Abstract:
User traffic transmitted and received by a mobile station is distributed so as not to be converged on a gateway. The gateway includes a signaling processing device and bearer data processing devices, the signaling processing device is concentrated, and the bearer data processing devices are distributed to networks close to base stations. The signaling processing device recognizes, in response to a connection request from each mobile station, a position of the base station covering the mobile station, allocates the bearer data processing device connected to the network close to the base station, and connects the base station to the allocated bearer data processing devices.

Description:
CLAIM OF PRIORITY 
     The present application claims priority from Japanese patent application JP 2011-249789 filed on Nov. 15, 2011, the content of which is hereby incorporated by reference into this application. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a wireless communication system, a wireless communication method, and a gateway, and more particularly to a wireless communication system such as a mobile communication system, a wireless communication method such as a mobile communication system, and a distributed gateway used in the wireless communication system such as the mobile communication system, which enhance a load distribution effect of a communication network. 
     2. Background Art 
     In general, a mobile communication system has a hierarchical structure. A WiMAX system will be described as an example of the mobile communication system having the hierarchical structure. 
       FIG. 23  is a diagram illustrating an outline of the WiMAX system. 
     The WiMAX system includes a mobile station (MS)  700 , a base station (BS)  600 , a BS  601 , a BS  602 , an access service network gateway (ASN-GW)  100  that manages the BSs, and a connectivity service network (CSN)  400 . The CSN  400  has authentication, authorization, and accounting (AAA) related to accounting and authentication. Also, the CSN  400  has a home agent (HA) in a system that supports an IP. When the CSN  400  provides an internet service, the CSN  400  is connected to an internet  500 . 
     The WiMAX system has a hierarchical structure in which the plurality of BS  600 , BS  601 , and BS  602  are connected to the ASN-GW  100  through a network  5002 , a network  5003 , and a network  5001 . One of reasons that the mobile communication system has the hierarchical structure resides in the mobility realization of the MS  700 . For example, let us consider a case in which the MS  700  travels from the BS  600  to the BS  601 . The BS  600  of a travel source and the BS  601  of a travel destination are consolidated in the identical ASN-GW  100 , to thereby realize handover in which the ASN-GW  100  detects the travel of the MS  700 , and continues service. 
       FIG. 25  is a diagram illustrating a connection sequence of the WiMAX specified by WiMAX Forum of a standards body. 
     The MS  700 , the BS  600 , the ASN-GW  100 , and the CSN  400  exchange messages with each other in conformity with the provision ( 800  to  821 ), and establish a radio path  822  between the MS  700  and the BS  600 , and a generic routing encapsulation (GRE) capsuling path  823  between the BS  600  and the ASN-GW  100 . When the MS  700  accesses to the internet, the MS  700  transmits user data to the BS  600  as radio data  7100 . The BS  600  transfers the received user data to the ASN-GW  100  as GRE capsuling data  7101 . Further, the ASN-GW  100  transfers the user data to the CSN  400 , and the CSN  400  transfers the user data to the internet  500 . 
       FIG. 26  is a diagram illustrating a GRE packet format of the GRE capsuling data between the BS and the ASN-GW. A GRE packet includes an IP header  7050 , a GRE header  7051 , and user data  7052 . The user data  7052  is an IP packet transmitted by the MS  700 . IP addresses of the BS  600  and the ASN-GW  100  are stored in the IP header  7050 , and used as communication addresses of the BS  600  and the ASN-GW  100  which terminate a GRE tunnel. A GRE KEY specified in, for example, an RFC 2784 GRE and an RFC 1701 GRE is included in the GRE header  7051 , and used to identify the MS  700 . 
     In the mobile system thus stratified, the user data communicated by the MS  700  passes through the BS  600  via a radio zone as the radio data  7100 , passes through the network  5002  and the network  5001  between the BS  600  and the ASN-GW  100 , and arrives at the CSN  400  through the ASN-GW  100 . The CSN  400  transfers the user data to the internet  500  according to routing. 
       FIG. 24  is a functional schematic diagram of the ASN-GW in the WiMAX system. 
     Also, the WiMAX Forum specifies that a function of the ASN-GW is divided into a function of processing signaling and a function of processing bearer data in a form illustrated in  FIG. 24 . A function unit for processing signaling is called “ASN-GW decision point  200 ”, and a function unit for processing the bearer data is called “ASN-GW enforcement point  300 ”. 
     As a related art, JP-A-2009-253678 proposes a method in which a load of a device is checked and allocated as an allocation method to the bearer data processing function. 
     SUMMARY OF THE INVENTION 
     In the above-mentioned related art mobile communication system, because a hierarchical network is applied, a plurality of base stations are intensively connected to the ASN-GW  100 . For that reason, data communicated by a large number of MSs behind the plurality of BSs is multiplexed every time the data passes through the networks  5002  and  5003 , further multiplexed by the network  5001  that bundles the networks together to arrive at the ASN-GW  100 , and is converged. That is, a data traffic volume is increased more as the data comes closer to the ASN-GW  100 . It is assumed that the increase in the data traffic presses a network capacity with the development of the mobile communication and an increase in the capacity of the content in recent years, and needs for decreasing a network load are demanded. Also, JP-A-2009-253678 has proposed that the signaling function unit and the bearer data function unit are separated from each other, and the bearer data function unit checks the amount of load of the bearer data function unit, and allocates the load to users. However, although the load of the bearer data function unit within the device can be distributed, a data traffic load of the overall network cannot be distributed. When the ASN-GWs are simply distributed as a solution, it is assumed that handover across the ASN-GWs frequently occurs, and the amount of signaling for handover is increased. As a result, service may be discontinued in a system applying no mobile IP. 
