G.DMT vs ADSL2+

[#1]

Hi,
I raised a fault a few months back when I suddenly kept loosing sync with the exchange, that problem went away but I have been baffled by the last few months over the various connection methods.
Its my understanding that G.DMT is the ASDL2 product which offered up to 8mbps, and ASDL2+ (G.992.5 I think?) offers upto 20mbps.
After reading various sources around the net, ASDL2+ works by utilising more of the available frequency on a line to give better throughput, so in theory should be the same or slightly better than G.DMT dependent on varying factors.  However I would not expect to see a drop in sync speed from using this protocol, which is what I allow the route to sync using multi-mode (chooses the best option for the line) or force it to G.992.5 which says it is using ASDL2+. 
I have manually altered this setting to G.DMT and I see higher sync speeds, not by a lot but the SNR Margin is at 5db instead of 12db for G.DMT and the noise level is at 49db instead of 43DB.
Any ideas on what could be causing this, and if my information above is correct?
Cheers
Minimos

[#2]

Just to clarify
G.DMT = ADSL 1
G.DMT.bis = ADSL2
G.DMT.bisplus = ADSL2+
If you change your router connection from ADSL2+ to ADSL1 your attenuation should drop as ADSL2+ uses the higher frequencies in calculating the attenuation and higher frequencies attenuate more although the difference is normally only about 3dB
The fact that the reported noise margin on resync changes from 5dB to 12dB is puzzling but may just be a sign that your connection has been banded which limits the sync speed regardless of the default noise margin
If you can post the full stats from your router (noise margin, speeds and attenuation) under the two conditions it may make it a bit clearer

[#3]

Hi minimos
Jim is spot on, the line is banded and your connection logs recently show lots of disconnections:
14:49 31/Aug/2010 N/A   0:35:8 (on going)
14:47 31/Aug/2010 14:48 31/Aug/2010   0:0:48
14:42 31/Aug/2010 14:45 31/Aug/2010   0:2:15
21:45 30/Aug/2010 14:39 31/Aug/2010   16:53:59
10:49 30/Aug/2010 21:45 30/Aug/2010   10:55:40
13:36 29/Aug/2010 10:48 30/Aug/2010   21:11:56
12:26 29/Aug/2010 13:36 29/Aug/2010   1:9:22
12:14 29/Aug/2010 12:26 29/Aug/2010   0:11:21
15:03 28/Aug/2010 12:14 29/Aug/2010   21:11:8
14:05 28/Aug/2010 15:02 28/Aug/2010   0:56:45
14:04 28/Aug/2010 14:05 28/Aug/2010   0:0:20
14:03 28/Aug/2010 14:04 28/Aug/2010   0:0:52
14:00 28/Aug/2010 14:02 28/Aug/2010   0:1:52
13:50 28/Aug/2010 14:00 28/Aug/2010   0:9:21
11:48 28/Aug/2010 13:50 28/Aug/2010   2:1:31
11:46 28/Aug/2010 11:47 28/Aug/2010   0:1:32
21:15 27/Aug/2010 11:37 28/Aug/2010   14:21:28
17:19 27/Aug/2010 21:15 27/Aug/2010   3:55:27
17:16 27/Aug/2010 17:19 27/Aug/2010   0:2:40
Which will result is this being lowered. The first thing I would do at this point is to look at your set up. Try it in the test socket, change filters etc.  to see if you can stabilise it in order for it to increase.
Your line is provisioned on ADSL2+ So any changes you make at your end will make little impact to the banded profile.
Jojo

[#4]

OK thanks for the replies.
The disconnections will have been me messing with the settings over the last few days, some of them a few moments after I set something just to see what the sync will have been,
I am going to disconnect again and set the modulation back to ASDL2+ and see if it increases over the next few days, if it doesn't I'll post some stats
Cheers
Minimos

[#5]

Ok, switched back to ASDL2+ and here are my stats:-

> adsl status
  --------------------------- ATU-R Info (hw: annex A, f/w: annex A) ---------
  Running Mode            : ADSL2+(G.992.5)      State                : SHOW
ME
  DS Actual Rate          :  4484784 bps  US Actual Rate      :  636000 bp
  DS Attainable Rate      :  4324000 bps  US Attainable Rate  :  1035707 bp
  DS Path Mode            :  Interleave    US Path Mode        :  Interleave
  DS Interleave Depth    :      128      US Interleave Depth  :        8
  NE Current Attenuation  :      49 dB    Cur SNR Margin      :        5  d
  DS actual PSD          :    19. 8 dB    US actual PSD        :    12. 6
  ADSL Firmware Version  : 2211201_A
  -------------------------------- ATU-C Info --------------------------------
  Far Current Attenuation :      26 dB    Far SNR Margin      :        8  d
  CO ITU Version[0]      : 00005453      CO ITU Version[1]    : 00005443
  DSLAM CHIPSET VENDOR    : < TI >
>

