Abstract:
A method of and equipment for subscriber mobility registration update in a Home Location Register, HLR, of a Global System for Mobile communications, GSM, or a Universal Mobile Telecommunications System, UMTS, mobile telecommunications network. The HLR receives and stores subscriber mobility registration information from at least one Mobile Switching Centre, MSC, of the telecommunications network. The HLR instructs an MSC to forward intermediate subscriber mobility registration update messages to the HLR for specific mobility events of a subscriber. The HLR receives an intermediate subscriber mobility registration update message of the MSC when such a specific mobility event occurs, and the subscriber mobility registration in the HLR is updated on the basis of a received intermediate subscriber mobility registration update message by the HLR. The method is especially applicable for IP Multimedia Subsystem Centralised Services, ICS.

Description:
TECHNICAL FIELD  
       [0001]    The present invention relates generally to telecommunications and, more specifically, to subscriber mobility registration update in a Home Location Register, HLR, of a mobile telecommunications network, being a Global system for Mobile communications, GSM, or a Universal Mobile Telecommunications System, UMTS. The invention is particularly applicable for IP Multimedia System, IMS, services. 
       BACKGROUND OF THE INVENTION 
       [0002]    In existing GSM or UMTS telecommunications networks, hereinafter generally referred to as GSM networks, GSM or UMTS subscribers from a given geographical area are attached to the network by a Mobile Switching Centre, MSC, which serves that area. When a GSM or UMTS subscriber, hereinafter generally referred to as subscriber, initially attaches to an MSC using a GSM or UMTS Mobile Station, MS, such as but not limited to a mobile telephone, a Personal Digital Assistant, PDA, or a laptop, the MSC initiates a Location Update procedure. The Location Update procedure involves updating the HLR of the subscriber by a suitable update message comprising the current location, in the form of an. MSC address, of the subscriber. This Location Update procedure is hereinafter referred to as “initial” or “standard” or “regular” Location Update procedure, being the Location Update procedure known in the art. The update message, from the MSC to the HLR, initiating the Location Update procedure, is called an “initial subscriber mobility registration update message”. 
         [0003]    The HLR of a subscriber is a central database where information concerning the subscriber is stored, such as account numbers, features, preferences, permissions, etc. During the regular Location Update procedure the HLR is updated, by the MSC, with the address of the MSC to which the subscriber is attached. It is in turn the responsibility of the HLR to send GSM subscription data for that subscriber to the particular MSC. The information stored in the HLR is also used for various other services, such as detaching from the MSC, as will be appreciated by those skilled in the art. 
         [0004]    If the subscriber “moves” to another MSC, e.g. by changing the geographical location and entering the area served by another MSC, the HLR is contacted and updated again by this other MSC. The HLR will now send subscription data to that other MSC and will instruct the previous MSC to remove the subscription data for that subscriber. This procedure, know in the art, is called an inter-MSC location area update. In this way, the HLR always comprises the MSC address where the subscriber is registered. 
         [0005]    However, the subscriber may move from one location area to another location area within an MSC. Such change corresponds to a location area update within an MSC, called an intra-MSC location area update and does not result in a Location Update procedure to the HLR. Neither is detaching and attaching within an MSC notified to the HLR. Accordingly, in a GSM network the HLR has limited information about the specific geographical location of the subscriber, as well as the status (attached/detached) of the subscriber. 
         [0006]    The aforementioned limited information results in limitations in functionality of the HLR in those cases where the location area of the subscriber and/or the status of the subscriber (attached/detached) plays a role. Examples of such cases include: 
         [0007]    Terminating Call Handling: 
         [0008]    The MSC address stored in the HLR is used for terminating call handling features. However, in some regions, such as the Caribbean, one MSC serves multiple countries (islands). Each country has one Base Station Controller, BSC, corresponding to one location area. Since in the HLR only the MSC address and not the location area is stored, the HLR cannot properly handle a terminating call, because the terminating call handling should correspond to a location area and not to the MSC. 
         [0009]    IP Multimedia Subsystem Centralised Services, ICS: 
         [0010]    If IP Multimedia System, IMS, services are offered to subscribers in the GSM network via IMS Centralised Services, ICS, the subscriber needs to be registered in the IMS network. This registration should be aligned with the status (attached/detached) of the subscriber. As this status is not always updated in the HLR, the HLR cannot handle the IMS registration/deregistration for the subscriber. 
       SUMMARY  
       [0011]    It is an object of the present invention to provide an improved subscriber mobility registration update in a HLR of a GSM network, enabling the HLR to gather, store and provide up-to-date information regarding the subscriber, including his location area and status (attached/detached) and thus enhance the functionality of the HLR, especially for IMS Centralised Services. 
         [0012]    It is a further object of the present invention to provide an HLR and MSC comprising equipment arranged for operating and supporting the improved subscriber mobility registration update. 
         [0013]    A first aspect of the invention comprises a method of subscriber mobility registration update in a Home Location Register, HLR, of a Global System for Mobile communications, GSM, or a Universal Mobile Telecommunications System, UMTS, mobile telecommunications network, wherein the HLR receives and stores subscriber mobility registration information from at least one Mobile Switching Centre, MSC, of the telecommunications network. The method comprises the steps of:
       instructing, by an HLR, an MSC to forward intermediate subscriber mobility registration update messages to the HLR for specific mobility events of a subscriber,   receiving, by the HLR, an intermediate subscriber mobility registration update message of the MSC when such a specific mobility event occurs, and   updating, by the HLR, the subscriber mobility registration in the HLR on the basis of a received intermediate subscriber mobility registration update message.       
 
