Description Title of Invention: MOBILE COMMUNICATION SYSTEM, SGW, TERMINAL COMMUNICATION METHOD AND CONTROL METHOD Technical Field LOO011 Thc present illvention relates to a bcarer ~na~lagelnednel vice and, for example, rclatcs to a bcwcr ~nanagcrncntd cvicc that pcrfoiins incolning call control Sor a mobilc ter~nilladl evice. Background Art [0002] In the 3GPP (Third Generation Partnership Project) that defines a standard for mobile network systems, EPC (Evolvcd Packet Core) is specified as the next generation mobile network systcm. The EPC is a network system that acco~n~nodateans LTE (Long Tclm Evolution) acccss nctwork in addition lo wirclcss access llclworks called the second generation and the third generation. (00031 incoming packet call processing in the EPC is described hereinafter. In 3rd Generation Pallnership Project; Technical Specification Group Services and System Aspects; Gcncral Packct Radio Scrvicc (GPRS) cllhallccmcllts for Evolvcd Universal Tcsrestsial Radio Access Network (E-UTRAN) access (Release 12), 3GPP TS 23.401 V12.0.0 (2013-03), clauses 5.3.4.3. 5.3.3.2), i~lcolnillgp acket call processing in the case whcre a UE (User Ecluipment) rcprcscnting a user ter~ninails in the idle Inode is disclosed. The state where the UE is in the idle mode is the state where the UE is not connected with the EPC. In othcr words, a wireless bearer between the UE and thc EPC is discollilectcd in this state. In such a case, when an incolning packel call is rnadc to thc UE, S-GW (Serving Gateway). which is a bearer lna~lagc~ncd~elvli ce, sends an incolning call notification lncssagc to MME (Mobility Mallagclnent Entity) or SGSN (Serving GPRS Support Node) that managcs the UE. Receiving thc incorning call notification message, the MME or SGSN sc~ldsa Paging message to cNB (evolved Node B) or NodeB, which is a base station, in ordel- to call the UE. Receiving thc Paging message, the eNB or NoclcB scnds a Paging lnessagc to a plurality oS UE locatcd in the area managed by itself. Thc UE to be called scllds a response message to the eNB or NodeB and con~~ccttos t he IiPC. [OOO4] In this manncr, cvcn when an incoming packct call is rnadc to thc UE in thc idle mode which is not connected with the EPC, it is possiblc to perfom1 data comrnunication with thc UE by calling the UE fi-om thc ~lctworks ide. Citation List Non Patent Literature [OOOS] NPL 1 : 3rd Generation Pal-tnership Project; Technical Specification Group Services and System Aspects; General Packet Radio Senlice (GPRS) enhancelnents for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access (Release 12), 3GPP TS 23.401 V12.0.0 (2013-03), clauses 5.3.4.3, 5.3.3.2 Suininary of Invention Technical Prohlein [0006] However, in the incoining packet call processing disclosed in the above literature, the following problem occurs. Normally, when the UE inoves out of a location registration area managed by the MME, the UE sends a location registration request (Tracking Area Update Request) message to a new MME that ~nanagesa location registration arca to which the UE is to move. Receiving the location registration request message, the new MME pcrfor~nslo cation registration of the UE. After the location registration in the new MME is done, the UE becomes the state where it is registered in the new MME that inanages the location registration area to which it is to move. 100071 When an incoming packet call arrives to the UE after the UE sends the location registration recluest message and belore processing lor moveinenl is done in the new MME, the S-GW sends the incolning call notification inessage to the old MME that has managed the location of the UE before movement. Receiving the incolning call notification message, the old MME sends a Paging incssagc to a base station under its control; howevcr, because the UE to be called has moved out to the arca inanaged by the new MME, it is not possible to call the UE. 111 other words, when an incoming packet call is made whilc the UE is during its movclncnt which involvcs a change in the MME, the problem that the UE cannot receive the incoining packet occurs. LOOOX] An exemplary object of the present invention is to providc a bearer unanagement dcvice, a inobility management device, a ~nobilcte l~ninald evice, a co~nnnunication system, an incolning call processing method, a inobility management inethod and program that perform contml so as to reliably receivc an incoming packet call that is made during inove~neilot f thc inobile terminal device. Solution to Problein [0009] A bcarcr managcincnt dcvicc according to a Sirs1 cxc~nplary aspect ofthc invcnlion include? an incorning call control unit that, in a case where a second mobility management device ~nanagesa location of a mobile terminal device as a result of movement of the inobile terminal device whosc location ha$ been managed by a first nobility management device, suspends procesxing oS an incoming call to the mobile ter~ninald cvice made during movernent oS the inobilc ter~ninald cvice until rccci\/ing a notification about colnplction of lnovcincnt of the inobilc terminal dcvlce froin the second rnobility managenlent device, and rcsumes incorning call processing to the mobile terminal device after receiving a notification about colnpletion of movement of the mobile terininal device from the sccond mobility lnanagement device. [0010] A lnobility management device accordiilg to a second exelnplary aspect of the invention is a mobility lnanagcment device that manages movclneilt of a mobile tcrlninal dcvicc, including a communication unit that, when rccciving an incolniilg call ilotificatioil message to the lnobile tellnilla1 device sent from a bearer lnanageinent device in a case where the lnobile terminal device whose location has been managed by the mobility ~nanagcmendt evice has moved and a location of the mobile terminal dcvicc is mailagcd by anothcr lnobility lnanagcmcnt dcvicc, sends a movclncnt notification lnessage indicating that the lnobile terlninal device has inoved to said another mobility management device to the bearer management device. 