSL line attenuation and SNR open original image

de.comm.technik.dsl comp.dcom.xdsl uk.telecom.broadband


Hello,



I have uploaded some screenshots of the results I got after I ran some diagnostics on my 4096/512 ADSL line.



I suspect that too much noise on the line causes re-transmissions which in return lowers my effective downstream speed for TCP traffic. I have measured a downstream speed of approx 2mbit and it is supposed to be around 3.7mbit.



Could you please tell me if I am right?



In my router I see that the line attenuation (downstream) is above 60dB and the SNR is sometimes as low as 3dB.



My ISP keeps on saying that they measure 4096/512 on my line, but my diagnostic tools says otherwise.



I look forward to receiving some comments. Thank you.



Screenshots are here:


3 tests:
formatting link
TraceRoute and TPTest results:
formatting link

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J

Could you elaborate please?

The TPTEST showed that downstream TCP speed is approx 2.5mbit.

What about the attenuation (The DSL central is less than 2km from here)? I think an attenuation of 64dB is quite high when the distance is so short.

And the SNR in the receive direction is sometimes at 3dB....isn't that quite low?

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R

Yes, it is high, when the 2km are correct. Is your installation OK, twisted pair cables, no "flat" ones in your wiring?

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J

How do I check to see if it's "twisted pair cables" ?

And what do you mean by "flat" ?

Thank you.

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H

you can only check your local wires/cables of course, in your house/bulding/appartment whatever, where you have access to... and contact areas, like sockets, self-made-cables/wires and so on..

twisted meaning the wires twisted around each other, and flat meaning non-twisted, so straight wires next to each other...

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E

Telephone extension cables seem to be 'flat'.

Graham

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D

And UDP was 3.6mbit.

I did see some errors on your first link, but without a baseline those reuslts can be almost anything.

Could be many reasosn. Yet where it shows the attenuation, it also shows you are getting the promised bandwidth

Again, one snapshot in time is not telling the whole picture.

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