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Would a fixed SNR help?

Caerefail
Rising Star
Posts: 91
Thanks: 8
Fixes: 2
Registered: 07-09-2015

Would a fixed SNR help?

I hate REIN and SHINE  Cheesy
My line suffers from bad overnight REIN and SHINE, with the SNR dropping by up to 4dB, otherwise the line is stable. No phone noise and nothing in the house but we're fed by nearly 4km of overhead cable, which terminates on the same pole as a street light and our electric supply.
With a target SNR of (I guess) 9dB, the ADSL connection is lovely and stable, very few HEC errors or Error Secs. Example stats for 24 hrs below:
Mode: ADSL_G.dmt
Traffic Type: ATM
Status: Up
Link Power State: L0

Downstream Upstream
Line Coding(Trellis): On On
SNR Margin (1 dB): 8.3 10.0
Attenuation (1 dB): 48.5 30.5
Output Power (1 dBm): 19.9 12.3
Attainable Rate (Kbps): 6336 1072

Path 0 Path 1
Downstream Upstream Downstream Upstream
Rate (Kbps): 5472 896 0 0

K (number of bytes in DMT frame): 172 29 0 0
R (number of check bytes in RS code word): 14 16 0 0
S (RS code word size in DMT frame): 1.00 8.00 0.0 0.0
D (interleaver depth): 32 4 0 0
Delay (msec): 8.00 8.00 0.0 0.0
INP (DMT symbol): 1.20 0.09 0.0 0.0

Super Frames: 5249585 5249585 0 0
Super Frame Errors: 177 43 0 0
RS Words: 356971780 44668647 0 0
RS Correctable Errors: 2405139 526 0 0
RS Uncorrectable Errors: 1818 0 0 0

HEC Errors: 1494 37 0 0
OCD Errors: 1 0 0 0
LCD Errors: 1 0 0 0
Total Cells: 1151736928 0 0 0
Data Cells: 508791752 0 0 0
Bit Errors: 0 0 0 0

Total ES: 142 0
Total SES: 0 0
Total UAS: 0 0
BT Speedtest results to match these:
Best Effort Test:  -provides background information.
Download  Speed
4.73 Mbps

0 Mbps 7.15 Mbps
Max Achievable Speed
Download speed achieved during the test was - 4.73 Mbps
For your connection, the acceptable range of speeds  is 2 Mbps-7.15 Mbps.
IP Profile for your line is - 4.83 Mbps
2. Upstream Test:  -provides background information.
Upload Speed
0.77 Mbps

0 Mbps 0.83 Mbps
Max Achievable Speed
Upload speed  achieved during the test was - 0.77Mbps
Additional Information:
Upstream Rate IP profile on your line is - 0.83 Mbps
However, because this gives a stable line (those stats were from a representative 24 hrs in a 10 day connection period), any re-sync results in a reduction of target SNR (and a much improved speed  Smiley). However, because of  the nighttime REIN, errors increase significantly and the line can drop out, resulting in DLM eventually setting the target SNR at 12dB and line speed dropping so I have to go through a period of time with a much lower speed before eventually getting it back to a profile of around 4.8 to 5 Mbps. As an example, the router was accidentally turned off the other night, reconnected with a much lower target SNR producing the following stats in the last 24 hours:
Mode: ADSL_G.dmt
Traffic Type: ATM
Status: Up
Link Power State: L0

Downstream Upstream
Line Coding(Trellis): On On
SNR Margin (1 dB): 4.9 10.0
Attenuation (1 dB): 48.5 31.0
Output Power (1 dBm): 19.9 12.3
Attainable Rate (Kbps): 6840 1068

Path 0 Path 1
Downstream Upstream Downstream Upstream
Rate (Kbps): 6592 896 0 0

K (number of bytes in DMT frame): 207 29 0 0
R (number of check bytes in RS code word): 16 16 0 0
S (RS code word size in DMT frame): 1.00 8.00 0.0 0.0
D (interleaver depth): 32 4 0 0
Delay (msec): 8.00 8.00 0.0 0.0
INP (DMT symbol): 1.15 0.09 0.0 0.0

Super Frames: 5177603 5177603 0 0
Super Frame Errors: 17397 129 0 0
RS Words: 352076970 44055534 0 0
RS Correctable Errors: 19604716 776 0 0
RS Uncorrectable Errors: 180852 0 0 0

HEC Errors: 235643 128 0 0
OCD Errors: 46 0 0 0
LCD Errors: 46 0 0 0
Total Cells: 1368211616 0 0 0
Data Cells: 32583367 0 0 0
Bit Errors: 0 0 0 0

Total ES: 2259 0
Total SES: 270 0
Total UAS: 186 46
Best Effort Test:  -provides background information.
Download  Speed
5.7 Mbps

0 Mbps 7.15 Mbps
Max Achievable Speed
Download speed achieved during the test was - 5.7 Mbps
For your connection, the acceptable range of speeds  is 2 Mbps-7.15 Mbps.
IP Profile for your line is - 5.82 Mbps
2. Upstream Test:  -provides background information.
Upload Speed
0.72 Mbps

