Gsm: Network Architecture
GSM: Network Architecture
The GSM technical specifications define the different entities that form the GSM network by defining their functions and interface requirements.
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).
figure 1: Architecture of the GSM network
Mobile Station
A Mobile Station consists of two main elements: * The Subscriber Identity Module (SIM): It is protected by a four-digit Personal Identification Number (PIN). In order to identify the subscriber to the system, the SIM card contains amongst others a unique International Mobile Subscriber Identity (IMSI). User mobility is provided through mapping the subscriber to the SIM card rather than the terminal as we done in past cellular systems. * Mobile equipment/terminal (ME): There are different types of terminals (MN) distinguished principally by their power and application: * `Fixed' terminals mainly installed in cars. Their maximum allowed output power is 20W * Portable terminals can also be installed in vehicles. Their maximum allowed output power is 8W. * Handheld terminals; their popularity is owed to their weight and volume, which is continuously decreasing. According to some specification these terminals may emit up to 0.8W. However, as technology has evolved their maximum allowed power output is limited to 0.1W.
Base Station Subsystem
The BSS provides the interface between the ME and the NSS. It is in charge of the transmission and reception. It may be divided into two parts: * Base Station Controller (BSC): It controls a group of BTSs and manages their radio ressources. A BSC is principally in charge of handoffs, frequency hopping, exchange functions and power control over each managed BTSs. * Base Transceiver Station (BTS) or Base Station: it maps to transceivers and
The GSM technical specifications define the different entities that form the GSM network by defining their functions and interface requirements.
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).
figure 1: Architecture of the GSM network
Mobile Station
A Mobile Station consists of two main elements: * The Subscriber Identity Module (SIM): It is protected by a four-digit Personal Identification Number (PIN). In order to identify the subscriber to the system, the SIM card contains amongst others a unique International Mobile Subscriber Identity (IMSI). User mobility is provided through mapping the subscriber to the SIM card rather than the terminal as we done in past cellular systems. * Mobile equipment/terminal (ME): There are different types of terminals (MN) distinguished principally by their power and application: * `Fixed' terminals mainly installed in cars. Their maximum allowed output power is 20W * Portable terminals can also be installed in vehicles. Their maximum allowed output power is 8W. * Handheld terminals; their popularity is owed to their weight and volume, which is continuously decreasing. According to some specification these terminals may emit up to 0.8W. However, as technology has evolved their maximum allowed power output is limited to 0.1W.
Base Station Subsystem
The BSS provides the interface between the ME and the NSS. It is in charge of the transmission and reception. It may be divided into two parts: * Base Station Controller (BSC): It controls a group of BTSs and manages their radio ressources. A BSC is principally in charge of handoffs, frequency hopping, exchange functions and power control over each managed BTSs. * Base Transceiver Station (BTS) or Base Station: it maps to transceivers and