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FTTC - attenuation - what should it be?

millsdon
Grafter
Posts: 47
Registered: 01-04-2012

FTTC - attenuation - what should it be?

What sort of attenuation should I expect? On ADSL, you could go to smaknows etc and get a rough distance from the exchange. You could then look at a graph and workout roughly what your attenuation should be which would then give you an idea if the line is good/bad. This gave you an idea to check your internal wiring etc to see if you could decrease it.
Now I know that FTTC now goes on the distance to the cabinet (rather than the exchange) so if I said i appeared to be 300m from the cabinet, what my my attenuation roughly be?
When I run xdslcmd info --pbParams (below), what does DI, D2 & D3 mean under line & signal attenuation.
# xdslcmd info --pbParams
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Max:    Upstream rate = 11920 Kbps, Downstream rate = 53628 Kbps
Path:  0, Upstream rate = 11864 Kbps, Downstream rate = 52930 Kbps
Discovery Phase (Initial) Band Plan
US: (0,95) (868,1207) (1972,2783)
DS: (32,859) (1216,1963) (2792,3959)
Medley Phase (Final) Band Plan
US: (0,95) (868,1207) (1972,2783)
DS: (32,859) (1216,1963) (2792,3959)
      VDSL Port Details      Upstream        Downstream
Attainable Net Data Rate:      11920 kbps        53628 kbps
Actual Aggregate Tx Power:        6.8 dBm          12.1 dBm
============================================================================
  VDSL Band Status        U0      U1      U2      U3      D1      D2      D3
  Line Attenuation(dB):  5.8    30.8    46.4    N/A    14.5    38.3    59.5
Signal Attenuation(dB):  9.5    30.0    46.1    N/A    14.5    38.3    59.5
        SNR Margin(dB):  6.3    6.4    6.4      N/A    6.2    6.2    6.4
        TX Power(dBm): -4.2    -11.6    6.3      N/A    9.0    7.9    3.5
2 REPLIES
Community Veteran
Posts: 6,307
Thanks: 86
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Registered: 08-01-2008

Re: FTTC - attenuation - what should it be?

U0, U1, U2, D1, D2 & D3 are all different upstream and downstream frequency bands, each has a different attenuation because of the different frequencies.
Further up the stats you'll see 'Band Plan' and different tone number ranges for US (upstream) and DS (downstream), these are the bands that each attenuation figure relates to.
I don't really know the difference between 'line' and 'signal' attenuation but, except for the lowest frequency bands, they're much the same anyway.
The higher bands have quite high attenuation because the frequencies used are much higher than on ADSL.
Now, I could be wrong but I think your stats indicate a bit longer than 300m line to the cabinet.
Call me 'w23'
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millsdon
Grafter
Posts: 47
Registered: 01-04-2012

Re: FTTC - attenuation - what should it be?

Yes, I would think that too. The nearest cabinet to me is about 100m to the west of me and then 100m north of that point. So I think it can mean 3 things:
1. I'm connected to that cabinet and the cabling takes a vastly different route to what you would think.
2. I'm not connected to that cabinet and the one I'm connected to is further away.
3. There's a fault somewhere as the line to the house is less than two years old and my house wiring is 100%