Abstract:
A paging group network includes multiple paging groups formed by areas covered by base stations (BSs). The paging group network further includes an anchor paging controller (PC) and a relay PC. The anchor paging controller initiates a page to a mobile station (MS), addresses the paging group in which the MS is located, and stores status information about the MS in a corresponding location register (LR). The relay PC manages the paging groups. A method for updating MS locations is also provided. Thereby, the present invention optimizes the paging and location updating processes, and reduces the complexity of managing the idle mode.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/134,820, filed on Jun. 6, 2008, which is a continuation of International Application No. PCT/CN2006/003328, filed on Dec. 7, 2006, which claims priority to Chinese Patent Application No. 200510129398.X, filed on Dec. 7, 2005, all of which are hereby incorporated by reference in their entireties. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the communication field, and more particularly to a paging group network and a method for updating mobile station (MS) locations. 
     BACKGROUND 
     Idle mode is a working mode of mobile station (MS) in a mobile broadband wireless access system defined in IEEE 802.16e. In the idle mode, an MS moves in a very large area, and receives downlink broadcast service messages in a certain period interval. The MS is informed by the broadcast messages whether there is a downlink service to be sent. When roaming in the area, the MS does not need to register with a base station (BS) of the cell it is roaming in. Meanwhile, when the MS roams to different cells, it is unnecessary to perform normal operation processes such as handover, so the idle mode saves the power of MS and air interface resources 
     Areas covered by BSs may form a group named paging group. The paging group aims to constitute a continuous area. In the area, the MS does not need to send uplink services, but may determine whether there is downlink services sent to the MS by a downlink paging channel. The paging group must be large enough to make sure most MSs remain in the same paging group in a long time period; meanwhile, the paging group must be small enough to make sure the overhead of paging the MSs is reasonable in a paging group. 
     In the normal operation with a serving BS, an MS may enter the idle mode by sending a message request. Similarly, the serving BS may also request the MS to enter the idle mode by sending a message to the MS. Whether the MS forwardly initiates a request to enter the idle mode or the serving BS sends a message to request the MS initiatively to enter the idle mode, the MS needs to finish registering and entering the idle mode in a set period. 
     A paging reference model in the idle mode is defined in the WiMAX Worldwide Interoperability Microwave Access standard being constituted right now. A paging controller (PC) is a network entity capable of controlling activities of MSs in the idle mode. The entity is a logic entity in the current WiMAX network architecture, and is closely associated with another logic entity, i.e., the authenticator (the PC may be realized in the same physical network element (NE) as a part of the logic function of the authenticator). The physical location of the PC is either a physical NE access service network gateway (ASN GW) of the WiMAX network or another independent physical NE. In addition, as the PC needs to initiate a paging message according to the paging group in which the current MS is located, a location register (LR) is required to store status information of the MS, paging information, and information related to service flows. Generally, a PC logic entity is corresponding to an LR logic entity, and the two logic entities are realized in the same physical NE. 
     Suppose other physical NEs and logical entities in the WiMAX network are not considered,  FIG. 1  is a schematic diagram of a paging group network in a WiMAX network according to the prior art. The WiMAX paging reference model according to  FIG. 1  is adopted in the following technical descriptions, and the technology of the present invention includes, but not limited to the application in WiMAX system. 
     According to the paging reference model of  FIG. 1 , when the MS initiatively requests to enter the idle mode on BS 1  (Serving BS), or when BS 1  instructs the MS to enter the idle mode, through message interaction between the MS and BS 1  and between BS 1  and the ASN GW (a rear NE), the PC is informed that the MS enters the idle state, wherein the informing is realized in ASN GW 1 , and the status information, paging information, and service flow information of the MS are stored in the corresponding LR. The MS may carry the information which needs to be reserved when entering the idle mode in the idle model request message sent to BS 1 , and BS 1  may also configure similar information in an idle mode response message, adapted to inform the MS of the related information stored in the LR by the MS and the PC ID. The PC involved in the above process is an anchor paging controller (PC) serving the MS. In addition, after the MS enters the idle mode, corresponding R4 and R6 interfaces need to be released, but an R3 interface between the home agent (HA) and foreign agent (FA) need to be reserved. 
     According to the above scheme, when the network needs to page the MS in the idle state, the ASN GW in which the FA is located queries information related to the MS from the ASN GW in which the anchor PC/LR is located. The anchor PC/LR obtains the paging group in which the current MS is located according to the location record, and queries about the ASN GW in which PC is located that belongs to the paging group. The APC sends a message of paging the MS to the ASN GW in which the relay PCs related to the paging group is located. The anchor PC is required to configure and manage all possible paging group information in this scheme. As each PC may be the anchor PC of a different MS, all of the PCs need such configuration and management, the data configuration volume is very large, and the management is complicated. 
