User equipment (UE)

Abstract

This UE operates as a 5G ProSe multi-hop U2U relay UE, the UE transmitting a PROSE direct link establishment rejection message including a reason value and the timer value of a back-off timer to a second 5G ProSe multi-hop U2U relay UE. The UE does not initiate a 5G ProSe direct link release procedure in cases where a first direct link is released and a second direct link is present.

Description

UE (User Equipment)

[0001] This embodiment relates to a UE (User Equipment). This application claims priority to Japanese Patent Application No. 2024-43041, filed on March 19, 2024, the contents of which are incorporated herein by reference.

[0002] The 3GPP (3rd Generation Partnership Project) is studying the system architecture of the 5G System (5GS), a fifth-generation (5G) mobile communication system, and is discussing how to support new procedures and new functions (see Non-Patent Documents 1 to 4). Currently, as part of the study toward the Release 19 specification, discussions are underway regarding the extension of Proximity-based Services (ProSe) functions (see Non-Patent Document 5).

[0003] 3GPP TS 23.304 V18.4.0 (2023-12); 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Proximity based Services (ProSe) in the 5G System (5GS); (Release 18)3GPP TS 24.554 V18.3.0 (2023-12); 3rd Generation Partnership Project; Technical Specification Group Core Network and Terminals; Proximity-services (ProSe) in 5G System (5GS) protocol aspects; Stage 3 (Release 18)3GPP TS 24.555 V18.3.0 (2023-12); 3rd Generation Partnership Project; Technical Specification Group Core Network and Terminals; Proximity-services (ProSe) in 5G System (5GS); User Equipment (UE) policies; Stage 3 (Release 18)3GPP TS 24.501 V18.5.0 (2023-12); 3rd Generation Partnership Project; Technical Specification Group Core Network and Terminals; Non-Access-Stratum (NAS) protocol for 5G System (5GS); Stage 3 (Release 18)3GPP TR 23.700-03 V0.2.0 (2024-03); 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Study on system enhancement for Proximity based Services (ProSe) in the 5G System (5GS); Phase 3 (Release 19).

[0004] Currently, Proximity-services (ProSe) is being considered for 5GS to realize close-proximity wireless communication between UEs. Furthermore, Release 19 considers multi-hop communication between UEs. However, when multiple UEs communicate using multi-hop, the UE behavior when a request to establish direct communication is rejected is unclear. Furthermore, when multiple UEs communicate using multi-hop, the UE behavior when an intermediate route is released is unclear.

[0005] This embodiment has been made in consideration of the above circumstances. In this embodiment, the behavior of a UE when a request to establish direct communication is rejected during communication between multiple UEs using multi-hop is clarified. Also, the behavior of a UE when an intermediate route is released during communication between multiple UEs using multi-hop is clarified.

[0006] A UE (User Equipment) of this embodiment is a UE including a transceiver unit and a control unit, the UE being a UE operating as a first 5G Proximity based Services (ProSe) multi-hop UE-to-UE (U2U) relay UE, wherein in a first 5G ProSe direct link establishment procedure between the UE and a second 5G ProSe multi-hop U2U relay UE, the transceiver unit receives a first PROSE direct link establishment request message from the second 5G ProSe multi-hop U2U relay UE, and in a second 5G ProSe direct link establishment procedure between the UE and a target 5G ProSe end UE, the transceiver unit transmits a second PROSE direct link establishment request message to the target 5G ProSe end UE, and the transceiver unit transmits a second PROSE direct link establishment request message to the target 5G ProSe end UE. and receiving, from the UE, a second PROSE direct link establishment rejection message including a first reason value and a timer value of a first back-off timer, and if the timer value of the second back-off timer is greater than the timer value of the first back-off timer, the transceiver unit transmits, to the second 5G ProSe multi-hop U2U relay UE, a first PROSE direct link establishment rejection message including a second reason value and the timer value of the second back-off timer, and if the timer value of the first back-off timer is greater than the timer value of the second back-off timer, the transceiver unit transmits, to the second 5G ProSe multi-hop U2U relay UE, a first PROSE direct link establishment rejection message including the first reason value and the timer value of the first back-off timer, indicates that a ProSe multi-hop U2U relay UE is unavailable, and the timer value of the second backoff timer is the timer value of a timer for limiting the initiation of a first 5G ProSe direct link establishment procedure.

[0007] A UE (User Equipment) of this embodiment is a UE including a transceiver unit and a controller, the UE being a UE operating as a first 5G Proximity based Services (ProSe) multi-hop UE-to-UE (U2U) relay UE, and in a 5G ProSe direct link establishment procedure between the UE and a second 5G ProSe multi-hop U2U relay UE, the transceiver unit transmits a PROSE direct link establishment request message to the second 5G ProSe multi-hop U2U relay UE, the transceiver unit receives a PROSE direct link establishment rejection message including a reason value and a timer value of a back-off timer from the second 5G ProSe multi-hop U2U relay UE, the controller starts a timer using the timer value of the back-off timer, and if the timer is running, the transceiver unit does not re-execute a 5G ProSe direct link establishment procedure with the second 5G ProSe multi-hop U2U relay UE, and the reason value is a 5G ProSe multi-hop U2U relay UE. The back-off timer indicates that the UE is unavailable, and the timer value of the back-off timer is the timer value of a timer for limiting the start of a 5G ProSe direct link establishment procedure.

[0008] According to this embodiment, when a plurality of UEs communicate using multi-hop, the behavior of the UE when a request to establish direct communication is rejected is clarified. Also, when a plurality of UEs communicate using multi-hop, the behavior of the UE when an intermediate route is released is clarified.

[0009] FIG. 1 is a diagram illustrating an overview of a mobile communication system (EPS / 5GS). FIG. 2 is a diagram illustrating a detailed configuration of a mobile communication system (EPS / 5GS). FIG. 3 is a diagram illustrating a device configuration of a UE. FIG. 4 is a diagram illustrating a configuration of an access network device (gNB) in 5GS. FIG. 5 is a diagram illustrating a configuration of a core network device (AMF / SMF / UPF) in 5GS. FIG. 6 is a diagram illustrating a registration procedure. FIG. 7 is a diagram illustrating a 5G ProSe direct link establishment procedure. FIG. 8 is a diagram illustrating a first communication mode of the 5G ProSe direct link establishment procedure. FIG. 9 is a diagram illustrating a second communication mode of the 5G ProSe direct link establishment procedure. FIG. 10 is a diagram illustrating a third communication mode of the 5G ProSe direct link establishment procedure. FIG. 11 is a diagram illustrating a fourth communication mode of the 5G ProSe direct link establishment procedure. FIG. 12 is a diagram illustrating a 5G ProSe direct link release procedure. FIG. 13 is a diagram illustrating an example configuration of a communication mode of a 5G ProSe direct link.

[0010] Hereinafter, a mode for carrying out the present embodiment will be described with reference to the drawings. In the present embodiment, as an example, an embodiment of a mobile communication system to which the present embodiment is applied will be described.

[0011] [1. System Overview] First, FIG. 1 is a diagram for explaining an overview of a mobile communication system 1 used in each embodiment, and FIG. 2 is a diagram for explaining a detailed configuration of the mobile communication system 1.

[0012] FIG. 1 shows that the mobile communication system 1 is composed of UE_A10, access network _A80, core network _A90, PDN (Packet Data Network) _A5, access network _B120, core network _B190, and DN (Data Network) _A6.

[0013] In the following, these devices and functions may be referred to by abbreviating the symbols, such as UE, access network_A, core network_A, PDN, access network_B, core network_B, DN, etc.

[0014] Figure 2 also shows devices and functions such as UE_A10, E-UTRAN80, MME40, SGW35, PGW-U30, PGW-C32, PCRF60, HSS50, 5G AN120, AMF140, UPF130, SMF132, PCF160, UDM150, and N3IWF170, as well as interfaces that connect these devices and functions to each other.

[0015] In the following, these devices and functions may be referred to by abbreviated symbols such as UE, E-UTRAN, MME, SGW, PGW-U, PGW-C, PCRF, HSS, 5G AN, AMF, UPF, SMF, PCF, UDM, N3IWF, etc.

[0016] The 4G system EPS (Evolved Packet System) includes an access network _A and a core network _A, but may further include a UE and / or a PDN. The 5G system 5GS (5G System) includes a UE, an access network _B, and a core network _B, but may further include a DN.

[0017] The UE is a device that can connect to a network service via 3GPP access (also referred to as a 3GPP access network, or 3GPP AN) and / or non-3GPP access (also referred to as a non-3GPP access network, or non-3GPP AN). The UE may be a terminal device capable of wireless communication, such as a mobile phone or a smartphone, and may be a terminal device that can connect to both EPS and 5GS. The UE may include a UICC (Universal Integrated Circuit Card) or an eUICC (Embedded UICC).

[0018] Furthermore, access network_A corresponds to an E-UTRAN (Evolved Universal Terrestrial Radio Access Network) and / or a wireless LAN access network. One or more eNBs (evolved Node Bs) 45 are deployed in the E-UTRAN. Note that, hereinafter, the eNB 45 may be referred to by abbreviating the symbol eNB. If there are multiple eNBs, the eNBs are connected to each other, for example, via an X2 interface. Furthermore, one or more access points are deployed in the wireless LAN access network.

[0019] Furthermore, access network_B corresponds to a 5G access network (5G AN). The 5G AN is composed of an NG-RAN (NG Radio Access Network) and / or a non-3GPP access network. One or more gNBs (NR NodeBs) 122 are deployed in the NG-RAN. Note that, hereinafter, the symbol for gNB 122 may be abbreviated, such as gNB. The gNB is a node that provides the NR (New Radio) user plane and control plane to UEs and connects to the 5GCN via an NG interface (including an N2 interface or an N3 interface). In other words, the gNB is a base station device newly designed for 5GS, and has different functions from the base station device (eNB) used in the 4G system EPS. Furthermore, when there are multiple gNBs, the gNBs are connected to each other, for example, via an Xn interface.

[0020] Furthermore, the non-3GPP access network may be an untrusted non-3GPP access network or a trusted non-3GPP access network. Here, the untrusted non-3GPP access network may be a non-3GPP access network that does not perform security management within the access network, such as a public wireless LAN. On the other hand, the trusted non-3GPP access network may be an access network specified by 3GPP, and may include a trusted non-3GPP access point (TNAP) and a trusted non-3GPP gateway function (TNGF).

[0021] In the following, E-UTRAN and NG-RAN may be referred to as 3GPP access. Also, wireless LAN access networks and non-3GPP AN may be referred to as non-3GPP access. Also, nodes located in access network_B may be collectively referred to as NG-RAN nodes.

[0022] Furthermore, in the following, access network _A, and / or access network _B, and / or devices included in access network _A, and / or devices included in access network _B may be referred to as access networks or access network devices.

[0023] The core network_A corresponds to an EPC (Evolved Packet Core), which includes, for example, an MME (Mobility Management Entity), an SGW (Serving Gateway), a PGW (Packet Data Network Gateway)-U, a PGW-C, a PCRF (Policy and Charging Rules Function), and an HSS (Home Subscriber Server).

[0024] Furthermore, the core network_B corresponds to a 5G Core Network (5GCN). In the 5GCN, for example, an Access and Mobility Management Function (AMF), a User Plane Function (UPF), a Session Management Function (SMF), a Policy Control Function (PCF), a Unified Data Management (UDM), etc. are arranged. Here, the 5GCN may be expressed as a 5GC.

[0025] In addition, in the following, core network _A and / or core network _B, devices included in core network _A, and / or devices included in core network _B may be referred to as core networks, core network devices, or devices within the core network.

[0026] The core network (core network _A and / or core network _B) may be an IP mobile communication network operated by a mobile network operator (MNO) that connects the access network (access network _A and / or access network _B) to the PDN and / or DN, or it may be a core network for a mobile network operator that operates and manages the mobile communication system 1, or it may be a core network for a virtual mobile communication operator or virtual mobile communication service provider such as an MVNO (Mobile Virtual Network Operator) or MVNE (Mobile Virtual Network Enabler).

[0027] Also, while FIG. 1 illustrates a case where the PDN and the DN are the same, they may be different. The PDN may be a DN (Data Network) that provides communication services to the UE. The DN may be configured as a packet data service network, or may be configured for each service. Furthermore, the PDN may include a connected communication terminal. Therefore, connecting to the PDN may mean connecting to a communication terminal or a server device located in the PDN. Furthermore, transmitting and receiving user data to and from the PDN may mean transmitting and receiving user data to and from a communication terminal or a server device located in the PDN. The PDN may be referred to as the DN, and the DN may be referred to as the PDN.

[0028] In addition, hereinafter, at least a portion of the access network _A, the core network _A, the PDN, the access network _B, the core network _B, and the DN, and / or one or more devices included therein may be referred to as a network or a network device. In other words, when a network and / or a network device sends or receives a message and / or performs a procedure, it means that at least a portion of the access network _A, the core network _A, the PDN, the access network _B, the core network _B, and the DN, and / or one or more devices included therein send or receive a message and / or perform a procedure.

[0029] The UE can also connect to an access network. The UE can also connect to a core network via the access network. The UE can also connect to a PDN or DN via the access network and the core network. That is, the UE can transmit and receive (communicate) user data with the PDN or DN. When transmitting and receiving user data, not only IP (Internet Protocol) communication but also non-IP communication can be used.

[0030] Here, IP communication refers to data communication using IP, and data is transmitted and received using IP packets. An IP packet consists of an IP header and a payload portion. The payload portion may include data transmitted and received by devices and functions included in EPS or devices and functions included in 5GS. Non-IP communication refers to data communication that does not use IP, and data is transmitted and received in a format different from the IP packet structure. For example, non-IP communication may be data communication achieved by transmitting and receiving application data without an IP header, or it may be user data transmitted and received by a UE with a different header such as a MAC header or an Ethernet (registered trademark) frame header.

[0031] In addition, access network _A, core network _A, access network _B, core network _B, PDN_A, and DN_A may be configured with devices not shown in Fig. 2. For example, core network _A and / or core network _B may include an AUSF (Authentication Server Function) and an AAA (Authentication, authorization, and accounting) server (AAA-S).

[0032] Here, the AUSF is a core network device having an authentication function for 3GPP access and non-3GPP access, specifically, a network function unit that receives an authentication request for 3GPP access and / or non-3GPP access from a UE and executes the authentication procedure.

[0033] The AAA server is a device that has authentication, authorization, and accounting functions and is connected to the AUSF directly or indirectly via another network device. The AAA server may be a network device within the core network. The AAA server may not be included in the core network _A and / or core network _B, but may be included in the PLMN. In other words, the AAA server may be a core network device or a device outside the core network. For example, the AAA server may be a server device within the PLMN managed by a third party.

[0034] 2, for the sake of simplicity, each device and function is shown one by one, but multiple similar devices and functions may be configured in the mobile communication system 1. Specifically, the mobile communication system 1 may be configured with multiple devices and functions such as UE_A10, E-UTRAN80, MME40, SGW35, PGW-U30, PGW-C32, PCRF60, HSS50, 5G AN120, AMF140, UPF130, SMF132, PCF160, and / or UDM150.

[0035] The UPF_A235 is connected to the DN, the SMF, other UPFs, and the access network. The UPF_A235 may perform functions such as an anchor for intra-RAT mobility or inter-RAT mobility, packet routing and forwarding, an UL CL (Uplink Classifier) ​​function that supports routing of multiple traffic flows for one DN, a branching point function that supports multi-homed PDU sessions, QoS processing for the user plane, verification of uplink traffic, buffering of downlink packets, and a trigger function for downlink data notification. The UPF_A235 may also be a relay device that forwards user data as a gateway between the DN and the core network_B190. The UPF_A235 may also be a gateway for IP communication and / or non-IP communication. The UPF_A235 may also have a function for forwarding IP communication and a function for converting non-IP communication to IP communication. Furthermore, multiple gateways may be gateways that connect the core network _B190 to a single DN. Note that UPF_A235 may have connectivity with other NFs and may be connected to each device via other NFs.

[0036] Between UPF_A235 and the access network, UPF_C239 (also called a branching point or uplink classifier), which is a UPF different from UPF_A235, may exist as a device or NF. When UPF_C239 exists, a PDU session between the UE and the DN will be established via the access network, UPF_C239, and UPF_A235.

[0037] Furthermore, the UPF 130 may be the same device as the UPF_A 235. Note that the UPF 130 and the UPF_A 235 may be written with the symbols omitted, such as UPF.

[0038] [2. Configuration of Each Device] Next, the configuration of each device (UE, and / or access network device, and / or core network device) used in each embodiment will be described with reference to the drawings. Each device may be configured as physical hardware, as logical (virtual) hardware configured on general-purpose hardware, or as software. Furthermore, at least a part (including all) of the functions of each device may be configured as physical hardware, logical hardware, or software.

[0039] Note that each memory unit (memory unit_A340, memory unit_A440, memory unit_B540, memory unit_A640, memory unit_B740) in each device / function mentioned below is configured with, for example, a semiconductor memory, a solid state drive (SSD), a hard disk drive (HDD), etc. Furthermore, each memory unit can store not only information originally set at the time of shipment, but also various information transmitted and received between devices / functions other than the device / function itself (e.g., UE, and / or access network device, and / or core network device, and / or PDN, and / or DN). Furthermore, each memory unit can store identification information, control information, flags, parameters, etc. included in control messages transmitted and received in various communication procedures described below. Furthermore, each memory unit may store this information for each UE. Furthermore, when interworking between 5GS and EPS is performed, each memory unit can store control messages and user data transmitted and received between 5GS and / or devices / functions included in EPS. At this time, not only those transmitted and received via the N26 interface but also those transmitted and received without going through the N26 interface can be stored.

