Network node, terminal, and communication method

Abstract

This network node in a first communication system includes: a reception unit that receives, from a first network node, a first message including information indicating that a terminal is located in the service area of a second communication system, and receives, from a second network node, a second message including information indicating an incoming call of a short message service to the terminal; and a transmission unit that transmits, to the first network node, a third message requesting a call of the terminal, the third message including information indicating the incoming call and an instruction to respond with the first communication system.

Description

Network node, terminal, and communication method

[0001] The present invention relates to a network node, a terminal, and a communication method in a communication system.

[0002] 3GPP (registered trademark) (3rd Generation Partnership Project) is currently studying a wireless communication system called 5G or NR (New Radio) (hereinafter, the wireless communication system will be referred to as "5G" or "NR") in order to achieve a larger system capacity, a higher data transmission speed, and a lower latency in wireless sections. Various wireless technologies are being studied for 5G to meet the requirements of achieving a throughput of 10 Gbps or more while keeping latency in wireless sections to 1 ms or less.

[0003] In NR, a network architecture including a 5G Core Network (5GC) corresponding to the Evolved Packet Core (EPC), which is the core network in the Long Term Evolution (LTE) network architecture, and a Next Generation Radio Access Network (NG-RAN) corresponding to the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), which is the Radio Access Network (RAN) in the LTE network architecture, is being considered (for example, Non-Patent Document 1). Here, a system including the EPC may be referred to as an Evolved Packet System (EPS), and a system including the 5GC may be referred to as a 5G System (5GS).

[0004] 3GPP TS 23.501 V18.4.0 (2023-12) 3GPP TS 23.502 V18.4.0 (2023-12) 3GPP TS 29.503 V18.4.0 (2023-12) 3GPP TS 38.413 V18.0.0 (2023-12) 3GPP TS 24.501 V18.5.0 (2023-12) 3GPP TS 23.273 V18.4.0 (2023-12) 3GPP TS 23.041 V18.3.0 (2023-12)

[0005] In 5GS, it is possible to fall back from 5GS to EPS (EPS FB (Fall Back)) in case only EPS supports voice call services.

[0006] However, EPS FB uses special network nodes called combo nodes, which can be inconvenient when migrating to new generation systems, etc. Also, EPS FB was only used for voice call services.

[0007] The present invention has been made in view of the above points, and has as its object to provide services other than voice call services in a wireless communication system by performing system fallback without using a special network node.

[0008] According to the disclosed technology, there is provided a network node in a first communication system, the network node having a receiving unit that receives from the first network node a first message including information indicating that a terminal is within the range of a second communication system and receives from the second network node a second message including information indicating an incoming short message service call to the terminal, and a transmitting unit that transmits to the first network node a third message requesting a call to the terminal, the third message including information indicating the incoming call and an instruction to respond in the first communication system.

[0009] According to the disclosed technology, in a wireless communication system, it is possible to provide services other than voice call services by performing system fallback without using a special network node.

[0010] FIG. 1 is a diagram for explaining an example of a communication system. FIG. 1 is a diagram for explaining an example of a communication system in a roaming environment. FIG. 2 is a diagram showing an example of a first sequence diagram in an embodiment of the present invention. FIG. 3 is a diagram showing an example of a second sequence diagram in an embodiment of the present invention. FIG. 4 is a diagram showing an example of a third sequence diagram in an embodiment of the present invention. FIG. 5 is a diagram showing an example of a fourth sequence diagram in an embodiment of the present invention. FIG. 6 is a diagram showing an example of a sixth sequence diagram in an embodiment of the present invention. FIG. 1 is a diagram showing an example of a functional configuration of a base station 10 and a network node 30 in an embodiment of the present invention. FIG. 2 is a diagram showing an example of a functional configuration of a terminal 20 in an embodiment of the present invention. FIG. 3 is a diagram showing an example of a hardware configuration of a base station 10, a terminal 20, and a network node 30 in an embodiment of the present invention. FIG. 4 is a diagram showing an example of a configuration of a vehicle 2001 in an embodiment of the present invention.

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is an example, and the embodiment to which the present invention is applied is not limited to the following embodiment.

[0012] In the operation of the wireless communication system according to the embodiment of the present invention, existing technology is used as appropriate. However, the existing technology is, for example, the existing LTE, but is not limited to the existing LTE. Furthermore, the term "LTE" used in this specification has a broad meaning including LTE-Advanced, and systems subsequent to LTE-Advanced (e.g., NR), or wireless LAN (Local Area Network), unless otherwise specified.

[0013] Furthermore, in the embodiments of the present invention, "configuring" radio parameters and the like may mean that predetermined values ​​are pre-configured, or that radio parameters notified from the network node 30 or the terminal 20 are set.

[0014] Fig. 1 is a diagram illustrating an example of a communication system. As shown in Fig. 1, the communication system is composed of a UE, which is a terminal 20, and multiple network nodes 30. Hereinafter, it is assumed that one network node 30 corresponds to each function, but multiple functions may be realized by one network node 30, or multiple network nodes 30 may realize one function. Furthermore, the "connection" described below may be a logical connection or a physical connection.

[0015] The RAN (Radio Access Network) is a network node 30 having a radio access function, which may include a base station 10, and is connected to a UE, an AMF (Access and Mobility Management Function), and a UPF (User Plane Function). The AMF is a network node 30 having functions such as terminating the RAN interface, terminating the NAS (Non-Access Stratum), registering management, connecting management, reachability management, and terminal mobility management. The UPF is a network node 30 having functions related to processing user plane data, such as a PDU (Protocol Data Unit) session point to the outside that interconnects with the DN (Data Network), packet routing and forwarding, and user plane Quality of Service (QoS) handling. The UPF and the DN constitute a network slice. In the wireless communication network according to the embodiment of the present invention, multiple network slices are constructed.

[0016] The AMF is connected to the UE, RAN, SMF (Session Management function), NSSF (Network Slice Selection Function), NEF (Network Exposure Function), NRF (Network Repository Function), UDM (Unified Data Management), AUSF (Authentication Server Function), PCF (Policy Control Function), and AF (Application Function). The AMF, SMF, NSSF, NEF, NRF, UDM, AUSF, PCF, and AF are network nodes 30 that are mutually connected via interfaces based on their respective services, Namf, Nsmf, Nnssf, Nnef, Nnrf, Nudm, Nausf, Npcf, and Naf.

[0017] The SMF is a network node 30 having functions such as session management, UE IP (Internet Protocol) address allocation and management, DHCP (Dynamic Host Configuration Protocol) function, ARP (Address Resolution Protocol) proxy, and roaming function. The NEF is a network node 30 having a function of notifying other NFs (Network Functions) of capabilities and events. The NSSF is a network node 30 having functions such as selecting a network slice to which a UE connects, determining an allowed NSSAI (Network Slice Selection Assistance Information), determining an NSSAI to be set, and determining an AMF set to which a UE connects. The PCF is a network node 30 having a function of controlling network policies. The AF is a network node 30 having a function of controlling application servers. The NRF is a network node 30 having a function of discovering NF instances that provide services. The UDM is a network node 30 that manages subscriber data and authentication data. The UDM is connected to a UDR (User Data Repository) that stores the data.

[0018] Fig. 2 is a diagram illustrating an example of a communication system in a roaming environment. As shown in Fig. 2, the network is composed of a UE, which is a terminal 20, and multiple network nodes 30. Hereinafter, it is assumed that one network node 30 corresponds to each function, but multiple functions may be realized by one network node 30, or multiple network nodes 30 may realize one function. Furthermore, the "connection" described below may be a logical connection or a physical connection.

[0019] The RAN is a network node 30 having a radio access function, and is connected to the UE, the AMF, and the UPF. The AMF is a network node 30 having functions such as RAN interface termination, NAS termination, registration management, connection management, reachability management, and mobility management. The UPF is a network node 30 having functions such as a PDU session point to the outside that interconnects with the DN, packet routing and forwarding, and user plane QoS handling. The UPF and the DN constitute a network slice. In the wireless communication network according to the embodiment of the present invention, multiple network slices are constructed.

[0020] The AMF is connected to the UE, RAN, SMF, NSSF, NEF, NRF, UDM, AUSF, PCF, AF, and SEPP (Security Edge Protection Proxy). The AMF, SMF, NSSF, NEF, NRF, UDM, AUSF, PCF, and AF are network nodes 30 that are interconnected via respective service-based interfaces, Namf, Nsmf, Nnssf, Nnef, Nnrf, Nudm, Nausf, Npcf, and Naf.

[0021] The SMF is a network node 30 having functions such as session management, UE IP address allocation and management, DHCP function, ARP proxy, and roaming function. The NEF is a network node 30 having a function of notifying other NFs of capabilities and events. The NSSF is a network node 30 having functions such as selecting a network slice to which a UE connects, determining an allowed NSSAI, determining a configured NSSAI, and determining an AMF set to which a UE connects. The PCF is a network node 30 having a function of controlling network policies. The AF is a network node 30 having a function of controlling application servers. The NRF is a network node 30 having a function of discovering NF instances that provide services. The SEPP is a non-transparent proxy that filters control plane messages between PLMNs (Public Land Mobile Networks). The vSEPP shown in FIG. 2 is a SEPP in the visited network, and the hSEPP is a SEPP in the home network.

