Noise Margin on new 21CN Connection

My line has recently been switched to 21CN equipment in my Market 1 exchange but I have yet to make make the jump to ADSL2+ and am wondering whether this would in fact be a good move.

Before the connection was switched, the downstream noise margin was a fairly steady 10dB with a router connection speed of 8128 kbit/s.

Since the switch the noise margin has risen to 15dB, although the connection speed is still almost the same (8064 kbit/s).

Router is a Thomson 546v6

Any advice would be gratefully received.

Some stats:-

Modemstate : Up
xDSL Type : ADSL
xDSL Standard : ITU-T G.992.1
xDSL Annex : Annex A
Channel Mode : Interleaved
Uptime (days hh:mm:ss) : 0 days, 2:26:20

Number of resets : 1

Total Available Bandwidth Cells/s kbit/s
Downstream : 19018 8064
Upstream : 2339 992

Intrinsic/Actual and Maximum Bandwidth % kbit/s
Downstream : 74 10848
Upstream : 86 1144

Bearer Generic Info Downstream Upstream
Margin (dB) : 15.0 11.0
Attenuation (dB) : 22.0 10.5
OutputPower (dBm) : 19.5 12.5

With the 22dB attenuation and 15dB SNR on ADSL Max you are getting full speed.

Moving to ADSL2+ will give a significant improvement in your downstream speeds - possibly 15 Mbps or probably even more along with an improvement in upstream too.

The DSLAM will eventually drop that down to 3.0db if the line is stable.

Mine is running on 3.0db and its far far longer than your line.

ISP may have the user on an like ADSL type profile, so may need the ISP to actually regard to an up to 16/20/24 speed option

Should run nice and fast though

Yes - still on ADSL (up to 8) profile but going for the regrade option.

So am I right in thinking that once the ADSL2+ regrade takes place the MSAN & Router will try to negotiate the highest stable speed possible and so the noise margin will reduce as this happens?

What threw me was the increased noise margin on the 21CN equipment - but I guess if the full 8064kbp/s is being achieved then there is no need for the margin to be any tighter.

Thanks for your help

The increased noise margin is taking up the slack cuz you're still on 8 Meg ADSL Max on a line capable of much more.

On ADSL2+ you should get 18 Meg @ 6 dB NM or even 19-20 Meg @ 3 dB NM which DLM on WBC will attempt if it is sufficiently stable.

In reply to a post by wolvesmad:

The DSLAM will eventually drop that down to 3.0db if the line is stable.

Mine is running on 3.0db and its far far longer than your line.

No it will not. If he remain on an 8Mbps product then it will stay at around that figure unless the total output power is also reducced which is unlikely.

If the OP moves to ADSL2+ the SNR will drop to probably 6dB to start.

So why did mine gradually go down from 12db to 3db AFTER I migrated to 21CN?

Absolutely no idea ... but if the OP remains on an 8Mb product there is no reason for his SNR to change significantly.

Cuz you were migrated to ADSL2+ WBC.

It is not sufficient for your exchange to be 21CN'ed but for your particular line to be moved to WBC from IPStream.

In reply to a post by dazzle39:

My line has recently been switched to 21CN equipment in my Market 1 exchange but I have yet to make make the jump to ADSL2+ and am wondering whether this would in fact be a good move ...

Any advice would be gratefully received.

It looks like you are on a great line - I would ask your ISP to move you to an ADSL2+ package ASAP

On my connection I was at 9dB originally, and on each re-sync it would jump to 12, 15, 18 and finally 21dB. Speed dropped to around 4 Meg. Mostly due to timing. I switched around the time of the Jubillee, and then there was the Euro 2012. Latency was pretty high in the evenings as a result.

Now on 3dB.

The OP should get close to full ADSL2+ speeds assuming all things go well.

Regrade order placed - should happen overnight.

I'll post some more line stats once the connection has settled down - should be interesting!

Thanks again for all the comments

Well, line now switched to ADSL2+ (which took longer than expected).

BUT I'm not convinced that everything is as it should be.

I know that I am only just into the so called 10 day 'training period' but ever since the connection was switched yesterday morning my router has not resynchronised once (apart from a H/W reset initiated by myself earlier today).

Connection speed has not risen above 3230kibs/s, NM is 31.5dB, the attenuation has actually dropped from ADSL to 21.5dB. Routerstats showing everything stable, no errors etc.

I would have thought that the line would have synced at a higher level, or at least DLM would have brought the NM down, forcing the connection to resync by now.

Am I being impatient, or is something wrong?