         [0017]    The invention provides for an enhanced update of the HLR by the MSC, based on instructions previously received from the HLR, for specific mobility events. A subscriber mobility registration update resulting from one of the specific mobility events is hereinafter called an “intermediate subscriber mobility registration update”, this in contrast to the known “initial subscriber mobility registration update message”, disclosed above. 
         [0018]    The step of instructing preferably comprises specifying the specific mobility events, other than the initial mobility event, for which the MSC has to forward intermediate subscriber mobility registration update messages to the HLR. 
         [0019]    In a further example of the invention, the MSC supports IP Multimedia Subsystem, IMS, services and the step of instructing by the HLR comprises providing IMS subscription information of the subscriber to the MSC and instructing registration of the IMS subscription information by the MSC. 
         [0020]    According to another example, the HLR may instruct the MSC to forward intermediate subscriber mobility registration update messages for specific mobility events of a subscriber, only if required for the subscriber. 
         [0021]    Preferably, the step of instructing is performed after receipt, by the HLR, of an initial subscriber mobility registration update message of an MSC. 
         [0022]    In an other example, the method further comprises the step of initiating, by the HLR, an IP Multimedia Subsystem, IMS, registration or deregistration process with an IMS registration entity for a subscriber after receipt, by the HLR, of a subscriber mobility registration update message from an MSC. 
         [0023]    In a second aspect, as far as the activity of an MSC is concerned, the invention provides a method of subscriber mobility registration update in a Home Location Register, HLR, of a Global System for Mobile communications, GSM, or a Universal Mobile Telecommunications System, UMTS, wherein the HLR receives and stores subscriber mobility registration information from at least one Mobile Switching Centre, MSC, of the telecommunications network, comprising the steps of:
       receiving, by an MSC, instructions of an HLR to forward intermediate subscriber location update messages to the HLR for specific mobility events of a subscriber,   detecting, by the MSC, occurrence of such a specific mobility event, and   forwarding, by the MSC, an intermediate subscriber mobility registration update message to the HLR when such specific mobility event occurs.       
 
         [0027]    In a further example, the initial subscriber mobility registration update message from the MSC to the HLR may be enhanced by including at least any of the following information:
       whether the MSC supports forwarding of intermediate subscriber mobility registration update messages,   whether the MSC supports IP Multimedia Subsystem, IMS, subscriber registration,   current location information of a subscriber, and   further subscriber mobility registration parameters relating to intermediate subscriber mobility registration update.       
 
         [0032]    By providing enhanced initial subscriber mobility registration update information to the HLR, the HLR is able, based on this enhanced information, to instruct the MSC more specifically regarding the intermediate subscriber mobility registration update messages to be forwarded by the MSC. 
         [0033]    In a further example the MSC forwards, to the HLR, in an intermediate subscriber mobility registration update message at least one of:
       a specification of the specific mobility event which has led to the forwarding of the intermediate subscriber mobility registration update message, and   current location information of the subscriber.       
 
