Re: 3G Signal CSQ

[Dan Williams <dcbw redhat com>]

On Sun, 2012-03-18 at 16:51 +0100, Aleksander Morgado wrote:
> Hoola,
> 
> > I see that NM request signal quality from 3G modem. I need dbm or
> > similar. Any command line option while modem it is locked by NM.
> > I need obtain dbm or result of at+csq
> >
> 
> You can query the signal quality retrieved by NM/MM directly using the 
> DBus interface and the 'dbus-send' command line utility (assuming your 
> modem is at index 0 here):
> 
> dbus-send --system --dest=org.freedesktop.ModemManager --print-reply 
> /org/freedesktop/ModemManager/Modems/0 
> org.freedesktop.ModemManager.Modem.Gsm.Network.GetSignalQuality
> 
> That won't give you neither the raw dBm value nor the rssi, though. It 
> will give you a computed percentage value [0,100] representing the 
> signal quality.

Right; most modems don't support reporting dBm or RSSI, including almost
all that only support AT commands.  Proprietary interfaces like CnS,
QMI, WMC, or DIAG etc may support reporting dBm though.  However,
remember that dBm is really only useful for 2G and 4G technologies.  For
3G, whether EVDO or UMTS, the unit you're really looking for is EC/IO
(energy-per-chip over interference) which is how signal quality is
calculated for [W]CDMA-based air interfaces.

Dan