[#6]

Decided to get a baseline now, so switched back to G.DMT so I could post the stats.  Will switch again to ASDL2+ in a moment (Noting so that PN are aware for their connection logs)
> adsl status
 --------------------------- ATU-R Info (hw: annex A, f/w: annex A) -----------
  Running Mode            :    G.DMT       State                : SHOWTIME
  DS Actual Rate          :  4544000 bps   US Actual Rate       :   864000 bps
  DS Attainable Rate      :  5664000 bps   US Attainable Rate   :   996000 bps
  DS Path Mode            :  Interleave    US Path Mode         :  Interleave
  DS Interleave Depth     :       16       US Interleave Depth  :        4
  NE Current Attenuation  :       43 dB    Cur SNR Margin       :       11  dB
  DS actual PSD           :    19. 7 dB    US actual PSD        :    12. 3   dB
  ADSL Firmware Version   : 2211201_A
 -------------------------------- ATU-C Info ---------------------------------
  Far Current Attenuation :       28 dB    Far SNR Margin       :        9  dB
  CO ITU Version[0]       : 00005453       CO ITU Version[1]    : 00005443
  DSLAM CHIPSET VENDOR    : < TI >
As you can see a big difference in numbers.  If there any insights as to how things stand now I'm all ears.
***EDIT****
BTW, I did have it connected to the test master socket over the last few days whilst I have been experimenting, and it only lowers the attenuation by 1 or 2 db and still see the same range difference between modulation.  Appreciate all the tests I have done may have banded my profile so as mentioned above will keep current setup and leave for a few days to see if things improve.

[#7]

Hi,
Just updating the post, my connection has been up now for over 49 hours.  Posting latest router stats which show no change
> adsl status
  --------------------------- ATU-R Info (hw: annex A, f/w: annex A) -----------
  Running Mode            : ADSL2+(G.992.5)      State                : SHOWTI
ME
  DS Actual Rate          :  4234459 bps  US Actual Rate      :  636000 bps
  DS Attainable Rate      :  4244000 bps  US Attainable Rate  :  1029695 bps
  DS Path Mode            :  Interleave    US Path Mode        :  Interleave
  DS Interleave Depth    :      128      US Interleave Depth  :        8
  NE Current Attenuation  :      49 dB    Cur SNR Margin      :        6  dB
  DS actual PSD          :    19. 8 dB    US actual PSD        :    12. 6  dB
  ADSL Firmware Version  : 2211201_A
  -------------------------------- ATU-C Info ---------------------------------
  Far Current Attenuation :      26 dB    Far SNR Margin      :        8  dB
  CO ITU Version[0]      : 00005453      CO ITU Version[1]    : 00005443
  DSLAM CHIPSET VENDOR    : < TI >
Will continue to monitor over the weekend

[#8]

OK  I think there is starting to be a change on my line:-
> adsl status
  --------------------------- ATU-R Info (hw: annex A, f/w: annex A) -----------
  Running Mode            : ADSL2+(G.992.5)      State                : SHOWTI
ME
  DS Actual Rate          :  4000044 bps  US Actual Rate      :  714000 bps
  DS Attainable Rate      :  4472000 bps  US Attainable Rate  :  924134 bps
  DS Path Mode            :  Interleave    US Path Mode        :  Interleave
  DS Interleave Depth    :      96      US Interleave Depth  :        2
  NE Current Attenuation  :      49 dB    Cur SNR Margin      :        7  dB
  DS actual PSD          :    19. 0 dB    US actual PSD        :    12. 6  dB
  ADSL Firmware Version  : 2211201_A
  -------------------------------- ATU-C Info ---------------------------------
  Far Current Attenuation :      26 dB    Far SNR Margin      :        7  dB
  CO ITU Version[0]      : 00005453      CO ITU Version[1]    : 00005443
  DSLAM CHIPSET VENDOR    : < TI >
The SNR has gone up and the attinable rate for DS is higher even though my actual has dropped.  The US rate has also increased, along with a decrease to interleave depth.
Does this mean the DLM is working on my line, and if I continue to leave the connection sync (over 90 hours now) it should improve over the next week?
Cheers
Minimos