     According to the above scheme, in the idle mode, the MS needs to initiate periodically a location updating request message over air interface to the current BS in which the MS is located. After receiving the message, the BS sends a location updating message about the rear network to the corresponding PC according to the PC ID in the message. The PC determines whether the MS enters a new paging group according to the message; and if the MS enters a new paging group, the corresponding information in the LR is updated. 
     The disadvantages of the above scheme are as follows:
         1) The grouping of the paging groups is not limited or specified, leading to that the anchor PCs need to configure and manage all possible paging groups.  FIG. 2  is a schematic diagram of another paging group network according to the prior art. Meanwhile, as shown in  FIG. 2 , both paging group 1  and paging group 3  involve two ASN GWs. Thus, when data is delivered to the paging group in which an MS is located, the PC needs to deliver the paging message to multiple ASN GWs of the paging group in which the MS is located.   2) In the prior art, the corresponding relationship between the paging groups and ASN GWs need to be configured in the LR, thus resulting in unnecessary configuration and maintenance. In the situation of the paging group division shown in  FIG. 2 , the PC/LR needs to maintain the ASN GW information corresponding to each paging group; otherwise, when a paging message needs to be sent to a certain MS, the PC does not know which ASN GW the paging message should be delivered to.       

     SUMMARY 
     The embodiments of present invention provides a paging group network and a method for updating MS locations, adapted to solve the problem in the prior art of complicated management of paging groups by PCs and complex configuration data in the LR. 
     The paging group network includes multiple paging groups, wherein the paging groups are formed of multiple areas covered by BSs. The paging group network further includes an anchor paging controller (PC), adapted to initiate a paging to a mobile station (MS), address a paging group in which the MS is located, and store status information about the MS in a corresponding location register (LR); wherein a relay PC, adapted to manage the paging group. 
     The method for updating mobile station (MS) locations by adopting the paging group network includes the following steps: 
     Step  1 , a serving BS sends an MS location updating request to a relay PC controlling the serving BS; 
     Step  2 , the relay PC interacts the location updating request with an anchor PC, and assigns a new paging group to the MS; 
     Step  3 , the relay PC sends a location updating response carrying the new paging group information to the serving BS; 
     Step  4 , the anchor PC modifies information stored in a location register (LR) according to a result of location updating. 
     The embodiments of present invention optimize the paging and location updating processes, and reduce the management complexity of the idle mode. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING(S) 
         FIG. 1  is a schematic diagram of a paging group network in a WiMAX network according to the prior art; 
         FIG. 2  is a schematic diagram of another paging group network according to the prior art; 
         FIG. 3  is a schematic structural diagram of a paging group network according to an embodiment of the present invention; 
         FIG. 4  is a schematic flow chart illustrating how an MS switches between different paging groups according to an embodiment of the present invention; and 
         FIG. 5  is a detailed flow chart illustrating steps S 2  and S 3  according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention are described below with reference to the accompanying drawings. 
       FIG. 3  is a schematic structural diagram of a paging group network according to an embodiment of the present invention. As shown in  FIG. 3 , in the paging group network according to the embodiment of the present invention, a paging group may include multiple areas covered by BSs, a paging group is managed by a specific PC, and a PC manages some specific paging groups. In the idle mode, the anchor PC is only responsible for the paging control function on the MS, addressing the area where the MS is, controlling related processes of paging the MS, initiating a paging of the MS, knowing the result of location updating, and storing information related to the idle state of the MS (in the corresponding LR). The detailed management of a paging group is performed by the current relay PC in charge of the paging group. 
     The relay PC is adapted to act as an agent, forward and process the processes related to the MS location updating, and inform the anchor PC of the result of the location updating. The relay PC appears when the MS moves to a new paging group out of the control of the original anchor PC. 
     This scheme further includes that a paging group may be managed by multiple relay PCs. 
     The anchor PC may also function as a relay PC for managing a certain paging group in this scheme, equivalent to a special situation that, for a paging group in which an MS is located, the relay PC which manages the paging group also is the anchor PC which is responsible for addressing the MS and storing the status information of the MS. 
     By the above paging group network, optimizing the paging and location updating processes and reducing the complexity of managing the idle mode may be realized. An example of the paging group network is given below. 