     The present invention has been made in view of the above, and one object of the present invention is to distribute a network load by terminating bearer data by a bearer data processing device arranged in a network close to a base station, and transferring the bearer data to an internet connected to the same network. Another object of the present invention is to process handover as handover within a gateway for the base station by converging signaling processing devices. 
     In order to achieve the above object, according to the present invention, there is provided a mobile communication system having a hierarchical structure such that a plurality of base stations are connected to a gateway through networks, and each of the plurality of base stations communicates with a plurality of mobile stations, in which the gateway includes a signaling processing device and bearer data processing devices, the signaling processing device is concentrated, and the bearer data processing devices are distributed to the networks close to the base stations. The signaling processing device of the gateway determines, in response to a connection request from each mobile station, the bearer data processing device connected to the network close to the base station covering the mobile station according to a position of the base station, and connects the base station to the determined bearer data processing device. Also, with the provision of a plurality of the bearer data processing devices within an area of each network, when a certain bearer data processing device is in failure, another bearer data processing device which is not in failure is specified, and notified the base station of. 
     According to the first solving means of the present invention, there is provided a wireless communication system comprising a hierarchical structure such that a plurality of base stations are connected to a gateway through a network, and each of the plurality of base stations communicates with a plurality of wireless terminals, wherein 
     the gateway includes a signaling processing device for processing signaling, and one or a plurality of bearer data processing devices for processing bearer data, 
     the plurality of base stations, the network, and one or a plurality of the bearer data processing devices are defined as one area, 
     one signaling processing device is concentrated for a plurality of the areas, 
     the signaling processing device includes a position management table indicating which area each of the base stations is located in, and which area the bearer data processing devices are set with respect to the areas in which 
     the respective base stations are located, the signaling processing device allocates the bearer data processing device to the area in which the base station is located in response to a connection request from any one of the wireless terminal, 
     each of the bearer data processing devices has an information table that stores wireless terminal addresses, base station addresses, and capsulation key information necessary for encapsulating and decapsulating in association with each other, 
     each of the bearer data processing devices is located on the basis of the area in which the base stations are located, and communicates the bearer data with one or the plurality of base stations within the area, 
     each of the base stations transmits the connection request including base station identification information to the signaling processing device according to a request from the wireless terminal, 
     upon receiving the connection request, the signaling processing device refers to the position management table, and executes bearer data processing device search processing for specifying a bearer data processing device address of the bearer data processing device connected to the base station on the basis of the base station identification information included in the connection request, 
     the signaling processing device transmits an address to be allocated to the wireless terminal to the base station, 
     the signaling processing device transmits the bearer data processing device address of the bearer data processing device specified by the bearer data processing device search to the base station, 
     the signaling processing device and the bearer data processing device exchange the capsulation key information necessary for encapsulating and decapsulating between the base station and the bearer data processing device, 
     the signaling processing device transmits a setup request including the wireless terminal address, the base station address, and the capsulation key address to the bearer data processing device in which the capsulation key information is specified by the bearer data processing device search, and 
     the bearer data processing device sets the wireless terminal address, the base station address, and the capsulation key information to the information table according to the setup request received from the signaling processing device, and completes a connection of a capsulation path between the base station and the bearer data processing device. 
     According to the second solving means of the present invention, there is provided a wireless communication method in a wireless communication system comprising a hierarchical structure such that a plurality of base stations are connected to a gateway through a network, and each of the plurality of base stations communicates with a plurality of wireless terminals, wherein 
     the gateway includes a signaling processing device for processing signaling, and one or a plurality of bearer data processing devices for processing bearer data, 
     the plurality of base stations, the network, and one or a plurality of the bearer data processing devices are defined as one area, 
     one signaling processing device is concentrated for a plurality of the areas, 
     the signaling processing device includes a position management table indicating which area each of the base stations is located in, and which area the bearer data processing devices are set with respect to the areas in which the respective base stations are located, 
     the signaling processing device allocates the bearer data processing device to the area in which the base station is located in response to a connection request from any one of the wireless terminal, 
     each of the bearer data processing devices has an information table that stores wireless terminal addresses, base station addresses, and capsulation key information necessary for encapsulating and decapsulating in association with each other, 
     each of the bearer data processing devices is located on the basis of the area in which the base stations are located, and communicates the bearer data with one or the plurality of base stations within the area, 
     each of the base stations transmits the connection request including base station identification information to the signaling processing device according to a request from the wireless terminal, 
     upon receiving the connection request, the signaling processing device refers to the position management table, and executes bearer data processing device search processing for specifying a bearer data processing device address of the bearer data processing device connected to the base station on the basis of the base station identification information included in the connection request, 
     the signaling processing device transmits an address to be allocated to the wireless terminal to the base station, 
     the signaling processing device transmits the bearer data processing device address of the bearer data processing device specified by the bearer data processing device search to the base station, 
     the signaling processing device and the bearer data processing device exchange the capsulation key information necessary for encapsulating and decapsulating between the base station and the bearer data processing device, 
     the signaling processing device transmits a setup request including the wireless terminal address, the base station address, and the capsulation key address to the bearer data processing device in which the capsulation key information is specified by the bearer data processing device search, and 
     the bearer data processing device sets the wireless terminal address, the base station address, and the capsulation key information to the information table according to the setup request received from the signaling processing device, and completes a connection of a capsulation path between the base station and the bearer data processing device. 
