Abstract:
The present invention relates to method for managing subscriber location information in mobile communications system. When a mobile subscriber moves to other place, wherever, registration notification(RN) is carried out from a visitor location register(VLR) to a home location register(HLR). In case of requested with overlapped the registration notification(RN) and call processing procedure about the same subscriber, the HLR protects multi-location registrations about the same subscriber until a previous registration notification(RN) is completed. Thereby, this invention relates to method for managing subscriber location information in mobile system, in order to always maintain location information about a subscriber in the HLR and VLR, correctly.

Description:
TECHNICAL FIELD 
     The present invention relates to method for managing subscriber location information in a mobile communications system. When a mobile subscriber moves to another place, registration notification is carried out from a visitor location register(hereinafter, referring to VLR) to a home location register(HLR). In case that request for the registration notification and call processing procedure about the same subscriber is overlapped, the HLR protects multi-location registrations about the same subscriber until a previous registration notification is completed. Thereby, this invention relates to method for managing subscriber location information in a mobile communications system, for always maintaining a location information about a subscriber in a HLR and a VLR, correctly. 
     BACKGROUND 
     Generally, a digital mobile communications system using CDMA(Code Division Multiple Access) comprises a home location register(HLR) and a visitor location register(VLR). The HLR has a database for managing extra service information, location information, and etc., about mobile subscribers. The VLR is used by a mobile exchanges to search information which processes a call from/to subscriber visiting area. Accordingly, the HLR should maintain exact information about a plurality of subscribers. And also, the HLR should maintain temporary information in the single VLR only, in which the information is generated according as subscribers move. 
     However, there is no regulation about a concrete situation in a current mobile communications standard(IS-41-C). So, when other mobile network subscribers try to call, it is frequently disconnected because the HLR could not offer subscriber information, correctly. 
     FIG. 1 is a flow chart showing a registration notification(RN) procedure of a normal mobile subscriber. It tells a case that a mobile station(MS 1 ) moves from a previous service system area(where a first visitor location register VLR 1  exists) to a new service system area(where a second visitor location register VLR 2  exists). 
     After the VLR 2  senses the MS 1  and sends a registration notification invoke(RNI) message of the MS 1  to the HLR according as the MS 1  moves(ST 1 ), the HLR updates and saves a location of the MS 1  in database. Here, the VLR 1  has a subscriber record of the MS 1 . The HLR thus requests the VLR 1  to erase location information of the MS 1 (ST 2 ). And then, VLR 1  erases the subscriber record of the MS 1  stored in the current database, and sends a registration cancellation return result(RCRR) message of MS 1  to the HLR(ST 3 ). After receiving the message for erasing location, the HLR sends a registration notification return result(RNRR) message of the MS 1  to the VLR 2 (ST 4 ). Accordingly, the VLR 2  may create a subscriber record of the MS 1  in the database. 
     FIG. 2 is a flow chart showing a call processing procedure of a mobile subscriber. In case that a calling party&#39;s MS requests the desired called party&#39;s mobile station(MS 2 ) to call in which the MS 2  is in other service system area, the FIG. 2 shows the procedure among a calling party&#39;s mobile switching center(MSC) and the HLR and a called party&#39;s mobile switching center(MSC 1 ). 
     When the calling party&#39;s MS requests the MS 2  to call, the corresponding MSC of the calling party&#39;s MS sends a location request (LR) message of the MS 2  to the HLR(ST 11 ). The HLR which received the LR message from the MSC, sends a routing request (RR) message of the MS 2  to a corresponding MSC 1  via VLR 1  of the MS 2  in order to know routing information of the MS 2 (ST 12 ). The called party&#39;s MSC 1  receives the RR message and allocates routing information TLDN(temporary local directory number). At this time, the VLR 1  has a subscriber record of the MS 2 . In case of receiving the TLDN of the MS 2 , the MSC 1  sends a routing request return result(RRRR) message of the MS 2  to the HLR(ST 13 ). The HLR which received the RRRR message sends a location request return result(LRRR) message of the MS 2  to the calling party&#39;s MSC(ST 14 ). 
