Control device, base station device, control method, and program for performing access restrictions on the basis of network load

Abstract

To relieve a network overload state in a mobile communication system.SOLUTION: A control device operating as a Mobility Management Entity (MME) or Access and Mobility Management Function (AMF) in a cellular communication network of a third generation partnership project (3GPP) receives a connection request from a terminal device to the cellular communication network via a base station device, performs a first determination as to whether a value indicating the load of the control device or a value indicating the load of the cellular communication network exceeds a predetermined threshold, and, on the basis of the result of the first determination, requests the base station device to perform control to suppress transmission of connection requests to the terminal device.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a technique for mitigating network overload conditions in a mobile communication system. [Background technology]

[0002] In the 3rd Generation Partnership Project (3GPP) cellular communication standard, a terminal connecting to a cellular communication network performs procedures such as registering itself to the network and setting up a communication path via a base station. For example, in Long Term Evolution (LTE), such procedures for connecting a terminal are performed via a network node called a Mobility Management Entity (MME). Similarly, in the 5th generation mobile communication system (5G), procedures are performed via a network node called an Access and Mobility Management Function (AMF). Here, if a large number of terminals attempt to connect to the network in a short period of time, the network load may temporarily increase, resulting in an overload state. For example, if a large number of connection requests are made to an MME or AMF in a short period of time, a volume of processing may occur that exceeds the processing capacity of the MME or AMF. When the network becomes overloaded, the requested processing may not be able to be performed, and a failure may occur. Patent Document 1 describes a control device that, based on detection of congestion occurring in a specific AMF, commands a base station to start congestion control for the specific AMF. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-150938 Summary of the Invention [Problem to be solved by the invention]

[0004] It is possible to alleviate the overload state of an MME or AMF by requesting a base station to limit the number of connection requests from terminals forwarded to the overloaded MME or AMF. However, if a large number of connection requests continue, the processing volume for this may exceed the processing performance of the entire network, and the system may no longer function. The present invention provides a technology for alleviating the overload state of a network in such a situation. [Means for solving the problem]

[0005] A control device according to one embodiment of the present invention is a control device that operates as a Mobility Management Entity (MME) or an Access and Mobility Management Function (AMF) in a 3rd Generation Partnership Project (3GPP) cellular communication network, and has: a receiving means for receiving a connection request to the cellular communication network from a terminal device via a base station device; a determining means for making a first determination as to whether a value indicating the load of the control device or a value indicating the load of the cellular communication network exceeds a predetermined threshold; and a requesting means for requesting the base station device to perform control to suppress the transmission of the connection request to the terminal device based on the result of the determination. [Effects of the Invention]

[0006] According to the present invention, it is possible to alleviate network overload conditions in a mobile communication system. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a mobile communication system. [Figure 2] FIG. 10 is a diagram illustrating an example of a sequence executed between an MME and a base station. [Figure 3] FIG. 2 is a diagram illustrating an example of a hardware configuration of an MME. [Figure 4] FIG. 1 is a diagram illustrating an example of the functional configuration of an MME. [Figure 5] FIG. 2 is a diagram illustrating an example of a functional configuration of a base station. [Figure 6] 10 is an example of a flowchart illustrating an operation flow of an MME. [Figure 7] 10 is an example of a flowchart illustrating an operation flow of an MME. [Figure 8] 10 is an example of a flowchart illustrating an operation flow of an MME. [Figure 9] 10 is an example of a flowchart illustrating an operation flow of an MME. [Figure 10] FIG. 10 is a diagram illustrating an example of a sequence executed between an MME, a base station, and a terminal. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention as claimed, and not all combinations of features described in the embodiments are necessarily essential to the invention. Two or more of the features described in the embodiments may be arbitrarily combined. Furthermore, the same reference numerals are used for the same or similar components, and redundant explanations will be omitted.

[0009] (System Configuration) FIG. 1 shows an example of the configuration of a mobile communication system according to this embodiment. The mobile communication system is, for example, a cellular communication system that complies with the cellular communication standard of the Third Generation Partnership Project (3GPP (registered trademark)). However, the present invention is not limited to this, and the following discussion can be applied to a mobile communication system that complies with any wireless communication standard. The mobile communication system includes, for example, terminals 101 to 104, base stations 111 to 112, MMEs 121 to 124, HSS 131, SGW 132, PGW 133, IMS 134, and the Internet 135. MME and HSS are abbreviations for Mobility Management Entity and Home Subscriber Server, respectively. SGW, PGW, and IMS are abbreviations for Serving Gateway, Packet Data Network Gateway, and IP Multimedia Subsystem, respectively. The terminals 101 to 104 may be collectively referred to as terminals 100. The base stations 111 and 112 may be collectively referred to as base station 110. Furthermore, MMEs 121 to 124 may be collectively referred to as MME 120. Note that FIG. 1 shows an example in which terminals 101, 102, 103, and 104 are wirelessly connected to base station 111 and base station 112, respectively, but the number of terminals 100 connected to each base station 110 may be zero, one, or three or more. Also, there may be three or more base stations 110. Each terminal 100 may be connected to multiple base stations 110. Each of base station 111 and base station 112 is mutually connected to each of MMEs 121 to MME 124 via a wired network. Note that the number of MMEs 120 may be three or less, or five or more. Also, the base station 110 and MME 120 may be connected via a wireless network. Each of the MMEs 120 is connected to another via a wired network or a wireless network (not shown), and communication may be performed between them. Each of the MMEs 121 to 124 may be further connected to the HSS 131 via a wired network or a wireless network. Each of the base stations 111 and 112 may be connected to the SGW 132 via a wired network or a wireless network.Each of the MMEs 121 to 124 may be connected to the SGW 132 via a wired or wireless network (not shown). The SGW 132 may be connected to the PGW 133 via a wired or wireless network. The PGW 133 may be connected to the IMS 134 and the Internet 135 via a wired or wireless network.

[0010] The terminal 100 is a terminal used by a user, and exchanges radio signals with the base station 110 via a wireless medium. The terminal 100 may be called User Equipment (UE). The terminal 100 includes, for example, a smartphone, a mobile phone, a personal computer, a tablet terminal, a wearable terminal, an IoT (Internet of Things) terminal, etc. The base station 110 exchanges radio signals with the terminal 100 via a wireless medium. The base station 110 includes, for example, a gNB (next generation Node B), an eNB (evolved Node B), etc.

[0011] The MME 120 accommodates the base station 110 and provides mobility control for the terminal 100. For example, the MME 120 can perform mobility control such as location registration, paging, and handover for the terminal 100, and can establish and delete bearers. The MME 120 can also provide a function for authenticating the terminal 100 based on authentication information notified from the HSS 131. The MME 120 can provide the SGW 132 with the setting of a forwarding path for data packets. The HSS 131 is a subscriber information database and manages the authentication information and location information of the terminal 100. For example, the HSS 131 provides the authentication information and location information of the terminal 100 to the MME 120 in response to a request from the MME 120.

