Patent Publication Number: US-2011053594-A1

Title: Apparatus and method for location  management of user equipment in generic access network

Description:
FIELD OF THE INVENTION 
     The present invention relates to a technology for location management of a user equipment (UE) in a mobile communication system and, more particularly, to an apparatus and method for location management of a UE in a generic access network, which are suitable to efficiently carry out location management of a mobile UE in the generic access network to reduce power consumption of the UE. 
     BACKGROUND OF THE INVENTION 
     As well-known in the art, third generation partnership project (3GPP) standardized the generic access network (GAN) technology in which voice and data services performed by a mobile communication network are provided to a UE over an IP network. The GAN is a technology that can interwork with any networks supporting IP connection, which is also widely known as unlicensed mobile access (UMA). 
       FIG. 1  is an exemplary model of network structure to which the GAN technology is applied in accordance with a related art. 
     Referring to  FIG. 1 , a generic access network controller (GANC)  106 , which serves as a base station controller (BSC) or radio network controller (RNC) of an existing mobile communication network, plays the role of providing voice services and data services of the mobile communication network over a general IP network. Moreover, a variety of radio access networks, such as wireless local area network (WLAN)  110 , Bluetooth  112 , and world interoperability for microwave access (WiMAX)  114 , are routed to the generic IP access network  108  and then finally interwork with the mobile communication network through the GANC  106 . 
     The GANC  106  provides services such as voice calls and text messages through a mobile switching center (MSC)  102  of a core network (CN)  100 , and provides packet data services through a serving general packet radio service (GPRS) support node (SGSN)  104 . A user equipment (UE)  116 , which may be referred to as a mobile station (MS), subscriber unit (SU), access terminal (AT), and so on in various technologies, first has to search for the GANC  106  in order to get a circuit switching (CS) service provided through the GANC  106 , and carries out a registration process by sending a Generic Access-Radio Resource Control (GA-RRC) REGISTER REQUEST message to the GANC  106 . 
     Specifically, the GANC  106  manages a point of attachment (PoA), to which the UE  116  is connected, and, when there is a change in the PoA, allows the UE  116  to transmit a GA-RRC REGISTER UPDATE message to the GANC  106  to perform the update of location information. The UE  116  is able to use voice and data services under a connected state (GA-RRC-CONNECTED) to the GANC  106 , and the UE  116  is switched to an idle (GA-RRC-IDLE) mode when the services are not available for a predetermined period of time. 
     Meanwhile, the mobile communication network employs a power saving mechanism for efficient power consumption of a terminal in the idle mode. For instance, a universal mobile telecommunications system (UMTS) tracks the location of a UE in three areas including a location area (LA), a routing area (RA), and an UMTS radio access network (UTRAN) registration area (URA). The LA for CS service is a range in which the MSC tracks the location of a UE in an idle mode. The RA for packet switching (PS) service is an area in which the SGSN tracks the position of the UE in an idle mode. The URA is employed in the UTRAN to track the position of a UE. 
       FIG. 2  illustrates the relationship among an LA, an RA, and an URA in an UMTS in accordance with a related art. 
     Referring to  FIG. 2 , a URA is a set of cells or base stations, and an RA includes one or more URAs. As such, multiple RAs can exist under one RNC. Also, the LA may generally include one or more RAs. 
     Therefore, when a UE is in an idle mode in a CS domain, even if a cell to which the UE is connected is changed, the UE does not update its location to the MSC as long as the LA is not changed, thereby reducing power consumption. At this point, if it is required to provide a CS service to the UE in the idle mode (e.g., if a call is coming in), the MSC transmits a paging message to all cells in the LA to which the UE belongs, and the UE receiving such a paging message sends a response message to notify of its location. Location tracking for the UE in a PS domain is performed similarly to that of the CS domain, wherein a paging message is transmitted based on RA and URA rather than based on LA. 
