Terminal device, wireless communication system, and relay method

Abstract

A relay device (110 #) is provided with: a terminal-side communication unit (111 #) that relays communication by a UE (110) to a first network that cannot use an emergency call service but supports the fallback of the emergency call service or a second network that is a fallback destination of the emergency call service; and a protocol processing unit (113 #) that, when the communication of the UE (110) is relayed to the first network, switches the communication of the UE (110) to the second network when a connection request to an emergency call service is received from the UE (110).

Description

Technical Field

[0001] The present disclosure relates to a terminal device, a wireless communication system, and a relay method. Background Art

[0002] In 3GPP (3rd Generation Partnership Project), which is a standardization organization for mobile communication systems, research is being conducted on supporting services or applications using SL (Side Link) communication (also known as PC5 communication) in EPS (Evolved Packet System) and in the 5G core system of the 5th generation (hereinafter also referred to as "5G") wireless access system. In SL communication, communication is performed between terminals. As services using SL communication, for example, there are V2X (Vehicle-to-everything) services and proximity services. In SL communication, not only direct communication between terminals is proposed, but also communication between a mobile terminal device (hereinafter, UE: User Equipment) and a NW (NetWork) via a repeater is proposed (for example, refer to Non-Patent Document 1). In addition, hereinafter, a UE that performs relay between a UE and a NW may sometimes be referred to as a U2N repeater.

[0003] Here, 3GPP is a registered trademark.

[0004] In 3GPP, in order to expand the coverage area of a cell using side link communication, the following functions of a U2N repeater are defined: providing a relay connection to an E-UTRAN (Evolved Universal Terrestrial Radio Access Network) or a 5G network to other terminals located outside the coverage area of the cell via side link communication.

[0005] Prior Art Documents

[0006] Non-Patent Documents

[0007] Non-Patent Document 1: 3GPP TR 38.836 V17.0.0 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] However, although emergency call services are specified in LTE (Long Term Evolution) and 5G, there is no disclosure in the current U2N repeater standard regarding the mechanism for switching to an E-UTRAN or 5G network that supports emergency call services through fallback when using emergency call services.

[0010] Therefore, one of the objectives of one or more aspects of the present disclosure is to enable communication using emergency call services between a base station and a network that does not support emergency call services but supports fallback for emergency call services and a terminal device via a U2N repeater.

[0011] Means for Solving the Problem

[0012] The terminal device according to the first aspect of the present disclosure is characterized in that the terminal device includes: a communication unit that relays the communication of a relay target device, which is another terminal device, to a first network or a second network, where the first network cannot utilize emergency call services but supports fallback for the emergency call services, and the second network is the fallback destination for the emergency call services; and a protocol processing unit that, when relaying the communication of the relay target device to the first network, switches the communication of the relay target device to the second network when receiving a connection request to the emergency call services from the relay target device.

[0013] The terminal device according to the second aspect of the present disclosure is characterized in that it includes: a communication unit that, when the network to which a relay device, which is another terminal device for relaying, is connected can utilize emergency call services, receives a relay discovery request message or a relay discovery response message including information indicating that the emergency call services can be provided, and when the network to which the relay device is connected cannot utilize the emergency call services but can perform fallback for the emergency call services, receives a relay discovery request message or a relay discovery response message including information indicating that a switch is required to utilize the emergency call services; and a protocol processing unit that, when the network to which the relay device is connected can provide the emergency call services, accepts relaying to the network to which the relay device is connected and thereby accepts the provision of the emergency call services, and when the network to which the relay device is connected can perform fallback for the emergency call services, accepts relaying to another network through fallback for the emergency call services and thereby accepts the provision of the emergency call services.

[0014] A wireless communication system according to an aspect of the present disclosure is characterized in that the wireless communication system includes: a first base station included in a first network that cannot utilize an emergency call service but supports fallback of the emergency call service; a second base station included in a second network that is a fallback destination of the emergency call service; and a terminal device that relays to the first base station and the second base station. The terminal device includes: a communication unit that relays communication of a relay target device that is another terminal device to the first base station or the second base station; and a protocol processing unit that, when relaying the communication of the relay target device to the first base station, switches the communication of the relay target device to the second base station when a connection request to the emergency call service is received from the relay target device via the communication unit.

[0015] A relay method according to a first aspect of the present disclosure is characterized in that, when relaying communication of a relay target device to a first network that cannot utilize an emergency call service but supports fallback of the emergency call service, a connection request to the emergency call service is received from the relay target device, and the communication of the relay target device is switched to a second network that is a fallback destination of the emergency call service.

[0016] A relay method according to a second aspect of the present disclosure is characterized in that, when an emergency call service can be utilized in a network to which a relay device that is another terminal device for relaying is connected, a relay discovery request message or a relay discovery response message including information indicating that the emergency call service can be provided is received. When the emergency call service cannot be utilized in the network to which the relay device is connected but fallback of the emergency call service can be performed, a relay discovery request message or a relay discovery response message including information indicating that a switch is required to utilize the emergency call service is received. When the emergency call service can be provided in the network to which the relay device is connected, relay to the network to which the relay device is connected is accepted, and thus provision of the emergency call service is accepted. When fallback of the emergency call service can be performed in the network to which the relay device is connected, relay to another network is accepted through fallback of the emergency call service, and thus provision of the emergency call service is accepted.

