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>> Fibre Broadband

john_thorax
(newbie) Wed 08-Feb-12 00:36:08

Advice from the experts...worth getting OR out again?

[link to this post]

Hi everybody,

I was hoping to canvass the opinions of the resident experts as to whether it is worth getting OR out again for FTTC speed issues. I don’t want to spend another day at home if the chance of speed improvements is small. I also ought to say that I appreciate my FTTC speed is significantly better than some of those on ADSL, so don’t mean to moan.

My FTTC is synced at ~24, and has been since the install last week. The BT speed checker suggests that I should be able to get 33.9/6.5. I live 750m away from the cabinet. Due to error seconds on the line, and a below predicted sync rate, PlusNet expeditiously arranged for an OR engineer to come out. In the end, two engineers came on the same day (only one underground trained). One, an apprentice, suggested from his testing that there may be an underground fault 81 feet away, but he was unable to investigate other than confirming that a full 40/2 was possible at the cabinet and doing a profile reset (causing no improvement). The second engineer replaced my external wiring and junction box (making no difference – it was just old), and changed some of the crimp connectors at the cabinet, but (as far as I can tell) didn’t lift any manholes (my cable is fully underground). He declared the line to be healthy and stated that the sync speed was just ‘one of those things’. Both engineers spent quite a while doing tests with their JDSU etc. I’ve noticed no noise on the quietline test.

I’ve interrogated the OR modem, and attach the figures below. It strikes me that the predominant finding is very high attenuation figures, although I’m clearly not an expert. I suspect (although don’t categorically know) that some of my line may be aluminium, which may be a factor.

Max: Upstream rate = 3645 Kbps, Downstream rate = 24464 Kbps
Path: 0, Upstream rate = 1999 Kbps, Downstream rate = 24700 Kbps

VDSL Port Details Upstream Downstream
Attainable Net Data Rate: 3645 kbps 24464 kbps
Actual Aggregate Tx Power: 5.9 dBm 10.5 dBm
===============================================
VDSL Band Status U0 U1 U2 U3 D1 D2 D3
Line Attenuation(dB): 10.2 59.0 67.0 N/A 23.6 67.6 0.1
Signal Attenuation(dB): 15.9 58.1 N/A N/A 23.6 67.6 N/A
SNR Margin(dB): 11.0 10.8 N/A N/A 5.7 0.0 N/A
TX Power(dBm): -4.3 5.4 N/A N/A 9.6 3.1 N/A

The results of PN testing are below;

Current and Last 15 Minute Bin Performance
Last Traffic Count(Upto 15 mins) Current Traffic Count(Upto 15 mins)
Ingress Code Violation 2 0
Egress Code Violation 43 25
Errored Seconds 34 21
Severely Errored Seconds 0 0
Unavailable Seconds 0 0

(sorry about formatting - can't get tabs to work)

My question is whether it’s worth getting OR out again? PN have been very proactive in offering to (due to the ongoing sync speed and error seconds). I have a suspicion that this all may be due to possible underground aluminium, but I have no idea whether there are other equally likely explanations. Essentially, would the experts bother with OR or just make do?

Thanks very much!

John

MHC
(legend) Wed 08-Feb-12 00:48:28

Re: Advice from the experts...worth getting OR out again?

[re: john_thorax] [link to this post]

40/2 at the cabinet - I would certainly expect that to be the case! But is does prove that at that point everything is fine.

750m - it really will depend on what the line condition is and the conductor size. The 33.9 is a real estimate based on actual figures from other users (but I've no idea how they process the data and apply it to specific lines). It could be that there is a lot of noise being picked up on your line - maybe crosstalk, maybe from other sources - a full set of plots from the modem data may be useful for people to comment on.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

M H C

taurus excreta cerebrum vincit

Bald_Eagle1
(member) Wed 08-Feb-12 11:39:06

Re: Advice from the experts...worth getting OR out again?

