What are subsystems in GSM system?

In the GSM (Global System for Mobile Communications) system, various subsystems work together to enable the functionality and features of the overall mobile network. These subsystems are designed to perform specific tasks, such as managing radio access, controlling mobile stations, and handling network switching. Here are the key subsystems in the GSM system:

1. Mobile Station (MS):

• Definition:
  • The Mobile Station (MS) refers to the user equipment, which includes the mobile phone or device used by the subscriber.
• Components:
  • The MS consists of two main components: the Mobile Equipment (ME) and the Subscriber Identity Module (SIM). The ME includes the physical device (phone), while the SIM stores subscriber-specific information, such as the International Mobile Subscriber Identity (IMSI).

2. Base Station Subsystem (BSS):

• Definition:
  • The Base Station Subsystem (BSS) is responsible for managing the radio communication between the mobile station and the network.
• Components:
  • The BSS consists of two main elements:
    • Base Transceiver Station (BTS): The BTS handles the radio communication with the mobile station.
    • Base Station Controller (BSC): The BSC manages and controls multiple BTSs, handling tasks such as handovers and frequency hopping.

3. Network Switching Subsystem (NSS):

• Definition:
  • The Network Switching Subsystem (NSS) manages the call and connection control functions within the GSM network.
• Components:
  • The NSS consists of the following key elements:
    • Mobile Switching Center (MSC): The MSC performs call switching, handovers, and manages the connection to other networks.
    • Home Location Register (HLR): The HLR stores subscriber-related information, including location and subscriber profiles.
    • Visitor Location Register (VLR): The VLR stores information about subscribers currently within the coverage area.

4. Operation and Maintenance Center (OMC):

• Definition:
  • The Operation and Maintenance Center (OMC) is responsible for monitoring and managing the overall operation of the GSM network.
• Components:
  • The OMC includes systems and tools for monitoring network performance, fault detection, and maintenance activities.

5. Authentication Center (AUC):

• Definition:
  • The Authentication Center (AUC) is responsible for ensuring the security and authentication of mobile subscribers within the network.
• Functionality:
  • The AUC generates and validates security parameters used during the authentication process to protect the network from unauthorized access.

6. Equipment Identity Register (EIR):

• Definition:
  • The Equipment Identity Register (EIR) is responsible for managing the International Mobile Equipment Identity (IMEI) numbers of mobile devices.
• Functionality:
  • The EIR is used for tracking stolen or unauthorized mobile devices and preventing them from accessing the network.

These subsystems collectively form the GSM architecture, facilitating voice and data communication services for mobile subscribers.