[0022] As shown in Figure 2, a UE is in a roaming environment connected to a RAN and an AMF in a Visited PLMN (VPLMN). The VPLMN and a Home PLMN (HPLMN) are connected via a vSEPP and an hSEPP. The UE can communicate with a UDM in the HPLMN via the AMF in the VPLMN, for example.

[0023] In addition, 5GS allows for fallback from 5GS to EPS (EPS FB (Fall Back)) in case only EPS supports voice call services. EPS FB uses a combo node called SMF + PGW (Packet Data Network Gateway)-C (Control plane) and a UPF shared by EPS and 5GS, which can cause inconvenience when migrating to a new generation system.

[0024] (Example) A procedure for providing services other than voice call services by performing system fallback without using a special network node in a wireless communication system will be described. In this example, a fallback from a next-generation system, 6GS (6GS network), to 5GS (5GS network) is assumed. Here, a base station 10A, an AMF 30A, an SMF 30B, and a UPF 30C are deployed in the 5GS, and a 6G base station 10B, a 6GAMF 30D, a 6GSMF 30E, and a 6GUPF 30F are deployed in the 6GS. Furthermore, in this example, the following conditions are satisfied: When switching between 5GS and 6GS, data is allowed to be discarded, or data is protected in the application layer so that it is not discarded. A (5G / 6G) UDM 30G, which is a UDM shared by both the 5GS and 6GS systems, is deployed. A terminal 20 is capable of simultaneous transmission and reception (1Tx / 1Rx) in only one of the 5GS and 6GS systems. That is, the terminal 20 cannot simultaneously transmit and receive (2Tx / 2Rx) in the 5GS and 6GS systems. The terminal 20 can be registered in both the 5GS and 6GS systems (dual registration) using a single subscriber information.

[0025] Below, two embodiments (first and second embodiments) will be described under the above conditions. In each embodiment, three examples of services other than voice calls will be described: a short message service (SMS), a location information acquisition service, and a public warning service using a public warning system (PWS). Furthermore, as network nodes providing the services, an SMS function (SMSF) 30L is deployed for the short message service, a gateway mobile location centre (GLMC) 30M is deployed for the location information acquisition service, and a cell broadcast centre (CBC) 30N is deployed for the public warning service.

[0026] The details of the process will be explained below using a sequence diagram. Requests, responses, notifications, etc. sent and received in the procedures described below may be called messages (for example, request messages).

[0027] (First Example) In the first example, a procedure for providing services other than voice call services by causing the system to fall back without using a special network node when there is no cooperation between AMF30A and 6GAMF30D will be described.

[0028] (Short Message Service) An example of a short message service will be described. FIG. 3 is a diagram showing an example of a first sequence diagram in an embodiment of the present invention. The processing of each step in FIG. 3 will be described below. Section 4.13.3.6 of Non-Patent Document 2 can be referred to for the procedure of existing specifications related to the reception of short messages (processing executed before S101, etc.).

[0029] S101: The SMSF 30L transmits to the AMF 30A a request message (Namf_MT_EnableUEReachability request) requesting notification of an SMS arrival at the terminal 20. The request message includes information indicating that the terminal 20 has an SMF arrival.

[0030] S102: It is assumed that AMF 30A has previously set information indicating that terminal 20 is in the 6GS area (6G area flag = 1) in its own device based on information received from UDM 30G. Since the information (6G area flag = 1) is set, AMF 30A determines not to call terminal 20 on the 5GS side but to call terminal 20 on the 6GS side.

[0031] S103: AMF 30A transmits to UDM 30G a request message (Nudm_UECM_Update request) requesting a call to terminal 20. The request message includes information indicating that an SMS is being received in 5GS (5G SMS incoming flag = 1), and is expressed as, for example, Nudm_UECM_Update request (Amf3GppAccessRegistrationModification (5G SMS incoming flag = 1)).

[0032] S104: UDM30G adds information indicating that an SMS is being received at 5GS (5G SMS receiving flag = 1) to the stored information regarding AMF30A and information regarding 6GAMF30D.

[0033] S105: The UDM 30G transmits to the 6GAMF 30D a request message (Nudm_UECM_Update_Notify request) to notify and request an update of information relating to the terminal 20. The request message includes information indicating that the terminal 20 is receiving an SMS in 5GS, and is expressed as, for example, Nudm_UECM_Update_Notify request (6gAmf3GppAccessRegistrationModification (5G SMS receiving flag = 1)).

[0034] S106: The 6GAMF30D includes information indicating that the terminal 20 is receiving a voice call in 5GS (5G SMS incoming call flag = 1) in the information stored in the 6GAMF30D and registered in the UDM30G regarding the device itself.

[0035] S107: The 6GAMF 30D transmits to the UDM 30G a response message (Nudm_UECM_Update_Notify response) in response to the request message received in S105. The response message includes information indicating that the terminal 20 is receiving an SMS in 5GS, and is expressed as, for example, Nudm_UECM_Update_Notify response (6gAmf3GppAccessRegistrationModification (5G SMS receiving flag = 1)).

[0036] S108: The UDM 30G transmits a response message (Nudm_UECM_Update response) to the request message received in S103 to the AMF 30A. The request message includes information indicating that an SMS is being received in 5GS (5G SMS incoming flag = 1), and is expressed as, for example, Nudm_UECM_Update response (Amf3GppAccessRegistrationModification (5G SMS incoming flag = 1)).

[0037] S109: Since the terminal 20 is receiving an SMS in the 5GS, the 6GAMF30D determines to have the terminal 20 execute a service request in the 5GS to respond to the SMS incoming call.

[0038] S110 and S111 are processes that are executed when the terminal 20 is communicating in 6GS (connection mode).

[0039] S110: The 6GAMF 30D transmits to the 6G base station 10B a message (Downlink NAS Transport, see section 9.2.5.2 of Non-Patent Document 4) including a request for a response to an incoming SMS message in a system (5GS) other than the currently communicating system (6GS). The message includes information indicating that the wireless access type is a wireless system used in 5GS (RAT type=NR) and information indicating that the purpose of the message is to notify that an SMS message is incoming in 5GS. The message is expressed as, for example, Downlink NAS Transport(NAS-PDU(Notification(Access Type=3GPP access, RAT type=NR, Purpose=5G SMS incoming))) (see section 8.2.23.1 of Non-Patent Document 5, etc.).

[0040] S111: The 6G base station 10B transmits a message (DL Information Transfer) for transferring the information received in S110 to the terminal 20. This message is expressed as, for example, DL Information Transfer (dedicated NAS-Message (Notification (Access Type = 3GPP access, RAT type = NR, Purpose = 5G SMS incoming))).

[0041] S112 and S113 are processes executed when the terminal 20 is in the idle mode in 6GS.

[0042] S112: The 6GAMF 30D transmits to the 6G base station 10B a paging message (Paging) to call the idle mode terminal 20. The message includes a request for a response to an incoming SMS message in a system (5GS) other than the currently camped system (6GS), information indicating that the wireless access type is wireless used in 5GS (RAT type=NR), and information indicating that the purpose of the message is to notify that an SMS message is being received in 5GS.

[0043] S113: The 6G base station 10B transmits to the terminal 20 a paging message (Paging) generated from the message received in S112 to call the terminal 20 in idle mode.

[0044] S114: The terminal 20 determines to switch from 6GS to 5GS by an automatic response by the terminal 20 in response to the message received in S111 or S113, or by an operation by the user.

[0045] S115: Following S111, the procedures from S115 to S117 are executed. The terminal 20 transmits a message (UL Information Transfer) including information indicating switching to 5GS to the 6G base station 10B. This message is expressed as, for example, UL Information Transfer (dedicated NAS-Message (Notification response (switching to 5G))).

[0046] S116: The 6G base station 10B transmits to the 6GAMF 30D a message (Uplink NAS Transport) including information indicating switching to 5GS received in S115. This message is expressed as, for example, Uplink NAS Transport (NAS-PDU (Notification response (switching to 5G))).

[0047] S117: The 6GAMF30D decides to deactivate the 6G data communication PDU session, and processing related to the deactivation is executed.

[0048] From then on, processing after switching to 5GS will be carried out.

[0049] S121: The terminal 20 switches the connected system from 6GS to 5GS, and determines to execute a service request to receive SMS.

[0050] S122: The terminal 20 transmits a message (service request) requesting reception of an SMS to the base station 10A based on the procedure of the existing specifications.

[0051] S123: The base station 10A transmits the message (service request) received in S122 to the AMF 30A.

[0052] S124: Based on the existing procedure, the terminal 20 receives the incoming SMS.

[0053] S125: AMF30A erases the information indicating that SMS is being received in 5GS and the information indicating that the terminal 20 is in the 6G area from the registration information for UDM30G stored in its own device.

[0054] S126: AMF 30A transmits to UDM 30G a request message (Nudm_UECM_Update request) requesting an update of information related to the registration of terminal 20. The request message includes an instruction to erase information indicating that an SMS is being received in 5GS and information indicating that the terminal is in 6G service area, and is expressed as, for example, Nudm_UECM_Update request (Amf3GppAccessRegistrationModification (5G SMS receiving flag = 0, 6G in service area flag = 0)).

[0055] S127: In response to the request message received in S126, UDM30G erases the information indicating that an SMS is being received via 5GS and the information indicating that the device is in the 6G area from the information regarding AMF30A and the information regarding 6GAMF30D.

[0056] S128: UDM30G sends a request message (Nudm_UECM_Update_Notify request) to 6GAMF30D, which includes a request to erase information indicating that an SMS is being received in 5GS and information indicating that the device is in the 6G area.