[0040] [2.1. Device configuration of UE] First, an example of the device configuration of UE (User Equipment) will be explained using Figure 3. The UE is composed of a control unit _A300, an antenna 310, a transceiver unit _A320, and a memory unit _A340. The control unit _A300, the transceiver unit _A320, and the memory unit _A340 are connected via a bus. The transceiver unit _A320 is connected to the antenna 310.

[0041] The control unit _A300 is a functional unit that controls the operation and functions of the entire UE. The control unit _A300 realizes various processing in the UE by reading and executing various programs stored in the memory unit _A340 as necessary.

[0042] The transceiver unit _A320 is a functional unit for wireless communication with a base station device (eNB or gNB) in the access network via an antenna. That is, the UE can use the transceiver unit _A320 to transmit and receive user data and / or control information between an access network device, and / or a core network device, and / or a PDN, and / or a DN.

[0043] Explaining in detail with reference to Figure 2, the UE can communicate with a base station device (eNB) in the E-UTRAN via the LTE-Uu interface by using the transceiver unit _A320. The UE can also communicate with a base station device (gNB) in the 5G AN by using the transceiver unit _A320. The UE can also transmit and receive AMF and NAS (Non-Access-Stratum) messages via the N1 interface by using the transceiver unit _A320. However, since the N1 interface is logical, in reality, communication between the UE and the AMF is performed via the 5G AN.

[0044] The memory unit _A340 is a functional unit for storing programs, user data, control information, etc. necessary for each operation of the UE.

[0045] The UE in this embodiment may be a 5G ProSe-enabled UE.

[0046] [2.2. gNB Device Configuration] Next, an example of the gNB device configuration will be described using Figure 4. The gNB is composed of a control unit _B500, an antenna 510, a network connection unit _B520, a transceiver unit _B530, and a memory unit _B540. The control unit _B500, the network connection unit _B520, the transceiver unit _B530, and the memory unit _B540 are connected via a bus. The transceiver unit _B530 is connected to the antenna 510.

[0047] The control unit _B500 is a functional unit that controls the operation and functions of the entire gNB. The control unit _B500 realizes various processes in the gNB by reading and executing various programs stored in the memory unit _B540 as necessary.

[0048] The network connection unit _B520 is a functional unit for the gNB to communicate with the AMF and / or UPF. That is, the gNB can send and receive user data and / or control information between the AMF and / or UPF using the network connection unit _B520.

[0049] The transceiver unit _B530 is a functional unit for wireless communication with the UE via the antenna 510. That is, the gNB can transmit and receive user data and / or control information to and from the UE using the transceiver unit _B530.

[0050] 2, a gNB in ​​a 5G AN can communicate with an AMF via an N2 interface by using a network connection unit _B 520, and can communicate with a UPF via an N3 interface, and can communicate with a UE by using a transceiver unit _B 530.

[0051] The memory unit _B540 is a functional unit for storing programs, user data, control information, etc. necessary for each operation of the gNB.

[0052] [2.3. AMF Device Configuration] Next, an example of the AMF device configuration will be explained using Figure 5. The AMF is composed of a control unit _B700, a network connection unit _B720, and a memory unit _B740. The control unit _B700, the network connection unit _B720, and the memory unit _B740 are connected via a bus. The AMF may be a node that handles the control plane.

[0053] The control unit _B700 is a functional unit that controls the operation and functions of the entire AMF. The control unit _B700 realizes various processing in the AMF by reading and executing various programs stored in the memory unit _B740 as needed.

[0054] The network connection unit _B720 is a functional unit for the AMF to connect to a base station device (gNB), and / or SMF, and / or PCF, and / or UDM, and / or SCEF in a 5G AN. In other words, the AMF can use the network connection unit _B720 to send and receive user data and / or control information between a base station device (gNB), and / or SMF, and / or PCF, and / or UDM, and / or SCEF in a 5G AN.

[0055] Explaining in detail with reference to FIG. 2, the AMF in the 5GCN can communicate with a gNB via the N2 interface by using the network connection unit _A620, can communicate with a UDM via the N8 interface, can communicate with an SMF via the N11 interface, and can communicate with a PCF via the N15 interface. The AMF can also send and receive NAS messages with a UE via the N1 interface by using the network connection unit _A620. However, since the N1 interface is logical, communication between the UE and the AMF is actually performed via a 5G AN. Furthermore, if the AMF supports the N26 interface, it can communicate with an MME via the N26 interface by using the network connection unit _A620.

[0056] The memory unit _B740 is a functional unit for storing programs, user data, control information, etc. necessary for each operation of the AMF.

[0057] The AMF has functions such as exchanging control messages with the RAN using the N2 interface, exchanging NAS messages with the UE using the N1 interface, encrypting and protecting the integrity of NAS messages, registration management (RM) functions, connection management (CM) functions, reachability management functions, mobility management functions for UEs, etc., transferring SM (Session Management) messages between the UE and the SMF, access authentication (Access Authorization) functions, security anchor functionality (SEA), security context management (SCM), a function to support the N2 interface for the N3IWF (Non-3GPP Interworking Function), a function to support sending and receiving NAS signals with the UE via the N3IWF, and a function to authenticate UEs connected via the N3IWF.

[0058] In addition, registration management manages the RM state for each UE. The RM state may be synchronized between the UE and the AMF. The RM state includes an unregistered state (RM-DEREGISTERED state) and a registered state (RM-REGISTERED state). In the RM-DEREGISTERED state, the UE is not registered with the network, and therefore the UE context in the AMF does not have valid location information or routing information for the UE, and therefore the AMF cannot reach the UE. In the RM-REGISTERED state, the UE is registered with the network, and therefore the UE can receive services that require registration with the network. Note that the RM state may also be expressed as a 5GMM state. In this case, the RM-DEREGISTERED state may be expressed as a 5GMM-DEREGISTERED state, and the RM-REGISTERED state may be expressed as a 5GMM-REGISTERED state.

[0059] In other words, 5GMM-REGISTERED may be a state in which each device has established a 5GMM context or a PDU session context. When each device is 5GMM-REGISTERED, UE_A10 may start transmitting and receiving user data and control messages, or may respond to paging. Furthermore, when each device is 5GMM-REGISTERED, UE_A10 may perform registration procedures other than the registration procedure for initial registration, and / or service request procedures.

[0060] Furthermore, 5GMM-DEREGISTERED may be a state in which each device has not established a 5GMM context, a state in which UE_A10's location information is not known to the network, or a state in which UE_A10 is unreachable from the network. Note that when each device is 5GMM-DEREGISTERED, UE_A10 may initiate a registration procedure or may establish a 5GMM context by performing the registration procedure.

[0061] In addition, connection management manages the CM state for each UE. The CM state may be synchronized between the UE and the AMF. The CM state includes a non-connected state (CM-IDLE state) and a connected state (CM-CONNECTED state). In the CM-IDLE state, the UE is in the RM-REGISTERED state but does not have a NAS signaling connection established with the AMF via the N1 interface. In the CM-IDLE state, the UE does not have an N2 interface connection or an N3 interface connection. On the other hand, in the CM-CONNECTED state, the UE has a NAS signaling connection established with the AMF via the N1 interface. In the CM-CONNECTED state, the UE may have an N2 interface connection and / or an N3 interface connection.

[0062] Furthermore, in connection management, the CM state in 3GPP access and the CM state in non-3GPP access may be managed separately. In this case, the CM state in 3GPP access may include a non-connected state in 3GPP access (CM-IDLE state over 3GPP access) and a connected state in 3GPP access (CM-CONNECTED state over 3GPP access). Furthermore, the CM state in non-3GPP access may include a non-connected state in non-3GPP access (CM-IDLE state over non-3GPP access) and a connected state in non-3GPP access (CM-CONNECTED state over non-3GPP access). Note that the non-connected state may be expressed as an idle mode, and the connected state mode may be expressed as a connected mode.

[0063] The CM state may be expressed as a 5GMM mode. In this case, the unconnected state may be expressed as a 5GMM-IDLE mode, and the connected state may be expressed as a 5GMM-CONNECTED mode. Furthermore, the unconnected state in 3GPP access may be expressed as a 5GMM-IDLE mode over 3GPP access, and the connected state in 3GPP access may be expressed as a 5GMM-CONNECTED mode over 3GPP access. Furthermore, the unconnected state in non-3GPP access may be expressed as 5GMM unconnected mode in non-3GPP access (5GMM-IDLE mode over non-3GPP access), and the connected state in non-3GPP access may be expressed as 5GMM connected mode in non-3GPP access (5GMM-CONNECTED mode over non-3GPP access). Note that the 5GMM unconnected mode may be expressed as idle mode, and the 5GMM connected mode may be expressed as connected mode.

[0064] In addition, one or more AMFs may be placed in the core network _B. In addition, the AMF may be a Network Function (NF) that manages one or more Network Slice Instances (NSIs). In addition, the AMF may be a Common Control Plane Network Function (CCNF) shared among multiple NSIs.

[0065] In addition, the N3IWF is a device and / or function located between the non-3GPP access and the 5GCN when the UE connects to the 5GS via the non-3GPP access.

[0066] [2.4. SMF Device Configuration] Next, an example of the SMF device configuration will be explained using Figure 5. The SMF is composed of a control unit _B700, a network connection unit _B720, and a memory unit _B740. The control unit _B700, the network connection unit _B720, and the memory unit _B740 are connected via a bus. The SMF may be a node that handles the control plane.

[0067] The control unit _B700 is a functional unit that controls the operation and functions of the entire SMF. The control unit _B700 realizes various processing in the SMF by reading and executing various programs stored in the memory unit _B740 as needed.

[0068] The network connection unit _B720 is a functional unit for the SMF to connect with the AMF, and / or UPF, and / or PCF, and / or UDM. In other words, the SMF can send and receive user data and / or control information between the AMF, and / or UPF, and / or PCF, and / or UDM using the network connection unit _B720.

[0069] Explaining in more detail with reference to Figure 2, the SMF in the 5GCN can communicate with the AMF via the N11 interface, with the UPF via the N4 interface, with the PCF via the N7 interface, and with the UDM via the N10 interface by using the network connection unit _A620.

[0070] The memory unit _B740 is a functional unit for storing programs, user data, control information, etc. required for each operation of the SMF.

[0071] The SMF has session management functions such as establishing, modifying, and releasing PDU sessions, IP address allocation for UEs and its management, UPF selection and control, UPF configuration for routing traffic to the appropriate destination, sending and receiving the SM portion of NAS messages, Downlink Data Notification, providing AN-specific (for each AN) SM information to be sent to the AN via the N2 interface via the AMF, determining the SSC mode (Session and Service Continuity mode) for the session, and roaming functions.

[0072] [2.5. UPF Device Configuration] Next, an example of the UPF device configuration will be explained using Figure 5. The UPF is composed of a control unit _B700, a network connection unit _B720, and a memory unit _B740. The control unit _B700, the network connection unit _B720, and the memory unit _B740 are connected via a bus. The UPF may be a node that handles the control plane.

[0073] The control unit _B700 is a functional unit that controls the operation and functions of the entire UPF.The control unit _B700 realizes various processing in the UPF by reading and executing various programs stored in the memory unit _B740 as needed.

[0074] The network connection unit _B720 is a functional unit for the UPF to connect to a base station device (gNB), and / or SMF, and / or DN within the 5G AN. In other words, the UPF can use the network connection unit _B720 to transmit and receive user data and / or control information between the base station device (gNB), and / or SMF, and / or DN within the 5G AN.

[0075] Explaining in more detail with reference to Figure 2, a UPF in a 5GCN can communicate with a gNB via the N3 interface, with an SMF via the N4 interface, with a DN via the N6 interface, and with other UPFs via the N9 interface by using the network connection unit _A620.

[0076] The memory unit _B740 is a functional unit for storing programs, user data, control information, etc. required for each operation of the UPF.

[0077] The UPF has functions such as an anchor point for intra-RAT mobility or inter-RAT mobility, an external PDU session point for interconnecting to DNs (i.e., a gateway between DNs and core network_B that forwards user data), packet routing and forwarding, an UL CL (Uplink Classifier) ​​function that supports routing of multiple traffic flows to one DN, a branching point function that supports multi-homed PDU sessions, a QoS (Quality of Service) processing function for the user plane, an uplink traffic verification function, downlink packet buffering, and a function to trigger downlink data notifications.

[0078] The UPF may also be a gateway for IP communication and / or non-IP communication. The UPF may also have a function for forwarding IP communication and a function for converting non-IP communication and IP communication. Furthermore, multiple gateways may be gateways that connect the core network_B to a single DN. The UPF may also have connectivity with other NFs and may be connected to each device via other NFs.

[0079] The user plane refers to user data transmitted and received between a UE and a network. The user plane may be transmitted and received using a PDN connection or a PDU session. Furthermore, in the case of EPS, the user plane may be transmitted and received using the LTE-Uu interface, and / or the S1-U interface, and / or the S5 interface, and / or the S8 interface, and / or the SGi interface. Furthermore, in the case of 5GS, the user plane may be transmitted and received via the interface between the UE and the NG RAN, and / or the N3 interface, and / or the N9 interface, and / or the N6 interface. Hereinafter, the user plane may be referred to as the U-Plane.

[0080] Furthermore, the control plane refers to control messages transmitted and received to control UE communications, etc. The control plane may be transmitted and received using a Non-Access-Stratum (NAS) signaling connection between the UE and the MME. Furthermore, in the case of EPS, the control plane may be transmitted and received using the LTE-Uu interface and the S1-MME interface. Furthermore, in the case of 5GS, the control plane may be transmitted and received using the interface between the UE and the NG RAN and the N2 interface. Hereinafter, the control plane may be referred to as the control plane or the C-Plane.

[0081] Furthermore, the U-Plane (User Plane; UP) may be a communication path for transmitting and receiving user data and may be composed of multiple bearers. Furthermore, the C-Plane (Control Plane; CP) may be a communication path for transmitting and receiving control messages and may be composed of multiple bearers.

[0082] [2.6. Description of Other Devices and / or Functions] Next, other devices and / or functions will be described.

[0083] Next, the network refers to at least a part of the access network _B, the core network _B, and the DN. Furthermore, one or more devices included in at least a part of the access network _B, the core network _B, and the DN may be referred to as a network or a network device.

[0084] That is, when a network transmits, receives, and / or processes messages, it may mean that devices in the network (network devices and / or control devices) transmit, receive, and / or process messages. Conversely, when a device in the network transmits, receives, receives, and / or processes messages, it may mean that the network transmits, receives, receives, and / or processes messages.

[0085] Furthermore, the network may refer to a public land mobile network (PLMN) or a non-public network (NPN). The network may also be referred to as a NW.

[0086] Next, a PLMN (Public Land Mobile Network) is a communication network that provides mobile radio communication services. A PLMN is a network managed by an operator, which is a communication service provider, and the operator can be identified by a PLMN ID. A PLMN that matches the MCC (Mobile Country Code) and MNC (Mobile Network Code) of a UE's IMSI (International Mobile Subscription Identity) may be a Home PLMN (HPLMN). Furthermore, the UE may store an Equivalent PLMN list in its USIM to identify one or more Equivalent PLMNs (EPLMNs). A PLMN different from the HPLMN and / or EPLMN may be a Visited PLMN (VPLMN). A PLMN to which the UE has successfully registered may be a Registered PLMN (RPLMN).

[0087] Next, PLMN selection may be a procedure for a UE to select a PLMN.

[0088] A registration area is a collection of one or more TAs assigned to a UE by the AMF. Note that while UE_A10 is moving within one or more TAs included in the registration area, it may be able to move without sending or receiving signals for tracking area update. In other words, a registration area may be a group of information indicating areas in which UE_A10 can move without performing a tracking area update procedure. A registration area may be identified by a TAI list consisting of one or more TAIs.

[0089] A tracking area is a single or multiple ranges managed by the core network that can be represented by the location information of UE_A10. A tracking area may be composed of multiple cells. Furthermore, a tracking area may be an area in which control messages such as paging are broadcast, or an area in which UE_A10 can move without performing a handover procedure. Furthermore, a tracking area may be a routing area, a location area, or anything similar. Hereinafter, a tracking area may also be a TA (Tracking Area).

[0090] Next, an SM (Session Management) message may be a NAS message used in a procedure for SM. The SM message may also be referred to as a NAS (Non-Access-Stratum) SM message. The SM message may be a control message transmitted and received between UE_A10 and SMF_A230 via AMF_A240.

[0091] Next, an MM (Mobility management) message may be a NAS message used in procedures for MM. The MM message may be a control message transmitted and received between UE_A10 and AMF_A240. Note that the MM message may also be referred to as a NAS MM message.

[0092] Next, a 5GS (5G System) service may be a connectivity service provided using the core network _B190.

[0093] Next, a non-5GS service may be a service other than a 5GS service.

[0094] Next, a PDU (Protocol Data Unit) session can be defined as an association between a DN providing a PDU connectivity service and a UE, but it may also be connectivity established between a UE and an external gateway. In 5GS, a UE can transmit and receive user data to and from a DN by establishing a PDU session via an access network _B and a core network _B. Here, this external gateway may be a UPF, SCEF, or the like. The UE can transmit and receive user data to and from a device such as an application server located in the DN using the PDU session. Note that each device (UE, and / or access network device, and / or core network device) may manage one or more pieces of identification information associated with a PDU session. Note that this identification information may include one or more of a DNN, a QoS rule, a PDU session type, an application identification information, an NSI identification information, an access network identification information, and an SSC mode, or may further include other information. Furthermore, when multiple PDU sessions are established, the identification information associated with each PDU session may be the same or different.