       FIG. 3  is a schematic structural diagram of a paging group network according to an embodiment of the present invention. As shown in  FIG. 3 , two paging groups i.e., paging group 1  and paging group 2  are set. The paging group 1  includes BS 1  to BS 5 , and the paging group 2  includes BS 6  to BS 10 . Meanwhile, two PCs, i.e., PC 1  and PC 2  are set in the paging group network. PC 1  and PC 2  respectively function as the relay PC of paging group 1  and paging group 2 . 
     At first, the MS is located in BS 1 , and enters the idle mode from BS 1 . BS 1  is managed by PC 1 . At this time, PC 1  is the anchor PC of the MS in the idle mode. When the MS moves to BS 4  in the idle mode, the location of the MS needs to be updated. However, as BS 4  is also managed by PC 1 , in the location updating process, the MS only interacts with PC 1  which is the anchor PC of the MS. The designation of a new paging group and possible parameter settings are managed by the anchor PC. 
     However, when the MS moves to BS 6 , the location of the MS is updated. As BS 6  is managed by PC 2 , the MS needs to interact with both PC 1  and PC 2  during the location updating process. At this time, PC 1  is still the anchor PC of the MS, and PC 2  is also the relay PC of the MS. In this process, the new paging group of the MS is specified by PC 2 , i.e., the relay PC. If the paging cycle and paging offset need to be changed, the change is specified by the relay PC. And the specification result is reported to the anchor PC. Now, the anchor PC only needs to record the relay PC where the MS is located. When a paging to the MS is needed, the anchor PC informs the relay PC according to the recorded relay PC ID of the latest location updating of the MS. Therefore, the relay PC knows very clearly the situation of the paging groups managed by it. Moreover, if a paging group is possibly managed by multiple relay PCs, a relay PC managing the paging group will be configured with the IDs of other relay PCs which also manage the paging group. In this process, when the anchor PC needs to page the MS, after the paging message is sent to the relay PC on which the latest location updating occurs, the relay PC determines whether the paging group is managed by neighboring relay PCs according to the paging group information of the MS. If the paging group is managed by neighboring relay PCs, the paging is performed on BSs in the paging group, and the neighboring relay PCs are informed to page the BSs in the paging group. 
     The above process reduces the number of the paging groups managed by the anchor PC, that is, each PC manages certain specific paging groups. As a paging group may be managed by several PCs, each PC needs to configure not only the information about the BSs in the paging groups managed by the PC, but also the information about neighboring PCs of the paging groups managed by the PC. 
     In the above process, when the MS moves to a paging group that is not originally managed by the anchor PC, the anchor PC is changed to the current relay PC if necessary, i.e., the current relay PC is changed to the anchor PC of the MS during the location updating. In other words, when the MS updates its location in paging group 6 , PC 2  may be changed to be the anchor PC of the MS. 
     Another possibility also existing in the above structure of the paging group network is that, only one PC controls the related information, which may be seen as an overlapping of the relay PC and anchor PC. In this situation, the functions of the relay PC and anchor PC are integrated. 
       FIG. 4  is a schematic flow chart illustrating how an MS switches between different paging groups according to an embodiment of the present invention. According to the above scheme of the paging group network, the location updating process is shown in  FIG. 4 . 
     Step S 1 , the MS initiates a location updating request through a ranging request (RNG_REQ) message carrying a mobile station ID (MS ID) and an anchor paging c PC ID. 
     When the MS needs to perform the location updating, the MS initiates the location updating request through the RNG_REQ message carrying the MS ID and the anchor PC ID. The anchor PC ID is adapted to address the location information of the anchor PC which stores MS context information when the MS enters the idle mode. 
     Step S 2 , the location updating request carrying a serving BS ID is forwarded by the BS to the relay PC managing the BS. 
     In the embodiment of the present invention, the relay PC manages the paging group in which the MS is located. Therefore, the BS firstly forwards the location updating request to the relay PC managing the BS. The location updating request carries the MS ID, and/or the anchor PC ID, and/or the relay PC ID, and further carries the serving BS ID. 
       FIG. 5  is a detailed flow chart illustrating steps S 2  and S 3  according to an embodiment of the present invention. As shown in  FIG. 5 , step S 2  further includes determining whether the serving BS reserves valid authentication information according to the location updating request received by the serving BS. The valid authentication information includes a valid authorization key (AK), AK context information, or an anchor authenticator ID of the MS. If the serving BS reserves valid authentication information, step S 21  is performed; if the serving BS does not reserve valid authentication information, step S 22  is performed. 
