For 3G devices in Class A, AT+WWSM can be used to get or set the allowed mode:
* +WWSM: 0 (2G only)
* +WWSM: 1 (3G only)
* +WWSM: 2,0 (Any)
* +WWSM: 2,1 (2G preferred)
* +WWSM: 2,2 (3G preferred)
For 2G devices, there is no such command, so we will default to Any and allow
2G-only and 2G-preferred setups.
These modems can be configured to use different mobile classes. For each kind of
modem, the best mobile class is the highest one in the following order:
- Class A (3G only mode)
- Class B (PS or CS, GPRS/EDGE or GSM)
- Class CG (PS only, GPRS/EDGE)
- Class CC (CS only, GSM)
