JP6469454B2 - Communication system and communication control method - Google Patents

Description

  The present invention relates to a communication system and a communication control method.

  The mobile communication system is realized by a wireless network including a base station device and a core network including an exchange. In addition, standard specifications of communication methods and communication interfaces in mobile communication are defined by the 3rd Generation Partnership Project (3GPP).

  Currently, there are technologies for realizing various functions and services by building a plurality of core networks according to the purpose in a mobile communication system.

  For example, a technique called network sharing that allows a plurality of operators to share a wireless network among wireless networks and core networks that are generally constructed independently for each operator (see, for example, Non-Patent Document 1). There is.

  Thus, when providing a plurality of core networks according to the purpose, a plurality of exchanges are connected to one base station apparatus.

  Here, the base station apparatus manages the load of each of a plurality of exchanges connected to the base station apparatus. When receiving the connection request from the terminal, the base station apparatus can select (load balance) which switch the terminal is connected to according to the load of each of the plurality of switches (for example, Non-Patent Document 2). reference).

3GPP TS 23.251 V13.0.0 (2014-12) 3GPP TS 23.401 V13.1.0 (2014-12)

  However, in the conventional technology, when selecting which switch to connect the terminal to according to the load of each of the plurality of switches, the MME is selected in consideration of the plurality of core networks according to the purpose. I could not.

  FIG. 1 is a diagram for explaining the problem. A problem when the MME 10 is selected by the eNB 20 (evolved NodeB) and the terminal 30 is connected to the selected MME 10 when congestion occurs in the MME 10 (Mobility Management Entity) will be described with reference to FIG.

  In the mobile communication system shown in FIG. 1, two core networks (core network A and core network B) are connected to the eNB 20. Moreover, the core network A has MME10a, MME10b, and MME10c, and the core network B has MME10d and MME10e. Further, it is assumed that the terminal 30 is connected to the MME 10e of the core network B.

  First, when the MME 10e itself becomes congested (processing load exceeds a predetermined threshold), the MME 10e transmits a connection release signal (S1 UE Context release Command) to the eNB 20 (S1). The signal transmission reason (Cause value) included in this connection release signal includes information (Load-Balancing TAU required) indicating that reselection (load balance) of the MME 10 is requested. Subsequently, the eNB 20 releases the radio resources established with the terminal 30 (S2).

  When the terminal 30 recognizes that the MME 10e requests reselection of the MME 10, the terminal 30 transmits a location registration update request signal (TAU Request) to the eNB 20 (S3). Normally, the terminal 30 transmits a location registration update request signal including a temporary subscriber identifier (GUTI (Globally Unique Temporary Identifier)) to the eNB 20, but when the MME 10 requests reselection of the MME 10, The terminal 30 transmits a location registration update request signal that does not include GUTI to the eNB 20. Note that the eNB 20 can uniquely identify the core network and the MME 10 to which the terminal 30 was connected immediately before by the GUTI.

  When the eNB 20 receives the location registration update request signal that does not include the GUTI, the eNB 20 determines that the MME 10 to which the terminal has connected immediately before requests the reselection of the MME 10, and all the MMEs that can communicate with the eNB 20 Any one of (10a, 10b, 10c, 10d, 10e) is selected, and a location registration update signal is transmitted to the selected MME 10 (any one of S4 to S8).

  However, when there are a plurality of core networks in the mobile communication system, when the MME 10 is reselected, the terminal 30 connected to the predetermined core network until then is connected to a different core network from the predetermined core network. There was a possibility of being.

  For example, in the example of FIG. 1, the eNB 20 selects any one MME 10 among the MMEs (10a, 10b, 10c, 10d, 10e). Accordingly, there is a possibility that the terminal 30 is connected to the MME (10a, 10b, 10c) belonging to the core network A with 60% establishment.

  The network sharing technique described above has a mechanism for reconnecting the terminal 30 to the MME 10 in an appropriate core network when a terminal 30 that is not permitted to be located is connected. However, even if the MME 10 is congested and the reselection of the MME 10 is requested for the terminal 30 that is allowed to be located in both core networks, the terminal 30 is initially in the area. It may be desirable to be connected to the MME 10 in the core network.

  The disclosed technology has been made in view of the above, and in a mobile communication system having a plurality of core networks, when reselection of an exchange is performed, the core network to which the terminal 30 is connected is appropriately selected. The purpose is to provide the technology that enables it.

