[attachment=1390]

GLOBAL SYSTEM
FOR
MOBILE COMMUNICATION

Definition:
Global system for mobile communication (GSM) is a globally accepted
standard for digital cellular communication. GSM is the name of a
standardization group established in 1982 to create a common European
mobile telephone standard that would formulate specifications for a
pan-European mobile cellular radio system operating at 900 MHz. It is
estimated that many countries outside of Europe will join the GSM
partnership.
1. Introduction: The Evolution of Mobile Telephone Systems
Cellular is one of the fastest growing and most demanding
telecommunications applications. Today, it represents a continuously
increasing percentage of all new telephone subscriptions around the
world. Currently there are more than 45 million cellular subscribers
worldwide, and nearly 50 percent of those subscribers are located in
the United States. It is forecasted that cellular systems using a
digital technology will become the universal method of
telecommunications. By the year 2005, forecasters predict that there
will be more than 100 million cellular subscribers worldwide.
Cellular Subscriber Growth Worldwide
The concept of cellular service is the use of low-power transmitters
where frequencies can be reused within a geographic area. The idea of
cell-based mobile radio service was formulated in the United States at
Bell Labs in the early 1970s. However, the Nordic countries were the
first to introduce cellular services for commercial use with the
introduction of the Nordic Mobile Telephone (NMT) in 1981. Cellular
systems began in the United States with the release of the advanced
mobile phone service (AMPS) system in 1983. The AMPS standard was
adopted by Asia, Latin America, and Oceanic countries, creating the
largest potential market in the world for cellular.
In the early 1980s, most mobile telephone systems were analog rather
than digital, like today's newer systems. One challenge facing analog
systems was the inability to handle the growing capacity needs in a
cost-efficient manner. As a result, digital technology was welcomed.
The advantages of digital systems over analog systems include ease of
signaling, lower levels of interference, integration of transmission
and switching, and increased ability to meet capacity demands.
2. GSM:
Throughout the evolution of cellular telecommunications, various
systems have been developed without the benefit of standardized
specifications. This presented many problems directly related to
compatibility, especially with the development of digital radio
technology. The GSM standard is intended to address these problems.
From 1982 to 1985 discussions were held to decide between building an
analog or digital system. After multiple field tests, a digital system
was adopted for GSM. The next task was to decide between a narrow or
broadband solution. In May 1987, the narrowband time division multiple
access (TDMA) solution was chosen. A summary of GSM milestones is given
in Table
Table GSM Milestones
Year Milestone
1982 GSM formed
1986 field test
1987 TDMA chosen as access method
1988 memorandum of understanding signed
1989 validation of GSM system
1990 preoperation system
1991 commercial system start-up
1992 coverage of larger cities/airports
1993 coverage of main roads
1995 coverage of rural areas
Why has GSM been successful?
The success of GSM is that its development was founded on the delivery
of a specific user benefit - international roaming. The demands of
international roaming had profound changes on GSMâ„¢s architecture and
mandated an open future-proof standard that ensured interoperability,
without stifling competition, and innovation among suppliers. This
lowered barriers to entry, promoted compatibility between systems
which, in turn, lowered development costs and set the stage for better
choice and innovation. The unparalleled economies of scale and
competition that resulted brought convenience and falling prices to
manufacturers, network operators and consumers.
The adoption of a digital system offered improved mobility, spectrum
efficiency,
better quality transmission and new services over the first generation
systems. The
use of Very Large Scale Integration (VLSI) microprocessor technology
and other low
cost IC architectures paved the way for more efficient and affordable
pocket-sized
mobile phones. This resulted in a profound change in usersâ„¢ mobile
communication
style from vehicular-based to personal, opportunity-based
communications.
Although GSM is only one of the pieces in the cluster of current and
future
telecommunications networks, its ability to provide anytime, and almost
anywhere,
communications has resulted in tremendous economic and social
consequences.
Without GSM the pace of development of mobile telephony would have
pared dramatically and that additional revenue streams, such as roaming
(estimated globally at $1.78bn in 2003), would not have been as
successful.
3. The GSM Network:
GSM provides recommendations, not requirements. The GSM specifications
define the functions and interface requirements in detail but do not
address the hardware. The reason for this is to limit the designers as
little as possible but still to make it possible for the operators to
buy equipment from different suppliers. The GSM network is divided into
three major systems: the switching system (SS), the base station system
(BSS), and the operation and support system (OSS). The basic GSM
network elements are shown.
GSM Network Elements

