Core network node, access network node, wireless terminal, and communication method

Abstract

The purpose of the present invention is to provide a core network node which is capable of smoothly executing a wireless terminal registration process, even if congestion occurs in a mobile network. A core access network node (10) according to the present disclosure comprises: a detection unit (11) that detects congestion occurring at the core network node (10); and a communication unit (12) that, if congestion has occurred in the core network node (10), transmits to a wireless terminal (30) a message which indicates that congestion has occurred and which includes identification information of another core network node. The message gives an instruction to select the other core network node.

Description

[Technical Field]

[0001] The present disclosure relates to a core network node, an access network node, a radio terminal, a communication method, and a program. [Background Art]

[0002] When using a mobile network, a radio terminal performs registration processing of the radio terminal with the mobile network. The mobile network registers the radio terminal after performing authentication of the radio terminal and the like. By being registered with the mobile network, the radio terminal becomes ready to use the mobile network.

[0003] Patent Literature 1 discloses processing when congestion occurs in a mobile network. For example, when an AMF (Access and Mobility Management Function) configuring a mobile network determines that congestion has occurred, the AMF transmits a wait time to UE (User Equipment) via (R)AN ((Radio) Access Network). The UE does not transmit a registration request message during the wait time period. [Related Art] [Patent Literature]

[0004] [Patent Literature 1] Japanese Unexamined Patent Publication No. 2021-180523 [Summary of Invention] [Problem to be Solved by Invention]

[0005] When the congestion control disclosed in Patent Literature 1 is performed, there is a problem that the UE cannot transmit a registration request message during the wait time period, and thus cannot receive services using the mobile network during that period.

[0006] One of the purposes of this disclosure is, in view of the above-mentioned problems, to provide a core network node, an access network node, a wireless terminal, a communication method, and a computer-readable medium that can smoothly perform the registration process of wireless terminals even when congestion occurs in the mobile network. [Means for solving the problem]

[0007] A first core network node according to a first aspect of the present disclosure is a first core network node comprising: a detection unit for detecting congestion occurring in the first core network node; and a communication unit for transmitting a message to a wireless terminal indicating that congestion has occurred, which includes identification information of a second core network node, when congestion occurs in the first core network node, wherein the message instructs the selection of the second core network node.

[0008] An access network node according to a second aspect of the present disclosure includes a communication unit that receives a message from a wireless terminal indicating that congestion has occurred in a first core network node and instructing the selection of a second core network node different from the first core network node, and a selection unit that the message includes identification information of the second core network node and selects the second core network node identified by the identification information as the destination for a registration request message included in the message, wherein the communication unit transmits the registration request message to the second core network node.

[0009] A wireless terminal according to a third aspect of the present disclosure includes a receiving unit that receives a first message from a first core network node where congestion has occurred, indicating that congestion has occurred at the first core network node and instructing the selection of a second core network node different from the first core network node; and a transmitting unit that transmits a second message to the access network node, instructing the access network node to select the second core network node, wherein the first message includes identification information of the second core network node, and the second message includes identification information of the second core network node.

[0010] A communication method performed in a first core network node according to a fourth aspect of the present disclosure detects congestion occurring in the first core network node, and if congestion occurs in the first core network node, transmits a message to a wireless terminal that includes identification information of a second core network node and indicates that congestion has occurred, and the message instructs the selection of the second core network node.

[0011] A communication method performed in an access network node according to a fifth aspect of this disclosure receives a message from a wireless terminal indicating that congestion has occurred in a first core network node and instructing the selection of a second core network node different from the first core network node, the message including identification information of the second core network node, and based on the identification information, selects the second core network node identified by the identification information as the destination for a registration request message included in the message. The registration request message is sent to the second core network node.

[0012] A communication method performed in a wireless terminal according to a sixth aspect of the present disclosure includes receiving a first message from a first core network node where congestion has occurred, indicating that congestion has occurred at the first core network node and instructing the selection of a second core network node different from the first core network node, wherein the first message includes identification information of the second core network node, notifying an access network node that congestion has occurred at the first core network node and transmitting a second message to the access network node instructing the selection of the second core network node, wherein the second message includes identification information of the second core network node.

[0013] A program according to a seventh aspect of this disclosure detects congestion occurring at the first core network node and, if congestion occurs at the first core network node, causes a computer which is a core network node to send a message to a wireless terminal indicating that congestion has occurred, which includes identification information of the second core network node and instructs the selection of a second core network node. [Effects of the Invention]

[0014] This disclosure provides a core network node, an access network node, a wireless terminal, a communication method, and a program that can smoothly execute the registration process of wireless terminals even when congestion occurs in the mobile network. [Brief explanation of the drawing]

[0015] [Figure 1] This is a diagram showing the configuration of the communication system according to Embodiment 1. [Figure 2] This diagram shows the flow of communication processing in the core network node according to Embodiment 1. [Figure 3] This diagram shows the flow of communication processing in an access network node according to Embodiment 1. [Figure 4]It is a diagram showing the flow of communication processing in the wireless terminal according to the first embodiment. [Figure 5] It is a configuration diagram of the communication system according to the second embodiment. [Figure 6] It is a diagram showing the flow of Registration processing according to the second embodiment. [Figure 7] It is a diagram showing the flow of Registration processing according to the second embodiment. [Figure 8] It is a diagram showing the flow of Registration processing according to the third embodiment. [Figure 9] It is a diagram showing the flow of Registration processing according to the third embodiment. [Figure 10] It is a configuration diagram of the core network node and the AMF node according to each embodiment. [Figure 11] It is a configuration diagram of the access network node and gNB according to each embodiment. [Figure 12] It is a configuration diagram of the wireless terminal and UE according to each embodiment. DETAILED DESCRIPTION OF EMBODIMENTS

[0016] (First Embodiment) Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. A configuration example of the communication system according to the first embodiment will be described using FIG. 1. The communication system in FIG. 1 includes a core network node 10, an access network node 20, and a wireless terminal 30.

[0017] First, an example configuration of the core network node 10 will be described. The core network node 10 may be a computer device that operates by having a processor execute a program stored in memory. The core network node 10 may be a node device defined, for example, in 3GPP (3rd Generation Partnership Project). Specifically, the core network node 10 may be an MME (Mobility Management Entity) or an AMF (Access and Mobility Function) node. An AMF node may be referred to as an AMF entity.

[0018] The core network node 10 includes a detection unit 11 and a communication unit 12. The detection unit 11 and the communication unit 12 may be software or modules whose processing is performed by a processor executing a program stored in memory. The detection unit 11 and the communication unit 12 may also be hardware such as a circuit or chip.