     Step S 21 , whether the location updating request is valid is determined. If the location updating request is valid, step S 211  is performed; if the location updating request is invalid, step S 212  is performed. 
     Step S 211 , an RNG_RSP message carrying an unsafe location updating indication is sent; the MS is guided to perform a network reentry and end the location updating. 
     Step S 212 , an LU-REQ message is sent to a serving ASN GW, and the serving ASN GW forwards the LU-REQ message to the ASN GW in which the relay PC is located. The LU-REQ message carries the MS ID, BS ID and anchor PC ID. 
     Step S 22 , whether the serving BS knows the information about the anchor authenticator ID of the MS is determined. If the serving BS does not know the information about the anchor authenticator ID of the MS, step S 221  is performed; if the serving BS knows the information about the anchor authenticator ID of the MS, step S 222  is performed. 
     Step S 221 , if the serving BS does not know the authentication information of the MS, the serving BS sends the LU-REQ message to the serving ASN GW. The serving ASN GW forwards the LU-REQ message to the ASN GW in which the RPC is located. The LU-REQ messages carry MS ID, BS ID, and/or anchor PC ID, and/or relay PC ID, and further carry an instruction to inform the MS of the authentication information. 
     Step S 222 , if the serving BS knows the information about the anchor authenticator ID of the MS, the serving BS directly sends an AK-request message to the ASN GW in which the anchor authenticator is located, and requests the AK and AK context of the MS. The AK-request message carries the MS ID and BS ID. After receiving the AK-request message, the anchor authenticator generates a new AK and AK context for the MS, and sends the new AK and AK context to the serving BS through an AK-transfer message. After verifying the AK and AK context, the serving BS sends a location updating request LU-REQ message to the ASN GW in which the RPC is located. In addition, the LU-REQ messages carry MS ID, BS ID, and/or anchor PC ID, and/or relay PC ID. 
     Step S 3 , the relay PC interacts the location updating request with the anchor PC, and assigns a new paging group to the MS. 
     In this step, the ASN GW in which the relay PC is located forwards the location updating request to the ASN GW in which the anchor PC is located, and the forwarded message carries the relay PC ID cell. 
     Step S 31 , if step S 221  is performed in step S 2 , after the anchor PC interacts information with the relay PC, the relay PC assigns the new paging group to the MS. The details are shown below. 
     After the anchor PC receives the location updating request, the ID information of the relay PC in which the MS is located is recorded, and the authentication information of the MS is found from an anchor LR associated with the anchor PC. Then, a location updating response (LU-RSP) message is replied to the ASN GW in which the relay PC is located. The LU-RSP messages carry MS ID, BS ID, and/or anchor PC ID, and/or relay PC ID and anchor authentication ID. (In this step, the anchor PC may also directly inform the anchor authenticator to generate a new AK and AK context for the MS. Thus, the LU-RSP message may directly carry the generated AK and AK context instead of the anchor authenticator ID. The above scheme is adopted when the anchor PC and the anchor authenticator exist in the same physical entity or in different physical entities. For the latter situation, the anchor PC requests the AK and AK context from the anchor authenticator of the MS before replying the location updating response to the relay PC). After receiving the LU-RSP message sent by the anchor PC, the relay PC is responsible for managing the paging groups within its management domain according to the configuration of the paging groups (i.e., the management mode of the paging groups of the present invention), and assigns the new paging group to the MS. Thus, the paging group ID is obtained. In this process, the relay PC needs to change the paging parameters, namely, the paging cycle and paging offset of the MS at the same time according to the rules of the relay PC. At this time, the LU-REQ message sent to the anchor PC by the relay PC further carries the new paging group ID assigned to the MS, the new paging cycle and the new paging offset (the relationship between these three parameters is “or”. In addition, if only the paging group is changed, the LU-REQ message only carries the paging group ID; and if all the parameters are changed, the LU-REQ message carries all of the three parameters). 
     Step S 32 , if steps of S 212  and S 222  are performed in step S 2 , the relay PC is responsible for managing the paging groups within its management domain according to the configuration of the paging groups (i.e., the management mode of the paging groups of the present invention), and assigns the new paging group to the MS. Thus, the paging group ID is obtained. In this process, the relay PC needs to change the paging parameters, namely, the paging cycle and paging offset of the MS at the same time according to the rules of the relay PC. At this time, the LU-REQ message sent to the anchor PC by the relay PC further carries the new paging group ID assigned to the MS, the new paging cycle and the new paging offset (the relationship between these three parameters is “or”. In addition, if only the paging group is changed, the LU-REQ message only carries the paging group ID; and if all the parameters are changed, the LU-REQ message carries all of the three parameters). 
