Some 10Mbs question

[Kooku]

Hi All

I am looking for someone who knows the Line Attenuation and SNR Margin requirements for a 10mbs line.

I had a 4mbs line which I had upgraded to 6mbs when I called Telkom a few months ago.
They said that the fastest I could get at the time was 8mbs as the exchange could only handle up to that speed.
I checked recently and the exchange now says 10mbs capable but the Telkom techie I spoke to says that 6mbs is the fastest it can go.

My DSL Info is at 6mbs

Line Attenutation (db) 36.5 Local 15.0 Remote
SNR Margin (db) 13.5 Local 8.0 Remote
TX Power (db) 12.3 Local 19.1 Remote

Should this be sufficient to get 10mbs on an ADSL2+ line? According to the post on attenutation rates it should http://mybroadband.co.za/vb/showthread.php/186156-Understanding-SNR-and-Attenuation-Rates

Does that mean that I am not in fact on an ADSL2+ line, Line attenuation and the max speed would seem to indicate that I am still on a ADSL line and not ADSL2+
Do the 10Mbs lines use ADSL2+ to get the 10mbs lines?
How can I check if I am on an ADSL2+ connection?


Thanks

JohnB

 

[Chevron]

An SNR of 8 is a bit low. If you up your speed you'll probably get disconnects.

How can I check if I am on an ADSL2+ connection?

You set your router to ADSL 2+ and see if it connects.

 

[jackshiels]

I think mine is a good "case study". I live almost 3km away from my DSLAM, yet I can still get 10Mb down (albeit a little under the 1024Kb upload speed). I don't really have any sync problems worth noting, either.

Upstream 888000
Downstream 10010100
SNR Margin(Upstream) 7.0 dB
SNR Margin(Downstream) 10.20 dB
Line Attenuation(Upstream) 16.5 dB
Line Attenuation(Downstream) 41.0 dB

I reckon you can reach 10Mb if your profile is changed. Much like you my upload SNR is low. You can survive on 6db if your router is good (sometimes even as low as 1-3db with custom firmwares). Regardless your upload speed being less than the sync profile will not require you to move to a lower download speed - it will sync as well as it can.

 

[Yotch]

The current ADSL2+ Annex A configuration only allows a maximum upload speed of ~1Mbps at any download speed. If you are currently achieving a close to 1Mbps upload speed at 6 or 10Mbps the upload statistics should not change much when the download speed is increased. The downstream attenuation and noise margin are the figures which will determine the maximum downstream speed.

ADSL2+ maximum speed calculators ...
http://www.coolwebhome.co.uk/calc/calculator.php
http://www.farina1.com/adsl/
http://en.wikipedia.org/wiki/ITU_G.992.5_Annex_M
Predicted top speed for my line
http://www.coolwebhome.co.uk/calc/calculator.php?param=8/ahLQp6An+wNWi0OalFYzT8YN1uqaPfhNWk1xNa77o=

 

[Rickster]

[-]And I thought my noise margin of 16.4dB down stream was good.[/-]

Oh wait...it is according to:

Noise Margin (AKA Signal to Noise Margin or Signal to Noise Ratio)
Relative strength of the DSL signal to Noise ratio. The higher the number the better for this measurement. In some instances interleaving can help raise the noise margin to an acceptable level.

6dB or below is bad and will experience no synch or intermittent synch problems
7dB-10dB is fair but does not leave much room for variances in conditions
11dB-20dB is good with little or no synch problems* (but see note below)
20dB-28dB is excellent
29dB or above is outstanding

* Note that there may be short term bursts of noise that may drop the margin, but due to the sampling time of the management utility in your modem, will not show up in the figures.

Line Attenuation
Measure of how much the signal has degraded between the DSLAM and the modem. This is largely a function of the distance from the exchange. The lower the dB the better for this measurement.

20dB and below is outstanding
20dB-30dB is excellent
30dB-40dB is very good
40dB-50dB is good
50dB-60dB is poor and may experience connectivity issues
60dB or above is bad and will experience connectivity issues

DSL Rate ***/tx/rx/Rate
The actual service data rate that your ISP has provisioned.

Attainable Line Rate
This is the maximum rate at which your modem can connect to the DSLAM if there was no service provisioning limiting the bandwidth. The higher the number the better.

Occupancy
Occupancy is the percentage of line capacity used. Each DSL line is capable of a certain maximum speed or "capacity" dependant on line distance and other varying factors. The occupancy is an expression of your current sync rate setting over your maximum capacity. There are occupancy rates for both upload and download. The lower the figure, the better. Because of error correction and other factors in the DSL protocols, a margin is required so that a connection can be maintained under varying line conditions. If the occupancy approaches 100%, any interference can cause the ADSL sync to be lost. A useful measurement to monitor when sync problems occur. [AFAIK the billion SNMP utility does not give a direct measurement of occupancy

 

[Yotch]

A 20dB downstream noise margin at 10Mbps should allow a decent ADSL2+ speed of ~16Mbps but 20dB at 1Mbps and you may struggle to reach 4Mbps.

 

[Kooku]

Thanks for the advice folks, I set the modem to ADSL2+ but it does not connect so I assume that the connection is only ADSL.

I will se if I can get hold of the guys at Crowthorne exchange and see what they say. According to the ADSL checker, the exchange supports 10MBs but obviously not on my port.

JohnB

 

[Chevron]

Thanks for the advice folks, I set the modem to ADSL2+ but it does not connect so I assume that the connection is only ADSL.

I will se if I can get hold of the guys at Crowthorne exchange and see what they say. According to the ADSL checker, the exchange supports 10MBs but obviously not on my port.

JohnB

That makes sense. While adsl can technically support up to 8Mb/s, telkom only use it up to 6Mb/s.