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USS User Supportive Subsystem

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USS (User Supportive Subsystem)

The USS, short for User Supportive Subsystem, is a part of the GSM (Global System for Mobile Communications) network architecture. It is responsible for providing user-related support services and managing interactions between the mobile subscriber and the GSM network. The USS plays a crucial role in ensuring a smooth user experience and delivering various value-added services on the mobile network.

Introduction to USS in GSM

The GSM network is composed of several functional subsystems that work together to provide voice and data services to mobile subscribers. One of these subsystems is the User Supportive Subsystem (USS), which primarily focuses on user interactions and support services. The USS works in conjunction with other GSM subsystems, such as the Base Station Subsystem (BSS), Network Subsystem (NSS), and Operation and Support Subsystem (OSS), to provide comprehensive mobile services.

Functions and Components of USS

The USS performs several essential functions to facilitate user interactions and deliver value-added services:

  1. Authentication and Authorization: When a mobile subscriber accesses the network, the USS is involved in the authentication and authorization process. It verifies the subscriber's identity using the USIM (UMTS Subscriber Identity Module) or SIM card and checks the subscriber's authorization level for accessing various services.
  2. Short Message Service (SMS): The USS manages SMS services, allowing mobile subscribers to send and receive text messages. It handles the storage, routing, and delivery of SMS messages between mobile devices.
  3. Supplementary Services: The USS provides supplementary services to mobile subscribers, such as call forwarding, call waiting, call hold, conference calls, and caller ID display. These services enhance the calling experience and add additional functionalities to voice communications.
  4. Mobility Management: The USS handles various mobility-related functions, such as location registration, location updating, and handover procedures. It ensures seamless connectivity as a mobile subscriber moves between different cells or areas covered by the GSM network.
  5. Billing and Charging: The USS collects usage data from the NSS and BSS to calculate call duration, data usage, and other service-related information for billing purposes. It interacts with the Billing Subsystem (BS) to generate accurate billing records for mobile subscribers.
  6. Roaming Support: For mobile subscribers roaming on other GSM networks, the USS facilitates authentication and authorization with the home network, ensuring a smooth user experience while roaming.
  7. Value-Added Services: The USS enables the provision of various value-added services, such as mobile internet access, multimedia messaging (MMS), and mobile applications. These services are often provided by third-party service providers, and the USS coordinates the interactions between the subscribers and the service platforms.

Interfaces and Protocols

The USS interfaces with other GSM subsystems through various interfaces and protocols. Some important interfaces include:

  1. A-interface: The interface between the BSS and the NSS, used for call control and mobility management.
  2. B-interface: The interface between different NSS components, used for signaling and control purposes.
  3. C-interface: The interface between the NSS and the OSS, used for operations and maintenance.
  4. D-interface: The interface between the NSS and the USS, enabling interactions for user services.

Conclusion

The User Supportive Subsystem (USS) is an integral part of the GSM network architecture, responsible for providing user-related support services and managing interactions between mobile subscribers and the network. It plays a vital role in ensuring a seamless user experience, delivering value-added services, and facilitating billing and charging functions. By coordinating with other GSM subsystems, the USS enhances the overall efficiency and functionality of the mobile network, meeting the diverse needs of mobile subscribers and supporting various value-added services.