How to make ADSL connection faster? SNR tweak!

First of all please excuse me for a catchy title- it's meant to attract attention therefore it's not exactly sincere

This post describes and SNR tweak that might speed up your ADSL connection under certain circumstances- otherwise it's useless.
It also has some limitations. All of those are addressed below.

1. SNR tweak works on modems based on Broadcom chipset (some or most made by Netgear, Billion, TP-Link, or branded Speedtouch)
2. It doesn't work on those Broadcom-based modems that had the command deliberately disabled
3. The tweak will keep working only until modem reboot

Some theory on what you are about to do

SNR is Signal to Noise Ratio- a parameter that describes ratio that the ADSL signal has to maintain "over" background noise of the line.
Typically it is set to 6db (on a normal good quality line) although it might be significantly higher on poor lines with lots of noise.

Since no one is interested in technical jargon- let me describe it in a different way. Imagine that the ADSL signal is a plane flying over the sea and the sea would be the noise. 6db SNR is the hight over the sea that the plane maintains. For the sake of argument let's assume the lower the plane flies the faster if flies (your connection is faster with a lower SNR margin).

Now- if the sea is calm you can fly at very low altitude and therefore fly faster and everything is fine, however if the sea gets choppy there is a risk of a big wave hitting the plane and which ends the flight (meaning the ADSL disconnects). That's why with a high noise aka wave you need higher margin (you need to farther from the wave) which in turn reduces speed.

Some lines tend to have a constant noise- it's always the same- in which case you can lower SNR so it was just above the noise level and maintain higher speed. Other lines get choppy- for example after the rain has fallen noise might increase- so if you keep you SNR too low the line will keep disconnecting.

Another point is that with lines that are very choppy- modem sometimes sets SNR ratio too high, just to be on the safe side- that may mean SNR of even 18db which will cost you a good few mbps. That might or might not be relevant depending on how fast your connection speed is.

This tweak is particularly helpful for those who have slow connections- in such a case another 2 or 3mbps might almost double the connection speed- again assuming the SNR is set too high.

Implementing the tweak

Now onwards- how to implement the tweak. Remember that it vanishes once modem is rebooted so if you overdo it an your modem keeps disconnecting, you don't have to worry about reversing the procedure- just reboot the modem.

First you need a Putty or a similar app.



Type in an IP of your modem, click OPEN and once the connection is granted type username and password (note that it might not be the same username and password you use to log in to the modem via the browser- that depends on a device and manufacturer)

Once you've logged in type in a command adsl configure --snr XX or adslctl configure –snr XX (depending on a modem- both do the same thing)
Instead of XX is the percentage value of your normal 6db margin. So 6db is 100%. If you type 60 like I did you should get SNR of roughly 3.6db
(in my case I started with 6.1db and went down to 3.8db)



The percentage denominator works for 6db SNR margin which is normal one however if your SNR is significantly higher it might or might not work just like that.
If it doesn't work use these values:
To decrease SNR by 6db type adsl configure --snr 65550
To decrease it by 9db type adsl configure --snr 65500
To decrease it by 12db type adsl configure --snr 65450

Once you type the command and press enter you get no confirmation (as seen on the screen above) but the ADSL connection will disconnect and synchronize again.

Results and final thoughts

This is what I started with- standard SNR of 6.1db and connection speed according to speedtest of 12.99mbps



And that is whiat I ended up by changing the margin- SNR of 3.8db and speed according to speedtest of 14.09mbps



While I realize that 1.1mbps increase (or 8.5%) is not a dramatic one, you have to consider the fact that it is a free tweak, it takes only a minute to implement it's risk-free as it's very easy to revert (by rebooting the modem) and mostly- that it's not really meant to benefit people like me.
I've had normal SNR to start with so I did not have too much to gain. If yours is significantly higher for some reason (i.e. 12db) and your connection is still stable with much lower SNR (i.e. 6db), you are going to gain a lot more than I did especially relative to your connection speed (but also more in terms of mbps).

Please remember that setting SNR too low will result in frequent disconnections. This is far more annoying than a slower connection but still doesn't mean the tweak is not for you- it just means that you went too low with SNR setting and you should change the value (i.e. going from 18db to 9db might be too much, but going "only" to 12db might be stable, yet faster).

Last but not least- there are few modems that allow this tweak to be applied from firmware level (Billion) and there are apps that might make it easier for you for example DMT Tools or RouterStats. These tools don't work on all modems though- while doing it manually works on every one that runs a busybox and allows these commands.

 

To follow up on my own post- I would like to stress how important is it to buy ADSL modems that are based on a good chipset. Believe it or not there's only one maker of good ADSL modem SoCs- that is Broadcom. TI, Connexant or TrendChip are just crap.

Broadcom offers both the best speeds with good quality lines and best stability with poor quality lines not to mention advanced options to tweak the connection as described above.

The reason I mention it is because my ADSL modem that I used when writing the piece above started dying on me recently. It was a good Broadcom based ADSL modem-router that had worked fine for 4 or 5 years. When the speed started declining and my ISP couldn't diagnose the problem I borrowed a replacement modem that worked better.

I used the replacement for a while (Siemens based on TrendChip) and went on to buy another Broacom-based modem (new unit for $4 if you know what to look for )

Let's cut to the chase, shall we. We're talking the same connection and similar weather conditions (May and September)

Original Broadcom-based modem : 12.99mbps (with SNR tweak 14.09mbps)

Temporary replacement TrendChip modem: 10.30mbps (SNR tweak impossible to implement)

New Broadcom-based modem: 13.01mbps (with SNR tweak 14.02mbps)

Both original Broadcom modem and a replacement TrendChip one were made by the same company (Siemens) so you can't blame it on the second unit being some sort of cheap crap. It's all due to the hardware used and its possibilities and shortcomings.

To sum it up- going from a TrendChip-based modem (10.3mbps) to a Broadcom-based modem (13mbps) resulted in 30% increase in download speed and using SNR tweak bumped it up to 40% increase. This was all done on the same day and in the same conditions (I tested the temporary one and a new one on the same day).

I would advise you to spend an additional hour on the net and/or additional $ on the modem if needed but as long as you are on an ADSL connection be sure to use Broadcom-based modems.

 

Any similar tricks for cable, just wondering?

 

No, unfortunately nothing.

 

Thank you for the tricks. I'll try them on my cousin's ADSL.

 

Thanks downloads, I'll try this on my DSL-2780 hoping that they haven't disabled the command.

 

Is that a telnet command interface?

 

It's PuTTY - a telnet and SSH client. It may depend on a device whether it will accept telnet or SSH - in my case it was SSH as you can see on the config screen-shot.

 

meanwhile, in Tunisia, they lock the ADSL sync rates and make you pay for more sync, basicly you pay for nothing, a setting done by a technician in 10 seconds..

 

Can you let us know of the exact make and model of the Broadcom-based modem you are using now, please?