1001 1 ] A mobile terminal device according to a third exemplary aspect of the invention includes a com~nunication unit that, when the mobile terminal device moves out ol' an area managed by a first inobility manage~nendt evice from a state where its locatioil has been managed by the first mobility management device, sends a locatioil registration request message to a second inobility rnanagelnent device and, when an incoining call is made before location registration of the mobile terminal dcvice is completed in the second inobility inanagelnent device, receives data addressed to the mobile terlninal device using a wireless resource used when sending the location registration request message. [0012] A colnmui~ications ystem according to a foul-th exemplary aspect of the invention includcs a first lnobility manageinent devicc that manages a location of a lnobile terlninal device located in a first area, a second nobility nlanagclnent device that lnanages a location of a lnobile terminal device localed in a sccond area different from the first arca, and a bcarcr managcrncnt dcvicc that scilds an incolniilg call notification message to the first or second nlobility rnanagemellt device when an incoining call to !he mobile terrninal device is made, whercii~i,n a case whcrc the second lnobility n~anagclncnt dcvicc manages a location oS thc mobile tcnninal dcvicc as a result oS movement of the ~nobilctc rnlinal device having been located in the first area to the second area, the bcarcr management dcvicc suspends processing of an incolning call to the mobile terminal device made during movemcnt of thc mobile terminal dcvice unlil rccciving a 11otiSication about cornplction oS ~novcmcnto S the mobilc tci-~ninadl evicc from the second mobility lnanagclnent device, and resulnes incoming call processing to the mobile terminal devicc after rccciving a notification about completion of ~novement of the mobile terminal dcvice h l n the sccond ]nobility management device. [0013] An incolning call processing method according to a fifth cxemplasy aspect of the invention includcs, in a case where a second mobility managenlent device manages a location of a inobile tcnninal device as a result of movement of the mobile terminal dcvicc whose location has bccn managcd by a first inobility management dcvicc, suspending processing of an inco~ningc all to the mobile terminal device inade during movement of thc inobile terminal device until receiving a notification about completion of movcmcnt of the mobile tcrminal device from thc sccond inobility management device, and resuining incoining call processing to the inobile terminal device after receiving a notification about completion of movement of the mobile terminal dcvice from the second mobility management device. [0014] A mobility managcmcnt incthod according to a sixth cxcinplary aspcct of thc invention is a lnobility management method in a inobility inanageincnt device that manages movement of a inobile terminal device, including, when receiving an incoming call notification message to the mobile terminal device from a bearer management device in a case where the mobile terminal device whose location has been managed by the mobility management device has moved and a location of the inobile terminal device is managed by another mobility management device, sending a movement notification message indicating that the mobile terminal device has moved to said another mobility management device to the bearer management device. [0015] A program accordillg to a seventh exeinplary aspect of the invclltion causes a coinputcr to execute, in a case where a second inobility management device inanages a location of a mobile terminal device as a result of movement of the mobile terminal device whose location has been managed by a first mobility ma~lageinendt evice, a step of suspending processing of an incorning call to the mobile terminal device inade during movement oS the mobile tes~ninald evice until receiving a notification about completion of' movement of' the mobile terminal device from the second inobility managcmcnt dcvicc. and a stcp of rcsuining incoming call proccssing to thc inobilc terminal device alter receiving a notification about completion of movement of the mobile tcrminal device from thc second mobility management dcvice. Advalltageous Effects of I~lvention [0016] According to the exemplary aspects of the present invention, it is possible to provide a bcarcr managcrncnt dcvicc, a inobility managcincnt dcvicc, a lnobilc tcrminal dcvicc, a co~n~nunicatisoyis~t em, an incoming call processing method. a mobility ma~iagemcnt mcthod and program that pel-form coiitrol to reliably receive an incoming packet call that ic made during movement of the mobilc terminal device. Thc above and othcr objccts, f'eatuscs and advantages of thc prcscnt invention will beco~nem ore Sully understood from the detailed description given hereinbelow and the accoinpanying drawings which are given by way of'illustration only, and thus are not to be considered as limiting the preseilt invention. Brief Description of Drawings [0017] [fig. l]Fig. 1 is a configuration diagram of a cormnunication system according to a first exemplary embodiment; [fig.2]Fig. 2 is a coilfiguration diagram of a mobile coinmunicatioil system specified in the 3GPP according to a second exe~nplarye mbodiment; [fig.3]Fig. 3 is a configuratioil diagram of a mobile co~nmuiiicatioisl ystem specified in the 3GPP according to the second exemplary einbodiment; [Gg.4]Fig. 4 is a configuration diagram oS a mobile colnmuilication system specified in the 3GPP according to the second exeinplary ernbodiment; [Sig.S]Fig. 5 is configuration diagrain of SGW according to the second exemplary embodiment; [fig.GjFig. 6 is a diagram showing a flow of connection processing when connecti~lg UE to a mobile communication system according to the second exemplary embodiment; [Sig.7]Fig. 7 is a diagram showing a flow ofprocessiilg when an incoming packet call is made to UE according to the secoi~de xemplasy embodiment; LSig.