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ADSL2+ and min SNR

fredor
Grafter
Posts: 83
Registered: 05-04-2007

ADSL2+ and min SNR

Quote from: Peter

I think we should all be very clear that reduction of SNR (especially on ADSL2+) is not something that can be done 'on demand' from Wholesale, I'm sorry if you have been given the impression it can.  By your own admission you don't have a fault but clearly I'd like us to come to a reasonable understanding and I'd like your issue to be properly understood and investigated.  You have chosen to take part in the ADSL2+ trial and I suggest this conversation would now be better conducted in that arena rather than your becoming frustrated at our support staff who are following our standard processes.
http://community.plus.net/forum/index.php/board,62.0.html

Moving from ADSL with min SNR 9dB interleaved to ADSL2+ with min SNR 12dB no iterleaving has slightly reduced download performance. Is this to be expected?
Are you saying min SNR behaves differently on ADSL2+ and people 3km + from the DSLAM can expect a reduction in download speeds.
The change from 9dB to 12dB wasn't at my request so why was it done if it is so difficult to get it reversed?
Some information on what can be expected with ADSL2+ and SNR would be helpful.
According to the Kitz site I should have expected a slight improvement in download speed.
16 REPLIES
ctech500
Grafter
Posts: 255
Registered: 06-08-2007

Re: ADSL2+ and min SNR

Hi fredor
your snr is controlled by the DLM not Plusnet or BTW in might be possible to "tweaK" your SNR
Things do change when you move from MAX to ADSL2+ for one thing your Line Attenuation increases
The first thing you should do is post your router stats and i am sure the "experts" here will try and help you out
fredor
Grafter
Posts: 83
Registered: 05-04-2007

Re: ADSL2+ and min SNR

Hi ctech500,
Thanks for your interest.
SNR may well be controlled by DLM but as I understand it has to be requested though PlusNet.
Yes I can tweak my SNR and I did this regularly when on ADSL at a min SNR of 6dB. I had the min SNR increased to 9dB and this avoided tweaking.
Now I am on ADSL2+ with a min SNR of 12dB which I can tweak downwards but the problem is if the system reboots for any reason sync speed is lower and the IP Profife is lowered.
You are then stuck with lower download speeds until BT adjust your IP Profile.
A high sync speed is irrelevant with a low IP Profile.
Things did change when moving to ADSL2+.
Attenuation increased from 41dB to 43.5dB.
Interleaving was turned off and min SNR was increased to 12dB.
Upspeeds are excellent near to the max possible.
Current status is as follows:-
Status: ShowtimeRetrain Reason: 8000
Channel: FAST, Upstream rate = 1123 Kbps, Downstream rate = 6259 Kbps
Link Power State: L0
Mode:                  ADSL2+
Channel:                Fast
Trellis:                U:ON /D:ON
Line Status:            No Defect
Training Status:        Showtime
                Down            Up
SNR (dB):      11.6            6.2
Attn(dB):      43.5            21.3
Pwr(dBm):      0.0            13.0
Max(Kbps):      7264            1136
Rate (Kbps):    6259            1123
IP Profile is 4500kbps
Download speed 4078kbps
These are worse than achieved with ADSL except for upspeeds of course.
ctech500
Grafter
Posts: 255
Registered: 06-08-2007

Re: ADSL2+ and min SNR

ok
in my experience the best thing is to have interleaving set to auto. if you PM jamesh he will do that for you.
takes about 24 hours
Turning interleaving off will increase errors and DLM will raise the SNR  to ensure stability. this may also effect your sync speed
Moderator's note by David (spraxyt): removed large amount of white space to improve thread readability.
fredor
Grafter
Posts: 83
Registered: 05-04-2007

Re: ADSL2+ and min SNR

Thanks, following your suggestion, I have done this.
Superuser
Superuser
Posts: 9,136
Thanks: 546
Fixes: 46
Registered: 06-04-2007

Re: ADSL2+ and min SNR

Quote from: fredor
SNR may well be controlled by DLM but as I understand it has to be requested though PlusNet.
Things did change when moving to ADSL2+.
Attenuation increased from 41dB to 43.5dB.
Interleaving was turned off and min SNR was increased to 12dB.

