SNR

[gmorgan]

Has anyone managed to get SNR parameters to work on fibre? I've read on another forum using another router that you are able to adjust snr without dlm counter adjusting..... Was hoping it would work with the Billion.

[billion_fan]

Has anyone managed to get SNR parameters to work on fibre? I've read on another forum using another router that you are able to adjust snr without dlm counter adjusting..... Was hoping it would work with the Billion.

I don't think you can tweak the SNR when using VDSL

[simon194]

The manual says the SNR tweaking is for ADSL only. Anyway tweaking the SNR on fibre can have a detrimental affect on your speed if DLM decides there is an issue with the line.

From SIN498 "Note : It is the DLM system that sets the line profile, and this should not be interfered with by CPs/users setting rates, SNR margins etc. at the modem."

I'm sure I read somewhere that one of the criteria for a VDSL modem/router to be certified for use on the Openreach network it has to have a SNR that isn't user adjustable.

[spiralarms]

I've just received my 8800NL at the weekend, and I'm using it with the ADSL, and so I'm hoping to make use of the SNR tweaking. I've a couple of questions though (surprise surprise). The reason I got the 8800NL was to see if I could improve my connection over my old 3Com OfficeConnect router. We're in a rural area, fairly far from the exchange, as can be seen by the attenuation. My previous router reported 60dB for the downstream attenuation.

My current stats from the xDSL page show:

Code: Select all

              Downstream	Upstream
SNR Margin (dB)    6.4	22.0
Attenuation (dB)   52.0	31.5
Attainable Rate (Kbps)  4796	1144
Rate (Kbps)        4512	448

I've currently got the SNR tweak set to "5". So my first question is, is the reported "6.4" for the downstream SNR reflect the actual figure as measured by 8800NL, but the tweak will be reporting "5" back to the exchange?

Second question, not actually SNR, but about the Rates. The manual says:

Attainable Rate (Kbps): The sync rate you would obtain.
Rate (Kbps): Show the downstream and upstream rate in Kbps.

Is that saying with some tweaking I could make it to 4796 compared to the current actual rate of 4512? Or is that some sign of rate limiting being applied at the exchange end?

I know there's a difference between sync rate and what I'm likely to actually achieve as a download rate on a PC connected to the router (currently various speed tests say I'm getting about 3.2Mbps).

Thanks,

Neil

[billion_fan]

I've just received my 8800NL at the weekend, and I'm using it with the ADSL, and so I'm hoping to make use of the SNR tweaking. I've a couple of questions though (surprise surprise). The reason I got the 8800NL was to see if I could improve my connection over my old 3Com OfficeConnect router. We're in a rural area, fairly far from the exchange, as can be seen by the attenuation. My previous router reported 60dB for the downstream attenuation.

My current stats from the xDSL page show:

Code: Select all

              Downstream	Upstream
SNR Margin (dB)    6.4	22.0
Attenuation (dB)   52.0	31.5
Attainable Rate (Kbps)  4796	1144
Rate (Kbps)        4512	448

I've currently got the SNR tweak set to "5". So my first question is, is the reported "6.4" for the downstream SNR reflect the actual figure as measured by 8800NL, but the tweak will be reporting "5" back to the exchange?

Second question, not actually SNR, but about the Rates. The manual says:

Attainable Rate (Kbps): The sync rate you would obtain.
Rate (Kbps): Show the downstream and upstream rate in Kbps.

Is that saying with some tweaking I could make it to 4796 compared to the current actual rate of 4512? Or is that some sign of rate limiting being applied at the exchange end?

I know there's a difference between sync rate and what I'm likely to actually achieve as a download rate on a PC connected to the router (currently various speed tests say I'm getting about 3.2Mbps).

Thanks,

Neil

1. Normally a SNR setting of 5 would mean a -1db off your untweaked SNR value (if set to -1 then you should get 7.4db)
2. From my understanding the 'Attainable Rate ' is the max your line would go (from the router calculating the line states), with the current SNR reading. The 'Rate' is the speed the modem syncs with the exchange.

[spiralarms]

My current stats from the xDSL page show:

Code: Select all

              Downstream	Upstream
SNR Margin (dB)    6.4	22.0

I've currently got the SNR tweak set to "5". So my first question is, is the reported "6.4" for the downstream SNR reflect the actual figure as measured by 8800NL, but the tweak will be reporting "5" back to the exchange?

1. Normally a SNR setting of 5 would mean a -1db off your untweaked SNR value (if set to -1 then you should get 7.4db)
2. From my understanding the 'Attainable Rate ' is the max your line would go (from the router calculating the line states), with the current SNR reading. The 'Rate' is the speed the modem syncs with the exchange.

Thanks, that's useful about rate, but I'm still in not clear about the SNR figure reported on stats page. Are you saying that's the actual SNR value measured by the router, regardless of what tweak setting I may have?

I guess what I really want to know, is if I change the SNR tweak value (in any direction) would I expect to see the SNR value on the stats page change (because of the tweak value, not due to actual changes in the conditions on the line)?

Thanks.

Neil

[billion_fan]

My current stats from the xDSL page show:

Code: Select all

              Downstream	Upstream
SNR Margin (dB)    6.4	22.0

I've currently got the SNR tweak set to "5". So my first question is, is the reported "6.4" for the downstream SNR reflect the actual figure as measured by 8800NL, but the tweak will be reporting "5" back to the exchange?

1. Normally a SNR setting of 5 would mean a -1db off your untweaked SNR value (if set to -1 then you should get 7.4db)
2. From my understanding the 'Attainable Rate ' is the max your line would go (from the router calculating the line states), with the current SNR reading. The 'Rate' is the speed the modem syncs with the exchange.

Thanks, that's useful about rate, but I'm still in not clear about the SNR figure reported on stats page. Are you saying that's the actual SNR value measured by the router, regardless of what tweak setting I may have?

I guess what I really want to know, is if I change the SNR tweak value (in any direction) would I expect to see the SNR value on the stats page change (because of the tweak value, not due to actual changes in the conditions on the line)?

Thanks.

Neil

With the tweak in place, this is actual SNR the router is picking up at moment. Without a tweak or set back to -1, this is will be the SNR value set by the ISP

See the attached table for SNR values, eg if you leave the router on -1 meaning default and you get a SNR of 9db, then if you enter 1 you should be around 4db. (9db - 5db = 4db) the attached table runs off your default SNR value