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AP IX-128-E
Contents of Recommendation Q.1003
LOCATION REGISTRATION PROCEDURES
1. Introduction
2. Definitions
3. Procedures in the MS related to
location registration
4. Procedures in the MSC/BS related to
location updating
5. Procedures in the location registers
Annex A - Organization of the subscriber data
Recommendation Q.1003
LOCATION REGISTRATION PROCEDURES
1. Introduction
This Recommendation specifies the procedures related to location
registration. They include:
- location registration;
- location cancellation;
- periodic registration; and
- IMSI attach/detach.
The procedures in the MS, MSC, VLR and HLR are also given. The
procedures utilize the Mobile Application Part (MAP) and details concerning
the exchange of information are contained in Recommendation Q.1051.
2. Definitions
2.1 Location registration
Location registration means that the PLMNs keep track of where mobile
stations are located in the system area. The location information is stored in
functional units called location registers. Functionally there are two types of
location registers:
- the home location register where the current location and all
subscriber parameters of a mobile station are permanently stored; and
- the visitor location register where all relevant parameters
concerning a mobile station are stored so long as the station is within
the area controlled by that visitor location register.
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See also Recommendation Q.1001 where the network architecture is
described.
The action taken by a mobile station in order to provide location
information to the PLMN will be referred to as location updating.
2.2 Location area and MSC area
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 mobile stations may roam without
updating the location registers. A location area consists of one or more base
station areas.
Paging procedures will be required on the radio path if the location
area consists of more than one base station area. The paging procedure is used to
determine the base station area in which the MS is located.
For further details of the network architecture and for definitions,
see Recommendation Q.1001.
2.3 Location area identification
The location area idenfication plan is part of the base station
identification plan. The base stations should be identified uniquely and the base
station identity should include mobile country code, mobile network (PLMN) code,
location area code and base station code within the location area where the
location area identification consists of the first three elements. Furthermore, it
is viewed that based on network considerations, the mobile country code and base
station code may be optional in identifying where the location area
identification is included in all messages sent on common signalling channels on the radio
path.
2.4 IMSI detach/attach operation
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). 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).
IMSI detach/attach operation is an optional facility in PLMNs.
2.5 Use of the term mobile station (MS) in this Recommendation
In order to simplify the text the term mobile station (MS) as used in
relation to location registration refers to the entity where the IMSI is stored,
i.e., in the card operated MSs the term mobile station (MS) refers to the card.
3. Procedures in the MS related to location registration
3.1 Initiation of location register updating
Automatic location updating should take place as follows.
The mobile station initiates location updating when it detects that it
has entered into a new location area. The location area identification should
be stored in a non-volatile memory in the MS so that the memory content does not
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disappear when the MS is turned off. This will avoid unnecessary location
updating when the MS is still in the same location area when it is turned on again.
If the MS has lost the location information from memory, it will
initiate location updating as soon as it is in an operational state and within radio
coverage.
Location updating is also initiated on time-out of the timer T defined
in 3.2.
Location updating via manual intervention in the MS is for further
study.
3.2 Periodic location updating
A timer T with the following characteristics could be optionally
implemented in the MS:
i) timer T is reset to 0 and started when a signalling activity has
taken place on the radio path;
ii) when the MS is powered down the current value of T is kept in
memory, so that when the MS is powered up the timer starts running from
the value thus contained in memory; and
iii) when timer T reaches its time-out value, the MS initiates a
location updating.
Timer T thus measures the accumulated time between signalling
activities in the MS while the MS is in the powered up state.
In order to ensure:
i) that the location of silent and stationary MSs are checked at a
reasonable rate; and
ii) that the timer T does not mature to time-out in the majority of
cases.
The time-out value of timer T should be of the order of several hours
(e.g. in the range of 12 to 24 hours). See also Recommendation Q.1004.