[0017] Effects of the Invention

[0018] According to one or more aspects of the present disclosure, communication using an emergency call service can be achieved between a base station and a network that do not support the emergency call service but support fallback of the emergency call service and a terminal device via a U2N repeater. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1is a block diagram schematically showing the configuration of the wireless communication system of Embodiment 1.

[0020] Figure 2 is a block diagram schematically showing the configuration of the UE.

[0021] Figure 3 (A) and (B) thereof are block diagrams showing hardware configuration examples.

[0022] Figure 4 is a block diagram schematically showing the configuration of the base station.

[0023] Figure 5 is a block diagram schematically showing the configuration of the 5GC upper device.

[0024] Figure 6 is a block diagram schematically showing the configuration of the EPC upper device.

[0025] Figure 7 is a timing diagram showing the steps for implementing the emergency call service in Embodiment 1.

[0026] Figure 8 is a block diagram schematically showing the configuration of the wireless communication system of Embodiment 2.

[0027] Figure 9 is a timing diagram showing the steps for implementing the emergency call service in Embodiment 2. Detailed Embodiment

[0028] Embodiment 1.

[0029] Figure 1 is a block diagram schematically showing the configuration of the wireless communication system 100 of Embodiment 1.

[0030] The wireless communication system 100 includes a UE 110 as a terminal device, a relay device 110#, an NG-RAN base station 130A which is a base station corresponding to NG-RAN (Next Generation Radio Access Network), a 5GC upper device 150 which is an upper device corresponding to 5GC (5 Generation Core), an E-UTRAN base station 130B which is a base station corresponding to E-UTRAN, and an EPC upper device 170 which is an upper device corresponding to EPC (Evolved Packet Core).

[0031] The wireless communication system 100 is a system for receiving the provision of emergency call services from a PSAP (Public Safety Answering Point) 191 via an IMS (Internet Protocol Multimedia Subsystem) 190.

[0032] Here, the relay device 110# is a U2N repeater.

[0033] In addition, the NG-RAN base station 130A and the 5GC upper device 150 do not support emergency call services, but are connected to the emergency call services via the EPC upper device 170 that supports emergency call services.

[0034] Embodiment 1 shows an example of fallback that supports emergency call services in the above structure.

[0035] The UE 110 can perform wireless communication with the NG-RAN base station 130A and the E-UTRAN base station 130B, and transmit and receive signals through wireless communication. In addition, through SL communication, the UE 110 can also perform communication between UEs 110, and can also perform communication via the relay device 110#. The UE 110 that receives relay through the relay device 110# is also referred to as a relay target device.

[0036] The NG-RAN base station 130A constitutes a radio access network.

[0037] When the radio access network is a 5G mode discussed in 3GPP, this radio access network is called NG-RAN. In this case, the NG-RAN base station 130A is called a gNB (NG-RAN NodeB). The core network is called 5G Core.

[0038] The E-UTRAN base station 130B constitutes a radio access network.

[0039] When the radio access network is an LTE mode discussed in 3GPP, this radio access network is called E-UTRAN. In this case, the E-UTRAN base station 130B is called an eNB (E-UTRAN NodeB).

[0040] Figure 2 It is a block diagram schematically showing the structure of the UE 110.

[0041] The UE 110 includes a terminal-side communication unit 111, an application unit (hereinafter referred to as the AP unit) 112, a protocol processing unit 113, and a control unit 114.

[0042] First, the transmission process of UE110 will be described.

[0043] The control data from the protocol processing unit 113 or the user data from the AP unit 112 are sent to the terminal-side communication unit 111.

[0044] The terminal-side communication unit 111 converts the data into a transmission signal for wireless communication and sends the transmission signal to the destination through one or more antennas.

[0045] Next, the reception process of UE110 will be described.

[0046] The terminal-side communication unit 111 receives a wireless signal from the transmission source as a reception signal through one or more antennas, and generates control data or user data based on the received signal. Then, the terminal-side communication unit 111 sends the control data to the protocol processing unit 113 and sends the user data to the AP unit 112.

[0047] A series of processes in UE110 as described above are controlled by the control unit 114. Although not shown in the figure, the control unit 114 is connected to the terminal-side communication unit 111, the AP unit 112, and the protocol processing unit 113.

[0048] In addition, the number of antennas used for transmission and the number of antennas used for reception in UE110 can be the same or different.

[0049] When the terminal-side communication unit 111 can utilize the emergency call service through the network connected by the relay device 110# of another UE acting as a relay, it functions as a communication unit that receives a Relay Discovery Solicitation (relay discovery request) message or a Relay Discovery Response (relay discovery response) message containing information indicating that the emergency call service can be provided. In addition, when the terminal-side communication unit 111 cannot utilize the emergency call service through the network connected by the relay device 110# but can perform a fallback for the emergency call service, it functions as a communication unit that receives a Relay Discovery Solicitation (relay discovery request) message or a Relay Discovery Response (relay discovery response) message containing information indicating that a switch to the utilization of the emergency call service is required.

[0050] When the protocol processing unit 113 can provide the emergency call service through the network connected by the relay device 110#, it accepts the relay to the network connected by the relay device 110# and accepts the provision of the emergency call service.

[0051] On the other hand, when the protocol processing unit 113 can fallback the emergency call service through the network connected by the relay device 110#, it accepts the relay to other networks through the fallback of the emergency call service and accepts the provision of the emergency call service.

