SNRM & Error levels :: Fibre Broadband

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RobertoS
(sensei) Fri 09-Dec-11 10:07:20

Re: SNRM & Error levels

[re: BatBoy] [link to this post]

In reply to a post by BatBoy:
It's all explained here http://www.robertos.me.uk/html/noise_margin-snr-snrm...

Exactly

. Assuming you accept that explanation you inevitably have to accept that your initial statement was junk.

My broadband basic info/help site - www.robertos.me.uk
My domains,website and mail hosting - Tsohost. Internet connection - IDNet Home Starter Fibre. Live BQM.

"Where talent is a dwarf, self-esteem is a giant." - Jean-Antoine Petit-Senn.

Sadoldman
(moderator) Fri 09-Dec-11 10:41:05

Re: SNRM & Error levels

[re: BatBoy] [link to this post]

I see this as you trolling and little else.

Not sure why you feel the need to attention seek like this, desist this constant belligerent approach or you will get my attention.

To others...if you see it as trolling...ignore.

Sadoldman

Just a tad sad..a wee bit old... wink

[email protected]

The author of the above post is a thinkbroadband moderator but it does not constitute an official statement on behalf of thinkbroadband.

BatBoy
(legend) Fri 09-Dec-11 19:22:40

Re: SNRM & Error levels

[re: RobertoS] [link to this post]

In reply to a post by RobertoS:
In reply to a post by BatBoy:
It's all explained here http://www.robertos.me.uk/html/noise_margin-snr-snrm...
Exactly . Assuming you accept that explanation you inevitably have to accept that your initial statement was junk.

No, not at all. I see it as spot-on.

_{______________________________________________________________________________. __________________}

BatBoy
(legend) Fri 09-Dec-11 19:22:45

Re: SNRM & Error levels

[re: Sadoldman] [link to this post]

In reply to a post by Sadoldman:
I see this as you trolling and little else.

Not sure why you feel the need to attention seek like this, desist this constant belligerent approach or you will get my attention.

To others...if you see it as trolling...ignore.

Wrong. This is a troll http://forums.thinkbroadband.com/fibre/t/4072351-re-...

_{______________________________________________________________________________. __________________}

BatBoy
(legend) Fri 09-Dec-11 19:22:53

Re: SNRM & Error levels

[re: XRaySpeX] [link to this post]

In reply to a post by XRaySpeX:
What high signal?

The signal which is the "S" in SNR. It is high due to the profile change.

_{______________________________________________________________________________. __________________}

woodyblade
(newbie) Fri 09-Dec-11 19:27:09

Re: SNRM & Error levels

[re: Bald_Eagle1] [link to this post]

Managed to remember that some results wanted posting, this is after 68 hours uptime, looks like I've had more HEC errors than what I've seen before but less FEC errors.

Works out at 7/1 FEC errors per hour and 20/0 HEC errors per hour

Text
1 23 45	Downstream Upstream Line rate (kbit/s) 39998 10000CRC errors 0 0 FEC errors 471 94 HEC errors 1338 0

These are the current SNRM values below, but these can vary between 14.5/22 - 17/23, meaning attainable rates of 68/25mbps - 78/27mbps.
I've even seen/caught the SNRM as high as 19.5/24 before which meant something around 88/29mbps as attainable rates.

Shame the line can't sustain these speeds constantly, or even that 78/27mbps one, mainly stays around that 68/25 range. Though I can't complain when the speed before on ADSL was 3/0.8mbps.

Text

xdslcmd: ADSL driver and PHY status
Status: ShowtimeRetrain Reason: 0
Max:    Upstream rate = 26974 Kbps, Downstream rate = 78428 KbpsPath:   0, Upstream rate = 10000 Kbps, Downstream rate = 39998 Kbps
 Discovery Phase (Initial) Band Plan
US: (0,95) (868,1207) (1972,2783)DS: (32,859) (1216,1963) (2792,3939)
Medley Phase (Final) Band PlanUS: (0,95) (868,1207) (1972,2783)
DS: (32,859) (1216,1963) (2792,3939)       VDSL Port Details       Upstream        Downstream
Attainable Net Data Rate:      26974 kbps         78428 kbpsActual Aggregate Tx Power:        6.9 dBm          13.4 dBm
============================================================================  VDSL Band Status        U0      U1      U2      U3      D1      D2      D3
  Line Attenuation(dB):  4.6     21.9    31.4     N/A    11.7    27.0    41.1Signal Attenuation(dB):  8.1     21.4    30.2     N/A    11.7    27.0    41.1
        SNR Margin(dB):  22.4    21.9    22.8     N/A    17.5    17.8    17.6         TX Power(dBm): -4.1    -24.8    6.4      N/A    10.8    7.6     6.0

XRaySpeX
(eat-sleep-adslguide) Fri 09-Dec-11 19:58:42

Re: SNRM & Error levels

[re: BatBoy] [link to this post]

In reply to a post by BatBoy:
In reply to a post by XRaySpeX:
What high signal?
The signal which is the "S" in SNR. It is high due to the profile change.

