USSD stands for Unstructured Supplementary Service Data. It is a mobile-network communication mechanism that lets a mobile-station user communicate with an application defined by the public land mobile network (PLMN) operator. The 3GPP specification describes that communication as transparent to the mobile station and intermediate network entities.
What does USSD mean?
The initials expand to Unstructured Supplementary Service Data. 3GPP, the standards organization behind the relevant specifications, defines USSD as a mechanism for communication between a mobile station (MS) user and a PLMN operator-defined application. A PLMN is a public land mobile network.
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In its Stage 2 specification, 3GPP says the mechanism allows the user and application to communicate “in a way which is transparent to the MS and to intermediate network entities.” It also says USSD allows the development of network-specific supplementary services. 3GPP TS 23.090, Release 18 copy hosted by TEC/TSDSI
How is USSD defined in the standards?
3GPP lists specifications for USSD at two stages: TS 02.90, titled “Unstructured Supplementary Service Data (USSD); Stage 1,” and TS 23.090, titled “Unstructured Supplementary Service Data (USSD); Stage 2.” The 3GPP portal marks TS 23.090 as under change control, so technical details can depend on the specification release being consulted. TS 02.90 listing · TS 23.090 listing
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The NIST CSRC glossary also expands USSD as Unstructured Supplementary Service Data and links the term to its source context. NIST CSRC glossary entry
What does the definition establish—and what does it not?
The standards wording establishes USSD’s basic role: communication between a mobile user and an application defined by the mobile network operator, supporting operator-specific supplementary services. It does not, by itself, establish how a particular operator implements the mechanism or whether a specific service is currently available in a given country or network.
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- Examples: The cited definition does not verify particular contemporary services, such as balance checks, account menus, or payment flows.
- Security: The cited material does not establish that USSD is encrypted, secure, private, or safer than SMS.
- Interaction details: The definition does not provide a complete account of how a session starts, how replies work, how long it lasts, or how it ends.
Those questions require the relevant current specification and, where applicable, documentation from the operator or network concerned.
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