tertech
join:2008-04-12
Ottawa, ON
| ST516 - Strange discovery
For about the last year or so, I have been using the DMT tool to constantly adjust the target SNRM of my connection. With my attenuation of 63.5dB, I'm on a d2496/u640 Interleaved profile; but I can rarely keep sync active for more than a few minutes if I set an SNRM below about 15dB. This leaves me with a dl speed of around 850Kbps. Lately it seems to have gotten even more finicky and frequently losing sync unless I set the SNRM for the max of around 20dB with a resulting dl speed in the 700's. Even then it might re-sync every few hours.
After reading the other post here about how Teksavyy was reviewing their customer's line stats to uncover poor connections, I decided to do some of my own tests and log the results so that I would be prepared with a lot of stats to help with determining if my line should be serviced or my profile lowered. I even considered the downgrade to 512/512.
Anyway, in desperation last night I applied an engineering process of which the technical term is called 'monkeying'. I found a setting in the 'moptions2' tab of DMT to set the remote Tx power. Having absolutely no idea what that means (aside from the obvious), I moved the sliders from 'default' to about 3/4 the way between min and max. There are 2 sliders; both say 'REMOTE TX PWR'. One affects REG 0D and the other REG 0E. With that 3/4 setting, I also set the SNRM to around 12dB and synced at about 1.2Mbps. This morning I checked the log and found not a single re-sync disconnect all night. 
Could that have been my problem all along? Unless someone can tell me exactly what those settings should be, or at least point me at a process to determine the best settings, I will keep tweaking them in small increments and also set lower SNRM targets until I start to see re-sync disconnects; then I'll back off to the previous setting that worked.
It looks encouraging! |
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GearHead360
join:2002-12-14 | I have a ST516 & ust DMT. How are you able to adjust your SNRM? The option isn't there other than trying to resync. |
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justsomeguy
join:2007-10-08
London, ON
| reply to tertech
Instead of monkeying around like this I would suggest
opening a ticket in the teksavvy DIRECT area and asking
if there is a remote you can be put on or if they can
have a tech look at your line.
I wouldnt put up with what you are having to put up with and maybe I would go as far as looking into cable if nothing could be done. |
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tertech
join:2008-04-12
Ottawa, ON
1 edit | reply to GearHead360
said by GearHead360  :I have a ST516 & ust DMT. How are you able to adjust your SNRM? The option isn't there other than trying to resync. Under [Special][Misc. Options/Settings] is a checkbox "unlock experimental area". If this is gray, then your firmware doesn't support this feature. At some point in the SGT release cycle they thought it was a bad idea to empower their customers and removed this feature. You could downgrade to an earlier release, but unless you're having line difficulties there's no reason for you to do this. |
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tertech
join:2008-04-12
Ottawa, ON
| reply to justsomeguy
said by justsomeguy :Instead of monkeying around like this I would suggest opening a ticket in the teksavvy DIRECT area and asking if there is a remote you can be put on or if they can have a tech look at your line. I wouldnt put up with what you are having to put up with and maybe I would go as far as looking into cable if nothing could be done. Instead of 'monkeying' if I called it 'empirical testing' would that be better?
I've gone through a few tickets. A Bell tech comes to my house with a voltmeter and says the line is fine. When they did bring a DSL line tester, all that they could suggest was a lower profile. My suspicion is that there might be a different solution with fine tuning my modem.
I'm on the closest remote that's less than a Km from me in a straight line - but my wires go over 5Km to get there. 
I used to have Roger's cable TV & Internet. I switched to StarChoice and Teksavvy because I was sick of being reamed. Going back to cable would be my last resort, right behind dial-up. |
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Bicephale
join:2005-09-24
 ·TekSavvy Solutions..
| reply to tertech
Hi TerTech,
I published a .GIF animation showing how the
"Noisemargin" gliding cursor has worked for me:
%20.GIF)
From the ground up!, Bicephale, 2008-Aug-26
Such an experiment just wasn't possible when i
tried to move the cursor at my former location
(it only produced random results) but here, in
Quebec city, its behaviour changed radically:
i can now observe a smooth progression between
the SNRM vs RCO (Connection Speed) poles... It
would seem a better RCO obtained at the cost of
a lower Connection Speed could lead to a better
Final "browser" Speed, in addition to improved
noise/latency figures. I'd call this finding
the Sweet Spot, others may prefer "Monkeying":
%20.GIF)
From the ground up!, Bicephale, 2008-Sep-27
%20.GIF)
From the ground up!, Bicephale, 2008-Sep-27
The remote transmission power level setting did
not work for me but perhaps the conditions are
not right. In your case anyway, i'll bet it's
contributing to some noise reduction which may
translate into a lower DownStream RCO figure...