     Hereinafter, a call processing procedure of a mobile subscriber will be explained in case that the HLR has incorrect location information of the MS 2  with unrecognized reasons. 
     First, the calling party&#39;s MSC sends a location request invoke(LRI) message of the MS 2  to the HLR, showing in below of FIG.  2 (ST 21 ). The HLR sends a routing request (RR) message to the VLR 1  of the MS 2  in order to know location information of the MS 2 (ST 22 ). Here, the VLR 1  does not have the subscriber record of the MS 2 . Accordingly, the VLR 1  sends an error code as well as routing request(RR) error message of the MS 2  to the HLR, in which the error massage indicates that the subscriber can not be recognized(ST 23 ). 
     Here, the HLR clears the subscriber location information stored in the HLR database(ST 24 ). And then the HLR sends a location request return result(LRRR) message with an access denied reason parameter of the MS 2  to the calling party&#39;s MSC. As a result, the call is failed. 
     In case that a mobile station(MS 3 ) moves to a new serving area, location information of the subscriber is registered on at least two VLRs, respectively. And it will be now explained in FIG. 3 showing a registration notification(RN) flowchart of a mobile subscriber. 
     When a mobile station(MS 3 ) moves to a new serving area, the VLR 2  in a new serving area senses the MS 3  and requests the HLR a first registration notification invoke(RNI) of the MS 3 (ST 1 ). The HLR updates the location of the MS 3  and stores a previous location on database. Here, the VLR 1  still has the subscriber record of the MS 3 . Accordingly, the HLR requests the VLR 1  registration cancellation(RC)of the MS 3 (ST 2 ). 
     But, in case that the VLR 2  requests the HLR a second RNI(ST 3 ), the HLR answers about a registration notification request(RNR) without any registration cancellation(RC) procedure because it&#39;s from a current service system, again. Accordingly, the HLR sends a second registration notification return result(RNRR) message of the MS 3  to the VLR 2 (ST 4 ). Consequently, a subscriber record of the MS 3  is created in the VLR 2 . 
     Besides, in case that a registration cancellation request(RCR) of the MS 3  requested by the HLR to the VLR 1 , is not carried out because the MS 3  is busy, and etc., the VLR 1  sends a registration cancellation return result(RCRR) message with a cancellation denied parameter to the HLR(ST 5 ). Because the RCR of the MS 3  is denied, the HLR restores a location information of the database and sends a first RNRR message with an access denied reason parameter to the VLR 2  in order to re-register the location of the MS 3  in the VLR 1  where the previous service system is provided (ST 6 ). 
     The HLR is operated in the same way when the answering information is lost in the step (ST 2  or ST 5 ). Even though a first registration notification(RN) of the MS 3  failed, the database of the VLR 2  already has the subscriber record of the MS 3  by requesting the second RN(ST 3 ) and also, the subscriber record which established in the database of the VLR 1 , was not canceled. Consequently, both visitor location registers VLR 1 , VLR 2  have a subscriber record of the MS 3 . 
     Like this way, when the other mobile subscriber tries to call, the HLR can not carry out a normal call processing because the HLR and VLR have incorrect information about a corresponding subscriber. 
     FIG. 4 shows a signal processing flowchart for explaining errors. The errors may be happened in case that a registration notification(RN) and call processing procedures about same mobile subscriber are overlapped showing in FIG. 1 to FIG. 2, when a mobile station(MS 4 ) moves to another serving area. 
     In case that the MS 4  moves to a new serving area, a VLR 2  senses the MS 4  and requests a registration notification invoke(RNI) to the HLR(ST 31 ). The HLR updates the location of the MS 4  and stores the previous location in database. The VLR 1  has a subscriber record of the MS 4 . And then the HLR requests the VLR 1  a registration cancellation(RC)of the MS 4 (ST 32 ). Therefore the VLR 1  erases the subscriber record of the MS 4 . 
     Here, when the subscriber record of the MS 4  is normally erased in the VLR 1 , the VLR 1  sends a registration cancellation return result(RCRR) message to the HLR(ST 38 ), in which the message tells that the subscriber record of the MS 4  is erased. The HLR finally sends a registration notification return result(RNRR) message which requested by the VLR 2 , to the VLR 2 (ST 39 ). And the VLR 2  creates the subscriber record of the MS 4  in the database. 