3.3 Receiving acknowledgement from the PLMN
The MS may receive either of the following acknowledgements from the
PLMN.
i) Location updated, roaming allowed. In this case normal call
handling operations will take place in the MS.
ii) Location updated, roaming not allowed. In this case, the MS will
not be allowed to make calls. The MS should follow the procedure of
3.1 and 3.2 above. The MS will resume normal operation if it
receives a location updated, roaming allowed indication from the PLMN.
iii) Updating failure, indicating that the procedure in the PLMN
failed. In this case, the MS should initiate a new updating after a
given time. If this attempt fails, the MS should follow the normal
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procedures of 3.1 and 3.2. When receiving the updating failure
indication, the MS should be capable of normal call handling
operation.
iv) Insufficient identification, indicating that the PLMN was not
capable of identifying the MS. The MS should then initiate a new
udating using the IMSI. The MS should follow the procedures of 3.1 and
3.2 above.
v) Not registered, indicating that the MS is not known in the HLR.
The MS should then reject any call attempts from the user. However,
the MS should follow the normal procedures of 3.1 and 3.2.
vi) Illegal subscriber, indicating that the MS is not allowed access
to the system for authenticity reasons. The MS may
follow the normal procedures of 3.1 and 3.2.
3.4 Procedure when acknowledgement is not received
If the MS does not receive an acknowledgement (on layer 3) on an
updating request, the MS may retransmit the message three times with at
least ten seconds (see 3.5) between consecutive attempts. If the
procedure fails also for the third time, the general procedures of 3.1 and 3.2
should be followed.
3.5 Minimum time between location updatings
The minimum time between consecutive location updatings should be
ten seconds in order to avoid erroneous location information to be stored
because of delays in the signalling network for information transfer via
the mobile application part.
3.6 IMSI detach/attach operation
IMSI detach/attach operation is an optional facility in PLMNs. The
facility is also optional in MSs.
The network should provide an indicator to the MS indicating whether or
not IMSI detach/attach operation is allowed in a PLMN. MSs which are not
equipped for IMSI detach/attach operation will ignore this indicator. MSs which are
equipped for IMSI detach/attach operation shall operate in accordance with the
received value of the indicator.
When IMSI detach/attach operation applies, an MS equipped for this type
of operation and located in an area where roaming is allowed should send the IMSI
detach signal to the MSC when the MS enters the inactive state (e.g. when the MS
is powered down). When the MS again enters the active state, the IMSI attach
signal is sent to the PLMN, provided that the MS is still in the same location area.
If the location area has changed, the normal location upating of 3.1 shall take
place.
The IMSI detach signal will not be acknowledged from the PLMN.
The IMSI attach signal will be acknowledged from the PLMN. If the
acknowledgement indicates that the MS is not registered or that the identification is
insufficient, the MS should initiate the normal location updating procedure of
3.1.
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If the acknowledgement is not received, the MS should retransmit the IMSI
attach signal after a given time. If the second attempt fails, the MS should
follow the procedure of 3.2. However, in this state the MS is allowed to make
calls.
3.7 Location updating after handover
See Recommendation Q.1005.
3.8 SDL description of the procedures in the MS
Figure 1/Q.1003 shows state transition diagrams for procedures in the MS
related to location updating. The diagrams are intended for guidance.
The following states are identified:
State 0: inactive
This state would in most cases correspond to the powered down state of
an MS. The input signal IMSI attached may correspond to power up of the station.
State 1: Roaming allowed, updated
In this state the MS is fully operational.
State 2: Wait for updating
This is a transitional state where location updating takes place. In this
state the MS cannot make or receive calls.
State 3: Wait for IMSI attached
This transitional state is only required in MSs which are designed for
IMSI detach/attach operation. In this state the MS cannot make or receive calls.
State 4: Roaming not allowed
In this state the MS is not allowed to make calls (except emergency
calls) and will not receive calls.
State 5: Not updated
This state is entered if the location updating or IMSI attach procedure
fails. In this state the MS will not receive calls.
4. Procedures in the MSC/BS related to location updating
The MSC/BS will pass messages related to location updating between the MS
and the VLR.
The MSC/BS will provide the location area identification and IMSI
detach/attach supported information to the MS.
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FIGURE 1/Q.1003 (Sheet 1 of 5)
Logic procedures in the MS for location updating
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FIGURE 1/Q.1003 (Sheet 2 of 5)
Logic procedures in the MS for location updating
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FIGURE 1/Q.1003 (Sheet 3 of 5)
Logic procedures in the MS for location updating
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FIGURE 1/Q.1003 (Sheet 4 of 5)
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Logic procedures in the MS for location updating
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FIGURE 1/Q.1003 (Sheet 5 of 5)
Logic procedures in the MS for location updating
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5. Procedures in the location registers
5.1 Information to be stored in location registers
The home and visitor location registers should contain information as
defined in Annex A.