[0012] The SGW 132 relays data packets received from the terminal 100 via the base station 110 to the PGW 133. The SGW 132 also relays data packets addressed to the terminal 100 received via the PGW 133 to the base station 110. The PGW 133 forwards data packets received from the terminal 100 via the SGW 132 to an appropriate destination. For example, the PGW 133 forwards the data packets received from the terminal 100 to the IMS 134 or the Internet 135 depending on the type of the data packet. The IMS 134 and the Internet 135 are examples of networks that provide data services to the terminal 100, and networks that can be targets of the data packet forwarding function provided by the PGW 133 to the terminal 100 are not limited to these. The IMS 134 is a network that provides IP (Internet Protocol)-based multimedia services to the terminal 100. For example, the IMS 134 provides services such as voice calls between multiple terminals 100. The Internet 135 includes external networks and servers to which the terminal 100 can connect via a mobile communication system.

[0013] Although the above describes an example of the configuration of a mobile communication system based on Long Term Evolution (LTE) and Evolved Packet Core (EPC) defined by 3GPP, this embodiment can also be applied to other mobile communication system configurations. For example, this embodiment can also be applied to a fifth-generation (5G) mobile communication system defined by 3GPP. In this case, for example, the above functions provided by the MME 120, SGW 132, and PGW 133 can be provided by an AMF that performs mobility control in the 5G mobile communication system, an SMF that performs session management, and a UPF that routes and forwards data packets. AMF, SMF, and UPF are abbreviations for Access and Mobility management Function, Session Management Function, and User Plane Function, respectively. Furthermore, for example, the above functions provided by the HSS 131 can be provided by a UDM that manages subscriber information and authentication information, a UDR that stores subscriber information, policy information, etc., and an AUSF that authenticates terminals. Note that UDM, UDR, and AUSF are abbreviations for Unified Data Management, User Data Repository, and Authentication Server Function, respectively. In addition, 5G Core (5GC) in a 5G mobile communication system corresponds to EPC in a mobile communication system based on LTE.

[0014] An example of a procedure when the terminal 100 connects to a network in the mobile communication system of this embodiment will be described. First, when the terminal 100 wirelessly accesses the base station 110, a wireless control link is established between the terminal 100 and the base station 110. The terminal 100 transmits a connection request (also called an attach request) to the MME 120 via the wireless control link. At this time, the MME 120 to which the connection request is to be transmitted may be determined by, for example, the base station 110 from among MMEs 121 to 124. The MME 120 may execute a security procedure in response to the connection request from the terminal 100. For example, the security procedure may involve the exchange of messages related to authentication, encryption, and the like. Upon completion of the security procedure, the MME 120 transmits a location registration request message to the HSS. The HSS 131 associates the terminal 100 with the MME 120 and stores the association based on the location registration request message.

[0015] Next, the MME 120 transmits a bearer setup request to the SGW 132 to set up a communication path for data packets from the terminal 100. Upon receiving the bearer setup request, the SGW 132 transmits a path setup request to the PGW 133. The PGW 133 assigns an IP address to the terminal 100 and transmits a path setup response message including the assigned IP address to the SGW 132. This establishes a communication path for this IP address between the PGW 133 and the SGW 132. The SGW 132 transmits a bearer setup response signal to the MME 120. This bearer setup response signal can include information required for bearer setup in the direction from the base station 110 to the SGW 132 and information about the IP address assigned to the terminal 100.

[0016] The MME 120 notifies the terminal 100 via the base station 110 of a context setting request signal including the information received in the bearer setting response signal and a connection completion notification. Upon receiving the context setting request signal, the base station 110 establishes a wireless data link with the terminal 100 and transmits a connection completion notification to the terminal 100. The base station 110 also sets up a bearer in the direction from the base station 110 to the SGW 132 and transmits a context setting response to the MME 120. The context setting response may include information required for bearer setup in the direction from the SGW 132 to the base station 110. Upon receiving the connection completion notification, the terminal 100 notifies the MME 120 of a connection completion response. This completes registration of the terminal 100 with the network. The MME 120 notifies the SGW 132 of a bearer update request signal including the information received in the context setting response. The SGW 132 sets up a bearer in the direction from the SGW 132 to the base station 110, and upon completion of the setup, transmits a bearer update response to the MME 120. This completes the setting of the communication path from the terminal 100 to the PGW 133.

[0017] As described above, when a terminal 100 initiates a connection to a network in a mobile communication system, processes such as registering the terminal 100 with the network and setting up a communication path are performed by exchanging messages between network nodes mainly under the control of the MME 120. Here, if a large number of terminals 100 initiate connection requests to the network within a short period of time, and the resulting processing load exceeds the processing capacity of the MME 120 or other network nodes, congestion may occur. For example, if the MME 120 cannot process a connection request from the terminal 100, a call loss to the terminal 100 may occur. To avoid such a situation, the mobile communication system may be configured to include multiple MMEs 120, and the base station 110 may assign an MME 120 to which a connection request from the terminal 100 is to be forwarded depending on the status of each MME 120. For example, if the processing load on the MME 120 increases to the point where it exceeds its processing capacity, the MME 120 may notify the base station 110 not to forward the request to the MME 120.

[0018] FIG. 2 shows an example sequence when the MME 120 notifies the base station 110 of an overload. When the MME 120 detects that an overload has occurred in the MME 120 (S201), the MME 120 notifies the base station 110 of the overload (S202). For example, the overload notification from the MME 120 to the base station 110 can be performed based on the S1 interface, which defines communication between the MME 120 and the base station 110. For example, the MME 120 can notify the base station 110 of an OVERLOAD START message defined in the S1 interface. The OVERLOAD START message can include information indicating a specific type of communication to be rejected or permitted (emergency call, non-emergency call, prioritized session, delay-tolerant access, etc.), a percentage indicating the rate at which forwarding of connection requests is reduced, and the like. Upon receiving the overload notification, the base station 110 performs load control (S203). Based on the information included in the OVERLOAD START message, the base station 110 can control forwarding of connection requests to the MME 120, the source of the message. In this way, by the base station 110 controlling the number of connection requests forwarded to an overloaded MME 120, congestion in that MME 120 can be avoided. However, when the base station 110 controls the number of connection requests forwarded to a specific MME 120 to reduce the number of connection requests forwarded to that MME 120, the number of connection requests forwarded to other MMEs 120 increases. For example, in FIG. 1, when an overload occurs in the MME 123, the MME 123 notifies each of the base stations 110 of the overload. Based on this, each of the base stations 110 reduces the number of connection requests forwarded to the MME 123 and transfers the processing to the MMEs 121, 122, and 124. As a result, if the processing load in another MME 120 increases to the point where it exceeds its processing capacity, that MME 120 may similarly notify the base station 110 of the overload. For example, when the MME 121 notifies the base station 110 of the overload, subsequent connection requests are mainly forwarded to the MMEs 122 and 124. If this situation expands and all of the MMEs 120 are in an overloaded or high-load state, processing of connection requests from the terminals 100 may become delayed.If there is no response to a connection request to the network, terminal 100 may repeatedly retransmit the request, which may result in congestion not being resolved and connection requests remaining unprocessed, potentially spreading the impact to the mobile communication system or causing long-term congestion.

