GSM: Global System for Mobile Communications
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Questions and Answers

What is the full form of GSM?

  • General Standard for Multimedia
  • Global System for Mobile (correct)
  • General System for Multimedia
  • Global Standard for Mobile

    • GSM was primarily designed as a circuit-switched system.

    True

    What is the term used for the extension of GSM that is packet-switched?

    General Packet Radio Service (GPRS)

    GSM is still the most widely used wireless technology worldwide, although in recent years 4G LTE networks have become tremendously popular. In addition, a new service called Voice over LTE (VoLTE) has been standardized to support __________ calls via the LTE radio network.

    <p>voice</p> Signup and view all the answers

    What is the fixed transmission speed of a DS0 channel in a classic circuit-switched telecommunication network?

    <p>64 kbit/s</p> Signup and view all the answers

    Which of the following units is used as the reference unit for a telecommunication network in Europe?

    <p>E-1 connection</p> Signup and view all the answers

    An E-1 connection in Europe has a gross datarate of 1.544 Mbit/s.

    <p>False</p> Signup and view all the answers

    The SS-7 signaling standard defines three basic types of network nodes: Service Switching Points (SSPs), Service Control Points (SCPs), and Signaling __________ Points (STPs).

    <p>Transfer</p> Signup and view all the answers

    What is the MTP-3 protocol responsible for in the OSI model?

    <p>Packet routing</p> Signup and view all the answers

    What type of addresses does the MTP-3 protocol use to identify the source and destination of a message?

    <p>Point codes</p> Signup and view all the answers

    Which protocol is used for the establishment or clearing of a call? Integrated Services Digital Network ____ Part (ISUP).

    <p>User</p> Signup and view all the answers

    SCCP uses port numbers like TCP and UDP in the IP world to distinguish different applications.

    <p>False</p> Signup and view all the answers

    Match the SS-7 protocol with its primary function:

    <p>MAP = Communication between MSC and HLR for subscriber information BSSMAP = Communication between MSC and radio network to establish radio channels DTAP = Communication between user's mobile device and MSC for transparent communication</p> Signup and view all the answers

    What is the abbreviation used to refer to the IP-based SS-7 protocol stack?

    <p>SIGTRAN</p> Signup and view all the answers

    In an IP-based network, voice calls are transmitted in IP packets.

    <p>True</p> Signup and view all the answers

    What does BICC stand for and how does it relate to ISUP?

    <p>Bearer-Independent Call Control; BICC largely resembles ISUP.</p> Signup and view all the answers

    The responsible nodes called Signaling Gateways (______) bridge E-1-based and IP-based SS-7 communication.

    <p>SGWs</p> Signup and view all the answers

    Match the components with their description:

    <p>MSC = Central element of a mobile telecommunication network HLR = Database responsible for subscriber management VLR = Registers mobile subscribers and is responsible for mobility management MGW = Handles both IP-based and E-1-based voice calls transparently</p> Signup and view all the answers

    What does IMSI stand for?

    <p>International Mobile Subscriber Identity</p> Signup and view all the answers

    The MSISDN includes the country code, NDC, and the subscriber number.

    <p>True</p> Signup and view all the answers

    The IMSI is unique in the network and has a : relationship with the MSISDN in the HLR.

    <p>1:1</p> Signup and view all the answers

    What does MNP stand for and what does it allow subscribers to retain?

    <p>Mobile Number Portability; MSISDN</p> Signup and view all the answers

    What is the purpose of quantization in the processing of analog voice signals?

    <p>To convert analog samples into digital values</p> Signup and view all the answers

    What is the name of the 8-bit digital representation of analog samples in the described process?

    <p>Pulse Code-Modulated (PCM) signal</p> Signup and view all the answers

    Which standards describe the representation of volume by digital 8-bit values in voice signals?

    <p>A-law standard for European networks</p> Signup and view all the answers

    Voice calls between networks using different standards do not face any compatibility issues.

    <p>False</p> Signup and view all the answers

    The __ is responsible for creating billing records for each call in a mobile voice network.

    <p>Mobile Switching Center (MSC)</p> Signup and view all the answers

    How many MHz of bandwidth does the 1800 MHz band offer for GSM?

    <p>75</p> Signup and view all the answers

    Which organization developed the Voice Group Call Service (VGCS) for GSM-R?

    <p>3GPP</p> Signup and view all the answers

    GSM networks were originally intended only as a European standard.