         [0036]    In an example of the method, the MSC supports IP Multimedia Subsystem, IMS, services, and the method further comprises the step of initiating, by the MSC, an IMS registration or deregistration process of the subscriber after receipt, by the MSC, of IMS subscription information of the subscriber from the HLR. 
         [0037]    In the method according to the invention, the mobility events preferably include at least one of a group comprising:
       intra-MSC location area location update,   subscriber&#39;s attachment to the MSC,   subscriber&#39;s detachment from the MSC.       
 
         [0041]    As apparent from the above disclosure of the inventive method, the subscriber mobility registration update messages exchanged between the MSC and the HLR are enhanced, comparing to the prior art, in the sense that they comprise additional information. Consequently, new parameters need to be defined and included in the update messages to contain this additional information. Such parameters are referred to as “the newly defined parameters” throughout this specification and claims. They may be defined in the so-called MM-Code data type, which exists in Mobile Application Part, MAP, signalling. 
         [0042]    In an example of the inventive method, Mobile Application Part, MAP, signalling is used in communications between the HLR and the MSC for exchanging subscriber mobility registration update messages and information. In the subscriber mobility registration update messages, known and newly defined parameters are placed behind the ellipsis character in the argument of the MAP message or behind the ellipsis character in the MAP result message, such that the communications are compatible to previous version(s) of the MAP message. 
         [0043]    That is, using the MAP signalling in subscriber mobility registration update messages exchanged between the MSC and the HLR, and placing the known and newly defined parameters behind the ellipsis character, as a result, the messages—enhanced according to the inventive method—will be accepted and understood by all network nodes, including MSCs and HLRs, possibly using earlier version(s) of the MAP message, with the known and newly defined parameters just ignored and the rest of the message being handled, according to rules known in the art. 
         [0044]    According to a further embodiment of the inventive method, the HLR serves as mobility node for the subscriber. 
         [0045]    In an IP Multimedia Subsystem, IMS, the component corresponding to a HLR in a GSM system is called Home Subscriber Server, HSS, which combines the functionality of the HLR with gathering, storing and providing information specially required by the IMS network. It is thus to be understood that the invention equally applies to the Home Subscriber Server of an IP Multimedia Subsystem, in the case that the HLR is functionally included in the HSS. Consequently, in a preferred embodiment of the inventive method, the HLR is functionally included in a HSS of an IMS. 
         [0046]    The invention covers also a Home Location Register, HLR, and a Mobile Switching Centre, MSC, both comprising equipment arranged for operating in accordance with the inventive method, as disclosed above. 
         [0047]    According to the basic concept of the invention, the HLR may receive enhanced subscriber mobility registration update messages, in particular resulting from the mobility events including intra-MSC location area change, GSM attach and GSM detach. Consequently, information about such events may be stored in the HLR and used whenever needed, e.g. for proper terminating call handling (according to the subscriber&#39;s location area). It may also be used by the HLR for proper handling of an IMS registration of the subscriber, in the case that the GSM system offers to the subscriber network implementations requiring such registration. The network implementations include Multi Access Extension, MAE, and IMS Centralised Services, ICS. 
         [0048]    Moreover, the HLR is capable of quickly handling Any Time Interrogation, ATI, related to the subscriber&#39;s location area or status. When receiving ATI, the HLR may retrieve the internally stored information, instead of having to obtain this information from the MSC. 
         [0049]    Last but not least, it is worth mentioning that the present invention enables storing and retrieving information related to mobility events in a simpler and more useful manner than entailed by the CAMEL Phase 3 mobility management procedure. In particular, due to enhanced subscriber information stored in the HLR, the HLR may function as the mobility node (mobility gateway) for the subscriber. 
         [0050]    The above-mentioned and other features and advantages of the invention will be best understood from the following description referring to the attached drawings. 
         [0051]    In the drawings, like reference numerals denote identical parts and steps or parts and steps performing an identical or comparable function or operation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0052]    The present invention will be further described in details with reference to the enclosed drawing, in which: 
           [0053]      FIG. 1  shows, in a schematic and illustrative manner, a simplified mobile telecommunications network, arranged for supporting the present invention. 
           [0054]      FIG. 2  shows, in a schematic and illustrative manner, an example of an enhanced signalling scenario between a subscriber, an MSC and an HLR in accordance with the invention, in the mobile telecommunications network of  FIG. 1 . 
