How do routers and modems measure attenuation etc?

I'm surprised that my relatively cheap modem can measure SNRs and attenuations etc in addition to doing its main job! SNR is not that easy to measure - do modems measure relative rather than absolute parameters? Do exchanges output standard signal powers?

Yours intrigued

Nick

the exchange tells the modem what power it is outputting, the modem measures the received power and from that calculates the attenuation.

Measuring SNR in multiple frequency bands is a key part of the way G.dmt systems work so it is its "main job" to know that.

Phil

MaxDSL - goes as fast as it can and doesn't read the line checker first.

MaxDSL diagnostics
Are your kids pirates ? Limewire, Bearshare, Kazaa, BitTorrent, eMule are all tools of the trade.

I’m currently using a Thompson Speeouch 585. Stats are as quoted in my sig. If I use My BT Voyager 2500 or 205, the line attenuation is measured at 18.5 dB. Downstream SNR is also lower. I’ll probably buy a Netgear router soon and wonder what my stats will look like.

______________________________________
IDNet

Sync: 8128 / 832 kbps
IP Profile 7150 kbps
SNR Margin: 17.0-12.5 dB
Line Attenuation: 20.0 dB
SpeedTouch 585

I am approximately 930 metres from the exchange (straight line distance)

I’ll probably buy a Netgear router soon and wonder what my stats will look like.

Not the same???

I've used the Netgear DG834GT,the DG834N and also the DG834G v3 and the reported attenuation stats have all been different.
The DG834N reports 56-57dB down (Broadcom chipped)

whereas the DG834 v3 reported 53-54dB down (AR7 chipped)

As far as I can remember the DSLAM in my exchange is Texas Ins. chipped (according to the ST585 v6 I used last year) so whether the v3 would give a more accurate range of stats, I don't know.

Alastair

omadasafisho