[0019] The detection unit 11 detects congestion occurring at the core network node 10. For example, the detection unit 11 may detect congestion when the amount of data received at the core network node 10, or the number of messages, exceeds a threshold. Alternatively, the detection unit 11 may detect congestion when it detects that the number of messages, etc., is lower than normal. Alternatively, the detection unit 11 may detect congestion when the number of wireless terminals managed by the core network node 10 exceeds a threshold. Alternatively, the detection unit 11 may detect congestion when the processor or memory usage exceeds a threshold. The thresholds for comparison with the number of messages, etc., the threshold for comparison with the number of wireless terminals, and the threshold for comparison with the processor, etc., are all different. The number of wireless terminals managed by the core network node 10 may be rephrased as the number of wireless terminals registered with the core network node 10.

[0020] The detection unit 11 may detect that congestion has occurred in the core network node 10 when it is notified by a management system or the like that which manages the communication system that congestion has occurred in the core network node 10. The detection unit 11 may periodically or at arbitrary times transmit information such as the amount of data to be sent and received, the number of messages to be sent and received, the number of wireless terminals to be managed, and the usage rate of the processor or memory to the management system.

[0021] When congestion occurs at the core network node 10, the communication unit 12 sends a message to the wireless terminal 30 indicating that congestion has occurred, which includes the identification information of at least one other core network node. The message instructs the wireless terminal to select at least one other core network node corresponding to the identification information. The occurrence of congestion may be indicated, for example, by including information in the message to notify the wireless terminal 30 that congestion has occurred. The instruction to select another core network node may be indicated, for example, by including information instructing the wireless terminal to select another core network node in the message. Alternatively, for example, the message may include information indicating that congestion has occurred and information instructing the selection of another core network node. The communication unit 12 sends the message to the wireless terminal 30 via the access network node 20.

[0022] Information for notifying the wireless terminal 30 that congestion has occurred may include, for example, identification information of the core network node 10 where congestion occurred. Furthermore, information for notifying the wireless terminal 30 that congestion has occurred may include information indicating the congestion level, which shows the degree of congestion. The congestion level may be determined, for example, according to the difference between the number of messages and a threshold. Alternatively, the congestion level may be calculated based on, for example, the time since congestion started or an estimated value of the congestion period. The core network node identification information may be information assigned to each core network node to uniquely identify the core network node. Or, the core network node identification information may be address information such as an IP address or MAC address.

[0023] Next, an example configuration of the access network node 20 will be described. The access network node 20 may be a computer device that operates by having a processor execute a program stored in memory. The access network node 20 may be a node device that wireless terminals 30 access when using the mobile network. The access network node 20 may be, for example, a base station that communicates wirelessly with wireless terminals 30. The base station may be, for example, a device defined in 3GPP, and specifically may be an eNB (evolved Node B) or a gNB (gNode B). Alternatively, the access network node 20 may be an AP (Access Point) that performs wireless LAN (Local Area Network) communication.

[0024] The access network node 20 has a communication unit 21 and a selection unit 22. The communication unit 21 and the selection unit 22 may be software or modules whose processing is performed by the processor executing a program stored in memory. Alternatively, the communication unit 21 and the selection unit 22 may be hardware such as a circuit or chip.

[0025] The communication unit 21 receives a message from the wireless terminal 30 indicating that congestion has occurred at the core network node 10 and instructing the selection of a core network node different from the core network node 10. The message includes the identifier of the core network node different from the core network node 10. The congestion at the core network node 10 may also be indicated by including information in the message to notify the access network node 20 that congestion has occurred at the core network node 10. The instruction to select a core network node different from the core network node 10 may also be indicated, for example, by including information in the message instructing the access network node to select a core network node different from the core network node 10. Alternatively, for example, the message may include information indicating that congestion has occurred and further instructing the selection of a core network node different from the core network node 10. The message received from the wireless terminal 30 includes a registration request message.

[0026] The information used to notify the access network node 20 that congestion has occurred at the core network node 10 may be the same information that the core network node 10 sends to the wireless terminal 30 to notify the wireless terminal 30 that congestion has occurred. Alternatively, the information used to notify the access network node 20 that congestion has occurred at the core network node 10 may be different from the information used to notify the wireless terminal 30 that congestion has occurred. Specifically, this different information may be in a different format.

[0027] The registration request message is used when the wireless terminal 30 uses the mobile network to request registration of the wireless terminal 30 from the core network node.

[0028] The selection unit 22 selects another core network node identified by the received identification information as the destination for the registration request message. Selecting another core network node can be rephrased as deciding to send the other core network node as the destination for the registration request message. Alternatively, selecting another core network node can be rephrased as identifying another core network node from among multiple core network nodes that is identified by the received identification information.

[0029] If the selection unit 22 does not receive information indicating that congestion has occurred at the core network node 10, it may select a core network different from the other core network nodes identified by the received identification information as the destination for the registration request message. In other words, if the selection unit 22 receives information indicating that congestion has occurred at the core network node 10, it will not select a core network different from the other core network nodes identified by the received identification information as the destination for the registration request message.

[0030] The communication unit 21 transmits the registration request message received from the wireless terminal 30 to the other core network nodes identified by the selection unit 22.

[0031] Next, an example configuration of the wireless terminal 30 will be described. The wireless terminal 30 may be a computer device that operates by having a processor execute a program stored in memory. The wireless terminal 30 is a terminal that can communicate wirelessly with the access network node 20 according to a predetermined communication standard. The wireless terminal 30 may be, for example, a mobile phone terminal, a smartphone terminal, an IoT (Internet of Things) terminal, etc. The communication standard may be, for example, a wireless communication standard such as the so-called 4G (4th Generation) or 5G (5th Generation) defined by 3GPP, or it may be a communication standard for wireless LAN communication.

[0032] The wireless terminal 30 has a receiving unit 31 and a transmitting unit 32. The receiving unit 31 and the transmitting unit 32 may be software or modules whose processing is performed by a processor executing a program stored in memory. Alternatively, the receiving unit 31 and the transmitting unit 32 may be hardware such as a circuit or chip.

[0033] The receiving unit 31 receives a first message from the core network node 10 where congestion has occurred, indicating that congestion has occurred at the core network node 10 and instructing the receiving unit 31 to select another core network node different from the core network node 10. The first message further includes identification information of the other core network node different from the core network node 10. The receiving unit 31 receives the message sent from the core network node 10 via the access network node 20.

[0034] The transmitting unit 32 notifies the access network node 20 that congestion has occurred at the core network node 10 and sends a second message to the access network node 20 instructing it to select another core network node. The second message includes identification information of the other core network node. The second message further includes a registration request message.

[0035] The wireless terminal 30 becomes able to use the mobile network upon receiving a response message to the registration request message.

[0036] Next, the communication processing flow in the core network node 10 according to Embodiment 1 will be explained using Figure 2. First, the detection unit 11 detects congestion occurring in the core network node 10 (S11). Next, when congestion occurs in the core network node 10, the communication unit 12 sends a message to the wireless terminal 20 indicating that congestion has occurred, which includes identification information of another core network node different from the core network node 10 (S12). This message instructs the user to select another core network node.