     After receiving the location updating request sent from the relay PC, the anchor PC reserves the content of the LU-REQ message, for example, parameters such as paging group ID, paging cycle, and paging offset set by the relay PC for the MS and the relay PC ID. 
     Then, the anchor PC sends the LU-RSP message carrying the MS ID, anchor PC ID, relay PC ID and BS ID to the relay PC. 
     Step S 4 , the relay PC sends the LU-RSP carrying the information about the new paging group to the serving BS. 
     The ASN GW in which the relay PC is located forwards the LU-RSP message to the serving ASN GW of the serving BS in which the MS currently is located. The message carries the parameters such as the MS ID, the new paging group ID assigned to the MS, paging cycle possibly newly set and paging offset. 
     Step S 5 , the serving BS sends the LU-RSP message to the anchor PC. 
     The serving ASN GW forwards the LU-RSP message to the serving BS. After receiving the LU-RSP message, the serving BS further performs the following determining. 
     If this step is performed directly after step S 31 , and if the LU-RSP message carries the information about the anchor authenticator ID, the serving BS sends an AK-request message to the ASN GW in which the anchor authenticator is located, and requests to generate the AK and AK context. The anchor authenticator returns the AK and AK context to the serving BS through the AK-transfer. After obtaining the AK and AK context, the serving BS verifies the RNG-REQ message. If the verifying result is positive, the serving BS replies a ranging response (RNG_RSP) message indicating the success of the location updating to the MS. In addition, the RNG_RSP message carries the new paging group ID and the information about the anchor PC ID. If the verifying result is negative, the RNG_RSP carries a failure indication, and guides the MS to perform network reentry. Afterward, a location updating confirmation (LU-Confirm) message is replied to the relay PC, and the LU-Confirm message carries the location updating success or failure indication. After receiving the LU-Confirm message, the relay PC further replies the LU-Confirm message to the anchor PC. If the location updating is successful, the message carries parameters such as the MS ID, relay PC ID, BS ID, the paging group ID newly assigned by the relay PC to the MS in Step  4 a, paging offset and paging cycle. 
     If this step is performed directly after step S 32 , the serving BS packages the obtained parameters such as the paging group ID, paging cycle, and paging offset in the RNG_RSP message, and replies to the MS according to definitions in IEEE802.16e. Meanwhile, the serving BS replies the LU-Confirm message indicating the location updating confirmation to the ASN GW in which the relay PC is located. In addition, the LU-Confirm message carries the success or failure indication. 
     Step S 6 , on receiving the LU-Confirm message sent from the relay PC, the anchor PC modifies the information stored in the LR. 
     After the anchor PC receives the LU-Confirm message sent from the relay PC, if the location updating confirmation is successful, the anchor PC stores the obtained information which includes the new BS ID of the BS in which the MS belongs, the paging group ID, the relay PC ID of the relay PC to which the MS located, the paging offset, and the paging cycle in the associated LR. If the location updating fails, the above obtained information will be deleted. 
     Another situation existing in the above location updating process is that, if the relay PC knows that the serving BS may obtain the authentication information required for verifying the location updating request of the MS from the received location updating request, for example, the anchor authenticator ID or valid AK and AK context of the MS, the relay PC directly assigns a new paging group to the MS, and replies the location updating response to the serving BS. The location updating response carries the new paging group ID, and/or paging cycle, and/or paging offset. 
     After receiving the LU-Confirm message sent from the relay PC, the serving BS replies the location updating response to the MS, and replies the LU-Confirm message to the relay PC. The LU-Confirm message carries an indication of whether the location updating is successful. After the relay PC receives the LU-Confirm message sent by the serving BS, if the location updating is successful, the relay PC interacts with the anchor PC, and sends the LU-Confirm message. The LU-Confirm message sent by the relay PC and received by the anchor PC further includes the paging group ID newly assigned by the relay PC to the MS, and/or paging cycle, and/or paging offset. If the location updating fails, the original information stored in the LR before operating the location updating is reserved. 
     In this process, the anchor PC only interacts with the relay PC in the location updating confirmation process to obtain the result of the MS location updating. The processing before the location updating confirmation is performed by the relay PC. 
     The embodiments of the present invention clarify the method for managing the paging groups and PCs, optimize the paging and location updating processes, and reduce the complexity of managing the idle mode. 
     Those in the art may make modifications and variations without departing from the spirit and scope of the present invention. Therefore, these modifications and variations made based on the claims and equivalent techniques of the present invention fall within the scope of the present invention.