[0057] S129: The 6GAMF 30D sends to the UDM 30G a response message (Nudm_UECM_Update_Notify response) in response to the request message received in S128.

[0058] S130: The UDM 30G transmits to the AMF 30A a response message (Nudm_UECM_Update response) in response to the request message received in S126. The response message includes a notification that the information indicating that an SMS is being received in 5GS and the information indicating that the 6G device is in the service area have been deleted, and is represented as, for example, Nudm_UECM_Update response (Amf3GppAccessRegistrationModification (5G SMS receiving flag = 0, 6G in-service area flag = 0)).

[0059] (Location Information Acquisition Service) An example of a location information acquisition service will be described. FIG. 4 is a diagram showing an example of a second sequence diagram in an embodiment of the present invention. The processing of each step in FIG. 4 will be described below. Section 6.1.1 of Non-Patent Document 6 can be referred to for the procedure of existing specifications related to the location information acquisition service (processing executed before S201, etc.).

[0060] S201: The GMLC 30M transmits to the AMF 30A a request message (Namf_Location_ProvidePositioningInfo request) requesting acquisition of location information from the terminal 20. The request message includes information indicating that there is a request for acquisition of location information from the terminal 20.

[0061] S202: It is assumed that AMF 30A has previously set information indicating that terminal 20 is in the 6GS area (6G area flag = 1) in its own device based on information received from UDM 30G. Since the information (6G area flag = 1) is set, AMF 30A determines not to call terminal 20 on the 5GS side but to call terminal 20 on the 6GS side.

[0062] S203: AMF 30A transmits to UDM 30G a request message (Nudm_UECM_Update request) requesting to call terminal 20. The request message includes information indicating that a request to obtain location information is being received in 5GS (5G ML-LR (Mobile Terminated-Location Request) flag = 1), and is expressed as, for example, Nudm_UECM_Update request (Amf3GppAccessRegistrationModification (5G ML-LR flag = 1)).

[0063] S204: UDM30G adds information indicating that a request to obtain location information is being received at 5GS (5G MT-LR flag = 1) to the stored information regarding AMF30A and information regarding 6GAMF30D.

[0064] S205: The UDM 30G transmits to the 6GAMF 30D a request message (Nudm_UECM_Update_Notify request) notifying and requesting an update of information relating to the terminal 20. The request message includes information indicating that the terminal 20 is receiving a request to acquire location information in 5GS, and is expressed as, for example, Nudm_UECM_Update_Notify request (6gAmf3GppAccessRegistrationModification (5G 5G MT-LR flag = 1)).

[0065] S206: 6GAMF30D includes information indicating that terminal 20 is receiving a request to obtain location information in 5GS (5G MT-LR flag = 1) in the information stored in its own device and registered in UDM30G regarding its own device.

[0066] S207: The 6GAMF30D transmits to the UDM30G a response message (Nudm_UECM_Update_Notify response) in response to the request message received in S205. The response message includes information indicating that the terminal 20 is receiving a request to acquire location information in 5GS, and is expressed as, for example, Nudm_UECM_Update_Notify response (6gAmf3GppAccessRegistrationModification (5G MT-LR flag = 1)).

[0067] S208: UDM 30G transmits a response message (Nudm_UECM_Update response) to the request message received in S203 to AMF 30A. The request message includes information indicating that a request to acquire location information is being received in 5GS (5G MT-LR flag = 1), and is expressed as, for example, Nudm_UECM_Update response (Amf3GppAccessRegistrationModification (5G MT-LR flag = 1)).

[0068] S209: Since the terminal 20 is currently receiving a request to obtain location information in the 5GS, the 6GAMF30D decides to have the terminal 20 execute a service request in the 5GS in response to the request to obtain location information.

[0069] S210 and S211 are processes that are executed when the terminal 20 is communicating in 6GS (connection mode).

[0070] S210: The 6GAMF 30D transmits to the 6G base station 10B a message (Downlink NAS Transport, see section 9.2.5.2 of Non-Patent Document 4) including a request for a response to a request for acquiring location information in a system (5GS) other than the system (6GS) currently in communication. The message includes information indicating that the wireless access type is a wireless system used in 5GS (RAT type=NR) and information indicating that the purpose of the message is to notify that a request for acquiring location information in 5GS is being received. The message is expressed as, for example, Downlink NAS Transport (NAS-PDU (Notification (Access Type=3GPP access, RAT type=NR, Purpose=5G MT-LR))) (see section 8.2.23.1 of Non-Patent Document 5, etc.).

[0071] S211: The 6G base station 10B transmits a message (DL Information Transfer) for transferring the information received in S210 to the terminal 20. This message is expressed as, for example, DL Information Transfer (dedicated NAS-Message (Notification (Access Type = 3GPP access, RAT type = NR, Purpose = 5G MT-LR))).

[0072] S212 and S213 are processes executed when the terminal 20 is in the idle mode in 6GS.

[0073] S212: The 6GAMF 30D transmits to the 6G base station 10B a paging message (Paging) to call the terminal 20 in idle mode. The message includes a request for a response to a request to acquire location information in a system (5GS) other than the currently camped system (6GS), information indicating that the wireless access type is wireless used in 5GS (RAT type=NR), and information indicating that the purpose of the message is to notify that a request to acquire location information in 5GS is being received.

[0074] S213: The 6G base station 10B transmits to the terminal 20 a paging message (Paging) generated from the message received in S212 to call the terminal 20 in idle mode.

[0075] S214: In response to the message received in S211 or S213, the terminal 20 determines to switch from 6GS to 5GS by an automatic response by the terminal 20 or by an operation by the user.

[0076] S215: Following S211, the procedures from S215 to S217 are executed. The terminal 20 transmits a message (UL Information Transfer) including information indicating switching to 5GS to the 6G base station 10B. This message is expressed as, for example, UL Information Transfer (dedicated NAS-Message (Notification response (switching to 5G))).

[0077] S216: The 6G base station 10B transmits to the 6GAMF 30D a message (Uplink NAS Transport) including information indicating switching to 5GS received in S215. This message is expressed as, for example, Uplink NAS Transport (NAS-PDU (Notification response (switching to 5G))).

[0078] S217: 6GAMF30D decides to deactivate the 6G data communication PDU session, and processing related to the deactivation is executed.

[0079] From then on, processing after switching to 5GS will be carried out.

[0080] S221: The terminal 20 switches the connected system from 6GS to 5GS, and determines to execute a service request to receive a request for obtaining location information.

[0081] S222: The terminal 20 transmits a message (service request) requesting acquisition of location information to the base station 10A based on the procedure of the existing specifications.

[0082] S223: The base station 10A transmits the message (service request) received in S408 to the AMF 30A.

[0083] S224: Based on the existing procedure, the terminal 20 receives a request to acquire location information.

[0084] S225: AMF30A erases the information indicating that a request to obtain location information is being received in 5GS and the information indicating that the terminal 20 is in the 6G area from the registration information for UDM30G stored in its own device.

[0085] S226: AMF 30A transmits to UDM 30G a request message (Nudm_UECM_Update request) requesting an update of information related to the registration of terminal 20. The request message includes an instruction to delete information indicating that a request to acquire location information is being received in 5GS and information indicating that the terminal is present in 6G, and is expressed as, for example, Nudm_UECM_Update request (Amf3GppAccessRegistrationModification (5G MT-LR flag = 0, 6G present in area flag = 0)).

[0086] S227: In response to the request message received in S226, UDM30G erases the information indicating that a request to obtain location information is being received in 5GS and the information indicating that the device is in the 6G coverage area from the information regarding AMF30A and the information regarding 6GAMF30D.

[0087] S228: UDM30G sends to 6GAMF30D a request message (Nudm_UECM_Update_Notify request) including a request to erase information indicating that a request to obtain location information is being received in 5GS and information indicating that the device is in the 6G coverage area.

[0088] S229: The 6GAMF 30D sends a response message (Nudm_UECM_Update_Notify response) to the request message received in S228 to the UDM 30G.

[0089] S230: The UDM 30G transmits to the AMF 30A a response message (Nudm_UECM_Update response) in response to the request message received in S226. The response message includes a notification that the information indicating that a location information acquisition request is being received in 5GS and the information indicating that the 6G area is present have been deleted, and is represented as, for example, Nudm_UECM_Update response (Amf3GppAccessRegistrationModification (5G MT-LR flag = 0, 6G area present flag = 0)).

[0090] (Public Warning Service) An example of a public warning service will be described. Fig. 5 is a diagram showing an example of a third sequence diagram in an embodiment of the present invention. The processing of each step in Fig. 5 will be described below. Section 9.1.3.5.2 of Non-Patent Document 7 can be referred to for the procedure of existing specifications related to the public warning service (PWS transmission processing on the 5GS side, etc.).

[0091] S301: The CBC 30N transmits to the AMF 30A a request message (Namf_NonUeN2Message Transfer request) requesting transmission of warning information to the terminal 20. The request message is expressed as, for example, Namf_NonUeN2Message Transfer request (N2InformationTransferReqData (n2Information (Write-Replace Warning Request))).

[0092] S302: The AMF 30A determines to prompt the terminal 20 located in the 6GS area to move (camp) to the 5GS area in order to provide the terminal 20 with warning information.