[0052] In addition, the protocol processing unit 113 attaches information indicating acceptance of the provision of the emergency call service to the Relay Discovery Request message. Thereby, the UE 110 can notify the relay device 110# of the situation of accepting the provision of the emergency call service.

[0053] Some or all of the above-described AP unit 112, protocol processing unit 113, and control unit 114 can be composed of, for example, a memory 10 and a processor 11 such as a CPU (Central Processing Unit) that executes the program stored in the memory 10 as shown in Figure 3 (A). Such a program can be provided through a network, and can also be provided by being recorded on a recording medium. That is, such a program can also be provided as a program product, for example.

[0054] In addition, some or all of the AP unit 112, protocol processing unit 113, and control unit 114 can also be composed of, for example, a processing circuit 12 such as a single circuit, a composite circuit, a processor that operates according to a program, a parallel processor that operates according to a program, an ASIC (Application Specific Integrated Circuit), or an FPGA (Field Programmable Gate Array) as shown in Figure 3 (B).

[0055] As described above, the AP unit 112, protocol processing unit 113, and control unit 114 can be implemented by a processing circuit network.

[0056] In addition, the terminal-side communication unit 111 can be implemented by a wireless communication interface, which is an interface for wireless communication.

[0057] Any one of the multiple UEs 110 functions as a U2N repeater to become the relay device 110#. As shown in Figure 2 , the relay device 110# includes a terminal-side communication unit 111#, an AP unit 112#, a protocol processing unit 113#, and a control unit 114#. In addition, the structure of the relay device 110# is the same as that of the UE 110. In addition, the processing in the relay device 110# follows the regulations in 3GPP.

[0058] In addition, the communication unit 111 on the terminal side functions as a communication unit that relays the communication of the device to be relayed by another UE 110 to the first network that cannot utilize the emergency call service but supports the fallback of the emergency call service, or to the second network that is the fallback destination of the emergency call service. In Embodiment 1, the first network is the NG-RAN, and the second network is the E-UTRAN. In addition, in Embodiment 1, the NG-RAN base station 130A is also referred to as the first base station, and the E-UTRAN base station 130B is referred to as the second base station.

[0059] When the protocol processing unit 113 relays the communication of the device to be relayed to the first network and accepts a connection request from the device to be relayed to the emergency call service, it switches the communication of the device to be relayed to the second network.

[0060] The NG-RAN base station 130A corresponding to the 5G-based radio access network and the E-UTRAN base station 130B corresponding to the LTE-based radio access network can be configured in the same manner. Therefore, the following describes the structure of the base station 130.

[0061] Figure 4 It is a block diagram schematically showing the structure of the base station 130.

[0062] The base station 130 includes a station-side communication unit 131, a communication processing unit 132, a protocol processing unit 136, a control unit 137, and a storage unit 138.

[0063] The communication processing unit 132 includes a 5GC communication unit 133 that performs data transmission and reception with the 5GC, an EPC communication unit 134 that performs data transmission and reception with the EPC such as the Mobility Management Entity (MME), and an other base station communication unit 135 that performs data transmission and reception with other base stations. In addition, the 5GC communication unit 133, the EPC communication unit 134, and the other base station communication unit 135 respectively exchange information with the protocol processing unit 136.

[0064] First, the transmission processing of the base station 130 will be described.

[0065] The control data from the protocol processing unit 136, or the user data or control data from the 5GC communication unit 133, the EPC communication unit 134, or the other base station communication unit 135 is provided to the station-side communication unit 131.

[0066] The station-side communication unit 131 converts the data into a transmission signal for wireless communication and transmits the transmission signal to the destination through one or more antennas.

[0067] Next, the reception processing of the base station 130 will be described.

[0068] The station - side communication unit 131 receives a wireless signal from a transmission source as a received signal through one or more antennas, and generates control data or user data based on the received signal. Then, the station - side communication unit 131 sends the control data to the protocol processing unit 136, the 5GC communication unit 133, the EPC communication unit 134, or other base - station communication units 135, and sends the user data to the 5GC communication unit 133, the EPC communication unit 134, or other base - station communication units 135.

[0069] A series of processes in the base station 130 as described above are controlled by the control unit 137. Although not shown in the figure, the control unit 137 is connected to the station - side communication unit 131, the communication processing unit 132, and the protocol processing unit 136.

[0070] In addition, the number of antennas used for transmission in the base station 130 and the number of antennas used for reception may be the same or different.

[0071] Furthermore, the number of antennas of the UE 110 and the number of antennas of the base station 130 may be the same or different.

[0072] The storage unit 138 stores programs and data required for the processes in the base station 130.

[0073] Some or all of the communication processing unit 132, the protocol processing unit 136, and the control unit 137 described above can be composed of, for example, a memory 10 and a processor 11 such as a CPU that executes the program stored in the memory 10 as shown in Figure 3 (A). Such a program can be provided through a network, and can also be provided by being recorded on a recording medium. That is, such a program can also be provided as a program product, for example.

[0074] In addition, some or all of the communication processing unit 132, the protocol processing unit 136, and the control unit 137 can also be composed of, for example, a single circuit, a composite circuit, a processor that operates according to a program, a parallel processor that operates according to a program, a processing circuit 12 such as an ASIC or an FPGA as shown in Figure 3 (B).

[0075] As described above, the communication processing unit 132, the protocol processing unit 136, and the control unit 137 can be implemented by a processing - circuit network.