3.1 The Switching System:
The switching system is responsible for performing call processing and
subscriber- related functions. The switching system includes the
following functional units.
¢ home location register (HLR)”The HLR is a database used for
storage and management of subscriptions. The HLR is considered the most
important database, as it stores permanent data about subscribers,
including a subscriber's service profile, location information, and
activity status. When an individual buys a subscription from one of the
PCS operators, he or she is registered in the HLR of that operator.
¢ mobile services switching center (MSC)”The MSC performs the
telephony switching functions of the system. It controls calls to and
from other telephone and data systems. It also performs such functions
as toll ticketing, network interfacing, common channel signaling, and
others.
¢ visitor location register (VLR)”The VLR is a database that
contains temporary information about subscribers that is needed by the
MSC in order to service visiting subscribers. The VLR is always
integrated with the MSC. When a mobile station roams into a new MSC
area, the VLR connected to that MSC will request data about the mobile
station from the HLR. Later, if the mobile station makes a call, the
VLR will have the information needed for call setup without having to
interrogate the HLR each time.
¢ authentication center (AUC)”A unit called the AUC provides
authentication and encryption parameters that verify the user's
identity and ensure the confidentiality of each call. The AUC protects
network operators from different types of fraud found in today's
cellular world.
¢ equipment identity register (EIR)”The EIR is a database that
contains information about the identity of mobile equipment that
prevents calls from stolen, unauthorized, or defective mobile stations.
The AUC and EIR are implemented as stand-alone nodes or as a combined
AUC/EIR node.
3.2 The Base Station System (BSS):
All radio-related functions are performed in the BSS, which consists of
base station controllers (BSCs) and the base transceiver stations
(BTSs).
¢ BSC”The BSC provides all the control functions and physical
links between the MSC and BTS. It is a high-capacity switch that
provides functions such as handover, cell configuration data, and
control of radio frequency (RF) power levels in base transceiver
stations. A number of BSCs are served by an MSC.
¢ BTS”The BTS handles the radio interface to the mobile station.
The BTS is the radio equipment (transceivers and antennas) needed to
service each cell in the network. A group of BTSs are controlled by a
BSC.
3.3 The Operation and Support System:
The operations and maintenance center (OMC) is connected to all
equipment in the switching system and to the BSC. The implementation of
OMC is called the operation and support system (OSS). The OSS is the
functional entity from which the network operator monitors and controls
the system. The purpose of OSS is to offer the customer cost-effective
support for centralized, regional, and local operational and
maintenance activities that are required for a GSM network. An
important function of OSS is to provide a network overview and support
the maintenance activities of different operation and maintenance
organizations.
4. GSM Subscriber Services:
There are two basic types of services offered through GSM: telephony
(also referred to as teleservices) and data (also referred to as bearer
services). Telephony services are mainly voice services that provide
subscribers with the complete capability (including necessary terminal
equipment) to communicate with other subscribers. Data services provide
the capacity necessary to transmit appropriate data signals between two
access points creating an interface to the network. In addition to
normal telephony and emergency calling, the following subscriber
services are supported by GSM,
¢ dual-tone multifrequency (DTMF)”DTMF is a tone signaling scheme
often used for various control purposes via the telephone network, such
as remote control of an answering machine. GSM supports full-
originating DTMF.
¢ facsimile group III”GSM supports CCITT Group 3 facsimile. As
standard fax machines are designed to be connected to a telephone using
analog signals, a special fax converter connected to the exchange is
used in the GSM system. This enables a GSM“connected fax to communicate
with any analog fax in the network.
¢ short message services”A convenient facility of the GSM network
is the short message service. A message consisting of a maximum of 160
alphanumeric characters can be sent to or from a mobile station. This
service can be viewed as an advanced form of alphanumeric paging with a
number of advantages. If the subscriber's mobile unit is powered off or
has left the coverage area, the message is stored and offered back to
the subscriber when the mobile is powered on or has reentered the
coverage area of the network. This function ensures that the message
will be received.
¢ cell broadcast”A variation of the short message service is the
cell broadcast facility. A message of a maximum of 93 characters can be
broadcast to all mobile subscribers in a certain geographic area.
Typical applications include traffic congestion warnings and reports on
accidents.
¢ voice mail”This service is actually an answering machine within
the network, which is controlled by the subscriber. Calls can be
forwarded to the subscriber's voice-mail box and the subscriber checks
for messages via a personal security code.
¢ fax mail”With this service, the subscriber can receive fax
messages at any fax machine. The messages are stored in a service
center from which they can be retrieved by the subscriber via a
personal security code to the desired fax number
5. GSM ADVANTAGES AS PERCEIVED BY PROPONENTS:
¢ Already deployed as a worldwide standard
o 35 million subscribers today
o 150 million subscribers in 1999 (est.), outnumbering CDMA 7 to
1
¢ National/International roaming
o PCS1900 architecture supports full network interoperability
¢ Total system specified in standard
o CDMA is just an air interface
¢ Voice quality comparable to wireline
o Enhanced full rate vocoder (13 Kbps)
¢ Subscriber Identity Module (SIM) card
o Increased flexibility and utility
o Allows worldwide roaming
o Stores personal phone numbers, missed calls, voice mail
notification, text messages
6. GSMâ„¢S economic impact:
It is estimated that global subscribers will exceed 1.5bn in 2004 and
reach 2.3bn by 2010. And expectations are that at least 85% of the
world's next-generation wireless customers utilise the GSM family of
technologies for both voice and data services. Mobile network operator
revenues alone totaled $426bn in 2003 (based on current exchange
rates), an increase of 19% versus 2002. Beliefs are that GSM accounted
for 65% of this total. Returns analysis suggests that the sector is
highly profitable. In addition, estimates are that mobile telephony has
created 4.1m jobs worldwide and within this GSM itself accounts for
75%. Following a couple of weaker years, beliefs are that job creation
will recommence and expect the industry to reach 10m employees by 2010.
7. GSMâ„¢s social impact:
Probably no single telecommunication system in recent history has had
as profound an impact on global society than the GSM mobile phone. Its
unprecedented growth in the world has paved the way for increased
mobile telephone usage and brought badly needed modern
telecommunications services to undeserved communities in thedeveloping
world.
8. GSMâ„¢s future key success factors (KSFs):
Over the next five years, several KSFs for the mobile industry will
influence the market as we transition to the new 3G environment. These
include:
¢ Enabling convergence with other wireless technologies
¢ Developing mobile centric applications
¢ Evolving the mobile business model
¢ Introducing mobile terminal enhancements and variety
¢ Fostering industry partnerships and co-operations
¢ Interoperability and intergenerational roaming between various
platforms
9. Conclusion:
We sought to identify how mobile telephony, and to a large extent GSM,
is fostering the emergence of a mobile paradigm; whereby the mobile
phone has become the first choice of personal phone. Its ready
acceptance as the de facto global standard
has been a key driver for socio-economic growth throughout the world.
As we rapidly
evolve towards a mobile wireless information society, that will bring
about
convergence of mobility and the Internet, GSM is continuing to play a
crucial role in
facilitating the smooth transition to the next-generation (3G) of
mobile
telecommunications services.
CONTENTS:
PAGE
1. INTRODUCTION: THE EVOLUTION OF MOBILE
TELEPHONE SYSTEMS. ¦
2
2. GSM
¦ 3
3. THE GSM NETWORK
SWITCHING SYSTEM ...
6
BASE STATION SYSTEMN ¦
8
OPERATION AND SUPPORT SYSTEM ¦ 8
4. GSM SUBSCRIBER SERVICES ¦
9
5. GSM ADVANTAGES AS PERCIEVED BY
PROPONENTS ¦
10
6. GSM™S ECONOMIC IMPACT ¦
11
7. GSM™S SOCIAL IMPACT ¦
11
8. GSM FUTURE SUCCESS FACTORS ¦ 12
9. CONCLUSION ¦
12