[0093] S303: The AMF 30A transmits to the UDM 30G a request message (Namf_EventExposure Notify request) requesting a call to the terminal 20 via 6GS, the request message including information indicating that alert information is being transmitted. The request message includes information regarding the area to which the alert information is distributed and information regarding the content of the alert information. For example, the request message is expressed as Namf_EventExposure Notify_request (AmfEventNotification(reportList(type(PWS request received), areaList (pwsInfo)))).

[0094] S304: The UDM 30G transmits to the AMF 30A a response message (Namf_EventExposure Notify response) in response to the request message received in S303.

[0095] S305: The UDM 30G sends to the 6GAMF 30D a request message (Nudm_EventExposure Notify request) requesting a call to the terminal 20, which includes information indicating that alert information is being transmitted. The request message includes information about the area to which the alert information is to be distributed and information about the content of the alert information. For example, the request message is expressed as Nudm_EventExposure Notify_request (MonitoringReport(eventType(PWS request received), areaList(pwsInfo))).

[0096] S306: The 6GAMF 30D transmits to the UDM 30G a response message (Nudm_EventExposure Notify response) in response to the request message received in S305.

[0097] S307: The 6GAMF30D determines to send a short message using the paging channel to the terminal 20 to instruct it to receive PWS-related SIBs on the 5GS side.

[0098] S308: The 6GAMF 30D transmits a request message requesting transmission of a short message to the 6G base station 10B. The request message includes information indicating that warning information is being transmitted by 5GS.

[0099] S309: The 6G base station 10B transmits to the terminal 20 a short message including information indicating that warning information is being transmitted via 5GS.

[0100] S310: In response to the short message received in S309, the terminal 20 switches the standby state from 6GS (6G base station 10B) to 5GS (base station 10A).

[0101] S311: The base station 10A delivers a message including warning information. The message is delivered, for example, in SIB6, SIB7, SIB8, etc. in RRC.

[0102] S312: The terminal 20 receives the message including the warning information distributed from the base station 10A.

[0103] (Second Example) In the second example, when cooperation is performed between AMF30A and 6GAMF30D, a procedure for providing services other than voice call services by causing the system to fall back without using a special network node will be described.

[0104] (Short Message Service) An example of a short message service will now be described. Fig. 6 is a diagram showing an example of a fourth sequence diagram in an embodiment of the present invention. The processing of each step in Fig. 6 will now be described. Section 4.13.3.6 of Non-Patent Document 2 can be referred to for the procedure of existing specifications related to the reception of short messages (processing executed before S401, etc.).

[0105] S401: The SMSF 30L transmits to the AMF 30A a request message (Namf_MT_EnableUEReachability request) requesting notification of an SMS arrival at the terminal 20. The request message includes information indicating that the terminal 20 has an SMF arrival.

[0106] S402: It is assumed that AMF 30A has previously set information indicating that terminal 20 is in the 6GS area (6G area flag = 1) in its own device based on information received from 6GAMF 30D. Since the information (6G area flag = 1) is set, AMF 30A determines not to call terminal 20 on the 5GS side but to call terminal 20 on the 6GS side.

[0107] S403: Set information indicating that an SMS is being received in 5GS (5G SMS receiving flag = 1).

[0108] S404: The AMF 30A transmits to the 6GAMF 30D a request message (Namf_Association_Update request) requesting a call to the terminal 20. The request message includes information indicating that an SMS is being received in 5GS (5G SMS receiving flag = 1).

[0109] S405: The 6GAMF30D includes information indicating that the terminal 20 is receiving an SMS in 5GS (5G SMS receiving flag = 1) in the information stored in the device and registered in the UDM30G regarding the device.

[0110] S406: The 6GAMF 30D sends a response message (Namf_Association_Update response) to the request message received in S405 to the AMF 30A.

[0111] S407: Since the terminal 20 is receiving an SMS in the 5GS, the 6GAMF30D determines to have the terminal 20 execute a service request in the 5GS to respond to the SMS incoming call.

[0112] Steps S408 and S409 are processes executed when the terminal 20 is communicating in 6GS (connection mode).

[0113] S408: The 6GAMF 30D transmits to the 6G base station 10B a message (Downlink NAS Transport, see section 9.2.5.2 of Non-Patent Document 4) including a request for a response to an incoming SMS message in a system (5GS) other than the currently communicating system (6GS). The message includes information indicating that the wireless access type is a wireless system used in 5GS (RAT type=NR) and information indicating that the purpose of the message is to notify that an SMS message is incoming in 5GS. The message is expressed as, for example, Downlink NAS Transport(NAS-PDU(Notification(Access Type=3GPP access, RAT type=NR, Purpose=5G SMS incoming))) (see section 8.2.23.1 of Non-Patent Document 5, etc.).

[0114] S409: The 6G base station 10B transmits a message (DL Information Transfer) for transferring the information received in S408 to the terminal 20. This message is expressed as, for example, DL Information Transfer (dedicated NAS-Message (Notification (Access Type = 3GPP access, RAT type = NR, Purpose = 5G SMS incoming))).

[0115] S410 and S411 are processes executed when the terminal 20 is in the idle mode in 6GS.

[0116] S410: The 6GAMF 30D transmits to the 6G base station 10B a paging message (Paging) to call the terminal 20 in idle mode. The message includes a request for a response to an incoming SMS message in a system (5GS) other than the currently camped system (6GS), information indicating that the wireless access type is wireless used in 5GS (RAT type=NR), and information indicating that the purpose of the message is to notify that an SMS message is being received in 5GS.

[0117] S411: The 6G base station 10B transmits to the terminal 20 a paging message (Paging) generated from the message received in S410 to call the terminal 20 in idle mode.

[0118] S412: In response to the message received in S409 or S411, the terminal 20 determines to switch from 6GS to 5GS by an automatic response by the terminal 20 or by an operation by the user.

[0119] S413: Following S409, the procedures from S413 to S416 are executed. The terminal 20 transmits a message (UL Information Transfer) including information indicating switching to 5GS to the 6G base station 10B. This message is expressed as, for example, UL Information Transfer (dedicated NAS-Message (Notification response (switching to 5G))).

[0120] S414: The 6G base station 10B transmits to the 6GAMF 30D a message (Uplink NAS Transport) including information indicating switching to 5GS received in S413. This message is expressed as, for example, Uplink NAS Transport (NAS-PDU (Notification response (switching to 5G))).

[0121] S415: The 6GAMF30D decides to deactivate the 6G data communication PDU session, and processing related to the deactivation is performed.

[0122] S416: The 6GAMF30D erases the information indicating that an SMS is being received in 5GS and the information indicating that the terminal 20 is in the 6G area from the registration information for the UDM30G stored in the device itself.

[0123] From then on, processing after switching to 5GS will be carried out.

[0124] S421: The terminal 20 switches the connected system from 6GS to 5GS, and determines to execute a service request to receive SMS.

[0125] S422: The terminal 20 transmits a message (service request) requesting reception of an SMS to the base station 10A based on the procedure of the existing specifications.

[0126] S423: The base station 10A transmits the message (service request) received in S422 to the AMF 30A.

[0127] S424: Based on the existing procedure, the terminal 20 receives the incoming SMS.

[0128] S425: AMF 30A erases the information set in its own device regarding terminal 20 indicating that an SMS is being received in 5GS and the information indicating that it is in the 6G area.

[0129] (Location Information Acquisition Service) An example of a location information acquisition service will be described. FIG. 7 is a diagram showing an example of a fifth sequence diagram in an embodiment of the present invention. The processing of each step in FIG. 7 will be described below. Section 6.1.1 of Non-Patent Document 6 can be referred to for the procedure of existing specifications related to the location information acquisition service (processing executed before S501, etc.).

[0130] S501: The GMLC 30M transmits to the AMF 30A a request message (Namf_Location_ProvidePositioningInfo request) requesting acquisition of location information from the terminal 20. The request message includes information indicating that there is a request for acquisition of location information from the terminal 20.

[0131] S502: It is assumed that AMF 30A has previously set information indicating that terminal 20 is in the 6GS area (6G area flag = 1) in its own device based on information received from 6GAMF 30D. Since the information (6G area flag = 1) is set, AMF 30A determines not to call terminal 20 on the 5GS side but to call terminal 20 on the 6GS side.

[0132] S503: Set information (5G MT-LR flag = 1) indicating that a request to obtain location information is being received in 5GS.

[0133] S504: The AMF 30A transmits to the 6GAMF 30D a request message (Namf_Association_Update request) requesting a call to the terminal 20. The request message includes information indicating that a request to obtain location information is being received in the 5GS (5G MT-LR flag = 1).

[0134] S505: 6GAMF30D includes information indicating that terminal 20 is receiving a request to obtain location information in 5GS (5G MT-LR flag = 1) in the information stored in its own device and registered in UDM30G regarding its own device.

[0135] S506: The 6GAMF 30D sends a response message (Namf_Association_Update response) to the request message received in S405 to the AMF 30A.

[0136] S507: Since the terminal 20 is currently receiving a request to obtain location information at the 5GS, the 6GAMF30D decides to have the terminal 20 execute a service request at the 5GS in response to the request to obtain location information.

[0137] Steps S508 and S509 are processes executed when the terminal 20 is communicating in 6GS (connection mode).