[0019] In consideration of these circumstances, the MME 120 in this embodiment requests the base station to perform control to suppress transmission of connection requests to terminal devices when the load on the MME 120 itself or the load on the network increases beyond a predetermined threshold. For example, upon detecting an overload in the MME 120, the MME 120 requests the base station 110 to notify the base station 110 of access restriction to control the transmission of connection requests by the terminal 100. As an example, the MME 120 monitors the usage rate of the CPU, memory, etc. in the MME 120, and if the usage rate exceeds a predetermined threshold, may transmit a request for access restriction to the base station 110. CPU stands for Central Processing Unit. Then, upon receiving the request for access restriction, each base station 110 notifies the base station 110 that transmission of connection requests by the terminal 100 in the cell configured by the MME 120 is restricted. For example, the base station 110 notifies the base station 110 of the access restriction. Each terminal 100 that receives the notification of access restriction makes a connection request based on predetermined conditions. For example, a connection request based on a predetermined condition may involve drawing a random number before making a connection request, and making the connection request if the value of the random number is within a predetermined range; otherwise, waiting for a predetermined period without making the connection request. This suppresses the transmission of connection requests by the terminal 100, thereby making it possible to reduce the number of connection requests forwarded to an overloaded MME 120 without transferring the load to other MMEs 120 or causing a backlog of unprocessed connection requests. Note that the base station 110 may stop transmitting radio waves as a control to suppress transmission of connection requests to the terminal 100. When the base station 110 stops transmitting radio waves, the terminal 100 is unable to detect a cell formed by the base station 110, and therefore the terminal 100 may be suppressed from transmitting a connection request. In the following, an example of causing the base station 110 to perform access restriction on the terminal 100 will be described as a control to suppress transmission of connection requests by the base station 110 to the terminal 100. However, this example can also be applied to a case where the base station 110 stops transmitting radio waves to suppress transmission of connection requests to the terminal 100.

[0020] Furthermore, the MME 120 may request access restriction from the base station 110 when an overload occurs in the MME 120 itself and when the load of another MME 120 exceeds a predetermined threshold. The MME 120 determines whether to request access restriction by taking into consideration not only the overload in the MME 120 itself but also the overload in another MME, thereby preventing excessive requests for access restriction. For example, if an overload occurs in a specific MME 120 due to a factor other than a connection request from the terminal 100, and the MME 120 requests access restriction, the connection request may be restricted even though the other MME 120 is capable of processing the request. In such a case, the specific MME 120 can check the load status of the other MME 120 to prevent excessive requests for access restriction. The MME 120 may request access restriction from the base station 110 based on the overload in a network node other than the MME. For example, when the MME 120 transmits a predetermined message to another network node upon receiving a connection request, the MME 120 acquires the number of predetermined messages transmitted by the MME 120 itself as well as the number of messages transmitted by the other MMEs 120. The MME 120 may request access restriction from the base station 110 when the sum of the number of messages transmitted to the other network nodes within a predetermined period of time exceeds a predetermined threshold. This enables access restriction even in a situation where a network failure occurs due to an overload in a network node other than the MME 120, thereby enabling the overload in the device to be quickly resolved. The network node other than the MME may be, for example, the HSS 131, the SGW 132, the PGW 133, the IMS 134, the Internet 135, etc. The network node other than the MME may also be a device other than these.

[0021] (Circuit configuration) An example of the configuration of the MME 120 and base station 110 described above will be described. FIG. 3 is a diagram showing the hardware configuration of the MME 120 and base station 110. In one example, the MME 120 and base station 110 are configured to include a processor 301, a ROM 302, a RAM 303, a storage device 304, and a communication circuit 305. The processor 301 is a computer configured to include one or more processing circuits, such as a general-purpose CPU (Central Processing Unit) or an ASIC (Application Specific Integrated Circuit). The processor 301 reads and executes programs stored in the ROM 302 or the storage device 304, thereby performing overall processing of the device and each of the above-mentioned processes. The ROM 302 is a read-only memory that stores programs related to processing performed by the device, various parameters, and other information. The RAM 303 functions as a workspace when the processor 301 executes a program, and is a random access memory that stores temporary information. The storage device 304 is configured, for example, by a removable external storage device. The communication circuit 305 is configured, for example, by including a circuit for communicating with other devices.

[0022] (Functional configuration) FIG. 4 is a diagram illustrating an example of the functional configuration of the MME 120. The MME 120 includes, as its functions, a connection acceptance unit 401, a load determination unit 402, a suppression request unit 403, and an information acquisition unit 404, for example. FIG. 4 illustrates the functional configuration of the MME 120 according to this embodiment, and omits, for example, a general MME configuration. These functional units may be implemented, for example, by the processor 301 executing a program stored in the ROM 302 or the storage device 304 and controlling the communication circuit 305 as necessary. However, this is not limiting, and for example, dedicated hardware may be provided to implement each function. The connection acceptance unit 401 accepts a connection request to the network from the terminal 100 via the base station 110. The load determination unit 402 determines whether the MME 120 or the network is overloaded. For example, the load determination unit 402 determines whether a value indicating the load of the MME 120 or a value indicating the load of the mobile communication network exceeds a predetermined threshold. The load determination unit 402 may determine whether the overload has been resolved after the suppression request unit 403 notifies the base station 110 of a request to suppress connection requests. Based on the result of the determination by the load determination unit, the suppression request unit 403 requests the base station 110 to perform control to suppress transmission of connection requests to the terminal 100. Based on the result of the determination by the load determination unit, the suppression request unit 403 may also request the base station 110 to release control to suppress transmission of connection requests to the terminal 100. The information acquisition unit 404 acquires information capable of identifying the utilization rate of the computational resources of each of one or more other MMEs in the mobile communication network. The information acquisition unit 404 may also acquire information capable of identifying the number of predetermined messages that each of the other MMEs has transmitted to a predetermined network node based on a connection request. This information may be used for the determination by the load determination unit 402.

[0023] FIG. 5 is a diagram illustrating an example of the functional configuration of the base station 110. The base station 110 includes, as its functions, a connection request forwarding unit 501, a suppression request receiving unit 502, and a restriction notification unit 503. FIG. 5 illustrates the functional configuration of the base station 110 according to this embodiment, and omits, for example, the general configuration of a base station. These functional units may be implemented, for example, by the processor 301 executing a program stored in the ROM 302 or the storage device 304 and controlling the communication circuit 305 as necessary. However, this is not limiting, and, for example, dedicated hardware may be provided to implement each function. The connection request forwarding unit 501 forwards a network connection request received from the terminal 100 to the MME 120. The suppression request receiving unit 502 receives a request from the MME 120 to perform control to suppress transmission of connection requests to the terminal 100 based on overloading of the MME 120 or the mobile communication network. Furthermore, the suppression request receiving unit 502 receives from the MME 120 a request to release control for suppressing the transmission of connection requests to the terminal 100. The restriction notification unit 503 notifies the terminal 100 to restrict the transmission of connection requests. For example, the restriction notification unit 503 can notify, by broadcasting, that the transmission of connection requests in a cell configured by the terminal itself is to be restricted.

