Patent Publication Number: US-10791473-B2

Title: Wireless communication system, base station device, move control node, and method of wireless communication

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation application of U.S. application Ser. No. 16/269,176 filed Feb. 6, 2019, which is a continuation application of U.S. application Ser. No. 15/912,507 filed Mar. 5, 2018 (now U.S. Pat. No. 10,271,230 issued Apr. 23, 2019), which is a continuation application of U.S. application Ser. No. 15/419,980 filed Jan. 30, 2017 (now U.S. Pat. No. 9,949,150 issued Apr. 17, 2018), which is a continuation application of U.S. application Ser. No. 14/969,128 filed Dec. 15, 2015 (now U.S. Pat. No. 9,615,323 issued Apr. 4, 2017), which is a continuation application of U.S. patent application Ser. No. 12/865,190 filed on Jul. 29, 2010, which is a National Stage Entry of international application PCT/JP2009/051578, filed on Jan. 30, 2009, which claims priority from Japanese Patent Application No. 2008-021304 filed on Jan. 31, 2008, the disclosures each of which are incorporated by reference herein in their entireties. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a wireless communication system, a base station, a mobility management node, and a wireless communication method. 
     BACKGROUND ART 
     According to LTE (Long Term Evolution) that is being standardized in 3GPP (3rd Creation Partnership Projects) at present, there has been proposed a wireless communication system which includes EUTRAN (Evolved UMTS Terrestrial Radio Access Network, UMTS=Universal Mobile Telecommunication System) and EPC (Evolved Packet Core) that are configured as shown in  FIG. 1  (4.2.1 of Non-patent document 1, FIGS. 4.2.1-1 and 4.2.1-2 of Non-patent document 2). The above titles are not restrictive, but EUTRAN may be called “LTE”, EPC may be called SAE (System Architecture Evolution), and EUTRAN and EPC may collectively be called EPS (Evolved Packet System). 
     As shown in  FIG. 1 , the EUTRAN includes eNode B (evolved Node B)  10  as a base station. The EPC includes CN (Core Network) Nodes comprising MME (Mobility Management Entity)  20  as a mobility management node, S-GW (Serving Gateway)  30  as a gateway, P-GW (Packet Data Network Gateway)  40  as a higher-level gateway, and HSS (Home Subscriber Server)  50 . eNode  10  is connected to UE (User Equipment) as a wireless communication apparatus through a wireless interface. 
     MME  20  is a node having a mobility management (location registration) function for UE  60 , a handover control function, a selection function for S-GW  30  and P-GW  40 , a bearer management function, etc (4.4.2 of Non-patent document 1). S-GW  30  is a node for transferring user-plane packet data between eNode B  10  and P-GW  40 . P-GW  40  is a node for transferring transmission packet data from its own network (Home PLMN, PLMN=Public Land Mobile Network) to an external network (Visit PLMN) and transferring reception packet data from an external network to its own network. HSS  50  is a server for saving user information that is used to authenticate UE  60 . 
     According to LTE, TAs (Tracking areas) are assigned to UE  60  as areas in which UE  60  is to be paged when an incoming call is received (5.2.3 of Non-patent document 1). Specifically, when UE  60  registers its location in eNode B  10 , TAs are assigned to UE  60  by MME  20 , and the list of assigned TAs is registered in UE  60 . If UE  60  detects when it has moved to a TA that is not included in the registered list, UE  60  registers its location again in eNode B  10  in order to update the TAs (5.3.3.1 of Non-patent document 1). 
     In a region where the paging traffic is high, the number of TAs that are assigned to UE  60  when UE  60  registers its location is reduced in order to reduce the number of areas in which UE  60  is to be paged. In order to reduce the number of times that UE  60  registers its location, on the other hand, the number of TAs assigned to UE  60  which is moving at a high speed is increased. 
     Consequently, there is a trade-off between the number of TAs for reducing the paging traffic and the number of TAs for reducing the number of times that UE  60  registers its location. It is thus necessary to optimize the number of TAs assigned to UE  60  in view of the trade-off. 
     A general process of assigning TAs to UE  60  will be described below. 
     It is assumed that from among the respective cells of a plurality of eNodes B  10 , cells C #1 through C #23 are arranged as shown in  FIG. 2 , and cells C #1 through C #23 belong to TA #1 through TA #7 as follows: 
     TA #1=C #1, C #2, C #3, C #4, C #5 
     TA #2=C #17, C #18. C #19, C #20, C #21. C #22 
     TA #3=C #6, C #7, C #8 
     TA #4=C #9, C #10, C #12, C #13, C #14 
     TA #5=C #16 
     TA #6=C #11, C #15 
     TA #7=C #23 
     Generally, MME  20  assigns TAs to UE  60  according to a rule that is manually established by the operator. According to the rule, a plurality of TAs are fixedly assigned to UE  60 . 
     Specifically, in the example shown in  FIG. 2 , the rule is such that when UE  60  registers its location in either one of eNodes B  10  of the cells belonging to TA #1, two TAs represented as TA #1 and TA #4 are fixedly assigned to UE  60 . 
     Even when UE  60 , which is moving at a high speed, registers its location in either one of eNodes B  10  of the cells belonging to TA #, TA #1 and TA #4 are assigned to UE  60 . 
     If the cells belonging to TA #1 and TA #4 are of the type which covers a very small range (having a radius of several hundreds meters), for example, then even though MME  20  assigns TA #1 and TA #4 to UE  60 , since UE  60  travels through TA #1 and TA #4 and enters TA #5 in several seconds, UE  60  needs to newly register its location. 