     But, there is a situation that a location request (LR) message of the same MS 4  above is sent from a mobile switching center(MSC) which does not request a registration notification(RN) before the RN requested from the VLR 2  is not completed normally(ST 33 ). In above situation, the HLR tries to receive a temporary local directory number(TLDN) by sending a routing request(RR) message to a new service system(ST 34 ), because the location information of a corresponding subscriber, which is stored in the HLR database, is already updated to the information of a new service system. But, the VLR 2  does not have the subscriber record of the corresponding MS 4  because the RN of the MS 4  is processing in the current new service system. Accordingly, the VLR 2  sends the RR error message of the MS 4  to the HLR as an answer of the RR(ST 35 ). And then, the HLR, received the error message, clears the subscriber location information of the MS 4  of the database(ST 36 ). The HLR then sends the location request return result(LRRR) message to the MSC(ST 37 ). 
     Here, there is another situation that a location request invoke(LR) message of the MS 4  is sent from a MSC to the HLR by called signal request of the same MS 4  above(ST 40 ). In this case, the HLR has already cleared the location information of the MS 4  by receiving the routing request(RR) error message in the step(ST 36 ). Consequently, the HLR does not have the subscriber location information of the MS 4 . Accordingly, the call is failed by sending the location request return result(LRRR) message with access denied reason of the MS 4  to the corresponding MSC where requested the location information(ST 41 ). 
     Additionally, the VLR 1  sends the registration notification invoke(RNI) message of the MS 4  to the HLR in case that the MS 4  moves to another serving area (explained by drawings as an example, the MS 4  moves to an area where the VLRL manages)(ST 42 ). 
     But, because the subscriber location information of the MS 4  is already cleared in the HLR database, the registration cancellation(RC)is not requested to the VLR 2  of the previous serving area. And by sending the registration notification return result(RNRR) message of the MS 4  to the VLRL (ST 43 ), the VLRL creates a subscriber record of the MS 4  in the VLR 1  database. 
     The VLR 2  already has the subscriber record of the MS 4 , therefore does not request the registration notification(RN) to the HLR in case that the MS 4  moves to a serving area where has a current subscriber record(explained by drawing as an example, the MS 4  moves to an area where the VLR 2  manages). Accordingly, it is easy to fail when the other mobile subscriber try to call because the HLR is managing an incorrect subscriber location information of the MS 4 . 
     In above case, there is no way that a user of the corresponding mobile station(MS) can check the reason of disconnection except calling to a mobile communications company. And a VLR operator should select and erase useless subscriber records in the VLR database. But, the way to solve like above is not the essential solution and there are possibilities that the same problem happens successively. 
     SUMMARY 
     Thus taking the above-mentioned problems into consideration, a first objective of the present invention is to solve the problems in method for managing subscriber location information in a mobile communications system, as described above, by maintaining correctly temporary information of the same subscriber in a single VLR only by a HLR, when two VLRs request the HLR registration notification as overlapped, in case that a mobile station moves from a previous serving area to other area. 
     A second objective of the present invention is to provide a method for managing subscriber location information in a mobile communications system, in which a HLR maintains currently a correct location of a corresponding subscriber when a registration notification(RN) and call processing procedure of the same subscriber are happened by overlapped. 
     According to an embodiment to achieve the first object of the present invention, a method for managing subscriber location information in a mobile communications system, comprising processes of carrying out a corresponding registration notification(RN) of a mobile station(MS) in a HLR and indicating that the registration notification(RN) is processing when the MS moves to a previous serving area, and preventing multi-location registrations about a same subscriber during handling a registration notification(RN). 
     According to another embodiment to achieve the first object of the present invention, a method for managing subscriber location information in a mobile communications system, comprising processes of carrying out a corresponding registration notification(RN) of a MS in a HLR and in a corresponding VLR that the registration notification(RN) is processing when the MS moves to a new serving area, and preventing multi-location registrations about a same subscriber during handling a registration notification(RN). 
