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2g networks

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2G, or second-generation, networks represent the evolution of mobile telecommunications beyond the initial analog systems (1G). The transition to 2G marked a significant improvement in terms of voice quality, data transmission, and the overall efficiency of wireless communication. The two main technologies associated with 2G are GSM (Global System for Mobile Communications) and CDMA (Code Division Multiple Access).

GSM (Global System for Mobile Communications):

  1. Multiple Access Technique:
    • GSM uses Time Division Multiple Access (TDMA) as its multiple access technique. TDMA divides the frequency into time slots, and each user is assigned a specific time slot for transmission.
  2. Frequency Bands:
    • GSM operates in the 900 MHz and 1800 MHz frequency bands. In the United States, GSM uses the 850 MHz and 1900 MHz bands.
  3. Modulation:
    • The modulation scheme used in GSM is Gaussian Minimum Shift Keying (GMSK), which efficiently uses the available bandwidth.
  4. Channels:
    • GSM channels consist of physical channels and logical channels. Physical channels include the Traffic Channels (TCH) for carrying voice and the Control Channels (BCCH, CCCH) for managing the network.
  5. Encryption:
    • GSM incorporates encryption algorithms to secure communication. A5/1 and A5/2 are the encryption algorithms used to protect voice and data.
  6. Data Transmission:
    • GSM supports data transmission using General Packet Radio Service (GPRS). GPRS allows for packet-switched data transmission, enabling services like SMS and mobile internet.

CDMA (Code Division Multiple Access):

  1. Multiple Access Technique:
    • CDMA uses spread spectrum technology for multiple access. Each user is assigned a unique code to transmit and receive data simultaneously over the same frequency.
  2. Frequency Bands:
    • CDMA operates in the 800 MHz and 1900 MHz frequency bands.
  3. Modulation:
    • CDMA uses Quadrature Amplitude Modulation (QAM) for signal modulation.
  4. Channels:
    • CDMA doesn’t use traditional time-division channels like GSM. Instead, each conversation is assigned a unique code and transmitted simultaneously on the same frequency.
  5. Data Transmission:
    • CDMA supports both voice and data transmission. It paved the way for technologies like 1xRTT (1x Radio Transmission Technology) for data services.
  6. Interference and Capacity:
    • CDMA provides better capacity and improved call quality in the presence of interference compared to some other technologies.

Common Features:

  1. Switching:
    • Both GSM and CDMA systems utilize circuit-switched and packet-switched networks for voice and data transmission.
  2. Roaming:
    • 2G networks introduced international roaming capabilities, allowing users to make and receive calls while traveling between different countries.
  3. SMS (Short Message Service):
    • 2G introduced SMS as a standard service, allowing users to send and receive text messages.
  4. SIM Cards:
    • Both GSM and CDMA systems use Subscriber Identity Module (SIM) cards to identify and authenticate users on the network.