Architecture of GSM and Its Main Components

The Global System for Mobile Communications (GSM) is a digital mobile communication standard widely used for mobile phone services. It is structured into three main subsystems:

  1. Mobile Station (MS):

    • Components: The Mobile Station consists of the Mobile Equipment (ME), i.e., the mobile device, and the Subscriber Identity Module (SIM) card, which holds user information such as phone numbers, authentication keys, and service details.
    • Role: The MS enables users to make voice calls, send SMS, and use mobile data through the network.

  2. Base Station Subsystem (BSS):

    • Components: The BSS is responsible for radio communication between the mobile device and the network. It consists of:
      • Base Transceiver Station (BTS): Transmits and receives signals to/from the mobile device.
      • Base Station Controller (BSC): Manages multiple BTSs, controls radio resources, and performs handovers between cells.
    • Role: The BSS ensures efficient radio communication between users and the core network.

  3. Network Subsystem:

    • Components: It includes the Mobile Switching Center (MSC), Home Location Register (HLR), Visitor Location Register (VLR), Authentication Center (AUC), and Equipment Identity Register (EIR).
    • Role: The network subsystem manages call routing, subscriber management, authentication, and mobility handling.

  4. Operations Support Subsystem (OSS):

    • Role: It monitors and maintains the overall GSM network to ensure proper functioning, fault management, and network optimization.

Comparison of GEO, LEO, and MEO Satellites

  • GEO (Geostationary Earth Orbit):

    • Altitude: 35,786 km
    • Applications: Broadcasting, weather monitoring, and telecommunications.
    • Advantages: Continuous coverage, high capacity, and fewer satellites needed.
    • Disadvantages: High latency (around 250-300 ms), expensive, and affected by weather.

  • LEO (Low Earth Orbit):

    • Altitude: 160-2,000 km
    • Applications: Earth observation, satellite internet, and GPS.
    • Advantages: Low latency (20-40 ms), lower launch costs, and less interference.
    • Disadvantages: Limited coverage, frequent handovers, and shorter lifespan.

  • MEO (Medium Earth Orbit):

    • Altitude: 2,000-35,786 km
    • Applications: Navigation (GPS, Galileo).
    • Advantages: Balanced coverage and latency, lower cost than GEO.
    • Disadvantages: Moderate latency, specialized applications, and higher complexity than LEO.