[0095] Next, the DNN (Data Network Name) may be identification information for identifying a core network and / or an external network such as a DN. Furthermore, the DNN can also be used as information for selecting a gateway such as a PGW / UPF that connects the core network B190.

[0096] PC5 is a reference point. PC5 may be a reference point between ProSe-enabled UEs. PC5 may be a reference point for 5G ProSe Direct Discovery, 5G ProSe Direct Communication, and 5G ProSe UE-to-Network Relay.

[0097] The PC5 path may be a communication path on the PC5. The PC5 path may also be a communication path between ProSe-enabled UEs. The PC5 path may also refer to the PC5. The PC5 path may also be referred to as a PC5 interface.

[0098] In addition, the PC5 link may be a PC5 path. The PC5 link may be referred to as a PC5 direct link, a 5G ProSe direct link, or a direct link.

[0099] Uu may be a radio interface, and Uu may be a radio interface between a 5G AN and a UE.

[0100] The Uu path may be a communication path on the Uu. The Uu path may also be a communication path between the 5G AN and the UE. The Uu path may also refer to the Uu. The Uu path may also be referred to as a Uu interface. The Uu path may also be referred to as a Uu link.

[0101] 5G Proximity-based Services (ProSe) may be services provided by 5GS based on UEs being in close proximity to each other. 5G ProSe may also be referred to as ProSe.

[0102] A 5G ProSe-enabled UE may be a UE that supports 5G ProSe requirements and related procedures. A 5G ProSe-enabled UE may also be referred to as a ProSe-capable UE.

[0103] The initiating UE may be the UE that sends the PROSE direct link establishment request acceptance message.

[0104] The target UE may be the UE that sends the PROSE direct link establishment acceptance message.

[0105] The remote UE may be a ProSe-enabled UE that communicates with the DN via a U2N relay UE.

[0106] The remote UE may be a 5G ProSe remote UE, a 5G ProSe layer-2 remote UE, or a 5G ProSe layer-3 remote UE. Note that the 5G ProSe layer-2 remote UE may be a 5G ProSe capable UE that communicates with the DN via a 5G ProSe layer-2 UE-to-network relay UE. Also, the 5G ProSe layer-3 remote UE may be a 5G ProSe capable UE that communicates with the DN via a 5G ProSe layer-3 UE-to-network relay UE.

[0107] A remote UE may also be referred to as a UE acting as a remote UE.

[0108] Also, the 5G ProSe layer-2 remote UE is a 5G ProSe-enabled UE that communicates with the DN via a 5G ProSe layer-2 U2N relay UE.

[0109] Also, a 5G ProSe layer-3 remote UE is a 5G ProSe-enabled UE that communicates with a DN via a 5G ProSe layer-3 UE-to-network relay UE.

[0110] A U2N (UE-to-network) relay UE may be a ProSe-enabled UE that provides functionality to support network connectivity for remote UEs.

[0111] The U2N relay UE may be a 5G ProSe U2N relay UE, a 5G ProSe layer-2 U2N relay UE, or a 5G ProSe layer-3 U2N relay UE. Note that the 5G ProSe layer-2 U2N relay UE may be a 5G ProSe capable UE that provides functionality to support network connectivity for 5G ProSe layer-2 remote UEs via a layer 2 protocol. Also, the 5G ProSe layer-3 U2N relay UE may be a 5G ProSe capable UE that provides functionality to support network connectivity for 5G ProSe layer-3 remote UEs via a layer 3 protocol.

[0112] A U2N relay UE may be referred to as a UE that operates as a U2N relay UE, a U2N relay UE may be referred to as a target relay UE, and a U2N relay UE may be referred to as a U2N relay.

[0113] In addition, 5G ProSe layer-2 U2N relay UE is a 5G ProSe-enabled UE that provides the functionality to support the network connectivity of 5G ProSe layer-2 remote UE via layer-2 protocol.

[0114] In addition, 5G ProSe layer-3 U2N relay UE is a 5G ProSe-enabled UE that provides the functionality to support the network connectivity of 5G ProSe layer-3 remote UE via layer-3 protocol.

[0115] 8 or 13 may be referred to as 5G ProSe UE-to-network relaying. 5G ProSe UE-to-network relaying may simply be referred to as relaying, 5G ProSe UE-to-network relay, or relay.

[0116] A U2N (UE-to-network) intermediate UE may be a ProSe-enabled UE that provides functionality to support connectivity between a remote UE and a U2N relay UE.

[0117] The U2N intermediate UE may be a 5G ProSe U2N intermediate UE, a 5G ProSe layer-2 U2N intermediate UE, or a 5G ProSe layer-3 U2N intermediate UE. Note that the 5G ProSe layer-2 U2N intermediate UE may be a 5G ProSe capable UE that provides functionality to support connection to a network for a 5G ProSe layer-2 remote UE via a layer 2 protocol and / or a 5G ProSe layer-2 UE-to-network relay UE. Also, the 5G ProSe layer-3 U2N intermediate UE may be a 5G ProSe capable UE that provides functionality to support connection to a network for a 5G ProSe layer-3 remote UE via a layer 3 protocol and / or a 5G ProSe layer-2 UE-to-network relay UE.

[0118] A U2N intermediate UE may also be referred to as a UE acting as a U2N intermediate UE.

[0119] In addition, the 5G ProSe layer-2 U2N intermediate UE may be a 5G ProSe-enabled UE that provides functionality to support connectivity between a 5G ProSe layer-2 remote UE and a 5G ProSe layer-2 U2N relay UE via a layer-2 protocol.

[0120] In addition, the 5G ProSe layer-3 U2N intermediate UE may be a 5G ProSe-enabled UE that provides functionality to support connectivity between a 5G ProSe layer-3 remote UE and a 5G ProSe layer-3 U2N relay UE via a layer-3 protocol.

[0121] There may be one or more U2N intermediate UEs. For example, in Fig. 9, a first U2N intermediate UE and a second U2N intermediate UE may be present, in order from the left, between the remote UE and the U2N relay UE.

[0122] Furthermore, a U2N intermediate UE may be referred to as a Relay participated in multi-hop U2N relaying or as a 5G ProSe Intermediate Relay. Furthermore, a U2N intermediate UE may be referred to as a multi-hop U2N relay UE or as a 5G ProSe multi-hop U2N relay UE. A U2N intermediate UE may be referred to as a 5G ProSe layer-2 multi-hop U2N relay UE or as a 5G ProSe layer-3 multi-hop U2N relay UE.

[0123] Additionally, the intermediate UE may be a U2U intermediate UE and / or a U2N intermediate UE.

[0124] An end UE may be a ProSe-enabled UE that communicates with another ProSe-enabled UE via a U2U relay UE. An end UE may be a ProSe-enabled UE that communicates with another ProSe-enabled UE via a U2U relay UE and / or a U2U intermediate UE.

[0125] The end UE may be a 5G ProSe end UE, a 5G ProSe layer-2 end UE, or a 5G ProSe layer-3 end UE. Note that the 5G ProSe layer-2 end UE may be a 5G ProSe capable UE that communicates with other 5G ProSe capable UEs via a 5G ProSe layer-2 UE-to-UE relay UE. Also, the 5G ProSe layer-3 end UE may be a 5G ProSe capable UE that communicates with other 5G ProSe capable UEs via a 5G ProSe layer-3 UE-to-UE relay UE.

[0126] An end UE may also be referred to as a UE acting as an end UE.

[0127] An end UE that sends a request message may be referred to as a source end UE, and an end UE that receives the request message may be referred to as a target end UE.

[0128] Also, a 5G ProSe layer-2 end UE is a 5G ProSe-enabled UE that communicates with another 5G ProSe-enabled UE via a 5G ProSe layer-2 U2U relay UE.

[0129] Also, a 5G ProSe layer-3 end UE is a 5G ProSe-enabled UE that communicates with another 5G ProSe-enabled UE via a 5G ProSe layer-3 U2U relay UE.

[0130] A U2U (UE-to-UE) relay UE may be a ProSe-enabled UE that provides functionality to support connectivity between two end UEs. A U2U relay UE may be a ProSe-enabled UE that provides functionality to support connectivity between two end UEs via a U2U intermediate UE.

[0131] The U2U relay UE may be a 5G ProSe U2U relay UE, a 5G ProSe layer-2 U2U relay UE, or a 5G ProSe layer-3 U2U relay UE. Note that the 5G ProSe layer-2 U2U relay UE may be a 5G ProSe capable UE that provides functionality to support a connection between two 5G ProSe layer-2 end UEs via a layer 2 protocol. Also, the 5G ProSe layer-3 U2U relay UE may be a 5G ProSe capable UE that provides functionality to support a connection between two 5G ProSe layer-3 end UEs via a layer 3 protocol.

[0132] The U2U relay UE may be a U2U intermediate UE. In this case, for example, in FIG. 11, the U2U relay UE may be the first U2U intermediate UE, and the U2U intermediate UE may be the second U2U intermediate UE.

[0133] A U2U relay UE may be referred to as a UE that operates as a U2U relay UE. A U2U relay UE may be referred to as a U2U relay.

[0134] In addition, 5G ProSe layer-2 U2U relay UE is a 5G ProSe-enabled UE that provides the capability to support connectivity between two 5G ProSe layer-2 end UEs via layer-2 protocols.

[0135] In addition, 5G ProSe layer-3 U2U relay UE is a 5G ProSe-enabled UE that provides the capability to support connectivity between two 5G ProSe layer-3 end UEs via layer-3 protocols.

[0136] In addition, the 5G ProSe layer-2 U2U relay UE may be a 5G ProSe-enabled UE that provides the capability to support connectivity between a source 5G ProSe layer-2 end UE and a 5G ProSe layer-2 U2U intermediate UE via a layer-2 protocol.

[0137] In addition, the 5G ProSe layer-3 U2U relay UE may be a 5G ProSe-enabled UE that provides the capability to support connectivity between a source 5G ProSe layer-3 end UE and a 5G ProSe layer-3 U2U intermediate UE via a layer-3 protocol.

[0138] 10 may be referred to as 5G ProSe UE-to-UE relay. 5G ProSe UE-to-network relay may simply be referred to as relaying, 5G ProSe UE-to-UE relaying, or relay.

[0139] A U2U (UE-to-UE) intermediate UE may be a ProSe-enabled UE that provides functionality to support connectivity between two end UEs. A U2U intermediate UE may be a ProSe-enabled UE that provides functionality to support connectivity between two end UEs via a U2U relay UE.

[0140] The U2U intermediate UE may be a 5G ProSe U2U intermediate UE, a 5G ProSe layer-2 U2U intermediate UE, or a 5G ProSe layer-3 U2U intermediate UE. Note that the 5G ProSe layer-2 U2U intermediate UE may be a 5G ProSe capable UE that provides functionality to support a connection between two 5G ProSe layer-2 end UEs via a layer 2 protocol and / or a 5G ProSe layer-2 U2U relay UE. Also, the 5G ProSe layer-3 U2U intermediate UE may be a 5G ProSe capable UE that provides functionality to support a connection between two 5G ProSe layer-3 end UEs via a layer 3 protocol and / or a 5G ProSe layer-3 U2U relay UE.

[0141] A U2U intermediate UE may also be referred to as a UE acting as a U2U intermediate UE.

[0142] The U2U intermediate UE may be a U2U relay UE. In this case, for example, in FIG. 11, the U2U relay UE may be the first U2U relay UE, and the U2U intermediate UE may be the second U2U relay UE.

[0143] In addition, the 5G ProSe layer-2 U2U intermediate UE may be a 5G ProSe-enabled UE that provides functionality to support connectivity between the target 5G ProSe layer-2 end UE and the 5G ProSe layer-2 U2U relay UE via a layer-2 protocol.

[0144] In addition, the 5G ProSe layer-3 U2U intermediate UE may be a 5G ProSe-enabled UE that provides the capability to support connectivity between the target 5G ProSe layer-3 end UE and the 5G ProSe layer-3 U2U relay UE via a layer-3 protocol.

[0145] Furthermore, the U2U intermediate UE may be referred to as a multi-hop U2U relay UE, a 5G ProSe multi-hop U2U relay UE, a 5G ProSe layer-2 multi-hop U2U relay UE, or a 5G ProSe layer-3 multi-hop U2U relay UE.

[0146] Also, there may be two or more U2U intermediate UEs. For example, as shown in Fig. 13, there may be a plurality of U2U intermediate UEs on a communication path from a source end UE to a target end UE.

[0147] Additionally, the intermediate UE may be a U2U intermediate UE and / or a U2N intermediate UE.

[0148] A discovery procedure may be a procedure that uses NR radio signals to detect and identify other nearby UEs.

[0149] The discovery procedure may be a 5G ProSe direct discovery procedure, a 5G ProSe UE-to-network relay discovery procedure, or a 5G ProSe UE-to-UE relay discovery procedure. The discovery procedure may also be referred to as 5G ProSe direct discovery or 5G ProSe discovery.

[0150] Multi-hop communication may refer to communication via two or more UEs, or a UE communicating to another UE or a network via two or more other UEs.

[0151] For example, the embodiments of Figures 9 and 11 may be multi-hop communications. In Figure 9, a remote UE connects to a network via two UEs, a U2N intermediate UE and a U2N relay UE. In Figure 11, a source end UE connects to a target UE via two UEs, a U2U relay UE and a U2U intermediate UE.

[0152] Also, in Fig. 9, the remote UE, and / or the U2N intermediate UE, and / or the U2N relay UE may support multi-hop. Also, in Fig. 11, the source end UE, and / or the U2U relay UE, and / or the U2U intermediate UE, and / or the target end UE may support multi-hop.

[0153] Multi-hop communication may be referred to as multi-hop, and a UE that supports multi-hop may be a multi-hop UE, and a UE that supports operating as a multi-hop UE.

[0154] The multi-hop communication may be UE-to-network relay multi-hop communication or UE-to-UE relay multi-hop communication.

[0155] Furthermore, a UE that supports multi-hop U2N relay UE may be a UE that supports operating as a U2N intermediate UE, and a UE that supports multi-hop U2U relay UE may be a UE that supports operating as a U2U intermediate UE.

[0156] Furthermore, a UE that supports multi-hop may be a UE that supports multi-hop U2N relay UE, or a UE that supports multi-hop U2U relay UE.

[0157] Supporting multi-hop or multi-hop functionality may mean supporting operation as a U2N intermediate UE and / or supporting operation as a U2U intermediate UE.

[0158] The application layer ID is an identifier that identifies a 5G ProSe-enabled UE within the context of a particular application.

[0159] The relay service code may be used in the case of U2N relay as well as in the case of U2U relay, where the relay service code may be used to identify the connection service provided by the U2U relay and the authorized users to whom the U2U relay provides the service.

[0160] The user info ID may be configured for Model A or Model B Group Member Discovery, 5G ProSe U2N Relay Discovery, and 5G ProSe U2U Relay Discovery for public safety or commercial applications based on the policy of the HPLMN or via the ProSe application server.

[0161] Congestion control may be a process performed when congestion occurs in a network. The congestion control may be NAS level mobility management congestion control.

[0162] ProSeP is the 5G ProSe policy.

[0163] The first timer may be a timer for a UE policy for a U2N intermediate UE. The first timer may indicate a validity period of the UE policy for a U2N intermediate UE.

[0164] The second timer may be a timer for a UE policy for the U2U intermediate UE. The second timer may indicate an effective time of the UE policy for the U2U intermediate UE.

[0165] The third timer may be a timer for a UE policy for the ProSe-enabled UE. The third timer may indicate a validity period of the UE policy for the ProSe-enabled UE.

[0166] [2.7. Description of Identification Information in This Embodiment] Next, the identification information transmitted, received, stored, and / or managed by each device in this embodiment will be described.

[0167] The first identification information may be information indicating that multi-hop is supported. The first identification information may be information indicating that multi-hop is not supported. The first identification information may be information indicating whether multi-hop is supported.

[0168] The first identification information may be information indicating that the UE supports operation as a multi-hop UE. The first identification information may be information indicating that the UE does not support operation as a multi-hop UE. The first identification information may be information indicating whether the UE supports operation as a multi-hop UE.

[0169] The first identification information may be information indicating that the UE supports multi-hop. The first identification information may be information indicating that the UE does not support multi-hop.

[0170] The first identification information may be information included in a 5GMM capability IE (Information Element).

[0171] The first identification information may indicate information indicated by the second identification information and / or the third identification information. The first identification information may include the second identification information and / or the third identification information.

[0172] Here, supporting multi-hop or multi-hop functionality may mean supporting operation as a U2N intermediate UE and / or supporting operation as a U2U intermediate UE.

[0173] The transmission and reception of first identification information may be interpreted as the transmission and reception of second identification information, or may be interpreted as the transmission and reception of third identification information.

[0174] The second identification information may be information indicating that the UE supports operating as a U2N intermediate UE. The second identification information may be information indicating that the UE does not support operating as a U2N intermediate UE. The second identification information may be information indicating whether the UE supports operating as a U2N intermediate UE. The second identification information may be indicated by the first identification information.

[0175] The second identification information may be information included in the 5GMM capability IE.

[0176] Transmitting and receiving the second identification information may be interpreted as transmitting and receiving the first identification information and / or the second identification information.

[0177] The third identification information may be information indicating that the UE supports operating as a U2U intermediate UE. The third identification information may be information indicating that the UE does not support operating as a U2U intermediate UE. The third identification information may be information indicating whether the UE supports operating as a U2U intermediate UE. The third identification information may be indicated by the first identification information.

[0178] The third identification information may be information included in the 5GMM capability IE.

[0179] Transmitting and receiving the third identification information may be interpreted as transmitting and receiving the first identification information and / or the third identification information.