     The time which UE  60  takes to travel through TA #1 and TA #4 will be actually calculated as described below. 
     It is assumed that UE  60  registers its location in eNode B  10  of C #2 belonging to TA #1, the cells belonging to TA #1 and TA #4 have a diameter of 500 m (meter), and UE  60  travels at a speed of 80 km (kilo meter)/h (hour). 
     The distance over which UE  60  travels through TA #1 and TA #4 is 2500 in (meter) across five cells (C #2, C #3, C #5, C #12, C #13) (=500 m*5). 
     Therefore, the time which UE  60  takes to travel through TA #1 and TA #4 is 113 seconds (≈2500 m/80 km/h). This numerical value indicates that UE  60  will do its location registration in about two minutes. Therefore, the number of times that UE  60  registers its location cannot be reduced. 
     Since the number of times that UE  60  registers its location cannot be reduced, an optimum number of TAs cannot be assigned to UE  60 . 
     According to the practice of fixedly assigning a plurality of TAs to UE  60 , a plurality of TAs are also assigned to UE  60  which mostly does not move in daytime. Consequently, since the paging traffic for paging UE  60 , when an incoming call is received, has to cover the plural TAs, the paging traffic cannot be reduced, resulting in a large burden imposed on the wireless communication system. 
     As described above, the practice of fixedly assigning a plurality of TAs to UE  60  is problematic in that an optimum number of TAs cannot be assigned to UE  60 . 
     Furthermore, in as much as the operator manually sets the rule for assigning TAs to UE  60  in MME  20 , the rule has to be re-established each time eNode B  10  is added or removed. This requires the operator to spend a lot of time and make a lot of effort, and hence results in an increase in OPEX (Operation and Expenditure). 
     Non-patent document 1: 3GPP TS 23.401, V8.0.0 
     Non-patent document 2: 3GPP TS 36.300, V8.2.0 
     DISCLOSURE OF THE INVENTION 
     It is an object of the present invention to provide a wireless communication system, a base station, a mobility management node, and a wireless communication method which are capable of solving at least one of the above problems. 
     A wireless communication system according the present invention comprises a base station and a mobility management node, wherein 
     said base station sends at least one information from among location information of the base station and information about the size of a cell of the base station, to said mobility management node; and 
     said mobility management node receives at least one information from among the location information of the base station and the information about the size of the cell of the base station, from said base station. 
     A base station according to the present invention comprises a transmitter for sending at least one information from among location information of a base station and information about the size of a cell of the base station, to a mobility management node. 
     A first mobility management node according to the present invention comprises a receiver for receiving at least one information from among location information of a base station and information about the size of a cell of the base station, from said base station. 
     A second mobility management node according to the present invention comprises: 
     a receiver for receiving, from a base station, information about movement of a wireless communication apparatus which registers its location in said base station; and 
     a controller for assigning a tracking area based on information about a layout of said base station and the information about movement. 
     According to the present invention, a first wireless communication method to be carried out by a base station, comprises: 
     the transmission step of sending at least one information from among location information of the base station and information about the size of a cell of the base station, to a mobility management node. 
     According to the present invention, a second wireless communication method to be carried out by a mobility management node comprises the reception step of receiving, from a base station, at least one information from among location information of the base station and information about the size of a cell of the base station. 
     According to the present invention, the base station is arranged to send at least one information from among the location information of the base station and the information about the size of the cell of the base station, to the mobility management node. 
     Therefore, since the mobility management node can recognize a layout of cells by receiving at least one information from among the location information of the base station and the information about the size of the cell thereof, the OPEX required by manual operation of the operator for assigning tracking areas can be reduced, and it is possible to assign an optimum number of tracking areas to the wireless communication apparatus. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram showing the overall configuration of a wireless communication system; 
         FIG. 2  is a diagram showing another example of a map representing the layout of cells; 
         FIG. 3  is a block diagram showing the configuration of a wireless communication system according to a first exemplary embodiment of the present invention; 
         FIG. 4  is a sequence diagram illustrating an operation of the wireless communication system according to the first exemplary embodiment of the present invention; 
         FIG. 5  is a block diagram showing the configuration of a wireless communication system according to a second exemplary embodiment of the present invention; 
         FIG. 6  is a sequence diagram illustrating an operation of the wireless communication. 
     