What profile change? If you mean the one mentioned by bhawkes, it was made the day after I made & withdrew my comment about the high SNRM when you had no inkling of any profile change.

It's easy to be "wise" after the event, particularly when you are talking out of your blowhole.

1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 19 Meg WBC

BatBoy
(legend) Fri 09-Dec-11 20:11:29

Re: SNRM & Error levels

[re: XRaySpeX] [link to this post]

In reply to a post by XRaySpeX:
In reply to a post by BatBoy:
In reply to a post by XRaySpeX:
What high signal?
The signal which is the "S" in SNR. It is high due to the profile change.
What profile change? If you mean the one mentioned by bhawkes, it was made the day after I made & withdrew my comment about the high SNRM when you had no inkling of any profile change.

It's easy to be "wise" after the event, particularly when you are talking out of your blowhole.

Don't worry, I know all about the profile change as I am on Fibre, unlike you who is on ADSL? Dial-up? who knows...

_{______________________________________________________________________________. __________________}

Bald_Eagle1
(regular) Fri 09-Dec-11 20:55:13

Re: SNRM & Error levels

[re: woodyblade] [link to this post]

In reply to a post by woodyblade:
Managed to remember that some results wanted posting, this is after 68 hours uptime, looks like I've had more HEC errors than what I've seen before but less FEC errors.

Works out at 7/1 FEC errors per hour and 20/0 HEC errors per hour
Text
1
23
45
Downstream Upstream     
Line rate (kbit/s)        39998 10000CRC errors                   0      0 
FEC errors                 471     94 HEC errors                1338      0

Thanks for that woodyblade

Paul.

WWWombat
(committed) Sun 11-Dec-11 14:04:29

Re: SNRM & Error levels

[re: Bald_Eagle1] [link to this post]

In reply to a post by Bald_Eagle1:
From the unlocked HG612 modem's GUI, these are my current details:-

In case anyone is still listening to the real thread, rather than arguing over the meaning of SNR, I've come across something of a hitch...

That is that the HG612 is not reporting error data consistently!

As far as I can make out, the GUI reports CRC, FEC and HEC by taking values from the "xdslcmd info --show" command, extracting the data as follows:

- CRC comes from the "RSUnCorr" field
- FEC comes from the "OHFErr" field (I have no idea what this is. Some kind of framing error?)
- HEC comes from the "HEC" field

However, the "xdslcmd info --stats" command gives different information (but is not quite correct about some of the presentation).

The last section of the "stats" is labelled "Since Link Time" (in my case, currently 14 days), and gives FEC, CRC and ES values that I can believe. These seem to be the statistics since the last synchronisation.

The prior 4 sections of stats give the stats for smaller, more recent periods (days and 15 mins). They too look consistent.

The prior section (labelled "Total Time") also gives statistics that i believe are valid since the modem was last booted. However, it then goes on to display a time that patently *isn't* the total time the the modem has been on - but the corresponding statistics do seem to represent the full set. In my case, the full uptime is just over 16 days, the "total time" is reported as just over a day, but the numbers in the statistics are higher than the later "14 day" numbers. In fact, the numbers I see *do* reflect the burst of errors I got in the 1st 2 days, which cause DLM to resync me with interleaving... which resulted in far fewer CRC errors (and ES) and far higher FEC.

So which numbers should we believe?

Here are my numbers from the different sources:
GUI

Text

DSL up time                  1229823  (14 days 05:37:03)
 Attainable rate (kbit/s)       59256     16780
SNR margin (dB)                 10.1      11.3Line attenuation (dB)              0         0
Output power (dBmV)             12.3       6.6 
Line rate (kbit/s)             39996     10000 CRC errors                     11155         0
FEC errors                       331       288HEC errors                      2987         0