[0037] Next, the communication processing flow in the access network node 20 according to Embodiment 1 will be explained using Figure 3. First, the communication unit 21 receives a message from the wireless terminal 30 indicating that congestion has occurred in the core network node 10 and instructing it to select another core network node different from the core network node 10 (S21). The message further includes identification information of the other core network node different from the core network node 10 and a registration request message. Next, the selection unit 22 selects the other core network node identified by the identification information as the destination for sending the registration request message based on the identification information (S22). Next, the communication unit 21 sends the registration request message to the other core network node selected by the selection unit 22 (S23).

[0038] Next, the communication processing flow in the wireless terminal 30 according to Embodiment 1 will be explained using Figure 4. First, the receiving unit 31 receives a first message from the core network node 10 where congestion has occurred, indicating that congestion has occurred at the core network node 10 and instructing the receiving unit 31 to select another core network node different from the core network node 10 (S31). The message further includes identification information of the other core network node different from the core network node 10. Next, the transmitting unit 32 notifies the access network node 20 that congestion has occurred at the core network node 10 and sends a second message to the access network node 20 instructing it to select another core network node (S32). The second message further includes identification information of the other core network node and a registration request message.

[0039] As explained above, when congestion occurs at core network node 10, it transmits identification information of another core network node to wireless terminal 30. Furthermore, wireless terminal 30 transmits to access network node 20 the fact that congestion has occurred at core network node 10 and the identification information of another core network node that will take over from core network node 10. As a result, access network node 20 can transmit the registration request message received from wireless terminal 30 to the other core network node on behalf of core network node 10. Consequently, the other core network node can manage wireless terminal 30 on behalf of core network node 10, and wireless terminal 30 can receive services using the mobile network.

[0040] (Embodiment 2) Next, an example of the configuration of the communication system according to Embodiment 2 will be described using Figure 5. The communication system in Figure 5 shows a 5GS (5G System) as defined by 3GPP. The 5GS in Figure 5 has a 5GC (5G Core) 40, a RAN (Radio Access Network) 50, and a UE (User Equipment) 60. Furthermore, the 5GC 40 has an AMF (Access and Mobility Management Function) node 41 (hereinafter referred to as AMF41), an AMF node 42 (hereinafter referred to as AMF42), and an NRF (Network Repository Function) node 43 (hereinafter referred to as NRF43). The RAN 50 has a gNB 51. The AMF 41 and AMF 42 correspond to the core network node 10 and include the same components as the core network node 10 in Figure 1. The gNB 51 corresponds to the access network node 20 and includes the same components as the access network node 20 in Figure 1. The UE 60 corresponds to the wireless terminal 30 and includes the same components as the wireless terminal 30 in Figure 1. A node may be rephrased as an entity or device, etc.

[0041] Figure 5 shows that RAN50 includes gNB51 which communicates wirelessly with UE60, but RAN50 may also include node devices which communicate with UE60 in a manner different from wireless communication, such as fixed communication. In this case, RAN50 may be referred to as AN (Access Network) or (R)AN.

[0042] Next, the flow of the Registration process according to Embodiment 2 will be explained using Figure 6. The Registration process in Figure 6 refers to the sequence of the Registration procedure described in 3GPP TS23.502 V17.4.0, and extracts and explains the processes necessary for explaining Embodiment 2. Registration is the process performed so that UE60 can use the services provided in 5GS. In other words, once the Registration process is completed and UE60 is registered with the node devices included in AMF41 or AMF42 and 5GC40, UE60 can use the services provided in 5GS.

[0043] First, let's assume that congestion occurs in AMF41 (S41). For example, the detection unit 11 that constitutes AMF41 may detect the congestion that has occurred in AMF41. Alternatively, a monitoring device that monitors 5GC40 may notify AMF41 that congestion has occurred in AMF41, and the detection unit 11 may then detect the congestion that has occurred in AMF41.

[0044] Next, UE60 sends an AN (Access Network) message containing a Registration Request message to gNB51 (S42). For example, UE60 may send a Registration Request message to gNB51 after UE60 has been started. Furthermore, UE60 may send Registration Request messages to gNB51 periodically or regularly. Alternatively, UE60 may send a Registration Request message to gNB51 when it enters a new TA (Tracking Area). Entering a new TA can be rephrased as moving to a new TA. The Registration Request message includes SUCI (Subscription Concealed Identifier) ​​or 5G-GUTI (5G Globally Unique Temporary Identifier) ​​as identification information to identify UE60.

[0045] The AN message further includes AN parameters. These AN parameters may include, for example, 5G-S-TMSI (5G S Temporary Mobile Subscription Identifier) ​​or GUAMI (Globally Unique AMF Identifier). 5G-S-TMSI is identification information for identifying the UE60. 5G-S-TMSI includes the AMF Set ID, AMF Pointer, and 5G-TMSI. The AMF Set ID is identification information for identifying an AMF set containing one or more AMFs, and the AMF Pointer is identification information for identifying each AMF included in the AMF set. 5G-TMSI is identification information for the UE60 managed in the AMF.

[0046] GUAMI is identification information used to identify AMF. GUAMI includes MCC (Mobile Country Number), MNC (Mobile Network Code), AMF Region ID, AMF Set ID, and AMF Pointer. MCC represents the country or region, and MNC represents the operator. The AMF Region ID represents the region where AMF is located.

[0047] Next, gNB51 selects the AMF to which the Registration Request message will be sent (S43). If the AN parameter includes 5G-S-TMSI or GUAMI, gNB51 may select the AMF identified by 5G-S-TMSI or GUAMI. Alternatively, even if the AN parameter includes 5G-S-TMSI or GUAMI, gNB51 may select an AMF different from the AMF identified by 5G-S-TMSI or GUAMI.

[0048] For example, gNB51 may select a different AMF than the one identified by 5G-S-TMSI or GUAMI if it is unable to use the AMF identified by 5G-S-TMSI or GUAMI included in the AN parameters. Specifically, if gNB51 detects that the AMF identified by 5G-S-TMSI or GUAMI is malfunctioning, it may select a different AMF than the one identified by 5G-S-TMSI or GUAMI. Alternatively, if gNB51 has been notified in advance that the AMF identified by 5G-S-TMSI or GUAMI is unavailable, it may select a different AMF than the one identified by 5G-S-TMSI or GUAMI. Alternatively, if the load on the AMF identified by 5G-S-TMSI or GUAMI is greater than a predetermined value, gNB51 may choose not to select the AMF identified by 5G-S-TMSI or GUAMI.

[0049] gNB51 may select an AMF based on the AMF Region ID and AMF Set ID. For example, gNB51 may select an AMF to which the Registration Request message will be sent from among multiple AMFs included in the AMF Set ID. Alternatively, gNB51 may select an AMF according to the policies of the operator managing 5GS, or it may select an AMF considering the load status of the AMF. In step S43, let's assume that gNB51 has selected AMF41.

