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Thread: Does noise margin change depending on speed profile?

Started 2 months, 1 week ago by Xcellor
Yesterday I was on the 7.6 speed profile with the following results: / # adsl info Current Training Status : Showtime Current trained adsl mode : G.Dmt Current trained adsl path : Interleaved Downstream Bit Rate : 7616000 bps Downstream Noise Margin : 15.0 dB Downstream Attenuation : 8.0 dB Upstream Bit Rate : 672000 bps Upstream...
Site: boards.ie  boards.ie - site profile
Forum: Broadband  Broadband - forum profile
Total authors: 7 authors
Total thread posts: 13 posts
Thread activity: no new posts during last week
Domain info for: boards.ie

Other posts in this thread:

DECEiFER replied 2 months ago
Quote: Originally Posted by Xcellor Yesterday I was on the 7.6 speed profile with the following results: / # adsl info Current Training Status : Showtime Current trained adsl mode : G.Dmt Current trained adsl path : Interleaved Downstream Bit Rate : 7616000 bps Downstream Noise Margin : 15.0 dB ...

dub45 replied 2 months ago
Quote: Originally Posted by Xcellor Yesterday I was on the 7.6 speed profile with the following results: / # adsl info Current Training Status : Showtime Current trained adsl mode : G.Dmt Current trained adsl path : Interleaved Downstream Bit Rate : 7616000 bps Downstream Noise Margin : 15.0 dB...

DECEiFER replied 2 months ago
Quote: Originally Posted by dub45 http://www.kitz.co.uk/adsl/lowSNR.htm Quote: Traditional Fixed 512/1Mb/2Mb For each upgrade between the speeds you can expect to lose on average 6dB. Therefore if you upgraded from 512kbps to 2Mbps then your SNR Margin is likely to have dropped in the region of 12dB....

dub45 replied 2 months ago
Quote: Originally Posted by DECEiFER Exactly! Therefore his line is capable of the full 7.6Mb sync, and downgrading it is just a load of bulls**t, no matter what excuse they pull out for it. Best of luck with it, Xcellor. Yes in theory but don't forget his internal wiring could be in a mess

DECEiFER replied 2 months ago
Quote: Originally Posted by dub45 Yes in theory but don't forget his internal wiring could be in a mess True, but surely that would deteriorate the signal and up the noise?

dub45 replied 2 months ago
The op has not told us exactly what the issue was that lead to UTV changing his profile. The attenuation figure would suggest that he is living very close to the exchange. The SNR figure would suggest that give that proximity to the exchange there must be an issue of line quality somewhere. That problem may be contributing to the already low snr figure.

Grommet replied 2 months ago
Quote: Originally Posted by DECEiFER Exactly! Therefore his line is capable of the full 7.6Mb sync, and downgrading it is just a load of bulls**t, no matter what excuse they pull out for it. Modems are normally set to "Rate Adaptive" mode by the operator, which means that the modem will be set to a maximum speed (...

Xcellor replied 2 months ago
Quote: Originally Posted by Grommet Modems are normally set to "Rate Adaptive" mode by the operator, which means that the modem will be set to a maximum speed (probably 7Mbps in this case) but can re-synch at lower speeds if noise is introduced onto the line. It sounds as if there is some RF interference somewhere that is causing the ...

Karsini replied 2 months ago
Quote: Originally Posted by Grommet Modems are normally set to "Rate Adaptive" mode by the operator, which means that the modem will be set to a maximum speed (probably 7Mbps in this case) but can re-synch at lower speeds if noise is introduced onto the line. It sounds as if there is some RF interference somewhere that is causing the ...

Grommet replied 2 months ago
Quote: Originally Posted by Karsini I've seen some people's modems constantly sync at 6144/512 or 5120/512 so this would make me think that there are multiple profiles. I'd just find it highly unlikely that a modem would, on its own accord, sync at exactly 5 or 6 megs. It depends on the modem manufacturer. The ...

 

Top contributing authors

Name
Posts
DECEiFER
3
user's latest post:
Does noise margin change...
Published (2009-10-01 00:11:00)
Quote: Originally Posted by dub45 Yes in theory but don't forget his internal wiring could be in a mess True, but surely that would deteriorate the signal and up the noise?
dub45
3
user's latest post:
Does noise margin change...
Published (2009-10-01 00:17:00)
The op has not told us exactly what the issue was that lead to UTV changing his profile. The attenuation figure would suggest that he is living very close to the exchange. The SNR figure would suggest that give that proximity to the exchange there must be an issue of line quality somewhere. That problem may be contributing to the already low snr figure.
Xcellor
2
user's latest post:
Does noise margin change...
Published (2009-10-01 10:13:00)
Quote: Originally Posted by Grommet Modems are normally set to "Rate Adaptive" mode by the operator, which means that the modem will be set to a maximum speed (probably 7Mbps in this case) but can re-synch at lower speeds if noise is introduced onto the line. It sounds as if there is some RF interference somewhere that is causing the op's line to degrade on occasion. I doubt if UTV (or eircom) have actually provisioned...
Grommet
2
user's latest post:
Does noise margin change...
Published (2009-10-01 23:15:00)
Quote: Originally Posted by Karsini I've seen some people's modems constantly sync at 6144/512 or 5120/512 so this would make me think that there are multiple profiles. I'd just find it highly unlikely that a modem would, on its own accord, sync at exactly 5 or 6 megs. It depends on the modem manufacturer. The various synch speeds are defined within the modem firmware. The max profile is set by the operator, the modem then...
To_be_confirmed
1
user's latest post:
Does noise margin change...
Published (2009-10-02 13:31:00)
Crosstalk would do nothing except lower signal margin. Aka it's not noticeable until the signal margin spikes down towards 0. The fact that the speed issues only appear in the evenings, and stop by 1am, means that contention/backhaul issues in some form or other are the problem. The line is grand. Btw, I've found the signal margin changes unpredictably when sync rate is changed. As good as the Kitz website is, the "rule of...
Karsini
1
user's latest post:
Does noise margin change...
Published (2009-10-01 22:28:00)
Quote: Originally Posted by Grommet Modems are normally set to "Rate Adaptive" mode by the operator, which means that the modem will be set to a maximum speed (probably 7Mbps in this case) but can re-synch at lower speeds if noise is introduced onto the line. It sounds as if there is some RF interference somewhere that is causing the op's line to degrade on occasion. I doubt if UTV (or eircom) have actually provisioned...
Sponge Bob
1
user's latest post:
Does noise margin change...
Published (2009-10-01 23:56:00)
Quote: Originally Posted by Grommet EDIT: come to think of it - if your exchange was only enabled in June then there is no way the link between the DSLAM and the BRAS would be anywhere near full already. So almost certainly not congestion there. Absolutely . Another possibility and one that would be have been masked by the congestion upstream would be 'Crosstalk' . In other words too many people out your direction from the exchange...

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