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[pooclah]

Hi all

Posting this here because I think it shows the effect of crosstalk on a connection. 

This evening in we had a large electrical storm that knocked  out our power supply so  I took the opportunity to connect the modem to a power pack that I’d bought a few years ago to jump start cars.

I collected stats from during the power outage and when I reconnected a few minutes after the power came back on.

Below shows that I have lost 11 dB of SRNM and 46 Mbps of downstream attainable due to crosstalk.

During power outage

Code: [Select]

    VDSL Training Status:   Showtime
                    Mode:   VDSL2 Annex B
            VDSL Profile:   Profile 17a
                G.Vector:   Disable
            Traffic Type:   PTM Mode
             Link Uptime:   0 day: 0 hour: 0 minute
====================================================================================
       VDSL Port Details       Upstream         Downstream
               Line Rate:     20.063 Mbps       79.998 Mbps
    Actual Net Data Rate:     19.999 Mbps       79.999 Mbps
          Trellis Coding:         ON                ON
              SNR Margin:       23.2 dB           17.4 dB
            Actual Delay:          0 ms              0 ms
          Transmit Power:      - 0.7 dBm          12.7 dBm
           Receive Power:      -15.9 dBm           1.0 dBm
              Actual INP:        0.0 symbols      48.0 symbols
       Total Attenuation:        0.0 dB          11.7 dB
Attainable Net Data Rate:     38.874 Mbps      121.985 Mbps
====================================================================================
  VDSL Band Status        U0      U1      U2      U3      U4      D1      D2      D3
  Line Attenuation(dB): 3.3 12.9 19.8   N/A   N/A 7.1 15.9 25.3
Signal Attenuation(dB): 3.3 12.1 19.0   N/A   N/A 8.4 15.8 25.3
        SNR Margin(dB): 24.8 23.0 23.2   N/A   N/A 17.5 17.4 17.4
         TX Power(dBm): -14.9 -30.0 -0.8   N/A   N/A 8.8 7.7 7.1
====================================================================================

            VDSL Counters

           Downstream        Upstream
Since Link time = 51 sec
FEC: 1303 71
CRC: 0 10
ES: 0 1
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 15 minutes time = 1 min 27 sec
FEC: 1303 71
CRC: 0 10
ES: 0 1
SES: 0 0
UAS: 35 35
LOS: 0 0
LOF: 0 0
LOM: 0 0
Previous 15 minutes time = 0 sec
FEC: 0 0
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 1 day time = 1 min 27 sec
FEC: 1303 71
CRC: 0 10
ES: 0 1
SES: 0 0
UAS: 35 35
LOS: 0 0
LOF: 0 0
LOM: 0 0
Previous 1 day time = 0 sec
FEC: 0 0
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Total time = 1 min 27 sec
FEC: 1303 71
CRC: 0 10
ES: 0 1
SES: 0 0
UAS: 35 35
LOS: 0 0
LOF: 0 0
LOM: 0 0
====================================================================================
And after

Code: [Select]

    VDSL Training Status:   Showtime
                    Mode:   VDSL2 Annex B
            VDSL Profile:   Profile 17a
                G.Vector:   Disable
            Traffic Type:   PTM Mode
             Link Uptime:   0 day: 0 hour: 3 minutes
====================================================================================
       VDSL Port Details       Upstream         Downstream
               Line Rate:     20.063 Mbps       75.680 Mbps
    Actual Net Data Rate:     19.999 Mbps       75.681 Mbps
          Trellis Coding:         ON                ON
              SNR Margin:       15.0 dB            6.0 dB
            Actual Delay:          0 ms              0 ms
          Transmit Power:      - 0.6 dBm          12.6 dBm
           Receive Power:      -15.9 dBm           0.9 dBm
              Actual INP:        0.0 symbols      48.0 symbols
       Total Attenuation:        0.0 dB          11.8 dB
Attainable Net Data Rate:     25.210 Mbps       75.199 Mbps
====================================================================================
  VDSL Band Status        U0      U1      U2      U3      U4      D1      D2      D3
  Line Attenuation(dB): 3.3 12.9 19.7   N/A   N/A 7.1 15.9 25.1
Signal Attenuation(dB): 3.3 12.0 18.9   N/A   N/A 8.4 15.7 25.1
        SNR Margin(dB): 14.9 15.3 14.9   N/A   N/A 5.1 6.4 6.4
         TX Power(dBm): -15.1 -30.2 -0.8   N/A   N/A 8.7 7.7 7.1
====================================================================================