    <p>True</p> Signup and view all the answers

    GSM networks use ________ and ________ multiple access schemes for communication.

    <p>frequency division, time division</p> Signup and view all the answers

    What are the components involved in the authentication process between a subscriber and the network?

    <p>SIM/Mobile device, HLR/AuC, and MSC</p> Signup and view all the answers

    What is the purpose of the RAND value in the authentication process?

    <p>To serve as a 128-bit random number used in generating the authentication triplet.</p> Signup and view all the answers

    The Ki key is transmitted over interfaces in plaintext during authentication.

    <p>False</p> Signup and view all the answers

    What does SRES stand for in the authentication process? The signed response (_____)

    <p>SRES: The signed response (SRES) is generated by using Ki, RAND, and the A3 authentication algorithm.</p> Signup and view all the answers

    What is one of the most important parameters for mobile operators when dimensioning their network?

    <p>number of minutes per hour that a subscriber statistically uses the system</p> Signup and view all the answers

    What is the commonly used value for the number of minutes per hour that a subscriber uses the system?

    <p>3</p> Signup and view all the answers

    How many times the number of active subscribers can a base station provide service to if each subscriber uses the system for 3 minutes per hour?

    <p>20</p> Signup and view all the answers

    How many subscribers can a base station with 54 channels provide service to if each subscriber uses the system for 3 minutes per hour?

    <p>1080</p> Signup and view all the answers

    What was the subscriber base of Telefonica O2 Germany in 2014?

    <p>20 million</p> Signup and view all the answers

    Based on the given information, how many base stations would be required to serve the subscriber base of Telefonica O2 Germany in 2014?

    <p>The total number of base stations required to serve the subscriber base of Telefonica O2 Germany in 2014 is incomplete in the provided text.</p> Signup and view all the answers

    Study Notes

    Global System for Mobile Communications (GSM)

    • Triggered an unprecedented change in mobile communication in the 1990s
    • Widely used by billions of people worldwide, with steady improvements in technology and decreasing prices

    Circuit-Switched Data Transmission

    • GSM initially designed as a circuit-switched system, similar to fixed-line phone networks
    • Establishes a direct and exclusive connection between two users on every interface between all network nodes
    • Switching center uses a switching matrix to connect any originating party to any destination party
    • The approach is identical in both mobile and fixed-line networks

    Classic Circuit Switching

    • Fixed-line telecommunication networks were designed only for voice communication, using analog connections
    • Analog technology was superseded by digital technology in the switching center in the mid-1980s
    • GSM reused much of the fixed-line technology, with the main development being the means to wirelessly connect subscribers to the network

    Mobility Management

    • In a GSM network, subscribers are mobile and can change their location at any time
    • It is not possible to use the same input and output in the switching matrix for a user for each call as in fixed-line networks
    • A flexible mobility management architecture in the core network is necessary, which needs to be aware of the current location of the subscriber

    Virtual Circuit Switching over IP

    • While voice calls remain important, other forms of communication like email, instant messaging, and social networks play a bigger role
    • The Internet is based on transferring individual data packets, using the destination address contained in each packet to forward the packet
    • Virtual circuit switching allows voice calls to be transferred over IP packets, replacing the physical presence of a circuit-switched infrastructure

    Standards

    • Standardization of interfaces and procedures is necessary for global roaming and international calls
    • The International Telecommunication Union (ITU) defines standards, including the Signaling System Number 7 (SS-7)
    • GSM set a common standard for Europe, which was later adopted globally, reducing research and development costs
    • The European Telecommunication Standards Institute (ETSI) was the main body responsible for creating the GSM standard

    Transmission Speeds

    • The smallest transmission speed unit in a classic circuit-switched telecommunication network is the digital signal level 0 (DS0) channel, with a fixed transmission speed of 64 kbit/s
    • An E-1 connection in Europe and a T-1 connection in the United States are used, with gross datarates of 2.048 Mbit/s and 1.544 Mbit/s, respectively
    • Optical systems using the synchronous transfer mode (STM) standard are used for higher transmission speeds and long distances

    The Signaling System Number 7 (SS-7)