  A communication system according to the disclosed technique is a communication system including a plurality of exchanges belonging to each of a plurality of networks and a base station apparatus connected to each of the plurality of exchanges, wherein the exchange includes a load of the exchanges A first transmitter that transmits, to the terminal, an identifier update signal that includes a network identifier that identifies a network to which the switch belongs based on a state, and the base station apparatus performs location registration including the network identifier from the terminal. A receiving unit that receives an update signal; and an exchange that transmits the location registration update signal from the plurality of exchanges belonging to the same network as the network indicated by the network identifier, based on the network identifier. And the location registration update to the selector selected by the selector. It has a second transmission unit for transmitting signals.

  According to the disclosed technology, in a mobile communication system having a plurality of core networks, it is possible to provide a technology capable of appropriately selecting a core network to which a terminal is connected when reselection of an exchange is performed. it can.

It is a figure for demonstrating a subject. It is a figure which shows the whole structure of the mobile communication system which concerns on embodiment. It is a figure which shows an example of a function structure of the switching device which concerns on embodiment. It is a figure which shows an example of the format of GUTI which concerns on embodiment. It is a figure which shows an example of a function structure of the base station apparatus which concerns on embodiment. It is a figure which shows an example of a function structure of the terminal which concerns on embodiment. It is a sequence diagram which shows an example of the process sequence of the mobile communication system which concerns on embodiment.

  Hereinafter, embodiments will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted.

  In the following explanation, the embodiment will be described assuming that congestion occurs in the exchange, but it is also assumed that reselection of the exchange is performed due to factors other than congestion, such as when an abnormality occurs in the exchange. Can be done. Therefore, the mobile communication system according to the embodiment can also be applied to the case where reselection of the exchange is performed due to a factor other than congestion.

<Overall configuration>
FIG. 2 is a diagram illustrating an overall configuration of the mobile communication system according to the embodiment. The mobile communication system according to the embodiment includes an exchange (MME 10), a base station apparatus (eNB 20), and a terminal 30. In the mobile communication system according to the embodiment, two core networks (core network A and core network B) are connected to the eNB 20 as in FIG. The core network A has three MMEs (MME10a, MME10b, and MME10c), and the core network B has two MMEs (MME10d and MME10e).

  In the following description, any MME among the MME 10a, MME 10b, MME 10c, MME 10d, and MME 10e may be described as “MME 10”. Further, the MME 10 included in an arbitrary core network may be described as “MME 10 belonging to the core network”.

  The MME 10 and the eNB 20 can communicate with each other. Also, the terminal 30 can communicate with the eNB 20. Furthermore, the terminal 30 can directly communicate with the MME 10 via the eNB 20.

  The core network A may have one or two MMEs 10, or may have four or more MMEs 10. Similarly, the core network B may have one MME 10 or may have three or more MMEs 10.

  The mobile communication system according to the embodiment will be described on the assumption that it is a mobile communication system in LTE, but can be applied to other mobile communication systems. The mobile communication system according to the embodiment can also be applied to a case where one or three or more core networks are included.

  Further, the core network A and the core network B may be core networks provided by different mobile communication carriers. Further, the core network A and the core network B may be core networks provided by the same mobile communication carrier.

  When the core network A and the core network B are core networks provided by the same mobile communication carrier, the core network A may be, for example, a normal core network, and the core network B may be, for example, 3GPP TR23. 707 V13.1.0 (2014-12), a core network dedicated to a specific terminal such as an M2M terminal (hereinafter referred to as “Dedicated Core Network”) may be used. The mobile communication system according to the embodiment can be applied to any case.

  The MME 10 has a function of controlling a transmission path of a call from the terminal 30 (performing session control), and is equipped with an exchange (S-GW (Serving Gateway), P-GW (Packet Data Network Gateway) that transmits the call. )) Is a different exchange. The MME 10 is a hardware such as a CPU (Central Processing Unit) such as a processor, a memory device such as a ROM (Read Only Memory), a RAM (Random Access Memory) or a flash memory, a communication interface device for communicating with the eNB 20 and the terminal 30 and the like. Hardware resources. Each function and process of the MME 10 may be realized by a processor processing or executing data or a program stored in a memory device. However, the MME 10 is not limited to the hardware configuration described above, and may have any other appropriate hardware configuration.