    
    
     system according to the second exemplary embodiment of the present invention at the time eNode B is added; 
       FIG. 7  is a diagram showing an example of a map representing the layout of cells; 
       FIG. 8  is a sequence diagram illustrating an operation of the wireless communication system according to the second exemplary embodiment of the present invention at the time a range covered by the cell of eNode B is changed; 
       FIG. 9  is a flowchart of an operation sequence of MME when it assigns TAs according to the second exemplary embodiment of the present invention; 
       FIG. 10  is a flowchart of a processing sequence for calculating a TA range in steps  706 ,  712  shown in  FIG. 9 ; 
       FIG. 11  is a sequence diagram illustrating an operation of a wireless communication system according to a third exemplary embodiment of the present invention at the time the UE is attached; and 
       FIG. 12  is a sequence diagram illustrating an operation of a wireless communication system according to a fourth exemplary embodiment of the present invention at the time the LIE registers its location. 
     BEST MODE FOR CARRYING OUT THE INVENTION 
     The best mode for carrying out the present invention will be described below with reference to the drawings. 
     In all exemplary embodiments to be described below, the overall configuration of a wireless communication system is identical to the overall configuration of the wireless communication system shown in  FIG. 1 . 
     First Exemplary Embodiment 
     As shown in  FIG. 3 , eNode B  10  according to the present exemplary embodiment includes transmitter  11  for transmitting location information of the cell of eNode B  10  and information about the size thereof to MME  20 . 
     MME  20  according to the present exemplary embodiment includes receiver  21  for receiving the location information of the cell of eNode B  10  and the information about the size thereof from eNode B  10 . 
     Operation of the present exemplary embodiment will be described below with reference to  FIG. 4 . 
     As shown in  FIG. 4 , in step  201 , transmitter  11  of eNode B  10  sends the location information of the cell of eNode B  10  and the information about the size thereof to MME  20 . The information sent to MME  20  is received by receiver  21  of MME  20 . 
     Since MME  20  can recognize the layout of cells by receiving the location information of the cell of eNode B  10  and the information about the size thereof, the OPEX required by manual operation of the operator for assigning TAs can be reduced, and it is possible to assign an optimum number of TAs to UE  60 . 
     Second Exemplary Embodiment 
     As shown in  FIG. 5 , eNode B  10  according to the present exemplary embodiment is different from eNode B 10  according to the first exemplary embodiment shown in  FIG. 3  in that receiver  12  and controller  13  are added thereto. 
     Controller  13  includes information about eNode B  10 , described below, in a, message. 
     (1) Location information of the cell of eNode B  10 : 
     For example, the location information of the cell is the information of latitude and longitude of the location of the cell of eNode B  10  (e.g., the central location of the cell or the central location of eNode B  10 ), which is acquired by a location information measuring device on eNode B  10  using a GPS (Global Positioning System) or the like. The location information of the cell may be information required to calculate the location, which is acquired by eNode B  10  using the GPS or the like. 
     (2) Information about the size of the cell of eNode B  10 : 
     For example, the size of the cell may represent the diameter or radius of the cell (e.g., 500 m, 1 km, or 2 km). Alternatively, the size of the cell may represent a type indicative of the size of the cell (e.g., Macro, Micro, Pico, or Femto). 
     (3) TA to which the cell of eNode B  10  belongs: 
     (4) The eNode B  10  number or the cell number of eNode B  10 : 
     The information (2) through (4) is preset in eNode B  10 . 
     The transmitter  11  sends a message including information (1) through (4) with respect to eNode B  10  to MME  20 . 
     Receiver  12  receives a message including the information of TAs assigned to UE  60  which has registered its location in its own eNode B  10 , from MME  20 . 
     Messages are also se and received from UE  60  by transmitter  11 , receiver  12 , and controller  13 . 
     MME  20  according to the present exemplary embodiment is different from MME  20  according to the first exemplary embodiment shown in  FIG. 3  in that transmitter  22  and controller  23  are added thereto. 
     Receiver  21  receives the message including the information (1) through (4) with respect to eNode B  10  from eNode B  10 . 
     Controller  23  creates a map representative of the layout of cells based on the information (1) through (4) with respect to eNode B  10 . 
