03-12-2012, 06:14 PM
GSM TECHNOLOGY
[attachment=42342]
INTRODUCTION TO GSM NETWORK
THE SWITCHING SYSTEM
The switching system (SS) 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 centralized network database that stores and manages all mobile subscriptions belonging to a specific operator. It acts as a permanent store for a person’s subscription information until that subscription is canceled. The information stored includes:
• Subscriber identity
• Subscriber supplementary services
• Subscriber location information
• Subscriber authentication information
The HLR can be implemented in the same network node as the MSC or as a stand-alone database. If the capacity of a HLR is exceeded by the number of subscribers, additional HLRs may be added.
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 database contains information about all the mobile subscribers currently located in an MSC service area. Thus, there is one VLR for each MSC in a network. The VLR temporarily stores subscription information so that the MSC can service all the subscribers currently visiting that MSC service area. When a subscriber roams into a new MSC service area, the VLR connected to that MSC requests information about the subscriber from the subscriber’s HLR. The HLR sends a copy of the information to the VLR and updates its own location information. When the subscriber makes a call, the VLR will already have the information required for call set-up.
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. The AUC is a database connected to the HLR which provides it with the authentication parameters and ciphering keys used to ensure network security.
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
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) & transcoder controller.
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.
TRC -The purpose of a TRC is to multiplex network traffic channels from multiple BSCs onto one 64 Kbits/s PCM channel which reduces network transmission costs. The TRC can be combined with the BSC or exist as a stand-alone node.
MOBILE STATION
A Mobile Station (MS) is used by a mobile subscriber to communicate with the cellular system. Several types of mobile stations exist, each allowing the subscriber to make and receive calls. Manufacturers of mobile stations offer a variety of designs and features to meet the needs of different markets. The range or coverage area of a mobile station depends on, for example, the output power of the mobile station. Different types of mobile stations have different output power capabilities and therefore, different ranges. For example, hand-held telephones have a lower output power, (resulting in a shorter range), than a car installed phone with roof mounted antenna.
[attachment=42342]
INTRODUCTION TO GSM NETWORK
THE SWITCHING SYSTEM
The switching system (SS) 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 centralized network database that stores and manages all mobile subscriptions belonging to a specific operator. It acts as a permanent store for a person’s subscription information until that subscription is canceled. The information stored includes:
• Subscriber identity
• Subscriber supplementary services
• Subscriber location information
• Subscriber authentication information
The HLR can be implemented in the same network node as the MSC or as a stand-alone database. If the capacity of a HLR is exceeded by the number of subscribers, additional HLRs may be added.
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 database contains information about all the mobile subscribers currently located in an MSC service area. Thus, there is one VLR for each MSC in a network. The VLR temporarily stores subscription information so that the MSC can service all the subscribers currently visiting that MSC service area. When a subscriber roams into a new MSC service area, the VLR connected to that MSC requests information about the subscriber from the subscriber’s HLR. The HLR sends a copy of the information to the VLR and updates its own location information. When the subscriber makes a call, the VLR will already have the information required for call set-up.
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. The AUC is a database connected to the HLR which provides it with the authentication parameters and ciphering keys used to ensure network security.
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
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) & transcoder controller.
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.
TRC -The purpose of a TRC is to multiplex network traffic channels from multiple BSCs onto one 64 Kbits/s PCM channel which reduces network transmission costs. The TRC can be combined with the BSC or exist as a stand-alone node.
MOBILE STATION
A Mobile Station (MS) is used by a mobile subscriber to communicate with the cellular system. Several types of mobile stations exist, each allowing the subscriber to make and receive calls. Manufacturers of mobile stations offer a variety of designs and features to meet the needs of different markets. The range or coverage area of a mobile station depends on, for example, the output power of the mobile station. Different types of mobile stations have different output power capabilities and therefore, different ranges. For example, hand-held telephones have a lower output power, (resulting in a shorter range), than a car installed phone with roof mounted antenna.