22-12-2010, 02:41 PM
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 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.
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 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.