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2g systems

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Technical details of 2G (Second Generation) mobile systems, focusing on the widely adopted GSM (Global System for Mobile Communications) standard:

GSM (Global System for Mobile Communications):

1. Digital Modulation Techniques:

  • FDMA (Frequency Division Multiple Access): Divides the frequency spectrum into channels, and each user is assigned a specific frequency channel.
  • TDMA (Time Division Multiple Access): Divides time into slots, allowing multiple users to share the same frequency by transmitting in different time slots.

2. Network Architecture:

  • Base Station Subsystem (BSS): Comprises Base Transceiver Stations (BTS) and Base Station Controllers (BSC). BTS manages radio communication, while BSC controls multiple BTS and manages handovers.
  • Network Switching Subsystem (NSS): Includes Mobile Switching Center (MSC) responsible for call routing and switching.

3. Digital Voice Compression:

  • PCM (Pulse Code Modulation): Converts analog voice signals into digital form, allowing for more efficient transmission and better voice quality.
  • Full Rate and Half Rate Codecs: Introduced to optimize bandwidth usage for voice transmission.

4. Signaling:

  • SS7 (Signaling System 7): Used for call setup, management, and teardown.
  • MAP (Mobile Application Part): A protocol within SS7, responsible for mobility management and other mobile-specific functions.

5. Frequency Bands:

  • GSM Bands: GSM operates in various frequency bands, including 850 MHz, 900 MHz, 1800 MHz, and 1900 MHz.

6. Handovers:

  • Hard Handover: Involves a clear break from the current connection before establishing a new one.
  • Soft Handover: Allows mobile devices to communicate with multiple base stations simultaneously during handovers, contributing to improved call quality and reliability.

7. SIM (Subscriber Identity Module):

  • Security and Authentication: The use of SIM cards for subscriber identity and authentication, contributing to the security of mobile communication.

8. SMS (Short Message Service):

  • Introduction of SMS: 2G introduced SMS, allowing users to send and receive short text messages.

9. Cell Sizes and Frequency Reuse:

  • Cellular Networks: Divided into cells to efficiently use radio frequency resources.
  • Frequency Reuse: Reuses the same frequency channels in different cells, maximizing spectrum utilization.

10. Security Measures:

  • A5 Encryption Algorithm: Used to secure voice communication over the air, providing a level of privacy for users.

Technical Highlights:

  1. Digital Transition:
    • 2G represented a shift from analog to digital communication, improving voice quality, reducing interference, and enabling the development of data services.
  2. Efficient Spectrum Usage:
    • FDMA and TDMA techniques allowed for efficient spectrum usage, accommodating multiple users in the same frequency bands.
  3. Interoperability:
    • GSM, a widely adopted 2G standard, promoted interoperability, allowing users to roam seamlessly across different networks and countries.
  4. Data Evolution - GPRS:
    • The introduction of GPRS (General Packet Radio Service) within 2G paved the way for packet-switched data services, setting the stage for the mobile internet era.
  5. Foundation for Mobile Communication:
    • 2G laid the foundation for the widespread adoption of mobile communication, introducing digital voice, efficient spectrum utilization, and the beginning of data services.

While GSM is a key example of 2G technology, it's important to note that other standards, such as CDMA (Code Division Multiple Access), were also prevalent in some regions. However, GSM's global adoption and interoperability played a significant role in shaping the 2G landscape.