  The eNB 20 has a function of receiving a call from the terminal 30 through radio and transmitting the call to the MME 10. The eNB 20 is configured by hardware resources such as a CPU such as a processor, a memory device such as a ROM, a RAM, or a flash memory, an antenna for communicating with the terminal 30 and the like, and a communication interface device for communicating with the adjacent eNB 20 and the MME 10 and the like. Is done. Each function and process of the eNB 20 may be realized by a processor processing or executing data or a program stored in the memory device. However, the eNB 20 is not limited to the hardware configuration described above, and may have any other appropriate hardware configuration.

  The terminal 30 has a function of communicating with the eNB 20 and the MME 10 through wireless. The terminal 30 is, for example, a mobile phone, a smartphone, a tablet, a mobile router, a wearable terminal, or the like. The terminal 30 may be any terminal as long as it has a communication function. The terminal 30 is configured by hardware resources such as a CPU such as a processor, a memory device such as a ROM, a RAM, or a flash memory, an antenna for communicating with the eNB 20, and an RF (Radio Frequency) device. Each function and process of the terminal 30 may be realized by a processor processing or executing data or a program stored in a memory device. However, the terminal 30 is not limited to the hardware configuration described above, and may have any other appropriate hardware configuration.

<Functional configuration>
(MME)
FIG. 3 is a diagram illustrating an example of a functional configuration of the exchange according to the embodiment. The MME 10 includes a load detection unit 101, an identifier update request unit 102, a session management unit 103, and a terminal information acquisition unit 104. Each of these means is realized by processing that one or more programs installed in the MME 10 cause the CPU to execute.

  The load detection unit 101 monitors the processing load of the MME 10 itself, and compares the predetermined threshold value determined in advance with the processing load of the MME 10 itself to determine whether the MME 10 itself is in an overload state (congestion state). Judging. When the processing load exceeds a predetermined threshold value, the load detection unit 101 determines that the MME 10 itself is congested and requests the terminal 30 and the eNB 20 to reselect the MME 10. The load detection unit 101 detects values such as the CPU usage rate, memory usage rate, traffic volume, temperature, clock count, or power consumption of the MME 10 as the processing load, and compares the acquired value with a predetermined threshold value. It may be.

  When the identifier update request unit 102 receives a notification from the load detection unit 101 that the MME 10 is congested, the identifier update request unit 102 updates the GUTI and TA List (Tracking Area List) stored in the terminal 30 to the terminal 30. Send a signal to make it happen. GUTI is a temporary subscriber identifier used in LTE networks. TA (Tracking Area) indicates a location registration area in LTE, and one TAI (Tracking Area Identifier) is assigned to each location registration area. TA List is a list in which a plurality of TAIs are bundled.

  When the terminal update is performed by the terminal 30, the identifier update request unit 102 includes a TAI (hereinafter referred to as “non-broadcast TAI”) in which a number that is not normally used for the TAI is stored in the terminal 30. Send TA List. The TAI in which numbers that are not normally used for TAI are stored is, for example, TAI in which all bit values are set to “1”.

  Here, the format of GUTI transmitted to the terminal 30 will be described.

  FIG. 4 is a diagram illustrating an example of a GUTI format according to the embodiment. GUTI shown in FIG. 4 includes MCC (Mobile Country Code), MNC (Mobile Network Code), MMEGI (MME Group Identifier), MMEC (MME Code), M-TMSI (M-Temporary Mobile Subscriber Identity), Consists of MCC is a code indicating the country in which the mobile communication system is operated. The MNC is a code that uniquely identifies an operator operating the mobile communication system in the country where the mobile communication system is operated. The MMEGI is an ID that uniquely identifies a group (pool area) to which the MME 10 belongs in a mobile communication system operated by the same operator. The pool area is composed of one or more MMEs 10. The MMEC is a code that uniquely identifies the MME 10 in the same MMEGI. The M-TMSI is an ID for uniquely identifying a subscriber (terminal 30) in the MME 10, and is an ID given temporarily. That is, by referring to GUTI, it is possible to grasp which core network the subscriber (terminal 30) is connected to and which MME 10 is connected to. An ID obtained by removing M-TMSI from GUTI (that is, an ID composed of MCC, MNC, MMEGI, and MMEC) is called GUMMEI (Global Unique MME Identifier). The mobile communication system can uniquely identify the MME 10 by using GUMMEI.

