The Unstructured Supplementary Service Notify (USSN) is an essential part of the Unstructured Supplementary Service Data (USSD) protocol, which is used in GSM (Global System for Mobile Communications) networks. USSD is widely utilized for sending text between a mobile phone and an application program in the network, enabling services such as mobile banking, menu-based information services, and network configuration services without needing a voice connection or SMS.
USSN, specifically, is a mechanism used by the network to send notifications to the mobile user as part of a USSD session. Here’s a detailed explanation of USSN within the context of USSD:
- USSD Session Initiation:
- A USSD session can be initiated by the user by dialing a code that usually starts with * (asterisk), followed by numbers that denote the specific service, and ends with # (hash). The session can also be initiated by the network, depending on the service’s requirements.
- Real-time Communication:
- USSD establishes a real-time communication session between the mobile user and the application, allowing for a quick and interactive exchange of information. This session remains active until the user ends it or it times out due to inactivity.
- Role of USSN:
- The Unstructured Supplementary Service Notify (USSN) is used by the network to send notifications to the user’s device during an active USSD session. These notifications can include information updates, service prompts, or any messages related to the service being accessed.
- Unlike the Unstructured Supplementary Service Request (USSR), which is user-initiated, USSN messages are generated by the network or the service application to inform or update the user without requiring an immediate response.
- Examples of USSN Usage:
- Notification of account balance after a mobile banking transaction.
- Alerts about promotional offers or service updates from the mobile network operator.
- Confirmations of service activations or changes made during the USSD session.
- Advantages of USSN:
- Immediate Delivery: USSN messages are delivered in real-time, making them ideal for services that require immediate notification or confirmation.
- Simplicity: The USSD protocol, including USSN notifications, operates over the voice channel, ensuring compatibility with even basic mobile phones without the need for internet connectivity.
- Cost-Effectiveness: USSD sessions, including sending and receiving USSN messages, are typically cheaper than SMS messages and do not require data services.
- Session Closure:
- The USSD session can be concluded by the user, the application, or automatically after a timeout period. USSN plays a part in these sessions by providing necessary information without needing user initiation.
In summary, USSN within the USSD protocol serves as a direct channel for networks and service providers to push notifications and important information to users in real-time. This makes USSD a powerful tool for interactive services and instant notifications, accessible to a broad range of mobile users worldwide.