     Controller  23  dynamically assigns an optimum number of TAs to UE  60  which has registered its location in eNode B  10 , based on the moving speed and moving direction of UE  60  and the map, and includes the information of the assigned TAs in a message. 
     Transmitter  22  sends the message including the information of the TAs assigned to LIE  60  which has registered its location in eNode B  10 , to eNode B  10 . 
     Messages are also sent to and received from S-GW  30  by transmitter  22 , receiver  21 , and controller  23 . 
     Operation of the present exemplary embodiment will be described below. 
     In order for the wireless communication system to provide communication services stably and optimally, it adds, removes, and redeploys eNode B  10  depending on the traffic volume in a certain region and the place such as between buildings where a wireless signal from existing eNode B  10  does not reach. 
     [When eNode B  10  is Added] 
     Operation at the time eNode B  1 . 0  is added will be described with reference to  FIG. 6 . 
     It is assumed that, as shown in  FIG. 7 , C #30 belonging to TA #1 is newly added to the cell layout shown in  FIG. 2 . 
     As shown in  FIG. 6 , eNode B  10  of C #30 added to TA #1 is newly added in step  401 . 
     In step  402 , transmitter  11  of added eNode B  10  sends a setup message (S1 setup message) including the information (1) through (4) with respect to eNode B  10  to MME  20 . 
     Then, in step  403 , controller  23  of MME  20  calculates the range of TA #3 based on the location information of C #1 through C #5, C #30 belonging to TA #1, creates a new map as shown in  FIG. 7 , and stores the new map in a memory (not shown in any of the figures). 
     Thereafter, in step  404 , transmitter  22  of MME  20  sends a response message to the setup message (S1 Setup Response message) to eNode B  10 . 
     [When eNode B  10  is Removed] 
     When eNode B  10  is removed, the cell of removed eNode B  10  is deleted. Therefore, MME  20  cannot receive a notice from removed eNode B  10 . However, when eNode B  10  is removed, the connection link between removed eNode B  10  and MME  20  is cut off. 
     Controller  23  of MME  20  judges eNode B  10  whose connection link to its own MME  20  has been cut off as being removed, deletes the cell of removed eNode B  10  from the map, creates a new map, and stores the new map in the memory (not shown in any of the figures). 
     [When the Range Covered by the Cell of eNode B  10  is Changed] 
     Operation at the time the range covered by the cell of eNode B  10  is changed will be described below with reference to  FIG. 8 . 
     As shown in  FIG. 8 , in step  601 , the range covered by the cell of eNode B  10  is changed because of a redeployment or configurational change (replacement of the antenna, a change in the antenna direction, etc.) of eNode B  10 . 
     In step  602 , transmitter  11  of eNode B  10  with the cell-covered range being changed sends a reconfiguration message (S1 Reconfiguration message) including information (1) through (4) with respect to eNode B  10  to MME  20 . 
     Then, in step  603 , controller  23  of MME  20  calculates the range of the TA, to which the cell with the range covered thereby being changed belongs, creates a new map, and stores the new map in the memory (not shown in any of the figures). 
     Thereafter, in step  604 , transmitter  22  of MME  20  sends a response message (S1 Reconfiguration Response message) to the reconfiguration to eNode B  10 . 
     [When the Location of UE  60  is Registered] 
     When the location of UE  60  is registered (TA Update), controller  23  of MME  20  assigns an optimum number of TAs to UE  60  based on the moving speed Sue and moving direction Dir of UE  60 . 
     (A) Calculation of the Moving Speed Sue of UE  60 : 
     For example, the moving speed Sue of UE  60  can be calculated from a change in the number of TAs assigned when the location of UE  60  is registered within a certain period. Specifically, if the number of TAs has increased, then the moving speed of UE  60  is judged as high. Conversely, if the number of TAs has decreased, then the moving speed of UE  60  is judged as low. Information of the moving speed of UE  60  may acquired by other methods. For example, MME  20  can receive the information of the moving speed which is recognized by UE  60  from UE  60  via eNode B  10 . 
     (B) Calculation of the Moving Direction Dir of UE  60 : 
     For example, the moving direction Dir of UE  60  can be calculated from the track of registered locations of UE  60  within a certain period. Information of the moving direction Dir of UE  60  may acquired by other methods. For example, MME  20  can receive the information of the moving direction which is recognized by UE  60  from UE  60  via eNode B  10 . 
     (C) Assignment of TAs to UE  60 : 
     When TAs are assigned to UE  60 , they are assigned such that it takes UE  60  six minutes or more, for example, to travel through all the assigned TAs. The time that UE  60  takes to travel through all the assigned TAs is not limited to six minutes, but may be determined appropriately depending on the design of the system. 