GLOBAL SYSTEM
FOR
MOBILE COMMUNICATION

---

Presented By,
M.K.Chaitanya,
BE ¾ (ECE),
M.V.S.R Engineering College,
Nadergul, Hyderabad.
Phone:040-24040165.
L.Srinivas,
BE ¾ (ECE),
M.V.S.R Engineering College,
Nadergul, Hyderabad.

---

Definition:
Global system for mobile communication (GSM) is a globally accepted standard for digital cellular communication. GSM is the name of a standardization group established in 1982 to create a common European mobile telephone standard that would formulate specifications for a pan-European mobile cellular radio system operating at 900 MHz. It is estimated that many countries outside of Europe will join the GSM partnership.
1. Introduction: The Evolution of Mobile Telephone Systems
Cellular is one of the fastest growing and most demanding telecommunications applications. Today, it represents a continuously increasing percentage of all new telephone subscriptions around the world. Currently there are more than 45 million cellular subscribers worldwide, and nearly 50 percent of those subscribers are located in the United States. It is forecasted that cellular systems using a digital technology will become the universal method of telecommunications. By the year 2005, forecasters predict that there will be more than 100 million cellular subscribers worldwide.
Cellular Subscriber Growth Worldwide
The concept of cellular service is the use of low-power transmitters where frequencies can be reused within a geographic area. The idea of cell-based mobile radio service was formulated in the United States at Bell Labs in the early 1970s. However, the Nordic countries were the first to introduce cellular services for commercial use with the introduction of the Nordic Mobile Telephone (NMT) in 1981. Cellular systems began in the United States with the release of the advanced mobile phone service (AMPS) system in 1983. The AMPS standard was adopted by Asia, Latin America, and Oceanic countries, creating the largest potential market in the world for cellular.
In the early 1980s, most mobile telephone systems were analog rather than digital, like today's newer systems. One challenge facing analog systems was the inability to handle the growing capacity needs in a cost-efficient manner. As a result, digital technology was welcomed. The advantages of digital systems over analog systems include ease of signaling, lower levels of interference, integration of transmission and switching, and increased ability to meet capacity demands.
2. GSM:
Throughout the evolution of cellular telecommunications, various systems have been developed without the benefit of standardized specifications. This presented many problems directly related to compatibility, especially with the development of digital radio technology. The GSM standard is intended to address these problems.
From 1982 to 1985 discussions were held to decide between building an analog or digital system. After multiple field tests, a digital system was adopted for GSM. The next task was to decide between a narrow or broadband solution. In May 1987, the narrowband time division multiple access (TDMA) solution was chosen. A summary of GSM milestones is given in Table
Table GSM Milestones
Year Milestone
1982 GSM formed
1986 field test
1987 TDMA chosen as access method
1988 memorandum of understanding signed
1989 validation of GSM system
1990 preoperation system
1991 commercial system start-up
1992 coverage of larger cities/airports
1993 coverage of main roads
1995 coverage of rural areas
Why has GSM been successful?
The success of GSM is that its development was founded on the delivery of a specific user benefit - international roaming. The demands of international roaming had profound changes on GSMâ„¢s architecture and mandated an open future-proof standard that ensured interoperability, without stifling competition, and innovation among suppliers. This lowered barriers to entry, promoted compatibility between systems which, in turn, lowered development costs and set the stage for better choice and innovation. The unparalleled economies of scale and competition that resulted brought convenience and falling prices to manufacturers, network operators and consumers.
The adoption of a digital system offered improved mobility, spectrum efficiency,
better quality transmission and new services over the first generation systems. The
use of Very Large Scale Integration (VLSI) microprocessor technology and other low
cost IC architectures paved the way for more efficient and affordable pocket-sized
mobile phones. This resulted in a profound change in usersâ„¢ mobile communication
style from vehicular-based to personal, opportunity-based communications.
Although GSM is only one of the pieces in the cluster of current and future
telecommunications networks, its ability to provide anytime, and almost anywhere,
communications has resulted in tremendous economic and social consequences.
Without GSM the pace of development of mobile telephony would have pared dramatically and that additional revenue streams, such as roaming (estimated globally at $1.78bn in 2003), would not have been as successful.
3. The GSM Network:
GSM provides recommendations, not requirements. The GSM specifications define the functions and interface requirements in detail but do not address the hardware. The reason for this is to limit the designers as little as possible but still to make it possible for the operators to buy equipment from different suppliers. The GSM network is divided into three major systems: the switching system (SS), the base station system (BSS), and the operation and support system (OSS). The basic GSM network elements are shown.
GSM Network Elements
3.1 The Switching System:
The switching system is responsible for performing call processing and subscriber- related functions. The switching system includes the following functional units.
¢ home location register (HLR)”The HLR is a database used for storage and management of subscriptions. The HLR is considered the most important database, as it stores permanent data about subscribers, including a subscriber's service profile, location information, and activity status. When an individual buys a subscription from one of the PCS operators, he or she is registered in the HLR of that operator.
¢ mobile services switching center (MSC)”The MSC performs the telephony switching functions of the system. It controls calls to and from other telephone and data systems. It also performs such functions as toll ticketing, network interfacing, common channel signaling, and others.
¢ visitor location register (VLR)”The VLR is a database that contains temporary information about subscribers that is needed by the MSC in order to service visiting subscribers. The VLR is always integrated with the MSC. When a mobile station roams into a new MSC area, the VLR connected to that MSC will request data about the mobile station from the HLR. Later, if the mobile station makes a call, the VLR will have the information needed for call setup without having to interrogate the HLR each time.