[0024] (Processing flow) (Processing example 1) FIG. 6 shows an example of a flowchart of the operation when the MME 120 requests the base station 110 to suppress connection requests in this processing example. Here, the suppression of connection requests can be performed by access restriction, stopping radio wave transmission, etc. The access restriction can be performed by the base station 110 notifying the terminal 120 to perform a predetermined operation when transmitting a connection request, in order to restrict the terminal 120 from transmitting a connection request. The predetermined operation can be performed by the terminal 100 drawing a random number before transmitting a connection request, as described above, and making a connection request if the value of the random number is within a predetermined range, or waiting for a predetermined period without making a connection request otherwise. The following describes an example of suppressing connection requests by access restriction.

[0025] First, the MME 120 determines whether an overload state occurs in the MME 120 (S601). For example, the MME 120 monitors the load status of the MME 120 and determines whether a predetermined condition is met. As an example, the MME 120 may periodically check the usage rate of the computing resources of the MME 120, such as the CPU and memory, and determine whether the predetermined condition is met. For example, the predetermined condition may be that the usage rate of the computing resources exceeds a predetermined threshold. The predetermined threshold may be a different threshold for each computing resource, or may be a common threshold for some computing resources.

[0026] The method by which MME 120 determines whether an overload state has occurred in its own device is not limited to the above. For example, MME 120 may determine the load state based on the number of connection requests received or processed by its own device per unit time. As an example, MME 120 may determine that an overload state has occurred if the number of connection requests received or processed by its own device per unit time exceeds a predetermined threshold. If the functions provided by MME 120 are provided by multiple cards, and each card is configured to independently process connection requests, for example, MME 120 may count the number of connection requests received or processed per unit time for each card. Then, MME 120 may determine whether an overload state has occurred by comparing the number of connection requests counted for each card with a predetermined threshold. In this case, MME 120 may determine that an overload state has occurred in its own device based on the occurrence of an overload state in any one of the cards, or may determine that an overload state has occurred in its own device based on the total number of connection requests in two or more cards exceeding a predetermined threshold. Furthermore, MME 120 may determine that an overload state has occurred in its own device based on the result of comparing the number of connection requests with the predetermined threshold for each card and finding that the number of connection requests in a predetermined number of cards or more exceeds the predetermined threshold. When MME 120 determines that an overload state has occurred because the load situation in its own device satisfies a predetermined condition (YES in S601), it executes the process of S602. On the other hand, when MME 120 determines that the load situation in its own device does not satisfy the predetermined condition (NO in S601), it periodically repeats the determination of S601.

[0027] When the MME 120 determines that an overload state occurs in the MME 120, it requests access restriction from the base station 110 (S602). For example, the MME 120 can request access restriction from each base station 110 using the S1 interface. For example, the MME 120 can request access restriction from the base station 110 by adapting the Overload Start procedure defined for the S1 interface. As an example, the MME 120 can request access restriction by including a new information element indicating a request for access restriction in an OVERLOAD START message used in the Overload Start procedure. Note that the MME 120 can request access restriction by adapting an existing information element in the OVERLOAD START message. For example, the MME 120 can indicate a request for access restriction by using an unused value of the Overload Action IE. Note that the S1 interface is a general term for the interface between the base station and the EPC. For example, the interface between the base station and the MME can be called an S1-MME. In other words, if the MME 120 can request access restriction using the S1 interface, which is a standard interface between a base station and the MME, it becomes possible to efficiently request access restriction without providing each base station 110 with a special interface for requesting access restriction and without major modifications. The method by which the MME 120 requests access restriction using the S1 interface is not limited to the above. For example, the MME 120 may use a new procedure defined for the S1 interface to request access restriction. By providing a new procedure for requesting access restriction, efficient message transmission and reception can be achieved without being restricted by existing procedures or message formats. Furthermore, when the MME 120 establishes a new S1 interface with a base station after access restriction becomes necessary, the MME 120 may request access restriction in the procedure for establishing the S1 interface. For example, the MME 120 may request access restriction in an S1 Setup Response.In this case, upon receiving an S1 SETUP REQUEST from the base station 110, the MME 120 determines whether access restriction is necessary, and if it determines that access restriction is necessary, it may indicate a request for access restriction in an S1 SETUP RESPONSE. In this case, the MME 120 may request access restriction by reusing an existing information element in an existing S1 SETUP RESPONSE message. The MME 120 may also use a new information element in the existing S1 SETUP RESPONSE message to request access restriction. Note that, when suppressing connection requests by stopping the transmission of radio waves from the base station 110, the MME 120 may request the base station 110 to stop transmitting radio waves using the S1 interface. In this case, too, the request to stop transmitting radio waves may be notified from the MME 120 to the base station 110 in an OVERLOAD START message or the like.

[0028] The MME 120 may request access restriction from multiple base stations 110. For example, the MME 120 may request access restriction from all base stations 110 associated with the MME 120. In this case, if there is a method for specifying multiple destinations at once as a method for specifying the destination of an S1 message or the like requesting access restriction, the MME 120 may distribute the access restriction request using this method. As a result, the MME 120 may request access restriction from all base stations 110 associated with the MME 120 at once in a short time with little load. Furthermore, if there is a method for specifying multiple base stations 110 that satisfy predetermined conditions at once, the MME 120 may request access restriction using this method. For example, when the MME 120 wants to perform access restriction on cells configured in a specific area, the MME 120 may request access restriction using information (such as a TAI) that can identify cells corresponding to the specific area (cells that satisfy geographical conditions). TAI is an abbreviation for Tracking Area Identifier. The MME 120 may also request access restriction from a specific base station 110. For example, the MME 120 may count the number of connection requests received for each base station 110 associated with the MME 120, and if the number of connection requests received from a specific base station 110 alone exceeds a predetermined threshold, the MME 120 may request access restriction for that specific base station 110. If an excessive number of connection requests are transmitted in a specific cell due to congestion or the like, and access restriction is performed for each cell based on this, access restriction that is not actually required may be performed. The MME 120 may check the status of each base station 110 and select the base station for which access restriction is to be requested, thereby preventing excessive access restriction.

[0029] Next, the operations of the base station 110 and the terminal 100 will be described. When the base station 110 receives a request for access restriction, it notifies the cell that includes the base station 110 of the access restriction. For example, the base station 110 may notify the cell of the access restriction using System Information Block 2 (SIB2). The method by which the base station 110 notifies the cell of the access restriction is not limited to the above. For example, the base station 110 may notify the access restriction using a Master Information Block (MIB) or another SIB. The base station 110 may uniformly impose access restriction regardless of the type of communication or service, or may vary the presence or absence of access restriction and the conditions for access restriction depending on the type of communication or service. For example, the base station 110 may not impose access restriction on emergency calls, priority sessions, etc. The base station 110 may specify a predetermined restriction rate in the notification of access restriction. For example, if the restriction rate can range from 0% to 100% and 30% is specified as the restriction rate, 30% of calls will be restricted and 70% of calls will be allowed to be made.

