HLR (Home Location Register) basic concept

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November 23, 2012 by Isybel Harto

Position of HLR in GSM/UMTS System
Main Function of HLR/AuC
•Home location register(HLR)
–Maintenance of Database for Mobile Subscriber
–The information in DB consists of some services parameter, location information of subscribers
•Authentication Center (AuC)
–Generates and stores authentication information for Mobile Subscriber
MAP Protocol Stack
Location Management Service Flow: Location Update
Call Processing Service Flow: Get Routing Information
Call Processing Service Flow: Query Anytime
Short Message Service Flow: Mobile-ended Short Message
Supplementary Service Operation Flow -1
Supplementary Service Operation Flow -2
Insert Sub Data
•Updating  location and modifying sub data through SMU server will cause the procedure of insert sub data.
–In location update, when HLR find that the location information of the user changes, HLR will insert new location information of the user.
–When the user data is modified at BOSS or SMU Client through SMU Server, it will cause insert new sub data.
–Authentication is the process to check if the subscriber’s IMSI is valid.
–In the GSM and the UMTS, authentication is complete under the cooperation of the MS, the VLR/SGSN, and the HLR/AuC. The MS and the AuC respectively calculate the authentication parameter. Then the VLR/SGSN compares the two parameters to check if the MS is valid.
–In the UMTS, the MS can check if the UMTS network is valid.
•Authentication types
–GSM: Using triplet: RAND, SRES, Kc
–UMTS: Using quintet: RAND, XRES, AUTN (for UE authenticate network) , CK, IK (for data integrity function)
–The Purge function allows an SGSN to inform the HLR that it has deleted the MM and PDP contexts of a detached MS
•After the MS detach from the network:
–The SGSN may delete the MM/PDP context immediately
– the SGSN may keep the MM/PDP context for some time of the detached MS
•Purge Timer Function
–Allows the SGSN to inform the HLR that it has deleted the MM and PDP contexts of a detached MS.
–The purge timer is set longer than the mobile reachable timer

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