           [0055]      FIG. 3  shows, in a schematic and illustrative manner, enhanced signalling scenarios between a subscriber, an MSC, an HLR and an IMS registration entity for a GSM detach followed by IMS deregistration, for a GSM attach, followed by IMS registration, and for an intra-MSC location update followed by IMS re-registration, respectively, in accordance with the invention, in the mobile telecommunications network of  FIG. 1 . 
           [0056]      FIG. 4  shows in a schematic and illustrative manner, an example of an enhanced signalling scenario between a subscriber, a first MSC, a second MSC and an HLR for an intra-MSC location update for a multi-zone MSC, enhanced in accordance with the invention, in the mobile telecommunications network of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0057]    The invention will now be explained in more details by the following examples, which are presented for illustrative purposes only and are not intended to limit the scope of the invention. 
         [0058]      FIG. 1  shows, in a schematic and illustrative manner, a mobile telecommunications network, such as a Global System for Mobile Communications, GSM, or a Universal Mobile Telecommunications System, UMTS, mobile telecommunications network, arranged for supporting the present invention. 
         [0059]    The mobile telecommunications network comprises a plurality of Radio Base Stations, RBS, or radio access stations  2 ,  3 ;  4 ,  5 ;  6 ,  7  which connect to a Base Station Controller, BSC,  8 ;  9 ;  10 , respectively. The BSC  8 ,  9  connect to a Mobile Switching Centre, MSC,  11 , and the BSC  10  connects to an MSC  12 . The MSC  11 ,  12  connect via a signalling network  13 , arranged for, among other, Mobile Application Part, MAP, signalling, to a Home Location Register, HLR,  14 . The MSC  11  connects to an IP Multimedia System, IMS, registration entity  38  of an IMS network  39  which provides access to the Internet  36 . The IMS network  39  comprises one or more Home Subscriber Server, HSS,  37  which combines the functionality of gathering, storing and providing information specially required by the IMS network  39 . 
         [0060]    A Mobile Station or Mobile Subscriber, MS,  1 , such as a telephone handset or a multi-media communications terminal, or the like, connects via a radio connection  18  to an RBS  2 ,  3 ,  4 ,  5 ,  6 ,  7  for communication with an other MS, the Internet  36  or other telecommunications subscribers, among which subscribers of a fixed telecommunications network or other mobile telecommunications networks which connect to an MSC (not shown). 
         [0061]    Those skilled in the art will appreciate that a practical mobile communications system may comprise a plurality of RBS, a plurality of MS, dependent on the extension and capacity of the telecommunications network, and a plurality of HLR and a plurality of MSC. 
         [0062]    Each RBS  2 ,  3 ,  4 ,  5 ,  6 ,  7  serves a particular geographical area. When the MS  1  moves in the area serviced by the mobile telecommunications network, a call in progress will be handed over from one RBS to another. If the MS  1  moves from an area serviced by any of the RBS  2 ,  3  to an area serviced by any of RBS  4 ,  5 , for example, the location of the MS  1  will be updated within the MSC  11 , called, an Intra-MS location area update. When the MS  1  moves into an area serviced by any of the RBS  6 ,  7 , the location update of the MS  1  involves a change of MSC address, i.e. from MSC  11  to MSC  12 , also called an inter-MSC location update. 
         [0063]    The MSC  11  and the MSC  12  and the HLR  14  comprise equipment  15 ,  16 ,  17 , respectively, either hardware or software or a combination of both, arranged for supporting improved subscriber mobility registration update in the HLR  14  in accordance with the invention, the operation of which will be elucidated below by a number of examples. 
       Example 1 
     Enhanced signalling during the Location Update procedure. 
       [0064]      FIG. 2  shows, in a schematic and illustrative manner, an example of a signalling scenario involving subscriber mobile station MS  1 , MSC  11  and HLR  14 , in accordance with the invention, in the case of a location update for the subscriber. In this example MAP signalling is used between the MSC  11  and the HLR  14 . In  FIG. 2 , the following steps are illustrated:
       the MS  1  registers in the MSC  11  (message  20 ),   an initial subscriber mobility registration update message (message  21 ) is sent from the MSC  11  to the HLR  14 , comprising the address of MSC  11  for storage  26  in the HLR  14 ,   the HLR  14  instructs the MSC  11  (message  22 ) to forward intermediate subscriber mobility registration update messages to the HLR  14  for selected mobility events,   when one or more of the selected mobility events occurs, the MSC  11  sends a corresponding intermediate subscriber mobility registration update message (message  23 ) to the HLR  14 ,   the HLR  14  updates  27  the subscriber mobility registration in the HLR on the basis of the received intermediate subscriber mobility registration update message  23 , or messages in the event of a plurality of occurring selected mobility events,   in turn, appropriate update confirmation messages may be sent from the HLR  14  to the MSC  11  (message  24 ) and from the MSC  11  to the MS  1  (message  15 ).       
 
