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Author Topic: DLM has put me on a 3 dB (ish) target SNRM  (Read 2601 times)

WWWombat

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Re: DLM has put me on a 3 dB (ish) target SNRM
« Reply #30 on: June 18, 2017, 05:47:44 PM »

Remember a cross-talker is only added when a modem reaches sync and starts transmitting. It isn't necessarily when a connection is changed in the cabinet - self-install could just be when a subscriber gets home from work. And it doesn't have to be someone new - it could be someone returning from holiday. Or just getting up in the morning.

A modem reaching sync can have different impacts on other subscribers. It can cause an increase in noise, or an increase in errors, or both. Or nothing.

In this case, it isn't clear why DLM has made a change, but it might be because there was a resync the day before.

I'm approaching the XdB implementation with an open mind as to how DLM will have changed to cope, but I do expect to see some different behaviour. After all, the whole premise of using 3dB can make any line more susceptible to fast-developing changes in the environment ... so I expect DLM to have tricks up its sleeves for a faster response.

One open concern I have is this: How will DLM react if it has inadvertently made a line a little less stable - such that it causes resyncs rather than errors.  I expect to see signs that DLM falls back by 1dB if it is "pressured" at all.

I can imagine a plausible method where DLM has had a hint that a line is less-than-perfectly-stable (ie after a resync), where it sets the "target SNRM" to XdB and a (new) "next target SNRM" to X+1dB in case there is a further resync.

With such behaviour, today's 5dB target might have been because there was a resync yesterday at 4dB and a further resync today.
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Chrysalis

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Re: DLM has put me on a 3 dB (ish) target SNRM
« Reply #31 on: June 18, 2017, 05:53:31 PM »

yeah that can explain the instances when we see crosstalk start at odd times, as we forget self install is simply when the modem is first powered up.
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lee111s

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Re: DLM has put me on a 3 dB (ish) target SNRM
« Reply #32 on: June 18, 2017, 11:10:43 PM »

I know but a new cross-talker would require a connection in the cabinet and that would most likely be in daylight hours not talking migration from provider to provider. That doesn't require physical work at the cabinet just the flick of a virtual switch as far as I am aware.

I believe when chaging ISP's actually involves a physical port change at the cab. Something to do with making it equivalent for each provider.
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j0hn

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Re: DLM has put me on a 3 dB (ish) target SNRM
« Reply #33 on: June 19, 2017, 03:07:21 PM »

Changing ISP definitely involves no work at the cabinet. All the port assignment work is done remotely. Changing the port during an ISP switch would make no difference.

If the cabinet has spare capacity then even cancelled lines are left connected to the cabinet so they can be turned back on remotely.
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lee111s

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Re: DLM has put me on a 3 dB (ish) target SNRM
« Reply #34 on: June 19, 2017, 07:54:30 PM »

Changing ISP definitely involves no work at the cabinet. All the port assignment work is done remotely. Changing the port during an ISP switch would make no difference.

If the cabinet has spare capacity then even cancelled lines are left connected to the cabinet so they can be turned back on remotely.

Then explain how people have placed migration orders only to find on the day they switch, there's no spare capacity. Their old port isn't able to be used.

It also explains why you can't change ISP if the cab is full or awaiting additional capacity.
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WWWombat

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Re: DLM has put me on a 3 dB (ish) target SNRM
« Reply #35 on: June 20, 2017, 09:43:14 AM »

@lee111s, I think you are talking about the exceptional cases, while @j0hn is talking about the usual cases.

There needs to be spare capacity at the time of the order, which has been explained away as for reasons of equivalence. Agreed.

However, I'm not sure I've come across a case where the order fails in this way on the day of migration.
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kitz

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Re: DLM has put me on a 3 dB (ish) target SNRM
« Reply #36 on: June 20, 2017, 09:46:45 AM »

There's no changes at the cab during migration.  If migration involves one of the MPF ISPs then there will be physical changes at the MDF -> LLU Tie for telephony.  As far as the FFTC goes then the SVLAN has to be remapped at the headend exchange.


>>> Then explain how people have placed migration orders only to find on the day they switch, there's no spare capacity.


I think those instances may be more to do with a failure in the SIM provide process.   In order to ensure that both services go through on the same day, the gaining ISP should place the FTTC SIM provide before the MPF SIM provide.

Quote
We do recommend that you place the FTTC Provide part of the SIM provide order before the MPF/WLR Provide order to make sure that the migration of both the FTTC and the underlying WLR/MPF are matched together. Obviously, we all want to avoid the end user being without broadband service for several days (which can happen if the two migration orders fail to be matched within Openreach’s systems).

>>> It also explains why you can't change ISP if the cab is full or awaiting additional capacity.


When the ISP places the FTTC provide part, I'm assuming the system doesnt know that point it will be a SIM provide and therefore rejects the FTTC provide part due to the cab being full. :/


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ETA...  wombat was typing same time as me.
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LorianNod

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Re: DLM has put me on a 3 dB (ish) target SNRM
« Reply #37 on: July 11, 2017, 07:33:55 AM »

My line has been sat on 6b SNR since the trial.

Since Friday DLM has forced a resync each day with the SNR dropping towards 3db each time. one more to go I think, hopefully.
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