     According to the third solving method of the present invention, there is provided a gateway in a wireless communication system comprising a hierarchical structure such that a plurality of base stations are connected to the gateway through a network, and each of the plurality of base stations communicates with a plurality of wireless terminals, wherein 
     the gateway includes a signaling processing device for processing signaling, and one or a plurality of bearer data processing devices for processing bearer data, 
     the plurality of base stations, the network, and one or a plurality of the bearer data processing devices are defined as one area, 
     one signaling processing device is concentrated for a plurality of the areas, 
     the signaling processing device includes a position management table indicating which area each of the base stations is located in, and which area the bearer data processing devices are set with respect to the areas in which the respective base stations are located, 
     the signaling processing device allocates the bearer data processing device to the area in which the base station is located in response to a connection request from any one of the wireless terminal, 
     each of the bearer data processing devices has an information table that stores wireless terminal addresses, base station addresses, and capsulation key information necessary for encapsulating and decapsulating in association with each other, 
     each of the bearer data processing devices is located on the basis of the area in which the base stations are located, and communicates the bearer data with one or the plurality of base stations within the area, 
     from each of the base stations, the connection request including base station identification information is transmitted to the signaling processing device according to a request from the wireless terminal, 
     upon receiving the connection request, the signaling processing device refers to the position management table, and executes bearer data processing device search processing for specifying a bearer data processing device address of the bearer data processing device connected to the base station on the basis of the base station identification information included in the connection request, 
     the signaling processing device transmits an address to be allocated to the wireless terminal to the base station, 
     the signaling processing device transmits the bearer data processing device address of the bearer data processing device specified by the bearer data processing device search to the base station, 
     the signaling processing device and the bearer data processing device exchange the capsulation key information necessary for encapsulating and decapsulating between the base station and the bearer data processing device, 
     the signaling processing device transmits a setup request including the wireless terminal address, the base station address, and the capsulation key address to the bearer data processing device in which the capsulation key information is specified by the bearer data processing device search, and 
     the bearer data processing device sets the wireless terminal address, the base station address, and the capsulation key information to the information table according to the setup request received from the signaling processing device, and completes a connection of a capsulation path between the base station and the bearer data processing device. 
     It is possible, according to the present invention, to distribute a network load by terminating bearer data by a bearer data processing device arranged in a network close to a base station, and transferring the bearer data to an internet connected to the same network. Also, it is possible, according to the present invention, to process handover as handover within a gateway for the base station by converging signaling processing devices. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a mobile communication system according to an embodiment of the present invention; 
         FIG. 2  is a configuration diagram of a signaling processing device according to an embodiment of the present invention; 
         FIG. 3  is a configuration diagram of a bearer data processing device according to an embodiment of the present invention; 
         FIG. 4  is a diagram illustrating an example of a BS position management table according to an embodiment of the present invention; 
         FIG. 5  is a diagram illustrating an example of a position management table in the bearer data processing device; 
         FIG. 6  is a diagram illustrating an example of an information table necessary for bearer data assembly and disassembly in the bearer data processing device; 
         FIGS. 7A and 7B  are diagrams illustrating an IPinIP encapsulation processing and decapsulation processing; 
         FIG. 8  is a diagram illustrating an example of a table storing statistical information necessary for accounting in the bearer data processing device; 
         FIG. 9  is a sequence diagram illustrating connection processing according to an embodiment of the present invention; 
         FIG. 10  is a flowchart illustrating allocation processing in the bearer data processing device according to an embodiment of the present invention; 
         FIG. 11  is a flowchart illustrating bearer data transfer in the bearer data processing device according to an embodiment of the present invention; 
         FIG. 12  is a diagram illustrating a format example of a setup request to the bearer data processing device; 
         FIG. 13  is a diagram illustrating decapsulation processing; 
         FIG. 14  is a diagram illustrating encapsulation processing; 
         FIG. 15  is a sequence diagram illustrating disconnection processing according to an embodiment of the present invention; 
         FIG. 16  is a diagram illustrating an example of the BS position management table according to an embodiment of the present invention; 
         FIG. 17  is a diagram illustrating a format of a BSID according to an embodiment of the present invention; 
         FIG. 18  is a flowchart illustrating the allocation processing in the bearer data processing device according to an embodiment of the present invention; 
         FIG. 19  is a diagram illustrating an example of the BS position management table according to an embodiment of the present invention; 
         FIG. 20  is a flowchart illustrating the allocation processing in the bearer data processing device according to an embodiment of the present invention; 
         FIG. 21  is a diagram illustrating an example of the BS position management table according to an embodiment of the present invention; 
         FIG. 22  is a flowchart illustrating the allocation processing in the bearer data processing device according to an embodiment of the present invention; 
         FIG. 23  is a schematic diagram of a WiMAX system which is one of the mobile communication systems; 
         FIG. 24  is a schematic diagram of a function of an ASN-GW in the WiMAX system; 
         FIG. 25  is a diagram illustrating a connection sequence of the WiMAX; and 
         FIG. 26  is a diagram illustrating a packet format of GRE capsuling data. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A. First Embodiment 
     Hereinafter, a description will be given of a WiMAX system according to an embodiment of the present invention. 
