Understanding SNR and Attenuation Rates

@markface:
I doubt it is the router. Try changing the ADSL mode/modulation from ADSL2+ to G.DMT, or other way round.

You are pretty far away (according to the attenuation) from the DSLAM/Exchange, and this would be 1 reason why your ADSL modem would struggle to synchronize at 1Mbps down + 512kbps up.
What speed connection & ADSL modem did you previously have when it was still stable?

Lastly, could you also post your downstream & upstream speeds reported by the ADSL modem?
 
Pada said:
@markface:
I doubt it is the router. Try changing the ADSL mode/modulation from ADSL2+ to G.DMT, or other way round.

You are pretty far away (according to the attenuation) from the DSLAM/Exchange, and this would be 1 reason why your ADSL modem would struggle to synchronize at 1Mbps down + 512kbps up.
What speed connection & ADSL modem did you previously have when it was still stable?

Lastly, could you also post your downstream & upstream speeds reported by the ADSL modem?
Click to expand...
I've had quite a few months of near perfect line speeds, and zero drops at 1mbps.

Modem reports:
Line Rate - Upstream (Kbps): 448
Line Rate - Downstream (Kbps): 1024

So looks like you're right. Something seriously wrong with the upstream SNR. I've checked my stats before this though, and they've always been in the good/excellent range.

I've reported a fault with Telkom - we'll see how this pans out.
 
@markface:
Remove the ADSL filter and other telephonic devices, such that only the ADSL modem is connected to the Telkom line.
Once you've done that, recheck your statistics.

Also check the ADSL mode that you're using: either ADSL2+ / G.DMT
G.DMT usually works best with high attenuation values.
 
ajules said:
I bought it from Uniterm Direct.Will give them a call and see if I can take it in for testing.Thanks for the help.
Click to expand...
Well according to Uniterm Direct CT office after doing testing on my router they reckon it is not faulty :confused::confused:Strange thing is that I have been running an old Netgear DG834G v5 on my line for the past 3 days and no disconnections and very stable snr margin.
 
Hi all,

Have a 4Mbs line that has been solid for almost a year but for the past week its been super slow and unstable speed wise.

I haven't noticed any line syncing problems though.

Used to get a consistent +- 3.3Mb/s on Local & slightly less on Intl speedtest.net tests, but now I'm getting:

Local: avg. about 1.5Mb/s
Intl: avg. 0.5Mb/s

Pings are also a bit higher than normal but not hugely.

Have tried 3 different ISPs and no change.

I checked my DSL stats and I think maybe something has stuffed up my line, my SNR on Downstream is bad, right?
Downstream Upstream
Line Coding(Trellis): On On
SNR Margin (0.1 dB): 77 133
Attenuation (0.1 dB): 460 241
Output Power (0.1 dBm): 0 48
Attainable Rate (Kbps): 6572 972

Path 0 Path 1
Downstream Upstream
Rate (Kbps): 4096 507
Click to expand...

I plugged my modem (TP-Link TDW8960N) directly into the line without a filter and my SNR upstream improves to about 9dB. I also changed between ADSL2+ and GDMt but that didn't help improve the SNR, it was slightly worse on GDmt.

What are my options - can I get Telkom to investigate and improve my line or will they only drop me to a lower speed profile?

I did see a Telkom van here in the complex about a week ago - maybe they stuffed the line up :/

Thanks!
 
Wonder how the modem works out the attainable rate? Using your current SNR Margin and Attenuation or does it sense it from the ADSL port you are on?

ADSL.jpg
 
It calculates it from your current SNR values. You sync at amazing rates, so I guess you are really really close to the DSLAM.
 
Tinuva said:
It calculates it from your current SNR values. You sync at amazing rates, so I guess you are really really close to the DSLAM.
Click to expand...

Thanks for the info. Yes the DSLAM sits in the complex about 200 meters away. So I should not take my results as an indication that the DSLAM was upgarded to 20Mb/s?
 
AllBrain:
No not at all. The 'Attainable Rate' is simply an estimate of your ADSL modem for the maximum speed that you might synchronize at, however your DSLAM might not even support 10Mbps.