[0076] In addition, the station - side communication unit 131 can be implemented by a wireless communication interface, which is an interface for wireless communication.

[0077] The storage unit 126 can be implemented by a non-volatile memory or a storage device such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive).

[0078] Figure 5 It is a block diagram schematically showing the structure of the 5GC upper device 150.

[0079] The 5GC upper device 150 includes a data network communication unit 151, a base station communication unit 152, a user plane communication unit 153, a session management unit 154, a control plane control unit 155, and a control unit 159.

[0080] The data network communication unit 151 transmits and receives data between the 5GC upper device 150 and the data network. Here, the data network communication unit 151 can at least communicate with the EPC upper device 170.

[0081] The base station communication unit 152 performs NG interface data transmission and reception between the 5GC upper device 150 and the NG-RAN base station 130A.

[0082] When the data received from the data network is user data, the user data is sent from the data network communication unit 151 via the user plane communication unit 153 to the base station communication unit 152, and then sent from the base station communication unit 152 to the NG-RAN base station 130A.

[0083] When the data received from the NG-RAN base station 130 is user data, the user data is sent from the base station communication unit 152 via the user plane communication unit 153 to the data network communication unit 151, and then sent from the data network communication unit 151 to the data network.

[0084] When the data received from the data network is control data, the control data is sent from the data network communication unit 151 via the user plane communication unit 153 to the session management unit 154. The session management unit 154 sends the control data to the control plane control unit 155.

[0085] When the data received from the NG-RAN base station 130A is control data, the control data is sent from the base station communication unit 152 to the control plane control unit 155. The control plane control unit 155 sends the control data to the session management unit 154.

[0086] The control plane control unit 155 performs all processing for the control plane (hereinafter sometimes also referred to as the C-Plane).

[0087] The control plane control unit 155 includes a NAS (Non-Access Stratum) security unit 156, a PDU (Protocol Data Unit) session control unit 157, and an idle state mobility management unit 158.

[0088] The NAS security unit 156 is responsible for the security of NAS messages and the like.

[0089] The PDU session control unit 157 manages the PDU session between the UE 110 and the upper device 150 of the 5GC and the like.

[0090] The idle state mobility management unit 158 performs mobility management in the waiting state, generation and control of paging signals in the waiting state, addition, deletion, update, and retrieval of the tracking area of one or more subordinate UEs 110, and tracking area list management and the like. In addition, the waiting state is also referred to as the idle state, the RRC_IDLE state, or simply the idle state.

[0091] A series of processes of the upper device 150 of the 5GC are controlled by the control unit 159. Although not shown, the control unit 159 is connected to the data network communication unit 151, the base station communication unit 152, the user plane communication unit 153, the session management unit 154, and the control plane control unit 155.

[0092] Part or all of the data network communication unit 151, the base station communication unit 152, the user plane communication unit 153, the session management unit 154, the control plane control unit 155, and the control unit 159 can be composed of, for example, Figure 3 (A) a memory 10 and a processor 11 such as a CPU that executes a program stored in the memory 10. Such a program can be provided through a network, and can also be provided by being recorded on a recording medium. That is, such a program can also be provided as a program product, for example.

[0093] In addition, part or all of the data network communication unit 151, the base station communication unit 152, the user plane communication unit 153, the session management unit 154, the control plane control unit 155, and the control unit 159 can also be composed of, for example, Figure 3 (B) a single circuit, a composite circuit, a processor that operates according to a program, a parallel processor that operates according to a program, a processing circuit 12 such as an ASIC or an FPGA.

[0094] As described above, the data network communication unit 151, the base station communication unit 152, the user plane communication unit 153, the session management unit 154, the control plane control unit 155, and the control unit 159 can be implemented by a processing circuit network.

[0095] Figure 6 It is a block diagram schematically showing the structure of the EPC upper device 170.

[0096] The EPC upper device 170 includes a PDN GW (Packet Data Network Gate Way) communication unit 171, a base station communication unit 172, a user plane communication unit 173, a HeNB GW (Home-eNB Gate Way) communication unit 174, a control plane control unit 175, and a control unit 179.

[0097] The PDN GW communication unit 171 transmits and receives data between the EPC upper device 170 and the PDN GW. Here, it is assumed that the PDN GW communication unit 171 can at least communicate with the 5GC upper device 150.

[0098] The base station communication unit 172 transmits and receives data based on the S1 interface between the EPC upper device 170 and the E-UTRAN base station 130B.

[0099] When the data received from the PDN GW is user data, the user data is sent from the PDN GW communication unit 171 to the base station communication unit 172 via the user plane communication unit 173, and is sent from the base station communication unit 172 to the E-UTRAN base station 130B.

[0100] When the data received from the E-UTRAN base station 130B is user data, the user data is sent from the base station communication unit 172 to the PDN GW communication unit 171 via the user plane communication unit 173, and is sent from the PDN GW communication unit 171 to the PDN GW.

[0101] When the data received from the PDN GW is control data, the control data is sent from the PDN GW communication unit 171 to the control plane control unit 175.

[0102] When the data received from the E-UTRAN base station 130B is control data, the control data is sent from the base station communication unit 172 to the control plane control unit 175.

[0103] The HeNB GW communication unit 174 transmits and receives data between the EPC upper device 170 and the HeNB GW. The control data received by the HeNB GW communication unit 174 from the HeNB GW is sent to the control plane control unit 175. The HeNB GW communication unit 174 sends the control data from the control plane control unit 175 to the HeNB GW.