     In the UMTS as set forth above, base stations within a certain region are grouped together into one RA, and the location of a UE that has entered the idle mode is tracked for each RA or for each LA including one or more RAs. That is, even if the UE in the idle mode changes a serving base station to another, the UE in the idle mode does not update its location as long as the RA or the LA is not changed, thereby reducing power consumption. 
     However, the GAN standard defines that the UE has to perform a register update process to the GANC each time the UE changes its PoA. Therefore, even if the UE is in the idle mode, it has to send a REGISTER UPDATE message to the GANC when there is a change in PoA. Such an instant register update process allows the GANC to correctly forward a GA-RRC PAGING REQUEST message to the corresponding PoA, but has the problem of increase in the power consumption of the UE in the case of frequent changes in PoA. 
     SUMMARY OF THE INVENTION 
     Therefore, a primary object of the present invention is to provide an apparatus and method for location management of a user equipment in a generic access network capable of reducing power consumption of the user equipment. 
     In accordance with a first aspect of the present invention, there is provided an apparatus for location management of user equipments (UEs) in a generic access network (GAN), which includes: 
     apparatus for location management of user equipments (UEs) in a generic access network (GAN), the apparatus comprising: 
     a UE adapted for transmitting a register request message containing an ID of a current point of attachment (PoA) to which the UE is currently connected, checking the information on GAN paging area (GPA) received in response to the register request, wherein the information on the GPA includes IDs of one or more points of attachment (PoAs) within a GPA to which the PoA where the terminal is located belongs, and transmitting a register update message to the GAN when moving to another PoA that is not included in the information of the GPA; and 
     a generic access network controller (GANC) adapted for identifying the location of the UE based on an ID of the current PoA transmitted by the UE, and transmitting a register accept message containing the information on the GPA to the UE that made the register request. 
     In accordance with a second aspect of the present invention, there is provided a method for location management of a user equipment (UE) in a generic access network (GAN), the method comprising: 
     configuring one or more points of attachment (PoAs) for each GAN paging area (GPA); 
     identifying the location of the UE based on an ID of the current PoA contained in a register request message transmitted by the UE; 
     transmitting a register accept message containing information about the one or more PoAs of the GPA to the UE that made the register request; and 
     upon receipt of a paging message requested from a mobile switching center (MSC) or serving general packet radio service (CPRS) support node (SGSN) to the UE, transmitting a paging request message to all the PoAs of the GPA. 
     In accordance with a third aspect of the present invention, there is provided a method for location management of a UE in a generic access network (GAN), the method comprising: 
     transmitting register request information containing ID information corresponding to a PoA where the UE is currently located to a generic access network controller (GANC); 
     storing the register accept message transmitted from the GANC, wherein the register accept message contains information of each GPA paging area (GPA) having one or more PoAs; and 
     performing a location register update procedure with the GANC when moving to a PoA that is not contained in the GPA. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects and features of the present invention will become apparent from the following description of embodiments, given in conjunction with the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
         FIG. 1  is an exemplary model of network structure to which a general GAN technology is applied in accordance with a related art; 
         FIG. 2  illustrates the relationship among an LA, an RA, and an URA in a UMTS in accordance with a related art; 
         FIG. 3  illustrates a register update operation in a GAN when a UE moves; 
         FIG. 4  illustrates an operation when a call comes in from a UE in a GAN; 
         FIG. 5  illustrates an operation for receiving data service in the GAN; 
         FIG. 6  illustrates an operation in which a GANC forwards GPA (GAN paging area) information to the UE during a GAN registration process in accordance with an embodiment of the present invention; 
         FIG. 7  illustrates a register update operation performed when the UE moves in the GAN in accordance with an embodiment of the present invention; and 
         FIG. 8  illustrates a paging procedure performed in the GAN in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, the embodiments of the present invention will be described in detail with reference to the accompanying drawings which forms a part thereof. 
     Although, between two modes of a GAN: the A/Gb mode which is an interface between a user equipment and a base station; and the Iu mode which is an interface between a user equipment and an UMTS radio access network (UTRAN), the embodiments of the present invention will be described hereinafter based on the Iu mode, it should be understood that the embodiments are applicable in the same manner to the A/Gb mode. 