¢ authentication center (AUC)”A unit called the AUC provides authentication and encryption parameters that verify the user's identity and ensure the confidentiality of each call. The AUC protects network operators from different types of fraud found in today's cellular world.
¢ equipment identity register (EIR)”The EIR is a database that contains information about the identity of mobile equipment that prevents calls from stolen, unauthorized, or defective mobile stations. The AUC and EIR are implemented as stand-alone nodes or as a combined AUC/EIR node.
3.2 The Base Station System (BSS):
All radio-related functions are performed in the BSS, which consists of base station controllers (BSCs) and the base transceiver stations (BTSs).
¢ BSC”The BSC provides all the control functions and physical links between the MSC and BTS. It is a high-capacity switch that provides functions such as handover, cell configuration data, and control of radio frequency (RF) power levels in base transceiver stations. A number of BSCs are served by an MSC.
¢ BTS”The BTS handles the radio interface to the mobile station. The BTS is the radio equipment (transceivers and antennas) needed to service each cell in the network. A group of BTSs are controlled by a BSC.
3.3 The Operation and Support System:
The operations and maintenance center (OMC) is connected to all equipment in the switching system and to the BSC. The implementation of OMC is called the operation and support system (OSS). The OSS is the functional entity from which the network operator monitors and controls the system. The purpose of OSS is to offer the customer cost-effective support for centralized, regional, and local operational and maintenance activities that are required for a GSM network. An important function of OSS is to provide a network overview and support the maintenance activities of different operation and maintenance organizations.
4. GSM Subscriber Services:
There are two basic types of services offered through GSM: telephony (also referred to as teleservices) and data (also referred to as bearer services). Telephony services are mainly voice services that provide subscribers with the complete capability (including necessary terminal equipment) to communicate with other subscribers. Data services provide the capacity necessary to transmit appropriate data signals between two access points creating an interface to the network. In addition to normal telephony and emergency calling, the following subscriber services are supported by GSM,
¢ dual-tone multifrequency (DTMF)”DTMF is a tone signaling scheme often used for various control purposes via the telephone network, such as remote control of an answering machine. GSM supports full-originating DTMF.
¢ facsimile group III”GSM supports CCITT Group 3 facsimile. As standard fax machines are designed to be connected to a telephone using analog signals, a special fax converter connected to the exchange is used in the GSM system. This enables a GSM“connected fax to communicate with any analog fax in the network.
¢ short message services”A convenient facility of the GSM network is the short message service. A message consisting of a maximum of 160 alphanumeric characters can be sent to or from a mobile station. This service can be viewed as an advanced form of alphanumeric paging with a number of advantages. If the subscriber's mobile unit is powered off or has left the coverage area, the message is stored and offered back to the subscriber when the mobile is powered on or has reentered the coverage area of the network. This function ensures that the message will be received.
¢ cell broadcast”A variation of the short message service is the cell broadcast facility. A message of a maximum of 93 characters can be broadcast to all mobile subscribers in a certain geographic area. Typical applications include traffic congestion warnings and reports on accidents.
¢ voice mail”This service is actually an answering machine within the network, which is controlled by the subscriber. Calls can be forwarded to the subscriber's voice-mail box and the subscriber checks for messages via a personal security code.
¢ fax mail”With this service, the subscriber can receive fax messages at any fax machine. The messages are stored in a service center from which they can be retrieved by the subscriber via a personal security code to the desired fax number
5. GSM ADVANTAGES AS PERCEIVED BY PROPONENTS:
¢ Already deployed as a worldwide standard
o 35 million subscribers today
o 150 million subscribers in 1999 (est.), outnumbering CDMA 7 to 1
¢ National/International roaming
o PCS1900 architecture supports full network interoperability
¢ Total system specified in standard
o CDMA is just an air interface
¢ Voice quality comparable to wireline
o Enhanced full rate vocoder (13 Kbps)
¢ Subscriber Identity Module (SIM) card
o Increased flexibility and utility
o Allows worldwide roaming
o Stores personal phone numbers, missed calls, voice mail notification, text messages
6. GSMâ„¢S economic impact:
It is estimated that global subscribers will exceed 1.5bn in 2004 and reach 2.3bn by 2010. And expectations are that at least 85% of the world's next-generation wireless customers utilise the GSM family of technologies for both voice and data services. Mobile network operator revenues alone totaled $426bn in 2003 (based on current exchange rates), an increase of 19% versus 2002. Beliefs are that GSM accounted for 65% of this total. Returns analysis suggests that the sector is highly profitable. In addition, estimates are that mobile telephony has created 4.1m jobs worldwide and within this GSM itself accounts for 75%. Following a couple of weaker years, beliefs are that job creation will recommence and expect the industry to reach 10m employees by 2010.
7. GSMâ„¢s social impact:
Probably no single telecommunication system in recent history has had as profound an impact on global society than the GSM mobile phone. Its unprecedented growth in the world has paved the way for increased mobile telephone usage and brought badly needed modern telecommunications services to undeserved communities in thedeveloping world.
8. GSMâ„¢s future key success factors (KSFs):
Over the next five years, several KSFs for the mobile industry will influence the market as we transition to the new 3G environment. These include:
¢ Enabling convergence with other wireless technologies
¢ Developing mobile centric applications
¢ Evolving the mobile business model
¢ Introducing mobile terminal enhancements and variety
¢ Fostering industry partnerships and co-operations
¢ Interoperability and intergenerational roaming between various platforms
9. Conclusion:
We sought to identify how mobile telephony, and to a large extent GSM, is fostering the emergence of a mobile paradigm; whereby the mobile phone has become the first choice of personal phone. Its ready acceptance as the de facto global standard
has been a key driver for socio-economic growth throughout the world. As we rapidly
evolve towards a mobile wireless information society, that will bring about
convergence of mobility and the Internet, GSM is continuing to play a crucial role in
facilitating the smooth transition to the next-generation (3G) of mobile
telecommunications services.


