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Global System for Mobile communications . GSM. ... Release 99 introduced higher speed data transmission using Enhanced Data Rates for GSM Evolution (EDGE ... – PowerPoint PPT presentation

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Title: (GPRS, EDGE, UMTS, LTE and

  • Global System for Mobile communications

GSM History
Year Events
1982 CEPT establishes a GSM group in order to develop the standards for a pan-European cellular mobile system
1985 Adoption of a list of recommendations to be generated by the group
1986 Field tests were performed in order to test the different radio techniques proposed for the air interface
1987 TDMA is chosen as access method (in fact, it will be used with FDMA) Initial Memorandum of Understanding (MoU) signed by telecommunication operators (representing 12 countries)
1988 Validation of the GSM system
1989 The responsibility of the GSM specifications is passed to the ETSI
1990 Appearance of the phase 1 of the GSM specifications
1991 Commercial launch of the GSM service
1992 Enlargement of the countries that signed the GSM- MoUgt Coverage of larger cities/airports
1993 Coverage of main roads GSM services start outside Europe
1995 Phase 2 of the GSM specifications Coverage of rural areas
GSM world coverage map
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Differences Between First and Second Generation
  • Digital traffic channels first-generation
    systems are almost purely analog
    second-generation systems are digital
  • Encryption all second generation systems
    provide encryption to prevent eavesdropping
  • Error detection and correction
    second-generation digital traffic allows for
    detection and correction, giving clear voice
  • Channel access second-generation systems allow
    channels to be dynamically shared by a number of

GSM network
  • The GSM network can be divided into four
  • The Mobile Station (MS).
  • The Base Station Subsystem (BSS).
  • The Network and Switching Subsystem (NSS).
  • The Operation and Support Subsystem (OSS).

GSM Network Architecture
Mobile Station
  • Mobile station communicates across Um interface
    (air interface) with base station transceiver in
    same cell as mobile unit
  • Mobile equipment (ME) physical terminal, such
    as a telephone or PCS
  • ME includes radio transceiver, digital signal
    processors and subscriber identity module (SIM)
  • GSM subscriber units are generic until SIM is
  • SIMs roam, not necessarily the subscriber devices

Base Station Subsystem (BSS)
  • BSS consists of base station controller and one
    or more base transceiver stations (BTS)
  • Each BTS defines a single cell
  • Includes radio antenna, radio transceiver and a
    link to a base station controller (BSC)
  • BSC reserves radio frequencies, manages handoff
    of mobile unit from one cell to another within
    BSS, and controls paging
  • The BSC (Base Station Controller) controls a
    group of BTS and manages their radio ressources.
    A BSC is principally in charge of handovers,
    frequency hopping, exchange functions and control
    of the radio frequency power levels of the BTSs.

Network Subsystem (NS)
  • NS provides link between cellular network and
    public switched telecommunications networks
  • Controls handoffs between cells in different BSSs
  • Authenticates users and validates accounts
  • Enables worldwide roaming of mobile users
  • Central element of NS is the mobile switching
    center (MSC)

Mobile Switching Center (MSC) Databases
  • Home location register (HLR) database stores
    information about each subscriber that belongs to
  • Visitor location register (VLR) database
    maintains information about subscribers currently
    physically in the region
  • Authentication center database (AuC) used for
    authentication activities, holds encryption keys
  • Equipment identity register database (EIR)
    keeps track of the type of equipment that exists
    at the mobile station

The Operation and Support Subsystem (OSS)
  • The OSS is connected to the different components
    of the NSS and to the BSC, in order to control
    and monitor the GSM system. It is also in charge
    of controlling the traffic load of the BSS.
  • However, the increasing number of base stations,
    due to the development of cellular radio
    networks, has provoked that some of the
    maintenance tasks are transferred to the BTS.
    This transfer decreases considerably the costs of
    the maintenance of the system.

GSM Channel Types
  • Traffic channels (TCHs)
  • carry digitally encoded user speech or user data
    and have identical functions and formats on both
    the forward and reverse link.
  • Control channels (CCHs)
  • carry signaling and synchronizing commands
    between the base station and the mobile station.
    Certain types of control channels are defined for
    just the forward or reverse link.

