Noise Margin and speed

[barrymung]

Hi All,

My Broadband 'training period' has presumably now finished and I'm getting the following statistics:

Broadband Link	Downstream	Upstream
Connection Speed	6973 kbps	798 kbps
Line Attenuation	48.5 dB	30.3 dB
Noise Margin	6.1 dB	14.14 dB

Do these figures seem sensible?

Reason for asking is that I thought Sky ramped the speed up until the downstream noise margin dropped to around 4dB. Mine is above 6dB.

Is this line therefore capable of a better speed? If so, how do I go about getting it?

[gymno]

Almost 7mb downstream with an attenuation of 48.5 is excellent.

48.5db = a line length af approximately 3.5km.
DLM will only use a noise margin below 6db if the line is extremely good & errors don't build up causing instability.
In practice, this usually only applies to lines around 1km long or less.

I have 22.5db attenuation (1.4km) & DLM used a noise margin of 6db.

[barrymung]

Well, I'm not complaining, just curious if i could eke some more out on the connection.

Out of interest I rebooted the router and it's gone up a tad to 7007mbps downstream.

3.5km sounds about right as the exchange is about 1.5 miles by road.

[gymno]

The speed change after a reboot is perfectly normal.

6db is the 'target' noise margin.
I don't know the exact figures for the profile you're on, but let's say it's 7014 / 814.
Normally if you reboot while the nm is 0.2 or more above target, it'll 'use up' that extra margin, you'll get the full speed according to the profile & nm will return to target.

Likewise, if you reboot when the nm is 0.2 or more below target, the opposite will happen & you'll lose a few kbps.

[Isitme]

Your line will be set to 7008/800kbps. With ADSL2+ you will always loose a few Kb, what you actually get will depend on the noise on your line when it is rebooted. As Gymno says, you are doing very well for your attenuation.