  In the GUTI according to the embodiment, among the 8 bits (0th to 7th bits) constituting the MMEC, the 7th bit is used to indicate the state of the MME 10, and the 0th to 6th bits are set. To uniquely identify the MME 10. Specifically, when the MME 10 is in a normal state, the seventh bit of the MMEC is set to “0” so that an abnormality or the like occurs in the MME 10 (for example, the MME 10 is congested). The first bit is set to “1”. An MMEC in which “0” is set in the seventh bit is called “Normal-MMEC”, and an MMEC in which “1” is set in the seventh bit is called “Null-MMEC”.

  The session management unit 103 manages the session state of the terminal 30 connected to the MME 10, and transmits and receives various signals related to session establishment and release between the eNB 20 and the S-GW. When the session management unit 103 receives a notification from the load detection unit 101 that the MME 10 is congested, the session management unit 103 has already established a session for the eNB 20 and the S-GW in order to reduce the load on the MME 10 itself. Send a signal to release.

  When receiving the location registration update request from the eNB 20, the terminal information acquisition unit 104 acquires the profile information (UE Context) of the terminal 30 from the old MME 10 (the MME 10 to which the terminal 30 was connected immediately before the reselection of the MME 10). To do.

(ENB)
FIG. 5 is a diagram illustrating an example of a functional configuration of the base station apparatus according to the embodiment. The eNB 20 includes a radio resource management unit 111, a location registration request transmission / reception unit, and a selection unit 113. Each of these means is realized by processing that one or more programs installed in the eNB 20 cause the CPU to execute.

  The radio resource management unit 111 manages radio resources established between the eNB 20 and the terminal 30.

  The location registration signal transmission / reception unit 112 receives a location registration update request from the terminal 30 and transmits a location registration update signal to the MME 10 instructed by the selection unit 113.

  Based on the GUTI included in the location registration update request received from the terminal 30, the selection unit 113 instructs the location registration signal transmission / reception unit 112 to which location registration update signal should be transmitted. Moreover, the selection part 113 hold | maintains the identifier (for example, GUMMEI) regarding all the MME10 connected to eNB20.

(Terminal)
FIG. 6 is a diagram illustrating an example of a functional configuration of the terminal according to the embodiment. The terminal 30 includes an identifier update reception unit 121, a radio resource release reception unit 122, and a location registration request unit 123. Each of these means is realized by processing that one or more programs installed in the terminal 30 cause the CPU to execute.

  The identifier update accepting unit 121 accepts a signal for updating the GUTI and TA List (Tracking Area List) stored in the terminal 30 from the MME 10, and accepts the GUTI and TA List stored in the terminal 30. Updated to GUTI and TA List included in the received signal.

  The radio resource release accepting unit 122 accepts a radio resource release instruction established between the eNB 20 and the terminal 30 from the eNB 20 and releases the radio resource.

  The location registration request unit 123 requests location registration to the eNB 20 and the MME 10. In addition, when the radio resource established between the eNB 20 and the terminal 30 is released, the location registration request unit 123 includes a non-broadcast TAI in the TA List stored in the terminal 30 The eNB 20 and the MME 10 are requested to update location registration.

<Processing procedure>
FIG. 7 is a sequence diagram illustrating an example of a processing procedure of the mobile communication system according to the embodiment. A processing procedure from when congestion is detected in the MME 10e until the terminal 30 is connected to the MME 10 different from the congested MME 10e will be described with reference to FIG. In addition, when the mobile communication system is constructed | assembled using the network sharing technique, it assumes that MME10d, MME10e, and MME10f belong to the core network which the same mobile communication provider provides. Further, when a normal network and a dedicated core network exist in the core network provided by the same mobile communication carrier, the MME 10d, the MME 10e, and the MME 10f belong to either the normal network or the dedicated core network. Assuming that

  In step S201, the load detection unit 101 of the MME 10e detects that the processing load of the MME 10e has exceeded a predetermined threshold.

  In step S202, the identifier update request unit 102 of the MME 10e sends a GUTI in which the value of the seventh bit of the MMEC is set to “1” and an identifier update request signal having a TA-List including a non-broadcast TAI. 30. The identifier update request unit 102 sets a code indicating the MME 10e in the 0th to 6th bits of the MMEC. The identifier update request signal is, for example, a signal called “GUTI Reallocation Command”.