How a Cellular Telephone Call is Made
  • All base stations continuously send out
    identification signals (ID) of equal, fixed
    strength. When a mobile unit is picked up and
    goes off-hook, it senses these identification
    signals and identifies the strongest. This tells
    the phone which cell it is in and should he
    associated with. The phone then signals to that
    cell's base station with its ID code, and the
    base station passes this to the MSC, which keeps
    track of this phone and its present cell in its
    database. The phone is told what channel to use
    for talking, is given a dial tone, and the call
    activity proceeds just like a regular call. All
    the nontalking activity is done on a setup
    channel with digital codes.

  • Mobile unit initialisation
  • Mobile-originated call
  • Paging
  • Call accepted
  • Ongoing call
  • Handoff

GSM Radio interface
  • Frequency allocation
  • Two frequency bands, of 25 Mhz each one, have
    been allocated for the GSM system
  • The band 890-915 Mhz has been allocated for the
    uplink direction (transmitting from the mobile
    station to the base station).
  • The band 935-960 Mhz has been allocated for the
    downlink direction (transmitting from the base
    station to the mobile station).

Multiple access scheme
  • In GSM, a 25 MHz frequency band is divided, using
    a FDMA, into 124 carrier frequencies spaced one
    from each other by a 200 kHz frequency band.
  • Each carrier frequency is then divided in time
    using a TDMA. This scheme splits the radio
    channel into 8 bursts.
  • A burst is the unit of time in a TDMA system, and
    it lasts approximately 0.577 ms.
  • A TDMA frame is formed with 8 bursts and lasts,
    consequently, 4.615 ms.
  • Each of the eight bursts, that form a TDMA frame,
    are then assigned to a single user.

GSM bands
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Maximum number of simultaneous calls (124)
8 / N 330 (if N3)
Multiframe components
GSM frame format
TDMS format
Trail bits synchronisation between mobile and BS.
Encrypted bits data is encrypted in blocks, Two
57-bit fields
Stealing bit indicate data or stolen for urgent
control signaling
Training sequence a known sequence that differs
for different adjacent cells. It indicates the
received signal is from the correct transmitter
and not a strong interfering transmitter. It is
also used for multipath equalisation. 26 bits.
Guide bits avoid overlapping, 8.25 bits
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Data rate
  • channel data rate in GSM
  • (1/120 ms) 26 8 156.26 270.8 33Kbps
  • User data rate
  • Each user channel receives one slot per frame

With error control
Traffic Channels
  • full rate channels offer a data rate of 22.8
  • speech data used as 13 kBit/s voice data plus
    FEC data
  • packet data used as 12, 6, or 3.6 kBit/s plus
    FEC data
  • half rate channels offer 11.4 kBit/s
  • speech data improved codecs have rates of 6.5
    kBit/s, plus FEC
  • packet data can be transmitted at 3 or 6 kBit/s
  • Two half rate channels can share one physical
  • Consequence to achieve higher packet data
    rates, multiple logical channels have to be
    allocated ) this is what GPRS does

Speech coding
  • There are 260 bits coming out of a voice coder
    every 20 ms.
  • 260 bits/20ms 13 kbps
  • These 260 bits are divided into three classes
  • Class Ia having 50 bits and are most sensitive to
  • 3-bit CRC error detection code 53, then
    protected by a Convolutional (2,1,5) error
    correcting code.
  • Class Ib contains 132 bits which are reasonably
    sensitive to bit errors--protected by a
    Convolutional (2,1,5) error correcting code.
  • Class II contains 78 bits which are slightly
    affected by bit errors unprotected
  • After channel coding 260 bits

Channel coding block coding Then Convolutional
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Signal Processing in GSM
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Global Wireless Frequency Bands
Evalution to 2.5G mobile Radio Networks
  • Newer versions of the standard were
    backward-compatible with the original GSM phones.
  • Release 97 of the standard added packet data
    capabilities, by means of General Packet Radio
    Service (GPRS). GPRS provides data transfer rates
    from 56 up to 114 kbit/s.
  • Release 99 introduced higher speed data
    transmission using Enhanced Data Rates for GSM
    Evolution (EDGE), Enhanced GPRS (EGPRS), IMT
    Single Carrier (IMT-SC), four times as much
    traffic as standard GPRS. accepted by the ITU as
    part of the IMT-2000 family of 3G standards
  • Evolved EDGE standard providing reduced latency
    and more than doubled performance e.g. to
    complement High-Speed Packet Access (HSPA). Peak
    bit-rates of up to 1Mbit/s and typical bit-rates
    of 400kbit/s can be expected.