[0104] The control plane control unit 175 performs all processing for the control plane.

[0105] The control plane control unit 175 includes a NAS security unit 176, an SAE (System Architecture Evolution) bearer control unit 177, and an idle state mobility management unit 178.

[0106] The NAS security unit 176 is responsible for the security of NAS messages and so on.

[0107] The SAE bearer control unit 177 manages the bearers of SAE and so on.

[0108] The idle state mobility management unit 178 performs mobility management of the idle state (also referred to as the LTE-IDLE state or simply the idle state) which is a waiting state, generation and control of paging signals in the waiting state, addition, deletion, update, and retrieval of the tracking area of the UE 110 under the umbrella, and tracking area list management and so on.

[0109] The EPC upper device 170 allocates paging signals to the E-UTRAN base station 130B. In addition, the EPC upper device 170 performs mobility control of the waiting state. The EPC upper device 170 manages the tracking area list when the UE 110 is in the waiting state and in the active state. The EPC upper device 170 sends a paging message to the cell belonging to the tracking area in which the UE 110 is registered, thereby starting the paging protocol. Management of the CSG of the eNB connected to the EPC upper device 170, management of the CSG ID, and management of the whitelist can also be performed by the idle state mobility management unit 178.

[0110] A series of processes of the EPC upper device 170 are controlled by the control unit 179. Although not shown, the control unit 179 is connected to the PDN GW communication unit 171, the base station communication unit 172, the user plane communication unit 173, the HeNB GW communication unit 174, and the control plane control unit 175.

[0111] Part or all of the PDN GW communication unit 171, the base station communication unit 172, the user plane communication unit 173, the HeNB GW communication unit 174, the control plane control unit 175, and the control unit 179 can be constituted by, for example, a memory 10 and a processor 11 such as a CPU that executes the program stored in the memory 10 as shown in Figure 3 (A). Such a program can be provided via a network, and can also be provided by being recorded on a recording medium. That is, such a program can also be provided as a program product, for example.

[0112] In addition, some or all of the PDN GW communication unit 171, the base station communication unit 172, the user plane communication unit 173, the HeNB GW communication unit 174, the control plane control unit 175, and the control unit 179 can also be, for example, as Figure 3 shown in (B), constituted by a single circuit, a composite circuit, a processor that operates according to a program, a parallel processor that operates according to a program, an ASIC, an FPGA, or other processing circuit 12.

[0113] As described above, the PDN GW communication unit 171, the base station communication unit 172, the user plane communication unit 173, the HeNB GW communication unit 174, the control plane control unit 175, and the control unit 179 can be implemented by a processing circuit network.

[0114] Figure 7 It is a timing chart showing the steps for implementing an emergency call service in Embodiment 1.

[0115] First, the protocol processing unit 113# of the relay device 110# that functions as a U2N repeater is connected to the 5GC upper device 150 that constitutes the 5G core network via the NG-RAN base station 130A that constitutes the NG-RAN (S10). At this time, the protocol processing unit 113# of the relay device 110# receives information on whether Emergency Service is supported and whether Emergency Service Fallback is supported from the control plane control unit 155 of the 5GC upper device 150 that functions as an AMF (Access Management Function) and a UPF in the 5G core network. Thereby, the protocol processing unit 113# of the relay device 110# grasps whether the emergency call service can be used between the connected base station 130, or whether it is necessary to switch (fall back) to the E-UTRAN of this base station, or whether it is necessary to reconnect to another cell. Here, it is assumed that the protocol processing unit 113# of the relay device 110# has grasped the case where it is necessary to switch (fall back) to the E-UTRAN of this base station for explanation.

[0116] Next, the protocol processing unit 113 of the relay device 110# notifies the approaching UE110 of the availability of relay services in accordance with the steps of mode A or mode B of Relay Discovery (S11). At this time, the protocol processing unit 113 may also attach information on whether emergency call services of the connected base station 130 can be used, whether it is necessary to switch to the E-UTRAN of this base station, or whether it is necessary to reconnect to another cell, which was obtained in step S10, to the Relay Discovery Solicitation message or the Relay Discovery Response message.

[0117] Although not shown, the UE110 that wants to use the emergency call service first searches for whether it can directly communicate with a base station that provides emergency call services within the service area. Here, it is assumed that there is no base station that provides emergency call services within the service area for explanation.

[0118] In the case where there is no base station that provides emergency call services within the service area, the protocol processing unit 113 of the UE110 searches for a U2N repeater in accordance with the steps of Relay Discovery. Here, it is assumed that the relay device 110# that functions as a U2N repeater is discovered for explanation.

[0119] In this case, the protocol processing unit 113 of the UE110 sends a Direct Communication Request and attempts to connect to the relay device 110# (S12). At this time, the protocol processing unit 113 can also select a U2N repeater that is connected to a base station that provides emergency call services or a base station that can use emergency call services by switching to the E-UTRAN based on the information identified in step S11, send a Direct Communication Request, and start communication. At this time, the protocol processing unit 113 of the UE110 may also attach information indicating the use of emergency call services to this Direct Communication Request and notify this information to the U2N repeater.

[0120] Next, the protocol processing unit 113 of the relay device 110# that has received this Direct Communication Request requests the 5GC upper device 150 that functions as an AMF of the 5G core network to start an Emergency Service session (S13).