       FIG. 3  illustrates a register update operation in a generic access network (GAN) when a user equipment (UE) moves. 
     Referring to  FIG. 3 , a UE  302 , which is initially connected to the location of a PoA 1   304 , sends a generic access-resource control (GA-RC) REGISTER REQUEST message to a GANC  300  through a generic IP access network  318  to carry out registration, and then sends a GA-RC REGISTER UPDATE message, to each PoA through a generic IP access network  318  to notify the GANC  300  of the location of each PoA while moving PoAs. That is, the UE  302  transmits a GA-RC REGISTER UPDATE message to the GANC  300  each time it moves from the PoA 1   304  to a PoA 2   306 , a POA 3   308 , a PoA 4   310 , and a PoA 5   312 . 
       FIG. 4  illustrates an operation when a call comes in from the UE in the GAN. 
     In  FIG. 4 , a GANC  402  performs the same function as the RNC of an UMTS. Therefore, if the GANC  402  is positioned in a location area (LA) of a UE  400 , a paging message sent from a mobile switching center (MSC)  404  arrives at the GANC  402  in step  406 . By the way, as explained above, the UE  400  needs to send a REGISTER UPDATE message to the GANC  402  each time its POA is changed, so the GANC  402  is aware of the correct PoA to which the UE  400  is currently connected. 
     Therefore, the GANC  402 , which has received the paging message from the MSC  404 , sends a GA-RRC PAGING REQUEST message only to the PoA where the UE  400  is located in step  408 , and the UE  400  that has received the GA-RRC PAGING REQUEST message transmitted to the corresponding PoA response with a GA-RRC INITIAL DIRECT TRANSFER message containing a PAGING RESPONSE message to the GANC  402  in step  410 . At this point, the UE  400  is switched to a GA-RRC-CONNECTED state in step  412 , and the GANC  402  forwards an initial UE message containing the PAGING RESPONSE message received from the UE  400  to the MSC  404  in step  414  so as to perform the subsequent processes for call setup. 
     In the subsequent process for call setup, an authentication procedure among the MSC  404 , the GANC  402 , and the UE  400  is performed in step s 416 , the control of the security mode is performed in step  418 , and then the MSC  404  forwards a GA-RRC DL DIRECT TRANSFER message containing a setup message to the UE  400  via the GANC  402  in step  420 . Then, the UE  400  forwards a GA-RRC UL DIRECT TRANSFER message containing a call confirmed message to the MSC  404  via the GANC  402  in step  422 . 
     Thereafter, a bearer establishment procedure for wireless connection among the MSC  404 , the GANC  402 , and the UE  400  is performed in step  424 , the uE  400  transmits a GA-RRC UL DIRECT TRANSFER message containing an Alerting message to the MSC  404  in step  426 , and then transmits a GA-RRC UL DIRECT TRANSFER message containing a Connect message to the MSC  404  step  428 . 
     Then, the MSC  404  transmits a GA-RRC DL DIRECT TRANSFER message containing a Connect Ack message to the UE  400  in step  430  to perform connection and establish a bearer channel, and the UE  400  receives voice traffic transmitted from the bearer channel established by the MSC  404  in step  432 . 
       FIG. 5  illustrates an operation for getting data service in the GAN. 
     Referring to  FIG. 5 , upon receipt of downlink data towards the UE  500  in a GA-RRC-IDLE state, an SGSN  504  transmits a Paging message to the GANC  502  in step  506 , the GANC  502  transfers a GA-RRC PAGING REQUEST message only to the PoA where the corresponding UE  500  is located in step  508 , and the UE  500  that has received the GA-RRC PAGING REQUEST message transmitted to the corresponding PoA sends a GA-RRC INITIAL DIRECT TRANSFER message containing a Paging Response message to the GANC  502  in step  510 . 
     The UE  500  is then switched to the GA-RRC-CONNECTED state in step  512 , and the GANC  502  forwards an Initial UE message containing the Paging Response message received from the UE  400  to the SGSN  504  in step  514  so as to perform the subsequent process for data transmission and reception. 