  • the Base Station Subsystem (the base stations and
    their controllers).
  • the Network and Switching Subsystem (the part of
    the network most similar to a fixed network).
    This is sometimes also just called the core
  • the GPRS Core Network (the optional part which
    allows packet based Internet connections).all of
    the elements in the system combine to produce
    many GSM services such as voice calls and SMS.

ITUs View of Third-Generation Capabilities
  • Voice quality comparable to the public switched
    telephone network
  • High data rate. 144 kbps data rate available to
    users in high-speed motor vehicles over large
    areas 384 kbps available to pedestrians standing
    or moving slowly over small areas Support for
    2.048 Mbps for office use
  • Symmetrical / asymmetrical data transmission
  • Support for both packet switched and circuit
    switched data services
  • An adaptive interface to the Internet to reflect
    efficiently the common asymmetry between inbound
    and outbound traffic
  • More efficient use of the available spectrum in
  • Support for a wide variety of mobile equipment
  • Flexibility to allow the introduction of new
    services and technologies

Third Generation Systems (3G)
  • The dream of 3G is to unify the world's mobile
    computing devices through a single, worldwide
    radio transmission standard. However,
  • 3 main air interface standards
  • W-CDMA(UMTS) for Europe
  • CDMA2000 for North America
  • TD-SCDMA for China (the biggest market)

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UMTS (Universal Mobile Telecommunications System
) Services
UMTS offers teleservices (like speech or SMS) and
bearer services, which provide the capability for
information transfer between access points. It is
possible to negotiate and renegotiate the
characteristics of a bearer service at session or
connection establishment and during ongoing
session or connection. Both connection oriented
and connectionless services are offered for
Point-to-Point and Point-to-Multipoint
communication. Bearer services have different QoS
parameters for maximum transfer delay, delay
variation and bit error rate. Offered data rate
targets are144 kbits/s satellite and rural
outdoor384 kbits/s urban outdoor2048 kbits/s
indoor and low range outdoor
UMTS Architecture
Core Network
The Core Network is divided in circuit switched
and packet switched domains. Some of the circuit
switched elements are Mobile services Switching
Centre (MSC), Visitor location register (VLR) and
Gateway MSC. Packet switched elements are Serving
GPRS Support Node (SGSN) and Gateway GPRS Support
Node (GGSN). Some network elements, like EIR,
HLR, VLR and AUC are shared by both domains.The
Asynchronous Transfer Mode (ATM) is defined for
UMTS core transmission. ATM Adaptation Layer type
2 (AAL2) handles circuit switched connection and
packet connection protocol AAL5 is designed for
data delivery.
Summary of UMTS frequencies
Universal Mobile Telephone System (UMTS)
  • 1920-1980 and 2110-2170 MHz Frequency Division
    Duplex (FDD, W-CDMA) Paired uplink and downlink,
    channel spacing is 5 MHz and raster is 200 kHz.
    An Operator needs 3 - 4 channels (2x15 MHz or
    2x20 MHz) to be able to build a high-speed,
    high-capacity network.1900-1920 and 2010-2025
    MHz Time Division Duplex (TDD, TD/CDMA) Unpaired,
    channel spacing is 5 MHz and raster is 200 kHz.
    Tx and Rx are not separated in frequency.1980-201
    0 and 2170-2200 MHz Satellite uplink and downlink.

W-CDMA Parameters
Base station finder http//www.sitefinder.ofcom.
Frequency Spectrum in UK(Sep 2007)
900MHz 1800MHz 2100MHz ( 3G )
Vodafone Vodafone Vodafone
O2 O2 O2
Restricted to 2G services only T-Mobile T-Mobile
  Orange Orange
    Restricted to 3G services only
GSM frequency allocations
Mobile phone transmit  frequency MHz Base station transmit frequency MHz
Vodafone GSM 900 890 - 894.6        935 - 939.6
O2 (BT) GMS 900 894.8 - 902 939.8 - 947
Vodafone GSM 900 902 - 910 947 - 955
O2 (BT) GMS 900 910 - 915 955 - 960

Vodafone GSM 1800       O2 GSM 1800 1710 - 1721.5 1805 - 1816.5
T Mobile GSM 1800 1721.5 - 1751.5 1816.5 - 1846.5
Orange GSM 1800 1751.5 - 1781.5 1846.5 - 1876.5