[0121] When receiving a request to start a session for Emergency Service, the control plane control unit 155 of the 5GC upper device 150 starts a session corresponding to the Emergency Service when the 5GC core network supports emergency call services. Here, it is assumed that the 5GC core network does not support emergency call services but supports fallback for emergency call services for explanation.

[0122] In such a case, the control plane control unit 155 of the 5GC upper device 150 causes the control plane control unit 175 of the EPC upper device 170 to perform a handover to the E-UTRAN base station 130B that constitutes the E-UTRAN, and starts the session (S14).

[0123] Next, the protocol processing unit 113# of the relay device 110# establishes a session with the IMS 190 via the handover-completed E-UTRAN base station 130B and connects to an emergency notification center such as eCall that uses the emergency call service (S15).

[0124] Next, when both the handover based on the fallback of the emergency call service and the session establishment with the IMS 190 are successful, the protocol processing unit 113# of the relay device 110# sends an ACK (ACKnowledgement) signal for DirectCommunication to the UE 110 that wants to use the emergency call service (S16). Although not shown, in the case where any of the above steps fails, the protocol processing unit 113# of the relay device 110# can also immediately send a NACK (Negative ACKnowledgement) signal to the UE 110 at the time of failure. In addition, the protocol processing unit 113# of the relay device 110# can also temporarily send an ACK signal in any of the above steps to shorten the response time.

[0125] Next, the protocol processing unit 113 of the UE 110 that wants to use the emergency call service establishes direct communication with the relay device 110# (S17).

[0126] Next, the protocol processing unit 113# of the relay device 110# reports the success of the direct communication in step S17 and the relay with the E-UTRAN base station 130B to the EPC upper device 170 (S18). In the EPC upper device 170, such a report is received by the control plane control unit 175 that functions as the EPC.

[0127] Next, the AP unit 112 of the UE 110 starts communication with the emergency notification center via the relay device 110# (S19, S20).

[0128] Through the above steps, the UE 110 can perform emergency communication via the U2N repeater and through fallback of the emergency call service.

[0129] In addition, the UE 110 can reliably start emergency communication by selecting a base station 130 that can utilize the emergency call service or a base station 130 that can perform fallback of the emergency call service.

[0130] Furthermore, Embodiment 1 describes the fallback of the emergency call service using the U2N repeater, but Embodiment 1 is not limited to the emergency call service. It can also be applied to services that support fallback mechanisms other than the emergency call service.

[0131] Embodiment 2.

[0132] Embodiment 1 shows an example in which the U2N repeater is connected to the NG-RAN (5G core network) and performs fallback of the emergency call service to the E-UTRAN as needed. Conversely, it can also be switched from the E-UTRAN to the NG-RAN (5G core network) through fallback of the emergency call service. Embodiment 2 describes such an example.

[0133] In addition, in Embodiment 2, the first network is the E-UTRAN, and the second network is the NG-RAN. Also, in Embodiment 2, the E-UTRAN base station 130B is also referred to as the first base station, and the NG-RAN base station 130A is referred to as the second base station.

[0134] Figure 8 It is a block diagram schematically showing the structure of the wireless communication system 200 of Embodiment 2.

[0135] The wireless communication system 200 includes a UE 110, a relay device 110#, an NG-RAN base station 130A, a 5GC upper device 150, an E-UTRAN base station 130B, and an EPC upper device 170.

[0136] The wireless communication system 200 is a system for receiving the provision of the emergency call service from the PSAP 191 via the IMS 190.

[0137] Here, in the wireless communication system 200 of Embodiment 2, although the E-UTRAN base station 130B and the EPC upper device 170 do not support the emergency call service, they are connected to the emergency call service via the 5GC upper device 150 that supports the emergency call service.

[0138] In addition, the structures of the UE 110, relay device 110#, NG-RAN base station 130A, 5GC upper device 150, E-UTRAN base station 130B, and EPC upper device 170 of the wireless communication system 200 in Embodiment 2 are the same as those of the UE 110, relay device 110#, NG-RAN base station 130A, 5GC upper device 150, E-UTRAN base station 130B, and EPC upper device 170 of the wireless communication system 100 in Embodiment 1.

[0139] Figure 9 It is a timing chart showing the steps for implementing an emergency call service in Embodiment 2.

[0140] First, the protocol processing unit 113# of the relay device 110# functioning as a U2N repeater is connected to the EPC upper device 170 via the E-UTRAN base station 130B constituting the E-UTRAN (S30). At this time, the protocol processing unit 113# of the relay device 110# receives information on whether Emergency Service (emergency service) is supported and whether Emergency Service Fallback (emergency service fallback) is supported from the control plane control unit 175 of the EPC upper device 170 functioning as the EPC in the E-UTRAN. Thereby, the protocol processing unit 113# of the relay device 110# determines whether the emergency call service can be used with the connected base station 130, whether it is necessary to switch (fall back) to the NG-RAN of this base station, or whether it is necessary to reconnect to another cell. Here, it is assumed that the protocol processing unit 113# of the relay device 110# has determined that it is necessary to switch (fall back) to the NG-RAN of this base station for explanation.

