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[broadstairs]

Can someone please explain to me (or point me at a document) how the bands are allocated to either u/s or d/s and whether or not my u1 snrm band being permanently 0 is because of a fault or something DLM has done to prevent the equivalent band being used. My line now looks like it is restricted to 40000kbps down and 800kbps up possibly by DLM because of all the issues I've been having and now wondering if the problem has gone away for now or being masked by the restrictions DLM has put in place. My attainable speeds show 70311kbps down and 23288kbps up. I have an OR guy coming tomorrow afternoon.

Stuart

[WWWombat]

Bandplan
The frequencies in each band are fixed. The ANFP specifies that we use bandplan 998ADE17-M2x-A, which is one of the 17MHz profiles.

Details of the bandplans, including the specific frequencies for the various bands, can be found here, on page 5:
http://www.joepeesoft.com/Public/DSL_Corner/Docs/Publications/PUB_2009_10_TNO35092_SpM_VDSL2_FreqAllocations.pdf

The decision whether or not to use any tone comes after the Hlog and QLN have been measured; the available SNR (plus the target SNRM of 6dB) must be above a certain threshold. This, I think, os the outcome of the "medley phase" visible in "--pbParams".

Allocating bits to tones
Then comes the process of allocating bits to tone, until the "maximum speed" has been reached. This "iterative water filling" mechanism tries to maximise speed while minimising potential errors (ie trying to keep SNRM as high as possible on each tone) as well as trying to minimise power (the upstream power backoff mechanism). This algorithm can be pretty complex (eg http://file.scirp.org/pdf/CN20110400003_95057946.pdf )

From looking at many lines, my guess is that U1 tends to be used less than it could because of the upstream power backoff mechanism. But this probably applies more in cases where the line is running at the full package speed, or the full "banded" speed.

Your U1 band
In your case, it looks much more like the modem didn't like the Hlog readings: there is nothing there in that graph, while the QLN graph looks normal. The end result is no bits, and not even any SNRM readings. I suspect U1 has been left out of the medley .... can you show us a "--pbParams" before the next sync?

Having said all that, your line looks to have recovered somewhat today, and a resync will probably restore speeds. Bad timing with OR arriving tomorrow...

[broadstairs]

Here is the current pbparams data today. The last re-sync was just after 8am today which I did as I was doing some testing of filters etc.

Code: [Select]

adsl info --pbParams
adsl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason:    1
Last initialization procedure status:   0
Max:    Upstream rate = 23374 Kbps, Downstream rate = 69527 Kbps
Bearer: 0, Upstream rate = 800 Kbps, Downstream rate = 40000 Kbps

Discovery Phase (Initial) Band Plan
US: (6,31) (882,1193) (1984,2770)
DS: (33,857) (1218,1959) (2795,4083)
Medley Phase (Final) Band Plan
US: (6,31) (882,1193) (1984,2770)
DS: (41,857) (1218,1959) (2795,4083)
                  VDSL Port Details               Upstream                Downstream
Attainable Net Data Rate:           23374 kbps              69527 kbps
Actual Aggregate Tx Power:             5.2 dBm                5.2 dBm
====================================================================================
  VDSL Band Status U0 U1 U2 U3 U4 D1 D2 D3
  Line Attenuation(dB): 1.7 22.7 34.2 N/A N/A 12.1 28.5 45.0
Signal Attenuation(dB): 1.6 22.5 34.1 N/A N/A 16.0 28.3 44.9
        SNR Margin(dB): 31.2 0.0 23.5 N/A N/A 10.3 10.2 10.3
         TX Power(dBm): -5.5 -24.2 4.8 N/A N/A 9.6 7.3 7.4
 >
Stuart

[NewtronStar]

Don't know what to say broadstairs and spent some time looking through your on line stats on MDWS but it looks the same issue Starman had for months in 2015 and now his line is stable again after fault found and corrected by Openreach engineer.

My fingers are well crossed for you 

[WWWombat]

Ah, I think those params will have lost what I was looking for. Never mind.

What I seemed to miss this morning is that the upstream attainable jumped, and the actual sync recovered, but only a little. It looks to be banded at 0.8Mbps.

[broadstairs]

Ah, I think those params will have lost what I was looking for. Never mind.

What should I look out for in future if/when the problem recurs?

Stuart

[broadstairs]

Well about an hour ago an OR guy called me to say he was coming to install a new phone line    I explained that this was NOT what I expected and I've asked TT to confirm the guy coming will be a broadband guy and not a line man. Heaven knows where the communication went wrong!

Stuart

[Black Sheep]

I can guess .................... we (OR), work to instruction given by the CP/ISP. 

[broadstairs]

Yes I can believe it was TT, I think the person ho called to arrange the appointment was from their Indian call centre.

Stuart

[WWWombat]

What should I look out for in future if/when the problem recurs?

Changes to the "Discovery phase band plan" and the "Medley phase band plan" figures.

[broadstairs]

Well the OR guy came today, stuck his JDSU on the line and told me its working OK, well I guess that looking at the stats. I suggested he reset the line again but he said he would go to the cabinet to do some more diagnostics and that I'd see a line drop, well I didn't see any further line drops and when I drove past the cabinet he was nowhere to be seen. He tried to tell me that there is a probable issue with TT equipment in the exchange causing this and that each customer has their own fibre connection back to the exchange from the cabinet. Now I don't really believe that the fibre is run for each user, my basic understanding was that FTTC was like extending the exchange to the cabinet - I can't see each end user having their own bit of fibre. The guy that came did not seem the slightest bit interested in the evidence I have of an intermittent fault.

So I'm left with a line capped at 40meg down and 0.8meg up which is woeful and well below what I am paying for and the line is capable of, even the wholesale line checker says impacted I should get 55meg down I think. OK now I have a fight on my hands because I know TT will say wait for DLM to recover the line and will say anything else is beyond their capability to affect. I will see what response I get on the TT forum but I expect to have to contact the CEO once again. The biggest issue this time was the delay caused by their network team who sat on this issue for days before doing anything about sending OR out, Had they been quicker the OR might have come while the fault existed.

Stuart

[NewtronStar]

Engineer No3 and no fault found and your modem is showing your line has been in sync since 8:01am 20/7/2016 when they test with this JDSU do they not take the modem offline during the tests and then plug the modem back in after all is done and this would show up as new resync

[Black Sheep]

Yes, the EU's modem/router would need to be unplugged for a minimum of 10mins whilst the mandatory 'PQT' and 5 minute 'DSL Close out test' were completed.
Chances are it would usually be slightly longer as the engineer explains the results to the EU, but as I say ....... minimum of 10mins.

[NewtronStar]

Cheers BS any idea why the engineer would say he was going to the cabinet to check and then from broadstairs beady eye's he never showed up in that location

[Black Sheep]

I wouldn't know, NS ............ with respect to Stuart, one can't monitor the synch status of the router whilst driving to the Cab at the same time ?? Maybe something happened during the crossover point ?? It seems that the monitoring stats haven't picked up on the engineers need to test at Stuarts premises, maybe the engineer did break the circuit down again at the Cab and it's not been picked up again on the stats ??

The problem with intermittency or a miniscule fault that our test systems won't pick up on, is that the engineer stands a high chance of getting a 'Repeat report' against him if the EU raises another fault. As the Cab is the piece of equipment that sees the most footfall from engineers, and lots of messing around in them, it is good practice to perform a visual inspection in there for signs of accidental damage.

All guess work.