$]Fig. 8 is a diagram showing a llow of processing when an incoming packet call is made to UE according to a third exemplary embodiment; [Gg.9]Fig. 9 is a diagram showing a flow of processii~g when an incoming packet call is made to UE according to a fourth exemplary einbodirnent; and [fig.lO]Fig. 10 is a diagrain showing a flow of processing when an incorning packet call is made to UE accordiilg to a fifth exemplary embodiment. Description of Embodiments [00 1 81 (First exemplary embodiment) An exemplary embodiment of the present inveiition is described hereinafter with reference to the drawings. A collliguration example oS a co~ninunication sy stern according to a first exemplary e~nbodiment is described hereinafter with reference to Fig. 1. The communication system in Fig. I includes a bearer management device 10, a tnobility management dcvicc 20. a mobility managcincnt dcvicc 30, and a mobile terininal device 40. The mobility management device 20 lnanagcs the location of the mobile ter~ninadl evice located in a location registration area 21. The mobility management device 30 manages the location of the inobile terminal device located in a location registration area 31. Further, ill Fig. 1, the inobile tcl-~ninadl evice 40 is moving from the location registration area 21 to the location registration area 3 1. Note that, in Fig. 1, a wireless base station that wirelessly communicates with the mobile ter~ninadl evice 40 is not shown. As the mobile terminal device 40 moves from the location registration area 2 1 to the location registration area 3 1, the nlobility manageinent devicc that inanages the mobile terininal devicc 40 changes from the mobility manageinenl device 20 to the inobility lnanagcinent device 30. When registration of the inobile terlninal device 40 is completed, the mobility management devicc 30 notifies the bearer management device 10 about the completion of movclncnt of thc inobilc tcr~ninadl cvicc 40. [0019] A configuration exainple of the bearer manageinent device 10 is described hereinafter. The bearer inanagelnent device 10 includes an incoining call control unit 1 I . The case where an incoming packet call is made to the mobile terminal device 40 when the lnobilc terminal dcvice 40 has lnovcd from the location registration arca 21 to the location registration area 3 1 and before registration of the mobile terininal device 40 is coinpletcd in the nobility management device 30 is described hereinafter. In this case, even when an incoming call is made to the mobile terminal device 40, the incoining call control unit 11 suspends incolning call processing for the mobile terininal device 40 until it receives a notification about the coinpletion of lnoveineiit of the mobile terminal device 40 froin the mobility management dcvicc 30. After receiving a notification about the completion of movement of the inobile terminal device 40 froin the inobility inanagernent device 30, the inconling call control unit 11 resuincs inco~ningc all proccssing 10s the inobilc teilninal device 40. For example, the incoiniilg call control unit 11 lnay acquire inforlnation that the inobile ter~ninadl evice 40 is during its inoveinent from the inobility management device 20 when perfornling inco~niilgc all processing for the nlobility management device 20. [0020] The incoining call processing is processing that notifies an incoming call incssage to the nlobility nianageinent dcvice that manages the mobile ter~riinald evice 40. and sends data addressed to the rnobile terminal devicc 40 to the mobile terminal device 40, for cxamplc. Suspending thc inco~ningc all proccssing inay means that, whcn thc incoining call control unit 1 1 detects that thc lnobilc ternlinal device 40 is inoving, it suspends transition to processing of sending data (user data) addressed to the rnobile tcrininal dcvicc 40 to thc mobile tc~minadl cvicc 40 and, aflcr receiving a notification about the completion of movement of the lnobile tenninal device 40. sends the data addressed to the mobile terininal dcvicc 40 to the mobile termin:ll device 40. Alternatively. i t inay mean that the incoming call control unit 1 1 cuspendc transmission of an incoining call lncssagc to thc inobilily inanagcment dcvicc until it rcccivcs a notification about the completion of movement of the rnobilc tctminal device 40 from the mobility lnanagcinent device 30. During movement of the mobile terminal device 40 may be a period froin when the inobilc terminal device 40 eendc a location registration recluest message to the inobility management device 30 that managex the location registration area 31 to which it is to nlove to when the mobility management device 30 notifies a message indicating the completion of movement of the mobile ter~llinal device 40 to the bearer management device 10. [0021] Suspeilding the inco~ningc all processing may be temporarily suspending the incoming call processing, temporarily stopping the incoming call processing, ceasing the incoming call processing with the assuinption of resuming the incoming call processing, dcfel~ingth e cxccution of the iilco~ningc all proccssing and the like. [0022] As described above, with use of the co~ninunications ystem in Fig. 1, even when an incoining packet call is made to the inobile terminal device 40 while the mobile terminal device 40 is during its lnovernent which involves a change in the nobility management device that manages its location, the mobile terminal dcvicc 40 can receive the packet communication. In other words, the bearer management device 10 can resume the incolniilg call processing for the mobile terminal device 40 after receiving a notification about the completion of movement from the mobility management device 30 that manages the location registration area lo which the mobile terminal device 40 moves. Thei-efore, even when an i~lcomingp acket call is made before processing for movement of the mobile terminal device 40 is not done, the bearer management device 10 can notify the mobile tel-minal device 40 about an incoming packet