Kitz Forum

Broadband Related => ADSL Issues => Topic started by: konrado5 on October 18, 2017, 02:14:36 PM

Title: Very low noise on tones 415-468
Post by: konrado5 on October 18, 2017, 02:14:36 PM: Is it real that noise is so low? I know that other people don't use these frequiences (no crosstalk) but it seems the noise is still incredibly low.

Best regards
konrado5
Title: Re: Very low noise on tones 415-468
Post by: burakkucat on October 18, 2017, 05:29:58 PM: It is generally accepted that a good noise floor, for an xDSL circuit, would be around -140 dBm/Hz per sub-carrier or quieter.

If only that level was maintained across the entire bandwidth . . .
Title: Re: Very low noise on tones 415-468
Post by: konrado5 on October 19, 2017, 05:04:31 PM: What do you think about this huge difference between tones 415-468 and remaining tones?
Title: Re: Very low noise on tones 415-468
Post by: JGO on October 19, 2017, 07:06:03 PM: "What do you think about this huge difference between tones 415-468 and remaining tones ? "

Frequency Allocations - they are not made with IT in mind !.
Title: Re: Very low noise on tones 415-468
Post by: konrado5 on October 19, 2017, 07:22:24 PM: Quote from: JGO on October 19, 2017, 07:06:03 PM
"What do you think about this huge difference between tones 415-468 and remaining tones ? "

Frequency Allocations - they are not made with IT in mind !.
I don't understand. I know that I am only user using frequiences 1.8-2.0 Mhz. My ISP disabled ham band mask for me.
Title: Re: Very low noise on tones 415-468
Post by: burakkucat on October 19, 2017, 09:45:43 PM: Quote from: konrado5 on October 19, 2017, 05:04:31 PM
What do you think about this huge difference between tones 415-468 and remaining tones?

That is something I am unable to explain. Perhaps you will discover something that fits your observations.
Title: Re: Very low noise on tones 415-468
Post by: konrado5 on October 19, 2017, 10:31:37 PM: Quote from: burakkucat on October 19, 2017, 09:45:43 PM
That is something I am unable to explain. Perhaps you will discover something that fits your observations.
Crosstalk? Other people have HAM band masks.
Title: Re: Very low noise on tones 415-468
Post by: burakkucat on October 19, 2017, 10:52:32 PM: Quote from: konrado5 on October 19, 2017, 10:31:37 PM
Crosstalk? Other people have HAM band masks.

Well, yes, that is the simplest explanation that fits the observation.
Title: Re: Very low noise on tones 415-468
Post by: kitz on October 20, 2017, 10:32:52 PM: Crosstalk - or rather lack of over those tones.

Your bit load graph would be interesting too.
Title: Re: Very low noise on tones 415-468
Post by: burakkucat on October 20, 2017, 11:05:06 PM: Quote from: kitz on October 20, 2017, 10:32:52 PM
Your bit load graph would be interesting too.

Oh, yes. That, too, would be interesting.

Actually the SNR v sub-carrier plot gives quite a good idea of the "excess" SNR that is available across that 200 kHz band. By eye, we can judge where a flattened sinusoid that links the two frequencies would lie. Everything above that would be the bonus "excess" due to the lack of other users. Whether the "excess" could then be mapped across the entire bandwidth, to give an estimate for a "one user system", I'm not too sure.
Title: Re: Very low noise on tones 415-468
Post by: konrado5 on October 22, 2017, 06:28:36 PM: This is my bit-loading on SNR margin 2.7 dB.