5.2 Information transfer between MSCs/BSs and the associated visitor location
register
The procedures for information transfer between MSCs/BSs and the
associated visitor location registers using Signalling System No. 7 are defined in
Recommendation Q.1051.
5.2.1 Normal location updating and IMSI detach/attach operation
When receiving a location register updating message or an IMSI
detach/attach message from an MS, the MSC/BS will convey the message to its associated
visitor location register. The response from the location register will similarly be
conveyed to the MS.
5.2.2 Location updating as part of call set-up
Location registration may also take place during call set-up if the
request for call set-up comes from an MS which is not registered in the visited
location register. This applies in particular to the case where a previous updating was
unsuccessful. In such cases the MSC/BS should not establish the call until the
location register updating has been completed.
Location register updating will also take place if the visitor location
register receives signalling information from an unknown MS, e.g. a request for
activation of a supplementary service.
5.3 IMSI enquiry procedure
The MS may either identify itself by the IMSI or the TMSI plus location
area identification of the previous VLR. In the latter case the new VLR will
enquire the IMSI from the previous VLR by methods defined in Recommendation Q.1051.
5.4 Information transfer between visitor and home location registers
5.4.1 Interconnection of location registers
Location registers may be interconnected by use of Signalling System No.
7 by procedures defined in Recommendation Q.1051. On a national basis other
networks may be used for this purpose.
5.4.2 Procedures for location registration
Detailed procedures for exchange of location registration and location
register updating information between visitor and home location registers are given
in Recommendation Q.1051. Below follows an overview of these procedures.
5.4.2.1 Location updating procedure
This procedure is used when an MS registers with a visitor location
register. It will also be used if the visitor location register has to reallocate the
mobile station roaming number for an MS (see Recommendation E.213).
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The visitor location register provides routing information to the home
location register. This information consists of the mobile station roaming number
which is used for routing of calls to the MS.
The home location register will then convey the subscriber parameters of
the MS which need to be known by the visitor location register for proper call
handling.
5.4.2.2 Location cancellation procedure
The procedure is used by the home location register to remove a mobile
station 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.
5.4.2.3 Deregistration procedure
If supported, the deregistration procedure is initiated by the VLR when
it receives an IMSI detach request, see 3.6. The corresponding IMSI is then
deleted from the VLR tables. The HLR marks the subscriber as not registered and will
reject all calls to that subscriber until a new updating procedure has taken
place.
5.4.2.4 Location information requested procedure
This procedure enables a visitor register to enquire whether or not an MS
is still to be kept in the register.
5.4.2.5 Location information retrieval procedure
By use of this procedure the home location register may obtain
information on which of its MSs are registered with a visitor location register. The
procedure may be used after a restart of the location register. The actual use of this
procedure is for further study.
5.4.2.6 Reset procedure
The reset procedure is used for recovering from a restart of a home
location register. A reset message is sent to visitor location registers so that
recovery procedures can be initiated.
5.4.2.7 Recovery procedure
Recovery and restoration procedures for location registers are defined in
Recommendations Q.1004 and Q.1051.
Recovery arrangements should be such that MSs with valid subscriptions
are not deleted from the HLR as a result of HLR failure. The worst result of an HLR
failure will thus be that some MSs are stored with errors in the temporary
subscriber data.
5.5 Overview state diagrams for location registers
Figures 2/Q.1003 and 3/Q.1003 contain overview state transition diagrams
for the home location register and the visitor location register, respectively,
with regard to one MS. Reset procedures are not included in these diagrams, i.e.
only the normal case is shown.
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The state description is as follows.
i) Home location register
State 0: Null. In this state the MS has no subscription with the
PLMN. Restart arrangements of the home location
register should be such that this state is not
reached for any MSs which have a subscription with
the PLMN which is valid at the time of the
restart.
State 1: MS not registered. In this state the location of the MS
is not known. The MS is not offered any
communication capabilities in this state.
State 2: MS in visitor location register (VLR), roaming allowed.
In this state the MS is offered communication capabilities
in the visitor location register in accordance
with those established by the location updating
procedure of 5.4.2.1.
State 3: MS in visitor location register, roaming not allowed.