     In the subsequent process for data transmission and reception, an authentication procedure among the SGSN  504 , the GANC  502 , and the UE  500  is performed in step  516 , the control of the security mode is performed in step  518 , and then a packet transport channel (PTC) is activated in step  520 . Consequently, in step  522 , downlink data transmitted from the SGSN  504  is transmitted to the UE  500  through the packet transport channel activated between the GANC  502  and the UE  500 . 
     As described with reference to  FIGS. 4 and 5 , such an instant register update operation performed in the GAN allows the GANCs  402  and  502  to correctly forward a GA-RRC PAGING REQUEST message to the corresponding PoA. However, in the case of frequent changes in PoA, power consumption of the UEs  400  and  500  may be increased. 
     Now, a description will be given on a method for reducing power consumption of a UE in the GAN. 
     In the embodiment of the present invention, the following operations are additionally defined for the basic operation of a UE performed in GANC and GAN. The GANC has a list of access point IDs (hereinafter referred to as AP-IDs) of PoAs from which the GANC permits access. Also, geographically adjacent PoAs are grouped into a GAN paging area (hereinafter referred to as GPA). In this regard, PoAs operating on different access technologies may belong to one GPA. 
       FIG. 6  illustrates an operation in which a GANC forwards information about GPA to the UE during a GAN registration process in accordance with an embodiment of the present invention. 
     According to the embodiment of the invention, rather than newly defining a message for GPA information forwarding, a message defined in the GAN standard is extended as follows. That is, in the GAN standard, a UE  600  transmits a GA-RC REGISTER REQUEST message containing information such as the AP-ID of the current PoA to a GANC  602  in the location registration process of step  604 , and, upon receipt of it, the GANC  602  transmits a GA-RC REGISTER ACCEPT message to the UE  600 . 
     The GA-RC REGISTER ACCEPT message contains a plurality of system information. For instance, a GPA information field  608  can be additionally included in the GA-RC REGISTER ACCEPT message. The GPA information field  608  has a structure in which IDs of GPAs (hereinafter referred to as GPA-IDs) are listed, followed by the AP-IDs of the PoAs belonging to a corresponding GPA. With this, the UE  600  becomes aware of which GPA each PoA belongs in the registration process. Also, the GANC  602  becomes aware of the GPA to which the UE  600  currently belongs based on the AP-ID contained in the GA-RC REGISTER REQUEST message. 
     After that, when the UE  600  in the GA-RRC-IDLE state changes its PoA, it checks whether the AP-ID of the PoA to which the UE  600  is newly connected is contained in the GPA information field  608  received from the GANC  602 . If not, the UE  600  sends a register update message to the GANC  602  for the purpose of a location register update procedure. 
     However, if the AP-ID of the PoA to which the UE  600  is newly connected is contained in the GPA information field  608  received from the GANC  602 , it is checked whether both the new PoA and the previous PoA belong to the same GPA. If the new PoA and the previous PoA belong to the same GPA, the UE  600  does not need to take any action while keeping the existing condition. On the contrary, if the new PoA and the preceding PoA do not belong to the same GPA, the UE  600  transmits a register update message to the GANC  602 . In conclusion, as long as a new PoA belongs to the same GPA, a change in PoA does not require for the UE  600  to send a register update message, thereby reducing power consumption from a point of the UE  600 . 
       FIG. 7  illustrates a register update operation when the UE moves in the GAN in accordance with an embodiment of the present invention. 
     Referring to  FIG. 7 , for example, a PoA 1   704 , a PoA 2   706 , and a PoA 3   708  belong to GPA 1 , and a PoA 4   710  and a PoA 5   712  belong to GPA 2 . A UE  702 , which is currently connected to the location of the PoA 1   704 , sends a GA-RC REGISTER REQUEST message containing information, such as the AP-ID of the current PoA 1   704 , to a GANC  700  through a generic IP access network  718 . Then, the GANC  700  sends a GA-RC REGISTER ACCEPT message to the UE  702  through a generic IP access network  718  to perform registration of the UE. 
