Signal quality

[José]

ModemManager reports look like this:

Status | lock: 'none'
| unlock retries: 'sim-pin (3), sim-pin2 (3), sim-puk (10), sim-puk2 (10)'
| state: 'connected'
| power state: 'on'
| access tech: 'hsdpa'
| signal quality: '38' (recent)

I have some questinos about the signal quality quantity:

* Which units does the 'signal quality' use?
* Is it the same for any technology/modem?
* How does it relate to RSSI and dbm?

Thanks.