[0141] Next, the protocol processing unit 113# of the relay device 110# notifies the approaching UE 110 that relay services can be provided according to the steps of Relay Discovery mode A or mode B (S31). At this time, the protocol processing unit 113# may also attach to the Relay Discovery Solicitation message or the Relay Discovery Response message information on whether the emergency call service of the connected base station 130 can be used, whether it is necessary to switch to the NG-RAN of this base station as needed, or whether it is necessary to reconnect to another cell, which was obtained in step S30.

[0142] Although not shown, the UE 110 that wants to use the emergency call service first searches for whether it can directly communicate with the base station that provides the emergency call service within the service area. Here, it is assumed that there is no base station that provides the emergency call service within the service area for the explanation.

[0143] In the case where there is no base station that provides the emergency call service within the service area, the protocol processing unit 113 of the UE 110 searches for the U2N repeater according to the steps of Relay Discovery (relay discovery). Here, it is assumed that the relay device 110# that functions as the U2N repeater is discovered for the explanation.

[0144] In this case, the protocol processing unit 113 of the UE 110 sends a Direct Communication Request (direct communication request) and attempts to connect to the relay device 110# (S32). At this time, the protocol processing unit 113 can also select the U2N repeater that connects to the base station that provides the emergency call service or the base station that can use the emergency call service by switching to NG-RAN based on the information identified in step S31, send a Direct Communication Request (direct communication request), and start communication. At this time, the protocol processing unit 113 of the UE 110 can also attach the information indicating the use of the emergency call service to the Direct Communication Request (direct communication request) and notify this information to the U2N repeater.

[0145] Next, the protocol processing unit 113# of the relay device 110# that receives the Direct Communication Request (direct communication request) requests the EPC upper device 170 that functions as the EPC of the E-UTRAN to start a session of Emergency Service (emergency service) (S33).

[0146] When accepting the request to start the session of Emergency Service (emergency service), the control plane control unit 175 of the EPC upper device 170 starts the session corresponding to the Emergency Service (emergency service) in the case where the E-UTRAN supports the emergency call service. Here, it is assumed that the E-UTRAN does not support the emergency call service but supports the fallback of the emergency call service for the explanation.

[0147] In such a case, the control plane control unit 175 of the EPC upper device 170 causes the control plane control unit 155 of the 5GC upper device 150 to perform a handover to the NG-RAN base station 130A that constitutes the NG-RAN and starts the session (S34).

[0148] Next, the protocol processing unit 113# of the relay device 110# establishes a session with the IMS 190 via the switched NG-RAN base station 130A and connects to an emergency notification center (such as eCall) that utilizes the emergency call service (S35).

[0149] Next, when both the handover based on the fallback of the emergency call service and the session establishment with the IMS 190 are successful, the protocol processing unit 113# of the relay device 110# sends an ACK signal for DirectCommunication (direct communication) to the UE 110 that wants to utilize the emergency call service (S36). Although not shown in the figure, if any of the above steps fails, the protocol processing unit 113# of the relay device 110# can also immediately send a NACK signal to the UE 110 at the time of failure. In addition, the protocol processing unit 113# of the relay device 110# can also temporarily send an ACK signal in any of the above steps to shorten the response time.

[0150] Next, the protocol processing unit 113 of the UE 110 that wants to utilize the emergency call service establishes direct communication with the relay device 110# (S37).

[0151] Next, the protocol processing unit 113# of the relay device 110# reports the success of the direct communication in step S37 and the relay with the NG-RAN base station 130A to the 5GC upper device 150 (S38). In the 5GC upper device 150, the control plane control unit 155 that functions as the AMF receives such a report.

[0152] Next, the AP unit 112 of the UE 110 starts communication with the emergency notification center via the relay device 110# (S39, S40).

[0153] Through the above steps, the UE 110 can perform emergency communication via the U2N repeater and through the fallback of the emergency call service.

[0154] In addition, by selecting the base station 130 that can utilize the emergency call service or the base station 130 that can perform the fallback of the emergency call service, the UE 110 can reliably start emergency communication.

[0155] Variant example.

[0156] In Embodiment 1 and Embodiment 2, when the fallback of the emergency call service of the relay device 110# fails and the handover is abandoned, the relay device 110# reconnects to the original base station 130 and sends a NACK signal to the UE 110 that requested the relay communication of the emergency call service, causing the UE 110 to attempt other connection methods.

[0157] In this case, different from a request for an emergency call service made through direct communication with a normal base station 130, the base station 130 and the network side cannot detect which UE 110 has requested the emergency call service, that is, they cannot detect who is in an emergency situation where.

[0158] Therefore, as a modification of Embodiment 1 and Embodiment 2, when the protocol processing unit 113# of the relay device 110# receives a connection request for an emergency call service from the UE 110 and the connection to the emergency call service in the first network fails, or when it receives a connection request for an emergency call service from the UE 110 and the handover to the second network fails, it notifies the first base station of the identification information for identifying the UE 110.

[0159] Specifically, at the time of sending a DirectCommunication Request (direct communication request) in step S12 shown in Figure 7 or in step S32 shown in Figure 9 the protocol processing unit 113# of the UE 110 may also send terminal identification information, which is used to identify the UE 110 making the request in addition to communication using the emergency call service. Here, as the terminal identification information, for example, SIM (Subscriber Identity Module) information or location information indicating the location of the UE 110 can be used.