[0138] S508: The 6GAMF 30D transmits to the 6G base station 10B a message (Downlink NAS Transport, see section 9.2.5.2 of Non-Patent Document 4) including a request for a response to a request for acquiring location information in a system (5GS) other than the system (6GS) currently in communication. The message includes information indicating that the wireless access type is a wireless system used in 5GS (RAT type=NR) and information indicating that the purpose of the message is to notify that a request for acquiring location information in 5GS is being received. The message is expressed as, for example, Downlink NAS Transport (NAS-PDU (Notification (Access Type=3GPP access, RAT type=NR, Purpose=5G MT-LR))) (see section 8.2.23.1 of Non-Patent Document 5, etc.).

[0139] S509: The 6G base station 10B transmits a message (DL Information Transfer) for transferring the information received in S508 to the terminal 20. This message is expressed as, for example, DL Information Transfer (dedicated NAS-Message (Notification (Access Type = 3GPP access, RAT type = NR, Purpose = 5G MT-LR))).

[0140] S510 and S511 are processes executed when the terminal 20 is in the idle mode in 6GS.

[0141] S510: The 6GAMF 30D transmits to the 6G base station 10B a paging message (Paging) to call the terminal 20 in idle mode. The message includes a request for a response to a request to acquire location information in a system (5GS) other than the currently camped system (6GS), information indicating that the wireless access type is wireless used in 5GS (RAT type=NR), and information indicating that the purpose of the message is to notify that a request to acquire location information in 5GS is being received.

[0142] S511: The 6G base station 10B transmits to the terminal 20 a paging message (Paging) generated from the message received in S510 to call the terminal 20 in idle mode.

[0143] S512: In response to the message received in S509 or S511, the terminal 20 determines to switch from 6GS to 5GS by an automatic response by the terminal 20 or by an operation by the user.

[0144] S513: Following S509, the procedures from S513 to S516 are executed. The terminal 20 transmits a message (UL Information Transfer) including information indicating switching to 5GS to the 6G base station 10B. This message is expressed as, for example, UL Information Transfer (dedicated NAS-Message (Notification response (switching to 5G))).

[0145] S514: The 6G base station 10B transmits to the 6GAMF 30D a message (Uplink NAS Transport) including information indicating switching to 5GS received in S513. This message is expressed as, for example, Uplink NAS Transport (NAS-PDU (Notification response (switching to 5G))).

[0146] S515: The 6GAMF30D decides to deactivate the 6G data communication PDU session, and processing related to the deactivation is performed.

[0147] S516: 6GAMF30D erases the information indicating that a request to obtain location information is being received in 5GS and the information indicating that the terminal 20 is in the 6G area from the registration information for UDM30G stored in its own device.

[0148] From then on, processing after switching to 5GS will be carried out.

[0149] S521: The terminal 20 switches the connected system from 6GS to 5GS, and determines to execute a service request to receive a request for obtaining location information.

[0150] S522: The terminal 20 transmits a message (service request) requesting acquisition of location information to the base station 10A based on the procedure of the existing specifications.

[0151] S523: The base station 10A transmits the message (service request) received in S522 to the AMF 30A.

[0152] S524: Based on the existing procedure, the terminal 20 receives a request to acquire location information.

[0153] S525: AMF30A erases the information set in its own device regarding terminal 20 indicating that it is receiving a request to obtain location information in 5GS and the information indicating that it is in the 6G area.

[0154] (Public Warning Service) An example of a public warning service will be described. Fig. 8 is a diagram showing an example of a sixth sequence diagram in an embodiment of the present invention. The processing of each step in Fig. 8 will be described below. Section 9.1.3.5.2 of Non-Patent Document 7 can be referred to for the procedure of existing specifications related to the public warning service (PWS transmission processing on the 5GS side, etc.).

[0155] S601: The CBC 30N transmits to the AMF 30A a request message (Namf_NonUeN2Message Transfer request) requesting transmission of warning information to the terminal 20. The request message is expressed as, for example, Namf_NonUeN2Message Transfer request (N2InformationTransferReqData (n2Information (Write-Replace Warning Request))).

[0156] S602: The AMF 30A determines to prompt the terminal 20 located in the 6GS area to move (camp) to the 5GS area in order to provide the terminal 20 with warning information.

[0157] S603: The AMF 30A transmits to the 6GAMF 30D a request message (Namf_EventExposure Notify request) requesting a call to the terminal 20 via 6GS, the request message including information indicating that alert information is being transmitted. The request message includes information regarding the area to which the alert information is distributed and information regarding the content of the alert information. For example, the request message is expressed as Namf_EventExposure Notify_request (AmfEventNotification(reportList(type(PWS request received), areaList (pwsInfo)))).

[0158] S604: The 6GAMF 30D sends a response message (Namf_EventExposure Notify response) to the request message received in S603 to the AMF 30A.

[0159] S605: The 6GAMF30D determines to send a short message using the paging channel to the terminal 20 to instruct it to receive PWS-related SIBs on the 5GS side.

[0160] S606: The 6GAMF 30D transmits a request message requesting transmission of a short message to the 6G base station 10B. The request message includes information indicating that warning information is being transmitted by 5GS.

[0161] S607: The 6G base station 10B transmits to the terminal 20 a short message including information indicating that warning information is being transmitted via 5GS.

[0162] S608: In response to the short message received in S607, the terminal 20 switches the standby state from 6GS (6G base station 10B) to 5GS (base station 10A).

[0163] S609: The base station 10A delivers a message including the warning information. The message is delivered by being included in, for example, SIB6, SIB7, and SIB8 in the RRC.

[0164] S610: The terminal 20 receives a message including warning information distributed from the base station 10A.

[0165] According to the above-described embodiment, in a wireless communication system, it is possible to provide services other than voice call services by performing a system fallback without using a special network node.

[0166] (Device Configuration) Next, a description will be given of an example of the functional configuration of the base station 10, network node 30, and terminal 20 that perform the processes and operations described above. The base station 10, network node 30, and terminal 20 include functions for performing the above-described embodiments. However, the base station 10, network node 30, and terminal 20 may each include only a part of the functions of the embodiments.

[0167] <Base Station 10 and Network Node 30> Fig. 9 is a diagram showing an example of the functional configuration of the base station 10 and the network node 30. As shown in Fig. 9, the base station 10 has a transmitting unit 110, a receiving unit 120, a setting unit 130, and a control unit 140. The functional configuration shown in Fig. 9 is merely an example. As long as the operations according to the embodiment of the present invention can be performed, the names of the functional divisions and functional units may be any. Note that the network node 30 may have the same functional configuration as the base station 10. Furthermore, a network node 30 having multiple different functions in the system architecture may be composed of multiple network nodes 30 separated by function.

[0168] The transmitter 110 includes a function of generating a signal to be transmitted to the terminal 20 or another network node 30 and transmitting the signal by wire or wirelessly. The receiver 120 includes a function of receiving various signals transmitted from the terminal 20 or another network node 30 and acquiring, for example, information of a higher layer from the received signal. A communication unit including the transmitter 110 and the receiver 120 may be configured.

[0169] The setting unit 130 stores preset setting information and various setting information to be transmitted to the terminal 20 in a storage device, and reads out the information from the storage device as needed.

[0170] The control unit 140 performs processing related to communication with the terminal 20. The function unit related to signal transmission in the control unit 140 may be included in the transmitting unit 110, and the function unit related to signal reception in the control unit 140 may be included in the receiving unit 120.

[0171] <Terminal 20> Fig. 10 is a diagram showing an example of the functional configuration of the terminal 20. As shown in Fig. 10, the terminal 20 has a transmitting unit 210, a receiving unit 220, a setting unit 230, and a control unit 240. The functional configuration shown in Fig. 10 is merely an example. As long as the operations related to the embodiment of the present invention can be performed, the names of the functional divisions and functional units may be any. In addition, the communication device that becomes the resource holder 20 may have the same functional configuration as the terminal 20.

[0172] The transmitter 210 creates a transmission signal from transmission data and transmits the transmission signal wirelessly. The receiver 220 receives various signals wirelessly and acquires higher layer signals from the received physical layer signals. The receiver 220 also has a function of receiving control signals, reference signals, etc. transmitted from the network node 30. A communication unit including the transmitter 210 and the receiver 220 may be configured.

[0173] The setting unit 230 stores various pieces of setting information received from the network node 30 by the receiving unit 220 in a storage device, and reads them out from the storage device as needed. The setting unit 230 also stores setting information that is set in advance.

[0174] The control unit 240 performs processing to enable mutual communication between the base station 10 and the network node 30. The function unit related to signal transmission in the control unit 240 may be included in the transmitting unit 210, and the function unit related to signal reception in the control unit 240 may be included in the receiving unit 220.

[0175] (Hardware Configuration) The block diagrams (FIGS. 9 and 10) used to explain the above embodiments show functional blocks. These functional blocks (components) are realized by any combination of at least one of hardware and software. Furthermore, the method for realizing each functional block is not particularly limited. That is, each functional block may be realized using a single device that is physically or logically coupled, or may be realized using two or more physically or logically separated devices that are directly or indirectly connected (for example, using wires, wirelessly, etc.) and these multiple devices. The functional block may be realized by combining software with the single device or the multiple devices.

[0176] Functions include, but are not limited to, judgment, determination, assessment, calculation, computation, processing, derivation, investigation, search, confirmation, reception, transmission, output, access, resolution, selection, selection, establishment, comparison, assumption, expectation, consideration, broadcasting, notifying, communicating, forwarding, configuring, reconfiguring, allocating, mapping, and assignment. For example, a functional block (component) that performs transmission is called a transmitting unit or transmitter. As mentioned above, there are no particular limitations on how these functions are implemented.