My advice is to keep an eye on the RCO and Error
rate measurements while you experiment further!
Can you mention your exact FirmWare version please? |
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tertech
join:2008-04-12
Ottawa, ON
| Hi Bicephale,
I don't believe there's anyone here who has done more meticulous research into the modem behavior than you. Thank you for sharing all that fine work. 
I say that I'm 'monkeying', but actually my current job is in satellite communication - so I understand the basic principles. What's the difference between 5Km of copper and 36000Km of space?
I'm using ST516 v6.1.0.5.0 and DMT v7.33 (2007.07.28). I notice on your screenshot of DMT, your modem options only go to Reg 0A; you see on mine that they go to REG 0F. The remote Tx Pwr setting appears to change Reg 0D & 0E.
So far, with the setting shown on my screenshots I've been running for 2 hours without a re-sync disconnect. |
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Admiral Mike
join:2005-12-20
Hamilton, ON | reply to tertech
Quick question. I'm switching to TS when my Bell cancellation date nears, is the ST516 a good modem to get? I would get it through TS as well. |
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Scoop
join:2006-08-05
Ottawa, ON | Yes, the 516 is a good modem. You can get it elsewhere for less money. |
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jfmezei
Premium
join:2007-01-03
Beaconsfield, QC
·ELECTRONICBOX
| reply to tertech
I have a question for which I never got an answer:
With dial-up modems, the connection speed was negotiated between the 2 sides. (and then the various MNP capabilities.
With ADSL, I was under the impression that the connection speed was dictated by the DSLAM and that end user's modem didn't negotiate the speed.
Many here have pointed to the speedtouch having some magical ability to lower the negotiated speed to get a better SNR, which doesn't seem to be present in any other modem.
Does the speedtouch truly tell the DSLAM to not go higher than X speed ?
Or is the actual ADSL speed still dictated by the DSLAM, and the speedtouch simply adjusts the throughput to a lower value, hoping that this will result in fewer errors (aka: time gaps between packets instead of having packets one after the other) ? |
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tertech
join:2008-04-12
Ottawa, ON
4 edits | said by jfmezei :I have a question for which I never got an answer: With dial-up modems, the connection speed was negotiated between the 2 sides. (and then the various MNP capabilities. With ADSL, I was under the impression that the connection speed was dictated by the DSLAM and that end user's modem didn't negotiate the speed. Many here have pointed to the speedtouch having some magical ability to lower the negotiated speed to get a better SNR, which doesn't seem to be present in any other modem. Does the speedtouch truly tell the DSLAM to not go higher than X speed ? Or is the actual ADSL speed still dictated by the DSLAM, and the speedtouch simply adjusts the throughput to a lower value, hoping that this will result in fewer errors (aka: time gaps between packets instead of having packets one after the other) ? I can't say with any authority how an ADSL connection is negotiated. I believe the DSLAM profile determines the maximum speed. The other modems that I have tried ( a 2Wire and a SpeedStream ) seemed to connect at that max profile speed; even if it resulted in a 6dB SNRM. Apparently that 6dB figure is the minimum acceptable number for a connection. I don't know if the 2Wire or SpeedStream would negotiate a slower speed if that 6dB margin could not be obtained. I never saw it happen in the short time I used those modems. They just kept dropping sync over and over.
I don't know if the ST516 has any magic in it. I do know that the ability to set a target SNRM was removed in later firmware versions; somebody at SGT didn't think it was a good feature.
As I set the target SNRM lower and lower, I see an increase in the connection speed and an accompanying increase in the frequency range. I guess this means that the ST516 is actually changing the negotiated modulation frequency range rather than some trick of spacing out the data stream. We have a radio station in Ottawa CFRA that broadcasts at 580kHz: sometimes I can actually hear it on my telephone handset. That frequency stomps right on the middle of the ADSL band. If I do go higher than that I see a notch at 580kHz. |
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TilhasBB
Formally Goden99
Premium
join:2000-08-05
canada
| reply to tertech
I would recommend you try different firmwares. Some of them are already tweaked nicely.
I would try the following ones.