In this state the MS is not offered any
communication capabilities, except emergency calls, in
the visitor location register. The home location
register will contain an indication that the MS is
in an area where the roaming not allowed
condition applies. The visitor location register will not
store any information concerning that MS.
ii) Visitor location register
State 0: Null. In this state the MS is not known to the visitor
location register.
State 1: MS in visitor location register, roaming allowed. In
this state the MS is offered communication
capabilities in accordance with those established by
the location updating procedure of 5.4.2.1.
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FIGURE 2/Q.1003 (Sheet 1 of 2)
State diagram for home location register
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FIGURE 3/Q.1003 (Sheet 1 of 2)
State diagram for visitor location register
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FIGURE 3/Q.1003 (Sheet 2 of 2)
State diagram for visitor location register
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5.6 Additional updating procedures
5.6.1 Registration/erasure, activation/deactivation, invocation and
interrogation of supplementary services
The procedures defined in Recommendation Q.1051 enable MSs to
register/erase, activate/deactivate, invoke or interrogate supplementary
services in the visitor location register. The visitor location register
conveys the necessary information to the home location register.
5.6.2 Updating of other parameters
Recommendation Q.1051 also contains procedures by which the home
location register may update any set of subscriber parameters in a
visitor location register if they are changed when the MS is in the area controlled by
that visitor register. This may correspond to changes in subscription or of other
parameters such as authentication parameters.
5.7 Call handling functions of location registers
5.7.1 Retrieval of subscriber parameters on a per call basis
All subscriber parameters are stored in the home location register. A
subset of these parameters are stored in the visitor location register (see Annex A).
There are also cases where the visitor location register must obtain
subscriber parameters on a per call basis from the home location register of the MS.
The procedures are defined in Recommendation Q.1051.
5.7.2 Interrogation procedures
In fixed networks using the ISDN User Part of Signalling System No. 7 it
may be possible for an exchange of the fixed network to retrieve routing
information from the home location register of an MS prior to establishing a physical
connection for a call. If this is not possible, a gateway MSC will perform this
interrogation.
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AP IX-128-E
ANNEX A
(to Recommendation Q.1003)
Organization of subscriber data
A.1 Introduction
A.1.1 Definitions
For the purpose of this Recommendation the following terms are used.
Mobile station (MS): either a physical equipment or a card for which
subscriber data are stored.
Subscriber data: all information concerning a specific MS which is
required for service provisions, identification,
authentication, routing, call handling, charging, operation and
maintenance purposes. Some subscriber data are referred to as
permanent subscriber data, i.e. they can only be changed by
administrative means. Other data are temporary subscriber
data which may change as a result of normal operation of the
system. Some data are referred to as flexible length data,
i.e. further values than those listed may be required in
the future.
A.1.2 Storage facilities
Subscriber data is stored in two types of functional units.
Home location register (HLR): which contains all permanent subscriber
data and all relevant temporary subscriber data for all
MSs permanently registered in the HLR.
Visitor location register (VLR): which contains all subscriber data
required for call handling and other purposes for MSs
currently located in the area controlled by the VLR.
Note - It is for further study whether other types of functional units
containing MS parameters are to be included in this Recommendation or
not. Such units could include encryption key distribution centres,
maintenance centres, etc.
A.2 Definition of subscriber data
A.2.1 Data related to identification and numbering
A.2.1.1 International mobile station identity (IMSI) is defined in
Recommendation E.212. It consists of three parts MCC, MNC and MSIN. The
MCC consists of 3 digits and the MNC consists of 1 or 2 digits. The IMSI has
variable length depending on national requirements. The maximum length is
15 digits.
Only numerical characters (0 through 9) are used in the IMSI.
The IMSI is permanent subscriber data, and is stored in both the HLR
and the VLR.
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Note - The IMSI for mobile PBXs is for further study.
A.2.1.2 International mobile station number is defined in Recommendation E.213.
It is a PSTN/ISDN number and has a variable length which complies with the
requirements of the PSTN/ISDN in each country.
The international mobile station number is permanent subscriber data.
The international mobile station number is stored in both the HLR and the VLR.
Note - Mobile station numbers for mobile PBXs are for further study.
