cancel
Showing results for 
Search instead for 
Did you mean: 

Seemless rate adaptation

Community Veteran
Posts: 2,430
Thanks: 266
Fixes: 2
Registered: ‎04-08-2009

Seemless rate adaptation

I've heard rumours that BT has introduced SRA on ADSL2+. Are any of the PN techs able to confirm this please?
9 REPLIES
sjrinfroyle
Grafter
Posts: 895
Registered: ‎08-05-2011

Re: Seemless rate adaptation

I don't think it's available on many providors. It's available on Bethere who are LLU, but I don't think it's available on any BT Wholesale providors.
Community Veteran
Posts: 6,735
Thanks: 12
Registered: ‎02-02-2008

Re: Seemless rate adaptation

Quote from: sjrinfroyle
It's available on Bethere who are LLU

Not really, Be are undertaking a SMALL trial at present.
I think that UKonline also did some work on SRA before they closed down.
Superuser
Superuser
Posts: 9,803
Thanks: 1,168
Fixes: 67
Registered: ‎06-04-2007

Re: Seemless rate adaptation

Quote from: nozzer
I've heard rumours that BT has introduced SRA on ADSL2+.

What BT are presently introducing on 21CN WBC (ADSL2+, ADSL2 and ADSL1) is not seamless rate adaptation (SRA) but what has been called quantisation. For SRA  transmission speed (bit rate) continuously adapts to line conditions - increasing or decreasing. However with quantisation the transmission speed (bit rate) remains fixed once sync is gained, but the IP Profile is immediately set to 88.2% of this. If line conditions deteriorate, as now sync could be lost and be regained at a lower speed. If line conditions improve it would require a user-initiated re-sync to achieve a higher sync speed - but the benefit would be seen immediately*.
Target noise margins will still apply, and as now re-syncing too often is likely to cause target noise margin to increase.
Since IP Profiles when quantisation is in operation are 88.2% of sync speed they will generally not be round numbers.
* Plusnet have still to announce how the Plusnet profile (Current line speed) will be adapted to work with quantisation.
David
Community Veteran
Posts: 3,366
Thanks: 15
Registered: ‎06-04-2007

Re: Seemless rate adaptation

Quote from: spraxyt
* Plusnet have still to announce how the Plusnet profile (Current line speed) will be adapted to work with quantisation.

Hopefully, the answer is that it will be completely removed as in an all IP system, it is redundant.
It was also truly not needed in an ATM world, but BT fooled enough people enough of the time into believing it had 'some use'. Sad
But us Market1/20CN/IPSC users will still be unable to benefit from this.
--
3Mb FTTC
https://portal.plus.net/my.html?action=data_transfer_speed
itsme
Grafter
Posts: 5,924
Thanks: 1
Registered: ‎07-04-2007

Re: Seemless rate adaptation

Why is it not needed?
Community Veteran
Posts: 6,316
Thanks: 86
Fixes: 3
Registered: ‎08-01-2008

Re: Seemless rate adaptation

Quote from: itsme
Why is it not needed?

or, indeed, why IS it needed?
Call me 'w23'
At any given moment in the universe many things happen. Coincidence is a matter of how close these events are in space, time and relationship.
Opinions expressed in forum posts are those of the poster, others may have different views.
itsme
Grafter
Posts: 5,924
Thanks: 1
Registered: ‎07-04-2007

Re: Seemless rate adaptation

Otherwise the BT system will have to control the speed or buffer the data or drop the data.
Community Veteran
Posts: 3,366
Thanks: 15
Registered: ‎06-04-2007

Re: Seemless rate adaptation

Quote from: itsme
Otherwise the BT system will have to control the speed or buffer the data or drop the data.

Every digital data communications system on this planet includes [1] flow control and [2] collision/error detection. UDP packets make this a little harder, but not impossible.
Only BT implements this scheme, the LLU providers do not.
--
3Mb FTTC
https://portal.plus.net/my.html?action=data_transfer_speed
Community Veteran
Posts: 6,735
Thanks: 12
Registered: ‎02-02-2008

Re: Seemless rate adaptation

Quote from: godsell4
the LLU providers do not.

Being on an LLU circuit without an IP Profile I have to say there's no sign of the network failing, locally or generally.
The other protocols in the system deal with traffic more than adequately.  Wink
I'd love to see an explanation from a suitably-qualified person at BT to explain what value it has these days, for BT at least.
(or why they ever thought it would)
My suspicion is that it was designed to deal with a perceived problem that has long gone away (and may never have existed) and that they just couldn't drop it.
The "new" fixed % of sync speed version is effectively abandoning it without actually admitting so.  Lips are sealed