[0030] When the terminal 100 receives access restriction, it determines whether to transmit a connection request based on the information included in the access restriction. For example, if connection requests are uniformly restricted regardless of the type of communication or service, the terminal 100 does not transmit a connection request. Furthermore, if access restriction is specified depending on the type of communication or service, the terminal 100 determines whether to transmit a connection request based on the type of service the terminal 100 is attempting to receive or the type of communication the terminal 100 is attempting to perform. That is, if the terminal 100 is attempting to perform a type of communication or service for which the transmission of a connection request is restricted, the terminal 100 does not transmit a connection request. Furthermore, if the terminal 100 is attempting to perform a type of communication or service for which the transmission of a connection request is permitted or not restricted, the terminal 100 may transmit a connection request. On the other hand, if a restriction rate is set in the access restriction, the terminal 100 may subtract a random number and determine whether to transmit a connection request based on the value. For example, if the restriction rate is specified as 30% and the random number (ranging from 0 to 100) is 20, the terminal 100 does not transmit a connection request. On the other hand, if the value of the random number is 50, the terminal 100 may transmit a connection request.

[0031] As described above, in this embodiment, MME 120 determines whether or not to implement access restriction based on whether or not an overload state has occurred in the MME itself, and requests access restriction to base station 110 based on the determination result. Each base station 110 then notifies the terminal 100 that access restriction should be implemented within the cell configured by the MME itself, and the terminal 100 that receives this notification determines whether or not to accept a connection request based on the conditions indicated as information regarding access restriction. This enables MME 120 to reduce its own load without transferring the load to other MMEs.

[0032] (Processing example 2) In the processing example 1, an example was described in which the MME 120 requests suppression of connection requests based on the occurrence of an overload state in the MME 120 itself. In this example, the MME 120 determines whether to request suppression of connection requests by taking into account the load states of other MMEs in addition to the occurrence of an overload state in the MME 120 itself. FIG. 7 shows an example of a flowchart of the operation when the MME 120 in this example requests suppression of connection requests from the base station 110. In FIG. 7, the same reference numerals are assigned to operations similar to those in FIG. 6, and descriptions thereof will be omitted. First, the MME 120 determines whether an overload state has occurred in the MME 120 itself (S601). The same method as in processing example 1 can be applied as a method for the MME 120 to determine whether an overload state has occurred in the MME 120 itself. Then, when the MME 120 determines that an overload state has occurred in the MME 120 itself (YES in S601), the MME 120 checks the load states of other MMEs other than the MME 120 itself and determines whether a predetermined condition is met (S701). For example, MME 120 may acquire the utilization rate of the computational resources of each of the other MMEs other than its own device and determine whether the utilization rate exceeds a predetermined threshold. Note that the predetermined threshold may be different from the threshold used to determine whether an overload state has occurred in its own device in S601. For example, MME 120 may set a first threshold used to determine whether an overload state has occurred in its own device higher than a second threshold used to determine whether an overload state has occurred in the other MMEs. That is, MME 120 may determine that an overload has occurred in its own device based on the utilization rate of its own device exceeding the first threshold, and may additionally determine that the network is overloaded based on the utilization rate of the computational resources of the other MMEs exceeding the second threshold. In this way, MME 120 can request access restriction using the occurrence of an overload in its own device as a trigger before the overload state in the other MMEs becomes severe. Furthermore, MME 120 may set the first threshold lower than the second threshold.That is, when the MME 120 determines that an overload has occurred in its own device and also determines that an even greater overload has occurred in another MME, the MME 120 can request access restriction before the overload spreads to the other MME. The first threshold and the second threshold may be the same. This allows the MME 120 to request access restriction after confirming that the same level of load as that of the own device has occurred in the other MME. The MME 120 may also determine that an overload has occurred in the other MME based on the increase in computational resources per unit time in the other MME. For example, when the computational resources in the own device exceed the first threshold, the MME 120 performs an overload procedure with the base station 110 to request that the base station 110 reduce connection requests to the own device. After the MME 120 performs the overload procedure, the MME 120 determines that access restriction should be requested when the increase in the computational resource usage rate per unit time in the other MME exceeds a predetermined threshold. That is, the MME 120 may determine that a load exceeding the allowable amount has occurred in the other MME as a result of the connection request that the MME 120 should process being transferred to the other MME 120. This allows the MME 120 to request access restriction after confirming that the connection request that the MME 120 should process cannot be transferred to the other MME 120.

[0033] The method by which the MME 120 determines the load status of another MME 120 is not limited to the above. For example, the MME 120 may determine the load status based on the number of connection requests received or processed by the other MME 120 per unit time. As an example, the MME 120 may acquire from the other MME 120 the number of connection requests received or processed by the other MME 120 per unit time, and determine that an overload has occurred if the number of connection requests exceeds a predetermined threshold. As with the threshold used in the determination using the computing resource usage rate described above, the predetermined threshold may be a first threshold for determining the occurrence of an overload in the MME 120 itself and a second threshold for determining the occurrence of an overload in the other MME 120, which may be different or the same. Note that the MME 120 may periodically exchange the computing resource usage rate or the number of connection requests received or processed per unit time with the other MME. By periodically exchanging the information, it becomes possible to quickly determine the occurrence of an overload in the other MME if an overload has occurred in the MME 120 itself. On the other hand, when the MME 120 detects an overload in itself, it may acquire from other MMEs the utilization rate of computing resources and the number of connection requests accepted or processed per unit time. This makes it possible to avoid constant communication and processing for monitoring. When the MME 120 determines that the load status of other MMEs exceeds a predetermined threshold (YES in S701), it requests access restriction from the base station 110 (S602). The MME 120 may request access restriction from each base station 110 using a method similar to that in Processing Example 1.

[0034] Note that when MME 120 acquires information indicating the load status from multiple other MMEs and requests access restriction based on the load values ​​of each of the other MMEs identified by the information, it may request access restriction based on the load value of any one of the other MMEs exceeding a predetermined second threshold. This makes it possible to suppress an increase in load before the overload spreads to multiple other MMEs. Furthermore, MME 120 may request access restriction based on the number of other MMEs whose load values ​​exceed the second threshold exceeding a third threshold. This makes it possible to request access restriction after confirming that the overload is spreading not only to a specific MME but also to a certain number or more of MMEs, thereby avoiding excessive requests for access restriction. Furthermore, MME 120 may determine the load status of other MMEs based on statistical information of the load values ​​acquired from the other MMEs. For example, MME 120 may determine that an overload is occurring in another MME based on the average value of the load values ​​acquired from the other MMEs exceeding the second threshold. This makes it possible to determine whether an overload is occurring based on the load state at the network level, regardless of the load state of a specific other MME.

[0035] As described above, in this processing example, MME 120 determines whether or not to request suppression of connection requests based on the load status of other MMEs in addition to the occurrence of an overload state in the MME itself, and requests suppression of connection requests to base station 110. With this configuration, MME 120 can request suppression of connection requests after confirming that high loads are also occurring in other MMEs. This makes it possible to prevent MME 120 from excessively requesting suppression of connection requests even in cases where other MMEs are capable of processing.