    • Used for establishing, maintaining, and clearing connections in fixed-line and mobile networks
    • Signaling information is exchanged between the end user and network devices using a separate dedicated signaling channel
    • SS-7 is used in GSM networks, with enhancements by ETSI to fulfill the special requirements of mobile networks
    • Three basic types of network nodes are defined: Service Switching Points (SSPs), Service Control Points (SCPs), and Signaling Transfer Points (STPs)### SS-7 Protocol Stack
    • The SS-7 protocol stack is used in circuit-switched telecommunication networks for communication between network nodes.
    • The stack consists of several protocols and layers, similar to the OSI 7-layer model.
    • The Message Transfer Part 1 (MTP-1) protocol describes the physical properties of the transmission medium on layer 1 of the OSI model.
    • MTP-1 standardizes cable definitions, signal levels, and transmission speeds.
    • On layer 2, the data link layer, messages are framed into packets with start and stop identification.
    • Layer 3, the network layer, is responsible for packet routing and uses the MTP-3 protocol.
    • MTP-3 uses point codes to identify the source and destination of a message, similar to IP addresses.

    SS-7 Protocols for GSM

    • The Mobile Application Part (MAP) protocol is used for communication between an MSC and the HLR, which maintains subscriber information.
    • MAP is used to query the HLR for subscriber information, such as the current location of a subscriber.
    • The Base Station Subsystem Mobile Application Part (BSSMAP) protocol is used for communication between the MSC and the radio network.
    • BSSMAP is necessary to establish a dedicated radio channel for a new connection to a mobile subscriber.
    • The Direct Transfer Application Part (DTAP) protocol is used between the mobile station and the MSC to communicate transparently.

    IP-Based SS-7 Protocol Stack

    • When an IP network is used for the transmission of SS-7 signaling messages, the MTP-1 and MTP-2 protocols are replaced by the IP and transport-medium-dependent lower-layer protocols.
    • The Stream Control Transmission Protocol (SCTP) is used as a transport protocol in the IP stack.
    • The M3UA (MTP-3 User Adaptation Layer) protocol is used to transfer information contained in the classic MTP-3 protocol.
    • The IP-based SS-7 protocol stack is often referred to as SIGTRAN (signaling transmission).

    Network Architecture

    • A GSM network is split into three subsystems: the Base Station Subsystem (BSS), the Network Subsystem (NSS), and the Intelligent Network Subsystem (IN).
    • The BSS contains all nodes and functionalities necessary for wireless connection of mobile subscribers to the network.
    • The NSS contains all nodes and functionalities necessary for switching of calls, subscriber management, and mobility management.
    • The IN comprises SCP databases that add optional functionality to the network, such as prepaid services.### Interfaces and Nodes in a Mobile Network
    • Figure 1.9 shows the interfaces and nodes in a classic NSS (Network and Switching Subsystem) architecture
    • The nodes include:
      • BSS (Base Station Subsystem)
      • PSTN (Public Switched Telephone Network)
      • VLR (Visitor Location Register)
      • MSC (Mobile Switching Center)
      • HLR (Home Location Register)
    • The interfaces include:
      • A-interface (between BSS and MSC)
      • C-interface (between MSC and HLR)
      • D-interface (between VLR and HLR)
      • E-interface (between MSCs for handover)

    The Mobile Switching Center (MSC)

    • The MSC is the central element of a mobile telecommunication network
    • It is responsible for managing connections between subscribers
    • The MSC is also responsible for:
      • Registration of mobile subscribers
      • Call establishment and call routing
      • Forwarding of SMS messages
      • Mobility Management (MM) of subscribers
    • The MSC is composed of dozens of independent switching centers, each covering a certain area of the network

    Mobile Switching Center (MSC) Server and Gateway

    • In IP-based networks, the MSC has been split into an MSC-Server (MSC-S) and a Media Gateway (MGW)
    • The MSC-S is responsible for signaling and the MGW is responsible for transmitting user data
    • The MGW can convert media streams between different formats (e.g. Narrowband-AMR over IP to G.711/PCM over E-1)

    The Visitor Location Register (VLR)

    • Each MSC has an associated VLR, which holds a copy of the subscriber's record
    • The VLR is used to reduce signaling between the MSC and the HLR
    • The VLR is mainly used to verify the subscriber's record at every connection establishment

    The Home Location Register (HLR)

    • The HLR is the subscriber database of a GSM network
    • It contains a record for each subscriber, with information about the individually available services
    • The HLR is used to store the International Mobile Subscriber Identity (IMSI) of each subscriber
    • The IMSI consists of the Mobile Country Code (MCC), Mobile Network Code (MNC), and Mobile Subscriber Identification Number (MSIN)

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    Description

    Learn about the Global System for Mobile Communications (GSM) and its impact on the way people communicate, from its introduction in the 1990s to its widespread use today.

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