call. [0023] (Second excinplary embodiment) A contiguration example of a co~n~nunicatiosny stem according to a second exemplary embodiment of the inveiltion is described hereinafter with reference lo Fig. 2. In Fig. 2, a inobile co1nmui1ication system specified in the 3GPP is described as a communication system. The coinmunication system in Fig. 2 includes PGW (Packet Data Network GateWay) 75, SGW (Serving Gateway) 15, MME 25, MME 35, UE 45, eNB 55 and eNB 65. [0024] The UE 45 is a communication dcvicc that is specified as a mobile terminal dcvicc in the 3GPP. The UE 45 may be a cellular phone, a smartphone, a tablet terminal, a personal computer with a coin~nunicationf unction or the like, for example. Further, the UE 45 may be an M2M (Machinc To Machine) device that perlorins comm~~nications in an autonomous manner. The M2M device may be a device that does not often move such as an automatic vending machine or an electrical appliance having a communication function, or a watch worn by a user and the like, for example. [0025] The cNB.55 and eNB 65 arc node device5 spccificd a5 base stations in the 3GPP. Each of the eNB 55 and cNB 65 Solms a wireless communication area and cornmunicates with the UE that is located in the wireless communication area inanaged by itself. 100261 The PGW 75 is a node device that i j located at the boundary between the mobile con~munication systeln and the external network. The PGW 75 sends data sent from thc external network to the node device in the mobile cornrrlunication system. The PGW 75 establishes a cominu~lication bearer with the SGW 15. The com~nunication bearer inay be rcferred to as a co~nmunicatioc~hla nnel, a communication path or the like, for example. The PGW 75 sends data sent from the external network to the SGW 15 through the communication bearer. 100271 Thc bcarcr inanagcincnt dcvicc 10 in Fig. 1 is spccificd as thc SGW 15 i11 the 3GPP. When the SGW 15 reccives a notification about an incoining packet call to the UE 45, it notifies an inco~ningc all message to the MME 25 or MME 35. Further, the SGW 15 sends data addressed to the UE 45 to the eNB 55 or eNB 65 that com~nunicatesw ith tllc rnobilc tcr~ninald cvicc 45. [0028] The nobility ~na~lageinednetv ices 20 and 30 in Fig. I are specified as the MME 25 and MME 35 in the 3GPP. Each of the MME 25 and MME 35 deSines a location registration area that manages the location of the UE. In the location registration area managed by each of the MME 25 and MME 35, a plurality of eNB inay be located. In other words, the location registration area may include a plurality of wireless coinmunication areas Sorined by eNB. 100291 When the UE 45 inoves from the locatioil registration area defined by the MME 25 to the location registration area defined by the MME 35, the UE 45 sends a location registration request inessagc to the MME 35. Receiving the locatioil registration request inessage sent from the UE 45, the MME 35 pe~fonnsp rocessiilg for moveinent of the UE 45. The processing for inovelncnt of the UE 45 is processing that the MME 35 registers the UE 45 as a dcvicc to be managed, Sor example. Further, when the MME 35 receives the location registration request message sent froin thc UE 45, it scnds a message notifyi~lgt hat thc UE 45 has rnoved to the location registration area clel'ined by the MME 35 to the MME 25 that inanages the location registration area from which thc UE 45 inovcs. Thc UE 45 may add an idcntificr of thc MME 25 that manages the location registration area bcfore movement to the location registration request inessage for the MME 35. The MME 35 can thereby detect the MME 25 that managcs thc location rcgistratioil arca from which thc UE 45 movcs. The MME 25 receives the notification nlcssage from the MME 35 and can thereby detect that the UE 45 has moved to the location registration arca defined by the MME 35. [0030] Aftel- the processing for movement of the UE 45 is completed, the MME 35 sends a mehaage indicating thc conlplction oS movcmcnt processing ol thc UE 45 to thc SGW 15. In the case whet-e an inconling pacltet call is made to the UE45, the SGW 15 scnds an incoming call notification ~nessageto the MME 25 until a message indicating the complerion of lnovelnent processing of the UE 45 is sent from the MME 35. [0031 1 Thcrc is a case whci-e the MME 25 receives an inco~ningc all notilication message to the UE45 from the SGW 15 after it receives a nlessagc i~ldicatingth e ~nove~nconft the UE 45 from the MME 35. In such a case, the MME 25 sends a message notifying that the UE 45 has moved out to the SGW 15. [0032] By receiving the message notifying that the UE 45 has moved out from the MME 25, the SGW 15 detects that the UE 45 is during its movement which involves a change in the MME. When the SGW 15 detects that the UE 45 is during its movement which involvcs a change in the MME, the SGW 15 temporarily stores data addrcsscd to the UE 45 into a buffer. When the SGW 15 receives a message notifying the completion of movement of the UE 45 from the MME 35, the SGW 15 sends an incoming call notification message to the UE 45 to the MME 35. After that, the SGW 15 sends the data addrcsscd to the UE 45 to the UE 45. LO0331 Although the mobility management devices 20 and 30 are described as being the MME 25 and 35 above, the mobility management devices 20 and 30 may be SGSN 27 and 37 as shown in Fig. 3, The SGSN 27 and 37 are node devices that manage the location 01 the UE that coinmu~licates with a wireless access network called 2G or 3G. The SGSN 27 and 37 connect to 2G/3G wireless control devices 57 and 67 in the wireless access network called 2G or 3G in the 3GPP. The 2G/3G wireless control device in the wireless access network called 2G or 3G may be called RNC (Radio Network Controller), for example. The configuratioll shown in Fig. 3 is the same as that of Fig. 2 except that the MME 25 and 35 are replaced with the SGSN 27 and 37, and the eNB 55 and 65 are replaced with the 2G/3G wireless control devices 57 and 67. [0034] Further, the SGW 15 may coniiect to the MME 25 and the SGSN 