     According to the other embodiment to achieve the second object of the present invention, a method for managing subscriber location information in a mobile communications system, comprising processes of carrying out a corresponding registration notification(RN) of a MS in a HLR and indicating that the registration notification(RN) is processing when the MS moves to a new serving area and ignoring multi-location registration signals about a same subscriber and a call processing signal from an exchange during registering the location until a previous registration notification(RN) is erased. 
     According to a 4th embodiment to achieve the second object of the present invention, a method for managing subscriber location information in a mobile communications system, comprising processes of carrying out a corresponding registration notification(RN) of a MS in a HLR and indicating in a corresponding VLR that the registration notification(RN) is processing when the MS moves to an area where a new service system is provided, and ignoring multi-location registration signals about a same subscriber and a call processing signal from an exchange during registering the location until a previous registration notification(RN) is erased. 
    
    
     BRIEF DESCRIPTION 
     The invention and its modes of use and advantages are best understood by reference to the following description of illustrative embodiments when read in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a flowchart showing a registration notification procedure of a mobile subscriber, 
     FIG. 2 is a flowchart showing a call processing procedure of a mobile subscriber, 
     FIG. 3 is a flowchart explaining an error that location information of a mobile subscriber is registered by overlapped in two more VLRs, respectively, 
     FIG. 4 is a flowchart explaining an error which may be generated when a registration notification and a call processing procedure are carried out by overlapped about the same mobile subscriber of FIG. 1 to FIG. 2, 
     FIG. 5 is a flowchart showing one embodiment of the present invention for preventing the error of the FIG. 3, 
     FIG. 6 is a flowchart explaining a procedure for preventing a misoperation which may be happened again in the embodiment of FIG. 5, 
     FIG. 7 is a flowchart showing another embodiment of the present invention for preventing the error of the FIG.4, 
     FIG. 8 is a flowchart explaining a procedure for preventing a misoperation which may be happened again in the embodiment of FIG. 7, and 
     FIG. 9 is a flowchart showing the other embodiment of the present invention for maintaining a correct location information in a HLR and a VLR during registration notification process of a mobile subscriber. 
    
    
     DETAILED DESCRIPTION 
     The method of the present invention will be described in detail with reference to FIGS. 5 to  9  according to each embodiment of the present invention. 
     FIG. 5 is a flowchart explaining method for managing a subscriber location information in a mobile communications system according to one embodiment of the present invention. It prevents location information of a mobile subscriber from being registered in two more VLRs, respectively, in case that a MS 5  moves from a previous serving area, to a new serving area. 
     In the figure, a MS 5  moves from a previous serving area to a new serving area. A corresponding visitor location register(hereinafter, a second visitor register is referred to VLR 2 ) of the new serving area senses the MS 5  and sends a first registration notification (invoke RNI) message of the MS 5  to the HLR(ST 11 ). The HLR updates the location of the MS 5  and stores the previous location in database. Here, the previous visitor location register(hereinafter, a first visitor location register is referred to VLR 1 ) has a subscriber record of the MS 5 . Accordingly, the HLR receives a registration notification invoke(RNI) message and sets a registration notification pending flag(RNPF) of the MS 5  to “1” until the registration notification(RN) is completed, in which the flag is formed in the HLR database. And the HLR sends a registration cancellation return result (RCRR) message of the MS 5  to the VLR 1 (ST 13 ). Here, a state that the HLR is now carrying out the registration notification(RN) of the MS 5  is indicated, in which the state is that the registration notification pending flag(RNPF) is set as “1”. Accordingly, the HLR is processed as errors which are generated before the registration notification pending flag(RNPF) bit value of the MS 5  is changed “1” about all additional return result(RCRR). 
     The HLR sends an error to VLR 2  for a second registration notification return result(RNRR) because the registration notification pending flag(RNPF) bit value of the MS 5  in its database is set as “1”. As a result, a subscriber record of the MS 5  is not created in the VLR 2 . 