xdslcmd info --show

Text

# xdslcmd info --show
xdslcmd: ADSL driver and PHY statusStatus: Showtime
Retrain Reason: 2Max:    Upstream rate = 16758 Kbps, Downstream rate = 59256 Kbps
Path:   0, Upstream rate = 10000 Kbps, Downstream rate = 39996 Kbps 
Link Power State:       L0Mode:                   VDSL2 Annex B
VDSL2 Profile:          Profile 17aTPS-TC:                 PTM Mode
Trellis:                U:ON /D:ONLine Status:            No Defect
Training Status:        Showtime                Down            Up
SNR (dB):        10.1            11.3Attn(dB):        0.0             0.0
Pwr(dBm):        12.3            6.6                        VDSL2 framing
                        Path 0B:              57              111
M:              1               2T:              64              50
R:              16              16S:              0.0461          0.7101
L:              12835           2704D:              701             1
I:              74              120N:              74              240
                        Counters                        Path 0
OHF:            553649999               656045OHFErr:         331             288
RS:             3221633228              3957556RSCorr:         6819414         1551
RSUnCorr:       11155           0 
                        Path 0HEC:            2987            0
OCD:            0               0LCD:            0               0
Total Cells:    140396837               0Data Cells:     453789795               0
Drop Cells:     0Bit Errors:     0               0
 ES:             6235            302
SES:            8               0UAS:            35              35
AS:             1230559 
                        Path 0INP:            3.00            0.00
PER:            2.21            8.87delay:          8.00            0.00
OR:             86.72           55.88 
Bitswap:        33420           10345

xdslcmd info --stats

Text

# xdslcmd info --stats
xdslcmd: ADSL driver and PHY statusStatus: Showtime
Retrain Reason: 2Max:    Upstream rate = 16780 Kbps, Downstream rate = 59256 Kbps
Path:   0, Upstream rate = 10000 Kbps, Downstream rate = 39996 Kbps 
Link Power State:       L0Mode:                   VDSL2 Annex B
VDSL2 Profile:          Profile 17aTPS-TC:                 PTM Mode
Trellis:                U:ON /D:ONLine Status:            No Defect
Training Status:        Showtime                Down            Up
SNR (dB):        10.1            11.3Attn(dB):        0.0             0.0
Pwr(dBm):        12.3            6.6                        VDSL2 framing
                        Path 0B:              57              111
M:              1               2T:              64              50
R:              16              16S:              0.0461          0.7101
L:              12835           2704D:              701             1
I:              74              120N:              74              240
                        Counters                        Path 0
OHF:            553684194               664617OHFErr:         331             288
RS:             3228198526              91119RSCorr:         6819524         1551
RSUnCorr:       11155           0 
                        Path 0HEC:            2987            0
OCD:            0               0LCD:            0               0
Total Cells:    146241308               0Data Cells:     453791806               0
Drop Cells:     0Bit Errors:     0               0
 ES:             6235            302
SES:            8               0UAS:            35              35
AS:             1230635 
                        Path 0INP:            3.00            0.00
PER:            2.21            8.87delay:          8.00            0.00
OR:             86.72           55.88 
Bitswap:        33420           10345 
Total time = 1 days 2 hours 5 min 24 secFEC:            6819524         1703
CRC:            331             329ES:             6235            302
SES:            8               0UAS:            35              35
LOS:            5               0LOF:            5               0
Latest 15 minutes time = 5 min 24 secFEC:            435             0
CRC:            0               0ES:             0               0
SES:            0               0UAS:            0               0
LOS:            0               0LOF:            0               0
Previous 15 minutes time = 15 min 0 secFEC:            1104            1
CRC:            0               1ES:             0               1
SES:            0               0UAS:            0               0
LOS:            0               0LOF:            0               0
Latest 1 day time = 2 hours 5 min 24 secFEC:            11260           12
CRC:            0               3ES:             0               3
SES:            0               0UAS:            0               0
LOS:            0               0LOF:            0               0
Previous 1 day time = 24 hours 0 secFEC:            403855          111
CRC:            35              21ES:             11              21
SES:            0               0UAS:            0               0
LOS:            0               0LOF:            0               0
Since Link time = 14 days 5 hours 50 min 35 secFEC:            6819524         1551
CRC:            331             288ES:             114             263
SES:            0               0UAS:            0               0
LOS:            0               0LOF:            0               0

I always thought "FEC" statistics were the same as "RSCorr". These are the number of RS blocks that could be corrected by the FEC process, so are a count of teh number of correctable errors encountered. In ADSL, FEC is turned off when interleaving is off - so FEC would be zero. I guess FTTC/VDSL2 is the same.

I also always thought that the "RSUncorr" were the errors (uncorrectable by the FEC process) that therefore caused both CRC and HEC. However, RS blocks occur at a far greater rate than the CRC blocks, so you expect RSUnCorr to be the maximum of CRC+HEC. If RSUnCorr errors happen in bursts, then you might even expect 1 CRC (or HEC) per 16 RSUnCorr; if the RSUnCorr occur in a very spread-out fashion, then you'd get 1 CRC (or HEC) per RSUnCorr.

Looking at the overall output, I think the GUI ought to be reporting these values (or something like them):
CRC: 331
FEC: 6819524
HEC: 2987

However, I'm not fully convinced about the "CRC" figure here. I would have to monitor for longer.

I'm a little busy at the moment, so if I don't immediately answer any responses, you'll know why wink

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