[0180] The twentieth identification information may be a relay service code. The twentieth identification information may be information included in a relay service code IE (Information Element). The twentieth identification information may be information indicating a U2N relay UE. The twentieth identification information may be information indicating a U2N intermediate UE. The twentieth identification information may indicate a connection service requested by a remote UE. The twentieth identification information may indicate a connection service requested by a source end UE.

[0181] The twentieth identification information may be information for identifying a connection service provided by a U2N relay UE. The twentieth identification information may be information for identifying a connection service provided by a U2N intermediate UE. The twentieth identification information may be information for identifying a connection service provided by a U2U relay UE. The twentieth identification information may be information for identifying a connection service provided by a U2U intermediate UE.

[0182] The 30th identification information is a cause value. The 30th identification information may be a cause value included in a PC5 signaling protocol cause Information Element (IE). The 30th identification information may be a cause value included in a PC5 U2N relay UE failure cause IE. The 30th identification information may be a cause value included in a PC5 end UE failure cause IE. The 30th identification information may be a cause value indicating a congestion state. The 30th identification information may be "congestion situation".

[0183] Furthermore, the 30th identification information may be a cause value included in the PC5 end UE release cause IE.

[0184] The 31st identification information is a cause value. The 31st identification information may be a cause value included in a PC5 end UE release cause IE. The 31st identification information may be a PC5 protocol cause value. The 31st identification information may be a cause value indicating a failure from a U2U relay UE. The 31st identification information may be a cause value indicating a failure from a U2U intermediate UE. The 31st identification information may be a cause value indicating that a U2U relay UE is unavailable. The 31st identification information may be a cause value indicating that a U2U intermediate UE is unavailable. The 31st identification information may be a cause value indicating that multihop is unavailable. The 31st identification information may be "Failure from 5G ProSe UE-to-UE relay UE". The 31st identification information may be "Failure from 5G ProSe multihop UE-to-UE relay UE". The 31st identification information may be a cause value indicating that direct communication with a U2U intermediate UE has failed. The 31st identification information may be a reason value indicating that establishment of a direct link with the U2U intermediate UE is not permitted.

[0185] Furthermore, the 31st identification information may be a cause value included in the PC5 signaling protocol cause IE.

[0186] The 31st identification information may be a reason value indicating that the maximum number of links has been reached. The 31st identification information may be a reason value indicating that the maximum number of links allowed has been reached. The 31st identification information may be a reason value indicating that the U2U relay UE or the U2U intermediate UE has reached the maximum number of links allowed.

[0187] The 32nd identification information is a cause value. The 32nd identification information may be a cause value included in a PC5 end UE release cause IE. The 32nd identification information may also be a cause value included in a PC5 signaling protocol cause IE.

[0188] The 32nd identification information may be a cause value indicating a failure from the end UE. The 32nd identification information may be a cause value indicating that the end UE is unavailable. The 32nd identification information may be "Failure from 5G ProSe end UE".

[0189] The 33rd identification information may be a timer value for a backoff timer.

[0190] The 33rd identification may be a timer value for a back-off timer for a UE in a congested state. The 33rd identification may be a timer value for a back-off timer for congestion management.

[0191] The 33rd identification information may be a timer value of a timer for limiting initiation of a 5G ProSe direct link establishment procedure. For example, in FIG. 13 , the 33rd identification information may be a timer value of a timer for limiting initiation of a 5G ProSe direct link establishment procedure between a U2U relay UE and a U2U intermediate UE. Also, the 33rd identification information may be a timer value of a timer for limiting initiation of a 5G ProSe direct link establishment procedure between a target end UE and a U2U intermediate UE.

[0192] The 33rd identification information may be information that combines the 30th identification information and the 33rd identification information. The 33rd identification information may be information that combines the 31st identification information and the 33rd identification information. The 33rd identification information may be information that combines the 32nd identification information and the 33rd identification information.

[0193] [3. Description of Procedures Used in Each Embodiment] Next, procedures used in each embodiment will be described.

[0194] In each embodiment, as shown in FIG. 2, the HSS and UDM, PCF and PCRF, SMF and PGW-C, and UPF and PGW-U are each configured as the same device (i.e., the same physical hardware, the same logical hardware, or the same software). However, the contents described in this embodiment are also applicable to cases where these are configured as different devices (i.e., different physical hardware, different logical hardware, or different software). For example, data may be transmitted and received directly between these devices, or data may be transmitted and received via the N26 interface between the AMF and MME, or data may be transmitted and received via the UE.

[0195] [3.1. Registration Procedure] First, the registration procedure will be described with reference to FIG. 6. The registration procedure is a procedure in 5GS. In this chapter, this procedure refers to the registration procedure. The registration procedure is a procedure initiated by the UE to register with the access network _B and / or the core network _B and / or the DN. If the UE is not registered with the network, it can execute this procedure at any time, for example, when powered on. In other words, if the UE is in the deregistered state (RM-DEREGISTERED state), it can start this procedure at any time. Furthermore, each device (especially the UE and the AMF) can transition to the registered state (RM-REGISTERED state) based on the completion of the registration procedure. Note that the registration state may be managed by each device for each access. Specifically, each device may independently manage the registration state (registered state or unregistered state) for 3GPP access and the registration state for non-3GPP access.

[0196] The registration procedure may also be a registration procedure for initial registration, a registration procedure for mobility and periodic registration update, or simply referred to as registration.

[0197] Furthermore, the registration procedure may be a procedure for updating the location registration information of the UE in the network, and / or for the UE to periodically notify the network of the status of the UE, and / or for updating certain parameters related to the UE in the network.

[0198] It should be noted that this procedure may be performed multiple times, i.e., after this procedure is completed once, a new registration procedure may be performed.

[0199] In addition, the UE may perform a registration procedure after performing SNPN selection or PLMN selection.

[0200] The UE may initiate the registration procedure when performing mobility across TAs. In other words, the UE may initiate the registration procedure when it moves to a TA different from the TA indicated in the TA list it holds. Furthermore, the UE may initiate the registration procedure when it is necessary to update the context of each device due to disconnection or invalidation of a PDU session. Furthermore, the UE may initiate the registration procedure when there is a change in the capability information and / or preferences related to the establishment of the UE's PDU session. Furthermore, the UE may initiate the registration procedure periodically. Furthermore, the UE may initiate the registration procedure based on the completion of a UE configuration update procedure. However, the UE is not limited to these, and may perform the registration procedure at any timing.

[0201] Additionally, the UE may periodically initiate a registration procedure even when in a registered state.

[0202] Note that a registration procedure performed based on the mobility of the UE and a registration procedure performed periodically may be referred to as a registration procedure for mobility and registration update. In other words, the registration procedure for mobility and registration update may be a registration procedure performed based on the mobility of the UE, or may be a registration procedure performed periodically. Furthermore, the registration procedure for mobility and registration update may be a registration procedure performed based on a configuration update of the UE. Furthermore, the registration procedure for mobility and registration update may be a registration procedure performed to establish a communication path for transmitting and receiving user data. Furthermore, the registration procedure for mobility and registration update may be a registration procedure performed based on a request from the network. Furthermore, in other words, the registration procedure for mobility and registration update may be a registration procedure other than the registration procedure for initial registration.

[0203] Next, each step of the registration procedure will be described. Note that the registration procedure described below may be a registration procedure for initial registration, or a registration procedure for mobility and registration update.

[0204] First, the UE starts the registration procedure by transmitting a registration request message to the AMF (S800) (S802) (S804). Specifically, the UE transmits an RRC message including a registration request message to the 5G AN (or gNB) (S800). The registration request message is an NAS message. The RRC message may be a control message transmitted and received between the UE and the 5G AN (or gNB). The NAS message is processed in the NAS layer, and the RRC message is processed in the RRC layer. The NAS layer is a layer higher than the RRC layer.

[0205] Here, the UE may transmit one or more of the first to third pieces of identification information by including them in a registration request message and / or an RRC message. More specifically, the UE may transmit one or more of the first to third pieces of identification information by including them in a registration request message and / or an RRC message, or may transmit one or more of the first to third pieces of identification information by including them in a control message different from these, for example, a control message of a layer lower than the RRC layer (for example, a MAC layer, an RLC layer, or a PDCP layer).

[0206] Specifically, if the UE supports multi-hop, the UE may transmit first identification information indicating that the UE supports multi-hop. If the UE does not support multi-hop, the UE may transmit first identification information indicating that the UE does not support multi-hop.

[0207] If the UE supports operating as a multi-hop UE, it may transmit first identification information indicating that it supports multi-hop. If the UE does not support operating as a multi-hop UE, it may transmit first identification information indicating that it does not support multi-hop.

[0208] If the UE supports operating as a U2N intermediate UE, it may transmit second identification information indicating that it supports operating as a U2N intermediate UE. If the UE does not support operating as a U2N intermediate UE, it may transmit second identification information indicating that it does not support operating as a U2N intermediate UE.

[0209] If the UE supports operating as a U2U intermediate UE, it may transmit third identification information indicating that it supports operating as a U2U intermediate UE. If the UE does not support operating as a U2U intermediate UE, it may transmit third identification information indicating that it does not support operating as a U2U intermediate UE.

[0210] Note that the UE may send a registration request message to indicate to the network that the UE supports each function, or to indicate the UE's request.

[0211] Furthermore, the UE may include each piece of identification information in a registration request message and transmit it, thereby indicating to the network the contents indicated by the identification information included in the registration request message.

[0212] In addition, the UE may select and decide whether to include each identification information in the registration request message based on subscriber information, and / or network status, and / or user registration information, and / or context held by the UE, etc.

[0213] When a 5G AN (or gNB) receives an RRC message including a registration request message, it selects an AMF to which to forward the registration request message (S802). The 5G AN (or gNB) can select an AMF based on information included in the registration request message and / or the RRC message. The 5G AN (or gNB) extracts the registration request message from the received RRC message and forwards the registration request message to the selected AMF (S804).

[0214] Furthermore, when the AMF receives the first identification information, it may recognize that the UE supports or does not support multi-hop. When the AMF receives the first identification information, it may recognize that the UE supports or does not support operating as a multi-hop UE.

[0215] If the AMF receives the second identification information, it may recognize that the UE supports or does not support operating as a U2N intermediate UE.

[0216] If the AMF receives the third identification information, it may recognize that the UE supports or does not support operating as a U2U intermediate UE.

[0217] The AMF may determine whether the UE is authorized to use the 5G ProSe service based on one or more of the first to third identities. The AMF may approve the 5G ProSe service used by the UE based on one or more of the first to third identities.

[0218] The AMF may approve one or more of the first to third identities. The AMF may send one or more of the first to third identities to the PCF. The AMF may send the approved one or more of the first to third identities to the PCF.

[0219] When the AMF receives the registration request message, the AMF can perform a first condition determination. The first condition determination is for determining whether the network (or the AMF) accepts the UE's request. If the first condition determination is true, the AMF starts the procedure of (A) in Figure 6, while if the first condition determination is false, the AMF starts the procedure of (B) in Figure 6.

[0220] The first condition determination may be performed based on the reception of a registration request message, and / or subscriber information, and / or network capability information, and / or operator policy, and / or network status, and / or user registration information, and / or a context held by the AMF. For example, if the network permits the UE's request, the first condition determination may be true, and if the network does not permit the UE's request, the first condition determination may be false. Furthermore, if the network to which the UE is registered and / or a device within the network supports a function requested by the UE, the first condition determination may be true, and if the network does not support the function requested by the UE, the first condition determination may be false. Furthermore, if the identification information to be transmitted and received is permitted, the first condition determination may be true, and if the identification information to be transmitted and received is not permitted, the first condition determination may be false. The conditions for determining whether the first condition determination is true or false are not limited to the above-described conditions.

[0221] First, a case where the first condition determination is true will be described. In the procedure of (A) in Fig. 6, the AMF transmits a registration accept message to the UE via the 5G AN (or gNB) as a response message to the registration request message (S806). Note that the registration accept message is an NAS message transmitted and received on the N1 interface, but is transmitted and received between the UE and the 5G AN (gNB) as part of an RRC message.

[0222] The AMF may also indicate that the UE's request has been accepted by sending a registration acceptance message based on the received identification information, and / or subscription information, and / or network capability information, and / or operator policy, and / or network status, and / or user registration information, and / or context held by the AMF, etc.

[0223] Furthermore, the AMF may include information indicating that some of the UE's requests have been rejected in the registration acceptance message and send it, or may indicate the reason why some of the UE's requests have been rejected by sending the information indicating that some of the UE's requests have been rejected. Furthermore, the UE may recognize the reason why some of the UE's requests have been rejected by receiving the information indicating that some of the UE's requests have been rejected. Note that the reason for the rejection may be information indicating that the content indicated by the identification information received by the AMF is not permitted.

[0224] Next, the UE receives a registration acceptance message from the AMF via the 5G AN (gNB) (S806).

[0225] Here, the UE may recognize that the UE's request in the registration request message has been accepted by receiving the registration accept message.

[0226] Next, the UE may or may not send a registration completion message to the AMF via the 5G AN (gNB) as a response message to the registration acceptance message (S808). Here, the registration completion message is an NAS message transmitted and received on the N1 interface, but is included in an RRC message and transmitted and received between the UE and the 5G AN (gNB).

[0227] Next, the AMF may or may not receive a registration completion message via the 5G AN (gNB) (S808).

[0228] Each device completes the procedure in FIG. 6(A) based on the transmission and reception of the registration acceptance message and / or the registration completion message.

[0229] Next, a case where the first condition determination is false will be described. In the procedure of (B) of Fig. 6, the AMF transmits a registration reject message to the UE via the 5G AN (gNB) as a response message to the registration request message (S810). Here, the registration reject message is an NAS message transmitted and received on the N1 interface, but is transmitted and received between the UE and the 5G AN (gNB) as an RRC message.

[0230] The AMF may indicate that the UE's request via the registration request message has been rejected by sending a registration rejection message. Furthermore, the AMF may include information indicating the reason for the rejection in the registration rejection message and send it, or may indicate the reason for the rejection by sending the reason for the rejection. Furthermore, the UE may recognize the reason for the rejection of the UE's request by receiving information indicating the reason for the rejection of the UE's request. Note that the reason for the rejection may be information indicating that the content indicated by the identification information received by the AMF is not permitted.

[0231] Next, the UE receives a registration rejection message from the AMF via the 5G AN (gNB) (S810). By receiving the registration rejection message, the UE may recognize that the UE's request via the registration request message has been rejected.

[0232] Furthermore, if the UE does not receive a registration rejection message within a predetermined period of time after sending the registration request message, the UE may recognize that the UE's request has been rejected.

[0233] Based on the sending and receiving of the registration rejection message, each device completes the procedure (B) in this procedure.

[0234] The procedure in FIG. 6(B) may be started when the procedure in FIG. 6(A) is stopped.

[0235] Each device completes the registration procedure based on the completion of the procedure of (A) or (B) in Figure 6. Note that each device may transition to a state in which the UE is registered in the network (RM_REGISTERED state) based on the completion of the procedure of (A) in Figure 6. Also, each device may maintain a state in which the UE is not registered in the network (RM_DEREGISTERED state) based on the completion of the procedure of (B) in Figure 6, or may transition to a state in which the UE is not registered in the network.

[0236] Furthermore, each device may perform processing based on the information transmitted and received during the registration procedure based on the completion of the registration procedure. For example, if the device transmits or receives information indicating that some of the UE's requests have been rejected, the device may recognize the reason why the UE's requests have been rejected. Furthermore, each device may perform this procedure again based on the reason why the UE's requests have been rejected, or may perform the registration procedure for the core network_B or another cell.

[0237] Furthermore, the UE may store the identification information received with the registration accept message or registration reject message and may recognize the network's decision based on the completion of the registration procedure.

[0238] Furthermore, the UE may perform SNPN selection or PLMN selection based on the completion of the registration procedure.

[0239] [3.2 5G ProSe direct link establishment procedure] Next, the 5G ProSe direct link establishment procedure will be described with reference to Fig. 7. Hereinafter, the 5G ProSe direct link establishment procedure may be referred to as this procedure.

[0240] This chapter also explains the 5G ProSe direct link establishment procedure in each communication form shown in Figures 8 to 11.

[0241] The procedure may be for establishing a 5G ProSe direct link between two or more UEs, where the 5G ProSe direct link may be a Layer 2 link and / or a Layer 3 link.

[0242] Note that before this procedure is executed, each device may have performed the registration procedure, and / or the PDU session establishment procedure, and / or the discovery procedure one or more times.

[0243] This procedure may be performed multiple times, i.e., after this procedure is completed once, a new 5G ProSe direct link establishment procedure may be performed.

[0244] In this procedure, the UE that sends the request message may be referred to as the initiating UE. In other words, the initiating UE may be the UE that sends the PROSE direct link establishment request message. A UE other than the initiating UE may be referred to as the target UE. A UE that receives the request message may be referred to as the target UE. In other words, the target UE may be the UE that sends the PROSE direct link establishment accept message or the PROSE direct link establishment reject message.

[0245] 8, the remote UE may be the initiating UE and the U2N relay UE may be the target UE. That is, this procedure may be executed between the remote UE and the U2N relay UE.

[0246] In Figure 9, when the remote UE is the initiating UE, the U2N intermediate UE may be the target UE. Also, when the U2N intermediate UE is the initiating UE, the U2N relay UE may be the target UE. That is, this procedure may be performed between the remote UE and the U2N intermediate UE. Also, this procedure may be performed between the U2N intermediate UE and the U2N relay UE.

