SNR too low for VDSL

[Carnajo]

Hi everyone,

I see that my exchange has recently been upgraded to VDSL (the only one in my area which had not been upgraded) but when I phoned Axxess to ask about an upgrade I was told that my SNR is too low and it would cause constant disconnects.

From what I gather there isn't anything I can do about this but I thought I'd ask on here because one never knows.

My current line is 10 mbps and it works perfectly

According to Axxess my SNR is 12dB

My router reports
Signal Margin - 11 dB
Attenuation - 31 dB

If there is anything that I can do it would be awesome.

Thanks

 

[Kayoss]

How far are you from the MSAN?

If you're on 10mb then I assume you're still syncing on ADSL2+? Look in your router at your modulation..

If so, then when they swop you over onto VDSL modulation, your SNR margins should jump up. Also, VDSL is much less sensitive to SNR and attenuation than ADSL and tends to be stable at lower SNR margins than ADSL is.

I'd say that if possible, ask them to put you on 20mb and see how your connection is. If it's unstable then go back down to 10mb.

 

[Segg]

Check this thread out

The following guide (distance vs. attenuation vs speed) gives you an guestimate what you can achieve:
<1km should be 23-24Mbit (nice speed, but doesn't it bug you that Telkom people walk through your bedroom?)
1.0km = 13.81dB = 23Mbit
1.5km = 20.7dB = 21Mbit
2.0km = 27.6dB = 18Mbit
2.5km = 34.5dB = 13Mbit
3.0km = 41.4dB = 8Mbit
3.5km = 48.3dB = 6Mbit
4.0km = 56dB = 4Mbit
4.5km = 62.1dB = 3Mbit
5.0km = 69dB = 2Mbit
>5.0km (you are pretty much poked --- sorry for you)

Looking at this graph, it would appear that Axxess is correct, but it never hurts to give it a try anyway

 

[Kayoss]

Check this thread out



Looking at this graph, it would appear that Axxess is correct, but it never hurts to give it a try anyway

View attachment 237060

Nah, that graph isn't too accurate for VDSL.

My current attenuation is 18.5 which would put me at roughly 1.5km from the MSAN, and a max sync of 25mb, according to that graph. I'm currently syncing at 41mb and my SNR is holding strong at 15. My line is stable and doesn't ever drop!

I found that when I went from ADSL2+ modulation onto VDSL, my SNR/Attenuation held strong. SNR would normally drop with the speed increase. I think it went from 18 down to 15 with a 39mb increase in sync speed (was on a 2mb line before). I really don't believe that I'm an exception to the rule either.

Like you said, it won't hurt to try, so I agree that OP should at least try out the 20mb option.

 

[Carnajo]

Thanks for the input guys.

Axxess guy seemed to think that my SNR would drop to around 6 if I move to VDSL.
I wouldn't mind giving it a try its just that I would need to go and buy a VSDL modem. Perhaps I can find one to borrow or buy a second hand one I can sell on.

 

[aquadat0r]

Hi, I also upgraded recently with my SNR dropping to 6.5dB. I'm using a Pace modem which probably is not the best. Might get better SNR with another brand, still waiting feedback on another forum.

This being said, my line is stable at 6.5dB with no disconnects for days. There are a few CRC errors, but nothing noticable in use. Probably 0.001% of all packets downstream. So far, so good.

 

[User52]

6.5dB at what speed? (actual speed, like speedtest)?