     1. System 
       FIG. 1  is a diagram illustrating a configuration of a WiMAX system according to this embodiment. 
     The WiMAX system according to this embodiment includes an MS  700 , a BS  600 , a BS  601 , a BS  602 , a GW-EP  301 , a GW-EP  302 , and a GW-EP  303  which are bearer data processing units of an ASN-GW, a GW-DP  201  which is a signaling function unit of the ASN-GW, a CSN  400 , an internet  500 , an internet  501 , an internet  502 , and a network  5001 , a network  5002 , and a network  5003  which are connected with devices. The GW-DP  201 , the GW-EP  301 , the GW-EP  302 , and the GW-EP  303  are characteristic configurations of this embodiment. Also, as characteristic definitions of this embodiment, it is assumed that the GW-EP  301 , the BS  600 , the BS  601 , and the network  5002  are in an area 1, and the GW-EP  302 , the GW-EP  303 , the BS  602 , and the network  5003  are in an area 2. 
       FIG. 2  is a diagram illustrating a configuration of the GW-DP  201  according to the embodiment of the present invention. 
     The GW-DP  201  includes an I/O port  2005  having a physical interface connected to the BSs and the CSN, a packet buffer  2006  that stores data received from the I/O port  2005  therein, a control unit  2002  that decrypts the received data to create an appropriate response message, a program memory  2003  in which software is stored, a GW-EP position management unit  2004  that manages position information on the BS and the GW-EP, and an EP-IF  2007  that communicates with the EP-GW. 
       FIGS. 4 and 5  illustrate an example of a table stored in the EP-GW position management unit  2004 . The table of  FIG. 4  includes an index, a BS IP address, and an area, and the area in which the BSs are located is specified and set in advance. A table of  FIG. 5  includes an area, a GW-EP IP address, and a state. The state is information such as a flag showing an IP address of the GW-EP set within the area and a state of the GW-EP are normal, or failure. 
       FIG. 3  is a diagram illustrating configurations of the GW-EP  301 , the GW-EP  302 , and the GW-EP  303  according to the embodiment of the present invention. Each of the GW-EP  301 , the GW-EP  302 , and the GW-EP  303  includes an I/O port  3014  having a physical interface that connects the BS and the CSN to each other, an encapsulation/decapsulation processing unit  3015  that dissembles and assembles data received from the I/O port  3014 , a control unit  3011  that instructs and sets information necessary for the disassembly and assembly of the data, a program memory  3012  in which software is stored, an accounting statistics collection unit  3013  that stores statistics data that are an accounting base, a DP-IF  3016  that provides a notice to the GW-DP, and a bus  3010  that connects the respective function units to each other. 
       FIG. 6  illustrates an example of a table stored in the encapsulation/decapsulation processing unit  3015 . The table of  FIG. 6  includes an index, an MS IP address, a BS IP address, a down link GRE KEY, an up link GRE Key, and a connection type. Further, the table can include an index, an HA IP address, an SPI, and an MIP KEY necessary for a mobile IP connection. 
       FIG. 8  illustrates an example of a table stored in the accounting statistics collection unit  3013 . The table includes an index, the number of down link bytes, the number of up link bytes, the number of down link packets, and the number of up link packets. 
     2. Connection Sequence 
     Subsequently, a connection sequence according to this embodiment will be described. 
       FIG. 9  is a diagram illustrating an example of a procedure for determining the allocation of the GW-EPs in the connection sequence. 
     The MS  700  transmits an SBC-REQ  800  that is a connection request to the BS  600  when making a request for connection. The BS  600  that has received the SBC-REQ  800  transmits MS_PreAttachment_Req.  801  corresponding to the connection request to the GW-DP  201 . Upon receiving the MS_PreAttachment_Req.  801 , the GW-DP  201  specifies the GW-EP suitable for connection to the BS  600  that has transmitted the MS_PreAttachment_Req.  801  with the use of the tables of  FIGS. 4 and 5  in the EP-GW position management unit  2004  of  FIG. 2 . 
       FIG. 10  is a flowchart illustrating processing for specifying the GW-EP suitable for the BS  600  that has transmitted the request for connection. 
     Upon receiving the MS_PreAttachment_Req.  801 , the control unit  2002  starts steps in  FIG. 10 , and allows the operation to proceed to Step S 2002 . In Step  2002 , the control unit  2002  specifies an IP address of the BS. A source IP address included in an IP header of the MS_PreAttachment_Req.  801  is the IP address of the BS. Upon specifying the BS IP address, the control unit  2002  allows the operation to proceed to Step  2003 . In Step  2003 , an area in which the BS is located is specified with the use of the table of  FIG. 4 . First, the control unit  2002  searches the BS IP address extracted in Step  2002  from a BS IP address column of the table. An area column on the same row as that of the matched index is the area in which the BS is located. For example, if the BS IP address of the extracted BS  600  is 192.168.10.2, it is found that the index matches an index 1, and an area thereof is 1. After specifying the area, the control unit  2002  allows the operation to proceed to Step  2004 . In Step  2004 , the control unit  2002  specifies the IP address of the suitable GW-EP with the use of the table in  FIG. 5 . The control unit  2002  searches the area specified in Step  2003  from an area row, and acquires the GW-EP IP address on the matched row. In the case of the area 1 in the above-mentioned example, 192.168.100.1 becomes the GW-EP IP address. After acquiring the GW-EP IP address, the control unit  2002  allows the operation to proceed to Step  2005 . In this Step  2005 , the control unit  2002  determines whether a state of the GW-EP IP address acquired in Step  2004  is normal, or failure. If failure, the operation is returned to Step  2004 , and the control unit  2002  searches another GW-EP IP address. If the state is normal, the control unit  2002  returns the operation to Step  2006 , and completes the operation. 