[0036] (Processing example 3) In the processing examples 1 and 2, the suppression of connection requests was described based on the occurrence of an overload state in the MME 120. In this example, the suppression of connection requests is described based on the prediction that an overload state has occurred in a network node other than the MME 120. In this processing example, the MME 120 operates to predict the occurrence of an overload in a network node other than the MME, such as the HSS 131, the SGW 132, or the PGW 133, and to request the suppression of connection requests. For example, the HSS 131 may be connected to and shared by multiple MMEs 120. Therefore, when connection requests are received from multiple terminals 100, even if each of the multiple MMEs 120 is capable of processing the connection requests assigned to it, the HSS 131 may not be able to process the location registration request messages transmitted by each MME 120. Similarly, when connection requests are received from a large number of terminals 100, each of the multiple MMEs 120 may notify the SGW 132 of a bearer setup request, which in turn may notify the PGW 133 of a path setup request. As a result, the SGW 132 and the PGW 133 may be unable to process the requests notified to them. Even in these cases, the MME 120 may request the base station 110 to suppress connection requests by predicting the occurrence of overload in the HSS 131, the SGW 132, the PGW 133, etc. FIG. 8 shows an example of a flowchart of the operation when the MME 120 requests the base station 110 to suppress connection requests in this processing example. Note that the same reference numerals are used for operations similar to those in FIG. 6, and description thereof will be omitted.

[0037] First, each MME 120 counts the number of predetermined messages transmitted from itself to another predetermined network node per unit time. For example, when the MME 120 receives a connection request from the terminal 100, the MME 120 may count the number of location registration request messages and the like transmitted to the HSS 131. Furthermore, when the MME 120 receives a connection request from the terminal 100, the MME 120 may count the number of bearer establishment requests and the like transmitted to the SGW 132. A predetermined network node may receive messages from multiple MMEs 120 and perform processing accordingly. Here, the MME 120 acquires information that can identify the number of messages transmitted by other MMEs to a predetermined network node per unit time (S801). For example, the MME 120 may acquire the number of messages transmitted from each of the other MMEs to the predetermined network node per unit time. For example, the MME 120 may acquire a total value for a predetermined type of message. As an example, the MME 120 may acquire the number of location registration request messages transmitted by each MME to the HSS 131 per unit time. The MME 120 may also acquire the number of bearer establishment request messages transmitted by each MME to the SGW 132 per unit time. The predetermined types of messages acquired by the MME 120 are not limited to these, and may include messages that trigger processes that may cause overload in the HSS 131, the SGW 132, the PGW 133, etc. The MME 120 determines whether the sum of the number of transmitted predetermined messages counted by the MME 120 and the number of transmitted predetermined messages acquired from other MMEs 120 exceeds a predetermined threshold (S802). For example, the MME 120 may determine whether the sum of the number of transmitted messages counted by the MME 120 and the number of transmitted messages acquired from other MMEs 120 exceeds a predetermined threshold. A different value may be set for each network node or message, or the same value may be set for some of them. Furthermore, the predetermined threshold may be set individually for each device depending on the performance of the network node.As an example, if the number of messages that can be processed per unit time is determined based on the processing performance of a specific network node, a predetermined threshold may be set based on the processable number of messages so that the number of messages does not exceed the processable number of messages. For example, if the functions provided by the network node are configured using virtualization technology, the predetermined threshold may be dynamically set based on the computing resources allocated to the network node. The MME 120 determines whether to request access restriction based on the determination result. For example, if the total number of messages transmitted to the specific network node per unit time is below the predetermined threshold, the MME 120 may determine not to request access restriction (NO in S802). On the other hand, if the total number of messages transmitted to the specific network node per unit time is above the predetermined threshold (YES in S802), the MME 120 may determine to request access restriction. In this case, the MME 120 may request access restriction from each base station 110 using a method similar to that of processing example 1 (S602).

[0038] The method by which the MME 120 determines whether an overload has occurred in the network is not limited to the above, and may be any method capable of predicting that an overload will occur in a network node or that network traffic is overloaded. The MME 120 may recognize that the SGW 132 will transmit a path setup request to the PGW 133 when it receives a bearer setup request. That is, the MME 120 may predict, based on the number of messages it has sent to a specific network node, that the utilization rate of computing resources in a network node other than the destination of the message will increase. Therefore, the network nodes from which the MME 120 predicts an overload are not limited to the above, and the determination in step S802 may be performed on any network node in the mobile communication system from which an overload can be predicted. This makes it possible to mitigate an overload even in a situation where an overload occurs in a network node that cannot directly notify the base station 110 of a message.

[0039] (Processing example 4) In this example, an operation will be described in process examples 1 to 3, in which the MME 120 requests suppression of connection requests and then cancels the suppression of connection requests. FIG. 9 shows an example of a flowchart illustrating the operation when the MME 120 requests cancellation of suppression of connection requests in this process example. In this example, an example will be described in which the MME 120 requests suppression of connection requests based on the occurrence of an overload state in the MME itself and another MME, and then cancels the suppression of connection requests. However, the operation of the MME 120 in this example can also be applied to a case in which the MME 120 requests suppression of connection requests based on the occurrence of an overload state in the MME itself (process example 1) or a case in which the MME 120 requests suppression of connection requests by estimating an overload state in another network node (process example 3). In either case, the MME 120 can request the base station 110 to cancel the suppression of connection requests based on the satisfaction of a predetermined condition for determining whether or not to cancel the suppression of connection requests. In this example, an example in which the suppression of connection requests is performed by access restriction will be described.

[0040] First, the MME 120 determines whether the overload state of the MME 120 has been resolved (S901). For example, the MME 120 monitors the load status of the MME 120 and determines whether a predetermined condition is satisfied. The method by which the MME 120 determines whether the load status of the MME 120 is overloaded, described above in Processing Example 1, can be applied as a method for the MME 120 to monitor the load status of the MME 120 and determine whether the predetermined condition is satisfied. In this case, the MME 120 may determine whether the load on the MME 120 is below a predetermined threshold. The predetermined threshold for determining whether to release the access restriction may be set lower than the threshold used when requesting the access restriction. For example, if the number of connection requests from the terminal 100 decreases as a result of the MME 120 requesting access restriction, the usage of the computational resources in the MME 120 may temporarily decrease. In this case, if the threshold for the usage rate of the computational resources used to determine whether to release the access restriction is the same as the threshold used to determine whether to request the access restriction, the request and release of the access restriction may be repeated frequently as the computational resources increase or decrease. To avoid this, the MME 120 may set a threshold for canceling access restriction after requesting the access restriction lower than the threshold for requesting the access restriction. This may prevent the MME 120 from repeatedly requesting and canceling access restriction in a short period of time. When the MME 120 determines that the overload state of the MME 120 has been resolved, the MME 120 executes the process of S902. On the other hand, when the overload state of the MME 120 has not been resolved, the MME 120 periodically repeats the determination of S901.

