Lecture_2-GSM Towards LTE_CTTC_20120317.ppt

Editor's Notes

• #9: MSC:The MSC performs the telephony switching functions for the mobile network. It controls calls to and from other telephony and data systems, such as the Public Switched Telephone Network (PSTN), Integrated Services Digital Network (ISDN), public data networks, private networks and other mobile networks. GMSC:Gateway functionality enables an MSC to interrogate a network’s HLR in order to route a call to a Mobile Station (MS). Such an MSC is called a Gateway MSC (GMSC). For example,if a person connected to the PSTN wants to make a call to a GSM mobile subscriber, then the PSTN exchange will access the GSM network by first connecting the call to a GMSC. The same is true of a call from an MS to another MS. 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 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. The VLR can be regarded as a distributed HLR as it holds a copy of the HLR information stored about the subscriber. AUC:The main function of the AUC is to authenticate the subscribers attempting to use a network. In this way, it is used to protect network operators against fraud. The AUC is a database connected to the HLR which provides it with the authentication parameters and ciphering keys used to ensure network security. EIR:The EIR is a database containing mobile equipment identity information which helps to block calls from stolen,unauthorized, or defective MSs. BSC:The BSC manages all the radio-related functions of a GSM network. It is a high capacity switch that provides functions such as MS handover, radio channel assignment and the collection of cell configuration data. A number of BSCs may be controlled by each MSC. BTS:The BTS controls the radio interface to the MS. The BTS comprises the radio equipment such as transceivers and antennas which are needed to serve each cell in the network. A group of BTSs are controlled by a BSC. OMC:An OMC is a computerized monitoring center which is connected to other network components such as MSCs and BSCs via X.25 data network links. In the OMC, staff are presented with information about the status of the network and can monitor and control a variety of system parameters. There may be one or several OMCs within a network depending on the network size. NMC:Centralized control of a network is done at a Network Management Center (NMC).