Line stats - good enough for 4mbit?

[Flanders]

I posted this in the 'understanding SNR and attenuation' thread ( http://mybroadband.co.za/vb/showthread.php/186156-Understanding-SNR-and-Attenuation-Rates/page5 ) but ironically I think the fact that it's stickied is causing it to be overlooked.

My line used to perform brilliantly at 4mbps but over the past few years performance dropped off to the point where I eventually had to settle for 2mbps. Recently, telkom sorted out the line to some degree and these are my current stats:

Upstream: 512 kbps
Downstream: 2048 kbps
SNR Margin (Upstream): 12.0 db
SNR Margin (Downstream): 21.5 db
Line Attenuation (Upstream): 21.5 db
Line Attenuation (Downstream): 40.5 db

I know they're busy with plans to improve things (there is currently a lot of foliage entangled on the line down the road and they need residents' permission to cut it) but I would like to phone the call center and get them to bump it back to 4mbit. Would this be doable or am I looking for trouble with my current line stats?

 

[Pada]

Your stats are good enough for 4Mbps without any issues. As soon as the line attenuation goes beyond 45dB and you have a poor ADSL modem, then you will start having issues @ 4Mbps.

Typically the SNR margin would drop about 3dB for each 1Mbps increase in the downstream speed. At 4Mbps the upload speed would remain at 512kbps, so your upstream SNR would remain the same.
I usually advise people to keep their SNR margins at 12dB or above, and yours would be about 15dB for the downstream once you've changed the profile to 4Mbps.

 

[Flanders]

Thanks, pada. I've got them to push it back to 4mbps. Line stats now show:

Upstream: 512 kbps
Downstream: 4096 kbps
SNR Margin (Upstream): 12.0 db
SNR Margin (Downstream): 22 db
Line Attenuation (Upstream): 21.5 db
Line Attenuation (Downstream): 40.5 db

One other thing; when my line was acting up, someone recommended I use ADSL G.DMT and I still have it set to this. Is this okay?

 

[Pada]

I find it very strange that you upgraded your line speed from 2Mbps to 4Mbps and that your SNR margin actually improved with 0.5dB!

Don't change anything to what it's currently using, because your SNR margins are pretty good at this moment.

 

[Flanders]

I find it very strange that you upgraded your line speed from 2Mbps to 4Mbps and that your SNR margin actually improved with 0.5dB!

Don't change anything to what it's currently using, because your SNR margins are pretty good at this moment.

Okay, thanks for the info. Yea, about the SNR, I don't really know. I've been monitoring it for the past few days and the only thing that varies is this...and by max of 0.5 to boot. The line seems rock-solid again after so long and it's really nice to be back in 4mbit land. I know my exchange is 10meg compliant/ready/enabled but I feel that I don't want to get greedy now and push it any further. Good balance between stability and speed right now so I'm happy.

 

[Pada]

Could you perhaps find out what modulation your ADSL router is currently using? It would either be ADSL2+ or G.Dmt.

With your current downstream SNR margin, you should be able to push your downstream speed to 6Mbps, but you might run into a lowish upstream SNR margin when they also increase your upstream speed to like 640kbps, but this might not even happen due to your modem increasing the output power.

 

[Flanders]

Could you perhaps find out what modulation your ADSL router is currently using? It would either be ADSL2+ or G.Dmt.

G.Dmt at the moment but as I mentioned this was recommended when my line was screwed so I've just kept running it with this modulation ever since.

 

[fragtion]

I find it very strange that you upgraded your line speed from 2Mbps to 4Mbps and that your SNR margin actually improved with 0.5dB!

I don't Remember, depending on the line in question, SNR can fluctuate a lot... mine fluctuates within about 8db range on a typical day. On average he should be a few db's lower now though

 

[czc]

My stats are poorish/ very iffy from the link in Pada's sig.


Modulation: G.992.3 annex A

Bandwidth (Up/Down) [kbps/kbps]: 123 / 383

Line Attenuation (Up/Down) [dB]: 31,0 / 51,5

SN Margin (Up/Down) [dB]: 26,0 / 9,5