Currently your ADSL modem is only synchronizing at 1Mbps down/0.5Mbps up, so there is no way for us on telling you whether your DSLAM supports anything faster than 1Mbps. Since your ADSL modem is using ADSL2+ modulation, the odds are pretty high that your DSLAM/Exchange supports 10Mbps.
 
Good to know Pada. At the very least I know the DSLAM can do 4Mb/s second as I downgraded from that to 1Mb/s when Telkom reintroduced it. :)
 
Im having problems connecting to my Telkom ADSL line most of the time, my modem Status is as follow , what can be the problem

Connection Status Connected
Us Rate (Kbps) 128
Ds Rate (Kbps) 384
US Margin 9
DS Margin 8
Trained Modulation ADSL_G.dmt
LOS Errors 0
DS Line Attenuation 42
US Line Attenuation 31
Peak Cell Rate 301 cells per sec
CRC Rx Fast 4
CRC Tx Fast 0
CRC Rx Interleaved 0
CRC Tx Interleaved 0
Path Mode Fast Path
 
Pada said:
@markface:
Remove the ADSL filter and other telephonic devices, such that only the ADSL modem is connected to the Telkom line.
Once you've done that, recheck your statistics.

Also check the ADSL mode that you're using: either ADSL2+ / G.DMT
G.DMT usually works best with high attenuation values.
Click to expand...
Turns out they were installing fibre around my area which was stuffing up my signal. I am back to normal it seems:
Downstream Upstream
Line Coding(Trellis): On On
SNR Margin (0.1 dB): 292 140
Attenuation (0.1 dB): 460 195
Output Power (0.1 dBm): 73 81
Attainable Rate (Kbps): 9920 980

Syncing at my full line speed of 1mbps down, 512k up.
 
Can anybody tell me if this is good or bad.

ADSL Link Downstream Upstream
Connection Speed 384 kbps 128 kbps
Line Attenuation 44.0 db 22.5 db
Noise Margin 18.5 db 18 db
 
lilggg:
Your chances of getting a stable 4Mbps ADSL connection would be very small, but still not unlikely - when looking at your line attenuation figures.

As for your 384kbps ADSL connection your SNR (signal to noise ratio) margins are looking good.
 
From what i read on page 1 noise margin is different to SNR? There is lots of crackling on the phone and the adsl is timing out and losing sync every few mins. So if the stats are good then i have no idea whats wrong.
 
lilggg:
SNR and noise margin is one and the same thing. Apparently some noise margins are like SNR margin - 6dB, where 6dB is the minimum SNR margin required to have an ADSL connection, but I haven't really seen cases like that.

Remove your ADSL completely. If there's still crackling on your telephone, make sure that it is connected properly.

If you can still hear a crackling sound on your telephone, then log that as a fault with Telkom, and keep escalating it till it is resolved.
This way it should also fix your ADSL problem.

Lastly, do you have your telephone(s) connected via a filter?
 
Yea it is connected to filter,it comes and goes though, sometimes the adsl is fine and theres no crackling for hours. I think we tried with a different filter as well from our old router and there was no difference. Will try remove the adsl and check, thanks. Already logged a fault for the 2nd time, the first time a techie came we told him telkom must have fixed it on their side because we never had problems the whole day, but it started up again that evening.
 
I have drop outs every 2-3 hrs on new line (Recently moved to Durban-Pinetown), and was wandering if it's my modem or this new line? Pada, pls help!

Modem Info:
Billion 5210S (3yrs old!)

Modulation:
G.DMT

SNR Margin:
Downstream 14.5db Upstream 12.0db

Line Attenuation:
Downstream 54.0db Upstream 27.0db

Data Rate:
Downstream 384kbps Upstream 128kbps

Speedtest results:
http://www.speedtest.net/result/1699785408.png

Pingtest results:
http://www.pingtest.net/result/54273283.png

Tracert results (to www.google.com)
Tracing route to www.l.google.com [209.85.147.105]
over a maximum of 30 hops:

1 1 ms 2 ms 2 ms 192.168.1.254
2 23 ms 23 ms 23 ms 196-210-132-1.dynamic.isadsl.co.za [196.210.132.1]
3 113 ms 109 ms 109 ms 196.38.73.85
4 82 ms 78 ms 78 ms cdsl2-rba-vl150.ip.isnet.net [196.38.73.9]
5 59 ms 67 ms 65 ms core1b-rba-te2-0-0.ip.isnet.net [196.26.0.181]
6 304 ms 301 ms 299 ms mi-za-rba-p5-gi2-0-2.ip.isnet.net [168.209.164.7]
7 291 ms 281 ms 282 ms mi-uk-dock-p3-gi3-1-1.ip.isnet.net [168.209.161.80]
8 335 ms 325 ms 332 ms core1a-dock-gi1-0-17.ip.isnet.net [168.209.164.204]
9 255 ms 262 ms 251 ms 168.209.246.3
10 266 ms 266 ms 265 ms 195.66.226.125
11 313 ms 312 ms 309 ms 209.85.255.175
12 272 ms 273 ms 271 ms 209.85.253.94
13 319 ms 343 ms 336 ms 72.14.232.134
14 309 ms 343 ms 306 ms 216.239.49.45
15 357 ms 351 ms 309 ms 216.239.46.221
16 302 ms 312 ms 311 ms bru01m01-in-f105.1e100.net [209.85.147.105]

Trace complete.

My line to the telephone jack is 10m long. Is that an issue?
 
kingd53 said:
I have drop outs every 2-3 hrs on new line (Recently moved to Durban-Pinetown), and was wandering if it's my modem or this new line? Pada, pls help!

Modem Info:
Billion 5210S (3yrs old!)

Modulation:
G.DMT

SNR Margin:
Downstream 14.5db Upstream 12.0db

Line Attenuation:
Downstream 54.0db Upstream 27.0db

Data Rate:
Downstream 384kbps Upstream 128kbps

Speedtest results:
http://www.speedtest.net/result/1699785408.png

Pingtest results:
http://www.pingtest.net/result/54273283.png

Tracert results (to www.google.com)
Tracing route to www.l.google.com [209.85.147.105]
over a maximum of 30 hops:

1 1 ms 2 ms 2 ms 192.168.1.254
2 23 ms 23 ms 23 ms 196-210-132-1.dynamic.isadsl.co.za [196.210.132.1]
3 113 ms 109 ms 109 ms 196.38.73.85
4 82 ms 78 ms 78 ms cdsl2-rba-vl150.ip.isnet.net [196.38.73.9]
5 59 ms 67 ms 65 ms core1b-rba-te2-0-0.ip.isnet.net [196.26.0.181]
6 304 ms 301 ms 299 ms mi-za-rba-p5-gi2-0-2.ip.isnet.net [168.209.164.7]
7 291 ms 281 ms 282 ms mi-uk-dock-p3-gi3-1-1.ip.isnet.net [168.209.161.80]
8 335 ms 325 ms 332 ms core1a-dock-gi1-0-17.ip.isnet.net [168.209.164.204]
9 255 ms 262 ms 251 ms 168.209.246.3
10 266 ms 266 ms 265 ms 195.66.226.125
11 313 ms 312 ms 309 ms 209.85.255.175
12 272 ms 273 ms 271 ms 209.85.253.94
13 319 ms 343 ms 336 ms 72.14.232.134
14 309 ms 343 ms 306 ms 216.239.49.45
15 357 ms 351 ms 309 ms 216.239.46.221
16 302 ms 312 ms 311 ms bru01m01-in-f105.1e100.net [209.85.147.105]

Trace complete.

My line to the telephone jack is 10m long. Is that an issue?
Click to expand...
Line Attenuation:
Downstream 54.0db

seems to be the problem that is a bit high if you have checked filters then maybe logging a fault with telkom would be the best option you have.
the 10 meter cable should not be giving problems unless its passing a lot of electronic equipment which may cos problems but quick test with a shorter cable would easily prove if this the problem
 
Telkom will just say your problem has been resolved if you log a fault,without them telling you what they did. Problem still exists.
 
You must log in or register to reply here.
Back
Top
Sign up to the MyBroadband newsletter
X