The UMTS/3G frequency allocations
Frequency (MHz) Bandwidth (MHz) licence holder
1900 - 1900.3 Guard band
1900.3 - 1905.2 4.9 licence D T-Mobile
1905.2 - 1910.1 4.9 licence E Orange
1910.1 - 1915.0 4.9 licence C O2
1915.0 - 1919.9 4.9 licence A 3
1919.9 - 1920.3 Guard band
1920.3 - 1934.9 14.6 licence A 3
1934.9 - 1944.9 10 licence C O2
1944.9 - 1959.7 14.8 licence B Vodafone
1959.7 - 1969.7 10 licence D T-Mobile
1969.7 - 1979.7 10 licence E Orange
2110 - 2110.3 Guard band
2110.3 - 2124.9 14.6 licence A 3
2124.9 - 2134.9 10 licence C O2
2134.9 - 2149.7 14.8 licence B Vodafone
2149.7 - 2159.7 10 licence D T-Mobile
2159.7 - 2169 10 licence E Orange
2169.7 - 2170 Guard band
Signal level measured at T701
A mobile virtual network operator (MVNO) is a
mobile phone operator that provides services
directly to their own customers but does not own
key network assets such as a licensed frequency
allocation of radio spectrum and the cell tower
infrastructure. The UK mobile market has 5 main
mobile network operators and has a total of more
than 60 MVNOs.
Market share per mobile provider
Everything Everywhere (T-mobile Orange, inc
Virgin Mobile) 38 O2 (inc Tesco) 30, Vodafone
(inc ASDA, 25, 3UK 7 (end 2010) (from Ofcom
The Communications Market Report United
Kingdom 2011)
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LTE (Long Term Evolution)
  • Initiated in 2004
  • focused on enhancing the Universal Terrestrial
    Radio Access (UTRA)
  • Downlink (100Mbps), OFDM, support data modulation
    schemes QPSK, 16QAM, and 64QAM
  • Uplink (50Mbps) Single Carrier-Frequency Division
    Multiple Access (SC-FDMA), support BPSK, QPSK,
    8PSK and 16QAM

  • 4 x Increased Spectral Efficiency, 10 x Users Per
  • Multiple Input / Multiple Output (MIMO) antenna
  • both paired (FDD) and unpaired (TDD) band
    operation is supported
  • LTE can co-exist with earlier 3GPP radio
  • 3GPPs core network has been undergoing System
    Architecture Evolution (SAE), optimizing it for
    packet mode and in particular for the
    IP-Multimedia Subsystem (IMS) which supports all
    access technologies even wire-line

International Mobile Telecommunications (IMT)

  • Key features of IMT-Advanced
  • a high degree of commonality of functionality
    worldwide while retaining the flexibility to
    support a wide range of services and applications
    in a cost efficient manner
  • compatibility of services within IMT and with
    fixed networks
  • capability of interworking with other radio
    access systems
  • high quality mobile services
  • user equipment suitable for worldwide use
  • user-friendly applications, services and
  • worldwide roaming capability and,
  • enhanced peak data rates to support advanced
    services and applications (100 Mbit/s for high
    and 1 Gbit/s for low mobility were established as
    targets for research).

The Forth Generation
  • 4G is mainly a marketing buzzword at the moment.
    Some basic 4G research is being done, but no
    frequencies have been allocated.
  • Smart antennas
  • Multiple-Input-Multiple-Output Systems
  • Space-Time Coding
  • Dynamic Packet Assignment
  • Wideband OFDM

OFDM for 4G Wireless
  • OFDM is being increasingly used in high -speed
    information transmission systems
  • European HDTV
  • Digital Audio Broadcast (DAB)
  • Digital Subscriber Loop (DSL)
  • IEEE 802.11 Wireless LAN

Key Features of 4G W-OFDM
  • IP packet data centric
  • Support for streaming, simulcasting generic
  • Peak downlink rates of 5 to 10 Mbps
  • Full macro-cellular/metropolitan coverage
  • Asymmetric with 3G uplinks (EDGE)
  • Variable bandwidth - 1 to 5 MHz
  • Adaptive modulation/coding
  • Smart/adaptive antennas supported
  • MIMO/BLAST/space-time coding modes
  • Frame synchronized base stations using GPS
  • Network assisted dynamic packet assignment
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