Content for  TS 23.012  Word version:  18.0.0

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1  Scopep. 6

The present document describes the location management procedures for the circuit switched domain, with respect to the application level functional behaviour. This is to be distinguished from the corresponding protocol handling behaviour, which is specified in TS 29.002. The following location management procedures are included:
  • location updating;
  • location cancellation;
  • MS purging;
  • IMSI attach/detach.
The procedures in the Mobile Station (MS) are described in 3GPP TS 23.022 [6]. The procedures between MSC, VLR and HLR utilise the Mobile Application Part (MAP) and details concerning the protocol handling are contained in TS 29.002.
The present document excludes location management procedures for the packet switched domain, which are covered in TS 23.060.
The descriptions herein depict a logical separation between the MSC and VLR. This logical separation, as well as the messages transferred between the two logical entities are the basis of a model used to define the externally visible behaviour of the MSC/VLR, which a may be a single physical entity. They do not impose any requirement except the definition of the externally visible behaviour.

1.1  Referencesp. 6

The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
  • References are either specific (identified by date of publication, edition number, version number, etc.) or non specific.
  • For a specific reference, subsequent revisions do not apply.
  • For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.
TR 21.905: "3G Vocabulary".
TS 23.002: "Network architecture".
TS 23.003: "Numbering, addressing and identification".
TS 23.007: "Restoration procedures".
TS 23.008: "Organization of subscriber data".
TS 23.018: "Basic call handling; Technical realization".
TS 23.022: "Functions related to Mobile Station (MS) in idle mode".
→ to date, withdrawn by 3GPP
TS 23.116: "Super-Charger Technical Realisation; Stage 2".
TS 29.002: "Mobile Application Part (MAP) specification".
TS 29.007: "General requirements on interworking between the Public Land Mobile Network (PLMN) and the Integrated Services Digital Network (ISDN) or Public Switched Telephone Network (PSTN)".
TS 43.020: "Security related network functions".
TS 23.078: " Customised Applications for Mobile network Enhanced Logic (CAMEL) Phase 4 - stage2".
TS 23.195: "Provision of UE Specific Behaviour Information to Network Entities".
TS 23.236: "Intra Domain Connection of RAN Nodes to Multiple CN Nodes".
TS 24.008: "Mobile Radio Interface Layer 3 specification; Core Network Protocols - Stage 3".
TS 29.010: "Information element mapping between Mobile Station - Base Station System and BSS Mobile-services Switching Centre (MS - BSS - MSC) Signalling procedures and the Mobile Application Part (MAP)".
TS 32.422: "Subscriber and equipment trace: Trace control and configuration management".
TS 32.421: "Subscriber and equipment trace: Trace concepts and requirements".
TS 25.413: "UTRAN Iu interface RANAP signalling".
TR 29.994: "Recommended infrastructure measures to overcome specific Mobile Station (MS) faults".
TS 24.368: "Non-Access Stratum (NAS) configuration Management Object (MO)".
TS 23.060: "General Packet Radio Service (GPRS); Service description; Stage 2".

1.2  Abbreviationsp. 7

Abbreviations are listed in TR 21.905.
In addition, for the purposes of the present document, the following abbreviations apply:
Automatic Device Detection
Closed Subscriber Group
CSG Subscriber Server
Provision of User Equipment Specific Behaviour Information to Network Entities
User Equipment Specific Behaviour Information over the Iu interface

2  Definitionsp. 7

2.1  Location managementp. 7

Location management means that the PLMNs keep track of where the MSs are located in the system area. The location information for each MS is stored in functional units called location registers. Functionally, there are two types of location registers:
  • the Home Location Register where all subscriber parameters of an MS are permanently stored, and where the current location may be stored;
  • the Visitor Location Register where all relevant data concerning an MS are stored as long as the station is within the area controlled by that visitor location register;
  • the CSG Subscriber Server where the CSG subscription data are stored in the visited PLMN for inbound roaming MS, and where the current location may be stored.
See also TS 23.002 where the network architecture is described, and TS 23.008 where the data stored in the location registers are described.
The action taken by a MS in order to provide location information to the PLMN will be referred to as location updating.

2.2  Location area and MSC areap. 8

The MSC area is composed of the area covered by all base stations controlled by the MSC. An MSC area may consist of several location areas. A location area is an area in which, after having performed a location update once, MSs may roam without being required to perform subsequent location updates for reason of location change. A location area consists of one or more cells.
For further details of the network architecture, see TS 23.002.

2.3  Location area identificationp. 8

The Location Area Identification (LAI) plan is part of the base station identification plan. The base stations are identified uniquely (see TS 23.003).

2.4  IMSI detach/attach operationp. 8

The support of IMSI detach/attach operation is mandatory in MSs. The facility is optional in the fixed infrastructure of the PLMN.

2.4.1  Explicit IMSI detach/attachp. 8

Explicit IMSI detach operation is the action taken by an MS to indicate to the PLMN that the station has entered an inactive state (e.g. the station is powered down). Explicit IMSI attach operation is the action taken by an MS to indicate that the station has re-entered an active state (e.g. the station is powered up).