CONTENTS: PAGE
1. INTRODUCTION: THE EVOLUTION OF MOBILE TELEPHONE SYSTEMS. ¦ 2
2. GSM ¦ 3
3. THE GSM NETWORK
SWITCHING SYSTEM ... 6
BASE STATION SYSTEMN ¦ 8
OPERATION AND SUPPORT SYSTEM ¦ 8
4. GSM SUBSCRIBER SERVICES ¦ 9
5. GSM ADVANTAGES AS PERCIEVED BY
PROPONENTS ¦ 10
6. GSM™S ECONOMIC IMPACT ¦ 11
7. GSM™S SOCIAL IMPACT ¦ 11
8. GSM FUTURE SUCCESS FACTORS ¦ 12
9.CONCLUSION ¦ 12

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1.Global System of Mobile Communication
The GSM standard (Global System for Mobile Communications) for mobile telephony was introduced in the mid-1980s and is the European initiative for creating a new cellular radio interface. The GSM system uses a TDMA radio access system employed in 135 countries, operating in 200 KHz channels with eight users per channel. It is the most widely deployed digital network in the world today, used by 10.5 million people in more than 200 countries.
1.1 GSM Bandwidth Allocation
GSM can operate four distinct frequency bands:
GSM 450: GSM 450 supports very large cells in the 450 MHz band. It was designed for countries with a low user density such as in Africa. It may also replace the original 1981NMT 450 (Nordic Mobile Telephone) analog networks used in the 450 MHz band. NMT is a first generation wireless technology.
GSM 900: When speaking of GSM, the original GSM system was called GSM 900 because the original frequency band was represented by 900 MHz. To provide additional capacity and to enable higher subscriber densities, two other systems were added afterward:
GSM 1800: GSM 1800 (or DCS 1800) is an adapted version of GSM 900 operating in the 1800MHz frequency range. Any GSM system operating in a higher frequency band requires a large number of base stations than for an original GSM system. The availability of a wider band of spectrum and a reduction in cell size will enable GSM 1800 to handle more subscribers thanGSM900. The smaller cells, in fact, give improved indoor coverage and low power requirements.
GSM 1900 (or PCS 1900): PCS 1900 (Personal Communications System) is a GSM 1800 variation designed for use on the North American Continent, which uses the 1900 MHz band. Since 1993, phase 2 of the specifications has included both the GSM 900 and DCS 1800(Digital Cellular System) in common documents. The GSM 1900 system has been added to the IS-136 D-AMPS (Digital Advanced Mobile Phone System) and IS-95 Code Division Multiple Access (CDMA) system, both operated at the 1900 MHz band.
The ITU (International Telecommunication Union) has allocated the GSM radio spectrum with the following bands:

GSM 900: Uplink: 890–915 MHz
Downlink: 935–960 MHz
GSM 1800: Uplink: 1710–1785 MHz
Downlink: 1805–1880 MHz
GSM 1900: Uplink: 1850–1910 MHz
Downlink: 1930–1990 MHz

In the above, uplink designates connection from the mobile station to the base station and down page link denotes connection from the base station to the mobile station.
2. THE GSM NETWORK

2.1 AN INTRODUCTION
Global System for Mobile communications (GSM) was born from the need by several European countries to introduce a common mobile communication network and overcome the limitations of the existing analogue system. The analogue system was limited in several ways, including its inability to cope with the unprecedented growth in the demand for mobile communications, the use of open channels allowing for easy ‘eavesdropping’ and ‘cloning’, the inflexibility in the introduction of value added services and the lack of a common network across Europe, among others.
2.2 GSM Network History
In 1982 the Conference Europenne des Postest T l communications (CEPT) formed the “Group Special Mobile” (GSM) (later to be called Global System for Mobile communications) to define the standards for a new mobile communications system. Although GSM was introduced as an European specific standard, it has been adopted by several countries world wide. The system was required to allow roaming in participating countries, offer services and facilities found in other public networks and use an internationally standardized signaling system for interconnection of mobile switching centers and location registers.
In the late 1980s it was realized, the specification and implementation of GSM could not be achieved in a single instance. A limited GSM roll-out (phase 1) was affected in 1991, offering basic voice telephony only. The specifications for phase 2, an ‘Enhancement’ to faze 1, include new supplementary services and the introduction of half rate speech channels. GSM as a standard has been in a constant state of evolution since its inception and will continue to do so into the foreseeable future.
GSM as a network is not defined by a set of rigid and stagnant standards. It is a network not only willing to evolve, but by the very nature of its specifications it needs to evolve. These qualities embodied within GSM make the results described in this thesis feasible and a practical reality.
“A platform [GSM] which is full of hooks, mechanisms and not at least potential to continue to build on. It provides mobile communications in all its possible forms and varieties. Even before Phase 2 standard has been completed, GSM has grown far beyond its original geographical “limitations” and the Global System for Mobile communication really starts to deserve its name. With Phase 2, and in particular Phase 2+, GSM will also expand far beyond its originally intended functional boundaries and open up for new applications, new access methods, new technologies and thus altogether for new categories of market, needs and users. It looks promising.” Jonas Twingler,GSM co- coordinator of ETSI.
GSM is one of the first ‘intelligent’ networks with distributed processing, clear separation between the switch and bearer control and to use Common Channel Signaling System. This provides GSM the hooks, mechanism and the potential to evolve and grow. This potential combined with the similarities between Intelligent Networks and GSM network architectures will be exploited will in this thesis to present an evolutionary path to a 3rd generation of mobile communication network.
Although GSM has been thoroughly covered in a brief overview of GSM is given in this chapter, with the aim of highlighting the clear separation between GSM’s radio access and core networks. The clear separation of core and access networks is vital to the evolution of any network to ensure that one is not restricted by the other hand changes to one does not necessarily result in the replacement of the complete network. The evolutionary path presented in this thesis relies on this separation.

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HISTORY
• Early 80’s Europe was experiencing rapid growth in the analog cellular telephone systems
• 1982 Conference of European Posts and Telegraphs (CEPT) GSM (Groupe Special Mobile) group was formed to study and develop a pan-European public land mobile system
• GSM mandate was to develop a standard to be common for the countries that created it – provide service to the entire European continent
GSM criteria –
– Good subjective speech quality
– Low terminal and service cost
– Support for international roaming – one system for all of Europe
– Ability to support handheld terminals
– Support for range of new services and facilities
– Enhanced Features
– ISDN compatibility
– Enhance privacy
– Security against fraud
• Late 1980’s GSM work was transferred to the European Telecommunication Standards Institute (ETSI) and SGM (Special Mobile Group) was created
• Document the functionality and interaction of every aspect of the GSM network
• 1987 ETSI oversees the creation of GSM MoU (Memorandum of Understanding) Association
• Formal objective of the GSM MoU Association is the promotion and evolution of the GSM systems and GSM platforms
• Concepts of a published international standard and a constantly evolving common standard are unique to GSM
• Work groups throughout the world specifically designed to allow interested parties to meet and work on finding solutions to systems enhancements that will fit into existing programs of GSM operators
• Phase I of GSM specifications was published in 1990
• International demand was so great that the system name was changed from Groupe Special Mobile to Global Systems for Mobile Communications (still GSM)
• Commercial service started in mid-1991
• 1992 first paying customers were signed up for service
• By 1993 there were 36 GSM networks in 22 countries
• Early 1994 there were 1.3 million subscribers worldwide
• By 1996 there were more than 25 million subscribers worldwide
• By October 1997 it had grown to more than 55 million subscribers worldwide
Building Blocks
• AMPS – Advanced Mobile Phone System
• TACS – Total Access Communication System
• NMT – Nordic Mobile Telephone System
AMPS – Advanced Mobile Phone System
• analog technology
• used in North and South America and approximately 35 other countries
• operates in the 800 MHz band using FDMA technology
TACS – Total Access Communication System
• variant of AMPS
• deployed in a number of countries
• primarily in the UK
NMT – Nordic Mobile Telephone System
• analog technology
• deployed in the Benelux countries and Russia
• operates in the 450 and 900 MHz band
• first technology to offer international roaming – only within the Nordic countries
• System Architecture
• Mobile Station (MS)
Mobile Equipment (ME)
Subscriber Identity Module (SIM)
• Base Station Subsystem (BBS)
Base Transceiver Station (BTS)
Base Station Controller (BSC)
• Network Subsystem
Mobile Switching Center (MSC)
Home Location Register (HLR)
Visitor Location Register (VLR)
Authentication Center (AUC)
Equipment Identity Register (EIR)
• System Architecture
Mobile Station (MS)
The Mobile Station is made up of two entities:
1. Mobile Equipment (ME)
2. Subscriber Identity Module (SIM)