     Besides, the VLR 1  sends a registration cancellation return result(RCRR) with cancellation denied parameter or error message of the MS 5  to the HLR when the registration cancellation return result(RNRR) of the MS 5 , which is requested from the HLR to the VLR 1 , is not carried out with some reasons, in such a case of a MS is busy, and so on(ST 17 ). Accordingly, the HLR receives the registration cancellation return result(RCRR) with cancellation denied or error message of the MS 5  and changes the registration notification pending flag(RNPF) bit value to “0”. And then the HLR sends a first registration notification return result(RNRR) message of the MS 5  to the VLR 2 (ST 19 ). As a result, a subscriber record is not created in the VLR 2 . 
     The HLR processes the meaningful registration notification (invoke RNI) message only, even though the VLR 2  requests the registration notification(RN), overlapped in the same MS Therefore, the HLR and the VLR 1  and the VLR 2  can always maintain the location information of a MS, correctly. 
     FIG. 6 is an operational flowchart for preventing that the HLR has errors for managing the flag. 
     When a registration notification pending flag(RNPF) stored in the HLR database is maintained as “1” by the errors(ST 21 ) in FIG.  6 . And the VLR 2  sends a first registration notification invoke(RNI)-message of the MS 6  to the HLR by sensing the MS 6  in case that a MS 6  moves from a previous serving area, to other new serving area. At this time, the registration notification pending flag(RNPF) of the current database is set as “1”. So the HLR compares a latest registration notification time of the MS 6  with a current time in order to determine whether the registration notification(RN) is carrying out or is a bit value set by an error. After comparing, the HLR determines that the registration notification(RN) is carrying out the operation and maintains the registration notification pending flag(RNPF) and processes the registration notification invoke(RNI) generated right before to error, in case that a predetermined constant time is not over (explained that the time is set by 6 seconds in the embodiment). Otherwise, the HLR determines that the flag management has an error, resets the registration notification pending flag(RNPF) and normally takes the registration notification invoke(RNI) generated right before, in case that predetermined constant time is over(ST 23 ). And then, the HLR updates the location information of the MS 6  and stores the previous location in the database. At this time, the VLR 1  has a subscriber record of the MS 6 . Accordingly, the HLR sets the registration notification pending flag(RNPF) bit value, which is in the HLR database, to “1” until the registration notification(RN) operation is completed. And the HLR sends the registration cancellation return result(RCRR) message of the MS 6  to the VLR 1 (ST 25 ). Here, in case that the registration notification pending flag(RNPF) is set as “1”, all additional registration notification invoke(RNI) messages are processed as an error before the registration notification pending flag(RNPF) value is changed to “0”. 
     But, there is a case that the VLR 2  sends a second registration notification invoke(RNI) message to the HLR by a particular reason(ST 26 ). The HLR processes the second requested registration notification(RN) message as an error(ST 27 ) and then sends the second registration notification return result(RNRR) return with error message of the MS 6  to the VLR 2 (ST 28 ) because the registration notification pending flag(RNPF) bit value which is in the database, is set as “1”. Accordingly, a subscriber record of the MS 6  is not created in the VLR 2 . 
     Besides, the VLR 1  sends a registration cancellation return result(RCRR) message of the MS 6  to the HLR(ST 29 ) when the registration cancellation invoke of the MS 6  is refused because the MS is busy, and so on. The registration cancellation invoke(RCI) of the MS 6  was required from the HLR to the VLR 1 . The HLR therefore changes the registration notification pending flag(RNPF) bit value to “0” in order to notice that the current registration notification(RN) is completed, in case of receiving the registration cancellation return result(RCRR) message of the MS 6 . The HLR sends a first registration notification return result(RNRR) message of the MS 6  to the VLR 2 (ST 31 ). As a result, a subscriber record of the MS 6  is not created in the VLR 2 . 
     FIG. 7 is a flowchart according to the other embodiment of the present invention. It shows how to prevent the same mobile subscriber from being remained in two more VLRs when a registration notification(RN) procedure and the call processing procedure about the same mobile subscriber is overlapped. 