[0041] When the MME 120 determines that the overload of the MME 120 has been resolved (YES in S901), the MME 120 may check the load status of the other MMEs and determine whether a predetermined condition is met (S902). For example, the MME 120 may acquire the utilization rate of the computational resources of each of the other MMEs and determine whether the predetermined condition is met. The predetermined condition may be that the utilization rate of the computational resources has fallen below a predetermined threshold. Note that the predetermined threshold may be different from the threshold used to determine the elimination of the overload based on the utilization rate of the computational resources of the MME 120 in S901. For example, the MME 120 may set a first threshold used to determine the elimination of the overload of the MME 120 higher than a second threshold used to determine the load status of the other MMEs. That is, the MME 120 determines that the overload of the MME 120 has been resolved based on the utilization rate of the computational resources of the MME 120 having fallen below the first threshold, and further confirms that the access restriction may be lifted based on the utilization rate of the computational resources of the other MMEs having fallen below the second threshold. Alternatively, the first threshold and the second threshold may be the same. This allows the MME 120 to cancel the access restriction after confirming that the load on the other MME has decreased to the same level as the load on the MME itself. As described above in the processing example 2, the MME 120 may determine the load status of the other MME based on the number of connection requests that the other MME 120 has accepted or processed per unit time.

[0042] When the MME 120 determines that the load status of another MME 120 satisfies a predetermined condition (YES in S902), the MME 120 requests the base station 110 to lift the access restriction (S903). For example, the MME 120 may use the S1 interface to request each base station 110 to lift the access restriction. For example, the MME 120 may request the base station 110 to lift the access restriction by adapting the Overload Stop procedure defined in the S1 interface. As an example, the MME 120 may request the lifting of the access restriction by including a new information element indicating a request to lift the access restriction in an OVERLOAD STOP message used in the Overload Stop procedure. Note that the MME 120 may also request the lifting of the access restriction by adapting an existing information element in the OVERLOAD STOP message. Alternatively, the MME 120 may use a new procedure defined in the S1 interface to request the lifting of the access restriction.

[0043] The MME 120 may request that the access restriction be lifted based on the lapse of a predetermined period of time after requesting access restriction. For example, the MME 120 may start a predetermined timer based on the satisfaction of a predetermined condition after requesting access restriction, and may request that the access restriction be lifted when the timer expires. The predetermined condition may be, for example, that the utilization rate of the computational resources in the MME 120 falls below a predetermined threshold. In other words, after confirming that the overload caused by the access restriction has been alleviated, the number of terminals 120 making connection requests may decrease after a certain period of time has passed. Therefore, the MME 120 may request that the network load be stabilized after the lapse of the predetermined period of time, and may request that the access restriction be lifted in stages over multiple predetermined periods of time. For example, if the MME 120 imposes access restriction based on a restriction rate in a cell configured by the base station 110, the MME 120 may gradually relax the access restriction by gradually lowering the restriction rate. For example, after requesting access restriction, MME 120 may request that the access restriction be gradually released over a plurality of predetermined periods, and while the gradual release of the access restriction is being performed, MME 120 may determine whether or not an overload will occur in its own device or the network in parallel, and if an overload occurs, may notify base station 110 to re-execute access restriction. This makes it possible to control the request and release of access restriction even when requesting access restriction by inferring an overload in a device whose load state cannot be directly confirmed, such as a network node other than MME.

[0044] Note that when multiple MMEs 120 in a single mobile communication network independently request suppression of connection requests and request cancellation of the suppression, the base station 110 may not be able to determine whether to cancel the suppression of connection requests that are currently in progress. That is, when a request to cancel the suppression of connection requests is made because an overload has been resolved in a specific MME 120, the overload may not have been resolved in other MMEs. For this reason, when the base station 110 receives a request to cancel the suppression of connection requests that are currently in progress from a specific MME 120, it may check with the other MMEs 120. For example, when the base station 110 receives requests to cancel the suppression of connection requests from all MMEs 120, it may cancel the suppression of connection requests. Furthermore, when the base station 110 receives a request from a specific MME 120 to release the suppression of connection requests, it notifies the other MMEs 120 of a message confirming whether or not to release the suppression. If it receives a request within a predetermined period indicating that the suppression should not be released, it continues the suppression of connection requests. If it does not receive a request within the predetermined period indicating that the suppression should not be released, it may release the suppression of connection requests. Alternatively, it may determine one MME 120 from among multiple MMEs to request the suppression of connection requests and the request to release the suppression, and that MME 120 may make the request to the base station 110. For example, the MME 120 that has requested the suppression of connection requests may notify the other MMEs that it has made the request. Then, that MME 120 may determine whether the overload has been resolved and, based on the determination result, may request the release of the suppression of connection requests. This configuration makes it possible to prevent the suppression of connection requests requested by a specific MME 120 from being released due to a request from another MME 120.

[0045] (Variation) As described above, the present technology is applicable not only to mobile communication networks based on LTE but also to 5G mobile communication networks. In this case, the operation of the MME in each of the above processing examples may be executed by the AMF. Furthermore, messages between the base station 110 and the AMF may be executed using an NG interface. For example, a request to suppress connection requests may be notified to the base station 110 using an OVERLOAD START message in the NG interface. Furthermore, a request to release the suppression of connection requests may be notified to the base station 110 using an OVERLOAD STOP message in the NG interface. Note that, when a new message is configured in the NG interface from the AMF to the gNB to request suppression of connection requests or the release of the suppression, that message may be used.

[0046] (Processing flow) FIG. 10 shows an example of a processing flow when the MME 120 in this embodiment requests the base station 110 to impose and cancel access restriction, and the base station 110 notifies the terminal 100 of the access restriction. First, the MME 120 detects the occurrence of an overload based on its own load or the network load (S1001). For example, the MME 120 may determine an overload based on the utilization rate of its own computing resources, the number of connection requests received, the utilization rate of other MMEs' computing resources, the number of connection requests received, the number of predetermined messages sent to other network nodes, etc. When the MME 120 detects an overload, it requests the base station 110 to impose access restriction (S1002). Based on the request from the MME 120, the base station 110 notifies the cell that the MME 120 constitutes of the access restriction (S1003). For example, the base station 110 may notify the cell of the access restriction using System Information Block 2 (SIB2). When the terminal 100 receives the access restriction notified from the base station 110, it determines whether or not to transmit a connection request before transmitting the connection request (S1004). If the terminal 100 determines to transmit the connection request, it transmits the connection request. In this case, the base station 110 may forward the received connection request to the MME 120. The MME 120 may accept the forwarded connection request and perform operations such as registering the terminal 100 with the network. On the other hand, if the terminal 100 determines not to transmit the connection request, it may wait for a predetermined period of time without transmitting the connection request. After requesting access restriction, the MME 120 continuously determines whether the overload has been resolved. Then, when the MME 120 detects that the overload has been resolved (S1005), it requests the base station 110 to lift the access restriction (S1006). In response to the request, the base station 110 lifts the access restriction in the cell that the terminal 100 configures (S1007). In addition, base station 110 may transmit a notification to terminal 100 in the cell that it constitutes to cause access restriction to be performed from the time it receives a request for access restriction until it receives a request to lift the access restriction, and may not transmit a notification to cause access restriction to be performed based on the reception of a request to lift the access restriction.As an example, the base station 110 may notify that the access restriction has been lifted by changing the setting of a bit indicating the presence of access restriction in the SIB 2. In response to the lifting of the access restriction, the terminal 100 may not determine whether to permit transmission of a connection request when transmitting the connection request.