         [0071]    In a particular example instruction message  22  is arranged such that the HLR  14  requests the MSC  11  to send intermediate subscriber mobility registration update messages whenever the subscriber switches his/her phone off (GSM detach). Message  22  may also include information on whether or not the MSC  11  should register  28  MS  1  in IMS  38 . 
         [0072]    With the message  21 , the MSC  11  indicates to the HLR  14  that it supports intermediate subscriber mobility registration updates. In an example of the invention, the regular MAP Update location is enhanced to carry the above-mentioned additional information about supporting intermediate subscriber mobility registration updates. The Update location argument of message  21  may be enriched by adding the following known and/or newly defined parameters, see also 3GPP TS 29.002 v7.9.0:
       cell global Id Or Service Area Id Or LAI: this parameter contains the current location of the subscriber; it is defined already in MAP;   intermediate Location Update Supported: this parameter indicates to the HLR that the MSC supports the intermediate subscriber mobility registration update procedures;   ims Registration Supported: this parameter indicates that the MSC supports the IMS registration procedure; if the HLR receives this parameter, it knows that the MSC takes care of registering the subscriber in the IMS; in such case, the HLR, nor any other network node, would need to take any further action for received intermediate subscriber mobility registration update messages and registering the subscriber; the IMS registration by the MSC is known to the person skilled in the art and is not further described in the present application,   intermediate Location Update: this parameter contains information related to an intermediate location update procedure and will be further explained.       
 
         [0077]    In the MAP signalling, the known and/or newly defined parameters for the Update location message  21  are placed behind the ellipsis, ‘. . . ’, character in the argument of the MAP message or behind the ellipsis in the MAP result message. This implies that the enhancement to the MAP protocol is backwards compatible (i.e. compatible to previous version(s) of the MAP message). The receiver of this message may discard parameters behind the ellipsis, if the receiver does not support these parameters. 
         [0078]    When the MS  1  attaches to the MSC  11  for the first time, the MSC  11  performs an initial or regular location update procedure, with the enhancement as described above. In turn, the HLR  14  sends to the MSC  11  a message  22  instructing the MSC  11  to forward intermediate subscriber mobility registration update messages to the HLR for selected mobility events. The HLR  14  also indicates, for which events the MSC should send intermediate subscriber mobility registration update messages. Message  22  may be included in the MAP Update location result, which is for that purpose enriched by adding the following parameters:
       requested-mobility-events: this parameter indicates to the MSC for which mobility events the MSC should send intermediate subscriber mobility registration update messages to the HLR;   ims Subscriber this parameter indicates to the MSC that the subscriber is an IMS subscriber. The HLR may include this parameter only if the MSC has indicated that it supports the IMS registration. When the MSC receives this parameter in the Update location result, it should perform IMS registration for the subscriber. If the Update location result relates to an intermediate subscriber mobility registration update or to an inter-MSC location update, then the subscriber is likely already IMS-registered. When the HLR then instructs the MSC to register the subscriber, then this IMS registration should overwrite the existing IMS registration;   register Subscriber this parameter indicates to the MSC that the MSC should perform IMS registration for the subscriber.       
 
         [0082]    The HLR  14  may request an intermediate subscriber mobility registration update message for one or more of the events defined in the MM-Code data type, which exists in MAP. For the intermediate Update location messages (which constitute a subset of intermediate subscriber mobility registration update messages), the following events are used:
       Location-update-in-the-same-Visitor Location Register,   International Mobile Subscriber Identity (IMSI)-Attach,   MS-initiated-IMSI-Detach,   Network-initiated-IMSI-Detach.       
 