  In step S203, the identifier update accepting unit 121 of the terminal 30 updates the GUTI and TA-List stored in the terminal 30 to the GUTI and TA-List included in the identifier update request signal received in step S202. At the same time, an identifier update response signal is transmitted to the MME 10e. The identifier update response signal is, for example, a signal called “GUTI Reallocation Complete”.

  In step S204, the session management unit 103 of the MME 10e transmits an access bearer release request signal to the S-GW 40 in order to release the session established by the terminal 30 with the core network. The access bearer release request signal is a signal called, for example, “Release Access Bearer Request”.

  In step S205, the session management unit 103 of the MME 10e receives an access bearer release response signal from the S-GW 40. The access bearer release response signal is, for example, a signal called “Release Access Bearer Response”.

  In step S206, the session management unit 103 of the MME 10e transmits a connection release request signal to the eNB 20. The connection release request signal is a signal called “S1 UE Context Release Command” used in, for example, S1AP (S1 Application Protocol).

  In step S207, the radio resource management unit 111 of the eNB 20 transmits a radio resource release request signal to the terminal 30 in order to release radio resources established between the eNB 20 and the terminal 30. The radio resource release request signal is a signal called “RRC Connection Release”, for example. Moreover, the radio | wireless resource release reception part 122 of the terminal 30 will release the radio | wireless resource established between eNB20 and the terminal 30, if the radio | wireless resource release request signal is received from eNB20.

  In step S208, the radio resource management unit 111 of the eNB 20 transmits a connection release response signal to the MME 10e to notify the MME 10e that the radio resource established between the eNB 20 and the terminal 30 has been released. . The connection release response signal is a signal called “S1 UE Context Release Complete” used in S1AP, for example.

  In step S209, the location registration request unit 123 of the terminal 30 releases the radio resource established between the eNB 20 and the terminal 30, and further includes the non-broadcast TAI in the TA List stored in the terminal 30. Therefore, it is determined that it is necessary to request the location registration update from the network.

  In step S210, the location registration request unit 123 of the terminal 30 transmits to the eNB 20 a location registration update request signal including the GUTI stored in the terminal 30 (the GUTI updated by the processing procedure of step S202). To do. The location registration update request signal is, for example, a signal called “TAU Request”.

  In step S <b> 211, the location registration signal transmission / reception unit 112 of the eNB 20 notifies the selection unit 113 of GUTI included in the location registration update request signal received from the terminal 30. The selection unit 113 analyzes the GUTI notified from the location registration signal transmission / reception unit 112, and selects the MME 10 to which the location registration update request signal is to be transmitted based on the GUMME regarding all the MMEs 10 connected to the eNB 20.

  The selection unit 113 first extracts the MMEGI and MMEC included in the GUTI notified from the location registration signal transmission / reception unit 112. Subsequently, the selection unit 113 refers to the value of the seventh bit in the MMEC and confirms whether the MMEC is Normal-MMEC or Null-MMEC.

  When the MMEC is Normal-MMEC, the selection unit 113 is assigned one or more MCCs, MNCs, and MMEGIs that are the same as the MCCs, MNCs, and MMEGIs included in the GUTI notified from the location registration signal transmission / reception unit 112. One MME 10 is selected from the MMEs 10 (MME10d, MME10e, MME10f), and the selected MME10 is notified to the location registration signal transmission / reception unit 112.

  When all the MMEs 10 connected to the eNB 20 are core networks provided by the same mobile communication carrier, the selection unit 113 is the same as the MMEGI included in the GUTI notified from the location registration signal transmission / reception unit 112. One MME10 (MME10d, MME10e, MME10f) to which one MMEGI is assigned may be selected, and the selected MME10 may be notified to the location registration signal transmission / reception unit 112. . In this case, since the same value is set in the MCC and MNC of all the MMEs 10 connected to the eNB 20, it is sufficient for the eNB 20 to compare only the MMEGI.

  When the MMEC is Null-MMEC, the selection unit 113 is assigned one or more MCCs, MNCs, and MMEGIs that are the same as the MCCs, MNCs, and MMEGIs included in the GUTI notified from the location registration signal transmission / reception unit 112. Among the MMEs 10, any one MME 10 (MME 10d, MME 10f) other than the MME 10 (MME 10e) corresponding to the MMEC included in the GUTI notified from the location registration signal transmission / reception unit 112 is selected, and the selected MME 10 To the location registration signal transmitting / receiving unit 112.

