What are the responsibilities of SGSN?

The Serving GPRS Support Node (SGSN) is a crucial element within the General Packet Radio Service (GPRS) network architecture. It plays a central role in managing packet-switched data services, facilitating the efficient transmission of data between mobile devices and external packet data networks. Let’s delve into the responsibilities of the SGSN in greater detail:

1. Mobility Management:

• Location Tracking:
  • One of the primary responsibilities of the SGSN is to track the location of mobile devices within its serving area. This involves updating the current location of each device, allowing the network to know where to forward incoming data packets.
• Routing Area Update:
  • The SGSN handles routing area updates, ensuring that the network maintains accurate information about the location of mobile devices as they move within the GPRS coverage area. This contributes to efficient mobility management.

2. Session Management:

• Session Establishment and Release:
  • The SGSN is responsible for establishing and releasing sessions for GPRS data services. When a mobile device initiates a data session, the SGSN coordinates the setup process, allocating resources and establishing the necessary connections. Similarly, it manages the release of sessions when the data transmission is complete.
• Bearer Activation and Deactivation:
  • The SGSN activates and deactivates bearers for each user session. A bearer represents a logical connection between the mobile device and the GPRS network, providing the necessary resources for data transmission.

3. Packet Routing:

• Packet Forwarding:
  • The SGSN forwards data packets between the mobile device and external packet data networks, such as the Internet. It acts as an intermediary, ensuring that data is transmitted accurately and efficiently.
• Dynamic Assignment of Resources:
  • The SGSN dynamically assigns resources, such as radio channels and transmission paths, based on the current network conditions and the specific requirements of each data session. This contributes to optimal resource utilization.

4. Quality of Service (QoS) Management:

• QoS Parameters:
  • The SGSN manages Quality of Service (QoS) parameters for each user session. This includes determining the priority and characteristics of data traffic, ensuring that different services receive the appropriate level of service based on their requirements.
• Traffic Policing and Shaping:
  • To maintain QoS, the SGSN may perform traffic policing and shaping. This involves monitoring the data traffic to ensure it adheres to the defined QoS parameters and shaping the traffic if needed to meet the specified criteria.

5. Security and Authentication:

• Authentication and Authorization:
  • The SGSN authenticates and authorizes mobile devices during the registration process. It ensures that only valid subscribers with the proper credentials can access GPRS services, contributing to network security.
• Security Context Management:
  • The SGSN manages the security context for each user session. This involves the establishment of encryption keys and security associations to protect the confidentiality and integrity of data during transmission.

6. Charging and Billing Support:

• Volume Measurement:
  • The SGSN supports charging mechanisms by measuring the volume of data transmitted for each user session. This information is crucial for billing purposes.
• Interaction with Charging Gateway:
  • The SGSN interacts with the Charging Gateway (CG), providing necessary charging information related to data sessions. This ensures accurate billing and accounting for GPRS services.

7. Interworking with External Networks:

• Interface with GGSN:
  • The SGSN interfaces with the Gateway GPRS Support Node (GGSN), which acts as a gateway between the GPRS network and external packet data networks. This interface ensures proper routing and delivery of data packets between the GPRS network and the broader internet.

8. Error Handling and Fault Management:

• Error Detection and Recovery:
  • The SGSN is equipped to detect errors and faults within the GPRS network. It implements mechanisms for error recovery, minimizing service disruptions and ensuring the reliability of packet-switched data services.
• Fault Reporting:
  • The SGSN reports faults and issues to the Operation and Maintenance Center (OMC), contributing to the overall management and maintenance of the GPRS network.

In summary, the SGSN in GPRS is a multifaceted element that oversees mobility management, session establishment, packet routing, QoS management, security, charging support, and interworking with external networks. Its comprehensive set of responsibilities ensures the seamless and secure delivery of packet-switched data services to mobile subscribers.