37 as shown in Fig. 4. In other words, the SGW 15 may be located in the system where the MME and the SGSN coexist. The configuration shown in Fig. 4 is the same as that of Fig. 2 except that the MME 35 in Fig. 2 is replaced with the SGSN 37, and the eNB 65 is replaced with the 2G/3G wireless contl-ol dcvicc 67. [0035] A configuration example of the SGW 15 according to the second exeinplary embodiment of the invention is described hereinafter with reference to Fig. 5. The SGW 15 includes an incoming call control unit 16 and a data accumulation unit 17. The incoming call control unit 16 is the same as the incoming call control unit 11 in Fig. 1. [0036] When a message notifying the movement of'the UE 45 is sent frorn the MME 25 that manages the location registration area frotn which the UE 45 moves, the incoming call control unit 16 tcrnporarily btol-cs data addrcsscd to the UE 45 inlo the data accumulation unit 17. Further. when a message notifying the col~lpletion of movement of the UE 45 is sent from the MME 35 that inanages the location registration area to which the UE 45 moves, the incoming call control unit 16 sends an incoming call message to [he UE 45 lo the MME 35. Further, when a wireless bearer is established belween the UE 45 and the eNB 65. the incoming call control unit 16 scnds the data stored in the data accu~nulatiou~nl it 17 to the UE 45 through the eNB 65. [0037] Hereinafter, a flow of processing to co~lnectth e UE to the mobile corninunicatio~l systein according to the second exemplary e~nbodilnenot f the invention is described with reference to Fig. 6. First, when a power switch is pressed by a user and a power is turned on, the UE 45 sends an Attach Request message as the location registration reclucst lncssagc to thc cNB 55 (S11). Next, thc cNB 55 scnds thc Attach Rcclucst message sent from the UE 45 to the MME 25 (S12). Receiving thc Attach Request message, the MME 25 generates location registration infoilnation of the UE 45. The location registration information contains i~lformation indicating that the UE 45 is locatcd within the location rcgistration arca managed by its own dcvicc or subscriber infol~nationo f the UE 45, for example. The subscriber i~lformationo r the UE 45 may be acquired from a subscriber information mallage~nendt evice (not shown) that is placed in the mobile comlnunication system. The subscriber information lnanagernent device is specilied as HSS (Home Subscriber Server) in the 3GPP, for example. Then, the MME 25 notifies the subscriber infomation of the UE 45 to the SGW 15 using a Create Session Request message (S13). Then, the SGW 15 sends a Create Session Respo~lsem essage to the MME 25 as a response message to the Create Session Request rrlessage (S14). By receiving thc Create Session Request messagc, the SGW 15 can identify the MME that inailages the locatioil of the UE 45. Fui-ther, by the transinission of the Create Session Response message, a session for the UE 45 is established between the MME 25 and the SGW 15. [0038] Receiving the Create Session Responsc message, the MME 25 sends an Attach Acccpt message to the eNB 55 as a response signal to the Attach Request message (S15). By the trans~rlissiono f tht Attach Accept messagc, the MME 25 completes rcgistration processing of the UE 45. The completion of registration processing of the UE 45 means the co~nplctiono f movement proccssing of thc UE 45. After that, the cNB 55 sends an Attach Accept message to the UE 45 (S16). [0039J By laccciving the Attach Accept message, the UE 45 becomes connec~edto the mobile communication system. The slate whcrc thc UE 45 is coilncctcd to Lhc lnobilc communicatio~sy~s tcrn may be referred to as thc state where the UE 45 is attached to the mobile communication system. [0040] Although the flow of processing when the power of the UE 45 is turned 011 is tlcscribcd abo\/c, the same proccssing is cxccutcd also when the location rcgislration area where the UE 45 is locatcd changes in order to generate location rcgistration information in a new MME. When the location registration area wherc the UE 45 is located changes, the UE 45 scnds a Tracking Area Update Request message instcad of the Attach Recluest mesage. Further, the MME 25 and the SGW 15 send and receive Modify Bearer RequestIModify Bearer Response ~nessagesin stead of the Create Session Request/Creatc Sessioll Response inessages. [0041] Hereinafter, a flow of processing perforlned when an iilco~niilgp acket call is inade to the UE 45 while the UE 45 is during its lnovelneilt which involves a change in the MME according to the second exenlplary enlbodi~nellot f the invcntiol~is described with reference to Fig. 7. In this example, it is assumed that the processing of Fig. 6 is colnplctcd, and the UE 45 is located in the locatioil registration arca managed by the MME 25. [0042] First, when the UE 45 detects that it has inoved Srom the location registratioll area rnanaged by the MME 25 to another location registration area, the UE 45 sends a Tracking Area Update Recluest lncssagc to the cNB 65 that rnailagcs the location registration area to which it has moved (S21). The UE 45 inay detect that the location registration area has changed by receiving allnu~lciationi nfor~nationd elivered froin the eNB 65. Specifically, the UE 45 may detect that the location registration area has changed when the location registratioll area delivered from the eNB 55 belore lnove~neilta nd the location registratioll area delivered from the eNB 65 after movement are different from each other. [0043] Next, the eNB 65 sellds a Tracking Area Update Request message for the UE 45 to the MME 35 that Inailages the location registration area iilcluding the co~nrnu~lication area of its own device (S23). At the saine time, Sl Conilcctioll is established between the eNB 65 and the MME 35 for colninullicatioil of a control message between the UE 45 and the MME 35. It is assumed that the Tracking Area Update Request message co~ltaillsth e identifier of the MME 25 that used to mailage the location registratioll area fi.om which