     Specific Example 1 
     It is assumed that, as shown in  FIG. 7 , UE  60  registers its location in eNode B  10  of C #2 belonging to TA #1, the cells belonging to TA #1 and TA #4 have a diameter of 2 km. UE  60  has a moving speed Sue of 80 km/h, and UE  60  has a moving direction Dir from TA #1 to TA #4. 
     If two TA #1 and TA #4 are assigned to UE  60 , then the distance over which UE  60  travels through TA #1 and TA #4 is 10 km across five cells (C #2, C #3, C #5, C #12, C #13) (=2 km*5). Therefore, the time which UE  60  takes to travel through TA #1 and TA #4 is 7.5 minutes (≈10 km/80 km/h). Since it takes UE  60  six minutes or more to travel through TA #1 and TA #4, two TA #1 and TA #4 are assigned to UE  60 . 
     Specific Example 2 
     It is assumed that, as shown in  FIG. 7 , UE  60  registers its location in eNode B  10  of C #2 belonging to TA #1, the cells belonging to TA #1 and TA #4 have a diameter of 1.5 km,  60  has a moving speed Sue of 80 km/h, and UE  60  has a moving direction Dir from TA #1 to TA #4. 
     If two TA #1 and TA #4 are assigned to UE  60 , then the distance over which UE  60  travels through TA #1 and TA #4 is 7.5 km across five cells (C #2, C #3, C #5, C #12, C #13) 1.5 km*5). Therefore, the time which UE  60  takes to travel through TA #1 and TA #4 is 5.6 minutes (≈7.5 km/80 km/h). It does not take UE  60  six minutes or more to travel through TA #1 and TA #4. 
     If three TA #1, TA #4, and TA #5 are assigned to UE  60  and the distance and the time are recalculated, then the time which UE  60  takes to travel through TA #1, TA #4, and TA #5 is 6.8 minutes (≈9.0 km/80 km/h). Since it takes UE  60  six minutes or more to travel through TA #1, TA #4, and TA #5, three TA #1, TA #4, and TA #5 are assigned to UE  60 . 
     Specific Example 3 
     It is assumed that UE  60  registers its location in eNode B  10  of C #2 belonging to TA #1, as is the case with the above examples, but UE  60  has a moving speed Sue of 0 km/h. 
     It may be considered that UE  60  is in a company or the like and mostly does not move in daytime. Therefore, only one TA #1, to which C #2 of eNode B  10 , in which UE  60  has registered its location belongs, is assigned to UE  60 . As only one TA is assigned to UE  60  that mostly does not move in daytime, the paging traffic for paging UE  60 , when an incoming call is received, covers only TA #1, the paging traffic is reduced and no burden is imposed on the wireless communication system. 
     The above process of assigning TAs to UE  60  is described below. 
     As shown in  FIG. 9 , when UE  60  registers its location in eNode B  10 , controller  23  of MIME  20  calculates a moving speed Sue of UE  60  in step  701 . If the moving speed Sue is 0 in step  702 , then controller  23  assigns one TA, to which the cell of eNode B  10 , in which UE  60  has registered its location, belongs to UE  60  in step  703 . 
     If the moving speed Sue is not 0 in step  702 , then controller  23  calculates a moving direction Dir of UE  60  in step  704 , and then calculates a range of present TA (TA to which the cell of eNode B  10 , in which UE  60  has registered its location, belongs) in step  705 . 
     In the above exemplary embodiment, the range of TA is calculated if the moving speed Sue is not 0. However, the range of TA may be calculated if the moving speed Sue is equal to or higher than a predetermined speed, not 0. 
     The range of TA is calculated as shown in  FIG. 10 . 
     As shown in  FIG. 10 , the controller  23  sets, as x, the number of cells, of the cells belonging to TA, that are arrayed along the moving direction Dir of UE  60  in step  801 . 
     Then, controller  23  sets, as n, a next cell number (a first cell number when control comes from step  801 ) in step  802 , and then sets, as Dn, the diameter of cell n set in step  802  in step  803 . At this time, the diameter of the cell received as the information in above (2) from eNode B  10  is used as the diameter of cell n. If the information in above (2) received from eNode B  10  represents the radius or type of the cell, then the diameter of the cell is determined based on the received information. 
     Then, controller  23  sets the sum of present TAd (0) when control comes from step  801 ) and Dn set in step  803  as TAd representative of the range covered by TA, in step  804 . 
     Then, controller  23  sets, as new x, the difference produced by subtracting 1 from the present x in step  805 . If x is 0 in step  806 , then controller  23  stores TAd set in step  804  in the memory (not shown in any of the figures) in step  807 . 
     If x is not 0 in step  806 , then control goes back to step  802 , and the same processing is repeated until x becomes 0. 
     Therefore, the range TAd covered by TA is expressed by the equation 1 below where n represents the cell number. 
     