  When all the MMEs 10 connected to the eNB 20 are core networks provided by the same mobile communication carrier, the selection unit 113 is the same as the MMEGI included in the GUTI notified from the location registration signal transmission / reception unit 112. Among the one or more MMEs 10 to which the MMEGI is assigned, any one of the MMEs 10 (MME10d, MME10f) other than the MME10 (MME10e) corresponding to the MMEC included in the GUTI notified from the location registration signal transmission / reception unit 112 One MME 10 may be selected and the selected MME 10 may be notified to the location registration signal transmission / reception unit 112. In this case, since the same value is set in the MCC and MNC of all the MMEs 10 connected to the eNB 20, it is sufficient for the eNB 20 to compare only the MMEGI.

  In the processing procedure of step S211, when the MMEC is Null-MMEC, the selection unit 113 sets the weight factor of the MME 10 corresponding to the Null-MMEC among the weight factors of all the MMEs 10 managed by the eNB 20 to zero. When the eNB 20 selects the MME 10 based on the weight factor of each MME 10, the eNB 20 may select the MME 10 other than the MME 10 having the weight factor of zero. Note that the weight factor is an element indicating the load state of the MME 10, and the MME 10 can notify the eNB 20 of the weight factor of the MME 10 itself through the S1-AP message.

  In the following description, the selection unit 113 continues the description on the assumption that the MME 10d has been selected.

  In step S212, the location registration signal transmission / reception unit 112 of the eNB 20 transmits a location registration update request signal to the MME 10d. The location registration update request signal includes the GUTI notified from the terminal 30 in step S210. The location registration update request signal is, for example, a signal called “TAU Request”.

  In step S213, the terminal information acquisition unit 104 of the MME 10d extracts the MMEC from the GUTI included in the location registration update request signal received in step S212, and identifies the MME 10 from the values of the 0th to 6th bits of the MMEC. In the example of FIG. 7, a code indicating the MME 10e is set in the 0th to 6th bits of the extracted MMEC as described in the processing procedure of step S202. Subsequently, the terminal information acquisition unit 104 transmits a mobile device information acquisition request signal to the MME 10e. The mobile device information acquisition request signal is a signal called, for example, “Context Request”.

  In step S214, the terminal information acquisition unit 104 of the MME 10e transmits a mobile device information acquisition response signal to the MME 10d. The mobile device information acquisition response signal includes the profile information of the terminal 30. The mobile device information acquisition request signal is a signal called, for example, “Context Response”.

  In step S215, the terminal information acquisition unit 104 of the MME 10d transmits a location registration update response signal to the terminal 30. The location registration update response signal is a signal called “TAU Accept”, for example.

<Effect>
As described above, when the MME 10 detects congestion, the mobile communication system according to the embodiment stores the GUTI including the Null-MMEC and the TA List including the non-broadcast TAI in the terminal 30, and once the terminal 30 and the network, The terminal 30 is urged to update the location registration by releasing the session established between the terminals. Further, the mobile communication system according to the embodiment notifies the eNB 20 of the GUTI including the Null-MMEC through the location registration update, so that the eNB 20 selects the MME 10 belonging to the same core network as the Null-MMEC. Made it possible to do. Thereby, even when the mobile communication system according to the embodiment has a plurality of core networks, when the reselection of the exchange is performed, the core network to which the terminal 30 is connected can be appropriately selected. .

  Further, the mobile communication system according to the embodiment includes information indicating whether or not the MME 10 is in a congested state in the seventh bit among the eight bits defined in the MMEC. Two states called “MMEC” and “Null-MMEC” are defined. Thereby, each device in the mobile communication system according to the embodiment can know the load state of the MME 10 based on the setting value of the MMEC.

  Further, when the MME 10 detects congestion, the mobile communication system according to the embodiment notifies the eNB 20 of the GUTI including the Null-MMEC via the terminal 30, and the eNB 20 becomes congested when reselecting the exchange. The MME10 that is not selected. Thereby, the mobile communication system according to the embodiment can appropriately select the MME 10 to which the terminal 30 is connected when reselection of the exchange is performed due to congestion of the exchange.

  In addition, the MME 10 according to the embodiment receives the profile information of the terminal 30 from the MME 10 to which the terminal 30 was last connected regardless of the setting value of “Normal-MMEC” or “Null-MMEC”. Made it possible to get. Thereby, the mobile communication system according to the embodiment can take over the profile information of the terminal 30 between the MMEs 10 even when the reselection of the exchange is performed due to the congestion of the exchange.