     Returning to  FIG. 9 , when GW-EP search processing  830  is completed, the GW-DP  201  transmits a response message MS_PreAttachment_Rsp  802  responsive to the MS_PreAttachment_Req.  801  to the BS  600 . The BS  600  transmits a MS_PreAttachment_Ack  804  to the GW-DP  201  as a response to reception of the response message MS_PreAttachment_Rsp  802 . Upon receiving the MS_PreAttachment_Ack  804 , the GW-DP  201  transmits an EAP-Request  805  to the BS  600  for conducting authentication. Upon receiving the EAP-Request  805 , the BS  600  transfers the EAP-Request  805  to the MS  700  as an EAP-REQ  806 , and thereafter transmits an EAP-RSP  807  response from the MS  700  to the GW-DP  201  as an EAP-Response  808 . 
     An network access identifier (NAI) called “identity” is included in the EAP-Response  808 . Upon receiving the EAP-Response  808 , the GW-DP  201  extracts the NAI. The NAI has a format of user@Domain, and a domain to which the MS  700  joins can be known by viewing the domain. The GW-DP  201  determines a connection type (simple IP or mobile IP) for each of the domains in advance, and further extracts the domain from the extracted NAI. The GW-DP  201  knows the domain from the extracted domain, and determines whether the connection type of the MS  700  that has made the request for connection is the simple IP, or the mobile IP. After determination of the connection type, the GW-DP  201  transmits an Access-Request  809  to an authentication server set within the CSN  400 . Thereafter, an EAP authentication  810  is conducted between the authentication server and the MS  700 , and if authentication results are successful, an Access-Accept  811  is transmitted to the GW-DP  201  from the authentication server. The Access-Accept  811  includes an IP address to be allocated to the MS  700 . After receiving the Access-Accept  811 , the GW-DP  201  extracts the IP address to be allocated to the MS  700 , stores the IP address in the GW-DP  201 , and thereafter transmits the IP address to the BS  600  as an EAP-Success  812 . Further, the BS  600  transmits an EAP-SUC  813 . 
     After that, signals necessary for connection are exchanged between the BS  600  and the GW-DP  201  in conformity with the connection sequence specified by the WiMAX Forum (information exchange  814 , radio encryption key/MS information exchange  815 ). With advancing of the processing, the GW-DP  201  transmits a Path_Reg_Req.  816  to the BS. The Path_Reg_Req.  816  specifies that the IP address of the GW-EP specified by GW-EP search processing  830  can be allocated. In the above-mentioned example, the GW-DP  201  notifies the BS  600  of 192.168.100.1. Upon receiving the Path_Reg_Req.  816 , the BS  600  transmits a Path_Reg_Rsp.  819  which is a response message to the GW-DP  201 . The GW-DP  201  transmits a Path_Reg_Ack  820  as a response to reception of the Path_Reg_Rsp.  819 . In the Path_Reg_Req.  816  and the Path_Reg_Rsp.  819 , GRE KEY information necessary for encapsulating and decapsulating is exchanged between the BS  600  and the GW-EP  301 . 
       FIG. 13  is a diagram illustrating decapsulation processing. The GRE KEY is a KEY stored in a GRE header of a packet format illustrated in  FIG. 13 , which is an identifier that specifies the MS. 
     The GW-DP  201  transmits a setup request  831  to the GW-EP  301  in which the GRE KEY information is specified by the GW-EP search processing  830 . 
       FIG. 12  illustrates an example of a format of the setup request. 
     The setup request includes an IP header  8311 , an UDP header  8312 , a type  8313 , and one or a plurality of information elements  8310 . The type  8313  is used for distinguishing the setup request  831  and a setup response  832 . The information elements  8310  include information set from the GW-DP to the GW-EP. In the first embodiment, elements of the MS IP address, the BS IP address, the down link GRE KEY, and the up link GRE KEY are included as the information elements of the setup request  831 . Also, if the information terminal is a system that supports the mobile IP, an HA IP address and the connection type (simple IP or mobile IP) necessary for the mobile IP can be also included. 
     The GW-EP  301  receives the setup request  831  transmitted from the GW-DP  201  from the DP-IF  3016  of  FIG. 3 . The received message is decrypted by the control unit  3011 , and the MS IP address, the BS IP address, the down link GRE KEY, the up link GRE KEY, and the connection type are set to blank indexes of the table in  FIG. 6 , of the encapsulation/decapsulation processing unit  3015 . If the HA IP address, the SPI, and the MIP KEY are included in the information element for the mobile IP, the control unit  3011  sets the mobile IP for the connection type, and also sets values thereof. If no information related to the mobile IP is included in the information element for the simple IP, the control unit  3011  sets the simple IP for the connection element. Upon finishing setting for the respective tables, the GW-EP  301  creates the setup response  832 , and transmits the setup response  832  to the GW-DP  201 . 