       
         
           
             
               
                 
                   TAd 
                   = 
                   
                     
                       ∑ 
                       1 
                       n 
                     
                     ⁢ 
                     Dn 
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   [ 
                   1 
                   ] 
                 
               
             
           
         
       
     
     Referring back to  FIG. 9 , controller  23  sets, as TAd, the present range of TA calculated in step  705 , and also sets, as TAdm, an initial value 0 in step  706 . Controller  23  then sets the sum of TAd and TAdm set in step  706  as new TAd in step  707 . 
     Then, in step  708 , controller  23  determines travel time T which UE  60  takes to travel through TA by dividing TAd newly set in step  707  by moving speed Sue calculated in step  701 . 
     Therefore, travel time T of UE  60  is expressed by equation 2 below where in represents the TA number. 
     
       
         
           
             
               
                 
                   T 
                   = 
                   
                     
                       [ 
                       
                         
                           ∑ 
                           1 
                           m 
                         
                         ⁢ 
                         
                           TAd 
                           ⁡ 
                           
                             ( 
                             m 
                             ) 
                           
                         
                       
                       ] 
                     
                     ÷ 
                     Sue 
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   [ 
                   2 
                   ] 
                 
               
             
           
         
       
     
     Then, if travel time T calculated in step  708  exceeds a predetermined time of X minutes (a time required for UE  60  to travel through all the assigned TAs) in step  709 , then controller  23  assigns the present TAs to UE  60  in step  710 . 
     If travel time T calculated in step  708  is equal to or shorter than the X minutes in step  709 , then controller  23  sets, as new TAdm, TAd(m+1) representing a range covered by next TA along the moving direction of UE  60  in step  711 . Then, in step  712 , controller  23  calculates TAdm newly set in step  711 . Control then goes back to step  707 , and the same processing is repeated until travel time T exceeds the X minutes. 
     In the present exemplary embodiment described above, the moving speed Sue and the moving direction Dir are used as the information with respect to the movement of UE  60 . However, either the moving speed Sue or the moving direction Dir may be used in the present invention. For example, if only the moving speed Sue is used, then TAs that are present around the location of UE  60  may be assigned. If only the moving direction Dir is used, then a given number TAs along that direction may be assigned. 
     According to the present exemplary embodiment, as described above, when eNode B  10  is added or when the range that is covered by the cell is changed, eNode B  10  sends a message including the location information of the cell of its own and the information about the size thereof to MME  20 . 
     Therefore, MME  20  can recognize the layout of cells based on the location information of the cell of eNode B  10  and the information about the size thereof, and hence can dynamically assign an optimum number of TAs to UE  60 , as is the case with the first exemplary embodiment. 
     Furthermore, MME  20  is also capable of assigning an optimum number of TAs, which make the number of location registrations of UE  60  and the number of paging events balanced, to UE  60  in view of the moving speed Sue and the moving direction Dir of UE  60 . 
     When eNode B  10  is removed, MME  20  can judge that eNode  10  is removed based on the cut-off of the connection link to eNode B  10 . 
     According to the present exemplary embodiment, since eNode B  10  sends the above information to MME  20 , the manual operation of the operator for assigning TAs can be reduced and hence the OPEX can be reduced. 
     According to the present exemplary embodiment, when UE  60  registers its location, since MME assigns TAs to the based on the information about the layout of eNodes B  10  and the information about the movement of the UE, optimum TAs can dynamically be assigned to the UE depending on the movement of the UE. The movement of the UE may be represented by the moving speed and the moving direction, for example. 