            VDSL Counters

           Downstream        Upstream
Since Link time = 3 min 7 sec
FEC: 26523 1925
CRC: 55 225
ES: 12 23
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 15 minutes time = 3 min 34 sec
FEC: 26523 1925
CRC: 55 225
ES: 12 23
SES: 0 0
UAS: 27 27
LOS: 0 0
LOF: 0 0
LOM: 0 0
Previous 15 minutes time = 0 sec
FEC: 0 0
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 1 day time = 3 min 34 sec
FEC: 26523 1925
CRC: 55 225
ES: 12 23
SES: 0 0
UAS: 27 27
LOS: 0 0
LOF: 0 0
LOM: 0 0
Previous 1 day time = 0 sec
FEC: 0 0
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Total time = 3 min 34 sec
FEC: 26523 1925
CRC: 55 225
ES: 12 23
SES: 0 0
UAS: 27 27
LOS: 0 0
LOF: 0 0
LOM: 0 0
Edited to correct my sums.

[burakkucat]

Interesting.

I've taken your two data sets and displayed the difference between them, ignoring the "VDSL Counters" sections. The "before" data is indicated by "<" at the start of a line. The "after" data is indicated by ">" at the start of a line.

I wonder if the values shown can be manipulated in some way to . . . hmm . . . 

Code: [Select]

<                Line Rate:     20.063 Mbps       79.998 Mbps
<     Actual Net Data Rate:     19.999 Mbps       79.999 Mbps
---
>                Line Rate:     20.063 Mbps       75.680 Mbps
>     Actual Net Data Rate:     19.999 Mbps       75.681 Mbps

<               SNR Margin:       23.2 dB           17.4 dB
---
>               SNR Margin:       15.0 dB            6.0 dB

<           Transmit Power:      - 0.7 dBm          12.7 dBm
<            Receive Power:      -15.9 dBm           1.0 dBm
---
>           Transmit Power:      - 0.6 dBm          12.6 dBm
>            Receive Power:      -15.9 dBm           0.9 dBm

<        Total Attenuation:        0.0 dB          11.7 dB
< Attainable Net Data Rate:     38.874 Mbps      121.985 Mbps
---
>        Total Attenuation:        0.0 dB          11.8 dB
> Attainable Net Data Rate:     25.210 Mbps       75.199 Mbps

<   Line Attenuation(dB):       3.3     12.9    19.8      N/A     N/A   7.1     15.9    25.3   
< Signal Attenuation(dB):       3.3     12.1    19.0      N/A     N/A   8.4     15.8    25.3   
<         SNR Margin(dB):       24.8    23.0    23.2      N/A     N/A   17.5    17.4    17.4   
<          TX Power(dBm):       -14.9   -30.0   -0.8      N/A     N/A   8.8     7.7     7.1     
---
>   Line Attenuation(dB):       3.3     12.9    19.7      N/A     N/A   7.1     15.9    25.1   
> Signal Attenuation(dB):       3.3     12.0    18.9      N/A     N/A   8.4     15.7    25.1   
>         SNR Margin(dB):       14.9    15.3    14.9      N/A     N/A   5.1     6.4     6.4     
>          TX Power(dBm):       -15.1   -30.2   -0.8      N/A     N/A   8.7     7.7     7.1



[WWWombat]

I make the drop in SNRM to be 11.4dB, plus the drop in actual speed of 4Mbps.

IIRC, my rule-of-thumb is that 3dB is worth around 10-11Mbps for lines short enough to use the full spectrum. That would fit roughly with the overall drop in attainable.

[burakkucat]

I make the drop in SNRM to be 11.4dB, plus the drop in actual speed of 4Mbps.

IIRC, my rule-of-thumb is that 3dB is worth around 10-11Mbps for lines short enough to use the full spectrum. That would fit roughly with the overall drop in attainable.

Ah, I see. That is what I could not quite rationalise and so tailed off with a . . . hmm . . .

There are two other lines, one item, in the difference that intrigue me and they are the Attainable Net Data Rate lines.

[pooclah]

I make the drop in SNRM to be 11.4dB

Sorry about that, I made the post in a bit of a rush as I had a grandchild tugging my sleeve to go and watch the storm with them and must have read the wrong line.

[NewtronStar]

And it's great another user making use of a car jump starter pack it works well on modems but don't know how long the power would last on those packs I used it for 4-5 five hours and it was still showing 12.3 volts.

The Attainable DS & US show a heck of a difference have enjoyed seeing your before & after stats thanks.

[GigabitEthernet]

Huawei cabinet? BDUK? You might get vectoring, perhaps.

[pooclah]

@NS
The pack has been sat in a cupboard for months so I was surprised when it still worked, but it was good to see ‘clean’ vs ‘dirty’ stats.

@GigabitEthernet
Yes
I'm not 100% sure but I don't think so
Possibly - who knows