• System Architecture
Mobile Station (MS) contd.
Mobile Equipment
• Produced by many different manufacturers
• Must obtain approval from the standardization body
• Uniquely identified by an IMEI (International Mobile Equipment Identity)
• System Architecture
Mobile Station (MS) contd.
Subscriber Identity Module (SIM)
• Smart card containing the International Mobile Subscriber Identity (IMSI)
• Allows user to send and receive calls and receive other subscribed services
• Encoded network identification details
• Protected by a password or PIN
• Can be moved from phone to phone – contains key information to activate the phone
• System Architecture
Base Station Subsystem (BSS)
Base Station Subsystem is composed of two parts that communicate across the standardized Abis interface allowing operation between components made by different suppliers
1. Base Transceiver Station (BTS)
2. Base Station Controller (BSC)
• System Architecture
Base Station Subsystem (BSS) contd.
Base Transceiver Station (BTS)
• Houses the radio transceivers that define a cell
• Handles radio-link protocols with the Mobile Station
• Speech and data transmissions from the MS are recoded
• Requirements for BTS:
ruggedness
reliability
portability
minimum costs
• System Architecture
Base Station Subsystem (BSS) contd.
Base Station Controller (BSC)
• Manages Resources for BTS
• Handles call set up
• Location update
• Handover for each MS
System Architecture Network Subsystem
Mobile Switching Center (MSC)
• Switch speech and data connections between:
Base Station Controllers
Mobile Switching Centers
GSM-networks
Other external networks
• Heart of the network
• Three main jobs:
1) connects calls from sender to receiver
2) collects details of the calls made and received
3) supervises operation of the rest of the network components
Home Location Registers (HLR)
- contains administrative information of each subscriber
- current location of the mobile
• Visitor Location Registers (VLR)
- contains selected administrative information from the HLR
- authenticates the user
- tracks which customers have the phone on and ready to receive a call
- periodically updates the database on which phones are turned on and ready to receive calls
- System Architecture
• Authentication Center (AUC)
- mainly used for security
- data storage location and functional part of the network
- Ki is the primary element
• Equipment Identity Register (EIR)
- Database that is used to track handsets using the IMEI (International Mobile Equipment Identity)
- Made up of three sub-classes: The White List, The Black List and the Gray List
- Optional database
- System Architecture
Basic Features Provided by GSM
• Call Waiting
- Notification of an incoming call while on the handset
• Call Hold
- Put a caller on hold to take another call
• Call Barring
- All calls, outgoing calls, or incoming calls
• Call Forwarding
- Calls can be sent to various numbers defined by the user
• Multi Party Call Conferencing
- Link multiple calls together
Advanced Features Provided by GSM
• Calling Line ID
- incoming telephone number displayed
• Alternate Line Service
- one for personal calls
- one for business calls
• Closed User Group
- call by dialing last for numbers
• Advice of Charge
- tally of actual costs of phone calls
• Fax & Data
- Virtual Office / Professional Office
• Roaming
- services and features can follow customer from market to market
Future -- UMTS (Universal Mobile Telephone System
• Reasons for innovations
- new service requirements
- availability of new radio bands
• User demands
- seamless Internet-Intranet access
- wide range of available services
- compact, lightweight and affordable terminals
- simple terminal operation
- open, understandable pricing structures for the whole spectrum of available services
Advantages of GSM
• Crisper, cleaner quieter calls
• Security against fraud and eavesdropping
• International roaming capability in over 100 countries
• Improved battery life
• Efficient network design for less expensive system expansion
• Efficient use of spectrum
• Advanced features such as short messaging and caller ID
• A wide variety of handsets and accessories
• High stability mobile fax and data at up to 9600 baud
• Ease of use with over the air activation, and all account information is held in a smart card which can be moved from handset to handset