     Third Exemplary Embodiment 
     eNode B  10  according to the present exemplary embodiment is identical in configuration to, but is different in operation from, eNode B  10  according to the second exemplary embodiment shown in  FIG. 5 . 
     According to the first exemplary embodiment, eNode B  10  sends information (1) through (4) with respect to eNode B  10  to MME  20  when eNode B  10  itself is added. According to the present exemplary embodiment, eNode B  10  sends the information when UE  60  attaches itself. Attaching of UE  60  means first access from UE  60  to eNode B  10 , e.g., first access after the power supply is turned on. Other details of operation of eNode B  10  are the same as with the second exemplary embodiment. 
     MME  20  according to the present exemplary embodiment is identical in configuration and operation to MME  20  according to second exemplary embodiment shown in  FIG. 5 . 
     Operation of the present exemplary embodiment will be described below with reference to  FIG. 11 . 
     As shown in  FIG. 11 , UE  60  sends a message (Attach Request message) requesting its attachment to eNode B  10  in step  901 . 
     In step  902 , transmitter  11  of eNode B  10  as an attachment destination sends a message (Initial UE Message) for starting an attach procedure, including information (1) through (4) with respect to eNode B  10  and information of the Attach Request message, to MME  20 . 
     Then, if an authentication device (not shown in any of the figures) of MME  20  successfully authenticates UE  60  using user information stored in HSS  50  in step  903 , then transmitter  22  of MME  20  sends a message (Create Default Bearer Request message) requesting the creation of a bearer to S-GW  30  in step  904 . 
     In step  905 , S-GW  30  sends the message (Create Default Bearer Request message) requesting the creation of a bearer to P-GW  40 . In steps  906 ,  907 , P-GW  40  sends a response message (Create Default Bearer Response message) to the message requesting the creation of a bearer via S-GW  30  to MME  20 . 
     At this time, controller  23  of MME  20  performs a process of calculating a range of TAs, to which the cell of eNode B  10  as the attachment destination belongs, creating a new map, and storing the new map in the memory, and also a process of assigning TAs to UE  60  which has attached itself. 
     Then, in step  908 , transmitter  22  of MME  20  sends a message (Initial. Context Setup Request message) including the information of TAs assigned to UE  60  and a message (Attach Accept message) accepting the attachment, to eNode B  10 . In step  909 , transmitter  11  of eNode B  10  sends a message (Radio Bearer Establishment Request message) including the information of TAs assigned to UE  60  and the message (Attach Accept message) accepting the attachment, to UE  60 . 
     Thereafter, in step  910 , UE  60  sends a message (Radio Bearer Establishment Response message) including a response message (Attach Complete message) to the message accepting the attachment, to eNode B  10 . Then, in step  911 , transmitter  11  of eNode B  10  sends a message (Initial Context Setup Response message) including the response message (Attach Complete message) to the message accepting the attachment, to MME  20 . 
     According to the present exemplary embodiment, as described above, when UE  60  attaches itself, eNode B  10  sends information (1) through (4) with respect to eNode B  10  to MME  20 . Therefore, the latest information about eNode B  10  can be indicated to MME  20 . Other advantages are the same as those of the second exemplary embodiment. 
     Fourth Exemplary Embodiment 
     eNode B  10  according to the present exemplary embodiment is identical in configuration to, but is different in operation from, eNode B  10  according to the second exemplary embodiment shown in  FIG. 5 . 
     According to the first embodiment, eNode B  10  sends information (1) through (4) with respect to eNode B  10  to MME  20  when eNode B  10  itself is added. According to the present exemplary embodiment, eNode B  10  sends the information when UE  60  registers its location. Other details of the operation of eNode B  10  are the same as with the second exemplary embodiment. 
     MME  20  according to the present exemplary embodiment is identical in configuration and operation to MME  20  according to second exemplary embodiment shown in  FIG. 5 . 
     Operation of the present exemplary embodiment will be described below with reference to  FIG. 12 . 