[0047] As described above, according to the present embodiment, the MME 120 requests the base station 110 to perform control to suppress transmission of connection requests to terminal devices based on the load of the MME 120 or the network. For example, the base station 110, based on the request from the MME 120, notifies the base station 110 to restrict connection requests from the terminal 100 in the cell configured by the MME 120. Based on the notification from the base station 110, the terminal 100 performs predetermined processing before transmitting the connection request to determine whether to transmit the connection request. With this configuration, when the load on a specific MME 120 or the network is high, the MME 120 can be the main determiner to suppress connection requests for each cell, thereby alleviating overload and preventing call losses and chain reactions of overload due to the transfer of processing to other MMEs. This makes it possible to prevent the occurrence and expansion of failures even in situations where the network is temporarily overloaded, such as when a large number of connection requests occur in a short period of time. This makes it possible to contribute to Goal 9 of the United Nations' Sustainable Development Goals (SDGs), "Build resilient infrastructure, promote sustainable industrialization and foster innovation."

[0048] The invention is not limited to the above-described embodiment, and various modifications and variations are possible within the scope of the invention. [Explanation of symbols]

[0049] 101: terminal, 102: terminal, 103: terminal, 104: terminal, 111: base station, 112: base station, 121: MME, 122: MME, 123: MME, 124: MME, 131: HSS, 132: SGW, 133: PGW, 134: IMS, 135: Internet

Claims

1. A control device operating as a Mobility Management Entity (MME) or an Access and Mobility Management Function (AMF) in a 3rd Generation Partnership Project (3GPP) cellular communication network, comprising: a receiving means for receiving a connection request to the cellular communication network from a terminal device via a base station device; determining means for making a first determination as to whether a value indicative of the load of the control device or a value indicative of the load of the cellular communication network exceeds a predetermined threshold; and a request means for requesting the base station device to perform control for suppressing transmission of the connection request to the terminal device based on a result of the first determination. A control device characterized by:

2. The value indicating the load of the control device is the utilization rate of the processor of the control device.

2. The control device according to claim 1.

3. The value indicating the load of the control device is the number of connection requests accepted by the accepting means within a predetermined period of time.

2. The control device according to claim 1.

4. The method further includes acquiring means for acquiring information capable of identifying a utilization rate of each processor of one or more other control devices in the cellular communication network, the first value indicating the load of the cellular communication network is a processor utilization rate of the control device; a second value indicating the load of the cellular communication network is a processor utilization rate of the other control device; The requesting means makes the request based on the first value exceeding a first threshold value and the second value in at least one of the other control devices exceeding a second threshold value.

2. The control device according to claim 1.

5. The method further comprises: acquiring means for acquiring a number of predetermined messages that one or more other control devices in the cellular communication network have sent to a predetermined device in the cellular communication network based on the connection request; The value indicating the load of the cellular communication network is the sum of the number of the predetermined messages sent by the control device and each of the other control devices to the predetermined device.

2. The control device according to claim 1.

6. When the control device is an MME, the requesting means makes the request using an S1 interface.

6. The control device according to claim 1, wherein the control device is a control unit for controlling a vehicle.

7. The requesting means makes the request using a Next Generation (NG) interface when the control device is an AMF.

6. The control device according to claim 1, wherein the control device is a control unit for controlling a vehicle.

8. The request means issues the request to all of the base station devices associated with the control device.

8. The control device according to claim 7.

9. The request means issues the request to a base station device that satisfies a predetermined geographical condition among the base station devices associated with the control device.

8. The control device according to claim 7.

10. the determining means performs a second determination as to whether or not a value indicating a load on the control device or a value indicating a load on the cellular communication network satisfies a predetermined condition during a period in which the control for suppressing the load is being performed; The request means requests the base station device to perform control for releasing the control for suppressing the communication based on a result of the second determination.

2. The control device according to claim 1.

11. The control for suppressing the transmission of the connection request from the terminal device is performed.

2. The control device according to claim 1.

12. The control for suppressing the transmission of radio waves from the base station device is to stop the transmission of radio waves.

2. The control device according to claim 1.

13. A base station apparatus in a 3rd Generation Partnership Project (3GPP) cellular communication network, comprising: a forwarding means for forwarding a connection request to the cellular communication network received from a terminal device to a control device operating as a Mobility Management Entity (MME) or an Access and Mobility Management Function (AMF) in the cellular communication network; a receiving means for receiving from the control device a request to perform control for suppressing transmission of the connection request to the terminal device, based on a value indicating a load of the control device or a value indicating a load of the cellular communication network exceeding a predetermined threshold; and a processing means for executing a process for suppressing the terminal device from transmitting the connection request based on the reception of the request. A base station device characterized by:

14. The process for suppressing is to restrict the terminal device from transmitting the connection request. The base station device according to claim 13 .

15. The suppression process is to stop the transmission of radio waves from the base station device. The base station device according to claim 13 .

16. The receiving means receives the request using an S1 interface when the control device is an MME, and receives the request using a Next Generation (NG) interface when the control device is an AMF. The base station device according to claim 13 .

17. 1. A control method performed by a control device operating as a Mobility Management Entity (MME) or an Access and Mobility Management Function (AMF) in a 3rd Generation Partnership Project (3GPP) cellular communication network, the method comprising: a receiving step of receiving a connection request to the cellular communication network from a terminal device via a base station device; a determining step of making a first determination whether a value indicative of the load of the control device or a value indicative of the load of the cellular communication network exceeds a predetermined threshold; and a request step of requesting the base station device to perform control to suppress transmission of the connection request to the terminal device based on a result of the first determination. A control method comprising:

18. 1. A control method performed by a base station device in a Third Generation Partnership Project (3GPP) cellular communication network, comprising: a forwarding step of forwarding a connection request to the cellular communication network received from a terminal device to a control device operating as a Mobility Management Entity (MME) or an Access and Mobility Management Function (AMF) in the cellular communication network; a receiving step of receiving from the control device a request to perform control for suppressing transmission of the connection request to the terminal device, based on a value indicating a load of the control device or a value indicating a load of the cellular communication network exceeding a predetermined threshold; a processing step of executing a process for suppressing the terminal device from transmitting the connection request based on the reception of the request. A control method comprising:

19. A computer included in a control device operating as a Mobility Management Entity (MME) or an Access and Mobility Management Function (AMF) in a cellular communication network of a Third Generation Partnership Project (3GPP), Accepting a connection request to the cellular communication network from a terminal device via a base station device; making a first determination whether a value indicative of a load on the control device or a value indicative of a load on the cellular communication network exceeds a predetermined threshold; making the base station device issue a request to perform control for suppressing transmission of the connection request to the terminal device based on a result of the first determination; Program for.

20. A computer provided in a base station device in a cellular communication network of the Third Generation Partnership Project (3GPP), Transferring a connection request to the cellular communication network received from the terminal device to a control device operating as a Mobility Management Entity (MME) or an Access and Mobility Management Function (AMF) in the cellular communication network; receiving, from the control device, a request to perform control for suppressing transmission of the connection request to the terminal device, based on a value indicating a load of the control device or a value indicating a load of the cellular communication network exceeding a predetermined threshold; and executing a process for suppressing the terminal device from transmitting the connection request based on the reception of the request. Program for.

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