Home location register (HLR)
[edit] Description
The home location register (HLR) is a central database that contains details of each mobile phone subscriber that is authorized to use the GSM core network. There can be several logical, and physical, HLRs per public land mobile network (PLMN), though one international mobile subscriber identity (IMSI)/MSISDN pair can be associated with only one logical HLR (which can span several physical nodes) at a time.
The HLR stores details of every SIM card issued by the mobile phone operator. Each SIM has a unique identifier called an IMSI which is the primary key to each HLR record.
The next important items of data associated with the SIM are the MSISDNs, which are the telephone numbers used by mobile phones to make and receive calls. The primary MSISDN is the number used for making and receiving voice calls and SMS, but it is possible for a SIM to have other secondary MSISDNs associated with it for fax and data calls. Each MSISDN is also a primary key to the HLR record. The HLR data is stored for as long as a subscriber remains with the mobile phone operator.
Examples of other data stored in the HLR against an IMSI record is:
GSM services that the subscriber has requested or been given.
GPRS settings to allow the subscriber to access packet services.
Current location of subscriber (VLR and serving GPRS support node/SGSN).
Call divert settings applicable for each associated MSISDN.
The HLR is a system which directly receives and processes MAP transactions and messages from elements in the GSM network, for example, the location update messages received as mobile phones roam around.
[edit] Other GSM core network elements connected to the HLR
The HLR connects to the following elements:
The G-MSC for handling incoming calls
The VLR for handling requests from mobile phones to attach to the network
The SMSC for handling incoming SMS
The voice mail system for delivering notifications to the mobile phone that a message is waiting
The AUC for authentication and ciphering and exchange of data (triplets)
[edit] Procedures implemented
The main function of the HLR is to manage the fact that SIMs and phones move around a lot. The following procedures are implemented to deal with this:
Manage the mobility of subscribers by means of updating their position in administrative areas called 'location areas', which are identified with a LAC. The action of a user of moving from one LA to another is followed by the HLR with a Location area update while retrieving information from BSS as base station identity code (BSIC).
Send the subscriber data to a VLR or SGSN when a subscriber first roams there.
Broker between the G-MSC or SMSC and the subscriber's current VLR in order to allow incoming calls or text messages to be delivered.
Remove subscriber data from the previous VLR when a subscriber has roamed away from it.
[edit] Description
The home location register (HLR) is a central database that contains details of each mobile phone subscriber that is authorized to use the GSM core network. There can be several logical, and physical, HLRs per public land mobile network (PLMN), though one international mobile subscriber identity (IMSI)/MSISDN pair can be associated with only one logical HLR (which can span several physical nodes) at a time.
The HLR stores details of every SIM card issued by the mobile phone operator. Each SIM has a unique identifier called an IMSI which is the primary key to each HLR record.
The next important items of data associated with the SIM are the MSISDNs, which are the telephone numbers used by mobile phones to make and receive calls. The primary MSISDN is the number used for making and receiving voice calls and SMS, but it is possible for a SIM to have other secondary MSISDNs associated with it for fax and data calls. Each MSISDN is also a primary key to the HLR record. The HLR data is stored for as long as a subscriber remains with the mobile phone operator.
Examples of other data stored in the HLR against an IMSI record is:
GSM services that the subscriber has requested or been given.
GPRS settings to allow the subscriber to access packet services.
Current location of subscriber (VLR and serving GPRS support node/SGSN).
Call divert settings applicable for each associated MSISDN.
The HLR is a system which directly receives and processes MAP transactions and messages from elements in the GSM network, for example, the location update messages received as mobile phones roam around.
[edit] Other GSM core network elements connected to the HLR
The HLR connects to the following elements:
The G-MSC for handling incoming calls
The VLR for handling requests from mobile phones to attach to the network
The SMSC for handling incoming SMS
The voice mail system for delivering notifications to the mobile phone that a message is waiting
The AUC for authentication and ciphering and exchange of data (triplets)
[edit] Procedures implemented
The main function of the HLR is to manage the fact that SIMs and phones move around a lot. The following procedures are implemented to deal with this:
Manage the mobility of subscribers by means of updating their position in administrative areas called 'location areas', which are identified with a LAC. The action of a user of moving from one LA to another is followed by the HLR with a Location area update while retrieving information from BSS as base station identity code (BSIC).
Send the subscriber data to a VLR or SGSN when a subscriber first roams there.
Broker between the G-MSC or SMSC and the subscriber's current VLR in order to allow incoming calls or text messages to be delivered.
Remove subscriber data from the previous VLR when a subscriber has roamed away from it.
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