[0247] In Figure 10, when the source end UE is the initiating UE, the U2U relay UE may be the target UE. Also, when the U2U relay UE is the initiating UE, the target end UE may be the target UE. That is, this procedure may be performed between the source end UE and the U2U relay UE. Also, this procedure may be performed between the U2U relay UE and the target end UE.

[0248] In FIG. 11, when the source end UE is the initiating UE, the U2U relay UE may be the target UE. Also, when the U2U relay UE is the initiating UE, the U2U intermediate UE may be the target UE. Also, when the U2U intermediate UE is the initiating UE, the target end UE may be the target UE. That is, this procedure may be performed between the source end UE and the U2U relay UE. Also, this procedure may be performed between the U2U relay UE and the U2U intermediate UE. Also, this procedure may be performed between the U2U intermediate UE and the target end UE.

[0249] In addition, in FIG. 11, the U2U relay UE may be a U2U intermediate UE. Also, the U2U intermediate UE may be a U2U relay UE. For example, the U2U relay UE may be U2U intermediate UE #1, and the U2U intermediate UE may be U2U intermediate UE #2. Also, there may be two or more U2U intermediate UEs. For example, as shown in FIG. 13, there may be multiple U2U intermediate UEs on the communication path from the source end UE to the target end UE. In other words, the communication from the source end UE to the target end UE may be configured using multiple U2U intermediate UEs as shown in FIG. 13.

[0250] 9 and 11 show a communication mode with only one U2N intermediate UE or one U2U intermediate UE, but there may be two or more U2N intermediate UEs or two or more U2U intermediate UEs. In other words, although Figures 9 and 11 show a communication mode with two hops to the destination, this procedure may also be implemented when there are three or more hops to the destination.

[0251] In this procedure, the initiating UE and the target UE may transmit and receive control messages on PC5.

[0252] Also, for example, in FIG. 13, U2U intermediate UE #3 may perform a discovery procedure to search for a new U2U intermediate UE if the direct link between U2U intermediate UE #3 and U2U intermediate UE #5 is about to be broken.

[0253] Also, for example, in FIG. 13, U2U intermediate UE #3 may perform a discovery procedure to search for a new U2U intermediate UE when the direct link between U2U intermediate UE #3 and U2U intermediate UE #5 is about to be disconnected and when the direct link between U2U intermediate UE #3 and U2U intermediate UE #4 is about to be disconnected.

[0254] In addition, when the U2U intermediate UE receives an indication of radio link failure or an indication of PC5-RRC connection release from a lower layer, it may perform a discovery procedure to search for a new U2U intermediate UE.

[0255] Next, each step of this procedure will be described.

[0256] First, the initiating UE sends a PROSE DIRECT LINK ESTABLISHMENT REQUEST message to the target UE. Here, the initiating UE may send the PROSE DIRECT LINK ESTABLISHMENT REQUEST message including the 20th identification information. Furthermore, when the initiating UE retransmits the PROSE DIRECT LINK ESTABLISHMENT REQUEST message, the initiating UE may count the number of retransmissions. If the maximum number of permitted retransmissions is reached, the initiating UE may not send the PROSE DIRECT LINK ESTABLISHMENT REQUEST message. In other words, the initiating UE may retransmit the PROSE DIRECT LINK ESTABLISHMENT REQUEST message as long as the maximum number of permitted retransmissions is not reached. Furthermore, the initiating UE may send the PROSE DIRECT LINK ESTABLISHMENT REQUEST message including information on the number of hops.

[0257] In other words, in FIG. 8, the remote UE may send a PROSE direct link establishment request message to the U2N relay UE (S1200).

[0258] 9, a remote UE may send a PROSE direct link establishment request message to a U2N intermediate UE (S1400). In addition, the U2N intermediate UE may send a PROSE direct link establishment request message to a U2N relay UE (S1402).

[0259] In FIG. 9, the U2N intermediate UE may determine whether to send a PROSE direct link establishment request message based on the capabilities indicated by the first identification information for the U2N relay UE. In other words, if the U2N relay UE supports multi-hop, the U2N intermediate UE may send a PROSE direct link establishment request message. In other words, if the U2N relay UE does not support multi-hop, the U2N intermediate UE may not send a PROSE direct link establishment request message. Here, the U2N intermediate UE may receive the first identification information for the U2N relay UE from the network. In other words, the U2N intermediate UE may receive information on whether the U2N relay UE supports multi-hop from the network. The U2N intermediate UE may receive information on whether the U2N relay UE supports multi-hop during the registration procedure. In other words, the U2N intermediate UE may receive information on whether the U2N relay UE supports multi-hop in a registration accept message. In addition, the U2N intermediate UE may be informed by the U2N relay UE of whether the U2N relay UE supports multi-hop. The U2N intermediate UE may receive the information of whether the U2N relay UE supports multi-hop from the U2N relay UE during the discovery procedure.

[0260] 9, if a U2N relay UE supports multi-hop, the U2N intermediate UE may send a PROSE direct link establishment request message to the U2N relay UE. If multiple U2N relay UEs support multi-hop, the U2N intermediate UE may select one of the U2N relay UEs and send a PROSE direct link establishment request message to the selected U2N relay UE.

[0261] 10, the source end UE may send a PROSE direct link establishment request message to the U2U relay UE (S1600), and the U2U relay UE may send a PROSE direct link establishment request message to the target end UE (S1602).

[0262] 11, the source end UE may send a PROSE direct link establishment request message to the U2U relay UE (S1800). The U2U relay UE may also send a PROSE direct link establishment request message to the U2U intermediate UE (S1802). The U2U intermediate UE may also send a PROSE direct link establishment request message to the target end UE (S1804).

[0263] In FIG. 11 , the U2U relay UE may determine whether to send a PROSE direct link establishment request message based on the capabilities indicated by the first and / or third identification information for the U2N intermediate UE. In other words, if the U2U intermediate UE supports multi-hop, the U2U relay UE may send a PROSE direct link establishment request message. In other words, if the U2U intermediate UE does not support multi-hop, the U2U relay UE may not send a PROSE direct link establishment request message. Here, the U2U relay UE may receive the first and / or third identification information for the U2U intermediate UE from the network. In other words, the U2U relay UE may receive information on whether the U2U intermediate UE supports multi-hop from the network. The U2U relay UE may receive information on whether the U2U intermediate UE supports multi-hop during the registration procedure. In other words, the U2U relay UE may receive information on whether the U2U intermediate UE supports multi-hop in a registration accept message. In addition, the U2U relay UE may be informed of whether the U2U intermediate UE supports multi-hop by the U2U intermediate UE, and the U2U relay UE may receive the information on whether the U2U intermediate UE supports multi-hop from the U2U intermediate UE during the discovery procedure.

[0264] 11, if a U2U intermediate UE supports multi-hop, the U2U relay UE may send a PROSE direct link establishment request message to the U2U intermediate UE. If multiple U2U intermediate UEs support multi-hop, the U2U relay UE may select one of the U2U intermediate UEs and send a PROSE direct link establishment request message to the selected U2U intermediate UE.

[0265] Here, the initiating UE may include the 20th identification information.

[0266] In Figure 8, the initiating UE may set the relay service code of the target relay UE to the 20th identity. In other words, the remote UE may set the relay service code of the target relay UE to the 20th identity.

[0267] That is, when the 5G ProSe direct link establishment procedure is for 5G ProSe direct communication between a remote UE and a U2N relay UE, the initiating UE may set the relay service code of the target relay UE to the 20th identity. In other words, when a 5G ProSe direct link establishment procedure is initiated between a remote UE and a U2N relay UE, the initiating UE may set the relay service code of the target relay UE to the 20th identity.

[0268] In Figure 9, the initiating UE may set the relay service code of the target relay UE to the 20th identity. In other words, the remote UE may set the relay service code of the target relay UE to the 20th identity. Also, the U2N intermediate UE may set the relay service code of the target relay UE to the 20th identity.

[0269] That is, when the 5G ProSe direct link establishment procedure is for 5G ProSe direct communication between a remote UE and a U2N intermediate UE, the initiating UE may set the relay service code of the target relay UE to the 20th identity. In other words, when a 5G ProSe direct link establishment procedure is initiated between a remote UE and a U2N intermediate UE, the initiating UE may set the relay service code of the target relay UE to the 20th identity.

[0270] Also, when the 5G ProSe direct link establishment procedure is for 5G ProSe direct communication between a U2N intermediate UE and a U2N relay UE, the initiating UE may set the relay service code of the target relay UE to the 20th identity. In other words, when a 5G ProSe direct link establishment procedure is initiated between a U2N intermediate UE and a U2N relay UE, the initiating UE may set the relay service code of the target relay UE to the 20th identity. In other words, when a U2N intermediate UE receives a PROSE direct link establishment request message from the remote UE during a 5G ProSe direct link establishment procedure between a U2N intermediate UE and a U2N relay UE, and when a 5G ProSe direct link establishment procedure is initiated between the U2N intermediate UE and a U2N relay UE, the initiating UE may set the relay service code of the target relay UE to the 20th identity.

[0271] In addition, the initiating UE may set the 20th identification information to a relay service code indicating the connection service requested by the remote UE. In other words, the remote UE may set the 20th identification information to a relay service code indicating the connection service requested by the remote UE. In addition, the U2N intermediate UE may set the 20th identification information to a relay service code indicating the connection service requested by the remote UE.

[0272] That is, when the 5G ProSe direct link establishment procedure is for 5G ProSe direct communication between a remote UE and a U2N intermediate UE, the initiating UE may set the 20th identity to a relay service code indicating a connection service requested by the remote UE. In other words, when a 5G ProSe direct link establishment procedure is initiated between a remote UE and a U2N intermediate UE, the initiating UE may set the 20th identity to a relay service code indicating a connection service requested by the remote UE.

[0273] Furthermore, when the 5G ProSe direct link establishment procedure is for 5G ProSe direct communication between a U2N intermediate UE and a U2N relay UE, the initiating UE may set the 20th identity to a relay service code indicating a connection service requested by the remote UE. In other words, when a 5G ProSe direct link establishment procedure is initiated between a U2N intermediate UE and a U2N relay UE, the initiating UE may set the 20th identity to a relay service code indicating a connection service requested by the remote UE. In other words, when a U2N intermediate UE receives a PROSE direct link establishment request message from the remote UE during a 5G ProSe direct link establishment procedure between a U2N intermediate UE and a U2N relay UE, the initiating UE may set the 20th identity to a relay service code indicating a connection service requested by the remote UE.

[0274] 10, the initiating UE may set the relay service code indicating the connection service requested by the source end UE to the 20th identification information. In other words, the source end UE may set the relay service code indicating the connection service requested by the source end UE to the 20th identification information. In addition, the U2U relay UE may set the relay service code indicating the connection service requested by the source end UE to the 20th identification information.

[0275] That is, when the 5G ProSe direct link establishment procedure is for 5G ProSe direct communication between a source end UE and a U2U relay UE, the initiating UE may set the 20th identity to a relay service code indicating a connection service requested by the source end UE. In other words, when a 5G ProSe direct link establishment procedure is initiated between a source end UE and a U2U relay UE, the initiating UE may set the 20th identity to a relay service code indicating a connection service requested by the source end UE.

[0276] Furthermore, when the 5G ProSe direct link establishment procedure is for 5G ProSe direct communication between a target end UE and a U2U relay UE, the initiating UE may set the 20th identity to a relay service code indicating a connection service requested by the source end UE. In other words, when a 5G ProSe direct link establishment procedure is initiated between a target end UE and a U2U relay UE, the initiating UE may set the 20th identity to a relay service code indicating a connection service requested by the source end UE. In other words, when a U2U relay UE receives a PROSE direct link establishment request message from the source end UE in a 5G ProSe direct link establishment procedure between a source end UE and a U2U relay UE, and when a 5G ProSe direct link establishment procedure is initiated between the target end UE and the U2U relay UE, the initiating UE may set the 20th identity to a relay service code indicating a connection service requested by the source end UE.

[0277] In Figure 11, the initiating UE may set the relay service code of the target end UE to the 20th identification information. In other words, the source end UE may set the relay service code of the target end UE to the 20th identification information. In addition, the U2U relay UE may set the relay service code of the target end UE to the 20th identification information. In addition, the U2U intermediate UE may set the relay service code of the target end UE to the 20th identification information.

[0278] That is, when the 5G ProSe direct link establishment procedure is for 5G ProSe direct communication between a source end UE and a U2U relay UE, the initiating UE may set the relay service code of the target end UE to the 20th identity. In other words, when a 5G ProSe direct link establishment procedure is initiated between a source end UE and a U2U relay UE, the initiating UE may set the relay service code of the target end UE to the 20th identity.

[0279] Also, when the 5G ProSe direct link establishment procedure is for 5G ProSe direct communication between a U2U relay UE and a U2U intermediate UE, the initiating UE may set the relay service code of the target end UE to the 20th identity. In other words, when the 5G ProSe direct link establishment procedure is initiated between a U2U relay UE and a U2U intermediate UE, the initiating UE may set the relay service code of the target end UE to the 20th identity. In other words, when the U2U relay UE receives a PROSE direct link establishment request message from the source end UE in the 5G ProSe direct link establishment procedure between a source end UE and a U2U relay UE, and when the 5G ProSe direct link establishment procedure is initiated between the U2U relay UE and a U2U intermediate UE, the initiating UE may set the relay service code of the target end UE to the 20th identity.

[0280] Also, when the 5G ProSe direct link establishment procedure is for 5G ProSe direct communication between a U2U intermediate UE and a target end UE, the initiating UE may set the relay service code of the target end UE to the 20th identity. In other words, when a 5G ProSe direct link establishment procedure is initiated between a U2U intermediate UE and a target end UE, the initiating UE may set the relay service code of the target end UE to the 20th identity. In other words, when a U2U intermediate UE receives a PROSE direct link establishment request message from the U2U relay UE in a 5G ProSe direct link establishment procedure between a U2U relay UE and a U2U intermediate UE, and when a 5G ProSe direct link establishment procedure is initiated between the U2U intermediate UE and a target end UE, the initiating UE may set the relay service code of the target end UE to the 20th identity.

[0281] In addition, the initiating UE may set the 20th identification information to a relay service code indicating the connection service requested by the source end UE. In other words, the source end UE may set the 20th identification information to a relay service code indicating the connection service requested by the source end UE. In addition, the U2U relay UE may set the 20th identification information to a relay service code indicating the connection service requested by the source end UE. In addition, the U2U intermediate UE may set the 20th identification information to a relay service code indicating the connection service requested by the source end UE.

[0282] That is, when the 5G ProSe direct link establishment procedure is for 5G ProSe direct communication between a source end UE and a U2U relay UE, the initiating UE may set the 20th identity to a relay service code indicating a connection service requested by the source end UE. In other words, when a 5G ProSe direct link establishment procedure is initiated between a source end UE and a U2U relay UE, the initiating UE may set the 20th identity to a relay service code indicating a connection service requested by the source end UE.

[0283] Also, when the 5G ProSe direct link establishment procedure is for 5G ProSe direct communication between a U2U relay UE and a U2U intermediate UE, the initiating UE may set the 20th identity to a relay service code indicating a connection service requested by the source end UE. In other words, when a 5G ProSe direct link establishment procedure is initiated between a U2U relay UE and a U2U intermediate UE, the initiating UE may set the 20th identity to a relay service code indicating a connection service requested by the source end UE. In other words, when a U2U relay UE receives a PROSE direct link establishment request message from the source end UE in a 5G ProSe direct link establishment procedure between a source end UE and a U2U relay UE, and when a 5G ProSe direct link establishment procedure is initiated between the U2U relay UE and a U2U intermediate UE, the initiating UE may set the 20th identity to a relay service code indicating a connection service requested by the source end UE.

[0284] Also, when the 5G ProSe direct link establishment procedure is for 5G ProSe direct communication between a U2U intermediate UE and a target end UE, the initiating UE may set the 20th identity to a relay service code indicating a connection service requested by the source end UE. In other words, when a 5G ProSe direct link establishment procedure is initiated between a U2U intermediate UE and a target end UE, the initiating UE may set the 20th identity to a relay service code indicating a connection service requested by the source end UE. In other words, when a U2U intermediate UE receives a PROSE direct link establishment request message from the U2U relay UE in a 5G ProSe direct link establishment procedure between a U2U relay UE and a U2U intermediate UE, and when a 5G ProSe direct link establishment procedure is initiated between the U2U intermediate UE and a target end UE, the initiating UE may set the 20th identity to a relay service code indicating a connection service requested by the source end UE.

[0285] Next, the target UE receives a PROSE direct link establishment request message from the initiating UE. The target UE may also receive a PROSE direct link establishment request message from the initiating UE, the PROSE direct link establishment request message including the twentieth identity information.

[0286] In other words, in FIG. 8, the U2N relay UE may receive a PROSE direct link establishment request message from the remote UE (S1200).

[0287] 9, a U2N intermediate UE may receive a PROSE direct link establishment request message from a remote UE (S1400). Also, a U2N relay UE may receive a PROSE direct link establishment request message from the U2N intermediate UE (S1402).

[0288] 10, the U2U relay UE may receive a PROSE direct link establishment request message from the source end UE (S1600), and the target end UE may receive a PROSE direct link establishment request message from the U2U relay UE (S1602).

[0289] 11, the U2U relay UE may receive a PROSE direct link establishment request message from the source end UE (S1800). Also, the U2U intermediate UE may receive a PROSE direct link establishment request message from the U2U relay UE (S1802). Also, the target end UE may receive a PROSE direct link establishment request message from the U2U intermediate UE (S1804).

[0290] When the target UE receives the PROSE direct link establishment request message and / or the respective identification information, it may recognize the request of the initiating UE and may store the respective identification information.