[0050] Next, gNB51 sends the Registration Request message received from UE60 in step S42 to AMF41 (S44). Next, AMF41 sends a Registration Reject message to UE60 via gNB51 to reject UE60's registration on the grounds that congestion has occurred in AMF41 (S45). The Registration Reject message includes information to notify UE60 that congestion has occurred in AMF41, a GUAMI representing a different AMF, for example, AMF42, and information instructing the selection of AMF42. The information to notify UE60 that congestion has occurred in AMF41 may be, for example, a cause value set to "congestion". The cause value is a parameter that indicates the reason for rejecting UE60's registration. The information instructing the selection of AMF42 may be, for example, an information element instructing the selection of the AMF identified by the GUAMI included in the Registration Reject message. Furthermore, the Registration Reject message may also be a cause value that indicates, for example, "congestion" and instructs the selection of an AMF identified by GUAMI included in the Registration Reject message.

[0051] AMF41 may include a GUAMI representing AMF42, which is not experiencing congestion, in its Registration Reject message. Alternatively, if multiple AMFs are not experiencing congestion, AMF41 may select any of these AMFs, or it may select an AMF according to a predetermined policy. For example, AMF41 may select an operational AMF that is not experiencing congestion and has the same AMF Region ID or AMF Set ID as AMF41. Or, AMF41 may include the GUAMIs of multiple AMFs that are not experiencing congestion in its Registration Reject message.

[0052] AMF41 may change the AMF it selects depending on the degree of congestion. For example, if the degree of congestion is greater than a predetermined standard and the impact of the congestion is significant, AMF41 may select an AMF managed by another telecommunications carrier, i.e., an AMF not included in 5GC40. If the degree of congestion is below a predetermined standard and the impact of the congestion is limited, AMF41 may select an AMF within 5GC40. The criteria for determining the degree of congestion may be determined using, for example, the AMF downtime, the number of affected UEs, etc. Alternatively, the criteria for determining the degree of congestion may be, for example, the number of packet losses.

[0053] Furthermore, AMF41 may send a Registration Reject message in step S45 if the received Registration Request message indicates that it is an Emergency Registration. In other words, if the Registration Request message does not indicate that it is an Emergency Registration, AMF41 does not need to include a GUAMI representing a different AMF from AMF41 in the Registration Reject message. In other words, AMF41 may allow only UEs sending emergency calls to register with other AMFs that are not experiencing congestion. This allows UEs sending emergency calls to complete the registration process with other AMFs that are not experiencing congestion. An Emergency Registration may be, for example, a message containing information indicating that an Emergency service is being requested.

[0054] The AMF42 selected by AMF41, which is not experiencing congestion, may be a new AMF that is virtually constructed when congestion occurs in the AMF. For example, if the MANO (Management and Orchestration) that constitutes the NFV (Network Functions Virtualization) architecture detects that congestion has occurred in AMF41, the MANO may perform AMF virtualization by starting a VNF (Virtual Network Function) that operates as an AMF.

[0055] Next, upon receiving a Registration Reject message, UE60 sends an AN message containing a Registration Request message to gNB51 to execute the Registration process again (S46). UE60 sets GUAMI, which is included in the Registration Reject message received in step S45, as an AN parameter. Furthermore, UE60 sets information in the AN parameter to notify gNB51 that congestion has occurred in AMF41. For example, UE60 may include flag information in gNB51 indicating that congestion has occurred in AMF41. Alternatively, UE60 may not set identification information to identify AMF41 as an AN parameter, but instead set information indicating that congestion has occurred in any AMF. Alternatively, UE60 may set information in the AN parameter indicating that it is a Registration Request message sent again after receiving a Registration Reject message. Furthermore, UE60 sets information instructing the selection of AMF42 as an AN parameter. The information instructing the selection of AMF42 may be, for example, an information element instructing the selection of an AMF identified by GUAMI, which is set as an AN parameter. Alternatively, UE60 may set information as an AN parameter, for example, notifying gNB51 that congestion has occurred in AMF41 and instructing the selection of AMF42.

[0056] Next, gNB51 selects the AMF to which the Registration Request message will be sent (S47). The AN parameters may contain information instructing the selection of GUAMI, the AMF associated with GUAMI, and information to notify gNB51 that congestion has occurred at AMF41. In this case, gNB51 identifies the AMF identified in GUAMI as the AMF to which the Registration Request message will be sent. In other words, if the AN parameters contain information instructing the selection of GUAMI, the AMF associated with GUAMI, and information to notify gNB51 that congestion has occurred at AMF41, gNB51 identifies the AMF identified in GUAMI without selecting any other AMF. To put it another way, if the AN parameters do not contain information to notify gNB51 that congestion has occurred at AMF41, gNB51 may not identify the AMF identified in GUAMI. For example, if the AN parameters of gNB51 do not contain information instructing the selection of an AMF associated with GUAMI, gNB51 may not identify the AMF identified in GUAMI. On the other hand, if the AN parameters of gNB51 contain information instructing the selection of an AMF associated with GUAMI and information to notify gNB51 that congestion has occurred in AMF41, gNB51 will forcibly identify the AMF identified in GUAMI as the destination for the Registration Request message. Forcibly identifying an AMF means that gNB51 will identify the AMF identified in GUAMI without determining whether to select a different AMF from the one identified in GUAMI.

[0057] Next, gNB51 sends a Registration Request message to AMF42, which is represented by GUAMI set in the AN parameter (S48).

[0058] Next, AMF42 performs authentication processing for UE60, and if the registration process for UE60 is successfully completed, it sends a Registration Accept message to UE60 (S49). Furthermore, upon receiving the Registration Accept message, UE60 sends a Registration Complete message to AMF42 (S50). This completes the registration process for UE60.

[0059] As described above, in the 5GS according to Embodiment 2, if the Registration process fails to be performed correctly due to congestion in the AMF41, the UE60 sends another Registration Request message. At this time, the UE60 sends a message to the gNB51 containing information to notify the gNB51 that congestion has occurred in the AMF41, and information to instruct the gNB51 to select the GUAMI notified by the AMF41 and the AMF associated with the GUAMI. As a result, the gNB51 can send the Registration Request message received from the UE60 to the AMF42, which is not experiencing congestion. Consequently, the Registration process for the UE60 can be completed successfully.

[0060] Furthermore, while Figure 6 describes the process by which AMF41 selects AMF42, as shown in Figure 7, if congestion occurs in AMF41, NRF43 may select AMF42. Specifically, if AMF41 detects congestion in step S41, it sends a message to NRF43 notifying it that congestion has occurred (S51). Next, NRF43 sends a message to AMF41 notifying it of GUAMI, which represents AMF42 as an AMF that is not experiencing congestion (S52). Steps S42 to S50 in Figure 7 are the same as in Figure 6, so a detailed explanation is omitted. In step S44, when AMF41 receives a Registration Request message, it sends a Registration Reject message containing GUAMI notified by NRF43 to UE60.