2.4.2  Implicit IMSI detachp. 8

Implicit IMSI detach operation is the action taken by the VLR to mark an MS as detached when there has been no successful contact between the MS and the network for a time determined by the implicit detach timer. The value of the implicit detach timer is derived from the periodic location updating timer; when the MSC/VLR applies Mobility Management Congestion Control to a MS, the MSC/VLR may need to adjust the Implicit Detach timer as specified in clause 3.7.2. During an established radio contact, the implicit detach timer shall be prevented from triggering implicit detach. At the release of the radio connection, the implicit detach timer shall be reset and restarted. Implicit IMSI detach shall also be performed in the case of a negative response to an IMEI check.

2.5  Use of the term mobile station (MS) in the present documentp. 8

In order to simplify the text the term Mobile Station (MS) as used in relation to location management refers to the entity where the IMSI is stored, i.e., in card operated MSs the term Mobile Station (MS) refers to the card.

2.6  Paging area |R8|p. 8

As an option, and for paging optimization purpose, the VLR may control Paging Areas. A Paging Area (PgA) is composed of up to 5 Location Areas, and the MSC area is composed of several Paging Areas. Paging areas may overlap each other. The Paging Area is stored in the HLR and updated at each paging area change. The Paging Area is sent by the HLR to the VLR at roaming number request and may be used by the MSC/VLR for paging (e.g. when LAI is not known, after MSC/VLR restart) (see TS 23.018).

3  General procedures in the network related to Location Managementp. 9

3.1  Procedures in the MSC related to Location Updatingp. 9

The MSC shall pass messages related to location updating between the MS and the VLR.

3.2  Procedures in the VLR related to Location Updatingp. 9


3.3  Procedures in the HLR related to Location Updatingp. 9


3.4  Normal Location Updating and IMSI detach/attach operationp. 9

When receiving a Location Updating Request or an IMSI detach/attach message from an MS, the MSC shall convey the message to its associated Visitor Location Register. Any response from the location register shall similarly be conveyed to the MS.

3.5  IMSI enquiry procedurep. 9

The MS shall identify itself by either the IMSI or the TMSI plus Location Area Identification of the previous VLR. In the latter case the new VLR shall attempt to request the IMSI and authentication parameters from the previous VLR by the methods defined in TS 29.002.
If this procedure fails, or if the TMSI is not allocated, the VLR shall request that the MS identifies itself by use of the IMSI.

3.6  Information transfer between Visitor and Home Location Registersp. 9

3.6.1  Procedures for location managementp. 9

Detailed procedures for exchange of and location updating information between visitor and home location registers are given in TS 29.002. Below follows an overview of these procedures.  Location updating procedurep. 9

This procedure is used when an MS registers with a Visitor Location Register.
The VLR provides its address to the HLR.
The VLR may also allocate an optional identity for the MS at location updating: the Local Mobile Station Identity (see TS 23.003).  Downloading of subscriber parameters to the VLRp. 9

As a part of the location updating procedure, the Home Location Register will convey the subscriber parameters of the MS which need to be known by the visitor location register for proper call handling. This procedure is also used whenever there is a change in the subscriber parameters that need to be conveyed to the VLR (e.g. change in subscription, a change in supplementary services activation status).
If the HPLMN applies the multinumbering option, different MSISDNs are allocated for different Basic Services (see TS 29.007) and stored in the HLR. Among these MSISDNs, the Basic MSISDN Indicator as part of the HLR subscriber data (see TS 23.008) marks the 'Basic MSISDN' to be sent to the VLR at location update. It is used in the VLR for call handling as calling party and as line identity.
If the HPLMN applies the Administrative Restriction of Subscribers' Access feature, the HLR shall convey the subscriber access restriction parameter (AccessRestrictionData) to the VLR. The VLR shall check this subscription parameter against the radio access technology that supports the LA/RA in which the UE is roaming to decide whether the location update should be allowed or rejected.
For further information of the Subscriber access restriction see TS 23.008.
Up  Location cancellation procedurep. 10

The procedure is used by the home location register to remove a MS from a visitor location register. The procedure will normally be used when the MS has moved to an area controlled by a different location register. The procedure can also be used in other cases, e.g. an MS ceases to be a subscriber of the Home PLMN.  Mobile subscriber purging procedurep. 10

A VLR may purge the subscriber data for an MS which has not established radio contact for a period determined by the network operator. Purging means to delete the subscriber data and to "freeze" the TMSI that has been allocated to the purged MS in order to avoid double TMSI allocation. The VLR shall inform the HLR of the purging.
When the HLR is informed of the purging, it shall set the flag "MS purged" in the IMSI record of the MS concerned. Presence of the "MS purged" flag will cause any request for routing information for a call or short message to the MS to be treated as if the MS were not reachable.
In the VLR, the "frozen" TMSI is freed for usage in the TMSI allocation procedure by location updating for the purged MS in the same VLR, location cancellation for the purged MS or, in exceptional cases, by O&M.
In the HLR, the "MS purged" flag is reset by the location updating procedure and after reload of data from the non-volatile back-up that is performed when the HLR restarts after a failure.
Up  Support for subscription without MSISDN |R11|p. 10

An MSC/VLR may support delivery of SMS destined to an MS without MSISDN for GPRS and EPS operation whereby a MSISDN is not allocated as part of the subscription data (see TS 23.060, clause 5.3.17 and TS 23.401).
An MSC/VLR which supports MSISDN-less operation shall indicate such support to the HLR in the MAP Update Location request.
The HLR should reject a MAP Update Location request received for an MSISDN-less subscription from a VLR not indicating support of MSISDN-less operation, with a cause indicating that roaming is not allowed.
The HLR shall download the subscriber parameters to the VLR as per clause but without an MSISDN for an MSISDN-less subscription if the VLR indicates support of MSISDN-less operation.