     Returning to  FIG. 9 , upon completing the setting for the GW-EP  301 , a GRE capsuling path  823  is completed between the BS  600  and the GW-EP  301 . Thereafter, a DHCP exchange  824  is conducted, and the GW-DP  201  notifies the MS  700  of the IP address to be allocated to the MS  700 , which is extracted and stored when receiving the Access-Accept  811 , and completes the connection. When supporting the mobile IP, the GW-DP  201  establishes the HA and a mobile IP  825  set in the CSN  400 . 
     Subsequently, the routing operation of the user data will be exemplified by a case in which the MS  700  accesses to the internet. The MS  700  transmits the user data from the MS  700  toward a destination of the internet for connection to the internet. The user data arrives at the BS  600  through a radio zone. The BS  600  conducts GRE encapsulating on the user data with the use of the GRE KEY of the GRE capsuling path established by the above-mentioned connection sequence, and transmits the user data to the GW-EP  301  as GRE capsuling data  7101 . Upon receiving the GRE capsuling data from the I/O port  3014 , the GW-EP  301  transfers the GRE capsuling data to the encapsulation/decapsulation processing unit  3015 . 
     The data reception leads the encapsulation/decapsulation processing unit  3015  to conduct routing processing according to a flowchart of  FIG. 11 . 
       FIG. 11  is a flowchart illustrating the bearer data transfer in the bearer data processing device according to the embodiment of the present invention. In Step  3002 , the encapsulation/decapsulation processing unit  3015  determines whether a protocol type present in the IP header of the received data is GRE, or not. If yes, the operation proceeds to Step  3003  whereas if no, the operation proceeds to Step  3011 . In Step  3003 , the encapsulation/decapsulation processing unit  3015  extracts the GRE KEY included in the GRE header of the received data. After extraction of the GRE KEY, the operation proceeds to Step  3004 . In Step  3004 , the MS is specified with the use of the table in  FIG. 6 . For example, if the extracted GRE KEY is 0xFFFF0001, the encapsulation/decapsulation processing unit  3015  searches a row of the up link GRE KEY in  FIG. 6  for searching the matched index, and acquires the matched index. Information related to the MS such as the MS IP address and the connection type are present on the row of the same index. After specifying the MS, the encapsulation/decapsulation processing unit  3015  allows the operation to proceed to Step  3005 , and conducts GRE decapsulation processing to eliminate the GRE capsuling. 
       FIG. 13  is a diagram illustrating the GRE decapsulation processing. 
     In the GRE decapsulation processing, the encapsulation/decapsulation processing unit  3015  removes an IP header  7066  and a GRE header  7067  from the CRE capsuling data which is received data indicated on an upper stage of  FIG. 13 , extracts user data  7068 , and allows the operation to proceed to Step  3006 . In Step  3006 , the encapsulation/decapsulation processing unit  3015  measures the number of bytes of the user data  7068 , and notifies the accounting statistics collection unit  3013  of the index and the number of bytes acquired in Step  3004 . 
       FIG. 8  is a diagram illustrating an example of a table that stores statistics information necessary for accounting in the bearer data processing device. The accounting statistics collection unit  3013  adds the notified number of bytes to the number of up link bytes in the statistics information table in  FIG. 8  corresponding to the notified index, and adds +1 to the number of up link packets. 
     After addition, the operation proceeds to Step  3007 . In Step  3007 , the encapsulation/decapsulation processing unit  3015  determines whether the connection type is the simple IP or the mobile IP. If the connection type is the simple IP, the encapsulation/decapsulation processing unit  3015  transfers the user data to the I/O port  3014 , and allows the operation to proceed to Step  3009 . If the connection type is the mobile IP, the encapsulation/decapsulation processing unit  3015  allows the operation to proceed to IPinIP encapsulating processing S 3008  of Step  3008 . 
       FIG. 7A  is a diagram illustrating the IPinIP encapsulation processing. 
     In the IPinIP encapsulation processing, an IP header  7100  is allocated to the user data  7068  extracted in the GRE decapsulating processing capsulation processing  3005  indicated on an upper stage of  FIG. 7A . The HA IP address is set to the destination IP address  7101  of the allocated IP header, and the IP address of the GW-EP  301  is set to a source IP address  7102 . After conducting the IPinIP encapsulating processing, the encapsulation/decapsulation processing unit  3015  transfers the user data to the I/O port  3014 , and allows the operation to proceed to Step  3009 . In Step  3009 , the encapsulation/decapsulation processing unit  3015  conducts appropriate routing processing, and transmits the data to the network  5002 . If the network  5002  is connected to the internet  501 , the data is transferred to the internet  501  in conformity with a normal IP routing. 
     On the other hand, when the user data of down link which is transmitted from the internet  501  to the MS  700  arrives at the GW-EP  301 , the user data is transferred to the encapsulation/decapsulation processing unit  3015  through the I/O port  3014 , and the routing processing of  FIG. 11  is executed. In Step  3002 , the encapsulation/decapsulation processing unit  3015  checks whether the protocol type of the IP header is the GRE, or not. Because the data received from the internet  501  is not the GRE capsuling data, the determination is no, and the operation proceeds to Step  3011 . In Step  3011 , the encapsulation/decapsulation processing unit  3015  checks whether the protocol type of the IP header is IPinIP, or not. This is different depending on whether the connection type is the mobile IP or the simple IP, and if the connection type is the mobile IP, the check determination is yes, and the operation proceeds to IPinIP decapsulation processing in Step  3012 . 