[0061] Furthermore, as shown in Figure 7, AMF41 may notify NRF43 of congestion before receiving the Registration Request message, or it may notify NRF43 of congestion after receiving the Registration Request message. In other words, AMF41 may execute the processes of steps S51 and S52 between steps S44 and S45.

[0062] (Embodiment 3) Next, the flow of the Registration process according to Embodiment 3 will be explained using Figure 8. The Registration process in Figure 8 refers to the Registration procedure and Network-initiated Deregistration sequence described in 3GPP TS23.502 V17.4.0, and extracts and explains the processes necessary for explaining Embodiment 3. In addition, Figure 8 assumes that UE60 is in a Registered state, where the Registration process with AMF41 has been completed.

[0063] First, let's assume that congestion occurs in AMF41 (S61). For example, the detection unit 11 that constitutes AMF41 may detect the congestion that has occurred in AMF41. Alternatively, the detection unit 11 may detect the congestion that has occurred in AMF41 when a monitoring device or the like that monitors 5GC40 notifies it that congestion has occurred in AMF41.

[0064] Next, AMF41 sends a Deregistration Request message to UE60 via gNB51 (S62). The Deregistration Request message is used to request the unregistration of UE60 in AMF41. The Deregistration Request message includes information to notify UE60 that congestion has occurred in AMF41, a GUAMI representing a different AMF from AMF41, for example, AMF42, and information instructing the selection of AMF42. Alternatively, AMF41 may include the GUAMIs of multiple AMFs that are not experiencing congestion in the Deregistration Request message.

[0065] Furthermore, if UE60 is in the CM (Connection Management)-IDLE state, AMF41 may send a Deregistration Request message to UE60 after performing paging to UE60. The CM-IDLE state is a state in which a NAS (Non Access Stratum) signaling connection has not been established between UE60 and AMF41.

[0066] AMF41 may send a Deregistration Request message to all UEs registered with AMF41 or to all UEs managed by AMF41. Alternatively, AMF41 may send a Deregistration Request message to some of the UEs included in all UEs registered with AMF41.

[0067] For example, AMF41 may send a Deregistration Request message only to UEs that are designated as priority terminals or that are designated to use priority services. This allows UEs designated as priority terminals or those designated to use priority services to receive priority services by performing the registration process with an AMF that is not experiencing congestion.

[0068] Alternatively, AMF41 may send a Deregistration Request message only to UEs that are not designated as priority terminals or UEs that have not indicated they will be using priority services. AMF41 may also resolve congestion that has occurred in AMF41 by deregistering UEs other than those that are not designated as priority terminals. As a result, UEs that are designated as priority terminals or UEs that have indicated they will be using priority services and are registered with AMF41 will be able to receive priority services.

[0069] Next, upon receiving the Deregistration Request message, UE60 sends a Deregistration Accept message to AMF41 via gNB51 (S63).

[0070] The processing in steps S64 to S68 is the same as in steps S46 to S50 in Figure 6, so a detailed explanation is omitted. In step S46, UE60 sets GUAMI included in the Registration Reject message as an AN parameter, while in step S64, UE60 sets GUAMI included in the Deregistration Request message as an AN parameter.

[0071] As described above, in the 5GS according to Embodiment 3, if congestion occurs in AMF41 after the Registration process is completed between UE60 and AMF41, the Registration for UE60 is canceled. Subsequently, UE60 sends a Registration Request message to perform the Registration process again. At this time, UE60 sends a message to gNB51 that notifies gNB51 that congestion has occurred in AMF41, the GUAMI notified by AMF41, and information instructing the selection of the AMF identified by the GUAMI. As a result, gNB51 can send the Registration Request message received from UE60 to AMF42, which is not experiencing congestion. Consequently, UE60 can successfully complete the Registration process with AMF42, which is not experiencing congestion.

[0072] Furthermore, while Figure 8 describes the process by which AMF41 selects AMF42, as shown in Figure 9, if congestion occurs in AMF41, NRF43 may select AMF42. Specifically, if AMF41 detects congestion in step S61, it sends a message to NRF43 notifying it that congestion has occurred (S71). Next, NRF43 sends a message to AMF41 notifying it of GUAMI, which represents AMF42 as an AMF that is not experiencing congestion (S72). Steps S62 to S68 in Figure 9 are the same as in Figure 8, so a detailed explanation is omitted. In step S72, when AMF41 receives a message from NRF43, it sends a Deregistration Request message containing GUAMI notified by NRF43 to UE60.

[0073] Figure 10 is a block diagram showing an example configuration of an access network node 20 and gNB51 (hereinafter referred to as the access network node 20, etc.). Referring to Figure 10, the access network node 20, etc. includes an RF transceiver 1001, a network interface 1003, a processor 1004, and a memory 1005. The RF transceiver 1001 performs analog RF signal processing to communicate with UEs. The RF transceiver 1001 may include multiple transceivers. The RF transceiver 1001 is coupled with an antenna 1002 and a processor 1004. The RF transceiver 1001 receives modulated symbol data (or OFDM symbol data) from the processor 1004, generates a transmit RF signal, and supplies the transmit RF signal to the antenna 1002. The RF transceiver 1001 also generates a baseband receive signal based on the received RF signal received by the antenna 1002 and supplies this to the processor 1004.

[0074] The network interface 1003 is used to communicate with network nodes (e.g., other core network nodes). The network interface 1003 may include, for example, a network interface card (NIC) compliant with the IEEE 802.3 series.

[0075] The processor 1004 performs data plane processing and control plane processing, including digital baseband signal processing for wireless communication.

[0076] The processor 1004 may include multiple processors. For example, the processor 1004 may include a modem processor (e.g., DSP) that performs digital baseband signal processing and a protocol stack processor (e.g., CPU or MPU) that performs control plane processing.

[0077] Memory 1005 is composed of a combination of volatile and non-volatile memory. Memory 1005 may include multiple physically independent memory devices. Volatile memory is, for example, Static Random Access Memory (SRAM) or Dynamic RAM (DRAM), or a combination thereof. Non-volatile memory is Mask Read Only Memory (MROM), Electrically Erasable Programmable ROM (EEPROM), flash memory, or hard disk drive, or any combination thereof. Memory 1005 may include storage located away from the processor 1004. In this case, the processor 1004 may access memory 1005 via the network interface 1003 or an I / O interface not shown.

[0078] Memory 1005 may store a software module (computer program) containing instruction sets and data for processing by the access network node 20, etc., as described in the above-described embodiments. In some implementations, the processor 1004 may be configured to read the software module from memory 1005 and execute it to perform the processing of the access network node 20, etc., as described in the above-described embodiments.

