Understanding SNR and Attenuation Rates

PsyCLown said:
Hi guys,

So before starting a new thread I thought maybe post here quickly.
I just want to find out how much of a role the SNR upstream plays in keeping the line stable and free from resyncing?

Also whether these stats seem about right for a 10Mbit line (1Mbit up, 10Mbit down), the exchange is less than 1KM from my house and I was told that the copper distance is about 1.1KM.

SNR Margin (Upstream) 9.8 db
SNR Margin (Downstream) 24.7 db
Line Attenuation (Upstream) 10.5 db
Line Attenuation (Downstream) 15.6 db
Click to expand...

You'll get 10Mbps just fine and it will be rock solid, don't worry about the Upstream SNR.
 
Soul Assassin said:
You'll get 10Mbps just fine and it will be rock solid, don't worry about the Upstream SNR.
Click to expand...

I have a lot of line drops at the moment. :/ Busy dealing with TelkomZA - slowly working on getting the issue resolved. I plan to get 20Mbit VDSL as well within the next month or so. I am sure I can manage that on my line even though the stats seem a tad low at the moment?

During the week it seems as if my line drops a few times at around 6PM and then it will be fine for a few hours. Then on weekends it does it randomly although line stats drop drastically around the time my line drops - any ideas? Nothing inside my house changes which may effect the line stats.


EDIT: So the Telkom technician gave me a Dlink 2750U router to test to see whether my line still drops, weird interface. The ADSL stats are now as follows:

Downstream Upstream
Line Coding(Trellis): On On
SNR Margin (dB): 114 130
Attenuation (dB): 160 96
Output Power (dBm): -72 119
Attainable Rate (Kbps): 25008 1235
Rate (Kbps): 10239 1023
D (interleaver depth): 1 1
Delay (msec): 0.19 0.24

For the SNR Margins is that 11.4 and 13.0 ?
If so WTF, suddenly significantly worse downstream SNR although the upstream has improved?
 
Last edited:
Since moving my line over to Webafrica, I've gotten the power LOL :D I can set my line sync rate myself as well as do port resets. Without calling Telkom. Its a brilliant feature they implemented. I usually run my line on 5120/512 and sometimes when the line permits it I go up to 6144/640. See stats below:

RST_statistics.jpg


ADSL Link Downstream Upstream
Connection Speed 5120 kbps 512 kbps
Line Attenuation 49.0 db 31.5 db
Noise Margin 11.1 db 12.0 db


Its okay and running stable. Any what you guys think
 
Question - trying to understand my distance to exchange. I have a 4Mbps ADSL link - AH managed. Netgear DGND4000 router. See my capture below - thus, if i'm right, my attenuation and SNR is fine? Can somebody confirm?

Secondly, to calculate distance from my exchange, do i divide 13.81 into the downstream attenuation of 32.5, thus, resulting in a distance from the exchange of just over 2km's?
Capture.jpg
 
Answered my own question:) Used the tool here "http://fremnet.net/article/216/adsl-theoretical-speed-calculator" - confirms my distance to exchange is about 2.3km. My exchange is Bothasig - it shows up as 10Mbps enabled, and I've requested a 10Mbps upgrade as a result. Is it possible to work out what my best achievable speed would be, depending on the detail above?
 
haggy said:
Answered my own question:) Used the tool here "http://fremnet.net/article/216/adsl-theoretical-speed-calculator" - confirms my distance to exchange is about 2.3km. My exchange is Bothasig - it shows up as 10Mbps enabled, and I've requested a 10Mbps upgrade as a result. Is it possible to work out what my best achievable speed would be, depending on the detail above?
Click to expand...

There was an article on here a few weeks back where Telkom explained a lot of stuff. They had a graph similar to this. Depending on the tech they have in your area, you can see your speed vs distance. For normal ADSL (which is what you have in your area based on the 10 Mbps max) you should get 10 Mbps at just over 2 kms or very close to it. I am 3,5 km away from exchange and my max is around 6 Mbps.

That graph also shows that if you are more than 2,5 km from the exchange there is no point going to VDSL as your speed will be the same as on ADSL.
 
Thanks furpile - it ties up with "http://www.speedguide.net/dsl_speed_calc.php".
Capture 4.jpg
Next question from my side relates to my exchange itself - how do i determine if it's ADSL2. See pic attached relating to my exchange - it states that the exchange is 10Mbps enabled. Does this equate to ADSL2, as opposed to normal ADSL?
Capture 3.PNG
 
Is that from broadbandstats? I don't know how up to date their site is, as it shows my area as 4mbps while it is 10mbps enabled for a while now.

As to the ADSL 2+, I'm not sure. Definitely for 20 Mbps its ADSL 2+ or VDSL. I think you can check in your router what connection type it is using. If its on 2+ then you know.
 
My stats are looking good.

I just need to get everything sorted though. Finding a VDSL router seems to be difficult, as nobody has stock. I hope that I can get switched to ADSL2+ in the mean time to get full speeds

SNR Margin (dB): 13.3
Attenuation (dB): 17.5
Output Power (dBm): 12.9
Attainable Rate (Kbps): 25088
Rate (Kbps): 10239
 
topperharley said:
Good morning

I am looking at my stats for my 2Mb ADSL line :

Any ideas why my SNR is so high (SNR Margin (dB): 332 130 )?
Click to expand...