     The new serving VLR 2 , senses the MS 7  and requests a registration notification invoke(RNI) to the HLR(ST 51 ), in case that the MS 7  moves to other new serving area. The HLR updates the location information of the MS 7  and store a previous location information in the database. And the VLR 1  has the subscriber record of the MS 7 . As a result, the HLR sets a registration notification pending flag(RNPF) bit value which is in the HLR database as “1” until a registration notification(RN) is completed(ST 52 ). And the HLR indicates that the registration notification(RN) is carrying out the operation sends a registration cancellation return result(RCRR) message of the MS 7  to the VLRL (ST 53 ). 
     There is a case that a location message about the same MS 7  is sent from another MSC to the HLR(ST 54 ), in which the MSC does not request the registration notification(RN), before the requested registration notification(RN) is normally completed. In this case, a subscriber location information stored in the HLR database is already changed to a new service system. Therefore, the HLR sends a routing request message to the new service system and tries to receive the TLDN(ST 55 ). 
     But, the VLR 2  does not have a subscriber record of the corresponding MS 7  because the registration notification(RN) requested from the new service system, is in process. Accordingly, the VLR 2  sends a routing request(RR) error message(indicating an unrecognized MIN) of the MS 7  as a return error about the routing request(RR) message to the HLR(ST 56 ). 
     The HLR does not clear the location information of the MS 7  because the current registration notification pending flag(RNPF) bit value is “1” after receiving an error message about the routing request invoke(RRI)(ST 57 ). And then, the HLR sends a return result message of the location request to the MSC(ST 58 ), the call is failed. After sending a registration cancellation return result(RCRR) from the VLR 1  to the HLR, the HLR changes the registration notification pending flag(RNPF) bit value to “0” and indicates that the registration notification(RN) is completed, and sends the return result message as well as subscriber profile information to the VLR 2 , in which the registration notification pending flag(RNPF) is in the HLR database. As a result, a subscriber record of the MS 7  is created in the VLR 2 (ST 60 ). 
     At this time, there is a case that a location request message of the MS 7  is sent from other mobile exchanges(not showing in the figure) to the HLR, by that a called signal request of the same MS 7  is created, shown in below of FIG.  7 (ST 61 ). In this case, the HLR has the location information of the MS 7  because the HLR did not clear the location information about the MS 7  of the HLR database in the step(ST 57 ). Accordingly, in case that the HLR sends the routing request message to the VLR 2  in order to know the location information of the MS 7 (ST 62 ), the VLR 2  sends a routing request return result(RRRR) message of the MS 7  to the HLR(ST 63 ). 
     Additionally, the VLR 1  sends the registration notification invoke(RNRR) message of the MS 7 (ST 65 ), in case that the MS 7  moves to a previous serving area(or the other service system, this embodiment is explained when the MS 7  moves again to the previous serving area). The HLR did not clear the subscriber location information stored in the database. Therefore, the HLR sends the registration cancellation (invoke RCI) message of the MS 7  to the VLR 2 (ST 66 ) and the VLR 2  erases the subscriber record of the MS 7  stored in the VLR 2  database and sends a corresponding registration cancellation return result(RCRR) message to the HLR(ST 67 ). Accordingly, the HLR sends the registration notification return result (RNRR) message of the MS 7  to the VLR 1 (ST 68 ). As a result, the VLRL creates a subscriber record of the MS 7 . 
     Accordingly, location information of the current MS 7  may be correctly maintained in the HLR and single VLR only(VLR 1  or VLR 2 ). 
     FIG. 8 shows a flowchart explaining how to prevent a flag management misoperation during operation of preventing an error generation in case that a registration notification(RN) and call processing procedures are overlapped of FIG.  7 . 
     There is a case that a MSC sends the location request message of a MS 8  to the HLR when the HLR registration notification pending flag(RNPF) is maintained as “1” with unknown reasons(ST 71 ). The HLR sends a routing request message of the MS 8  to the VLR 2 (ST 73 ). But the VLR 2  does not have a subscriber record of the MS 8 . The VLR 2  sends a routing request return result(RRRR) error message of the MS 8  to the HLR(ST 74 ). The registration notification pending flag(RNPF) bit value in the HLR database is “1”. Accordingly, the HLR examines whether the latest registration time is passed over the predetermined constant time(6 seconds) by comparing the latest registration time of the MS 8  with current time. After passed over the constant time, the HLR clears the subscriber location information stored in the HLR database(ST 75 ) and sends the location request return result(LRRR) message of the MS 8  to the MSC(ST 76 ). 