Router stats as follows (ST 546v6)

Modemstate : Up
xDSL Type : ADSL2+
xDSL Standard : ITU-T G.992.5
xDSL Annex : Annex A
Uptime (days hh:mm:ss) : 0 days, 1:11:19

Number of resets : 1

Total Available Bandwidth Cells/s kbit/s
Downstream : 7617 3230
Upstream : 1535 651

Intrinsic/Actual and Maximum Bandwidth % kbit/s
Downstream : 27 11856
Upstream : 100 648

Bearer Generic Info Downstream Upstream
INP (DMT) : 1.15 2.03
Delay (ms) : 7.52 7.95
R : 16 12
Margin (dB) : 31.5 10.5
Attenuation (dB) : 21.5 11.0
OutputPower (dBm) : 0.0 9.5

Vendor Chipset Local Remote
Country : B5 B5
Vendor : BDCM IFTN
VendorSpecific : 0000 BE71
StandardRevisionNr : 00 02
Vendor System
Country : 0F 00
Vendor : TMMB ----
VendorSpecific : 3C61 0000
StandardRevisionNr : 00 00


Transfer statistics
Errors
Received FEC : 0
Received CRC : 0
Received HEC : 0
Transmitted FEC : 0
Transmitted CRC : 0
Transmitted HEC : 0

Near end failures since reset
Loss of frame : 0 failures
Loss of signal : 0 failures
Loss of power : 0 failures
Errored seconds : 0 seconds

Near end failures last 15 minutes
Loss of frame : 0 seconds
Loss of signal : 0 seconds
Loss of power : 0 seconds
Errored seconds : 0 seconds

Near end failures current day
Errored seconds : 0 seconds

Near end failures previous day
Errored seconds : 0 seconds

The BT Wholesale 10 day training period DOES NOT FORCE RESYNCS.
Time for you to reboot it and see if the spare margin is converted into sync.

Changes in the TARGET noise margin (rather than the one displayed) only come into effect the next time the modem resyncs.

I have rebooted the modem as suggested.

Resync has resulted in the noise margin remaining the same but an even lower sync rate?!

Not sure what is going on here - is it an ISP issue (ENTA) or a line problem - which appears very stable and 'noise' free.

Confused!!

Current stats below

Modemstate : Up
xDSL Type : ADSL2+
xDSL Standard : ITU-T G.992.5
xDSL Annex : Annex A
Uptime (days hh:mm:ss) : 0 days, 0:02:35

Number of resets : 1

Total Available Bandwidth Cells/s kbit/s
Downstream : 5450 2311
Upstream : 978 415

Intrinsic/Actual and Maximum Bandwidth % kbit/s
Downstream : 22 10092
Upstream : 98 420

Bearer Generic Info Downstream Upstream
INP (DMT) : 0.00 0.00
Delay (ms) : 0.24 0.24
R : 0 0
Margin (dB) : 31.0 17.0
Attenuation (dB) : 21.5 11.0
OutputPower (dBm) : 0.0 9.5

Vendor Chipset Local Remote
Country : B5 B5
Vendor : BDCM IFTN
VendorSpecific : 0000 BE71
StandardRevisionNr : 00 02
Vendor System
Country : 0F 00
Vendor : TMMB ----
VendorSpecific : 3C61 0000
StandardRevisionNr : 00 00


Transfer statistics
Errors
Received FEC : 0
Received CRC : 0
Received HEC : 0
Transmitted FEC : 0
Transmitted CRC : 0
Transmitted HEC : 0

Near end failures since reset
Loss of frame : 0 failures
Loss of signal : 0 failures
Loss of power : 0 failures
Errored seconds : 0 seconds

Near end failures last 15 minutes
Loss of frame : 0 seconds
Loss of signal : 0 seconds
Loss of power : 0 seconds
Errored seconds : 0 seconds

Near end failures current day
Errored seconds : 0 seconds

Near end failures previous day
Errored seconds : 0 seconds

SNR Margins have not remained the same - are they being reported correctly as upstream and downstream margins? Sometimes certain routers will report them the wrong way round...

Downstream SNR Margin since change to ADSL2+ has been 31 or 31.5 (was 15 on ADSL after switch to 21CN MSAN)
Upstream SNR Margin has changed from 17 to 10.5 (was 11 on ADSL as above)

I see no reason to think that the router is reporting these the wrong way round. Is there a way to check?

Sorry must have misread your stats: looked like the reported adsl2+ upstream margin had changed from 10.5 to 17

Edit: please see Mr. S's reply to me which may have been intended for you

Edited by 4M2 (Wed 18-Jul-12 18:13:27)

Get ISP to request a reset of DLM or removal of the banding that may have been applied to the line.