[0291] Here, a case where there are two or more U2N intermediate UEs will be described. For example, in the case where UEs exist as shown in FIG. 9, a first U2N intermediate UE and a second U2N intermediate UE exist, from left to right, between the remote UE and the U2N relay UE. When a PROSE direct link establishment request message including the same source user info, the same ProSe identifier, and the same relay service code is received from the first U2N intermediate UE and the second U2N intermediate UE, the U2N relay UE may select one from the first U2N intermediate UE and the second U2N intermediate UE. In other words, when a PROSE direct link establishment request message including the same source user info, the same ProSe identifier, and the same relay service code is received from multiple U2N intermediate UEs, the U2N relay UE may select one from the multiple U2N intermediate UEs. In other words, if the procedure is for direct communication between a U2N intermediate UE and a U2N relay UE, and if the U2N relay UE receives PROSE direct link establishment request messages containing the same source user info, the same ProSe identifier, and the same relay service code from multiple U2N intermediate UEs, the U2N relay UE may select one of the multiple U2N intermediate UEs according to signal strength, local policy, and operator policy for each relay service code.

[0292] Next, (A) of FIG. 7, (A) of FIG. 8, (A) of FIG. 9, (A) of FIG. 10, and (A) of FIG. 11 will be described.

[0293] The target UE sends a PROSE DIRECT LINK ESTABLISHMENT ACCEPT message to the initiating UE, where the target UE may send the PROSE DIRECT LINK ESTABLISHMENT ACCEPT message if it accepts the PROSE DIRECT LINK ESTABLISHMENT REQUEST message from the initiating UE.

[0294] In other words, in FIG. 8, the U2N relay UE may send a PROSE direct link establishment accept message to the remote UE (S1202).

[0295] 9, the U2N relay UE may send a PROSE direct link establishment acceptance message to the U2N intermediate UE (S1404), and the U2N intermediate UE may send a PROSE direct link establishment acceptance message to the remote UE (S1406).

[0296] 10, the target end UE may send a PROSE direct link establishment acceptance message to the U2U relay UE (S1604), and the U2U relay UE may send a PROSE direct link establishment acceptance message to the source end UE (S1606).

[0297] 11, the target end UE may send a PROSE direct link establishment acceptance message to the U2U intermediate UE (S1806). In addition, the U2U intermediate UE may send a PROSE direct link establishment acceptance message to the U2U relay UE (S1808). In addition, the U2U relay UE may send a PROSE direct link establishment acceptance message to the source end UE (S1810).

[0298] The PROSE direct link establishment acceptance message may be a response message to the PROSE direct link establishment request message. The PROSE direct link establishment acceptance message may indicate acceptance of the PROSE direct link establishment request message.

[0299] The target UE may indicate acceptance of the request of one or more initiating UEs by sending a PROSE direct link establishment acceptance message and / or respective identification information.

[0300] In addition, the target UE may indicate whether it supports or does not support each function by sending a ProSe direct link establishment acceptance message and / or each identification information, or may indicate that it accepts the request of the initiating UE.

[0301] Furthermore, when multiple pieces of identification information are transmitted, the two or more pieces of identification information may be transmitted as one piece of identification information. Note that the information indicating support for each function and the information indicating a request for use of each function may be transmitted as the same identification information or may be transmitted as different identification information.

[0302] Furthermore, the target UE may decide whether to include each identification information in the PROSE direct link establishment acceptance message based on the received identification information, and / or subscriber information, and / or network capability information, and / or UE policy, and / or operator policy, and / or network status, and / or user registration information, and / or UE context, etc.

[0303] Next, the initiating UE receives a PROSE direct link establishment acceptance message from the target UE.

[0304] In other words, in FIG. 8, the remote UE may receive a PROSE direct link establishment acceptance message from the U2N relay UE (S1202).

[0305] 9, the U2N intermediate UE may receive a PROSE direct link establishment acceptance message from the U2N relay UE (S1404), and the remote UE may receive a PROSE direct link establishment acceptance message from the U2N intermediate UE (S1406).

[0306] 10, the U2U relay UE may receive a PROSE direct link establishment acceptance message from the target end UE (S1604), and the source end UE may receive a PROSE direct link establishment acceptance message from the U2U relay UE (S1606).

[0307] 11, the U2U intermediate UE may receive a PROSE direct link establishment acceptance message from the target end UE (S1806). Also, the U2U relay UE may receive a PROSE direct link establishment acceptance message from the U2U intermediate UE (S1808). Also, the source end UE may receive a PROSE direct link establishment acceptance message from the U2U relay UE (S1810).

[0308] Upon receiving the PROSE direct link establishment acceptance message and / or the respective identification information, the initiating UE may recognize that the initiating UE's request has been accepted and may store the respective identification information.

[0309] Next, (B) of FIG. 7, (B) of FIG. 8, (B) of FIG. 9, (B) of FIG. 10, and (B) of FIG. 11 will be described.

[0310] The target UE sends a PROSE DIRECT LINK ESTABLISHMENT REJECT message to the initiating UE (S1004). Here, the target UE may send the PROSE DIRECT LINK ESTABLISHMENT REJECT message when rejecting the PROSE DIRECT LINK ESTABLISHMENT REQUEST message from the initiating UE. The target UE may also send the PROSE DIRECT LINK ESTABLISHMENT REJECT message to the initiating UE, including one or more pieces of identification information among the 30th to 33rd pieces of identification information.

[0311] In other words, in FIG. 8, the U2N relay UE may send a PROSE direct link establishment rejection message to the remote UE (S1206).

[0312] 9, the U2N relay UE may send a PROSE direct link establishment rejection message to the U2N intermediate UE (S1410), and the U2N intermediate UE may send a PROSE direct link establishment rejection message to the remote UE (S1412).

[0313] In FIG. 9, the U2N intermediate UE may determine whether to send a PROSE direct link establishment rejection message (S1412) based on the capabilities indicated by the first identification information for the U2N relay UE. In other words, if the U2N relay UE does not support multi-hop, the U2N intermediate UE may send a PROSE direct link establishment rejection message to the remote UE. Also, if the U2N relay UE does not support multi-hop, the U2N intermediate UE may send a PROSE direct link establishment rejection message including a reason value indicating that the U2N relay UE does not support multi-hop. Also, if the U2N relay UE does not support multi-hop, the U2N intermediate UE may send a PROSE direct link establishment rejection message including a reason value indicating that there is no UE that supports multi-hop. Here, the U2N intermediate UE may receive the first identification information for the U2N relay UE from the network. In other words, the U2N intermediate UE may receive information on whether the U2N relay UE supports multi-hop from the network. The U2N intermediate UE may receive information about whether the U2N relay UE supports multi-hop during the registration procedure. In other words, the U2N intermediate UE may receive information about whether the U2N relay UE supports multi-hop in a registration accept message. The U2N intermediate UE may also be indicated by the U2N relay UE about whether the U2N relay UE supports multi-hop. The U2N intermediate UE may receive information about whether the U2N relay UE supports multi-hop from the U2N relay UE during the discovery procedure.

[0314] 10, the target end UE may send a PROSE direct link establishment rejection message to the U2U relay UE (S1608), and the U2U relay UE may send a PROSE direct link establishment rejection message to the source end UE (S1610).

[0315] 11, the target end UE may send a PROSE direct link establishment rejection message to the U2U intermediate UE (S1812). In addition, the U2U intermediate UE may send a PROSE direct link establishment rejection message to the U2U relay UE (S1814). In addition, the U2U relay UE may send a PROSE direct link establishment rejection message to the source end UE (S1816).

[0316] In FIG. 11 , the U2U relay UE may determine whether to send a PROSE direct link establishment rejection message (S1816) based on the capabilities indicated by the first and / or third identification information for the U2N intermediate UE. In other words, if the U2U intermediate UE does not support multi-hop, the U2U relay UE may send a PROSE direct link establishment rejection message. Also, if the U2U intermediate UE does not support multi-hop, the U2U relay UE may send a PROSE direct link establishment rejection message including a reason value indicating that the U2U intermediate UE does not support multi-hop. Also, if the U2U intermediate UE does not support multi-hop, the U2U relay UE may send a PROSE direct link establishment rejection message including a reason value indicating that there is no UE that supports multi-hop. Here, the U2U relay UE may receive the first and / or third identification information for the U2U intermediate UE from the network. In other words, the U2U relay UE may receive information on whether the U2U intermediate UE supports multi-hop from the network. The U2U relay UE may receive information about whether the U2U intermediate UE supports multi-hop during the registration procedure. In other words, the U2U relay UE may receive information about whether the U2U intermediate UE supports multi-hop in a registration accept message. In addition, the U2U relay UE may be indicated by the U2U intermediate UE about whether the U2U intermediate UE supports multi-hop. The U2U relay UE may receive information about whether the U2U intermediate UE supports multi-hop from the U2U intermediate UE during the discovery procedure.

[0317] Here, when in a congestion state, the target UE may send the 30th identification information and / or the 33rd identification information to the initiating UE.

[0318] 8, when the U2N relay UE is in a congestion state, the U2N relay UE may transmit the 30th identification information and / or the 33rd identification information. In other words, when the 5G ProSe direct link establishment request is for 5G ProSe UE-to-network relaying and the U2N relay UE is in a congestion state, the U2N relay UE may transmit the 30th identification information and / or the 33rd identification information. When a back-off timer for congestion management is running, the U2N relay UE may not accept the 5G ProSe direct link establishment request for relaying.

[0319] Also, in FIG. 8, if congestion management is active, the U2N relay UE may transmit the 30th identification information and / or the 33rd identification information. In other words, if the 5G ProSe direct link establishment request is for 5G ProSe UE-to-network relaying and congestion management is active, the U2N relay UE may transmit the 30th identification information and / or the 33rd identification information. Here, congestion management being active may be interpreted as congestion management being executed. If a back-off timer for congestion management is running, the U2N relay UE may not accept a 5G ProSe direct link establishment request for relaying.

[0320] 9, when the U2N relay UE is in a congestion state, the U2N relay UE may transmit the 30th identification information and / or the 33rd identification information. In other words, when the 5G ProSe direct link establishment request is for 5G ProSe UE-to-network relaying and the U2N relay UE is in a congestion state, the U2N relay UE may transmit the 30th identification information and / or the 33rd identification information. When a back-off timer for congestion management is running, the U2N relay UE may not accept the 5G ProSe direct link establishment request for relaying.

[0321] Also, in FIG. 9, if congestion management is active, the U2N relay UE may transmit the 30th identification information and / or the 33rd identification information. In other words, if the 5G ProSe direct link establishment request is for 5G ProSe UE-to-network relaying and congestion management is active, the U2N relay UE may transmit the 30th identification information and / or the 33rd identification information. Here, congestion management being active may be interpreted as congestion management being executed. If a back-off timer for congestion management is running, the U2N relay UE may not accept a 5G ProSe direct link establishment request for relaying.

[0322] 9, when the U2N intermediate UE receives the 30th identification information and / or the 33rd identification information, the U2N intermediate UE may transmit a PROSE direct link establishment rejection message including the received 30th identification information and / or the 33rd identification information to the remote UE (S1412). In other words, when the U2N intermediate UE receives a PROSE direct link establishment rejection message from the U2N relay UE, and / or when (b) this procedure is for direct communication between the remote UE and the U2N intermediate UE, and / or when (c) the U2N relay UE rejects the 5G ProSe direct link establishment procedure, and / or when (d) the PROSE direct link establishment rejection message includes the 33rd identification information, and / or when (e) the U2N intermediate UE reaches the maximum number of allowed retransmissions, the U2N intermediate UE may transmit a PROSE direct link establishment rejection message including the 30th identification information and / or the 33rd identification information received from the U2N relay UE to the remote UE.

[0323] Also, in FIG. 9, the U2N intermediate UE may send a PROSE direct link establishment rejection message including the 30th identification information and / or the 33rd identification information received from the U2N relay UE to the remote UE if (a) it receives a PROSE direct link establishment rejection message from the U2N relay UE, and / or (b) the U2N intermediate UE performs a 5G ProSe direct link establishment procedure for direct communication between the remote UE and the U2N intermediate UE, and / or (c) the U2N relay UE rejects the 5G ProSe direct link establishment procedure for direct communication between the U2N intermediate UE and the U2N relay UE, and / or (d) the PROSE direct link establishment rejection message includes the 30th and / or 33rd identification information, and / or (e) the U2N intermediate UE reaches the maximum number of allowed retransmissions.

[0324] Also, in Figure 9, when the U2N intermediate UE receives a PROSE direct link establishment rejection message (S1410) including the 30th and / or 33rd identification information from the U2N relay UE, it may include the 30th and / or 33rd identification information received from the U2N relay UE in a PROSE direct link establishment rejection message (S1412) and send it to the remote UE.

[0325] Also in Figure 9, when the U2N intermediate UE receives a PROSE direct link establishment rejection message (S1410) including the 30th and / or 33rd identification information from the U2N relay UE and the maximum number of permitted retransmissions has been reached, the U2N intermediate UE may include the 30th and / or 33rd identification information received from the U2N relay UE in a PROSE direct link establishment rejection message (S1412) and transmit the message to the remote UE. In other words, also in Figure 9, when the U2N intermediate UE receives a PROSE direct link establishment rejection message (S1410) including the 30th and / or 33rd identification information from the U2N relay UE and the maximum number of permitted retransmissions has not been reached, the U2N intermediate UE may retransmit the PROSE direct link establishment request message (S1402) to the U2N relay UE.

[0326] Also, in Figure 9, when the U2N intermediate UE receives a PROSE direct link establishment rejection message (S1410) including identification information No. 30 and / or No. 33 from the U2N relay UE, it may start a timer set to identification information No. 33.

[0327] 10, when the target end UE is in a congestion state, the target end UE may transmit the 30th identification information, the 32nd identification information, and the 33rd identification information. Also, when the U2U relay UE is in a congestion state, the U2U relay UE may transmit the 30th identification information, the 32nd identification information, and the 33rd identification information.

[0328] Also, in Figure 10, when the 30th identification information, and / or the 32nd identification information, and / or the 33rd identification information is received, the U2U relay UE may send a PROSE direct link establishment rejection message including the received 30th identification information, and / or the 32nd identification information, and / or the 33rd identification information to the source end UE (S1610). In other words, if the U2U relay UE receives a PROSE direct link establishment rejection message from the target end UE, and / or if (a) the procedure is for direct communication between the source end UE and the U2U relay UE, and / or if (b) the procedure is for direct communication between the source end UE and the U2U relay UE, and / or if (c) the target end UE rejects the 5G ProSe direct link establishment procedure, and / or if (d) the PROSE direct link establishment rejection message includes the 33rd identification information, and / or if (e) the U2U relay UE has reached the maximum number of allowed retransmissions, the U2U relay UE may send a PROSE direct link establishment rejection message including the received 30th identification information, and / or the 32nd identification information, and / or the 33rd identification information to the source end UE.

[0329] 11 , when the target end UE is in a congested state, the target end UE may transmit the 30th identification information, and / or the 31st identification information, and / or the 32nd identification information, and / or the 33rd identification information. Also, when the U2U relay UE is in a congested state, the U2U relay UE may transmit the 30th identification information, and / or the 31st identification information, and / or the 32nd identification information, and / or the 33rd identification information. Also, when the U2U intermediate UE is in a congested state, the U2U intermediate UE may transmit the 30th identification information, and / or the 31st identification information, and / or the 32nd identification information, and / or the 33rd identification information.

[0330] Also, in FIG. 11, when the 30th identification information, and / or the 31st identification information, and / or the 32nd identification information, and / or the 33rd identification information is received, the U2U relay UE and / or the U2U intermediate UE may send a PROSE direct link establishment rejection message including the received 30th identification information, and / or the 31st identification information, and / or the 32nd identification information, and / or the 33rd identification information to the source end UE (S1610).

[0331] In other words, if the U2U relay UE receives a PROSE direct link establishment rejection message from the U2U intermediate UE, and / or if (a) the procedure is for direct communication between the source end UE and the U2U relay UE, and / or if (b) the procedure is for direct communication between the source end UE and the U2U relay UE, and / or if (c) the target end UE rejects the 5G ProSe direct link establishment procedure, and / or if (d) the PROSE direct link establishment rejection message includes the 33rd identification information, and / or if (e) the U2U relay UE has reached the maximum number of allowed retransmissions, the U2U relay UE may send a PROSE direct link establishment rejection message to the source end UE including the received 30th identification information, and / or the 31st identification information, and / or the 32nd identification information, and / or the 33rd identification information.

[0332] In other words, if the U2U intermediate UE receives a PROSE direct link establishment rejection message from the target end UE, and / or if (a) the procedure is for direct communication between the U2U relay UE and the U2U intermediate UE, and / or if (c) the target end UE rejects the 5G ProSe direct link establishment procedure, and / or if (d) the PROSE direct link establishment rejection message includes the 33rd identification information, and / or if (e) the U2U intermediate UE has reached the maximum number of allowed retransmissions, the U2U intermediate UE may send a PROSE direct link establishment rejection message including the received 30th identification information, and / or the 31st identification information, and / or the 32nd identification information, and / or the 33rd identification information to the U2U relay UE.

[0333] The target UE may transmit the 31st identification information, the 32nd identification information, and / or the 33rd identification information to the initiating UE. Furthermore, if the target UE cannot accept a request from the initiating UE, it may transmit the 31st identification information, the 32nd identification information, and / or the 33rd identification information to the initiating UE. Furthermore, if the target UE cannot communicate with the initiating UE, it may transmit the 31st identification information, the 32nd identification information, and / or the 33rd identification information to the initiating UE. Furthermore, if multi-hop is not available, the target UE may transmit the 31st identification information, the 32nd identification information, and / or the 33rd identification information to the initiating UE. Furthermore, when the maximum number of allowed links is reached, the target UE may transmit the 31st identification information, the 32nd identification information, and / or the 33rd identification information to the initiating UE.

