Kitz Forum
Broadband Related => Broadband Technology => Topic started by: roseway on February 19, 2009, 10:56:20 PM
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An interesting posting (http://adsl24.co.uk/forum/showpost.php?p=80214&postcount=47) on the ADSL24 forum. Apparently, with IPSC interconnect, users will be able to specify three different levels of stability - normal, stable and super stable - on regular ADSL Max as well as on ADSL2+. These stability settings are actually different levels of target noise margin. So if this works it will allow people to manage their own target noise margins instead of relying on the slow and uncertain automatic processes.
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oooh nice one -
I had heard that something like this was in the long term plan & to give the EU more configuration options. IIRC the intended profiles were something like "normal", "stable" and "superstable", but Ive no idea how it maps to target SNR figures.
I would assume 6dB, 9dB and 12dB would be likely? Interleaving ON/OFF is also supposed to be in there too, as were faster profile changes.
Seamless Rate Adaptation (SRA) was also mentioned for 21cn/wbc. However I've no idea as and when each of these are intended to roll live.
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I prefer the Be* options of 3, 6 and 9dB. Plus interleaving control. 8)
(my 3dB line dropped to around 1dB this evening, but stayed stable and is now at 1.9dB!)
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Me too, but since BT have always defined default as 6dB, then it would make sense to me that this is where they would map 'normal' to. Stable and superstable would suggest an increase over normal hence my assumption of 6,9,12... and please note that was my interpretation since afaik nothing has ever been said what they will be.
Could be interesting how they deal with SRA - may well stop a lot of complaints about disconnects from the lesser informed users.
Faster profile changes though is a a biggy for BT, as the current 'up to 5 days' for IPprofiles and even longer for target SNR changes are a major bug-bear for many.
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>> (my 3dB line dropped to around 1dB this evening, but stayed stable and is now at 1.9dB!)
Yep - my own line copes quite happily on the 3dB target too.. and takes random dips which Ive never been able to get to the bottom off. I suspect something to do with a neighbour cause its not here.
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Thanks for the 'heads up' roseway.
As someone on an IPSC connection (Freeola/EntaNet) and also with quite a flakey line this sounds like good news :)
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Just to add to this...
The owner of ADSL24 is saying that this isn't only going to be an IPSC feature but allegedly coming for all Max users...
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That's interesting, but I think I've read that all BT-based connections will be moved over to IPSC in the fairly near future.
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an Aussie one ? :lol:
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That's interesting, but I think I've read that all BT-based connections will be moved over to IPSC in the fairly near future.
I've read that too but I believe they are two separate things :)
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I posted about this over at Plusnet, and got a few replies including;
It's absolutely not a way of decreasing the target SNR...
And;
It's basically an increase in interleaving depth and SNR above the default.
On other words, changing the "service option" will make your speed worse than it already is - but it will be more stable connectivity wise.
In other words, I don't think they're in favour. The same rep also said it had been around for about 8 months.
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I can't recall exactly where I got the info now from as Ive had the document since last year... but this is what it says on the BTw doc.
WBC options for reducing fault costs
Broadband on 21CN extends this capability to deliver :
Faster profile changes and greater granularity
Proactive repair tools
Delivering more information/tools to customers for complex fault diagnosis
Selectable profiles – standard stable and super-stable (for video)
Seamless rate adaptation
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btw there was also an image with this [see attatchment below].
As I mentioned in my earlier post there was no actual definitions of the figures, but from the image it allows 6 different configurations.
Below are the 6 different profiles. The figures in italics being my assumption of what they are most likely to be.
1) Interleaving OFF - Normal profile (likely 6dB Target SNR)
2) Interleaving OFF - Stable profile (probably 9dB Target SNR?)
3) Interleaving OFF - SuperStable profile (probably 12dB SNR?)
4) Interleaving ON - Normal profile (likely 6dB Target SNR)
5) Interleaving ON - Stable profile (probably 9dB Target SNR + possible increased depth of interleaving?)
6) Interleaving ON - Super Stable (probably 12dB Target SNR + possible further increased depth of interleaving?)
>> It's absolutely not a way of decreasing the target SNR...
Since the profiles are also available for non interleaved lines... then surely that means that it must involve changing the Target SNR.
If a line is non-interleaved.. changing interleaving depth would be a complete waste of time!
Based on the fact that a 3dB Target profile change will make a difference of anything from 400kbps to 1200kbps of sync speed depending on how many bits are loaded per bin.. this ties in very nicely with what James from adsl24 has said about each step lowering the sync speed by about 800k.
(800kbps is a fair figure to quote as average for 3dB of target SNR).
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btw forgot to mention - increasing interleaving depth adds to delay (increased latency). Therefore increasing interleaving depth doesnt effect your sync speed.. but it does increase your ping times. Latency != speed.
Theres also one other configurable attribute that also hasnt been mentioned and thats error correction, which is turned on when interleaving is applied. Theres little (read none) information from BT how they handle this, but they certainly do appear to have different levels of error-correction (http://www.kitz.co.uk/adsl/error_correction.htm#RS).
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