GSM Overview and Technology

GSM Overview

• Global System for Mobile Communications (GSM) is a digital cellular technology used for transmitting mobile voice and data services.
• The technology has been implemented globally and is the world's most widely accepted standard for mobile communication.
• The concept of GSM emerged in the early 1970s, with Bell Laboratories developing a cell-based mobile radio system.
• GSM is the name of a standardization group formed in 1982 to develop a common European mobile telephone standard.
• Time-Division Multiple Access (TDMA) is used in GSM to transmit signals, dividing each 200 kHz channel into eight 25 kHz time-slots.
• GSM operates on the mobile communication bands 900 MHz and 1800 MHz in most parts of the world, while using 850 MHz and 1900 MHz in the US.
• GSM supports over one billion mobile subscribers across more than 190 countries worldwide.
• GSM provides fundamental to advanced voice and data services including roaming capabilities.
• Roaming allows GSM users to access their phone number while traveling in different network areas.
• GSM digitizes and compresses data before transmitting it through a channel with two other streams of user data.
• The popularity of GSM is due to its features, including improved spectrum efficiency, international roaming, cost-effective mobile sets and base stations, high-quality speech, and compatibility with other communication services.

GSM Specification

• Modulation is the process of transforming data into a suitable format for transmission.
• Gaussian Minimum Shift Keying (GMSK) is the modulation method used in GSM.
• GSM offers:
  • Voice Teleservices
  • Data Bearer services
  • Supplementary services

GSM Network Architecture

• Mobile Station (MS): The mobile phone used by the subscriber.
• Base Station Subsystem (BSS): Manages radio communication within cells.
  • Base Transceiver Station (BTS): Handles radio links between the MS and the network.
  • Base Station Controller (BSC): Manages radio resources for one or more BTSs.
• Network Switching Subsystem (NSS): Handles call switching and subscriber management.
  • Home Location Register (HLR): Stores permanent data about subscribers.
  • Mobile Services Switching Center (MSC): The central component of the NSS, performing call switching, registration, authentication, location updating, and more.
  • Visitor Location Register (VLR): Stores temporary information about visiting subscribers.
  • Authentication Center (AUC): Protects network security with authentication and encryption.
  • Equipment Identity Register (EIR): Contains a list of valid mobile equipment on the network.
• Operation Support Subsystem (OSS): Provides network monitoring and control for operational and maintenance activities.

GSM Network Components and Interfaces

• Um interface: The air interface or radio link between the MS and the BSS.
• Abis interface: The interface between the BTS and the BSC.
• A interface: The interface between the BSC and the MSC.
• Signaling interface: Interfaces with other networks like ISDN, PSTN, and PDN.
• IWF interface: The interface for connecting to Packet Data Networks (PDN).
• O interface: The interface between the OSS and other network elements.

GSM MS Functions

• Mobile Station (MS) provides a receptor for SMS messages, allowing users to switch between voice and data usage.
• The MS allows access to voicemail systems.
• The MS offers access to data services within the GSM network, including:
  • X.25 packet switching: Through synchronous or asynchronous dial-up connections to the PAD at 9.6 Kbps speed.
  • General Packet Radio Services (GPRSs): Using either X.25 or IP based data transfer methods at up to 115 Kbps speed.
  • High-Speed Circuit Switched Data: Transmission speeds of up to 64 Kbps.

GSM - The Base Station Subsystem (BSS)

• Comprises Base Transceiver Station (BTS) and Base Station Controller (BSC).
• BTS handles radio links with the Mobile Station (MS) and defines a cell in the network.
• BSC manages radio resources for one or more BTSs, controlling frequency hopping, handover, and power transmission.
• BTS functions include:
  • Encoding, encrypting, multiplexing, modulating, and sending RF signals to the antenna.
  • Transcoding and rate adaptation.
  • Time and frequency synchronization.
  • Voice services via full- or half-rate modes.
  • Decoding, decrypting, and equalizing received signals.
  • Random access detection.
  • Timing advances.
  • Uplink channel measurements.
• BSC functions include:
  • Control of frequency hopping.
  • Traffic concentration to reduce lines to the MSC.
  • Interface to the Operations and Maintenance Center.
  • Reallocation of frequencies among BTSs.
  • Time and frequency synchronization.
  • Power management.
  • Time-delay measurements of received signals from the MS.

GSM - The Network Switching Subsystem (NSS)

• The NSS is the core of the GSM network, responsible for switching calls between mobile and other network users, and managing mobile services.
• Mobile Switching Center (MSC): The central component of the NSS, handling switching, authentication, location updating, and roaming.
• Home Location Register (HLR): Stores permanent data about subscribers.
• Visitor Location Register (VLR): Stores temporary data about visiting subscribers.
• Authentication Center (AUC): Protects network security with authentication and encryption.
• Equipment Identity Register (EIR): Contains a list of valid mobile equipment on the network.

GSM - The Operation Support Subsystem (OSS)

• The Operations and Maintenance Center (OMC) is responsible for monitoring and controlling the GSM network.
• OSS provides cost-effective support for central, regional, and local operational and maintenance activities.
• OSS provides a network overview and supports maintenance activities for different organizations.

GSM Additional Components

• SMS Serving Center (SMS SC): Handles Short Message Service (SMS).
• Gateway MSC (GMSC): Handles international calls.
• Chargeback Center (CBC): Handles billing and charging.
• Transcoder and Adaptation Unit (TRAU): Adapts voice signals for different network formats.

This quiz covers the Global System for Mobile Communications (GSM), a widely adopted standard for mobile communication. It explores the technology's history, TDMA signal transmission, and its operation on various frequency bands. Test your knowledge on GSM's role in providing voice and data services globally.