No, the DLM controls the target SNR margin based on line conditions; this applied also on ADSL but the changes on ADSL2+ are more aggressively applied. There is ample evidence in this forum that automatic changes do happen, though the process can take a couple of weeks.
An increase in attenuation is to be expected on ADSL2+ because higher frequencies are brought into use. Attenuation at these higher frequencies is higher so the weighted average reported by the router is increased. The change you saw is normal.
ADSL2+ seems able to hang onto connections with lower SNR margins than ADSL. In fact the minimum target in its armoury is 3dB. It is possible the DLM will try 6dB and even 3dB on your line. If these generate a high number of errors the target will increase again within a day or so.
David
scootie
Grafter
Posts: 4,799
Registered: 03-11-2007

Re: ADSL2+ and min SNR

what are your error counts like?
Quote
Now I am on ADSL2+ with a min SNR of 12dB which I can tweak downwards but the problem is if the system reboots for any reason sync speed is lower and the IP Profife is lowered.

if you've got netgear you might want to check out the unoffical DGteam fimwares as these have snr tweaks that last a reboot Undecided but most defo a resync http://dgteam.ilbello.com/
tho you most likely all ready know that tweaking your margin your self might send the DLM in to shock and you end up with a even higher default noise margin.
i know you have a diff thread some where but at this time of the morning ive lost thee will to navigate the forum
if you havent all ready then i would surrgest trying to run http://www.vwlowen.co.uk/internet/files.htm or http://www.kitz.co.uk/routers/DMTv8.htm
on your router and see a more detailed picture of whats going on
ctech500
Grafter
Posts: 255
Registered: 06-08-2007

Re: ADSL2+ and min SNR

Quote from: ASBO

you most likely all ready know that tweaking your margin your self might send the DLM in to shock and you end up with a even higher default noise margin.

DLM dose tend to  "wobble" when tweaking the margin, I find it best to tweak it slowly I had a very high margin in the early days of the trial and i was beginning to think that DLM had "locked" on to the figure.
I also agree that anyone with a Netgear router ie DG834xx should use the DGteam Firmware it can work wonders with this pesky DLM system
fredor
Grafter
Posts: 83
Registered: 05-04-2007

Re: ADSL2+ and min SNR

Quote from: ASBO
what are your error counts like?

With the 12dB SNR on Fastpath, errored seconds are 0-6/15mins. Over the 24 hours, they will be maybe 200 or higher but most of these are when I am offline.
Quote from: ASBO
if you've got netgear you might want to check out the unoffical DGteam fimwares as these have snr tweaks that last a reboot Undecided but most defo a resync http://dgteam.ilbello.com/
tho you most likely all ready know that tweaking your margin your self might send the DLM in to shock and you end up with a even higher default noise margin.

I do have a Netgear DG834PN so thanks for the info on DGteam. It should be interesting.
I am going to try interleaving which in the past reduced errored seconds to virtually zero at 9dB on ADSL1.
I mainly run linux but I have a Windows Vista system and gave the DTM tool a quick try but it didn't recognize the modem.
scootie
Grafter
Posts: 4,799
Registered: 03-11-2007

Re: ADSL2+ and min SNR

Quote
With the 12dB SNR on Fastpath, errored seconds are 0-6/15mins. Over the 24 hours, they will be maybe 200 or higher but most of these are when I am offline.

the levels of errors i get on 12db
Plusnet Staff
Plusnet Staff
Posts: 12,169
Thanks: 18
Fixes: 1
Registered: 04-04-2007

Re: ADSL2+ and min SNR

No idea what the target SNR is on my line at the moment and I'm not rebooting in case it isn't 3dB Smiley
With interleaving on my ine is perfectly stable, don't think I'd want to try it without. Interleaving is normally the first tool the DLM uses to try and improve stability, then the target SNR and last it uses banded profiles to cap the speed. I think I agree that switching interleaving on would be the best option and assuming it stays stable it then wouldn't take long to drop to a 9dB inteleaved profile. While we can change the interleaving status we have very little control over the target SNR. Even when we do change it, it doesn't get capped at that rate and can easily change again.
ADSL Statistics
Mode: ADSL2
Line Coding: Trellis On
Status: No Defect