[0079] Figure 11 is a block diagram showing an example configuration of the wireless terminal 30 and UE60 (hereinafter referred to as wireless terminal 30, etc.). The Radio Frequency (RF) transceiver 1101 performs analog RF signal processing to communicate with the access network node 20 or gNB51. The analog RF signal processing performed by the RF transceiver 1101 includes frequency upconversion, frequency downconversion, and amplification. The RF transceiver 1101 is coupled with the antenna 1102 and the baseband processor 1103. Specifically, the RF transceiver 1101 receives modulation symbol data (or OFDM symbol data) from the baseband processor 1103, generates a transmit RF signal, and supplies the transmit RF signal to the antenna 1102. The RF transceiver 1101 also generates a baseband receive signal based on the received RF signal received by the antenna 1102 and supplies this to the baseband processor 1103.

[0080] The baseband processor 1103 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. Digital baseband signal processing includes (a) data compression / decompression, (b) data segmentation / concatenation, (c) generation / decomposition of transmission format (transmission frame), (d) transmission path coding / decoding, (e) modulation (symbol mapping) / demodulation, and (f) generation of OFDM symbol data (baseband OFDM signal) by Inverse Fast Fourier Transform (IFFT). Meanwhile, control plane processing includes communication management at Layer 1, Layer 2, and Layer 3.

[0081] The baseband processor 1103 may include a modem processor (e.g., Digital Signal Processor (DSP)) that performs digital baseband signal processing and a protocol stack processor (e.g., Central Processing Unit (CPU) or Micro Processing Unit (MPU)) that performs control plane processing. In this case, the protocol stack processor that performs control plane processing may be shared with the application processor 1104 described later.

[0082] The application processor 1104 is also called a CPU, MPU, microprocessor, or processor core. The application processor 1104 may include multiple processors (multiple processor cores). The application processor 1104 implements various functions of the wireless terminal 30, etc., by executing system software programs (Operating System (OS)) and various application programs (e.g., calling applications, web browsers, mail clients, camera operation applications, music playback applications) read from memory 1106 or memory not shown.

[0083] In some implementations, the baseband processor 1103 and the application processor 1104 may be integrated on a single chip, as shown by the dashed line (1105) in Figure 11. In other words, the baseband processor 1103 and the application processor 1104 may be implemented as a single System on Chip (SoC) device 1105. An SoC device is sometimes called a System Large Scale Integration (LSI) or chipset.

[0084] Memory 1106 is volatile memory, non-volatile memory, or a combination thereof. Memory 1106 may include multiple physically independent memory devices. Volatile memory is, for example, Static Random Access Memory (SRAM) or Dynamic RAM (DRAM), or a combination thereof. Non-volatile memory is Mask Read Only Memory (MROM), Electrically Erasable Programmable ROM (EEPROM), flash memory, or hard disk drive, or any combination thereof. For example, memory 1106 may include an external memory device accessible from the baseband processor 1103, the application processor 1104, and the SoC 1105. Memory 1106 may also include an internal memory device integrated within the baseband processor 1103, the application processor 1104, or the SoC 1105. Furthermore, memory 1106 may include memory within a Universal Integrated Circuit Card (UICC).

[0085] The memory 1106 may store a software module (computer program) containing a set of instructions and data for processing by the wireless terminal 30, etc., as described in the above-described embodiments. In some implementations, the baseband processor 1103 or application processor 1104 may be configured to read the software module from the memory 1106 and execute it to perform the processing of the wireless terminal 30, etc., as described in the above-described embodiments.

[0086] Figure 12 is a block diagram showing an example configuration of the core network node 10, AMF41, and AMF42 (hereinafter referred to as the core network node 10, etc.) described in the above-described embodiment. Referring to Figure 12, the core network node 10, etc. includes a network interface 1201, a processor 1202, and memory 1203. The network interface 1201 may be used to communicate with network nodes. The network interface 1201 may include, for example, a network interface card (NIC) compliant with the IEEE 802.3 series. IEEE stands for Institute of Electrical and Electronics Engineers.

[0087] The processor 1202 reads and executes software (computer programs) from the memory 1203 to perform processing on the core network node 10, etc., as described using a flowchart in the above embodiment. The processor 1202 may be, for example, a microprocessor, an MPU, or a CPU. The processor 1202 may include multiple processors.

[0088] Memory 1203 is composed of a combination of volatile and non-volatile memory. Memory 1203 may also include storage located away from the processor 1202. In this case, the processor 1202 may access memory 1203 via an I / O (Input / Output) interface, which is not shown.

[0089] In the example shown in Figure 12, memory 1203 is used to store a group of software modules. The processor 1202 can read these software modules from memory 1203 and execute them, thereby enabling the core network node 10 and the like, as described in the above embodiment.

[0090] As explained with reference to Figure 12, each processor in the core network node 10, etc., in the above-described embodiment executes one or more programs that include a set of instructions for causing a computer to perform the algorithm described with reference to the diagram.

[0091] In the examples described above, the program includes a set of instructions (or software code) that, when loaded into a computer, cause the computer to perform one or more of the functions described in the embodiments. The program may be stored on a non-temporary computer-readable medium or a physical storage medium. Examples, but not limited to, include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technologies, CD-ROM, digital versatile disc (DVD), Blu-ray® disc or other optical disc storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage devices. The program may be transmitted over a temporary computer-readable medium or a communication medium. Examples, but not limited to, include temporary computer-readable medium or a communication medium that includes electrically, optically, acoustically or otherwise propagating signals.

[0092] Furthermore, the technical concepts described herein are not limited to the embodiments described above, and may be modified as appropriate without departing from the spirit of the invention.

