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gprs and gsm

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GSM (Global System for Mobile Communications):

  1. Basics:
    • GSM is a standard for digital cellular networks. It was developed to replace the first-generation (1G) analog cellular networks.
    • The primary advantage of GSM over its predecessor was its ability to use digital technology for better voice quality, encryption, and data services.
  2. Frequency Bands:
    • GSM operates in several frequency bands around the world, including the 900 MHz and 1800 MHz bands.
    • The 900 MHz band is commonly used in Europe, Asia, and Africa, while the 1800 MHz band is used in Europe, Asia, and some other regions.
  3. Multiple Access Methods:
    • GSM uses a combination of Frequency Division Multiple Access (FDMA) for separating different conversations and Time Division Multiple Access (TDMA) for separating conversations over time within the same frequency.
    • TDMA divides a frequency into time slots, and each user is allocated one or more time slots, allowing multiple users to share the same frequency channel.
  4. Architecture:
    • GSM architecture comprises several components like Base Station Subsystem (BSS), Network Switching Subsystem (NSS), and the Operations Support System (OSS).
    • BSS includes Base Transceiver Stations (BTS) and Base Station Controllers (BSC), while NSS consists of Mobile Switching Center (MSC) and Gateway MSC.
  5. Services:
    • Apart from voice calls, GSM supports various services like Short Message Service (SMS), which allows text messages, and Supplementary Services like call forwarding, call waiting, and conference calling.

GPRS (General Packet Radio Service):

  1. Basics:
    • GPRS is an enhancement to GSM that provides packet-switched data services. It enables faster data transmission rates compared to the circuit-switched data services of GSM.
    • GPRS allows users to be always connected to the Internet or other IP-based networks, making it suitable for applications like web browsing, email, and multimedia messaging.
  2. Packet Switching:
    • Unlike GSM, which uses circuit-switched technology, GPRS employs packet-switching technology. In packet-switched networks, data is divided into packets and transmitted over the network.
    • This allows for more efficient use of network resources since bandwidth is allocated on-demand as and when data packets need to be sent or received.
  3. Enhancements:
    • GPRS introduces enhancements like a higher data rate (up to 114 kbps in theory, although real-world speeds are lower), always-on connectivity, and the ability to handle both data and voice simultaneously.
    • It uses the same GSM infrastructure, so it's relatively easy for GSM networks to upgrade to GPRS by adding GPRS support to existing GSM equipment.
  4. Architecture:
    • GPRS architecture includes the GPRS Support Nodes (GSN), which consist of Serving GPRS Support Node (SGSN) and Gateway GPRS Support Node (GGSN).
    • SGSN manages the packet-switched connections with mobile stations within its service area, while GGSN acts as a gateway between the GPRS network and external packet data networks, like the Internet.
  5. Charging Model:
    • GPRS introduced a different charging model compared to GSM. Instead of charging based on the duration of the connection (as in GSM), GPRS charges users based on the volume of data transferred.