Downstream Upstream
Rate (Kbps): 1952 908

SNR Margin (dB): 2.8 4.8
Attenuation (dB): 51.5 28.2
Output Power (dBm): 12.9 0.0

Super Frames: 23186828 23186826
Super Frame Errors: 8191 0
RS Words: 3014287746 197088021
RS Correctable Errors: 61563082 0
RS Uncorrectable Errors: 346598 N/A

HEC Errors: 5073 0
OCD Errors: 678 0
LCD Errors: 4 0
Total Cells: 1734417304 1150186
Data Cells: 18577953 3461
Bit Errors: 0 0

Total ES: 104280 0
Total SES: 1101 0
Total UAS: 471 0
fredor
Grafter
Posts: 83
Registered: 05-04-2007

Re: ADSL2+ and min SNR

According to jameseh, interleaving is now turned on although my Netgear DG834PN still shows channel = fast.
The errored seconds reported have reduced considerably and I now get 24ES in 19 hours so I guess interleaving must be on.
It will be interesting to see what happens from now on.
itsme
Grafter
Posts: 5,924
Thanks: 1
Registered: 07-04-2007

Re: ADSL2+ and min SNR

What you are looking for is D. If it's 1 and 1 then your are on fast path anything else you have interleaving.
Quote
Netgear DM111 ADSL2+ Modem
Software Version: 3.30j
Login name: admin
Password:
> adsl info --stats
adsl: ADSL driver and PHY status
Status: Showtime  Channel: FAST, Upstream rate = 816 Kbps, Downstream rate = 3655 Kbps
Link Power State: L0
Mode:                   ADSL2
Channel:                Fast
Trellis:                U:ON /D:ON
Line Status:            No Defect
Training Status:        Showtime
                Down            Up
SNR (dB):       12.1            6.2
Attn(dB):       50.5            29.3
Pwr(dBm):       0.0             12.4
Max(Kbps):      4560            816
Rate (Kbps):    3655            816
                        G.dmt framing
K:              14(0)           103
R:              16              16
S:              16              1
D:              16              8

fredor
Grafter
Posts: 83
Registered: 05-04-2007

Re: ADSL2+ and min SNR

My Stats are:-
Quote
adslctl: ADSL driver and PHY status
Status: ShowtimeRetrain Reason: 8000
Channel: FAST, Upstream rate = 888 Kbps, Downstream rate = 6582 Kbps
Link Power State: L0
Mode:                  ADSL2+
Channel:                Fast
Trellis:                U:ON /D:ON
Line Status:            No Defect
Training Status:        Showtime
                Down            Up
SNR (dB):      12.8            8.6
Attn(dB):      43.5            21.4
Pwr(dBm):      0.0            12.3
Max(Kbps):      7836            888
Rate (Kbps):    6582            888
                        G.dmt framing
K:              206(0)          14
R:              14              16
S:              1              8
D:              32              8
                        ADSL2 framing
MSGc:          59              10
B:              205            13
M:              1              8
T:              1              9
R:              14              16
S:              0.9966          4.0000
L:              1766            256
D:              32              8

D is 32  8 so I guess thats interleaving ON.
fredor
Grafter
Posts: 83
Registered: 05-04-2007

Re: ADSL2+ and min SNR

With interleaving on stats have improved significantly:-
Quote
adslctl: ADSL driver and PHY status
Status: ShowtimeRetrain Reason: 8000
Channel: FAST, Upstream rate = 888 Kbps, Downstream rate = 7645 Kbps
Link Power State: L0
Mode:                  ADSL2+
Channel:                Fast
Trellis:                U:ON /D:ON
Line Status:            No Defect
Training Status:        Showtime
                Down            Up
SNR (dB):      8.7            12.4
Attn(dB):      43.5            21.5
Pwr(dBm):      0.0            12.9
Max(Kbps):      8716            888
Rate (Kbps):    7645            888

Min SNR has now been reduced and the sync rate correspondingly increases.
Many thanks to ctech500.