[0093] Some or all of the above embodiments may also be described as follows, but are not limited to the following: (Note 1) The first core network node, A detection unit for detecting congestion occurring in the first core network node, The system includes a communication unit that, when congestion occurs at the first core network node, sends a message to a wireless terminal indicating that congestion has occurred, which includes identification information of the second core network node. The aforementioned message instructs the selection of the second core network node. The first core network node. (Note 2) The message includes an information element indicating that congestion has occurred and instructing the selection of the second core network node. The first core network node as described in Appendix 1. (Note 3) The message includes a first information element indicating that congestion has occurred, and a second information element instructing the selection of the second core network node. The first core network node as described in Appendix 1. (Note 4) The aforementioned communications unit is If, after congestion occurs at the first core network node, the wireless terminal receives a registration request message requesting registration to the first core network node, the second core network node sends a response message to the wireless terminal that includes the identification information of the second core network node and indicates that congestion has occurred. The response message instructs the selection of the second core network node. The first core network node described in any one of the appendices 1 to 3. (Note 5) The aforementioned communications unit is The first core network node described in Appendix 4 sends a rejection message to the wireless terminal as the response message, rejecting the registration of the wireless terminal. (Note 6) The aforementioned communications unit is If congestion occurs at the first core network node after the wireless terminal has been registered with the first core network node, a deregistration request message indicating that congestion has occurred, including the identification information of the second core network node, is sent to the wireless terminal to request that it be deregistered. The release request message instructs the selection of the second core network node. The first core network node described in any one of the appendices 1 to 5. (Note 7) The aforementioned communications unit is A first core network node according to any one of the appendices 1 to 6, which transmits the message containing the identification information of the second core network node that is not experiencing congestion to the wireless terminal. (Note 8) The aforementioned communications unit is A first core network node as described in any one of the appendices 1 to 7, which includes the identification information of the second core network node, notified by the management node that manages the core network nodes, in the message. (Note 9) The aforementioned communications unit is The first core network node as described in Appendix 8, which sends a notification message to the management node containing information indicating that congestion has occurred at the first core network node, and receives the identification information of the second core network node included in a response message to the notification message. (Note 10) The aforementioned communications unit is A core network node according to any one of the appendices 1 to 9, which sends a message to the wireless terminal transmitting a call that is to be prioritized for processing, including the identification information of the second core network node, indicating that congestion has occurred, and instructing the terminal to select the second core network node. (Note 11) The aforementioned communications unit is A first core network node as described in any one of the appendices 1 to 9, which sends a message to wireless terminals other than the wireless terminal that transmits a call that is given priority for processing, including the identification information of the second core network node, indicating that congestion has occurred, and instructing the wireless terminal to select the second core network node. (Note 12) Access network node, A communication unit receives a message from a wireless terminal indicating that congestion has occurred at the first core network node and instructing the selection of a second core network node different from the first core network node, and the message includes identification information of the second core network node. The system includes a selection unit that, based on the identification information, selects the second core network node identified by the identification information as the destination for sending the registration request message included in the message, The aforementioned communications unit is An access network node that sends the registration request message to the second core network node. (Note 13) The aforementioned selection unit is If the message does not indicate that congestion has occurred at the first core network node, the destination for sending the registration request message is selected from the second core network node or a core network node different from the second core network node. If the message indicates that congestion has occurred at the first core network node, the access network node according to Appendix 12 selects the second core network node as the destination for the registration request message. (Note 14) A wireless terminal, A receiving unit receives a first message from a first core network node where congestion has occurred, indicating that congestion has occurred at the first core network node and instructing the selection of a second core network node different from the first core network node, wherein the first message includes identification information of the second core network node. The system includes a transmitting unit that notifies an access network node that congestion has occurred in the first core network node and sends a second message to the access network node instructing it to select the second core network node, The second message includes the identification information of the second core network node, Wireless terminal. (Note 15) The receiving unit is As the first message, a rejection message is received that rejects the registration request message. The rejection message notifies the access network node that congestion has occurred on the first core network node. The rejection message instructs the selection of the second core network node, The rejection message includes the identification information of the second core network node, The aforementioned transmitting unit The wireless terminal according to Appendix 14, which, after receiving the rejection message, sends the second message to the access network node, further including a registration request message requesting registration with the second core network node. (Note 16) The receiving unit is As the second message, a deregistration request message is received requesting the deregistration of the wireless terminal. The release request message notifies the access network node that congestion has occurred on the first core network node. The release request message instructs the selection of the second core network node, The release request message includes the identification information of the second core network node, The aforementioned transmitting unit A wireless terminal according to Appendix 14 or 15, which, after receiving the deactivation request message, transmits the second message to the access network node, further including a registration request message requesting registration to the second core network node. (Note 17) A communication method performed at a first core network node, The first core network node detects congestion, When congestion occurs at the first core network node, a message indicating that congestion has occurred, including the identification information of the second core network node, is sent to the wireless terminal. The message is a communication method performed at the first core network node, which instructs the selection of the second core network node. (Note 18) The communication method according to Appendix 17, wherein the message includes an information element indicating that congestion has occurred and instructing the selection of the second core network node. (Note 19) The communication method according to Appendix 17, wherein the message includes a first information element indicating that congestion has occurred, and a second information element instructing the selection of the second core network node. (Note 20) If, after congestion occurs at the first core network node, the wireless terminal receives a registration request message requesting registration to the first core network node, the second core network node sends a response message to the wireless terminal that includes the identification information of the second core network node and indicates that congestion has occurred. The response message is a communication method as described in Appendix 17, which instructs the selection of the second core network node. (Note 21) The communication method described in Appendix 20, wherein, as the response message, a rejection message refusing registration of the wireless terminal is sent to the wireless terminal. (Note 22) If congestion occurs at the first core network node after the wireless terminal has been registered with the first core network node, a deregistration request message indicating that congestion has occurred, including the identification information of the second core network node, is sent to the wireless terminal to request that it be deregistered. The release request message is a communication method according to any one of the items 17 to 21, which instructs the selection of the second core network node. (Note 23) A communication method according to any one of the appendices 17 to 22, comprising transmitting the message containing the identification information of the second core network node, which is not experiencing congestion, to the wireless terminal. (Note 24) A communication method according to any one of the appendices 17 to 23, wherein the message includes the identification information of the second core network node, which has been notified by the management node that manages the core network node. (Note 25) The communication method according to Appendix 24, comprising sending a notification message to the management node containing information indicating that congestion has occurred at the first core network node, and receiving the identification information of the second core network node included in a response message to the notification message. (Note 26) The communication method according to any one of Appendix 17 to 25, wherein a message is sent to the wireless terminal transmitting a call that is to be prioritized for processing, the message includes the identification information of the second core network node, indicates that congestion has occurred, and instructs the terminal to select the second core network node. (Note 27) The communication method according to any one of the appendices 17 to 25, which includes sending a message to a wireless terminal other than the wireless terminal that transmits a call that is given priority for processing, a message that includes the identification information of the second core network node, indicates that congestion has occurred, and instructs the selection of the second core network node. (Note 28) A communication method executed at an access network node, A message is received from a wireless terminal indicating that congestion has occurred at the first core network node and instructing the selection of a second core network node different from the first core network node, and the message includes identification information of the second core network node. Based on the identification information, the second core network node identified by the identification information is selected as the destination for the registration request message included in the message. A communication method performed on an access network node, which sends the registration request message to the second core network node. (Note 29) When selecting the recipient of the aforementioned registration request message, If the message does not indicate that congestion has occurred at the first core network node, the destination for sending the registration request message is selected from the second core network node or a core network node different from the second core network node. The communication method according to Appendix 28, wherein if the message indicates that congestion has occurred at the first core network node, the second core network node is selected as the destination for the registration request message. (Note 30) A communication method performed in a wireless terminal, A first message is received from a first core network node where congestion has occurred, indicating that congestion has occurred at the first core network node and instructing the selection of a second core network node different from the first core network node, the first message includes identification information of the second core network node, The system notifies the access network node that congestion has occurred in the first core network node and sends a second message to the access network node instructing it to select the second core network node. A communication method performed in a wireless terminal, wherein the second message includes identification information of the second core network node. (Note 31) As the first message, a rejection message is received that rejects the registration request message. The rejection message notifies the access network node that congestion has occurred on the first core network node. The rejection message instructs the selection of the second core network node, The rejection message includes the identification information of the second core network node, The communication method according to Appendix 30, wherein, after receiving the rejection message, the second message further includes a registration request message requesting registration to the second core network node, which is then sent to the access network node. (Note 32) As the second message, a deregistration request message is received requesting the deregistration of the wireless terminal. The release request message notifies the access network node that congestion has occurred on the first core network node. The release request message instructs the selection of the second core network node, The release request message includes the identification information of the second core network node, The communication method according to Appendix 30 or 31, wherein, after receiving the deactivation request message, the second message further includes a registration request message requesting registration to the second core network node, and is transmitted to the access network node. (Note 33) A program to be executed by a computer which is the first core network node, The first core network node detects congestion, A program that causes a computer acting as a core network node to send a message to a wireless terminal indicating that congestion has occurred, which includes identification information of the second core network node, instructing the selection of a second core network node when congestion occurs at the first core network node. (Note 34) A program that is executed on a computer that is an access network node, A message is received from the wireless terminal indicating that congestion has occurred in the first core network node and instructing the selection of a second core network node different from the first core network node. The message includes identification information of the second core network node, and based on the identification information, the second core network node identified by the identification information is selected as the destination for the registration request message included in the message. A program that causes a computer, which is an access network node, to send the registration request message to the second core network node. (Note 35) A program to be executed on a computer that is a wireless terminal, A first message is received from a first core network node where congestion has occurred, indicating that congestion has occurred at the first core network node and instructing the selection of a second core network node different from the first core network node, the first message includes identification information of the second core network node, A program that causes a wireless terminal computer to send to an access network node a second message, which includes identification information of the second core network node, instructing the access network node to select the second core network node, and which notifies the access network node that congestion has occurred in the first core network node.