[0177] For example, the base station 10, the network node 30, the terminal 20, etc. according to an embodiment of the present disclosure may function as a computer that performs processing of the wireless communication method of the present disclosure. Fig. 11 is a diagram illustrating an example of the hardware configuration of the base station 10 and the terminal 20 according to an embodiment of the present disclosure. The network node 30 may have the same hardware configuration as the base station 10. The above-described base station 10 and the terminal 20 may be physically configured as a computer device including a processor 1001, a storage device 1002, an auxiliary storage device 1003, a communication device 1004, an input device 1005, an output device 1006, a bus 1007, etc.

[0178] In the following description, the term "apparatus" can be interpreted as a circuit, a device, a unit, etc. The hardware configuration of the base station 10 and the terminal 20 may be configured to include one or more of the apparatuses shown in the drawings, or may be configured to exclude some of the apparatuses.

[0179] Each function in the base station 10 and the terminal 20 is realized by loading specified software (programs) onto hardware such as the processor 1001, the memory device 1002, etc., so that the processor 1001 performs calculations, controls communication by the communication device 1004, and controls at least one of reading and writing data in the memory device 1002 and the auxiliary memory device 1003.

[0180] The processor 1001 controls the entire computer by running, for example, an operating system. The processor 1001 may be configured as a central processing unit (CPU) including an interface with peripheral devices, a control device, an arithmetic unit, a register, etc. For example, the above-mentioned control unit 140, control unit 240, etc. may be realized by the processor 1001.

[0181] Furthermore, the processor 1001 reads programs (program codes), software modules, data, etc. from at least one of the auxiliary storage device 1003 and the communication device 1004 into the storage device 1002 and executes various processes in accordance with the programs. The programs used are those that cause a computer to execute at least some of the operations described in the above-described embodiments. For example, the control unit 140 of the base station 10 shown in FIG. 9 may be implemented by a control program stored in the storage device 1002 and running on the processor 1001. Furthermore, for example, the control unit 240 of the terminal 20 shown in FIG. 10 may be implemented by a control program stored in the storage device 1002 and running on the processor 1001. While the above-described various processes have been described as being executed by one processor 1001, they may also be executed simultaneously or sequentially by two or more processors 1001. The processor 1001 may be implemented by one or more chips. The programs may also be transmitted from a network via a telecommunications line.

[0182] The storage device 1002 is a computer-readable recording medium and may be configured, for example, by at least one of a read-only memory (ROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), a random access memory (RAM), etc. The storage device 1002 may also be called a register, a cache, a main memory, etc. The storage device 1002 can store executable programs (program codes), software modules, etc. for implementing a communication method according to an embodiment of the present disclosure.

[0183] The secondary storage device 1003 is a computer-readable recording medium, and may be, for example, at least one of an optical disk such as a CD-ROM (Compact Disc ROM), a hard disk drive, a flexible disk, a magneto-optical disk (e.g., a compact disk, a digital versatile disk, a Blu-ray (registered trademark) disk), a smart card, a flash memory (e.g., a card, a stick, a key drive), a floppy (registered trademark) disk, a magnetic strip, etc. The above-mentioned storage medium may be, for example, a database, a server, or other appropriate medium including at least one of the storage device 1002 and the secondary storage device 1003.

[0184] The communication device 1004 is hardware (transmission / reception device) for communicating between computers via at least one of a wired network and a wireless network, and is also referred to as, for example, a network device, a network controller, a network card, a communication module, etc. The communication device 1004 may be configured to include a high-frequency switch, a duplexer, a filter, a frequency synthesizer, etc. to realize at least one of frequency division duplex (FDD) and time division duplex (TDD). For example, a transmission / reception antenna, an amplifier unit, a transmission / reception unit, a transmission path interface, etc. may be realized by the communication device 1004. The transmission / reception unit may be implemented as a transmission unit and a reception unit that are physically or logically separated.

[0185] The input device 1005 is an input device (e.g., a keyboard, a mouse, a microphone, a switch, a button, a sensor, etc.) that receives input from the outside. The output device 1006 is an output device (e.g., a display, a speaker, an LED lamp, etc.) that outputs to the outside. Note that the input device 1005 and the output device 1006 may be integrated into one device (e.g., a touch panel).

[0186] Furthermore, each device such as the processor 1001 and the storage device 1002 is connected by a bus 1007 for communicating information. The bus 1007 may be configured using a single bus, or may be configured using different buses between each device.

[0187] Furthermore, the base station 10 and the terminal 20 may be configured to include hardware such as a microprocessor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a programmable logic device (PLD), or a field programmable gate array (FPGA), and some or all of the functional blocks may be realized by the hardware. For example, the processor 1001 may be implemented using at least one of these pieces of hardware.

[0188] Fig. 12 shows an example configuration of a vehicle 2001. As shown in Fig. 12, the vehicle 2001 includes a drive unit 2002, a steering unit 2003, an accelerator pedal 2004, a brake pedal 2005, a shift lever 2006, front wheels 2007, rear wheels 2008, an axle 2009, an electronic control unit 2010, various sensors 2021 to 2029, an information service unit 2012, and a communication module 2013. Each aspect / embodiment described in the present disclosure may be applied to a communication device mounted on the vehicle 2001, and may be applied to the communication module 2013, for example.

[0189] The drive unit 2002 is configured, for example, by an engine, a motor, or a hybrid of an engine and a motor. The steering unit 2003 includes at least a steering wheel (also called a handle) and is configured to steer at least one of the front wheels and the rear wheels based on the operation of the steering wheel operated by the user.

[0190] The electronic control unit 2010 is composed of a microprocessor 2031, a memory (ROM, RAM) 2032, and a communication port (IO port) 2033. Signals are input to the electronic control unit 2010 from various sensors 2021 to 2029 provided in the vehicle 2001. The electronic control unit 2010 may also be called an ECU (Electronic Control Unit).

[0191] The signals from the various sensors 2021 to 2029 include a current signal from a current sensor 2021 that senses the current of the motor, a rotation speed signal of the front and rear wheels obtained by a rotation speed sensor 2022, an air pressure signal of the front and rear wheels obtained by an air pressure sensor 2023, a vehicle speed signal obtained by a vehicle speed sensor 2024, an acceleration signal obtained by an acceleration sensor 2025, an accelerator pedal depression amount signal obtained by an accelerator pedal sensor 2029, a brake pedal depression amount signal obtained by a brake pedal sensor 2026, a shift lever operation signal obtained by a shift lever sensor 2027, and a detection signal for detecting obstacles, vehicles, pedestrians, etc. obtained by an object detection sensor 2028.

[0192] The information service unit 2012 is composed of various devices, such as a car navigation system, an audio system, speakers, a television, and a radio, for providing (outputting) various types of information, such as driving information, traffic information, and entertainment information, and one or more ECUs for controlling these devices. The information service unit 2012 uses information acquired from external devices via the communication module 2013 or the like to provide various types of multimedia information and multimedia services to the occupants of the vehicle 2001. The information service unit 2012 may include input devices (e.g., a keyboard, a mouse, a microphone, a switch, a button, a sensor, a touch panel, etc.) that accept input from the outside, and may also include output devices (e.g., a display, a speaker, an LED lamp, a touch panel, etc.) that output information to the outside.

[0193] The driving assistance system unit 2030 is composed of various devices that provide functions for preventing accidents and reducing the driving burden on the driver, such as millimeter-wave radar, LiDAR (Light Detection and Ranging), cameras, positioning locators (e.g., GNSS, etc.), map information (e.g., high-definition (HD) maps, autonomous vehicle (AV) maps, etc.), gyro systems (e.g., IMU (Inertial Measurement Unit), INS (Inertial Navigation System), etc.), AI (Artificial Intelligence) chips, and AI processors, as well as one or more ECUs that control these devices. In addition, the driving assistance system unit 2030 transmits and receives various information via the communication module 2013 to realize the driving assistance function or the autonomous driving function.

[0194] The communication module 2013 can communicate with the microprocessor 2031 and components of the vehicle 2001 via the communication port. For example, the communication module 2013 transmits and receives data via the communication port 2033 to and from the drive unit 2002, steering unit 2003, accelerator pedal 2004, brake pedal 2005, shift lever 2006, front wheels 2007, rear wheels 2008, axle 2009, microprocessor 2031 and memory (ROM, RAM) 2032 in the electronic control unit 2010, and sensors 2021 to 29, which are provided in the vehicle 2001.

[0195] The communication module 2013 is a communication device that can be controlled by the microprocessor 2031 of the electronic control unit 2010 and can communicate with an external device. For example, it transmits and receives various information to and from the external device via wireless communication. The communication module 2013 may be located either inside or outside the electronic control unit 2010. The external device may be, for example, a base station, a mobile station, or the like.

[0196] The communication module 2013 may transmit at least one of signals from the above-mentioned various sensors 2021-2028 input to the electronic control unit 2010, information obtained based on the signals, and information based on input from the outside (user) obtained via the information service unit 2012 to an external device via wireless communication. The electronic control unit 2010, the various sensors 2021-2028, the information service unit 2012, etc. may be referred to as input units that accept input. For example, the PUSCH transmitted by the communication module 2013 may include information based on the above-mentioned input.