     In  FIG. 12 , existing MME  20  and S-GW  30  are referred to as Old MME  20 -O and Old S-GW  30 -O, respectively, MME  20  which eNode B  10  has newly selected based on the information included in a location registration request message (TAU Request message) from UE  60  is referred to as New MME  20 -N, and S-GW  30  which New MME  20 -N has newly selected based on the information included in the TAU Request message is referred to as New S-GW  30 -N. 
     As shown in  FIG. 12 , UE  60  sends a TAU Request message for location registration to eNode B  10  in step  1001 . 
     In step  1002 , transmitter  11  of eNode B  10  as a location registration destination sends a message (Initial UE Message) for starting a TA Update procedure, including information (1) through (4) with respect to eNode B  10  and information of the TAU Request message, to New MME  20 -N. 
     In step  1003 , transmitter  22  of New MME  20 -N sends a message (Context Request message) requesting context information of UE  60  to Old MME  20 -O. In step  1004 , transmitter  22  of Old MME  20 -O sends a response message (Context Response message) to the message requesting context information of UE  60  to New MME  20 -N. 
     If the authentication device (not shown in any of the figures) of MME  20  successfully authenticates UE  60  using user information stored in HSS  50  in step  1005 , then transmitter  22  of new MME  20 -N sends a message indicating that the context of UE  60  is validated for New MME  20 -N and invalidated for Old MME  20 -O to Old MME  20 -O in step  1006 , and sends a message (Create Default Bearer Request message) requesting the creation of a bearer to New S-GW  30 -N in step  1007 . 
     In step  1008 , New S-GW  30 -N sends a request message (Update Bearer Request message) for changing a data transfer route from Old S-GW  30 -O to New S-GW  30 -N to P-GW  40 . In step  1009 , P-GW  40  sends a message (Update Bearer Response message) in response to the request message for changing the data transfer route to New S-GW  30 -N. In step  1010 , New S-GW  30 -N sends a response message (Create Bearer Response message) to the message for requesting the creation of a bearer to New MME,  20 -N. In step  1011 , a process of releasing the bearer with respect to Old S-GW  30 -O is carried out. 
     At this time, controller  23  of New MME  20 -N performs a process of calculating a range of TAs, to which the cell of eNode B  10  as the location registration destination belongs, creating a new map, a process of storing the new map in the memory, and also a process of assigning TAs to UE  60  which has registered its location. 
     In step  1012 , transmitter  22  of new MME  20 -N sends a message (Initial Context Setup Request message) including the information of TAs assigned to UE  60  and a message (TAU Accept message) accepting the location registration, to eNode B  10 . In step  1013 , transmitter  11  of eNode B  10  sends a message (Radio Bearer Establishment Request message) including the information of TAs assigned to UE  60  and the message accepting the to cation registration, to UE  60 . 
     Thereafter, in step  1014 , UE  60  sends a message (Radio Bearer Establishment Response message) including a response message (TAU Complete message) to the message accepting the location registration, to eNode B  10 . Then, in step  1015 , transmitter  11  of eNode B  10  sends a message (initial Context Setup Response message) including the response message (TAU Complete message) to the message accepting the location registration, to MME  20 . 
     According to the present exemplary embodiment, as described above, when UE  60  registers its location, eNode B  10  sends information (1) through (4) with respect to eNode B  10  to MME  20 . Therefore, the latest information about eNode B  10  can be indicated to MME  20 . Other advantages are the same as those of the second exemplary embodiment. 
     The present invention has been described above in reference to the exemplary embodiments. However, the present invention is not limited to the above exemplary embodiments. Rather, various changes that can be understood by those skilled in the art within the scope of the invention may be made to the arrangements and details of the present invention. 
     For example, in the above exemplary embodiments, the LTE wireless communication system has been illustrated. However, the present invention is not limited to the LTE wireless communication system, but is also applicable to other wireless communication systems having mobility management nodes, a base station, and a wireless communication apparatus. 
     Furthermore, the above exemplary embodiments explain the wireless communication system wherein the mobility management nodes and the gateway are separate from each other. However, the present invention is also applicable to wireless communication systems wherein the mobility management nodes and the gateway are integral with each other.