[0334] For example, in FIG. 10, if the target end UE cannot accept a request from the source end UE or the U2U relay UE, the target end UE may transmit the 32nd identity and / or the 33rd identity. Furthermore, if the target end UE cannot operate as a target end UE, the target end UE may transmit the 32nd identity and / or the 33rd identity. Furthermore, if the target end UE reaches the maximum number of allowed links, the target end UE may transmit the 32nd identity and / or the 33rd identity.

[0335] Furthermore, if the U2U relay UE cannot accept a request from the source end UE, the U2U relay UE may transmit the 31st identification information and / or the 33rd identification information. Furthermore, if the U2U relay UE cannot operate as a U2U relay UE, the U2U relay UE may transmit the 31st identification information and / or the 33rd identification information. Furthermore, if the U2U relay UE reaches the maximum number of allowed links, the U2U relay UE may transmit the 31st identification information and / or the 33rd identification information.

[0336] At this time, the U2U relay UE may send a PROSE direct link establishment rejection message (S1610) to the source end UE without sending a PROSE direct link establishment request message (S1602) to the target end UE. Furthermore, the U2U relay UE may send a PROSE direct link establishment rejection message (S1610) including the 31st identification information and / or the 33rd identification information.

[0337] 11, if the target end UE cannot accept a request from the source end UE, U2U relay UE, or U2U intermediate UE, the target end UE may transmit the 32nd identification information and / or the 33rd identification information. Furthermore, if the target end UE cannot operate as a target end UE, the target end UE may transmit the 32nd identification information and / or the 33rd identification information. Furthermore, if the target end UE reaches the maximum number of allowed links, the target end UE may transmit the 32nd identification information and / or the 33rd identification information.

[0338] Furthermore, if the U2U intermediate UE cannot accept a request from the source end UE or the U2U relay UE, the U2U intermediate UE may transmit the 31st identification information and / or the 33rd identification information. Furthermore, if the U2U intermediate UE cannot operate as a U2U intermediate UE, the U2U relay UE may transmit the 31st identification information and / or the 33rd identification information. Furthermore, if the U2U intermediate UE cannot use multi-hop, the U2U relay UE may transmit the 31st identification information and / or the 33rd identification information. Furthermore, if the U2U intermediate UE has reached the maximum number of allowed links, the U2U relay UE may transmit the 31st identification information and / or the 33rd identification information.

[0339] At this time, the U2U intermediate UE may send a PROSE direct link establishment rejection message (S1814) to the U2U relay UE without sending a PROSE direct link establishment request message (S1804) to the target end UE. Furthermore, the U2U intermediate UE may send a PROSE direct link establishment rejection message (S1814) including the 31st identification information and / or the 33rd identification information.

[0340] Furthermore, if the U2U relay UE cannot accept a request from the source end UE, the U2U relay UE may transmit the 31st identification information and / or the 33rd identification information. Furthermore, if the U2U relay UE cannot operate as a U2U relay UE, the U2U relay UE may transmit the 31st identification information and / or the 33rd identification information. Furthermore, if the U2U relay UE cannot use multi-hop, the U2U relay UE may transmit the 31st identification information and / or the 33rd identification information. Furthermore, if the U2U relay UE has reached the maximum number of allowed links, the U2U relay UE may transmit the 31st identification information and / or the 33rd identification information.

[0341] At this time, the U2U relay UE may send a PROSE direct link establishment rejection message (S1816) to the source end UE without sending a PROSE direct link establishment request message (S1802) to the U2U intermediate UE. Furthermore, the U2U relay UE may send a PROSE direct link establishment rejection message (S1816) including the 31st identification information and / or the 33rd identification information.

[0342] Furthermore, when the U2U intermediate UE receives the 32nd identification information from the target end UE and is unable to operate as a U2U intermediate UE, the U2U intermediate UE may transmit either the 31st identification information or the 32nd identification information. Furthermore, when the U2U intermediate UE receives the 32nd identification information from the target end UE and is unable to use multi-hop, the U2U intermediate UE may transmit either the 31st identification information or the 32nd identification information. Furthermore, the U2U intermediate UE may determine whether to transmit either the 31st identification information or the 32nd identification information based on a policy.

[0343] Furthermore, when the U2U intermediate UE transmits either the 31st identification information or the 32nd identification information, the U2U intermediate UE may also transmit the 33rd identification information. Here, the U2U intermediate UE may determine whether to transmit either the 31st identification information or the 32nd identification information based on the 33rd identification information. For example, if the timer value for the 32nd identification information is greater than the timer value for the 31st identification information, the U2U intermediate UE may transmit the 32nd identification information. For example, if the timer value for the 31st identification information is greater than the timer value for the 32nd identification information, the U2U intermediate UE may transmit the 31st identification information.

[0344] In other words, when the timer value of the timer for restricting the initiation of a 5G ProSe direct link establishment procedure between a U2U relay UE and a U2U intermediate UE is greater than the timer value of the timer for restricting the initiation of a 5G ProSe direct link establishment procedure between a target end UE and a U2U intermediate UE, the U2U intermediate UE may transmit the 31st identification information. Also, when the timer value of the timer for restricting the initiation of a 5G ProSe direct link establishment procedure between a U2U relay UE and a U2U intermediate UE is greater than the timer value of the timer for restricting the initiation of a 5G ProSe direct link establishment procedure between a U2U relay UE and a U2U intermediate UE, the U2U intermediate UE may transmit the 32nd identification information.

[0345] Furthermore, when the U2U intermediate UE receives the 32nd identification information from the target end UE and is unable to operate as a U2U intermediate UE, the U2U intermediate UE may transmit the 31st identification information. Furthermore, when the U2U intermediate UE receives the 32nd identification information from the target end UE and is unable to use multi-hop, the U2U intermediate UE may transmit the 31st identification information.

[0346] Furthermore, when the U2U intermediate UE receives the 32nd identification information from the target end UE and cannot operate as a U2U intermediate UE, the U2U intermediate UE may transmit the 32nd identification information. Furthermore, when the U2U intermediate UE receives the 32nd identification information from the target end UE and cannot use multi-hop, the U2U intermediate UE may transmit the 32nd identification information.

[0347] Furthermore, when the U2U intermediate UE receives the 32nd identification information from the target end UE and is unable to operate as a U2U intermediate UE, the U2U intermediate UE may transmit both the 31st and 32nd identification information. Furthermore, when the U2U intermediate UE receives the 32nd identification information from the target end UE and is unable to use multi-hop, the U2U intermediate UE may transmit both the 31st and 32nd identification information.

[0348] When transmitting the 31st identification information, the U2U intermediate UE may transmit 33rd identification information indicating a timer value of a timer for limiting initiation of a 5G ProSe direct link establishment procedure between the U2U relay UE and the U2U intermediate UE. Furthermore, when transmitting the 32nd identification information, the U2U intermediate UE may transmit 33rd identification information indicating a timer value of a timer for limiting initiation of a 5G ProSe direct link establishment procedure between the target end UE and the U2U intermediate UE.

[0349] The PROSE direct link establishment rejection message may be a response message to the PROSE direct link establishment request message. The PROSE direct link establishment rejection message may indicate that the PROSE direct link establishment request message is rejected.

[0350] The target UE may indicate its rejection of one or more initiating UE requests by sending a PROSE direct link establishment rejection message and / or respective identification information.

[0351] In addition, the target UE may indicate whether or not it supports each function, or may indicate that it rejects the initiating UE's request, by sending a ProSe direct link establishment rejection message and / or each identification information.

[0352] Furthermore, when multiple pieces of identification information are transmitted, the two or more pieces of identification information may be transmitted as one piece of identification information. Note that the information indicating support for each function and the information indicating a request for use of each function may be transmitted as the same identification information or may be transmitted as different identification information.

[0353] Furthermore, the target UE may decide whether to include each identification information in the PROSE direct link establishment rejection message based on the received identification information, and / or subscriber information, and / or network capability information, and / or UE policy, and / or operator policy, and / or network status, and / or user registration information, and / or UE context, etc.

[0354] Next, the initiating UE receives a PROSE direct link establishment rejection message from the target UE, where the initiating UE may receive the PROSE direct link establishment rejection message from the target UE, the PROSE direct link establishment rejection message including one or more of the 30th to 33rd identities.

[0355] In other words, in FIG. 8, the remote UE may receive a PROSE direct link establishment rejection message from the U2N relay UE (S1206).

[0356] 9, the U2N intermediate UE may receive a PROSE direct link establishment rejection message from the U2N relay UE (S1410), and the remote UE may receive a PROSE direct link establishment rejection message from the U2N intermediate UE (S1412).

[0357] 10, the U2U relay UE may receive a PROSE direct link establishment rejection message from the target end UE (S1608), and the source end UE may receive a PROSE direct link establishment rejection message from the U2U relay UE (S1610).

[0358] 11, the U2U intermediate UE may receive a PROSE direct link establishment rejection message from the target end UE (S1812). Also, the U2U relay UE may receive a PROSE direct link establishment rejection message from the U2U intermediate UE (S1814). Also, the source end UE may receive a PROSE direct link establishment rejection message from the U2U relay UE (S1816).

[0359] Upon receiving the PROSE direct link establishment rejection message and / or the respective identification information, the initiating UE may recognize that the initiating UE's request has been rejected and may store the respective identification information.

[0360] Specifically, when the initiating UE receives the 30th identification information and / or the 33rd identification information, the initiating UE may abort the procedure. Furthermore, when the initiating UE receives the 30th identification information and / or the 33rd identification information, the initiating UE may start a back-off timer set to the 33rd identification information.

[0361] 8, the remote UE may abort this procedure when it receives the 30th identification information, the 31st identification information, and / or the 33rd identification information. Also, the remote UE may start a back-off timer set to the 33rd identification information when it receives the 30th identification information, the 31st identification information, and / or the 33rd identification information.

[0362] 9, the U2N intermediate UE or the remote UE may abort this procedure when it receives the 30th identification information, the 31st identification information, and / or the 33rd identification information. Also, when it receives the 30th identification information, the 31st identification information, and / or the 33rd identification information, the U2N intermediate UE or the remote UE may start a back-off timer set to the 33rd identification information.

[0363] Also, in Figure 9, when the 30th identification information, and / or the 31st identification information, and / or the 33rd identification information is received, the U2N intermediate UE may send a PROSE direct link establishment rejection message including the received 30th identification information, and / or the 31st identification information, and / or the 33rd identification information to the remote UE (S1412). In other words, if the U2N intermediate UE receives a PROSE direct link establishment rejection message from the U2N relay UE, and / or if (a) the procedure is for direct communication between the remote UE and the U2N intermediate UE, and / or if (c) the U2N relay UE rejects the 5G ProSe direct link establishment procedure, and / or if (d) the PROSE direct link establishment rejection message includes the 33rd identification information, and / or if (e) the U2N intermediate UE has reached the maximum number of allowed retransmissions, the U2N intermediate UE may send a PROSE direct link establishment rejection message including the received 30th identification information, and / or the 31st identification information, and / or the 33rd identification information to the remote UE.

[0364] Also, in FIG. 9, the U2N intermediate UE may send a PROSE direct link establishment rejection message including the 30th identification information, the 31st identification information, and the 33rd identification information received from the U2N relay UE to the remote UE if (a) it receives a PROSE direct link establishment rejection message from the U2N relay UE, and / or (b) the U2N intermediate UE performs a 5G ProSe direct link establishment procedure for direct communication between the remote UE and the U2N intermediate UE, and / or (c) the U2N relay UE rejects the 5G ProSe direct link establishment procedure for direct communication between the U2N intermediate UE and the U2N relay UE, and / or (d) the PROSE direct link establishment rejection message includes the 30th and / or 31st and / or 33rd identification information, and / or (e) the U2N intermediate UE reaches the maximum number of allowed retransmissions.

[0365] Also, in Figure 9, when a U2N intermediate UE receives a PROSE direct link establishment rejection message (S1410) including identification information no. 30 and / or 31 and / or 33 from a U2N relay UE, the U2N intermediate UE may include the identification information no. 30 and / or 31 and / or 33 received from the U2N relay UE in a PROSE direct link establishment rejection message (S1412) and send it to the remote UE.

[0366] Also in Figure 9, when the U2N intermediate UE receives a PROSE direct link establishment rejection message (S1410) including the identification information of the 30th and / or 31st and / or 33rd from the U2N relay UE and the maximum number of permitted retransmissions has been reached, the U2N intermediate UE may include the identification information of the 30th and / or 31st and / or 33rd received from the U2N relay UE in the PROSE direct link establishment rejection message (S1412) and transmit the message to the remote UE. In other words, also in Figure 9, when the U2N intermediate UE receives a PROSE direct link establishment rejection message (S1410) including the identification information of the 30th and / or 31st and / or 33rd from the U2N relay UE and the maximum number of permitted retransmissions has not been reached, the U2N intermediate UE may retransmit the PROSE direct link establishment request message (S1402) to the U2N relay UE.

[0367] Also, in Figure 9, when the U2N intermediate UE receives a PROSE direct link establishment rejection message (S1410) including identification information 30 and / or 31 and / or 33 from the U2N relay UE, it may start a back-off timer with identification information 33 set.

[0368] 10, the U2U relay UE or the source end UE may abort this procedure when it receives the 30th identification information, the 32nd identification information, and / or the 33rd identification information. Also, when it receives the 30th identification information, the 32nd identification information, and / or the 33rd identification information, the U2U relay UE or the source end UE may start a back-off timer set to the 33rd identification information.

[0369] Also, in Figure 10, when the 30th identification information, and / or the 32nd identification information, and / or the 33rd identification information is received, the U2U relay UE may send a PROSE direct link establishment rejection message including the received 30th identification information, and / or the 32nd identification information, and / or the 33rd identification information to the source end UE (S1610). In other words, if the U2U relay UE receives a PROSE direct link establishment rejection message from the target end UE, and / or if (a) the procedure is for direct communication between the source end UE and the U2U relay UE, and / or if (b) the procedure is for direct communication between the source end UE and the U2U relay UE, and / or if (c) the target end UE rejects the 5G ProSe direct link establishment procedure, and / or if (d) the PROSE direct link establishment rejection message includes the 33rd identification information, and / or if (e) the U2U relay UE has reached the maximum number of allowed retransmissions, the U2U relay UE may send a PROSE direct link establishment rejection message including the received 30th identification information, and / or the 32nd identification information, and / or the 33rd identification information to the source end UE.

[0370] 11, the U2U intermediate UE, U2U relay UE, or source end UE may abort this procedure upon receiving the 30th identification information, and / or the 31st identification information, and / or the 32nd identification information, and / or the 33rd identification information. Furthermore, the U2U intermediate UE, U2U relay UE, or source end UE may start a back-off timer set to the 33rd identification information upon receiving the 30th identification information, and / or the 31st identification information, and / or the 32nd identification information, and / or the 33rd identification information.

[0371] Also, in FIG. 11, when the U2U intermediate UE receives the 30th identification information, and / or the 31st identification information, and / or the 32nd identification information, and / or the 33rd identification information, it may send a PROSE direct link establishment rejection message including the received 30th identification information, and / or the 31st identification information, and / or the 32nd identification information, and / or the 33rd identification information to the U2U relay UE (S1814). In other words, if the U2U intermediate UE receives a PROSE direct link establishment rejection message from the target end UE, and / or if (b) the procedure is for direct communication between the U2U intermediate UE and the U2U relay UE, and / or if (c) the target end UE rejects the 5G ProSe direct link establishment procedure, and / or if (d) the PROSE direct link establishment rejection message includes the 33rd identification information, and / or if (e) the U2U intermediate UE has reached the maximum number of allowed retransmissions, the U2U intermediate UE may send a PROSE direct link establishment rejection message including the received 30th identification information, and / or the 31st identification information, and / or the 32nd identification information, and / or the 33rd identification information to the U2U relay UE.

[0372] Also, in FIG. 11, when the 30th identification information, and / or the 31st identification information, and / or the 32nd identification information, and / or the 33rd identification information is received, the U2U relay UE may send a PROSE direct link establishment rejection message including the received 30th identification information, and / or the 31st identification information, and / or the 32nd identification information, and / or the 33rd identification information to the source end UE (S1816). In other words, if the U2U relay UE receives a PROSE direct link establishment rejection message from the U2U intermediate UE, and / or if (a) the procedure is for direct communication between the source end UE and the U2U relay UE, and / or if (b) the procedure is for direct communication between the source end UE and the U2U relay UE, and / or if (c) the target end UE rejects the 5G ProSe direct link establishment procedure, and / or if (d) the PROSE direct link establishment rejection message includes the 33rd identification information, and / or if (e) the U2U relay UE has reached the maximum number of allowed retransmissions, the U2U relay UE may send a PROSE direct link establishment rejection message to the source end UE including the received 30th identification information, and / or the 31st identification information, and / or the 32nd identification information, and / or the 33rd identification information.

[0373] In addition, the UE may not initiate a 5G ProSe direct link establishment procedure if the back-off timer is running. In other words, the UE may not send a PROSE direct link establishment request message if the back-off timer is running.

[0374] Furthermore, if the back-off timer is running, the UE may not retry the 5G ProSe direct link establishment procedure with a UE that has received a PROSE direct link establishment rejection message. For example, in FIG. 13, if U2U intermediate UE #3 receives a PROSE direct link establishment rejection message from U2U intermediate UE #5, the UE may not retry the 5G ProSe direct link establishment procedure with U2U intermediate UE #5 if the back-off timer is running. In other words, if U2U intermediate UE #3 receives a PROSE direct link establishment rejection message from U2U intermediate UE #5, the UE may retry the 5G ProSe direct link establishment procedure with U2U intermediate UE #1 and / or U2U intermediate UE #2 and / or U2U intermediate UE #4 if the back-off timer is running.

