Skip Navigation


BT Wholesale ADSL2+ to go all cool
Tuesday 03 April 2012 20:47:22 by Andrew Ferguson

ADSL2+ has a lower power state available to it, which has the potential to save some 2.9 GWh/year for every million ADSL2+ lines in operation, and also make the task of running MSAN's in exchange buildings within their operating temperature range easier.

BT Wholesale ran a trial testing this low power (L2 mode) which is known as BT Cool Broadband on some 29 different types of ADSL2+ modem that ended in December 2011, and should at the end March 2012 have started a six week trial, prior to any launch of the mode across the network.

The low power mode should not result in the lose of any data with seamless transfers into and out of the mode, and will only be used if the amount of data across an ADSL2+ or ADSL2 line is below 128 Kbps. Once data transfer above this level is requested, the modem and exchange hardware will switch back to the full power mode.

In the low power mode the modem and MSAN can negotiate a lower rate, that for those who monitor their noise margin may result in higher than expected noise margins being reported when in the low power mode, compared to when working in full power mode.

To avoid lines that are switching in and out of the low power mode causing unneccessary crosstalk the low power mode is only entered after a period of time. The level of power reduction is also limited to a maximum drop of 10dB.

For those geeks amongst you there is the TR-202 document on Broadband Forum that goes into depth on how this mode works.

The power saving from an individual line seems insignificant, but when added up the potential is there for BT Wholesale to save several million pounds in electricity costs. Those addicted to monitoring the state of their broadband connection, just need to be aware of the effect this may have on router stats.

Comments

Posted by camieabz over 3 years ago
It should also mean greater longevity of equipment if it runs in low power more often. Less maintenance, less costs all round, and more time for engineers and support staff to focus on other things, or will the overall savings in this sense be negligible?
Posted by LeJimster over 3 years ago
Generally lower power = less noise. So in theory this should reduce crosstalk on full powered lines during periods where most lines are in a low powered state (night time).

Be did some tweaking to their ADSL2+ equipment the other month and I just realised the other day I'm synching 500k-1Mb higher than usual. So any improvements along these lines is welcome for us sub 8Mb users.
Posted by chris6273 over 3 years ago
What I don't understand is:

"Once data transfer above this level is requested, the modem and exchange hardware will switch back to the full power mode."

and...

"In the low power mode the modem and MSAN can negotiate a lower rate".


Now, does the modem resync the connection every time its throughput exceeds 128Kbps, or does it use 'Seamless Rate Adaptation' where the connection speed is increased without the need for the handshake?

I've read through that document but I couldn't find an answer to this question.
Posted by andrew (Favicon staff member) over 3 years ago
No resyncs as I understand it, as this would cause problems for things like audio streaming that took the bit rate above the low power threshold.
Posted by alwall over 3 years ago
Was this from 1st April?
Posted by nredwood over 3 years ago
@LeJimster I'm not sure what I'd look for, but I've seen no evidence of this on BE lines. May be able to comment further after reading the doc

@Andrew - would the end user see this in the stats. Reason for asking is I went to help a friend connect up a HH3 at the weekend and the stats showed the DS power to be 0db consistently. Personally, I suspect the HH3 and unfortunately didn't have time to connect the old one to check. Having seen this, it now makes me wonder
Posted by camieabz over 3 years ago
Interesting:

"Operators in several countries have indicated that there is a risk that some emerging high speed services (e.g. IPTV) could be adversely impacted by the use of the ADSL2/2plus L2 state (or mode) as currently standardised by the ITU-T Recommendations.
However, there is an opportunity to make significant savings in the electrical energy demand required to operate the network by enabling the L2 state...
Posted by camieabz over 3 years ago
...If the existing ADSL2/2plus L2 state is enabled by a Network Operator care must be taken that parameter values are set to minimise network harm, and the implementation guidelines herein should be used until improvements are made to the operational effectiveness of the L2 mode for ADSL2 or ADSL2plus."

So it would seem that it will work fairly seamlessly, but only if knowledgable techies set their parameters, and not political policies.
Posted by andrew (Favicon staff member) over 3 years ago
@nredwood The 0dB is usually a router bug

If it was low power mode, running a download would bring you out of low power and the power level would rise.
Posted by herdwick over 3 years ago
0.3 Watts per line average over a year. Probably small beer compared to end users turning their routers off when not in use, which presumably also saves on the DSLAM.
Posted by andrew (Favicon staff member) over 3 years ago
Switching router off would save more, and if going away for a week I do switch most of my kit off.

If the BT system can generate the savings they suggest, then why not go for it.

Remember it will possibly save aircon costs during the summer too.
Posted by herdwick over 3 years ago
Indeed worth doing, save a few million on power.
Posted by chrysalis over 3 years ago
it will also reduce crosstalk, shame this has came very late in the day tho as most adsl2+ exchanges will be getting FTTC I expect.
Posted by snadge over 3 years ago
Sky will welcome this with open arms seeing as they are already robbing most of their customers of speed cos of the PMM module of DLM in the ASSIA software restricting Output Power on lines in an attempt to further save money.
Posted by snadge over 3 years ago
...also, will the savings be passed onto us? I bet not.
Posted by andrew (Favicon staff member) over 3 years ago
DLM systems by their very nature will often mean a line connects at a slower speed than if the ADSL2+ CPE is left to free run. Benefit to consumer is less resyncs.

If Sky DLM over harsh, more harsh than BT Wholesale one? More harsh than Talktalk which has a tendency for 9db or 12dB targets?
Posted by snadge over 3 years ago
thing is customers are moving to sky having perfectly fine fast lines before for years on ADSL2+ with no "re-syncs" - then with SKY its much slower, a call to SKY can sort this out 50% of the time with a manual reconfig but depends on the rep
Posted by snadge over 3 years ago
Andrew Iam using chrome and I cant get the link to the PDF file above to open...is it broken?
Posted by chrysalis over 3 years ago
So is SRA coming as well for BTw adsl2+?
Posted by andrew (Favicon staff member) over 3 years ago
@snadge

PDF opens in chrome under windows fine, and on android it downloads fine.
Posted by Legolash2o over 3 years ago
This may be a silly question, but is it also possible for them not to provide power to the bell/ring wire? As well as saving energy it would also increase users broadband speeds.
Posted by Legolash2o over 3 years ago
Nevermind, it was a silly question, i was under the impression that it was power via the exchange/cabinet.
You must be logged in to post comments. Click here to login.