<Supplement of embodiment>
Although the embodiments of the present invention have been described above, the disclosed invention is not limited to the embodiments, and those skilled in the art will understand various variations, modifications, alternatives, substitutions, and the like. . Although specific numerical values have been used to facilitate understanding of the invention, these numerical values are merely examples, and any appropriate values may be used unless otherwise specified. The classification of items in the above description is not essential to the present invention, and the items described in two or more items may be used in combination as necessary, or the items described in one item may be used in different items. It may be applied to the matters described in (if not inconsistent). The boundaries between functional units or processing units in the functional configuration diagram do not necessarily correspond to physical component boundaries. The operations of a plurality of functional units may be physically performed by one component, or the operations of one functional unit may be physically performed by a plurality of components.

  As described above, all or part of the embodiments can be implemented by a program. This program can be stored in random access memory (RAM), flash memory, read only memory (ROM), EPROM, EEPROM, register, hard disk (HDD), removable disk, CD-ROM, database, server or any other suitable storage medium. It may be saved.

  As described above, in the embodiment, GUTI, GUMMEI, or MMEGI is an example of a network identifier. The identifier update request signal is an example of an identifier update signal. The identifier update request unit 102 is an example of a first transmission unit. The location registration update request signal is an example of a location registration update signal. The location registration signal transmission / reception unit 112 is an example of a reception unit and a second transmission unit. The non-broadcast TAI is an example of information that prompts updating of location registration. The identifier update receiving unit 121 is an example of a second receiving unit. The location registration request unit 123 is an example of a third transmission unit. Normal-MMEC and Null-MMEC are examples of an exchange identifier having a flag indicating the state of the exchange.

10 MME
20 eNB
30 terminal 101 load detection unit 102 identifier update request unit 103 session management unit 104 terminal information acquisition unit 111 radio resource management unit 112 location registration signal transmission / reception unit 113 selection unit 121 identifier update reception unit 122 radio resource release reception unit 123 location registration request unit

Claims (7)

A communication system having a plurality of exchanges belonging to each of a plurality of networks, and a base station apparatus connected to each of the plurality of exchanges,
The exchange is
A first transmitter for transmitting an identifier update signal including a network identifier for identifying a network to which the switch belongs based on a load state of the switch to a terminal;
The base station device
A receiving unit for receiving a location registration update signal including the network identifier from the terminal;
Based on the network identifier, a selection unit that selects a switch that transmits the location registration update signal from the plurality of switches belonging to the same network as the network indicated by the network identifier among the plurality of networks;
A second transmitter for transmitting the location registration update signal to the exchange selected by the selector;
A communication system.   The communication system according to claim 1, wherein the identifier update signal includes information that prompts the terminal to update location registration. The communication system includes the terminal,
The terminal
A second receiver for receiving the identifier update signal;
A third transmitter for transmitting the location registration update signal to the base station device, when the identifier update signal includes information prompting to update location registration;
The communication system according to claim 1, comprising: The first transmission unit transmits the identifier update signal to the terminal, which is an exchange identifier for identifying the exchange, and further includes an exchange identifier having a flag indicating a state of the exchange,
The selection unit selects a switch other than the switch indicated by the switch identifier from the plurality of switches belonging to the same network as the network indicated by the network identifier when a flag indicating the state of the switch is set; The communication system according to any one of claims 1 to 3.   The communication system according to claim 4, wherein the exchange includes an acquisition unit that acquires terminal information of the terminal from an exchange indicated by the exchange identifier. The exchange is an MME;
The base station device is an eNB;
The communication system according to any one of claims 1 to 3, wherein the identifier update signal and the location registration update signal are control signals used in an MME and an eNB. A communication control method executed in a communication system having a plurality of exchanges belonging to each of a plurality of networks and a base station apparatus connected to each of the plurality of exchanges,
The exchange is
Transmitting an identifier update signal including a network identifier for identifying a network to which the switch belongs based on a load state of the switch to a terminal;
The base station device
Receiving a location registration update signal including the network identifier from the terminal;
Selecting a switch that transmits the location registration update signal from the plurality of switches belonging to the same network as the network indicated by the network identifier among the plurality of networks based on the network identifier;
The exchange selected by said selecting step, and transmitting the location update signal,
A communication control method comprising:

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