         [0087]    The newly defined parameters for the Update location message result are placed behind the ellipsis in the argument of the MAP message or behind the ellipsis in the MAP result message; this implies that this enhancement to the MAP protocol is also backwards compatible. 
         [0088]    Similar to the initial subscriber mobility registration update message  21 , the intermediate subscriber mobility registration update message  23  may also be enhanced by adding the parameter intermediate Location Update to the argument. This parameter is defined as follows: 
         [0000]    
       
         
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 IntermediateLocationUpdate ::= SEQUENCE { 
               
               
                   
                    mobilityEvent [0] MM-Code  OPTIONAL, 
               
               
                   
                    extensionContainer [2] ExtensionContainer  OPTIONAL, 
               
               
                   
                    ...} 
               
               
                   
                   
               
             
          
         
       
     
         [0089]    The following parameters may be contained in IntermediateLocationUpdate:
       mobilityEvent: this parameter indicates which mobility event led to the intermediate subscriber mobility registration update procedure. It is defined as MM-Code.       
 
         [0091]    The intermediate subscriber mobility registration update message  23  may comprise also the location information, contained in cellGloballdOrServiceAreaOrLAI. 
         [0092]    When the HLR  14  receives the MAP intermediate subscriber mobility registration update message  23 , it deduces, by virtue of the presence of the intermediateLocationUpdate parameter, that this is an intermediate subscriber mobility registration update message, as opposed to an initial regular subscriber mobility registration update message. 
         [0093]    The enhanced features described above may be used selectively. In such case, the HLR  14  instructs the MSC  11  to send intermediate subscriber mobility registration update messages only when such messages are actually needed for this subscriber. For other subscribers, the HLR  14  will request and receive only the regular subscriber mobility registration update messages. It will be appreciated that the update step  27  may be performed each time an intermediate subscriber mobility registration update message is received. 
       Example 2 
     IMS Deregistration Handled by the HLR, Resulting from Switching off the Mobile Station, MS. 
       [0094]      FIG. 3  shows, in a schematic and illustrative manner, an enhanced signalling scenario involving the MS  1 , the MSC  11 , the HLR  14  and an IMS registration entity  38 , in accordance with the invention. 
         [0095]    In the case that MS  1  is switched off, the MSC  11  is notified about it (message  30 ). Then the MSC  11  sends to the HLR  14  an intermediate subscriber mobility registration update message  31 , according to the request from the HLR  14  received during the initial registration (as discussed in Example 1 above). In turn, the HLR  14 , using the message  31 , informs the IMS registration entity  38  that the MS  1 , or the subscriber, is detached (message  32 ). The subscriber is now de-registered from IMS (message  33 ). Finally, appropriate update confirmation messages may be sent from the HLR  14  to the MSC  11  (message  34 ) and from the MSC  11  to the MS  1  (message  35 ). 
         [0096]    The intermediate subscriber mobility registration update message resulting from Detach does not include location information, as explained in Example 1. Moreover, the MSC indicates in the intermediate subscriber mobility registration update message  31  that it supports the IMS registration and intermediate subscriber mobility registration updates. 
         [0097]    According to an example of the invention, the HLR  14  has to indicate in every update location result message, whether it wants the MSC  11  to send intermediate subscriber mobility registration update messages. If the HLR  14  does not include such request in the Update location result message, the MSC  11  will cease to send intermediate subscriber mobility registration update messages. 
       Example 3 
     IMS Registration Handled by the HLR, Resulting from Switching on the Mobile Station, MS. 
       [0098]    In the case that the subscriber&#39;s Mobile Station, MS  1 , is switched on again, which is also illustrated in  FIG. 3 , the MSC  11  is notified about it (message  40 ). Then the MSC  11  sends to the HLR  14  an intermediate subscriber mobility registration update message  41 , according to the request from the HLR  14  during the initial registration (as discussed in Example 1). In turn, the HLR  14  using the message  41 , informs the IMS registration entity  38  that the MS  1 , i.e. the subscriber, is attached (message  42 ). The subscriber is now registered in IMS (message  43 ). Finally, appropriate update confirmation messages may be sent from the HLR  14  to the MSC  11  (message  44 ) and from the MSC  11  to the MS  1  (message  45 ). 