[0197] The communication module 2013 receives various information (traffic information, traffic signal information, vehicle-to-vehicle information, etc.) transmitted from external devices and displays it on an information service unit 2012 provided in the vehicle 2001. The information service unit 2012 may be called an output unit that outputs information (for example, outputs information to a device such as a display or speaker based on the PDSCH (or data / information decoded from the PDSCH) received by the communication module 2013). The communication module 2013 also stores the various information received from external devices in a memory 2032 that can be used by the microprocessor 2031. Based on the information stored in the memory 2032, the microprocessor 2031 may control the drive unit 2002, steering unit 2003, accelerator pedal 2004, brake pedal 2005, shift lever 2006, front wheels 2007, rear wheels 2008, axles 2009, sensors 2021 to 2029, etc. provided in the vehicle 2001.

[0198] <Additional Notes> (Additional Item 1) A network node in a first communication system, comprising: a receiving unit that receives, from the first network node, a first message including information indicating that a terminal is within the service area of ​​a second communication system, and a second message that receives, from a second network node, a second message including information indicating an incoming short message service call to the terminal, and a transmitting unit that transmits, to the first network node, a third message requesting a call to the terminal, the third message including the information indicating the incoming call and an instruction to respond in the first communication system. (Additional Item 2) A network node in a first communication system, comprising: a receiving unit that receives, from the first network node, a first message including information indicating that a terminal is within the service area of ​​a second communication system, and a second message from the second network node including information indicating a request to acquire location information for the terminal, and a transmitting unit that transmits, to the first network node, a third message requesting a call to the terminal, the third message including information indicating the acquisition request and an instruction to respond in the first communication system. (Supplementary Item 3) A network node in a first communication system, comprising: a receiving unit that receives, from the first network node, a first message requesting transmission of alarm information, and a transmitting unit that transmits, to a second network node, a second message requesting a call to a terminal in a second communication system, the second message including information indicating that alarm information is being transmitted in the first communication system. (Supplementary Item 4) A network node comprising: a receiving unit that receives, from the first network node, a first message requesting a call to a terminal in a second communication system, the second message including information indicating that alarm information is being transmitted in the first communication system, and a transmitting unit that transmits the second message requesting the call to a base station in the second communication system.(Supplementary Item 5) A terminal comprising: a receiver that receives, from a first base station, a first message requesting a call to the terminal, the first message including information indicating that alert information is being transmitted in a first communication system; and a control unit that switches from a second communication system to standby in the first communication system, wherein the receiver receives a second message including the alert information from a second base station in the second communication system. (Supplementary Item 6) A communication method executed by a network node in a first communication system, the method comprising: receiving, from the first network node, a first message including information indicating that the terminal is within the range of the second communication system; receiving, from the second network node, a second message including information indicating an incoming call of a short message service to the terminal; and transmitting, to the first network node, a third message requesting a call to the terminal, the third message including information indicating the incoming call and an instruction to respond in the first communication system.

[0199] Any of Supplementary Items 1 to 6 makes it possible to enable fallback of a system in a wireless communication system without using a special network node.

[0200] (Supplementary Notes on the Embodiments) Although the embodiments of the present invention have been described above, the disclosed invention is not limited to such embodiments, and those skilled in the art will understand various modifications, alterations, alternatives, and substitutions. While specific numerical examples have been used to facilitate understanding of the invention, unless otherwise specified, these numerical values ​​are merely examples, and any appropriate values ​​may be used. The division of items in the above description is not essential to the present invention; matters described in two or more items may be used in combination as needed, and matters described in one item may apply to matters described in another item (as long as there is no contradiction). Boundaries between functional units or processing units in functional block diagrams do not necessarily correspond to boundaries between physical components. The operations of multiple functional units may be performed by a single physical component, or the operations of a single functional unit may be performed by multiple physical components. The order of processing steps described in the embodiments may be reversed as long as there is no contradiction. For convenience of processing description, the base station 10 and terminal 20 have been described using functional block diagrams, but such devices may be realized by hardware, software, or a combination thereof. The software operated by the processor of the base station 10 in accordance with an embodiment of the present invention and the software operated by the processor of the terminal 20 in accordance with an embodiment of the present invention may each be stored in random access memory (RAM), flash memory, read-only memory (ROM), EPROM, EEPROM, register, hard disk (HDD), removable disk, CD-ROM, database, server, or any other suitable storage medium.

[0201] Furthermore, the notification of information is not limited to the aspects / embodiments described in the present disclosure, and may be performed using other methods. For example, the notification of information may be performed by physical layer signaling (e.g., Downlink Control Information (DCI), Uplink Control Information (UCI)), higher layer signaling (e.g., Radio Resource Control (RRC) signaling, Medium Access Control (MAC) signaling), broadcast information (Master Information Block (MIB), System Information Block (SIB)), other signals, or a combination thereof. Furthermore, the RRC signaling may be referred to as an RRC message, and may be, for example, an RRC Connection Setup message, an RRC Connection Reconfiguration message, or the like.

[0202] Each aspect / embodiment described in the present disclosure may be implemented using any of the following standards: LTE (Long Term Evolution), LTE-Advanced (LTE-A), SUPER 3G, IMT-Advanced, 4G (4th generation mobile communication system), 5G (5th generation mobile communication system), 6th generation mobile communication system (6G), xth generation mobile communication system (xG) (xG (x is, for example, an integer or a decimal number)), FRA (Future Radio Access), NR (new Radio), New radio access (NX), Future generation radio access (FX), W-CDMA (registered trademark), GSM (registered trademark), CDMA2000, UMB (Ultra Mobile Broadband), IEEE 802.11 (Wi-Fi (registered trademark)), IEEE 802.16 (WiMAX (registered trademark)), IEEE 802.17 (WiMAX (registered trademark)), IEEE 802.19 (WiMAX (registered trademark)), IEEE 802.20 (WiMAX (registered trademark)), IEEE 802.21 (Wi-Fi (registered trademark)), IEEE 802.22 (WiMAX (registered trademark)), IEEE 802.23 (WiMAX (registered trademark)), IEEE 802.24 (WiMAX (registered trademark)), IEEE 802.25 (WiMAX (registered trademark)), IEEE 802.26 (WiMAX (registered trademark)), IEEE 802.27 (WiMAX (registered trademark)), IEEE 802.28 (WiMAX (registered trademark)), IEEE 802.29 (WiMAX (registered trademark)), IEEE 802.30 (WiMAX (registered trademark)), IEEE 802.31 (Wi-Fi (registered trademark)), IEEE 802.32 (WiMAX (registered trademark)), IEEE 802.33 (WiMAX (registered trademark)), IEEE 802.34 ( The present invention may be applied to at least one of systems using 802.20, UWB (Ultra-Wide Band), Bluetooth (registered trademark), or other suitable systems, and next-generation systems that are extended, modified, created, or defined based on these systems. The present invention may also be applied to a combination of multiple systems (e.g., a combination of LTE and / or LTE-A with 5G).

[0203] The order of the procedures, sequences, flowcharts, etc. of each aspect / embodiment described herein may be rearranged unless it is consistent. For example, the methods described in this disclosure present elements of various steps using an example order and are not limited to the particular order presented.

[0204] In this specification, a specific operation described as being performed by the base station 10 may be performed by its upper node in some cases. In a network consisting of one or more network nodes having the base station 10, it is clear that various operations performed for communication with the terminal 20 may be performed by at least one of the base station 10 and another network node other than the base station 10 (such as, but not limited to, an MME or an S-GW). Although the above example illustrates a case where there is one other network node other than the base station 10, the other network node may be a combination of multiple other network nodes (such as an MME and an S-GW).

[0205] The information, signals, etc. described in the present disclosure may be output from a higher layer (or a lower layer) to a lower layer (or a higher layer), or may be input / output via multiple network nodes.

[0206] Input and output information may be stored in a specific location (for example, memory) or may be managed using a management table. Input and output information may be overwritten, updated, or added to. Output information may be deleted. Input information may be sent to another device.

[0207] In the present disclosure, the determination may be made based on a value represented by one bit (0 or 1), a Boolean value (true or false), or a numerical comparison (e.g., comparison with a predetermined value).

[0208] Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

[0209] Software, instructions, information, etc. may also be transmitted or received over a transmission medium. For example, if software is transmitted from a website, server, or other remote source using wired technologies (such as coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL)), and / or wireless technologies (such as infrared, microwave), then these wired and / or wireless technologies are included within the definition of transmission media.

[0210] The information, signals, etc. described in this disclosure may be represented using any of a variety of different technologies. For example, data, instructions, commands, information, signals, bits, symbols, chips, etc. that may be referred to throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, optical fields or photons, or any combination thereof.

[0211] Note that terms described in this disclosure and terms necessary for understanding this disclosure may be replaced with terms having the same or similar meanings. For example, at least one of a channel and a symbol may be a signal (signaling). Furthermore, a signal may be a message. Furthermore, a component carrier (CC) may be called a carrier frequency, a cell, a frequency carrier, etc.

[0212] As used in this disclosure, the terms "system" and "network" are used interchangeably.

[0213] Furthermore, the information, parameters, etc. described in the present disclosure may be expressed using absolute values, may be expressed using relative values ​​from a predetermined value, or may be expressed using other corresponding information. For example, a radio resource may be indicated by an index.

[0214] The names used for the above-described parameters are not intended to be limiting in any way. Furthermore, the mathematical expressions using these parameters may differ from those explicitly disclosed in this disclosure. The various channels (e.g., PUCCH, PDCCH, etc.) and information elements may be identified by any suitable names, and therefore the various names assigned to these various channels and information elements are not intended to be limiting in any way.

