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Standard User j0hn83
(member) Fri 03-Feb-17 03:20:14
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Re: Openreach to rollout 3dB target SNRm for FTTC next year


[re: BatBoy] [link to this post]
 
That doesn't make sense. Do you think your modem has synced at 5dB but it's working out it's attainable from a 6dB snrm? Because that isn't possible.
Standard User j0hn83
(member) Fri 03-Feb-17 03:47:19
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Re: Openreach to rollout 3dB target SNRm for FTTC next year


[re: sohail2k] [link to this post]
 
In reply to a post by sohail2k:
Understood.
You could be right but I am not aware of any other reason which could have lowered the SNRM. This is the first time I have see it and it was actually below 3db. Should have taken the telnet stats. If it happens next time I'll do that.

Just to mention that I live in Reading (Earley area), and the exchange is not on the list of test exchanges (someone posted a list on these forums). So not sure how we take these results.

I'll try to do a resync tonight or early tomorrow morning (15 min power cycle method).

If the SNRM drops and the sync rises the attainable will rise in a similar pattern. If the attainable remains what it usually is, and is considerably lower than sync, then it's almost certainly not a lower target snrm.
Standard User RobertoS
(elder) Fri 03-Feb-17 09:36:55
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Re: Openreach to rollout 3dB target SNRm for FTTC next year


[re: j0hn83] [link to this post]
 
As I, MrSaffron and others have pointed out, it is entirely possible. In fact almost certainly happening. It merely requires the 6dB to be hard coded in the modem's firmware, and from several examples that appears to be the case.

How else, under the pre-existing regime, does the attainable rate significantly exceed the actual when the sync-time margin is 9dB or higher? On both VDSL2 and ADSLx, different DLMs from different suppliers.

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 54999/14466Kbps @ 600m. BQMs - IPv4 & IPv6


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Standard User j0hn83
(member) Fri 03-Feb-17 11:33:09
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Re: Openreach to rollout 3dB target SNRm for FTTC next year


[re: RobertoS] [link to this post]
 
Hard coded in the firmware? that's a load of nonsense. It's an OpenReach setting, absolutely nothing to do with CPE firmware. The attainable is way higher when interleaving + FEC is enabled.
The max attainable rate calculation was rather loosely defined in the original VDSL2 ITU documents and many modems incorrectly calculate it, particularly when interleaving is enabled. The target SNRM is absolutely not "hard coded" in firmware.

And to add, of course it's entirely possibly. On an exchange where the trial isn't active, where only the sync had risen significantly, the attainable had remained static, I'd stick with "almost certainly not".

Edited by j0hn83 (Fri 03-Feb-17 11:41:13)

Standard User RobertoS
(elder) Fri 03-Feb-17 11:46:26
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Re: Openreach to rollout 3dB target SNRm for FTTC next year


[re: j0hn83] [link to this post]
 
Openreach do not set the base figure in the modem. End of. How it is obtained is entirely up to the modem manufacturer, as you correctly point out.

The posters concerned know what they are observing and how to interpret it. They also know how their actual/attainable/SNRM behave when the Openreach base setting at the DSLAM is 6dB, and how that behaviour has changed.

You said it is impossible for the modem to be using 6dB as the base figure for calculating attainable. You cannot possibly know that for exactly the reason you state.

Similarly, all the posters (including myself) discussing the matter are fully aware of the effect interleaving has on the calculation and that the result is usually crackers.

As has been stated, the only way to be sure of the sync-time DSLAM setting is to take the stats immediately after connection, or better still from the modem log if it records 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 54999/14466Kbps @ 600m. BQMs - IPv4 & IPv6
Standard User RobertoS
(elder) Fri 03-Feb-17 11:49:09
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Re: Openreach to rollout 3dB target SNRm for FTTC next year


[re: j0hn83] [link to this post]
 
Re one of your inclusions added while I was writing my previous reply
In reply to a post by j0hn83:
The attainable is way higher when interleaving + FEC is enabled.
Not when G.INP is active.

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 54999/14466Kbps @ 600m. BQMs - IPv4 & IPv6
Standard User Realalemadrid
(regular) Fri 03-Feb-17 11:50:49
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Re: Openreach to rollout 3dB target SNRm for FTTC next year


[re: j0hn83] [link to this post]
 
I think you are misunderstanding what has been suggested and looks to be consistent with observed results, that the modem calculation of attainable rate assumes a fixed 6db SNRM and doesn't use the actual SNRM value. So the target SNRM for the attainable rate calculation is hard coded in the modem firmware.
Standard User j0hn83
(member) Fri 03-Feb-17 11:52:47
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Re: Openreach to rollout 3dB target SNRm for FTTC next year


[re: RobertoS] [link to this post]
 
In reply to a post by RobertoS:
Re one of your inclusions added while I was writing my previous reply
In reply to a post by j0hn83:
The attainable is way higher when interleaving + FEC is enabled.
Not when G.INP is active.
That's why I didn't say G.INP. G.INP is not interleaving or FEC.
Standard User RobertoS
(elder) Fri 03-Feb-17 11:55:46
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Re: Openreach to rollout 3dB target SNRm for FTTC next year


[re: j0hn83] [link to this post]
 
With G.INP active both downstream interleaving and FEC are also active. G.INP is not invoked unless interleaving is needed. By adding retransmission it is able hugely to reduce the interleaving depth.

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 54999/14466Kbps @ 600m. BQMs - IPv4 & IPv6

Edited by RobertoS (Fri 03-Feb-17 11:57:24)

Standard User lee111s
(experienced) Fri 03-Feb-17 11:55:48
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Re: Openreach to rollout 3dB target SNRm for FTTC next year


[re: Realalemadrid] [link to this post]
 
In reply to a post by Realalemadrid:
I think you are misunderstanding what has been suggested and looks to be consistent with observed results, that the modem calculation of attainable rate assumes a fixed 6db SNRM and doesn't use the actual SNRM value. So the target SNRM for the attainable rate calculation is hard coded in the modem firmware.


I'd also agree
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