Is that a D-Link modem? They show the stats in 0,1 dB increments, so your SNR is 33,1 dB and your attenuetion 16,5 dB. Which is quite good, and like the router shows you should be able to get a 10 Mbps line easily.
 
Thanks furpile

Yes, I have the D-link DSL-2750U modem.
My exchange only supports max of 4Mb at the moment, so will have to wait a while till 10Mb is available.
 
I recently found this tool, more meant for geeks I'd say, that shows you a whole lot more than just your SNR and attenuation.
It shows it for each and every ADSL "tone", so you can spot things like interference etc. It recently helped me understand why my DSL line was not behaving, so I thought I'd share it with you all, maybe it can help with analyzing unstable ADSL syncs.

Its called DMT (DSL Modem Tool) and supports quite a few xDSL modems:

The developer's web site: http://dmt.mhilfe.de/ (its in german)
The latest version download http://www.2cent.de/dmt/v9/dmt.zip (you'll find this link at the bottom of http://dmt.mhilfe.de/)


I've successfully used this tool on:
- D-LINK 2750U
- Zyxel VDSL router ( dont recall the model number)
- Netgear DGN834

The only requirement is that you enable LAN telnet access to your router (make sure you DON'T enable WAN telnet access to the router)

Here's an example screenshot of a pretty bad DSL line if you ask me :D
dmt8.png
 
That tool definitely looks the part. Will give it a try. Thanks

Mr.Jax said:
I recently found this tool, more meant for geeks I'd say, that shows you a whole lot more than just your SNR and attenuation.
It shows it for each and every ADSL "tone", so you can spot things like interference etc. It recently helped me understand why my DSL line was not behaving, so I thought I'd share it with you all, maybe it can help with analyzing unstable ADSL syncs.

Its called DMT (DSL Modem Tool) and supports quite a few xDSL modems:

The developer's web site: http://dmt.mhilfe.de/ (its in german)
The latest version download http://www.2cent.de/dmt/v9/dmt.zip (you'll find this link at the bottom of http://dmt.mhilfe.de/)


I've successfully used this tool on:
- D-LINK 2750U
- Zyxel VDSL router ( dont recall the model number)
- Netgear DGN834

The only requirement is that you enable LAN telnet access to your router (make sure you DON'T enable WAN telnet access to the router)

Here's an example screenshot of a pretty bad DSL line if you ask me :D
dmt8.png
Click to expand...
 
My Line sync's at 4096 and 511 on adsl2+
ADSL Link Downstream Upstream
Connection Speed 4096 kbps 511 kbps
Line Attenuation 50.0 db 30.1 db

The noise margins varies from 16db to 0db and just disconnects.
Can anyone help me in what might be wrong.
It worked perfectly with a stable Noise Margin of like 14db and no disconnects not sure what is up at the moment.
 
Hi.

Is somebody able to translate these numbers from a dlink modem for me?

SNR Margin (dB) 131
Attenuation (dB) 180
Power (dBM) -178
Att Rate (Kbps) 24208
Rate 4096

The line is dropping quite often, and I was wondering if the stats indicate noise, but I'm not sure how to read these figures.
 
mister said:
Hi.

Is somebody able to translate these numbers from a dlink modem for me?

SNR Margin (dB) 131
Attenuation (dB) 180
Power (dBM) -178
Att Rate (Kbps) 24208
Rate 4096

The line is dropping quite often, and I was wondering if the stats indicate noise, but I'm not sure how to read these figures.
Click to expand...

Check about 5 posts back. The D-link shows the values in 0,1 dB increments. So your SNR is 13.1 and Att 18.0. Both values are quite good and as the modem indicates you should be able to get 20 Mbps if your exchange is capable.

You will have to monitor the stats and the modem to check exactly what happens, is it the wifi that drops, does the modem lose connection and resync etc... Also monitor the SNR to see if that value dips, it should only be a problem below 6 dB. Otherwise you could have interference from electrical devices close to your line.
 
mister said:
Hi.

Is somebody able to translate these numbers from a dlink modem for me?

SNR Margin (dB) 131
Attenuation (dB) 180
Power (dBM) -178
Att Rate (Kbps) 24208
Rate 4096

The line is dropping quite often, and I was wondering if the stats indicate noise, but I'm not sure how to read these figures.
Click to expand...

That is SHCOKING! :O

An attenuation that low and a SNR soo low as well. Is it by any chance the Telkom D-Link 2750U?

When I was using that router on 10Mbit my attenuation was 15dB and my SNR was around 13dB as well, when I changed to an older Billion 7300W my SNR increased to 24dB which is a lot more reasonable for 10Mbit with such an attenuation.

You are only syncing at 4Mbit as well. So try a different router and see if your SNR improved (higher SNR is better, lower attenuation is better). Otherwise there might be an issue with your line.
 
Hi all

I just applied for a 10mbps line from Telkom; Could anyone possibly advise whether I will be able to get a stable connection based on my current line stats?


ADSL Link (Downstream/ Upstream)
Connection Speed 4096 kbps / 512 kbps
Line Attenuation 30.5 db / 19.0 db
Noise Margin 14.8 db / 12.0 db
 
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