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INTRODUCTION
The Global System for Mobile communications is a digital cellular communications system. It was developed in order to create a common European mobile telephone standard but it has been rapidly accepted worldwide. GSM was designed to be compatible with ISDN services.
HISTORY OF GSM :---
The idea of cell-based mobile radio systems appeared at Bell Laboratories (in USA) in the early 1970s. However, mobile cellular systems were not introduced for commercial use until the 1980s. During the early 1980s, analog cellular telephone systems experienced a very rapid growth in Europe, particularly in Scandinavia and the United Kingdom. Today cellular systems still represent one of the fastest growing telecommunications systems.
But in the beginnings of cellular systems, each country developed its own system, which was an undesirable situation for the following reasons:
• The equipment was limited to operate only within the boundaries of each country.
• The market for each mobile equipment was limited.
In order to overcome these problems, the Conference of European Posts and Telecommunications (CEPT) formed, in 1982, the Groupe Spécial Mobile (GSM) in order to develop a pan-European mobile cellular radio system (the GSM acronym became later the acronym for Global System for Mobile communications). The standardized system had to meet certain criteria:
• Spectrum efficiency
• International roaming
• Low mobile and base stations costs
• Good subjective voice quality
• Compatibility with other systems such as ISDN , PSTN , PSPDN etc.
• Ability to support new services
GSM system is based on digital technology which has many advantages over analog technology. It also provides the technology as ROAMING, SMS
TELETEX , Fax mail.
TRANSITION FROM ANALOG TO DIGITAL
In the 1980s most mobile cellular systems were based on analog systems as AMPS. Second generation cellular digital systems like GSM , DAMPS, were implemented then. From 1984-86, GSM focused on to compare different technical possibilities for transmission. It was decided to compare several technical proposals on the basis of prototypes allowing actual radio transmission.
The capacity of the system
Cellular systems have experienced a very important growth. Analog systems were not able to cope with this increasing demand. In order to overcome this problem, new frequency bands and new technologies were proposed. But the possibility of using new frequency bands was rejected by a big number of countries because of the restricted spectrum. The new analog technologies proposed were able to overcome the problem to a certain degree but the costs were too important.
The digital radio was, therefore, the best option to handle the capacity needs in a cost-efficiency way.
Compatibility with other systems such as ISDN
The decision of adopting a digital technology for GSM was made in the course of developing the standard. During the development of GSM, the telecommunications industry converted to digital methods. The ISDN network is an example of this evolution. In order to make GSM compatible with the services offered by ISDN, it was decide that the digital technology was the best option.
Additionally, a digital system allows, easily than an analog one, the implementation of future improvements and the change of its own characteristics.
Aspects of quality
The quality of the service can be considerably improved using a digital technology rather than an analog one. In fact, analog systems pass the physical disturbances in radio transmission (such as fades, multipath reception, spurious signals or interferences) to the receiver. These disturbances decrease the quality of the communication because they produce effects such as fadeouts, crosstalks, hisses, etc. On the other hand, digital systems avoid these effects transforming the signal into bits. This transformation combined with other techniques, such as digital coding, improves the quality of the transmission. The improvement of digital systems comparing to analog systems is more noticeable under difficult reception conditions than under good reception conditions.
Cellular systems
The cellular structure
In a cellular system, the covering area of an operator is divided into cells. A cell corresponds to the covering area of one transmitter or a small collection of transmitters. The size of a cell is determined by the transmitter's power. The concept of cellular systems is the use of low power transmitters in order to enable the efficient reuse of the frequencies. In fact, if the transmitters used are very powerful, the frequencies cannot be reused for hundred of kilometers as they are limited to the covering area of the transmitter.
The frequency band allocated to a cellular mobile radio system is distributed over a group of cells and this distribution is repeated in all the covering area of an operator. The whole number of radio channels available can then be used in each group of cells that form the covering area of an operator. Frequencies used in a cell will be reused several cells away. The distance between the cells using the same frequency must be sufficient to avoid interference. The frequency reuse will increase considerably the capacity in number of users.
In order to work properly, a cellular system must verify the following two main conditions:
• The power level of a transmitter within a single cell must be limited in order to reduce the interference with the transmitters of neighboring cells. The receiver filters must also be very performant.
• Neighboring cells cannot share the same channels. In order to reduce the interference, the frequencies must be reused only within a certain pattern.
Cluster
The cells are grouped into clusters. The number of cells in a cluster must be determined so that the cluster can be repeated continuously within the covering area of an operator. The typical clusters contain 4, 7, 12 or 21 cells. The number of cells in each cluster is very important. The smaller the number of cells per cluster is, the bigger the number of channels per cell will be. The capacity of each cell will be therefore increased. However a balance must be found in order to avoid the interference that could occur between neighboring clusters. This interference is produced by the small size of the clusters. The total number of channels per cell depends on the number of available channels and the type of cluster used.
Types of cells: The density of population in a country is so varied that different types of cells are used: 3 Macrocells
The macrocells are large cells for remote and sparsely populated areas.
Microcells
These cells are used for densely populated areas. By splitting the existing areas into smaller cells, the number of channels available is increased as well as the capacity of the cells. The power level of the transmitters used in these cells is then decreased, reducing the possibility of interference between neighboring cells.
Selective cells
It is not always useful to define a cell with a full coverage of 360 degrees. In some cases, cells with a particular shape and coverage are needed. These cells are called selective cells. A typical example of selective cells is the cells that may be located at the entrances of tunnels where coverage of 360 degrees is not needed. In this case, a selective cell with a coverage of 120 degrees is used.
Umbrella cells
A freeway crossing very small cells produces an important number of handovers among the different small neighboring cells. In order to solve this problem, the concept of umbrella cells is introduced. An umbrella cell covers several microcells. The power level inside an umbrella cell is increased comparing to the power levels used in the microcells that form the umbrella cell. When the speed of the mobile is too high, the mobile is handed off to the umbrella cell. The mobile will then stay longer in the same cell (in this case the umbrella cell). This will reduce the number of handovers and the work of the network.