A.2.1.3 Temporary mobile station identity (TMSI) is assigned by the VLR and is
used for identification of an MS within the area controlled by the VLR. The purpose of
the TMSI is to support location confidentiality to mobile subscribers. TMSIs may not be
allocated to all MSs, e.g. if the location confidentiality service is offered only on
a subscription basis.
The TMSI is temporary subscriber data.
The TMSI is stored in the VLR.
A.2.2 Data related to mobile station types
A.2.2.1 Mobile station category comprises the following categories:
For further study.
Only one category is assigned for each MS.
Mobile station category is permanent subscriber data.
The length of the parameter is one octet.
Mobile station category is stored in the HLR and the VLR.
A.2.2.2 Mode of operation defines whether or not the MS is card operated. Only
two possibilities exist:
- card operated; and
- not card operated.
Mode of operation is permanent subscriber data.
The mode of operation is stored in the HLR and the VLR.
Note - It is for further study whether this data is required or not.
A.2.2.3. Preference indicates whether or not an MS is given preference access to
the PLMN under certain circumstances. This point is for further study.
Preference is permanent subscriber data.
Preference is stored in the HLR and the VLR.
A.2.3 Data related to authentication
For further study.
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A.2.4 Data related to roaming
A.2.4.1 Mobile station roaming number is defined in Recommendation E.213. It is a
PSTN/ISDN number and has a variable length which complies with the requirements of the
PSTN/ISDN in each country.
The mobile station roaming number is temporary subscriber data.
The mobile station roaming number is stored in the HLR and the VLR.
A.2.4.2 Location area identification consists of three parts: MCC, MNC and LAC,
where MCC is the Mobile Country Code and MNC is the Mobile Network Code of
Recommendation E.212 and LAC is a Location Area Code identifying a location area within a PLMN.
MCC and MNC are composed of numerical characters (0 through 9). LAC may have a variable
length and may be coded using full haxadecimal representation.
The overall length of the location area identification is for further study.
The location area identification is temporary subscriber data.
The location area identification is stored in the VLR. It may also be required
in the HLR; this is for further study.
A.2.4.3 VLR address is a PSTN/ISDN number and has variable length which complies
with the requirements of the PSTN/ISDN in each country.
The VLR address is temporary subscriber data.
The VLR address is stored in HLR.
A.2.5 Data related to supplementary services
For further study.
A.2.6 Mobile station status data
A.2.6.1 MS registered/deregistered is a parameter indicating whether the MS is in
the registered or deregistered state. The parameter takes the following values:
- registered, or
- not registered.
The parameter is temporary subscriber data.
The parameter is stored in the HLR.
A.2.7 Other subscriber data
This is for further study.
A.3 Subscriber data stored in HLR
The following information should be stored in the HLR for each MS:
i) international mobile station identity ( A.2.1.1);
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ii) international mobile station number ( A.2.1.2);
iii) mobile station roaming number ( A.2.4.1);
iv) mobile station category ( A.2.2.1) and mode of operation
( A.2.2.2);
v) preference (if implemented) ( A.2.2.3);
vi) authentication parameters ( A.2.3);
vii) VLR address (if received) ( A.2.4.3);
viii) location area identification (if required) ( A.2.4.2);
ix) supplementary service type ( A.2.5.1.1);
x) mobile station status data ( A.2.6); and
xi) other subscriber data, if required ( A.2.7).
A.4 Subscriber data stored in VLR
The following information should be stored in the VLR for each visiting
MS:
i) international mobile station identity ( A.2.1.1);
ii) international mobile station number ( A.2.1.2);
iii) mobile station roaming number ( A.2.4.1);
iv) temporary mobile station identity ( A.2.1.3);
v) mobile station category ( A.2.2.1) and mode of operation
( A.2.2.2.);
vi) preference (if implemented) ( A.2.2.3);
vii) authentication parameters ( A.2.3);
viii) location area identification ( A.2.4.2); and
ix) other subscriber data, if required ( A.2.7).
A.5 Accessing subscriber data
It should be possible to retrieve or store subscriber data concerning a
specific MS from the HLR by use of each of the following references:
- international mobile station identity; or
- international mobile station number.
It should be possible to retrieve or store subscriber data concerning a
specific MS from the VLR by use of each of the following references:
- international mobile station identity;
- mobile station roaming number; or
CCITT\APIX\128E3.TXS
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- temporary mobile station identity.
CCITT\APIX\128E3.TXS
