ADSL2+ - strange interferences?

I have ADSL2+ rate adaptive servie from polish provider Netia. I'm not complaining. I'm rather puzzled because I've observed strange interferences.

I know that SNR and thereby SNR margin fluctuates over the course of day and it's normal. However I thought that if I know actual synchronization rate and SNR margin I should predict what synchronization rate I will gain if I disconnect. However I have strange synchronization rates fluctuations. If I'm continously connected I don't have so much variations of SNR as I have when I'm reconnecting. As I am continously connected at 17800 kbps rate, SNR margin is never lower than 5.8 dB. Sometimes is about 7 dB. However I have often much lower SNR suddenly immediately as I reconnect. Then I have only 17000 kbps and SNR margin not higher than 6.8 dB. For example, during 10 minutes period if I'm continously connected my SNR margin is continously 6.1 dB. If I do many reconnectings at this period of time, I get either 17800 kbps at SNR margin 6.1 dB or 17100 kbps at SNR margin 6.3 dB. If they would be normal SNR fluctuations, then at 17800 kbps my SNR margin often dropped to 5.0 dB. I think they aren't normal ADSL interferences.

If i get lowered synchronization rate SNR margin immediately after reconnect is ALWAYS 6.3 dB. If I get 17800 kbps or higher SNR margin immediately after reconnect is ALWAYS 6.1 dB. There are more errored seconds when I have lowered synchronization.

Moreover, my ISP don't use DLM.

On this screenshot there are actual connection's characteristics. My distance from exchange is about 1.2 KM. This connection persit since 12 days. Despire SNR margin 4.2 dB I don't have disconnects, I have about 400 errored secons during 12 hours if average SNR margin is 4.4-4.8 dB. I have about 50 errored secons during 12 hours if average SNR margin is 6.0 dB.

Is it normal that sometimes SNR margin for download raised about 0.6 dB for 30 seconds or less? I know SNR margin fluctuates between night and day but I don't know whether it's normal that SNR margin fluctuates over such short time. Instead for upload SNR margin always fluctuates about 0.1-0.2 dB over about 15 seconds. Is it normal? Is it normal that my attenuation for G.DMT is 39 dB? I've read attenuation for G.DMT should be lower than on ADSL2+. On ADSL2 my attenuation is lower than on ADSL2+ however on G.DMT is much bigger (39.0 dB).

What screenshot?

What are the actual values of the Attenuations of the various ADSL Modes?

You do realise that once it has synced the sync speed will stay unchanged however the NM varies, until the next re-sync?

Screenshot:
http://img849.imageshack.us/img849/6942/e02g.png
I know that synchronization rate doesn't varies if I'm continously connected until I have SRA. I don't question about it.

Edited by konrado5 (Mon 09-Sep-13 22:00:58)

In reply to a post by XRaySpeX:

You do realise that once it has synced the sync speed will stay unchanged however the NM varies, until the next re-sync?

true for most UK adsl services, but:
OP says its a rate adaptive service in Poland, so it should/will change

Edited by ggremlin (Mon 09-Sep-13 22:05:26)

I thought ours was rate adaptive and that it adapts by re-syncing.

Post deleted by XRaySpeX

Here is screenshot:
http://img849.imageshack.us/img849/6942/e02g.png
I have the same synchronization rate until I reconnect. I question about something else. If I have at given moment 18200 kbps and SNR margin 6.1 dB, I expect as I reconnect I will gain about 18200 kbps. If I have at that moment SNR margin 5.0 dB I expect that if I reconnect I will gain lower synchronization rate eg. 15600 kbps. However I've noticed that often despire actual syncronization rate about 18000 kbps and SNR margin 6.1 dB if I reconnect I'll give 17100 kbps and SNR margin 6.3 dB immediately after reconnecting. For me that is strange phenomenon.

Why is my screenshot removed?

Rate adaptive is not the same thing as SRA (Seamless Rate Adaptation). It's unclear which the OP means.

Statistics -- ADSL

Mode: ADSL2+
Line Coding: Trellis On
Status: No Defect
Link Power State: L0

Downstream Upstream
SNR Margin (dB): 4.4 6.4
Attenuation (dB): 26.0 15.5
Output Power (dBm): 11.3 18.8
Attainable Rate (Kbps): 18000 1293
Rate (Kbps): 18607 1277
MSGc (number of bytes in overhead channel message): 68 16
B (number of bytes in Mux Data Frame): 254 39
M (number of Mux Data Frames in FEC Data Frame): 1 1
T (Mux Data Frames over sync bytes): 2 3
R (number of check bytes in FEC Data Frame): 0 0
S (ratio of FEC over PMD Data Frame length): 0.4377 0.9938
L (number of bits in PMD Data Frame): 4661 322
D (interleaver depth): 1 1
Delay (msec): 0 0

Super Frames: 2598803 69569626
Super Frame Errors: 443 17
RS Words: 0 0
RS Correctable Errors: 0 0
RS Uncorrectable Errors: 0 N/A

HEC Errors: 427 181
OCD Errors: 194 0
LCD Errors: 0 0
Total Cells: 1605556642 210813148
Data Cells: 977178250 72847995
Bit Errors: 0 242186

Total ES: 8587 258
Total SES: 0 0
Total UAS: 16 574