       FIG. 7B  is a diagram illustrating the IPinIP decapsulation processing. 
     In the IPinIP decapsulation processing, the encapsulation/decapsulation processing unit  3015  removes an IP header  7110  from an IPinIP packet indicated on an upper stage of  FIG. 7B , and extracts user data  7078 . After extraction of the user data, the operation proceeds to Step  3013 . In the encapsulation/decapsulation processing unit  3015 , if the connection type is the simple IP, the determination in Step  3011  is no, and the operation proceeds to Step  3013 . In Step  3013 , the encapsulation/decapsulation processing unit  3015  searches the IP address that matches the destination address of the IP header from the table of  FIG. 6 . If there is the matched IP address, the encapsulation/decapsulation processing unit  3015  acquires the index corresponding to the matched MS IP address, and allows the operation to proceed to Step  3014 . In Step  3014 , the encapsulation/decapsulation processing unit  3015  measures the number of bytes of the received data for statistics collection that is a base of accounting, and notifies the accounting statistics collection unit  3013  of the number of bytes and the index acquired in Step  3013 . The accounting statistics collection unit  3013  adds the notified number of bytes to the number of down link bytes in the table of  FIG. 8 , which corresponds to the index number, and increments the counter of the number of down link packets by +1. Upon completion of down link data amount collection  3014 , the operation proceeds to Step  3015 . 
       FIG. 14  is a diagram illustrating GRE encapsulation processing. 
     In the GRE encapsulation processing of Step  3015 , the encapsulation/decapsulation processing unit  3015  allocates a GRE header  7077  and an IP header  7076  to the received user data  7078  as illustrated in  FIG. 14 . The GRE KEY of the GRE header  7077  allocates the down link GRE KEY corresponding to the index acquired in Step  3013 . Upon completion of the GRE encapsulation processing, the encapsulation/decapsulation processing unit  3015  transfers the GRE capsuling data to the I/O port  3014 , and allows the operation to proceed to Step S 3009 . In Step  3009 , the encapsulation/decapsulation processing unit  3015  transfers the data to the BS  600  according to the routing information. 
     The BS  600  transfers the data received from the GW-EP  301  to the MS  700  as the radio data  7100 . 
     Subsequently, a disconnection sequence will be described. 
       FIG. 15  is a diagram illustrating an example of the disconnection sequence. 
     When the connection is to be disconnected, the MS  700  transmits a DRG-REQ  840  that is a request for disconnection to the BS  600 . The reception of the DRG-REQ  840  leads the BS  600  to execute a disconnection sequence (Path_Dereg_Req.  842 , Path_Dereg_Rsp.  843 , Path_Dereg_Ack  844 ) between the BS  600  and the GW-DP  201 . The GW-DP  201  conducts the disconnection sequence from the BS  600 , and at the same time, if the connection type is the mobile IP, disconnects a mobile IP path  846  from the CSN  400 . The GW-DP  201  transmits a setup cancel request  847  to the GW-EP  301 . A format of the setup cancel request  847  is identical with the format of the setup request illustrated in  FIG. 12 , and whether the format is of the setup request or the setup cancel request is distinguished by the contents of the type  8313 . The information elements  8310  of the setup cancel request include the MS IP addresses, and the control unit  3011  of the GW-EP  301  that receives the setup cancel request  847  searches the table in  FIG. 6 , and clears information on the matched index. After clearing, the control unit  3011  acquires the number of down link bytes, the number of up link bytes, the number of down link packets, and the number of up link packets in  FIG. 8  corresponding to the index, from the accounting statistics collection unit  3013  of the GW-EP  301 , sets those acquired numbers for the information elements  8310  of a setup cancel response  848 , and transmits the information elements  8310  to the GW-DP  201 . 
     The GW-DP  201  that has received the setup cancel response  848  extracts the number of down link bytes, the number of up link bytes, the number of down link packets, and the number of up link packets, which are stored in the setup cancel response  848 , and stores those extracted numbers in a given attribute of an Accounting-Request (stop)  849 , and transmits the stored numbers to the CSN  400 . Upon receiving the accounting-Request (stop)  849 , the CSN  400  transmits an Accounting-Response  850  to the GW-DP  201 . 
     Because the MS  700  can access to the GW-EP  301  connected to the network  5002  close to the BS  600  through the internet  501 , traffic can be prevented from being converted on the network  5001 . Also, during disconnection, the statistics information is transmitted from the GW-EP to the GW-DP  200 , to thereby enable information necessary for accounting to be notified the CSN  400  of. 
     B. Second Embodiment 
     In a second embodiment, a description will be given of another method of the BS management table in the GW-EP search flowchart of  FIG. 10 .  FIG. 16  illustrates a table held by the EP-GW position management unit  2004  in the GW-DP  201  of  FIG. 2 . This table includes items of the index, the BS network address, and the area, and specifies the area for each of the BS network addresses. The connection sequence of the MS is the sequence of  FIG. 9  which is identical with that of the first embodiment. The GW-DP  201  receives the MS_PreAttachment_Req.  801  transmitted from the BS  600  to implement the GW-EP search processing  830 . 