     Here, the HLR sends the location request return result(LRRR) message to the MSC where sends the location request message in case that the other MSCs (not showing in FIG.) send the location request message of the MS 8  to the HLR(ST 77 ), in which the location request return result(LRRR) message tells that there is no routing information of the MS 8 . 
     Additionally, in case that the MS 8  moves to the previous serving area, the VLR 1  of the corresponding area sends a registration notification message of the MS 8 (ST 79 ). And the HLR stores the subscriber location information of the MS 8  in database sends the registration notification return result(RNI) message to the VLR 1  without requesting the registration cancellation(RC) of other VLR(ST 80 ). As a result, the VLR 1  creates a subscriber record of the MS 8 . 
     FIG. 9 is a flowchart explaining a method for managing a subscriber location information. It shows that a registration notification pending flag(RNPF) set/reset and error generation preventing operation using the pending flag set/reset which are accomplished in the HLR in each embodiment above, are accomplished in a VLR. It tells that the HLR and a previous visitor location register(VLR 1 ) and the current visitor location register(VLR 2 ) maintains correct location information during a registration notification(RN) of a mobile station(MS 9 ). It is understood that each embodiment shown in FIG. 5 to FIG. 8 explains a below operation. 
     As shown in FIG. 9, the corresponding VLR 2  senses the MS 9 (ST 91 ), sets the registration notification pending flag(RNPF) as “1” (ST 92 ) and sends a registration notification invoke(RNI) message of the MS 9  to the HLR(ST 93 ) in case that the MS 9  moves from a previous serving area to other new serving area. Here, the VLR 1  has a subscriber record of the MS 9  and the HLR updates the location of the MS 9  and stores a previous location of the MS 9 . 
     And then, the HLR recognizes that the location of the MS 9  is changed, therefore sends a registration cancellation return result(RCRR) message to the VLR 1 (ST 94 ) and waits for answering that. The HLR sends a routing request message to the VLR 2  in case that a mobile switching center(MSC) requests the location of the MS 9  during the answering waiting state(ST 95 , ST 96 ). 
     But, the VLR 2  does not have a subscriber record in the database because of not receiving an answer about the current registration notification(RN). Additionally, the VLR 2  registration notification pending flag(RNPF) is set as “1”. 
     Accordingly, the VLR 2  sends “operator sequence problem error” message besides “recognized MIN error” message as a routing request return result(RRRR) of the MS 9 (ST 97 ). Therefore, the HLR does not clear subscriber information and sends the location request return result(LRRR) to the MSC(ST 98 ). As a result, the HLR may maintain a correct subscriber information. 
     As following, when the HLR receives the registration cancellation return result (RCRR) message of the MS 9  from the VLR 1 (ST 99 ), the HLR sends a registration notification return result(RNRR) message of the registration cancellation return result(RCRR) to the VLR 2 (ST 100 ). In this case, the VLR 2  creates a subscriber record of the MS 9  in the database and changes the registration notification pending flag(RNPF) as “0”(ST 101 ). As a result, the VLR 2  indicates the registration notification completion and helps that another registration notification(RN) and call processing is normally carried out. 
     As described above, when a mobile subscriber moves from a previous serving area to a new serving area, the HLR may maintain a current location information only of subscriber even though single VLR requests the registration notification(RN) of single MS by overlapped(or two VLR request the registration notification(RN), respectively). 
     Additionally, the present invention may maintain temporary information of the same subscriber in signal VLR as well as a current location of subscriber in HLR correctly in case that the registration notification(RN) and call processing procedure of the same subscriber are overlapped. Therefore, it can be improved reliability about a call connection in a mobile communications system. 
     The previous description of the preferred embodiments are provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without the use of the inventive faculty. Thus, the present invention is not intended to be limited to the embodiment herein, but is to be accorded the widest scope consistent with the principles as novel features disclosed herein.