     In this case, the GA-RC REGISTER ACCEPT message received by the UE  702  includes GPA information (e.g., information about only GPA 1  containing the PoA of the UE  702  or information about all GPAs, i.e., GPA 1  and GPA 2 , that are managed by the GANC  700 ). Since the GPA information is stored in the UE  702 , the UE  70  becomes aware that information on the PoA 1   704 , PoA 2   706 , and PoA 3   708  is included in GPA 1 . 
     Accordingly, when the UE  702  in the idle mode moves between PoAs, for example, from the PoA 1   704  to the PoA 2   706  or to the PoA 3   708 , the UE  702  does not need to send a GA-RC REGISTER UPDATE message to the GANC  700 , thereby maintaining the idle mode. 
     However, if the UE  702  moves from the position of PoA  704 ,  706 , or  708  belonging to GPA 1  to the location of the PoA 4   710  belongs to GPA 2 , the UE  702  transmits a GA-RC REGISTER UPDATE message containing the AP-ID information of the PoA 4   710  to the GANC  700  to update location registration. 
     Meanwhile, when the UE  702  moves from the location of the PoA 4   710  to the location of the PoA 5   712 , the UE  702  does not need to transmit a GA-RC REGISTER UPDATE message because both the PoA  710  and the PoA  712  belong to the same GPA 2 . 
       FIG. 8  illustrates a paging procedure performed in the GAN in accordance with an embodiment of the present invention. 
     As shown in  FIG. 8 , a UE  800  is currently located at a PoA 2   804 , wherein a PoA 1   802 , the PoA 2   804 , and a PoA 3   806  belong to one GPA. 
     First of all, in step  812 , upon receipt of a paging message from an MSC or SGSN (MSC/SGSN)  810 , while a GANC  808  conventionally sends a GA-RRC PAGING REQUEST message only to the PoA (e.g. PoA 2   804 ) to which the UE  800  is currently connected, in this embodiment, the GANC  800  is adapted to transmit a GA-RRC PAGING REQUEST message to all the PoAs in the GPA to which the UE  800  currently belongs. That is, since the PoA 1   802 , the PoA 2   804 , and the PoA 3   806  belong to one GPA, the GANC  808  transmits a GA-RRC PAGING REQUEST message to the PoA 3   806  in step  814 , transmits a GA-RRC PAGING REQUEST message to the PoA 2   804  in step  816 , and transmits a GA-RRC PAGING REQUEST message to the PoA 1   802  in step  818 . 
     Then, the UE  800  receives a paging message through the PoA 2   804  because it is currently connected to the PoA 2   804 , and the UE  800  response with a paging response message and a GA-RRC INITIAL DIRECT TRANSFER message containing the AP_ID of the current PoA 2   804  to the GANC  808  in step  820 . Based on this message, the GANC  808  identifies the PoA 2   804  where the UE  800  is currently located, and transmits an Initial UE message containing the paging response message received from the UE  800  to the MSC/SGSN  810  in step  822 . 
     The subsequent processes will be performed in the same manner as the existing call operation and data service procedure following the authentication procedure as shown in  FIGS. 4 and 5 . 
     As described above, the present invention allows a GANC to group at least one PoA together to create GAN paging area (GPA) information and then transmit the GPA information to the UE in a generic access-resource control (GA-RC) register accept message during a location registration with the UE so that the UE checks the GPA information and performs a register update only when the UE moves between PoAs of different GPAs when changing PoA. 
     In accordance with the present invention as explained above, actual available time of the user equipment may be increased by efficient power consumption of a UE using a technique for location management of a UE in a GAN, and may be easily applied to a currently installed GAN because a lower-level access network interworking with the GAN is not required to be modified. 
     While the invention has been shown and described with respect to the particular embodiments, it will be understood by those skilled in the art that various changes and modification may be made without departing from the scope of the present invention as defined in the following claims.