         [0099]    In this case, the intermediate subscriber mobility registration update message  41  from the MSC  11  to the HLR  14  includes location information, in the form of the Cell Global Identifier, CGI. 
       Example 4 
     IMS Re-Registration Handled by the HLR, Resulting from Intra-MSC  Location Change 
       [0100]    In the case that the subscriber changes location within an MSC  11  (intra-MSC location change), that is when the subscriber is, resulting from the change of location, served by another BSC, for example BSC  9  instead of BSC  8 , both being connected to MSC  11 , for example, which is schematically indicated by a dashed arrow  19  in  FIG. 1 , several signalling messages are exchanged as illustrated in  FIG. 3 . The MSC  11  is notified about this (message  50 ). It shall be understood by the person skilled in the art that the message  50 , being sent from MS  1  to MSC  11 , traverses RBS and BSC. Then the MSC  11  sends to the HLR  14  an intermediate subscriber mobility registration update message  51 , according to the request received from the HLR  14  during the initial registration (as discussed in Example 1 above). In turn, the HLR  14 , using the message  51 , informs the IMS registration entity  38  that the subscriber has changed its location (message  52 ). The subscriber is now re-registered in IMS (message  53 ) with the new location. Finally, appropriate update confirmation messages may be sent from the HLR  14  to the MSC  11  (message  54 ) and from the MSC  11  to the MS  1  (message  55 ). 
         [0101]    In this case, the intermediate subscriber mobility registration update message  51  from the MSC  11  to the HLR  14  includes location information, in the form of the Cell Global Identifier, CGI. 
       Example 5 
     Enhanced Signalling During an Intra-MSC Location Update for a Multi-Zone MSC. 
       [0102]      FIG. 4  shows in a schematic and illustrative manner, an enhanced signalling scenario between the subscriber&#39;s Mobile Station, MS  1 , a first MSC  11 , a second MSC  12 , and the HLR  14 , according to the invention. In this case, an intra-MSC location update takes place within MSC  11 , wherein MSC  11  serves multiple charging zones, i.e. is a multi-zone MSC. 
         [0103]    It is assumed that at first the subscriber registers to the MSC  11 , while being outside his home location area. Then the regular location update procedure, enhanced as described in Example 1, takes place illustrated by messages  60 ,  61 ,  62 ,  63 ,  64 ,  65  in  FIG. 4  corresponding to messages  20 ,  21 ,  22 ,  23 ,  24 ,  25  in  FIG. 1 , respectively. 
         [0104]    When a notification  66  about an incoming call is received by the HLR  14  from the MSC  12 , this incoming call is barred, because the MS  1  is not within its home location area, following messages  67 ,  68 ,  69  in  FIG. 4 . In one embodiment of the invention, messages  67  and  68  may not be needed, since the HLR has sufficient information to know whether the called subscriber currently resides in her home location area or not. This knowledge is gathered by HLR due to the afore described intermediate Location update messages. 
         [0105]    However, later on the MS  1  changes location from the present location area to another location area, being its home location area, while staying within the range of MSC  11  (an intra-MSC location change). MSC  11  is notified about this (message  70 ). According to the initial request  62  from the HLR  14 , the MSC  11  sends an intermediate subscriber mobility registration update message  71  to the HLR  14 , including the subscriber&#39;s new location information. The information in the HLR  14  is updated accordingly and appropriate confirmation messages are sent back from the HLR  14  to the MSC  11  (message  72 ) and from the MSC  11  to the subscriber&#39;s MS  1  (message  73 ). 
         [0106]    When another notification  74  about an incoming call for the subscriber is received by the HLR  14  from the MSC  12 , this incoming call is allowed to be established, because this time the MS  1  is within its home location area, involving suitable registration and confirmation messages  75 ,  76 ,  77 ,  78 ,  79 ,  80 ,  81 . Reference numerals  82 ,  83  represent the continuation of the call establishment, i.e. between MSC  12  and MSC  11 , and between MSC  11  and MS  1 , respectively. 
         [0107]    Generally, when the HLR receives an incoming call for the subscriber MS (MAP Send Routing Information, SRI), the HLR can determine, based on the subscriber&#39;s current location area stored in the HLR, whether the subscriber is within his home location area or not. Based on that, the HLR may decide whether CAMEL terminating call handling shall apply for the call. 
         [0108]    The present invention is not limited to the embodiments as disclosed above, and can be modified and enhanced by those skilled in the art beyond the scope of the present invention as disclosed in the appended claims without having to apply inventive skills.