7.4.4.7
5.4.0.14
Or the 6.2 UK Firmware
In that order
Bicephale has a nice post on where to find them
»Thomson SpeedTouch 5x6v6 FirmWare v6.2.H (v6.2.17.5) |
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tertech
join:2008-04-12
Ottawa, ON
| said by TilhasBB :I would recommend you try different firmwares. Some of them are already tweaked nicely. I would try the following ones. 7.4.4.7 5.4.0.14 Or the 6.2 UK Firmware I tried v7.417 because it was supposed to be so much better on marginal lines. It did the same as the 2Wire; it connected at the max profile speed. If I remember correctly, the SNRM was up around 8 or 9dB. Not that it mattered very much, it kept disconnecting and re-syncing every few minutes. The DMT ability to adjust the SNRM is not in that version; I went back to 6.1. The modem came with v5.4; I upgraded it to the current 6.1 at some point. I really didn't see any big difference in stability from v5 to v6. I haven't tried the 6.2 UK firmware.
I'll finish my little experiment with the Remote Tx Pwr first. and then start trying the other firmwares you recommended. Thanks for the suggestion.
As of now... 6 hours at 1664kBps 12.5dB SNRM without disconnect. Time to push the SNRM a little lower |
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Shikomu
join:2007-11-16
Ontario
| tertech:
Our lines are very similiar. Ive been testing the 7.4.4.7 for the last week and its very good it pushes your SNR up almost 2 DB. What I didn't like is if there was some DSL noise out there at night and errored sec. started it would re-sync. It was annoying. It would resync every evening at least once. So I'm also playing with open firmware 6.1.0.5. I have noticed the TX power in DB goes lower or higher depending on the speed you are syncing when you change your SNR. Mine is 17DB yours is 14 DB but I set the PWR to Max or MIN and it had no affect so I'm not sure yet. I'm also tweaking. See your bottom graph (Loop Length) mine is a bit longer than yours. When you lower your SNR and increase your speed does your TX Power go up to 17 DB like mine ? |
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tertech
join:2008-04-12
Ottawa, ON
| said by Shikomu :tertech: Mine is 17DB yours is 14 DB but I set the PWR to Max or MIN and it had no affect so I'm not sure yet. I'm also tweaking. See your bottom graph (Loop Length) mine is a bit longer than yours. When you lower your SNR and increase your speed does your TX Power go up to 17 DB like mine ? I've just gone to 'Max Power' too ( wasn't that a Simpson's character? ). I'll start taking tiny steps in lowering the SNRM then waiting several hours with no re-syncs before trying the next step. I just went to 2080kBps @ 12dB. I do notice the tx pwr has gone up to 16.0dBm; we'll see if and when I get to 2208kBps like you if the tx pwr goes to 17dBm.
What happens to you if you put the Remote Tx Power settings back to 'default'? I instantly go back to crappy connection.
This is all very encouraging. Over the last week or so Ive torrented a lot ( of Linux distros, ahemmm ). It was pathetic at 700kBps even with s/l MLPPP. |
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Bicephale
join:2005-09-24
·TekSavvy Solutions..
| reply to tertech
Hi TerTech,
Thanks for your motivating comment, as an ordinary
DSL customer i do little more than to simply use a
set of utilities which are at everyone's disposal.
Well, i guess it's true that some individuals might
risk to regress after a while when doing this but i
find "empirical testing" much more suitable myself!
About the difference between copper vs empty space,
i'm thinking about parasitics right away but maybe
you just refer to the "monkeying" work required...
It didn't occur to me i couldn't define MoDemOption
register #0Bh (and beyond) until you mentioned this
detail to me. Possibly, that's only a result of the
character set used by 'DMT' but there's a chance it
is why i couldn't set the Remote Tx Power level (?).
This reminds me of a link i gave to KPaul anyway:
»Re: SpeedTouch 516 Tweaking :)
I wonder if you wouldn't benefit from exploring the
matter since this post dates back to mid-2005: i'd
bet the author owned similar HardWare to your own.
In any case, having no resets sure is a good thing;
oh, and PLEASE keep posting as i'm finally learning
from the late new input! My situation was different
if we consider that i had lots of noise while you're
having lots of attenuation... This could be another
reason why i went nowhere trying to adjust my Remote
Tx Power level, i don't know, but i wouldn't be too
surprized if your "sweet spot" happens to gravitate
around an SNR Margin of 12 dB. Look at my capture:
%20.GIF)
'RouterStats-Lite v3.5' as a Trouble-Shooting Tool, Bicephale, 2008-Sep-14
The part marked "Disruption" was when my downstairs
neighbour walked into her kitchen and lighted up a
noisy dimmer (so it seems); you can see my ST546v6
trying to synchronize again but to no end. Then, i
used a stable tweak for a while and started looking
for a sweet spot before that noisy event ended (the
constant-slope sections). It's clear on my high-res
version of this capture that the MoDem reconnected
past 10.5 dB - but it was still resetting frequently.