0 Mbps 0.83 Mbps
Max Achievable Speed
Upload speed  achieved during the test was - 0.72Mbps
Additional Information:
Upstream Rate IP profile on your line is - 0.83 Mbps
Now don't get me wrong, I love this download speed and would like to keep it, but experience tells me that eventually that error level will affect my profile and the speed will drop. I know that the line can be stable when the stats show a daytime SNR margin of 7-8 dB and this can give me an IP Profile of around 5Mbps. Is there anyway that the SNR margin can be fixed so that an accidental re-sync doesn't result in a lovely improved speed that eventually will end up below the optimal - if you see what I mean? Grin Or can the IP Profile be fixed in anyway - any suggestions gratefully received!
35 REPLIES
ian007jen
Rising Star
Posts: 392
Thanks: 4
Fixes: 2
Registered: 06-09-2007

Re: Would a fixed SNR help?

My best advise would be to reset the router, just turn if off then back on again once every 10 days or so at between 10 and 12 PM, at least you are on an on an ADSL2 exchange
Are you on an ADSL2 exchange or on ADSL MAX Premium?
Are you using a Plusnet supplied modem/router and is it in the master socket with a micro filter face plate ?
Ian
Caerefail
Rising Star
Posts: 91
Thanks: 8
Fixes: 2
Registered: 07-09-2015

Re: Would a fixed SNR help?

Exchange is ADSL2 but I'm on ADSL Max I guess - BTW line speed forecast is only 2.5Mb max so Plusnet don't put you on ADSL2.
Router is the horrid 2704n, so I can't run RSL but it does seem to be quite good at hanging on to the line. Connected to the master socket with a filtered facelate and bell wire disconnected.
Very happy with Plusnet up to now - a reliable 4.5Mb + download speed is brilliant compared to the 0.3 to 1.5Mb I was getting from my previous ISP.
Community Veteran
Posts: 26,718
Thanks: 931
Fixes: 10
Registered: 10-04-2007

Re: Would a fixed SNR help?

I doubt you are on ADSL Max - I'd think you are probably on 21CN WBBC and it's syncing as ADSL1 due to your distance from the exchange.
You can tell: run the BT diagnostic speed test. If it reports on download only you are on ADSL Max, if it reports on up and down you are on 21CN.
jelv (a.k.a Spoon Whittler)
   Why I have left Plusnet (warning: long post!)   
Broadband: Andrews & Arnold Home::1 (FTTC 80/20)
Line rental: Pulse 8 Home Line Rental (£13/month)
Mobile: iD mobile (£4/month)
Caerefail
Rising Star
Posts: 91
Thanks: 8
Fixes: 2
Registered: 07-09-2015

Re: Would a fixed SNR help?

Thanks. Router says Mode:  ADSL_G.dmt and BT diagnostic speed test info' is in all the stats blurb - this morning's result was:
Best Effort Test:  -provides background information.
  Download  Speed
  5.7 Mbps
   
0 Mbps  7.15 Mbps
Max Achievable Speed
Download speed achieved during the test was - 5.7 Mbps
For your connection, the acceptable range of speeds  is 2 Mbps-7.15 Mbps.
IP Profile for your line is - 5.82 Mbps
2. Upstream Test:  -provides background information.
  Upload Speed
  0.72 Mbps
   
0 Mbps  0.83 Mbps
Max Achievable Speed
Upload speed  achieved during the test was - 0.72Mbps
Additional Information:
Upstream Rate IP profile on your line is - 0.83 Mbps
So I assume it's 21CN WBBC?
jg321
Grafter
Posts: 49
Thanks: 1
Registered: 17-05-2015

Re: Would a fixed SNR help?

It'll be WBC on an ADSL1 (aka ADSL Max) profile.
Community Veteran
Posts: 5,169
Thanks: 478
Fixes: 20
Registered: 10-06-2010

Re: Would a fixed SNR help?

It's on G.dmt (ADSL1) because that's what Plusnet have ordered your line as, OK so they ordered it as that due to the estimated speed, which is mostly due to the distance from the exchange.
Plusnet could change it to ADSL2+, ADSL2 can be very stable on long lines, but of course you won't know if ADSL2 is more stable or less stable and if it's faster or slower on your line without trying it. Unfortunately a possible drawback of ADSL2+ is that the DLM is slightly different and has banded profiles, which it doesn't have on 21CN WBC ADSL1. I'd be inclined to try ADSL2, and if you can set the 2704N to ADSL1, then you can mostly switch it back to how it was before yourself (although the DLM would still be different). But it's your line so it's your decision, and Plusnet should be able to just do the fixed 9 dB target SNRM instead.
Caerefail
Rising Star
Posts: 91
Thanks: 8
Fixes: 2
Registered: 07-09-2015

Re: Would a fixed SNR help?