[0215] In the present disclosure, terms such as "base station (BS)," "radio base station," "base station device," "fixed station," "NodeB," "eNodeB (eNB)," "gNodeB (gNB)," "access point," "transmission point," "reception point," "transmission / reception point," "cell," "sector," "cell group," "carrier," and "component carrier" may be used interchangeably. A base station may also be referred to by terms such as a macrocell, a small cell, a femtocell, and a picocell.

[0216] A base station can accommodate one or more (e.g., three) cells. When a base station accommodates multiple cells, the overall coverage area of ​​the base station can be partitioned into multiple smaller areas, and each smaller area can also be provided with communication services by a base station subsystem (e.g., a small indoor base station (RRH: Remote Radio Head)). The terms "cell" or "sector" refer to part or all of the coverage area of ​​a base station and / or base station subsystem that provides communication services within that coverage.

[0217] In the present disclosure, the base station transmitting information to a terminal may be interpreted as the base station instructing the terminal to control or operate based on the information.

[0218] In this disclosure, the terms "Mobile Station (MS)," "user terminal," "User Equipment (UE)," "terminal," and the like may be used interchangeably.

[0219] A mobile station may also be referred to by those skilled in the art as a subscriber station, mobile unit, subscriber unit, wireless unit, remote unit, mobile device, wireless device, wireless communication device, remote device, mobile subscriber station, access terminal, mobile terminal, wireless terminal, remote terminal, handset, user agent, mobile client, client, or some other suitable terminology.

[0220] At least one of the base station and the mobile station may be referred to as a transmitting device, a receiving device, a communication device, etc. At least one of the base station and the mobile station may be a device mounted on a mobile object, the mobile object itself, etc. The mobile object refers to a movable object, and may move at any speed. Naturally, this also includes cases where the mobile object is stationary. Examples of the mobile object include, but are not limited to, vehicles, transport vehicles, automobiles, motorcycles, bicycles, connected cars, excavators, bulldozers, wheel loaders, dump trucks, forklifts, trains, buses, handcars, rickshaws, ships and other watercraft, airplanes, rockets, satellites, drones (registered trademark), multicopters, quadcopters, balloons, and objects mounted thereon. The mobile object may also be a mobile object that moves autonomously based on an operational command. It may be a vehicle (e.g., a car, an airplane, etc.), an unmanned mobile object (e.g., a drone, an autonomous vehicle, etc.), or a robot (manned or unmanned). At least one of the base station and the mobile station may be a device that does not necessarily move during communication operations. For example, at least one of the base station and the mobile station may be an IoT (Internet of Things) device such as a sensor.

[0221] Furthermore, a base station in the present disclosure may be read as a user terminal. For example, the aspects / embodiments of the present disclosure may be applied to a configuration in which communication between a base station and a user terminal is replaced with communication between multiple terminals 20 (which may be called, for example, Device-to-Device (D2D) or Vehicle-to-Everything (V2X)). In this case, the terminal 20 may be configured to have the functions of the base station 10 described above. Furthermore, terms such as "uplink" and "downlink" may be read as terms corresponding to terminal-to-terminal communication (for example, "side"). For example, terms such as an uplink channel and a downlink channel may be read as a side channel.

[0222] Similarly, the user terminal in the present disclosure may be read as a base station, in which case the base station may be configured to have the functions of the user terminal described above.

[0223] As used in this disclosure, the terms "determining" and "determining" may encompass a wide variety of actions. "Determining" and "determining" may include, for example, judging, calculating, computing, processing, deriving, investigating, looking up, searching, inquiring (e.g., searching in a table, database, or other data structure), ascertaining, and the like. "Determining" and "determining" may also include receiving (e.g., receiving information), transmitting (e.g., sending information), input, output, accessing (e.g., accessing data in memory), and the like. Furthermore, "judgment" and "decision" can include regarding resolving, selecting, choosing, establishing, comparing, etc. as having been "judged" or "decided." In other words, "judgment" and "decision" can include regarding some action as having been "judged" or "decided." Furthermore, "judgment (decision)" can be interpreted as "assuming," "expecting," "considering," etc.

[0224] The terms "connected," "coupled," or any variation thereof, refer to any direct or indirect connection or coupling between two or more elements, and may include the presence of one or more intermediate elements between two elements that are "connected" or "coupled" to each other. The coupling or connection between elements may be physical, logical, or a combination thereof. For example, "connected" may be read as "access." As used in this disclosure, two elements may be considered to be "connected" or "coupled" to each other using one or more wires, cables, and / or printed electrical connections, as well as electromagnetic energy having wavelengths in the radio frequency range, microwave range, and optical (both visible and invisible) range, as some non-limiting and non-exhaustive examples.

[0225] The reference signal may be abbreviated as RS (Reference Signal) or may be called a pilot depending on the applicable standard.

[0226] As used in this disclosure, the phrase "based on" does not mean "based only on," unless expressly stated otherwise. In other words, the phrase "based on" means both "based only on" and "based at least on."

[0227] As used in this disclosure, any reference to an element using a designation such as "first," "second," etc. does not generally limit the quantity or order of those elements. These designations may be used in this disclosure as a convenient method of distinguishing between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed or that the first element must in some way precede the second element.

[0228] The "means" in the configuration of each of the above devices may be replaced with "part," "circuit," "device," etc.

[0229] When the terms "include," "including," and variations thereof are used in this disclosure, these terms are intended to be inclusive, similar to the term "comprising." Furthermore, when the term "or" is used in this disclosure, it is not intended to be an exclusive or.

[0230] In this disclosure, where articles are added by translation, such as a, an, and the in English, the disclosure may include that the nouns following these articles are in the plural form.

[0231] In the present disclosure, the term "A and B are different" may mean "A and B are different from each other." The term may also mean "A and B are each different from C." Terms such as "separate" and "coupled" may also be interpreted in the same way as "different."

[0232] The aspects / embodiments described in this disclosure may be used alone, in combination, or switched depending on the implementation. Notification of predetermined information (e.g., notification that "X is true") is not limited to explicit notification, but may be implicit (e.g., not notifying the predetermined information).

[0233] Although the present disclosure has been described in detail above, it is clear to those skilled in the art that the present disclosure is not limited to the embodiments described herein. The present disclosure can be implemented in modified and altered forms without departing from the spirit and scope of the present disclosure as defined by the claims. Therefore, the description of the present disclosure is intended to be illustrative and does not have any limiting meaning on the present disclosure.

[0234] 10 Base station 110 Transmitter 120 Receiver 130 Setting unit 140 Control unit 20 Terminal 210 Transmitter 220 Receiver 230 Setting unit 240 Control unit 30 Network node 1001 Processor 1002 Storage device 1003 Auxiliary storage device 1004 Communication device 1005 Input device 1006 Output device 2001 Vehicle 2002 Drive unit 2003 Steering unit 2004 Accelerator pedal 2005 Brake pedal 2006 Shift lever 2007 Front wheels 2008 Rear wheels 2009 Axle 2010 Electronic control unit 2012 Information service unit 2013 Communication module 2021 Current sensor 2022 RPM sensor 2023 Tire pressure sensor 2024 Vehicle speed sensor 2025 Acceleration sensor 2026 Brake pedal sensor 2027 Shift lever sensor 2028 Object detection sensor 2029 Accelerator pedal sensor 2030 Driving assistance system unit 2031 Microprocessor 2032 Memory (ROM, RAM) 2033 Communication port (IO port)

Claims

1. A network node in a first communication system, comprising: a receiving unit that receives from the first network node a first message including information indicating that a terminal is within the range of a second communication system; and a second message that receives from the second network node a second message including information indicating an incoming short message service call to the terminal; and a transmitting unit that transmits to the first network node a third message requesting a call to the terminal, the third message including information indicating the incoming call and an instruction to respond in the first communication system.

2. A network node in a first communication system, comprising: a receiving unit that receives from the first network node a first message including information indicating that a terminal is within the range of a second communication system; and a second message that receives from the second network node a second message including information indicating a request for obtaining location information from the terminal; and a transmitting unit that transmits to the first network node a third message requesting a call to the terminal, the third message including information indicating the request and an instruction to respond in the first communication system.

3. A network node in a first communication system, comprising: a receiving unit that receives a first message from the first network node requesting the transmission of alarm information; and a transmitting unit that transmits to a second network node a second message requesting a call to a terminal in the second communication system, the second message including information indicating that alarm information is being transmitted in the first communication system.

4. A network node having: a receiving unit that receives, from a first network node, a first message requesting a call to a terminal in a second communication system, the first message including information indicating that alert information is being transmitted in a first communication system; and a transmitting unit that transmits, to a base station in the second communication system, a second message requesting the call.

5. A terminal comprising: a receiving unit that receives a first message from a first base station requesting a call to the terminal, the first message including information indicating that alert information is being transmitted in a first communication system; and a control unit that switches from a second communication system to standby in the first communication system, wherein the receiving unit receives a second message including alert information from a second base station in the second communication system.

6. A communication method executed by a network node in a first communication system, comprising: receiving from the first network node a first message including information indicating that a terminal is within the range of a second communication system; receiving from the second network node a second message including information indicating an incoming short message service call to the terminal; and transmitting to the first network node a third message requesting a call to the terminal, the third message including information indicating the incoming call and an instruction to respond in the first communication system.

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