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Standard User ian72
(eat-sleep-adslguide) Fri 07-Apr-17 11:01:08
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Re: Openreach to rollout 3dB target SNRm for FTTC next year


[re: WilliamGrimsley] [link to this post]
 
What evidence do you have? Is it that it is up to date when you look at it on the stats page or when something else reads the data? If so, as a programmer it would, as Bob says, be more sensible to calculate when it is requested rather than calculating a number over and over again that has no bearing on the operation of the modem and is purely useful to a human being looking at the screen.
Administrator MrSaffron
(staff) Fri 07-Apr-17 11:29:21
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Re: Openreach to rollout 3dB target SNRm for FTTC next year


[re: RobertoS] [link to this post]
 
Debate technical issues, not name calling.

The moral to this thread is that if you chase for minute detail, then others will chase you for minute detail too.

So often better to couch statements with the usual caveats e.g. in this case something along the lines of what the majority of people see when on the stats page of their device, ie. that attainable rate varies over time driven by changing parameters and appears to update every few seconds.

The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User RobertoS
(elder) Fri 07-Apr-17 12:20:24
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Re: Openreach to rollout 3dB target SNRm for FTTC next year


[re: MrSaffron] [link to this post]
 
It only updates every few seconds because the device requests an update.

To illustrate, we know the SNR by its very nature varies continuously, as it is an analogue item. It is fair to assume the SNRM itself updates in line with that, but it is not guaranteed that it does. It may be a digital calculated figure from the SNR.

It is clear that as SNR varies the max attainable varies as an analogue value, but the more one thinks about it the less feasible it becomes for the modem to know what it is. It would have to be running a calculation loop. It isn't an intrinsic part of the connection protocol.

When looking at stats on a device the figures change at fixed intervals, not continuously. The update occurs because the device requests a refresh from the modem. Exactly like all the monitoring programs. Even the GUI on a combo device does not continuously update.

There is no reason to assume the max attainable is calculated at sync-time, nor that it is continuously recalculated. It is not a figure of any use to the functioning of the modem. There is every reason to believe it is a display figure calculated on demand.

To say "it's continually calculated whilst the line is in sync as line conditions change" and "it's blatantly obvious that it updates when the line is active" has to be nonsense. It would make calculating it more important than maintaining sync, bit-swapping, and passing data.

The poster is asserting false detail, not chasing it.

Kindness isn't going to cure the world of all its awfulness but it's a good place to begin. Daisy Ridley.
My broadband basic info/help site - www.robertos.me.uk. Domains, site and mail hosting - Tsohost.
Connection - AAISP Home::1 80/20. Sync 63790/13596Kbps @ 600m. BQMs - IPv4 & IPv6

Edited by RobertoS (Fri 07-Apr-17 12:21:06)


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Standard User Jez_
(newbie) Fri 07-Apr-17 15:48:28
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Re: Openreach to rollout 3dB target SNRm for FTTC next year


[re: RobertoS] [link to this post]
 
I have noticed that my line has slowly dropped over the last few days in 1db steps, down to its current 3.4db matched by a 79999 sync which i have not seen in around a year. Great news smile

I appear to have a slight issue with usable bandwidth though, my actual usable bandwidth when maxing out the line sits where it did before the changes, at just over 70mbit.

Strange one, its almost as though i have an IP profile which is stuck at the old sync rate which was that speed, which had been maintained for a long time?
Standard User WilliamGrimsley
(experienced) Fri 07-Apr-17 15:51:12
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Re: Openreach to rollout 3dB target SNRm for FTTC next year


[re: RobertoS] [link to this post]
 
Thanks for the in-detail explanation. I apologise, but surely there has to be a calculation somewhere in order for the attainable rate to be calculated before it displays it on the line stats page?

Sync: 40225/7660 Kbps.
Administrator MrSaffron
(staff) Fri 07-Apr-17 15:52:54
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Re: Openreach to rollout 3dB target SNRm for FTTC next year


[re: WilliamGrimsley] [link to this post]
 
>but surely there has to be a calculation somewhere in order for the attainable rate to be calculated before it displays it on the line stats page?

Yes, but it may simply be triggered by loading that page, or other methods of requesting the value, i.e. calculated on the fly

The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User MHC
(sensei) Fri 07-Apr-17 17:28:12
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Re: Openreach to rollout 3dB target SNRm for FTTC next year


[re: MrSaffron] [link to this post]
 
With experience of other comms systems, I can suggest three possible reasons for a recalc of the figure:

A specific request from a GUI or other external monitoring system.
If error rates (or another parameter) suddenly change, up or down.
On a timer - perhaps every 10 or 20 seconds and certainly not every few tens of millseconds.

There may well be others.

And as you MsS will know with your background, as this information is not vital to operations it will be a low priority task and delayed or not activated if the CPU is running at over a specific usage level.


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

M H C


taurus excreta cerebrum vincit
Standard User j0hn83
(member) Fri 07-Apr-17 19:17:11
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Re: Openreach to rollout 3dB target SNRm for FTTC next year


[re: troublegum] [link to this post]
 
I would be very surprised if you had a 3dB target SNRM.
Every example I've seen of the new lower target has seen it drop in 1dB stages, never straight from 6dB to 3dB.
Every example has also been on Huawei DSLAMs.
You're line is connected to an ECI DSLAM and jumped straight to 3dB. I say with confidence this is not a target SNRM set by DLM.
There are dozens of reasons that cause SNRM to fall to 3dB, including new crosstalkers, DSLAM reboots, line characteristic changing, line faults, etc. The attainable being higher than sync is not conclusive. We only have limited stats, from a single moment in time. The line could be interleaved which causes the higher attainable. We don't know such modem you use, the attainable may always be considerably higher than sync.

We can say with certainty that a line has a 3dB target SNRM when we can see all the stats, recorded every minute on MyDSLWebStats, with a familiar Broadcom chipset.

With 4 lines of stats, gathered once, without knowing the modem, on an ECI DSLAM, jumping straight to 3dB without 1dB steps, I'm confident it's not a set target SNRM.
Standard User WilliamGrimsley
(experienced) Fri 07-Apr-17 19:30:28
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Re: Openreach to rollout 3dB target SNRm for FTTC next year


[re: j0hn83] [link to this post]
 
Well, if those line stats don't prove to you that it's at 3 dB, then I don't know what will. wink

Router in use: Billion BiPAC 8800AXL.

Edited by WilliamGrimsley (Fri 07-Apr-17 19:30:48)

Standard User troublegum
(member) Fri 07-Apr-17 19:33:15
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Re: Openreach to rollout 3dB target SNRm for FTTC next year


[re: j0hn83] [link to this post]
 
It's a Billion 8800NL and interleaving certainly is on. As I said, it'll be getting powered down on Tuesday so we'll find out then whether it retains the 3dB margin or not.
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