Architecture of the GSM network:
The GSM network can be divided into four main parts:
The Mobile Station (MS).
The Base Station Subsystem (BSS).
The Network and Switching Subsystem (NSS).
The Operation and Support Subsystem (OSS).
Mobile Station:
A Mobile Station consists of two main elements:
The mobile equipment or terminal.
The Subscriber Identity Module (SIM).
The Terminal:
There are different types of terminals distinguished principally by their power and application:
The `fixed' terminals are the ones installed in cars. Their maximum allowed output power is 20 W.
The GSM portable terminals can also be installed in vehicles. Their maximum allowed output power is 8W.
The handhels terminals have experienced the biggest success thanks to thei weight and volume, which are continuously decreasing. These terminals can emit 0.8W to 2 W.
The Subscriber Identity Module SIM:
The SIM is a smart card that identifies the terminal. By inserting the SIM card into the terminal, the user can have access to all the subscribed services. The SIM card is protected by a four-digit Personal Identification Number (PIN).
↱ Another advantage of the SIM card is the mobility of the users. In fact, the only element that personalizes a terminal is the SIM card. Therefore, the user can have access to its subscribed services in any terminal using its SIM card.
The SIM is a smart card that identifies the terminal. By inserting the SIM card into the terminal, the user can have access to all the subscribed services. The SIM card is protected by a four-digit Personal Identification Number (PIN).
↱ Another advantage of the SIM card is the mobility of the users. In fact, the only element that personalizes a terminal is the SIM card. Therefore, the user can have access to its subscribed services in any terminal using its SIM card.
The Base Station Subsystem (BSS):
↱The BSS connects the Mobile Station and the NSS. It is in charge of the transmission and reception.
The BSS can be divided into two parts:
The Base Transceiver Station (BTS) or Base Station.
The Base Station Controller (BSC).
The Network and Switching Subsystem (NSS):
Its main role is to manage the communications between the mobile users and other users, such as mobile users, ISDN users, fixed telephony users, etc.
It also includes data bases needed in order to store information about the subscribers and to manage their mobility.
The different components of the NSS are described below.
Gateway Mobile service switching center (GMSC):
The gateway is a node interconnecting two or more networks. Basically GMSC is the interface between a mobile cellular network and other networks such as PSTN,PSDN,or networks of other mobile service provider.
Visitor location register (VLR):
The VLR is a data base containing information about all the mobile subscribers currently located in an MSC service area. There is a only one VLR for each MSC.
Home Location Register (HLR):
The HLR is a centralized network database that stores and manages all mobile subscriptions belonging to a specific service operator. This database stores the following information:
Subscriber identity
Subscriber supplementary services
Subscriber location information
Subscriber authentication information
Equipment Identity Register (EIR):
EIR is used for security purposes.It is a register containing information about the valid terminals. Generally a terminal is identified by its International Mobile Equipment Identity (IMEI). The EIR allows to cancel call from stolen or unauthorized terminals.
Authentication Center (AUC):
The function of the AUC register is to authenticate the subscribers attempting to use a network. It is connected to HLR and provides HLR with the authentication parameters.
Mobile switching center (MSC):
It is a switching center which coordinates the routing of calls in a large service area under a cellular network. MSC controls the switching within the BSCs. It is also known as mobile telephone switching office(MTSO.)
The GSM Interworking Unit (GIWU):
It is a switching center which coordinates the routing of calls in a large service area under a cellular network. MSC controls the switching within the BSCs. It is also known as mobile telephone switching office(MTSO.)
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.
The GSM network can be divided into four main parts:
The Mobile Station (MS).
The Base Station Subsystem (BSS).
The Network and Switching Subsystem (NSS).
The Operation and Support Subsystem (OSS).
Mobile Station:
A Mobile Station consists of two main elements:
The mobile equipment or terminal.
The Subscriber Identity Module (SIM).
The Terminal:
There are different types of terminals distinguished principally by their power and application:
The `fixed' terminals are the ones installed in cars. Their maximum allowed output power is 20 W.
The GSM portable terminals can also be installed in vehicles. Their maximum allowed output power is 8W.
The handhels terminals have experienced the biggest success thanks to thei weight and volume, which are continuously decreasing. These terminals can emit 0.8W to 2 W.
The Subscriber Identity Module SIM:
The SIM is a smart card that identifies the terminal. By inserting the SIM card into the terminal, the user can have access to all the subscribed services. The SIM card is protected by a four-digit Personal Identification Number (PIN).
↱ Another advantage of the SIM card is the mobility of the users. In fact, the only element that personalizes a terminal is the SIM card. Therefore, the user can have access to its subscribed services in any terminal using its SIM card.
The SIM is a smart card that identifies the terminal. By inserting the SIM card into the terminal, the user can have access to all the subscribed services. The SIM card is protected by a four-digit Personal Identification Number (PIN).
↱ Another advantage of the SIM card is the mobility of the users. In fact, the only element that personalizes a terminal is the SIM card. Therefore, the user can have access to its subscribed services in any terminal using its SIM card.
The Base Station Subsystem (BSS):
↱The BSS connects the Mobile Station and the NSS. It is in charge of the transmission and reception.
The BSS can be divided into two parts:
The Base Transceiver Station (BTS) or Base Station.
The Base Station Controller (BSC).
The Network and Switching Subsystem (NSS):
Its main role is to manage the communications between the mobile users and other users, such as mobile users, ISDN users, fixed telephony users, etc.
It also includes data bases needed in order to store information about the subscribers and to manage their mobility.
The different components of the NSS are described below.
Gateway Mobile service switching center (GMSC):
The gateway is a node interconnecting two or more networks. Basically GMSC is the interface between a mobile cellular network and other networks such as PSTN,PSDN,or networks of other mobile service provider.
Visitor location register (VLR):
The VLR is a data base containing information about all the mobile subscribers currently located in an MSC service area. There is a only one VLR for each MSC.
Home Location Register (HLR):
The HLR is a centralized network database that stores and manages all mobile subscriptions belonging to a specific service operator. This database stores the following information:
Subscriber identity
Subscriber supplementary services
Subscriber location information
Subscriber authentication information
Equipment Identity Register (EIR):
EIR is used for security purposes.It is a register containing information about the valid terminals. Generally a terminal is identified by its International Mobile Equipment Identity (IMEI). The EIR allows to cancel call from stolen or unauthorized terminals.
Authentication Center (AUC):
The function of the AUC register is to authenticate the subscribers attempting to use a network. It is connected to HLR and provides HLR with the authentication parameters.
Mobile switching center (MSC):
It is a switching center which coordinates the routing of calls in a large service area under a cellular network. MSC controls the switching within the BSCs. It is also known as mobile telephone switching office(MTSO.)
The GSM Interworking Unit (GIWU):
It is a switching center which coordinates the routing of calls in a large service area under a cellular network. MSC controls the switching within the BSCs. It is also known as mobile telephone switching office(MTSO.)
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.