[0094] Furthermore, the technical concepts described in this disclosure are not limited to the embodiments described above, and may be modified as appropriate without departing from the spirit of the invention.

[0095] Although the present invention has been described above with reference to embodiments, the present invention is not limited thereto. Various modifications to the structure and details of the present invention can be made that are understandable to those skilled in the art within the scope of the invention.

[0096] This application claims priority based on Japanese Patent Application No. 2022-093490, filed on 9 June 2022, and incorporates all of its disclosures herein. [Explanation of Symbols]

[0097] 10 core network nodes 11 Detection Unit 12 Communications Department 20 Access Network Nodes 21 Communications Department 22 Specific section 30 Wireless terminals 31 Receiver 32 Transmitter 40 5GC 41 AMF 42 AMF 43 NRF 50 RAN 51 gNB 60 UE

Claims

1. The first core network node, A detection means for detecting congestion occurring in the first core network node, The system includes a communication means that, when congestion occurs at the first core network node and a Registration Request message indicating that it is an Emergency Registration is received from the first wireless terminal transmitting a call that should be given priority processing, transmits a message via the access network node to the first wireless terminal transmitting the call that should be given priority processing, which includes identification information of a second core network node different from the first core network node, an information element indicating that congestion has occurred, and an information element instructing the selection of the second core network node, and instructing the selection of the second core network node. The first core network node.

2. The aforementioned communication means is The first core network node according to claim 1, wherein, when congestion occurs in the first core network node and a Registration Request message is received from the second wireless terminal that does not indicate that it is an Emergency Registration, the first core network node transmits a message indicating that congestion has occurred, without including identification information of the second core network node, to the second wireless terminal via the access network node.

3. Access network node, When a first Registration Request message indicating that it is an Emergency Registration is sent from a first wireless terminal transmitting a call that is to be processed as a priority to a first core network node, a receiving means receives a message from the first wireless terminal transmitting the call that is to be processed as a priority, which indicates that congestion has occurred at the first core network node, includes identification information of a second core network node different from the first core network node, includes an information element that instructs the selection of the second core network node, and instructs the selection of the second core network node. If the message includes a second Registration Request message, the selection means selects the second core network node identified by the identification information as the destination for the second Registration Request message, An access network node comprising: a transmission means for sending the second Registration Request message to the second core network node according to the information element that instructs the selection;

4. A wireless terminal that transmits a call that is given priority for processing, When a first Registration Request message indicating Emergency Registration is sent to a first core network node, a receiving means receives a first message from the first core network node via an access network node, which indicates that congestion has occurred at the first core network node, includes identification information of a second core network node different from the first core network node, includes an information element instructing the selection of the second core network node, and instructs the selection of the second core network node. The system includes a transmission means for transmitting a second message to the access network node, which indicates that congestion has occurred at the first core network node, includes identification information of the second core network node, includes an information element that instructs the selection of the second core network node, and instructs the selection of the second core network node. The second message includes the second Registration Request message of the wireless terminal, Wireless terminal.

5. A communication method performed at a first core network node, The first core network node detects congestion, A communication method performed in a first core network node, wherein, when congestion occurs in the first core network node and a Registration Request message indicating that it is an Emergency Registration is received from a first wireless terminal transmitting a call that is to be processed as a priority, the first core network node transmits a message via an access network node to the first wireless terminal transmitting the call that is to be processed as a priority, the message includes identification information of a second core network node different from the first core network node, an information element indicating that congestion has occurred, and an information element instructing the selection of the second core network node, and instructing the selection of the second core network node.

6. A communication method executed at an access network node, When a first Registration Request message indicating that it is an Emergency Registration is sent from a first wireless terminal transmitting a call that is to be processed as a priority to a first core network node, the first wireless terminal transmitting the call that is to be processed as a priority receives a message indicating that congestion has occurred at the first core network node, including identification information of a second core network node different from the first core network node, including an information element that instructs the selection of the second core network node, and instructing the selection of the second core network node. If the message includes a second Registration Request message, the second core network node identified by the identification information is selected as the destination for the second Registration Request message. A communication method performed on an access network node, which sends the second Registration Request message to the second core network node according to the information element that instructs the selection.

7. A communication method performed in a wireless terminal that transmits a call that is given priority for processing, When a first Registration Request message indicating Emergency Registration is sent to the first core network node, a first message indicating that congestion has occurred at the first core network node, including identification information of a second core network node different from the first core network node, including an information element instructing the selection of the second core network node, is received from the first core network node via the access network node, and the first message instructing the selection of the second core network node is received. A second message is sent to the access network node indicating that congestion has occurred in the first core network node, including identification information of the second core network node, including an information element that instructs the selection of the second core network node, and instructing the selection of the second core network node. A communication method performed in a wireless terminal, wherein the second message includes a second Registration Request message of the wireless terminal.

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