World GSM Subscribers
It is used by over 2 billion
people across more than 212
Global System for Mobile Communications (GSM)
• It started in the early 1980s
• It is the most popular standard for mobile phones in
• The key advantage of GSM systems to consumers
has been higher digital voice quality and low cost
alternatives to making calls,
• GSM is a cellular network, which means that mobile
phones connect to it by searching for cells in the
• GSM networks operate in four different frequency
• 900 MHz or 1800 MHz bands.
• 850 MHz and 1900 MHz bands
• 935–960 MHz
• 890–915 MHz,
GSM Network structure
Base Transceiver Station
Base Station Subsystem(BSS)
• BSS is the section of a traditional cellular telephone network
which is responsible for handling traffic and signaling between a
mobile phone and the NSS.
• Base Transceiver Station(BTS), contains the equipment for
transmitting and receiving of radio signals (transceivers),
antennas, and equipment for encrypting and decrypting
communications with the Base Station Controller .
• The BSC handles allocation of radio channels, receives
measurements from the mobile phones, controls handovers from
BTS to BTS.
• Packet Control Unit (PCU) performs some of the processing
tasks of the BSC, but for packet data.
Network Switching Subsystem(NSS)
• NSS, is the component of a GSM system that carries out
switching functions and manages the communications between
mobile phones and the PSTN. The NSS, also referred to as the
GSM core network.
• MSC is a sophisticated telephone exchange which provides
circuit-switched calling, mobility management, and GSM services
to the mobile phones roaming within the area that it serves.
• The 'Home Location Register' (HLR) is a central database that
contains details of each mobile phone subscriber that is
authorized to use the GSM core network.
• The 'Authentication Centre' ( AUC) is a function to authenticate
each SIM card that attempts to connect to the GSM core network.
• The EIR (Equipment Identity Register) keeps a list of mobile
phones (identified by their IMEI) which are to be banned from the
network or monitored.
GPRS Core Network
• It is the centralized part of the GPRS system and also provides
support for WCDMA based 3G networks. The GPRS core network
is an integrated part of the GSM core network.
• A Gateway GPRS Support Node (GGSN) acts as an interface
between the GPRS backbone network and the external packet
data networks. It converts the GPRS packets coming from the
SGSN into the appropriate packet data protocol and sends them
out on the corresponding packet data network
• Serving GPRS Support Node(SGSN) :Detunnel GTP packets
from the GGSN (downlink),Tunnel IP packets toward the GGSN
(uplink) ,Carry out mobility management as Standby mode mobile
moves from Routing Area to Routing Area, Billing user data
Subscriber Identity Module
• One of the key features of GSM is the Subscriber
Identity Module (SIM), commonly known as a SIM
• The SIM is a detachable smart card containing the
user's subscription information and phonebook.
This allows the user to retain his or her information
after switching handsets
• GPRS is a Mobile Data Service available to users
of Global System for Mobile Communications
(GSM) and IS-136 mobile phones.
• It is an expansion of GSM and a main step to 3G
• 2G cellular systems combined with GPRS is often
described as "2.5G“
• GPRS is packet-switched, which means that
multiple users share the same transmission
channel, only transmitting when they have data to
• The multiple access methods used in GSM with
GPRS are based on frequency division duplex
(FDD) and FDMA.
• During a session, a user is assigned to one pair of
up-link and down-link frequency channels.
• This is combined with packet mode communication,
which makes it possible for several users to share
the same frequency channel.
GPRS can be used for services such as
• Wireless Application Protocol (WAP) access
• Short Message Service (SMS),
• Multimedia Messaging Service (MMS),
• GPRS will enable Internet applications, from web
browsing to chat, location based applications, e-
commerce etc over the mobile network.
• Other new applications for GPRS, include file
transfer and the ability to remotely access and
control/monitor house appliances and machines.
• Enhanced Data rates for GSM Evolution (EDGE) or Enhanced GPRS
• It is a digital mobile phone technology that allows it to increase data
transmission rate and improve data transmission reliability.
• Although technically a 3G network technology it is generally classified as
the unofficial standard 2.75G, due to its slower network speed. EDGE
has been introduced into GSM networks around the world since 2003,
initially in North America.
