3GPP standards
AT-commands are specified in 3GPP TS 27.005 and 3GPP TS 27.007.



list of AT-commands

Selecting an APN
+CGDCONT=1,”IP”,”apn name”
e.g. for Vodafone UK – AT+CGDCONT=1,”IP”,”internet”


Querying signal strength
+CSQ
Returns two comma separated numbers. The first number is the signal strength (RSSI), the second number is unused. Here’s how to interpret RSSI:
0 <= -113dBm
1 -111dBm
2 – 30 -109dBm to -53dBm
31 >= -51dBm
99 Unknown


Setting operating mode
+CFUN=x
0 Low power mode
1 Online
4 Offline
6 Reset device
7 Turn off radio


Get manufacturer information
+CGMI


Get software version
+CGMR


Get SIM IMSI number
+CIMI


Get device IMEI
+CGSN


Get hardware version
^HWVER


Change PIN
+CPWD=SC,old pin, new pin


Enable PIN
+CLCK=SC,mode,pin
Mode: 0=unlock, 1=lock, 2=query state
On some modems it may be necessary to quote both SC and PIN.


Query system information
^SYSINFO
Returns: status, domain, roaming status, mode, SIM state
Status
0 No service.
1 Restricted service
2 Valid service
3 Restricted regional service.
4 Power-saving and deep sleep state
Domain
0 No service.
1 Only CS service
2 Only PS service
3 PS+CS service
4 CS and PS not registered, searching
Roaming
0 Non roaming state
1 Roaming state
Mode
0 No service.
1 AMPS mode (not in use currently)
2 CDMA mode (not in use currently)
3 GSM/GPRS mode
4 HDR mode
5 WCDMA mode
6 GPS mode
SIM state
0 Invalid USIM card state or pin code locked
1 Valid USIM card state
2 USIM is invalid in case of CS
3 USIM is invalid in case of PS
4 USIM is invalid in case of either CS or PS
255 USIM card is not existent,


Network selection
+COPS=? Return a list of networks
+COPS=mode, format, operator
Mode
0 Automatic
1 Manual
4 If manual fails, try automatic
Format
1 Long alpha
2 Short alpha
3 Numeric
Operator
Either the long alpha name, the short operator alpha code or the numeric code
Status
0 unknown
1 available
2 current
3 forbidden


System Config
^SYSCFG=mode, order, band, roaming, domain
Mode
2 Automatic search
13 2G ONLY
14 3G ONLY
16 No change
Order
0 Automatic search
1 2G first, then 3G
2 3G first, then 2G
3 No change
Band
80 GSM DCS systems
100 Extended GSM 900
200 Primary GSM 900
200000 GSM PCS
400000 WCDMA IMT 2000
3FFFFFFF Any band
40000000 No change of band
Roaming
0 Not supported
1 Roaming is supported
2 No change
Domain
0 CS_ONLY
1 PS_ONLY
2 CS_PS
3 ANY
4 No change


Sending USSD Commands
+CUSD=1,"USSD-Command"
e.g. AT+CUSD=1,"*100#"
for some devices you will need to attach ",15" to your AT-command, as there won't come any return otherwise:
e.g. AT+CUSD=1,"*100#",15