Thanks for your comments ejs and everyone. I think I'll see how things go for a bit, but I suspect that I may end up asking for a fixed SNR so I can stop having to monitor things all the time  Smiley
Caerefail
Rising Star
Posts: 91
Thanks: 8
Fixes: 2
Registered: 07-09-2015

Re: Would a fixed SNR help?

Just to update, as expected, line re-synced tonight and IP Profile is back to 4.8Mbps  Undecided
Community Veteran
Posts: 26,718
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Registered: 10-04-2007

Re: Would a fixed SNR help?

Quote from: jg321
It'll be WBC on an ADSL1

Correct. This is what you get on 21CN exchanges.
Quote from: jg321
(aka ADSL Max) profile.

Wrong! ADSL Max is a 20CN exchange feature.
jelv (a.k.a Spoon Whittler)
   Why I have left Plusnet (warning: long post!)   
Broadband: Andrews & Arnold Home::1 (FTTC 80/20)
Line rental: Pulse 8 Home Line Rental (£13/month)
Mobile: iD mobile (£4/month)
Caerefail
Rising Star
Posts: 91
Thanks: 8
Fixes: 2
Registered: 07-09-2015

Re: Would a fixed SNR help?

Right, as IP profile is now back to 4.8Mbs with a target SNRM of presumably 9dB, is there any way of getting a higher IP profile given the following stats from the router?
Downstream Upstream
Line Coding(Trellis): On On
SNR Margin (1 dB): 8.3 10.0
Attenuation (1 dB): 48.5 30.5
Output Power (1 dBm): 19.9 12.3
Attainable Rate (Kbps): 6460 1060

Path 0 Path 1
Downstream Upstream Downstream Upstream
Rate (Kbps): 5504 896 0 0
These are after a graceful disconnect this morning, following two overnight re-syncs.
Community Veteran
Posts: 5,169
Thanks: 478
Fixes: 20
Registered: 10-06-2010

Re: Would a fixed SNR help?

The IP profile is entirely dependent on the downstream line rate. 88.2% of 5504 is 4854, which will be rounded down to 4.8 Mb by Plusnet. Actual download speeds will be a little less due to the "Plusnet traffic management tax".
I'm not convinced the target SNRM is being changed by the DLM. The DLM wouldn't normally change it so often, and the DLM does not need to wait for you to do a re-sync to apply the new target SNRM.
Instead, the target SNRM might usually be 6. If the ADSL connects at a time when there's a lot of interference present, you'll get a lower speed. If the interference then goes away, the current SNRM would then rise above 6.
The target SNRM can only be set to 3, 6, 9, 12 or 15. If you want it more stable, Plusnet would have to fix it at 9. If you want more speed, Plusnet would have to fix it at 6, although there could potentially then be times when the CRC / uncorrected error rate gets so high it will result in slow and unreliable download speeds.
Caerefail
Rising Star
Posts: 91
Thanks: 8
Fixes: 2
Registered: 07-09-2015

Re: Would a fixed SNR help?

Okay, it's got me confused then. I know when the router was turned off the other day it reconnected in the morning with a daytime SNRM of around 5dB, which is too low to maintain a connection with the nighttime noise that we get.  It was steady during the day but as expected, it dropped connection overnight and when I checked the stats next morning, after a deliberate graceful disconnection and reconnection, the SNRM was just over 8dB so something raised the SNRM. I know the daytime SNRM is pretty steady from monitoring it.
Anyway, even with a daytime SNRM of around 8dB, router stats are showing an attainable rate of 6424, whilst the downstream rate, which I know the IP Profile is based on, is only 5504, so I was wondering if there was anyway to get the downstream rate higher. I've done a graceful disconnect and reconnect but it didn't have any effect - would a full reboot of the router make any difference?
Community Veteran
Posts: 26,718
Thanks: 931
Fixes: 10
Registered: 10-04-2007

Re: Would a fixed SNR help?

The only way you could get higher speeds consistently is by finding out why the day/night SNRM varies so much and addressing the issue. That may not be possible.
The problem will be if you keep rebooting the risk is that the target SNRM will be set higher by the DLM and you'll get slower speeds. Your best bet is to accept whatever speed it settles at after a night time resync and then continually monitor the SNRM to see if there's a drop at a particular time that you can associate with something being turned on.
jelv (a.k.a Spoon Whittler)
   Why I have left Plusnet (warning: long post!)   
Broadband: Andrews & Arnold Home::1 (FTTC 80/20)
Line rental: Pulse 8 Home Line Rental (£13/month)
Mobile: iD mobile (£4/month)
Caerefail
Rising Star
Posts: 91
Thanks: 8
Fixes: 2
Registered: 07-09-2015

Re: Would a fixed SNR help?

OK thanks for your help. I know that there's nothing in the house that causes the nighttime noise because I've previously monitored the line with RSL (prior to moving to Plusnet) so I'll just have to live with it - as I've said before, 4.5Mb reliable download is a heck of a lot better than 1.5 dropping to 0.3 in the evening with my previous provider. Smiley