       FIG. 10  is a flowchart illustrating allocation processing of the bearer data processing device according to the embodiment of the present invention. In the GW-EP search processing  830 , the flowchart of  FIG. 10  is implemented, and in Step  2002 , the GW-DP  201  extracts the BS IP address of the MS_PreAttachment_Req.  801  in the same method as that of the first embodiment. For example, it is assumed that the BS IP address extracted in Step  2002  is 192.168.20.25. Upon completion of the extraction, the GW-DP  201  allows the operation to proceed to Step  2003 , and specifies the area. The table of  FIG. 16  is used for specifying the area. 
       FIG. 16  is a diagram illustrating an example of the BS position management table according to the embodiment of the present invention. Areas corresponding to the BS network addresses are set in the table of  FIG. 16 . When the BS IP address is 192.168.20.25, it is found by searching a BS network address column that the BS IP address is included in a network address of 192.168.20.0/24 in index 2. The area on the same row as that of the matched index is an obtained area. In the case of the index 2, an area 2 is obtained. After the area could be specified, the GW-DP  201  allows the operation to proceed to Step  2004 , and the subsequent steps are identical with those in the first embodiment. 
     The advantage of the second embodiment resides in that the BS IP network address can be used as the BS management table to reduce the number of table setting. 
     C. Third Embodiment 
     In a third embodiment, a description will be given of another method in the GW-EP search processing of  FIG. 9 . 
       FIG. 17  illustrates a format of a BSID. The BSID is an identifier specified for identifying the BS, and in this example, has a length of 48 bits. High-order 24 bits  6001  are specified by an operator ID or an NAP ID and the standards of WiMAX forum. Low-order 24 bits can be used for identifying the BS. A first bit  6002  is specified as a determination flag to determine whether low-order 23 bits are intended for an NSP or for identifying the BS. In the third embodiment, 7 bits of 23 bits  6003  used for the BS identification are used as an area ID 6004. The 7 bits used as the area ID are made to match the area number. For example, when the area ID is 0000001, the area ID indicates an area 1. 
     The MS connection sequence in the third embodiment will be described with reference to  FIG. 9 . As in the first embodiment, the GW-DP  201  receives the MS_PreAttachment_Req.  801  transmitted from the BS  600  to implement the GW-EP search processing  830 . The MS_PreAttachment_Req.  801  includes the BSID. 
       FIG. 18  is a flowchart illustrating the allocation processing in the bearer data processing device according to the embodiment of the present invention. In the GW-EP search processing  830 , the flowchart of  FIG. 18  is implemented. In Step  2012 , the GW-DP  201  extracts the BSID. In the MS_PreAttachment_Req.  801 , the BSID is included in the message, and the GW-DP  201  extracts the BSID of 48 bits. As an example, it is assumed that the extracted BSID is 000100 010345(HEX). After extraction of the BSID, the operation proceeds to Step  2013 . It is found that the bit corresponding to the area ID of the above-mentioned extracted BSID is 01, and it is found that the BS is located in the area 1. After specifying the area, the GW-DP  201  specifies the GW-EP IP address with the use of the table 5 in  FIG. 5  as in the first embodiment. Thereafter, the same processing as that in the first embodiment is conducted. 
     The advantage of the third embodiment resides in that the BS management information can be reduced by setting the area information for the BSID. 
     D. Fourth Embodiment 
     In a fourth embodiment, a description will be given of another method in the GW-EP search processing of  FIG. 9 . 
       FIG. 19  illustrates a table held by the EP-GW position management unit  2004  in the GW-DP  201  of  FIG. 2 . The table includes items of the index, the BS IP address, and the GW-EP IP address. 
     The connection sequence of the MS is the sequence of  FIG. 9  which is identical with that of the first embodiment. The GW-DP  201  receives the MS_PreAttachment_Req.  801  transmitted from the BS  600  to implement the GW-EP search processing  830 . 
       FIG. 20  is a flowchart illustrating the allocation processing in the bearer data processing device according to the embodiment of the present invention. In the GW-EP search processing  830 , the flowchart of  FIG. 20  is implemented. In Step  2022 , the GW-DP  201  extracts the BSIP in the same method as that of the first embodiment. After extraction of the BSIP address, the operation proceeds to Step  2023 . In Step  2023 , the GW-DP  201  searches the extracted BSIP address on a column of the BSIP address of the table in  FIG. 19 , and acquires the GW-EP IP address on the same row as that of the matched index. For example, when the BS IP address is 192.168.10.2, the BS IP address matches an index 1, and acquires a corresponding GW-EP IP address 192.168.200.10. After acquiring the GW-EP IP address, the GW-DP  201  allows the operation to proceed to Step  2034 , and executes the sequence of  FIG. 9  as in the same manner as that of the first embodiment. 
     Also, as the same BS management method, the management can be achieved by the BSID instead of the BS IP address.  FIG. 21  illustrates a management table that associates the BSID with the GW-EP IP address. Also,  FIG. 22  illustrates a GW-EP search flowchart. A difference from  FIG. 20  resides in that the GW-EP address is searched on the basis of the BSID. 
     The GW-EP and/or the GW-DP can be configured by using an appropriate router or computer. 
     Also, the present invention has been described by exemplifying the GW-EPs and the GW-DP, but can be applied to an appropriate bearer data processing device or signaling processing device. The present invention is not limited to the GRE and the GRE KEY, but can be applied to appropriate encapsulation/decapsulation and a key (capsuling key) necessary for the encapsulation/decapsulation.