Unstructured Supplementary Service Data (USSD), sometimes referred to as "Quick Codes" or "Feature codes", is a protocol used by GSM cellular telephones to communicate with the service provider's computers. USSD can be used for WAP browsing, prepaid callback service, mobile-money services, location-based content services, menu-based information services, and as part of configuring the phone on the network.
USSD messages are up to 182 alphanumeric characters long. Unlike Short Message Service (SMS) messages, USSD messages create a real-time connection during a USSD session. The connection remains open, allowing a two-way exchange of a sequence of data. This makes USSD more responsive than services that use SMS.
Technical details
Most GSM phones have USSD capability. USSD is generally associated with real-time or instant messaging services. There is no store-and-forward capability, as is typical of other short-message protocols like SMS. In other words, an SMSC is not present in the processing path.
USSD Phase 1, as specified in GSM 02.90, only supports mobile-initiated ("pull") operations.In the core network, the message is delivered over MAP, USSD Phase 2, as specified in GSM 03.90.After entering a USSD code on a GSM handset, the reply from the GSM operator is displayed within a few seconds.
Format
A typical USSD message starts with an asterisk (*) followed by digits that comprise commands or data. Groups of digits may be separated by additional asterisks. The message is terminated with a number sign (#).
USSD Mode
Mobile-initiated
- USSD/ PULL or USSD/ P2P
- when the user dials a code, e.g. *139# from a GSM mobile handset
Network-initiated
- USSD/ PUSH or USSD/A2P
- when the user receives a push message from the network; primarily used for promotional services
| Example USSD codes |
|---|
| *101# |
| *139*1*1234567890# |
Code table
BS is the type of bearer service, some valid values are:The codes below are NOT USSD codes, but rather MMI codes: they are standardized so they are the same on every GSM phone. They are handled by the handset and not directly by the network. These codes might not always work when using an AT interface; there are standard AT commands defined for each of these actions instead.
- 11 for voice
- 13 for fax
- 16 for SMS (only valid for barring)
- 25 for data
- <leave blank> for all.
T is number of seconds for the No Reply Condition Timer, default is 20 seconds if not specified.
| Code | Function | Note | Switch on | Switch off | Display status |
|---|---|---|---|---|---|
| 002 | all diversions | unconditional, busy, unreachable, does not answer | * * 002 *number * BS * T# | # # 002 * * BS# | * # 002 * *BS # |
| 004 | all conditional redirections | busy, unreachable, does not answer | * * 004 *number * BS * T# | # # 004 * * BS# | * # 004 * *BS # |
| 03 | Change Network password | password is network dependent, default on some networks is 0000. See call barring functions *33 | * * 03 * 330 * old password * new password* new password # | ||
| 04 | Change PIN | * * 04 * old PIN * new PIN * new PIN # | |||
| 042 | Change PIN2 | Only with Phase 2 SIM | * * 042 * old PIN2 * new PIN2 * new PIN2 # | ||
| 05 | Change PIN by PUK | * * 05 * PUK * new PIN * new PIN # | |||
| 052 | Change PIN2 via PUK | Only with Phase 2 SIM | * * 052 * PUK * new PIN2 * new PIN2 # | ||
| 06 | read device number (IMEI) | * # 06 # | |||
| 21 | unconditional divert | all incoming calls will be diverted | * * 21 * number* BS # | # # 21 * * BS # | * # 21 * *BS # |
| 30 | get the caller's number displayed (CLIP) | as a callee get the CLIP displayed | * 30 # | # 30 # | * # 30 # |
| 31 | suppressing the transmission of caller's phone number (CLIR) | for all subsequent calls | # 31 # | * 31 # | * # 31 # |
| 31 | temporary change of the transmission of CLIR | valid just for the next call; no final # | # 31 # number | * 31 # number | |
| 330 | total incoming and outgoing service barring | password is network dependent, default on some networks is 0000 | * 330 *password * BS# | # 330 *password * BS# | * # 330 * *BS # |
| 33 | outgoing call barring | password is network dependent, default on some networks is 0000 | * 33 * password* BS # | # 33 *password * BS# | * # 33 * *BS # |
| 331 | outgoing international call barring | password is network dependent, default on some networks is 0000 | * 331 *password * BS# | # 331 *password * BS# | * # 331 * *BS # |
| 332 | outgoing international call barring, excluding to home | password is network dependent, default on some networks is 0000 | * 332 *password * BS# | # 332 *password * BS# | * # 332 * *BS # |
| 333 | total outgoing service barring | password is network dependent, default on some networks is 0000 | * 333 *password * BS# | # 333 *password * BS# | * # 333 * *BS # |
| 35 | incoming call barring | password is network dependent, default on some networks is 0000. Incompatible with call diversion | * 35 * password* BS # | # 35 *password * BS# | * # 35 * *BS # |
| 351 | incoming call barring, when international roaming | password is network dependent, default on some networks is 0000 | * 351 *password * BS# | # 351 *password * BS# | * # 351 * *BS # |
| 353 | total incoming service barring | password is network dependent, default on some networks is 0000 | * 353 *password * BS# | # 353 *password * BS# | * # 353 * *BS # |
| 37 | Call back on busy (CCBS) | valid on some mobile networks only | * 37 # | # 37 # | * # 37 # |
| 43 | incoming call notification when busy | * 43 * BS # | # 43 * BS # | * # 43 * BS# | |
| 61 | call divert when not answered | * * 61 * number* BS * T # | # # 61 * * BS # | * # 61 * *BS # | |
| 62 | call divert when off or not reachable | * * 62 * number* BS # | # # 62 * * BS # | * # 62 * *BS # | |
| 67 | call divert when busy or pressing reject | * * 67 * number* BS # | # # 67 * * BS # | * # 67 * *BS # | |
| Code | Function | Note | Switch on | Switch off | Display status |
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