the UE 45 has moved. [0044] Then, the MME 35 sends a Context Request message requcstiilg the transfer of the location registration il~fonnationto the MME 25 ill order to acquire the location registratioil information of the UE 45 from the MME 25 (S24). By the transmission of the Context Request inessage requesting the transf'er of the location registration inforination Sroin the MME 35, the MME 25 call detect that the UE 45 has moved out of the location rcgistratioll arca inanagcd by ithcll. Further, by rccciving the Context Request inessage scnt froln the from the MME 35, the MME 25 can detect that the UE 45 has inoved to the location registration area ~nanagedb y the MME 35. [0045] It is assutncd that an incoming packet call to the UE45 is ~iotificd to the SGW 15 alter thc Co~ltcxtR ecluest lnessagc is scnt Srom the MME 35 to the MME 25 in Step S24 (S25). Inco~nillgp acket call is notified fsom the external network to the SGW 15 via the PGW 75. 100461 The SGW 15 has been notified in the connection processing in Fig. 6 that the UE 45 is located in the location registratioll area managed by the MME 25. Therefore, to notify an iilcolniilg packet call to the UE45, the SGW 15 sends a Downlinl< Data. NotiGcatio~ lr nessage to the MME 25 in order to notify an ii~comingp acket call to the UE45 (S26). [0047] The MME 25 has detected that the UE 45 is during its ~noveinenbt y receiving the Context Request inessage in Step S24. Therefore, the MME 25 cannot tcnlporasily peifor~nc all atteinpt to the UE 45, that is, temporarily rejects the Downlink Data Notification mcssagc. Thca, thc MME 25 scts Causc indicating that the UE 45 is during its nlove~neilta nd call attenlpt to the UE 45 is teinporarily i~npossiblea nd sends a Downlink Data Notification Acknowledge lnessage in response to the Downlink Data Notification message (S27). To the Downlink Data Notification Acknowledge mcssagc, "Causc=Tcmporarily Rcjcctcd duc to mobility" is sct as Causc setting. "Cause=Temporasily Rejected due to mobility" indicates that infol~nationii ldicating that the UE is moving and call atteinpt is temporarily u~lavailable( temporarily rejected) i$ set to Cause. [0048] Receiving the Dowilli~lkD ata Notification Acknowledge mcssage to which "Cause=Tenlporasily Rejected due to tnobility" is set, the SGW 15 suspends incoining packet call processing, and starts a timer (locally configured guard timer) for retransmitting the Downlink Data Notification mcssage. coiltinuillg buffering of the packet addressed to the UE 45. 100491 ' Then, the MME 25 exccutcs the operation as the MME that manages the location registration area from which the UE 45 inovcs in the Tracking Area Update Request message. Specifically. the MME 25 sends a Context Response message to the MME 35 as a response rnessage to the Context Request lnessage in Step S24 (S28). The MME that Inanages the location registration area from which the UE 45 moves may be referred to as Old MME. On the othel- hand, the MME that mailages the locatio~l registration area to which the UE 45 inoves may bc referred lo as New MME. The MME 25 notifics thc location rcgistration information of thc UE 45 to thc MME 35 using the Coiltext Response message. Thc MME 35 sends a Context Ackilowledge lnessage to the MME 25 as a response message lo the Co~~tcIxiet sponse incssage (S29). [0050] Then, thc MME 35 sends a Modify Bcarcr Rcclucst rncssagc to the SGW 15 in order to notify switching of the session established bctwcen the MME 25 and the SGW 15 (S30). The session cstablishecl bctwcci~th e MME 25 ancl the SGW 15 is thc session that has been established in Stcpr S 13 and S 14 of Fig. 6. The SGW 15 dctccts that the movcmcnt proccs.sing of thc UE 45 is cotnplctcd in the MME 35 by rccciving the Modify Bearer Rcqucst message. The MME 35 may send an iclentil'ier that identifies the session established between the MME 25 and the SGW 15 to the SGW 15 and (hereby notify switching of thc scsrlon established bctwccn the MME 25 and the SGW 15. The identifier that identifies the session cjtablished between the MME 25 and the SGW 15 nlay be contained in the Context Response message in Step S28. [0051] Thc SGW 15 sends a ModiSy Bearer Response message to the MME 35 as a response inessage to the Modify Bearer Request inessage (S31). At the same time, the SGW 15 stops the timer (locally configured guard tiiner) that has been stated when receiving the Downlink Data Notification Acknowledge rnessage in Step S27. [0052] Receiving the ModiSy Bearer Response message, the MME 35 sends a Tracking Area Update Acccpt lncssagc to thc eNB 65 as a rcsponsc mcssagc to Stcp S23 (S32). Thcn, the eNB 65 sends the sent Tracking Area Update Accept inessage to the UE 45 (S33). 100531 After that, the MME 35 releases the S1 Coli~lectioltlh at has bee11 established between the MME 35 and the cNB 65 (S34). [0054] Thcn, thc SGW 15 sends a Downlink Data Notification message to the MME 35 that inanages the location registratioll area to which the UE 45 inoves in order to notiSy an incoining packet call to the UE45 (S35). Thus, in Step S35, the processi~igo f sending the Downlink Data Notification inessage to the MME 25 in Step S26 is performed for the MME 35 that inanages the location registration area to which the UE 45 moves. Then, the MME 35 sends a Paging inessage to the eNB 65 in order to pcrforin call attempt to thc UE 45 (S36), and the eNB 65 sends a Paging message to the UE located in thc co~ninunicatio~arie a under its control (S37). In this manner, after moving to the new location registration area, the UE 45 can receive a notification about the incoming packet call that has been made during its movement. 