13 dB was conservative, 12 dB would have been edgy.
This other capture clearly illustrates how my ST546
once just failed to gracefully "Fall-Back" far enough:
%20.GIF)
'RouterStats-Lite v3.5' as a Trouble-Shooting Tool, Bicephale, 2008-Sep-12
It continuously targetted around 4 Mbps/9 dB instead!
I keep my fingers crossed wishing that you can have
a stable connection well below the 12 dB mark but i
am sceptical. By the way, i explicitely associated
my last capture to FirmWare v7.4.4.7 so i feel this
one may be fine only until it hits the 12 dB barrier in
presence of strong noise...
 |
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Bicephale
join:2005-09-24
·TekSavvy Solutions..
1 edit | reply to jfmezei
Hi JFMezei,
With DialUp devices you could define the negociated
speed directly, with DSL MoDems you might find that
what is done actually refers to a form of Spectral
Shaping where the customer has some control over a
few parameters such as the Bits-per-Bin setting and
the Coding Gain which are available to GNet owners
only and maybe some others but not that's not to be
found in a Thomson ST5x6: i would have noticed!!!
Better Spectral Shaping control is allowed with the
3Com USR-910x products but i've never been able to
see one single capture which could seem conclusive.
If we were able to raise our profile ourselves this
would be called hacking, actually, and it's not open
for discussion - which doesn't matter as it doesn't
work like that even if you try very hard. All we do is
trade-off (sacrifice) some speed for more stability
instead of having Bell involved in a gross way...
Addendum:
"De-Luxe" Spectral-Shaping:
SpeedTouch 516 Tweaking :), Bicephale, 2008-May-8
GNet Tweaking:
Need help/tips about DSL connection speed, Bicephale, 2008-May-25
The Trade-Off:
Stats help from someone at Teksavvy, Bicephale, 2007-Jul-24
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jfmezei
Premium
join:2007-01-03
Beaconsfield, QC
·ELECTRONICBOX
| Bicephale, I was not suggesting hacking to raise one's profile.
With MNP modems, they would automatically retrain down to a lower speed when conditions were bad, and then retrain back up when conditions imporved, and you could set a ceiling for negotiations.
For instance, when I was in australia, I would connect back to my system via long distance dial-up with an accoustic coupler on a public payphone. I found it was faster to limit my tiny modem to 2400 baud than to let it negotiate higher speeds and spend time retraining down and up again.
From Rottness Island On the indian Ocean near perth (about as far as one could get from Montreal on the planet), I was able to get a usable 14.4kbps connection over a payphone. But from other places, 2400 was barely usable.
Now, back to DSL: does the client modem really have the ability to tell the DSLAM to use a lower speed than is provisioned ?
Or is the signal still saying 5056000 bps but because of blocked frequencies, the actual throughput is less ? Or does it actually negotiate a lower speed ?
And can the modem do this dynamically as conditions change, (like MNP modems) or once synched, it remains at those settings no matter what ? |
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tertech
join:2008-04-12
Ottawa, ON
| reply to tertech
10.5 hours at my max d/l profile speed of 2496 with no re-sync disconnects.
Now I'll leave it alone all day to test the effects of the diurnal variances such as cosmic rays, solar flares, moon gravity, whatever. The SNRM was 9.0dB last night when I finally went to sleep; this morning after sunrise it's down to 7.5dB but still hanging on to sync. I have the Tx Pwr set to MAX and it's showing 16.5dBm.
I dare not click that [DSL Resync] button for fear that my speed may come crashing down. |
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Bicephale
join:2005-09-24
·TekSavvy Solutions..
| reply to jfmezei
Hi JFMezei,
My reply of October 4 to TerTech (which refers to links
of September 27) lead to Bell portal captures where the
MoDem's peer didn't stick to some preset profile... The
ADSL standard is supposed to Fall-Back to a lower set
of speeds and then to recover as required but this just
won't happen when using a Thomson ST5x6, a Siemens
SpeedStream 4200 and i wouldn't even want to bet on
GNet's BB0060B and/or GBB2060-Xi for that. We're lucky
when a DSL unit provides some form of Spectral Shaping
and a lower UpStream rate would be most welcomed in
the present case, i believe. |
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