[0160] In addition, the relay device 110# may, instead of Figure 7 step S18 shown in Figure 9 or step S38 shown in Figure 7 report a handover failure to the original base station 130 to which reconnection is made ( Figure 9 NG-RAN base station 130A in

[0161] and E-UTRAN base station 130B in

[0162] ), and at this time, notify the above-obtained terminal identification information. Through the above method, even when the fallback of the emergency call service of the relay device 110# fails, the base station 130 and the network can determine the terminal that needs to be emergently reported.

[0162] Description of Reference Numerals

[0163] 100, 200 wireless communication systems, 110 UE, 111 terminal-side communication unit, 112 AP unit, 113 protocol processing unit, 114 control unit, 110# relay device, 111# terminal-side communication unit, 112# AP unit, 113# protocol processing unit, 114# control unit, 130 ANG-RAN base station, 130B E-UTRAN base station, 131 station-side communication unit, 132 communication processing unit, 136 protocol processing unit, 137 control unit, 138 storage unit, 150 5GC upper device, 151 data network communication unit, 152 base station communication unit, 153 user plane communication unit, 154 session management unit, 155 control plane control unit, 159 control unit, 170 EPC upper device, 171 PDN GW communication unit, 172 base station communication unit, 173 user plane communication unit, 174 HeNBGW communication unit, 175 control plane control unit, 179 control unit, 190 IMS, 191 PSAP.

Claims

1. A terminal device, characterized in that: The terminal device includes: A communication unit that relays the communication of a relay target device, which is another terminal device, to a first network or a second network, where the first network cannot use the emergency call service but supports fallback of the emergency call service, and the second network is the fallback destination of the emergency call service; and A protocol processing unit that, when relaying the communication of the relay target device to the first network, switches the communication of the relay target device to the second network when receiving a connection request to the emergency call service from the relay target device.

2. The terminal device according to claim 1, characterized in that: When the emergency call service can be used in the network connected to the communication unit, the protocol processing unit includes information indicating that the emergency call service can be provided in a relay discovery request message or a relay discovery response message for the relay target device; when the emergency call service cannot be used in the network connected to the communication unit but fallback of the emergency call service is possible, the protocol processing unit includes information indicating that a switch is required to use the emergency call service in a relay discovery request message or a relay discovery response message for the relay target device.

3. A terminal device, characterized in that: The terminal device includes: A communication unit that, when the emergency call service can be used in the network connected to a relay device that is another terminal device for relaying, receives a relay discovery request message or a relay discovery response message containing information indicating that the emergency call service can be provided; when the emergency call service cannot be used in the network connected to the relay device but fallback of the emergency call service is possible, receives a relay discovery request message or a relay discovery response message containing information indicating that a switch is required to use the emergency call service; And A protocol processing unit that, when the emergency call service can be provided in the network connected to the relay device, accepts relaying to the network connected to the relay device, thereby accepting the provision of the emergency call service; when fallback of the emergency call service is possible in the network connected to the relay device, accepts relaying to another network through fallback of the emergency call service, thereby accepting the provision of the emergency call service.

4. The terminal device according to claim 3, characterized in that: The protocol processing unit attaches information indicating acceptance of the provision of the emergency call service to the relay discovery request message.

5. A wireless communication system, characterized in that: The wireless communication system includes: A first base station included in a first network that cannot use the emergency call service but supports fallback of the emergency call service; A second base station included in a second network that is the fallback destination of the emergency call service; And A terminal device that performs relaying to the first base station and the second base station, The terminal device includes: A communication unit that relays the communication of a relay target device, which is another terminal device, to the first base station or the second base station; and A protocol processing unit that, when relaying the communication of the relay target device to the first base station, switches the communication of the relay target device to the second base station when a connection request to the emergency call service is received from the relay target device via the communication unit.

6. The wireless communication system according to claim 5, wherein when the emergency call service can be used in the network connected to the communication unit, the protocol processing unit includes information indicating that the emergency call service can be provided in a relay discovery request message or a relay discovery response message for the relay target device; when the emergency call service cannot be used in the network connected to the communication unit but fallback of the emergency call service is possible, the protocol processing unit includes information indicating that a switch is required to use the emergency call service in a relay discovery request message or a relay discovery response message for the relay target device.

7. The wireless communication system according to claim 5 or 6, wherein when a connection request to the emergency call service is received from the relay target device and the connection to the emergency call service fails in the first network, or when a connection request to the emergency call service is received from the relay target device and the switch to the second network fails, the protocol processing unit notifies the first base station of the identification information for identifying the relay target device.

8. A relay method, characterized in that when relaying the communication of a relay target device to a first network that cannot use the emergency call service but supports fallback of the emergency call service, a connection request to the emergency call service is received from the relay target device, and the communication of the relay target device is switched to a second network that is the fallback destination of the emergency call service.

9. A relay method, characterized in that when the emergency call service can be used in the network connected to a relay device that is a relay for other terminal devices performing relaying, a relay discovery request message or a relay discovery response message containing information indicating that the emergency call service can be provided is received, when the emergency call service cannot be used in the network connected to the relay device but fallback of the emergency call service is possible, a relay discovery request message or a relay discovery response message containing information indicating that a switch is required to use the emergency call service is received, when the emergency call service can be provided in the network connected to the relay device, relaying to the network connected to the relay device is accepted, and thus the provision of the emergency call service is accepted, when fallback of the emergency call service is possible in the network connected to the relay device, relaying to another network is accepted through fallback of the emergency call service, and thus the provision of the emergency call service is accepted.

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