100551 111 the case where the tiiner (locally configured guard timer) that has been started when thc Dowillink Data Notification Ack~lowlcdgem essage is rcceived in Step S27 expires before receiving the Modify Bearcr Request inessage, the SGW 15 inay end the incoini~lgp acket call processing to the UE45. Alternatively, thc SGW 15 may send the Downlink Data NotiSication message to the MME 25 again to colltinuc the inconling packet call proccssing. [0056] In the case whcrc the titncr (locally configured guard tirncr) that has been stalled when the Downli11k Data Notification Acknowledge inessage is reccivcd in Step S27 expires w~thourte ceiving the Modify Bearer Request inessage, the SGW 15 inay rclcasc thc buSScrcd packc( addrcsscd to lhc UE 45. [0057] As described abo\lc. with use of the colnr~~unicatiosny stem according to the second exenlplary einbodilnent of the invention, even when an incoining packet call is made to the UE 45 while the LIE 45 is during its movement which involves a change in the MME and the movcmcnt processing oS Ihc UE 45 has not co~nplctcdin thc new MME, the UE 45 can normally 1-eceive ail incoming packet call notification. [0058] Fusther. in the case where the MME 35 is replaced with the SGSN 37 and the eNB 65 ic replaced with the 2G/3G wireless control device 67 as show11 in Figs. 3 and 4. the Traclting Area Update Recjuejt message in Steps S21 and S23 is replaced with the Routing Area Update Request inessage. Further, the Tracking Area Update Accept message in Steps S32 and S33 is replaced with the Routing Area Updatc Accept message. If the MME 25 and the SGSN 37 activate ISR (Idle-mode signaling reduction), the continuation of the incorning packet call processing performed in Step S35 may be carried out by both of the MME 25 and the SGSN 37. [0059] (Third exeinplary embodiment) Hereinafter, a flow of proccssing pcrfor~ncdw hen an incorning packet call is made to the UE 45 while the UE 45 is during its ino\~ementw hich illvolves a change in the MME according to the third exemplary embodiinent of the invention is described with reference to Fig. 8. Steps ,541 to S49 are the same as Steps S21 to S29 in Fig. 7 and thus not redundantly described in detail. Further, when executing the processing of Fig. 8, it is assumed that the processing of Fig. 6 is completed, and the UE 45 is located in the location registration area managed by the MME 25. [OO6O] After sending the Context Acknowledge message to the MME 25 in Step S49, the MME 35 sends a Modil'y Bearer Request message to the SGW 15 (S50). The SGW 15 sets illforination of "SGW requested active flag = ON" to the Modify Bearer Response mcssage and sends it to the MME 35 (S5 1). [0061] Receiving the information of "SGW requested active flag = ON", the MME 35 maintains the S1 Connection between the eNB 65 and the MME 35 that has been established for Altach processing or Tracking Area Updatc processing without releasing it. Further, the MME 35 also inaintains the RRC (Radio Resource Control) connection between the UE 45 and the eNB 65 that has been established for Attach processing or Tracking Area Update processing. When the SGW 15 reccives a Modify Bearer Request indicating the colnpletion of moveinent of the UE after detecting that the UE to which an inconling packet call notified in Step S45 is nlade is during its movement. it sets information of "SGW requested active flag = ON" to the Modify Bearer Rcsponsc lncssagc and sciids it to the MME 35. (0062j Receiving the Modify Bearer Responsc message, the MME 35 sends a Tracking Area Update Accept ~nessageto the eNB 65 as a response message to Step S43 (S52). The cNB 65 the11 sends the scnl Tracking Arca Updatc Accept mcssagc to the UE 45 (S53). Because the MME 35 has received the infor~nation of "SGW requested active llag = ON", it does not execute S 1 Connection release processing. Further. at the same time as sending the Tracking Arca Update Accept message, the MME 35 sends a wireless packet bearer cslablishincnt rccjucst mcssagc to the cNB 65 through the maintained Sl Connection. The wireless packet bearer is a bearer that is used for co~ninunicationo l' user data such as audio data, image data or \Glco data between the UE 45 and the eNB 65. 100631 Receiving the wireless packet bearer establishment recluest message, the eNB 65 establishes a wirelcss packet bearer between the UE 45 and the eNB 65 using the RRC connection (S55). After establishing the wireless packet bearer, the eNB 65 sends a wireless packet bearer establishment response message to the MME 35 (S56). The wireless packet bearer establishment response lncssagc contains TEID (eNB Tunnel End Point Identifier) of the eNB 65. COO641 Receiving the wireless packet bearer establishinent response messagc, the MME 35 scnds a Modify Bcarcr Rcclucst mcssagc to which thc TEID of the cNB 65 is sct to thc SGW 15 (S57). [0065] Then, the SGW 15 sends a Modify Bearer Response message to the MME 35 as rcsponse message to the Modify Bearer Request message (S58). The SGW 15 then sends thc data addressed to the UE 45 to thc TEID of the cNB 65 sct to thc Modify Bearer Request mcssage. The eNB 65 sends the data addressed to the UE 45 sent from the SGW 15 to the UE 45 through the wireless packet bearer (S59). [0066] As described above, in the flow of processing in Fig. 8, after the MME 35 sends the Tracking Area Update Accept message, it does not release $1 Connection and sends the wireless packet bearer establishment request message to the eNB 65 using the maintained S1 Connection. The UE 45 thcrcby remains connected with the mobile communication system, and the MME 35 can skip the processillg of sending the Paging message and call attempt to the UE 45, which is described in Fig. 7. [0067] In Fig. 7, the MME 35 releases S1 Collllcction with the eNB 65. The UE 45 thereby becomes disconnected from the mobile coinlnullication system, that is, becomes separated from the mobile conlnlunicatio~sl ystem. Therefore, the MME 35 needs to send the Paging message to call the UE 45. LO0681 On the othcr hand, in Fig. 8, the Sl Connection between thc MME 35 and the cNB 65 is maintained, and further the RRC Con~lectionb etween the UE 45 and the eNB 65 is maintained. Therefore, the MME 35 does not need to execute the processing of call attempt to thc UE 45, and it is possiblc to skip thc processing of sending the Paging message. [0069] The MME 35 sends the Paging message to all the eNB located in the location rcgistration area managed