[re: john_thorax] [link to this post]

I don't know if you are already aware but you can obtain similar useful detail from xdslcmd info --stats

Text

# xdslcmd info --stats 
xdslcmd: ADSL driver and PHY statusStatus: Showtime
Retrain Reason: 2Max:    Upstream rate = 6224 Kbps, Downstream rate = 31744 Kbps
Path:   0, Upstream rate = 6142 Kbps, Downstream rate = 23367 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):        9.6             6.3Attn(dB):        0.0             0.0
Pwr(dBm):        12.1            6.2                        VDSL2 framing
                        Path 0B:              63              191
M:              1               1T:              60              38
R:              16              12S:              0.0871          0.9921
L:              7346            1645D:              371             1
I:              80              102N:              80              204
                        Counters                        Path 0
OHF:            1478471         617820OHFErr:         55              16
RS:             266170258               1989735RSCorr:         86103           12
RSUnCorr:       752             0 
                        Path 0HEC:            186             0
OCD:            0               0LCD:            0               0
Total Cells:    261172748               0Data Cells:     947993          0
Drop Cells:     0Bit Errors:     0               0
 ES:             161             14
SES:            57              0UAS:            43              43
AS:             5821 
                        Path 0INP:            3.00            0.00
PER:            3.92            9.42delay:          8.00            0.00
OR:             48.97           27.16 
Bitswap:        610             480 
Total time = 3 hours 51 min 19 secFEC:            4634573         30
CRC:            18675           22ES:             161             14
SES:            57              0UAS:            43              43
LOS:            4               0LOF:            5               0
Latest 15 minutes time = 6 min 19 secFEC:            15810           0
CRC:            31              0ES:             8               0
SES:            0               0UAS:            0               0
LOS:            0               0LOF:            0               0
Previous 15 minutes time = 15 min 0 secFEC:            7081            0
CRC:            0               0ES:             0               0
SES:            0               0UAS:            0               0
LOS:            0               0LOF:            0               0

That's just a snippet of the detail you can obtain from the OR supplied HG612 modem for yourself.

The mention that there is a suspected fault at a distance of 81 feet suggests that TDR testing has been carried out.

If that is a HR (high resistance) fault, it MIGHT explain your high attenuation values.
The cause of the fault ????

Corrosion, dry joint, bridge tap, water ingress, aluminium cables etc. etc. are potential causes of HR issues.

I am supposedly 1000m away from the cabinet (I think it is realistcally more like 850m) & my attenuation values are a bit lower than yours.

Your SNRM levels appear to be high enough to be able to achieve a higher speed, but I see you are actually synced at a slightly higher speed than your attainable rate, which is not unseen, but is quite unusual.

Your power levels also look a little low.

These are my recent stats:-

Text

# xdslcmd info --pbParams 
xdslcmd: ADSL driver and PHY statusStatus: Showtime
Retrain Reason: 2Max:    Upstream rate = 6213 Kbps, Downstream rate = 31828 Kbps
Path:   0, Upstream rate = 6142 Kbps, Downstream rate = 23367 Kbps 
Discovery Phase (Initial) Band PlanUS: (0,95) (868,1207) (1972,2783) 
DS: (32,859) (1216,1963) (2792,3939) Medley Phase (Final) Band Plan
US: (0,95) (868,1207) DS: (32,859) (1216,1963) 
       VDSL Port Details       Upstream        DownstreamAttainable Net Data Rate:       6213 kbps         31828 kbps
Actual Aggregate Tx Power:        6.2 dBm          12.1 dBm============================================================================
  VDSL Band Status        U0      U1      U2      U3      D1      D2      D3  Line Attenuation(dB):  8.5     52.4    63.7     N/A    21.7    62.6    0.1    
Signal Attenuation(dB):  14.4    51.6     N/A     N/A    21.7    62.6     N/A           SNR Margin(dB):  6.3     6.4      N/A     N/A    9.6     9.9      N/A   
         TX Power(dBm): -4.2     5.8      N/A     N/A    11.1    5.0      N/A

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