• It can be used both packet-switched and circuit-switched voice and
data services. High-speed data applications such as video services and
other multimedia benefit from EGPRS' increased data capacity.
• EDGE is an expansion of the GSM/GPRS protocol to support
higher data rates. EDGE is add-on to GPRS
• This is accomplished by utilizing 8-PSK (8-Phase Shift Keying)
modulation technique and modulation coding schemes at the
• Offer data rates of 384kbps, theoretically up to 473.6kbps
• Uses Link adaptation algorithm for packet based radio system.
• Modulation Bit rate – 810kbps
• Radio data rate per time slot – 69.2kbps
• User data rate per time slot – 59.2kbps
• User data rate (8 time slots) – 473.6kbps
Why evolve EDGE?
• Economic forces – less costly than upgrading to UMTS
• Easy to offer global service to subscribers – 82% of world
market is GSM which is already equipped for easy roaming
• Higher data rates and system capacity
• Broadband-like speeds achievable
• Much less expensive mobiles
EDGE In GSM Network
8 -PSK coverage
EDGE Capable TRX,
More capacity in interfaces
to support higher data imageEDGE capable terminal
GSM compatible BTS
BTS -Base Transceiver Station
BSC - Base Station Controller
SGSN - Serving GPRS Support Node
GGSN - Gateway GPRS Support Node
MSC - Mobile Switching Center
Impact of EDGE on existing GSM/GPRS networks
• EDGE requires no hardware or software changes to be made in
GSM core networks, base stations must be modified.
• EDGE compatible transceiver units must be installed
• Software upgrade to the BS and BSC
• The base station subsystem (BSS) hardware(new transceiver in
each cell) needs to be upgraded to support EDGE
• New mobile terminal hardware and software is also required to
decode/encode the new modulation and coding schemes and
carry the higher user data
• It is a digital modulation scheme that transmit data by changing,
• Any digital modulation scheme uses a finite number of distinct
signals to represent digital data.
• PSK uses a finite number of phases, each assigned a unique
pattern of binary bits. Usually, each phase encodes an equal
number of bits.
• Each pattern of bits forms the symbol that is represented by the
particular phase. The demodulator, which is designed
specifically for the symbol-set used by the modulator, determines
the phase of the received signal and maps it back to the symbol it
represents, thus recovering the original data.
Technical differences between GPRS and EDGE
• EDGE is a subsystem within the GSM standard, GPRS has
introduced packet-switched data into GSM networks.
• Basically, EDGE only introduces a new modulation
technique and new channel coding that can be used to
transmit both packet-switched and circuit-switched voice and
• EDGE is an add-on to GPRS and cannot work alone. And is
therefore much easier to introduce than GPRS. GPRS has a
greater impact on the GSM system than EDGE has.
Technical differences between GPRS and EDGE
• EDGE offers significantly higher throughput and capacity.
This decreases the number of radio resources required to
support the same traffic, thus freeing up capacity for more
data or voice services.
• EDGE can transmit three times as many bits as GPRS
during the same period of time. This is the main reason
for the higher EDGE bit rates.
Technical differences between GPRS and EGPRS
• With EDGE, the same time slot can support more users.
• GPRS and EDGE have different protocols and different
behavior on the base station system side.
• On the core network side, GPRS and EDGE share the
same packet-handling protocols and, therefore, behave in
the same way.
• GPRS and EDGE share the same symbol rate, the
modulation bit rate differs.
• Time to market
• Designed for existing spectrum: 800/900/1800/1900 MHz
• Low risk technology evolution from GSM/GPRS
• GSM global scale & scope
• Chipsets, handsets, infrastructure and applications
• Lower capital investment, better vendor selection
• Global roaming
• Short-term benefits: Capacity and performance
• Easy implementation on a GSM/GPRS network
• Cost effective
• Increase the capacity and triples the data rate of GPRS
• Enabling new multimedia services
on the way
E roll-outs on
the way and
Market follows global
war”. Also public
commitments to EDGE
ts to every
No rush to
EDGE, but no
Global EDGE Status
• EDGE transmit both packet-switched and circuit-
switched voice and data services.
• High speed Data rates
• EDGE Evolution continues in Release 7 of the
3GPP standard providing doubled performance e.g.
to complement High-Speed Packet Access
• Voice over IP is planned for EDGE R’2000