by itsell'. Further, the cNB that has rcccivcd the Paging mcssagc sends the Paging lnessage to all the UE located in the communication area undcr its control. Therefore. the proccs~ingo f sending the Paging lncssage is heavy-load processing in the mobile communication system. Thus, by omitting the transmission of the Paging mcssagc in Fig. 8, it is possible lo reduce the load in the mobile coinmunicntion system. [0070] (Fourth exemplary cmbodirnent) Hereinafter, a tlo\v of processing performed when an inco~nii~pgac ket call is made to the UE 45 while the UE 45 is during its movement which involves a change in the MME according to the fourth exemplary embodiment of the illve~ltioni s described with reference to Fig. 9. Steps S61 to S67 arc the sarne as Steps S21 to 527 in Fig. 7 and Steps S41 to S47 in Fig. 8 and thus not redundantly described in detail. Further, when executing the processing of Fig. 9, it is assumed that the processing of Fig. 6 is completed, and the UE 45 is located in the locatioil registration area managed by the MME 25. [007 l] Thc MME 25 scnds a Contcxt Rcspo~lscin cssagc to the MME 35 as a rcsponsc message to the Context Request message sent froin thc MME 35 in Step S64 (S68). The MME 25 sends the Context Response inessage to which "Active Flag=ONU is set to the MME 35 in order to notify that it is necessary to establish a wireless packet bcarcr. Thcn, thc MME 35 sends a Contcxt Acknowlcdgc mcssagc to thc MME 25 as a response message to the Context Response message (S69). [0072] Steps 570 to S77 are the same as Steps S52 to S59 ill Fig. 8 and thus not redundantly described in detail. In Steps S70 to S77, the processing of establishing a wireless packet bearer between the UE 45 and the eNB 65 is performed without releasing the S 1 Connection, just like the processiilg of Fig. 8. [0073] As described above, in the processing of Fig. 9, a message that serves as a trigger to establish a wireless packet bearer is sent to the MME 35 from the MME 25, not from the SGW 15. Therefore, in the processing of Fig. 9, it is possible to skip the translnission and reception of the Modify Beaver RequestlModify Bea-er Response messages in Steps S50 and S5 1 in the processing of Fig. 8. Further, in the processing of Fig. 9, it is possible to skip the processing of sending the Paging message, just like the processing of Fig. 8. 100741 (Fifth exeinplary embodiment) Hereinafter, a flow of processillg performed when the UE 45 rnaltcs its mo\icrnent which involves a changc in the MME after an incoining packet call is notificcl according to thc fifth cxcinplary cmbodiincnt of the invention is described with reference to Fig. 10. When executing the processing of Fig. 10. it is assuined that the proccssin~o f Fig. 6 is completed, and the UE 45 is located in the location rcgistration arca managcd by the MME 25. [0075] First. the SGW 15 receives an incoming packet call to the UE45 (S81). The SGW 15 receives an incoining packet call that is sent Srorn thc cxtci~lanl etwork through the PGW 75. The SGW 15 has been nolified in thc connection processing in Fig. 6 that the UE 45 is located in thc location rcgistration arca managcd by thc MME 25. Thcrcforc, to notiSy an inconling packet call to the UE45, the SGW 15 sends a Downlink Data Notification incssage to the MME 25 (S82). 100761 Next. the MME 25 sends a Downlink Data Notification Acknowlcdge ~nessagca s a 1-eaponsc lncssage lo the Downlink Data Notification lncssage (S83). The MME 25 then sends a Paging incssage to the eNB 55 l'or call attempt to the UE 45 (S84), and the eNB 55 sends the Paging rnessage to the UE located in the communication asea under its control (S85). [0077] It is assuincd that, immediately before the eNB 55 sends the Paging rnessage or immediately alter the eNB 55 sends the Paging message in Step ,985, the UE 45 moves out of the wireless co~n~nui~icatairoena inanaged by the eNB 55 and out of the location rcgistratioll area managed by the MME 25. In such a case, the UE 45 cannot receive the Paging message. LO0781 When the UE 45 moves out of the location registration area managed by the MME 25 and into the location registration area managed by the MME 35, the UE 45 sends a Tracking Arca Update Request message to thc eNB 65 located in the location rcgistration area rnanaged by the MME 35 (S86). [0079] Then, the eNB 65 sends a Tracking Arca Update Request nlessage for the UE 45 to the MME 35 that manages the location registration area including the com~nunication area ol its own device (S88). A1 the same lime, S1 Connection is established between the eNB 65 and the MME 35 for co~ninuilicationo f a control message. It is assumed that the Tracking Area Update Request message contains the identifier of the MME 25 that used to manage the location registration area from which the UE 45 has moved. [0080] Then, the MME 35 sends a Context Request message requesting the transfer of the location registration infor~nationt o the MME 25 in order to acquire the locatioil registration information of the UE 45 from the MME 25 (S89). By the transmission of the Coiltext Request message requesting the transfer of the location registration information of the UE 45 from the MME 35, the MME 25 can detect that the UE 45 has moved out of the location registration area managed by itself. Further, by receiving the Co~ltexRt equest message sent fronl the from thc MME 35. thc MME 25 can detect that the UE 45 has moved to the location registration area ~nanagcdb y the MME 35. [0081] The MME 25 has dctcctcd that the UE 45 is during its rnovcrncnt by rcceiving the Coiltext Request message in Step S89. Thereforc. the MME 25 stops call attcmpt to the UE 45 and temporarily rejects the Downlink Data Notificat~onT. hen. the MME 25 sets Cause indicating that the UE 45 is during itb tnovclncnt and call attcmpt to the UE 45 is te~nporarilyi nlpossible (temporarily rejected) and sends a Downlink Data Noti- Sication Failure Indication message indicating a failure in IIICOJII~IIp~a cket call notification (S90). To the Downlinl< Data Notification Acknowledge mc