3.7  Overload Protection |R10|p. 11

3.7.1  Overviewp. 11

As the number of mobile devices increase and become more automated (Machine Type Communication, MTC type devices) the network is at greater risk of becoming overloaded. Additional mechanisms may be deployed to prevent and or control overload and congestion. This clause describes such optional mechanisms.
The succeeding descriptions applies to Network Mode of Operation II (requesting CS only). For NMO I (requesting both CS and PS) the procedures are described in TS 23.060.

3.7.2  Congestion Control during Mobility Managementp. 11

The MSC or VLR may support the capability to reject Location Updating Requests or IMSI Attach messages from an MS if the node is experiencing congestion.
The MSC/VLR may indicate the rejection is due to congestion with a specific congestion cause value and a specific back-off timer, see TS 24.008.
The Mobility Management back-off timer shall not impact Cell/RAT and PLMN change. Cell/RAT and RA change do not stop the Mobility Management back-off timer. The Mobility Management back-off timer shall not be a trigger for PLMN reselection. The back-off timer is stopped as defined in TS 24.008 when a new PLMN that is not an equivalent PLMN is accessed.
While the Mobility Management back-off timer is running, the MS shall not initiate any Mobility Management procedures. However, the MS is allowed to initiate Mobility Management procedures for priority/emergency services and mobile terminated services even when the Mobility Management back-off timer is running.
If the MS receives a paging request from the MSC/VLR while the Mobility Management back-off timer is running, the MS shall stop the Mobility Management back-off timer and initiate the CM Service Request procedure.To avoid that large amounts of MSs initiate deferred requests (almost) simultaneously, the MSC/VLR should select the Mobility Management back-off timer value so that deferred requests are not synchronised.
The decision to apply congestion control is made by the MSC/VLR, the detailed criteria for which is outside the scope of this specification but may for example take into account the low access priority indication if signalled by MSs.
The MSC/VLR should use implicit detach timer values that are larger than the Mobility Management back-off timer values to avoid that the MSC/VLR implicitly detaches the MS before the MS has performed a LAU procedure, which could lead to unneccessary signalling after the back-off timer expires.

3.7.3  Extended periodic LAU Signallingp. 11

To reduce network load from periodic location updating (LAU) signalling and to increase the time until the MS detects a potential need for changing the RAT or PLMN (e.g. due to network problems) longer values of the periodic LAU timer and implicit detach timer should be supported.
A long periodic LAU timer value may be locally configured at the MSC/VLR for MS configured for low access priority (see TS 24.368) or may be stored as part of the subscription data in the HLR. During the IMSI Attach and Location Updating procedures, the MSC/VLR should allocate the periodic LAU timer value for the MS based on VPLMN operator policy, low access priority indication from the MS, and subscription information received from the HSS. If the allocated periodic LAU timer value is longer than T3212, the MSC/VLR shall provide the MS with the periodic LAU timer in the Location Updating Accept message as specified in TS 24.008.
If the subscriber is not roaming and the MSC/VLR receives a subscribed periodic LAU timer value from the HSS, it should allocate the subscribed value to the MS as periodic LAU timer. If the subscriber is roaming and the MSC/VLR receives a subscribed periodic LAU timer value from the HSS, the MSC/VLR may use the subscribed periodic LAU timer value as an indication to decide for allocating a locally configured periodic LAU timer value to the MS.

3.8  Information transfer between VLR and CSG Subscriber Server |R11|p. 12

3.8.1  Procedures for location managementp. 12  Generalp. 12

Detailed procedures for exchange of and location updating information between VLR and CSG Subscriber Server are given in TS 29.002. This clause follows an overview of these procedures.  Updating VCSG Location procedurep. 12

This procedure is used when an MS registers with a Visitor Location Register and there is a need to do a registration with the CSS.
The VLR provides its address to the CSS.  Downloading of VPLMN CSG subscription data to the VLRp. 12

As a part of the location updating procedure, the CSG Subscriber Server shall convey the VPLMN CSG subscription data of the roaming MS which needs to be known by the visitor location register for determine whether the MS can access the current cell to have CS services. This procedure is also used whenever there is a change in the VPLMN CSG subscription data that needs to be conveyed to the VLR.  VCSG Location cancellation procedurep. 12

The procedure is used by the CSS to remove a MS from a CSS. The procedure will normally be used when there is a removal of the CSG subscription data in CSS and of the MS registration including the case where a MS was registered in CSS but without CSG data.

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