Noise margin problem & slow speed

[bobda]

You can force ADSL1 (G.dmt) at least until a reboot, on the sky dlink, using my router add-on: the installler is Java based so ought to run on a Mac, and it can temporarily upload a monitoring and noise margin tweaking program onto the router itself.

(I'm afraid there's a typo I missed in the set margin option - you need to select the "d.gmt" option then click resync.)

I have found that sky's dlm occasionally makes a change to adsl1 stick, but forcing adsl2+ got it using adsl2+ permanently again.

Mels router plugin version 0.04 - Mels

On the dlink, after uploading dgstats, it runs a second user interface on port 8888 by default. http://192.168.0.1:8888/

Thank you for this, I've uploaded the tool and it has been running allowing me to play with the router a bit - very useful.

When I resync choosing d.gmt or ADSL2 etc, what is the Traning Margin? This seems to have an effect on the sync speed and I can make the router connect at 2400 or so (on ADSL1) but the problem of the Noise Margin drop off as I have explained in this thread still exists.

These are the current stats;
ADSL Link Downstream Upstream
Connection Speed 2048 kbps 544 kbps
Line Attenuation 62.5db 31.5db
Noise Margin 5.8db 17.0db

[fuzzy logic]

When your router is establishing an ADSL connection, Sky's hardware sets it a target noise margin (normally 7dB), this allows the router some leeway to adapt for the normal day to day and morning to night variations in noise on the line.


The training margin setting allows you to override the target set by sky, the value is a percentage - a value of 100 makes no change ie uses the normal margin set by Sky (the adsl mode settings will still be applied), a value over 100 increases the margin (200 is approx 13dB) a value below 100 decreases the margin (1 is about 1dB) 0 is not allowed, but negative values are.

If your sync speed isn't capped, Increasing the training margin, will result in a lower sync/connection speed, which can improve stability and reduce errors, decreasing it increases sync speed but unless your line is very good will increase errors and make the connection less stable.

If your sync speed has been capped you won't be able to increase the sync speed, and you may also find small increases to the training margin just make the reported noise margin go up and you have to increase the training margin more than expected to make the sync rate actually fall.

Normally you won't want to change it, unless you either have an excellent line, or (like mine) a line that sometimes plays up, and you want to temporarily reduce the speed to get a more stable connection while playing games or in wet weather.

[bobda]

I've been using it to get the router to sync at a better speed. The results I posted in my previous post are about the best I've had out of it while still giving a reliable connection (speedtest.net results are a flat graph at 1.8Mb down and ping of 57ms). That's using a Training Margin of 50.

The ADSL stats tab shows;
adslctl: ADSL driver and PHY status
Status: ShowtimeRetrain Reason: 1Max: Upstream rate = 960 Kbps, Downstream rate = 2432 KbpsChannel: INTR, Upstream rate = 544 Kbps, Downstream rate = 2080 Kbps

Is there a way of improving my upload speed?

[bobda]

It seems that I'm stuck at a sync speed of 2000ish. Any higher and after 5 minutes, 10 minutes or sometimes an hour, the noise margin drops to -0.1 and the connection is dead. The upload speed is never more than 544 - is there anything I can do about that?

I've just logged into our modem at work which uses a bog standard ADSL connection and the stats are very interesting;

				Downstream	Upstream
		SNR Margin	:	2.7	4.8	db
		Line Attenuation	:	62.0	33.8	db
		Data Rate	:	5711	462	kbps

That's running ADSL2+ - look at the line attenuation and noise margin versus the connection speed. It's a BT broadband service and it's stable.

[IWasNotTheEnemy]

That's because the SNR is a LOT lower than Sky

[Isitme]

.....and if it is stable it shows it is a far better line than yours.

[bobda]

That's because the SNR is a LOT lower than Sky

Lower should be worse. High SNR = more signal and less noise.

[IWasNotTheEnemy]

Lower is worse unless the line is perfect

[Isitme]

Lower should be worse. High SNR = more signal and less noise.

Exactly, the lower the noise margin the higher the speed will be.

[bobda]

Exactly, the lower the noise margin the higher the speed will be.

So why is Sky's target noise margin 6.5? This BT connection runs fine and faster than mine with a similar attenuation and lower noise margin.