[0375] Also, in Figure 11, when the U2U relay UE receives a PROSE direct link establishment rejection message from the U2U intermediate UE, if the back-off timer is running, the U2U relay UE does not need to retry the 5G ProSe direct link establishment procedure with the U2U intermediate UE.

[0376] Furthermore, if the back-off timer is running, the UE may not initiate a 5G ProSe direct link establishment procedure with a UE that has received a PROSE direct link establishment rejection message. For example, in FIG. 13, if U2U intermediate UE #3 receives a PROSE direct link establishment rejection message from U2U intermediate UE #5, the UE may not initiate a 5G ProSe direct link establishment procedure with U2U intermediate UE #5 if the back-off timer is running. In other words, if U2U intermediate UE #3 receives a PROSE direct link establishment rejection message from U2U intermediate UE #5, the UE may initiate a 5G ProSe direct link establishment procedure with U2U intermediate UE #1 and / or U2U intermediate UE #2 and / or U2U intermediate UE #4 if the back-off timer is running.

[0377] Furthermore, the UE may initiate a 5G ProSe direct link establishment procedure when the back-off timer expires. In other words, the UE may transmit a PROSE direct link establishment request message when the back-off timer expires. Furthermore, the UE may initiate a 5G ProSe direct link establishment procedure at any timing when the back-off timer expires. In other words, the UE may transmit a PROSE direct link establishment request message at any timing when the back-off timer expires.

[0378] Furthermore, "when each piece of identification information is received" may be read as "when a PROSE direct link establishment rejection message is received."

[0379] The initiating UE may complete this procedure based on receiving a PROSE direct link establishment accept message or a PROSE direct link establishment reject message. The target UE may complete this procedure based on sending a PROSE direct link establishment accept message or a PROSE direct link establishment reject message. Each device may or may not establish a 5G ProSe direct link based on completion of this procedure. Each device may or may not recognize that a 5G ProSe direct link has been established based on completion of this procedure.

[0380] Note that the processing based on the reception of the identification information of the initiating UE and the target UE may be performed after the completion of this procedure.

[0381] Upon completion of this procedure, the initiating UE and the target UE may transmit and receive user data using the established 5G ProSe direct link.

[0382] In (A) of FIG. 8, the U2N relay UE may be in a state of being connected to the remote UE.

[0383] In addition, the remote UE may connect to the network via the U2N relay UE. In other words, the remote UE may connect to the network using a ProSe direct link between the remote UE and the U2N relay UE and a PDU session between the U2N relay UE and the network.

[0384] The U2N relay UE may also send a first control message to the network (S1204). More specifically, the U2N relay UE may send the first control message to notify the network that the remote UE is connected to the U2N relay UE. The U2N relay UE may also send the first control message to notify the network that the remote UE is disconnected from the U2N relay UE. The U2N relay UE may send the first control message to the network based on completion of the 5G ProSe direct link establishment procedure.

[0385] The first control message may be a remote UE report message. The first control message may be a message for notifying a network that the remote UE is connected to the U2N relay UE or that the remote UE is disconnected from the U2N relay UE. The first control message may be a message sent to the network to notify the connection or disconnection of the remote UE. Furthermore, the network may be an AMF and / or an SMF.

[0386] 9A, the U2N intermediate UE may be in a state of being connected to the remote UE, and the U2N relay UE may be in a state of being connected to the U2N intermediate UE.

[0387] In addition, the remote UE may connect to the network via a U2N intermediate UE and a U2N relay UE. In other words, the remote UE may connect to the network using a ProSe direct link between the remote UE and the U2N intermediate UE, a ProSe direct link between the U2N intermediate UE and the U2N relay UE, and a PDU session between the U2N relay UE and the network.

[0388] In addition, the U2N intermediate UE may connect to the network via the U2N relay UE. In other words, the U2N intermediate UE may connect to the network using a ProSe direct link between the U2N intermediate UE and the U2N relay UE and a PDU session between the U2N relay UE and the network.

[0389] The U2N relay UE may also send a second control message to the network (S1408). More specifically, the U2N relay UE may send the second control message to notify the network that the U2N intermediate UE is connected to the U2N relay UE. The U2N relay UE may also send the second control message to notify the network that the U2N intermediate UE is disconnected from the U2N relay UE. The U2N relay UE may send the second control message to the network based on completion of the 5G ProSe direct link establishment procedure.

[0390] In addition, the U2N relay UE may send a second control message to notify the network that the U2N intermediate UE connected to the remote UE is connected to the U2N relay UE, and in addition, the U2N relay UE may send a second control message to notify the network that the U2N intermediate UE connected to the remote UE is disconnected from the U2N relay UE.

[0391] The U2N relay UE may also send a second control message to notify the network that the remote UE is connected to the U2N relay UE via the U2N intermediate UE, and the U2N relay UE may also send a second control message to notify the network that the remote UE is disconnected from the U2N relay UE via the U2N intermediate UE.

[0392] The second control message may be a remote UE report message, a U2N intermediate UE report message, or a message with a different name. The second control message may be a message for notifying the network that the U2N intermediate UE is connected to the U2N relay UE or that the U2N intermediate UE is disconnected from the U2N relay UE. The second control message may be a message sent to the network to notify the connection or disconnection of the U2N intermediate UE. The second control message may be a message for notifying whether the remote UE is connected to the U2N intermediate UE. Furthermore, the network may be an AMF and / or an SMF.

[0393] [3.3 5G ProSe Direct Link Release Procedure] Next, the 5G ProSe direct link release procedure will be described with reference to Fig. 12. Hereinafter, the 5G ProSe direct link release procedure may be referred to as this procedure.

[0394] In addition, this chapter also describes the 5G ProSe direct link release procedure in Figure 13.

[0395] The procedure may be for releasing a 5G ProSe direct link between two or more UEs, where the 5G ProSe direct link may be a Layer 2 link and / or a Layer 3 link.

[0396] Furthermore, before this procedure is performed, each device may have performed the registration procedure, and / or PDU session establishment procedure, and / or discovery procedure, and / or 5G ProSe direct link establishment procedure one or more times.

[0397] This procedure may be performed multiple times, i.e., after this procedure is completed once, a new 5G ProSe direct link release procedure may be performed.

[0398] In this procedure, the UE that sends the request message may be referred to as the initiating UE. In other words, the initiating UE may be the UE that sends the PROSE direct link release request message. A UE other than the initiating UE may be referred to as the target UE. A UE that receives the request message may be referred to as the target UE. In other words, the target UE may be the UE that sends the PROSE direct link release accept message.

[0399] 13, the source end UE, each U2U intermediate UE, and the target end UE may be an initiating UE or a target UE. That is, a PROSE direct link release request message and a PROSE direct link release acceptance message may be transmitted and received between the UEs.

[0400] In this procedure, the initiating UE and the target UE may transmit and receive control messages on PC5.

[0401] 13, for example, when the direct link between U2U intermediate UE #3 and U2U intermediate UE #5 is about to be disconnected and when the direct link between U2U intermediate UE #3 and U2U intermediate UE #4 is about to be disconnected, U2U intermediate UE #3 may perform this procedure to release the direct link with other U2U intermediate UEs. In other words, in FIG. 13, when the direct link between U2U intermediate UE #3 and U2U intermediate UE #5 is about to be disconnected and when the direct link between U2U intermediate UE #3 and U2U intermediate UE #4 is about to be disconnected, U2U intermediate UE #3 may perform this procedure to release the direct link with U2U intermediate UE #1 and / or U2U intermediate UE #2.

[0402] In addition, if a U2U intermediate UE receives an indication of radio link failure or an indication of PC5-RRC connection release from a lower layer, it may perform this procedure to release a direct link with another U2U intermediate UE.

[0403] Furthermore, if the initiating UE is a UE operating as a U2U intermediate UE, and if one direct link between the initiating UE and another U2U intermediate UE is released, and if a direct link exists between the initiating UE and another U2U intermediate UE, the initiating UE does not need to initiate a 5G ProSe direct link release procedure with the other U2U intermediate UE.

[0404] Furthermore, if the initiating UE is a UE acting as a first U2U intermediate UE, and one direct link between the initiating UE and a second U2U intermediate UE is released, and a direct link between the initiating UE and a third U2U intermediate UE exists, the initiating UE may not initiate a 5G ProSe direct link release procedure with the third U2U intermediate UE. Here, the third U2U intermediate UE may be a UE between the first U2U intermediate UE and a target end UE. Also, the third U2U intermediate UE may be a UE between the first U2U intermediate UE and a source end UE.

[0405] Furthermore, if the initiating UE is a UE operating as a first U2U intermediate UE, and one direct link between the initiating UE and a second U2U intermediate UE is released, and a direct link between the initiating UE and a third U2U intermediate UE exists, and a direct link between the initiating UE and a fourth U2U intermediate UE exists, the initiating UE may not initiate a 5G ProSe direct link release procedure with the third U2U intermediate UE, and the initiating UE may not initiate a 5G ProSe direct link release procedure with the fourth U2U intermediate UE. Here, the third U2U intermediate UE may be a UE between the first U2U intermediate UE and a target end UE. Alternatively, the third U2U intermediate UE may be a UE between the first U2U intermediate UE and one or more U2U intermediate UEs. Also, the fourth U2U intermediate UE may be a UE between the first U2U intermediate UE and the source end UE, or may be a UE between the first U2U intermediate UE and one or more U2U intermediate UEs.

[0406] Furthermore, if the initiating UE is a UE operating as a U2U intermediate UE or an end UE, and if one direct link between the initiating UE and another U2U intermediate UE is released, and if the initiating UE has established two or more direct links with another U2U intermediate UE, the initiating UE does not need to initiate a 5G ProSe direct link release procedure with the other U2U intermediate UE.

[0407] Furthermore, if the initiating UE is a UE operating as a U2U intermediate UE or an end UE, and if one direct link between the initiating UE and another UE is released, and if the initiating UE has established two or more direct links with other UEs, the initiating UE does not need to initiate a 5G ProSe direct link release procedure with the other U2U intermediate UEs.

[0408] Furthermore, if the initiating UE is a UE operating as a U2U intermediate UE or end UE, and one direct link established in the initiating UE is released and two or more direct links established in the initiating UE remain, the initiating UE does not need to initiate a 5G ProSe direct link release procedure.

[0409] Furthermore, if the initiating UE is a UE operating as a U2U intermediate UE or an end UE, and if the initiating UE has established three or more direct links with other U2U intermediate UEs, and if one direct link between the initiating UE and other U2U intermediate UEs is released, the initiating UE does not need to initiate a 5G ProSe direct link release procedure with the other U2U intermediate UEs.

[0410] Furthermore, if the initiating UE is a UE operating as a U2U intermediate UE or an end UE, and if the initiating UE has established three or more direct links with other UEs, and if one direct link between the initiating UE and the other UEs is released, the initiating UE does not need to initiate a 5G ProSe direct link release procedure with the other U2U intermediate UEs.

[0411] Furthermore, if the initiating UE is a UE acting as a U2U intermediate UE or an end UE, and if the initiating UE has three or more established direct links and one direct link is released, the initiating UE does not need to initiate a 5G ProSe direct link release procedure.

[0412] For example, in FIG. 13, if the initiating UE is U2U intermediate UE #3, and if the direct link between the initiating UE and U2U intermediate UE #5 is released, and if a direct link exists between the initiating UE and U2U intermediate UE #4, the initiating UE does not need to initiate a 5G ProSe direct link release procedure with U2U intermediate UE #4.

[0413] Furthermore, if the initiating UE is a UE acting as a U2U intermediate UE or end UE, and if the initiating UE has two or more established direct links and one direct link is released, the initiating UE may initiate a 5G ProSe direct link release procedure.

[0414] Furthermore, if the initiating UE is a UE operating as a U2U intermediate UE or end UE, and one direct link established in the initiating UE is released and only one direct link established in the initiating UE remains, the initiating UE may initiate a 5G ProSe direct link release procedure.

[0415] For example, in FIG. 13, if the initiating UE is U2U intermediate UE #5, and if the direct link between the initiating UE and the target end UE is released, and if a direct link exists between the initiating UE and U2U intermediate UE #3, the initiating UE may initiate a 5G ProSe direct link release procedure with U2U intermediate UE #3.

[0416] Also, for example, in Figure 13, if the initiating UE is U2U intermediate UE #2, and the direct link between the initiating UE and U2U intermediate UE #3 is released, and a direct link exists between the initiating UE and U2U intermediate UE #1, the initiating UE may initiate a 5G ProSe direct link release procedure with U2U intermediate UE #1.

[0417] Next, each step of this procedure will be described.

[0418] First, the initiating UE sends a PROSE DIRECT LINK RELEASE REQUEST message to the target UE, and the initiating UE may also send the PROSE DIRECT LINK RELEASE REQUEST message to the target UE, including one or more of the 30th to 33rd identification information.

[0419] Here, when in a congestion state, the initiating UE may send the 30th identification information and / or the 33rd identification information to the target UE.

[0420] For example, in Fig. 13, when a target end UE is in a congestion state, the target end UE may transmit the 30th identification information, and / or the 31st identification information, and / or the 32nd identification information, and / or the 33rd identification information. Also, when a U2U intermediate UE is in a congestion state, the U2U intermediate UE may transmit the 30th identification information, and / or the 31st identification information, and / or the 32nd identification information, and / or the 33rd identification information.

[0421] Next, the target UE receives a PROSE direct link release request message from the initiating UE, where the target UE may receive the PROSE direct link release request message from the initiating UE, the PROSE direct link release request message including one or more of the 30th to 33rd identities.

[0422] When the target UE receives the PROSE direct link release request message and / or the respective identification information, it may recognize the request of the initiating UE and may store the respective identification information.

[0423] Specifically, the target UE may abort this procedure when it receives one or more of the identification information from the 30th to 33rd identification information, and may start a timer set to the 33rd identification information when it receives one or more of the identification information from the 30th to 33rd identification information.

[0424] Next, the target UE sends a PROSE DIRECT LINK RELEASE ACCEPT message to the initiating UE, where the target UE may send the PROSE DIRECT LINK RELEASE ACCEPT message if it accepts the PROSE DIRECT LINK RELEASE REQUEST message from the initiating UE.

[0425] The PROSE direct link release accept message may be a response message to the PROSE direct link release request message. The PROSE direct link release accept message may indicate acceptance of the PROSE direct link release request message.

[0426] The target UE may indicate acceptance of the request of one or more initiating UEs by sending a PROSE direct link release accept message and / or respective identification information.

[0427] In addition, the target UE may indicate whether it supports or does not support each function by sending a ProSe direct link release acceptance message and / or each identification information, or may indicate that it accepts the request of the initiating UE.

[0428] Furthermore, when multiple pieces of identification information are transmitted, the two or more pieces of identification information may be transmitted as one piece of identification information. Note that the information indicating support for each function and the information indicating a request for use of each function may be transmitted as the same identification information or may be transmitted as different identification information.

[0429] Furthermore, the target UE may decide whether to include each identification information in the PROSE direct link release accept message based on the received identification information, and / or subscriber information, and / or network capability information, and / or UE policy, and / or operator policy, and / or network status, and / or user registration information, and / or UE context, etc.

[0430] Next, the initiating UE receives a PROSE direct link release accept message from the target UE.

[0431] The initiating UE may complete this procedure based on receiving the PROSE direct link release accept message. The target UE may complete this procedure based on sending the PROSE direct link release accept message. Each device may release the established 5G ProSe direct link based on completion of this procedure. Each device may recognize that the established 5G ProSe direct link has been released based on completion of this procedure.

[0432] Note that the processing based on the reception of the identification information of the initiating UE and the target UE may be performed after the completion of this procedure.

[0433] [4. Modifications] The program that runs on the device according to this embodiment may be a program that controls a central processing unit (CPU) or the like to cause a computer to function so as to realize the functions of the embodiment according to this embodiment. The program or information handled by the program is temporarily stored in a volatile memory such as a random access memory (RAM), a non-volatile memory such as a flash memory, a hard disk drive (HDD), or other storage device system.

[0434] A program for realizing the functions of the embodiments according to the present invention may be recorded on a computer-readable recording medium. The program may be read into a computer system and executed. The term "computer system" as used herein refers to a computer system built into a device, including hardware such as an operating system and peripheral devices. The term "computer-readable recording medium" may also refer to a semiconductor recording medium, an optical recording medium, a magnetic recording medium, a medium that dynamically stores a program for a short period of time, or any other computer-readable recording medium.

[0435] Additionally, each functional block or feature of the device used in the above-described embodiments may be implemented or performed by an electrical circuit, such as an integrated circuit or multiple integrated circuits. The electrical circuit designed to perform the functions described herein may include a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or a combination thereof. The general-purpose processor may be a microprocessor, or a conventional processor, controller, microcontroller, or state machine. The electrical circuit may be composed of digital circuits or analog circuits. Furthermore, as advances in semiconductor technology emerge, one or more aspects of the present embodiments may utilize new integrated circuit technologies that replace current integrated circuits.

[0436] It should be noted that this example is not limited to the above-described embodiment. In the embodiment, one example of a device is described, but this example is not limited to this and can be applied to terminal devices or communication devices such as stationary or non-movable electronic devices installed indoors or outdoors, for example, AV equipment, kitchen equipment, cleaning / washing equipment, air conditioning equipment, office equipment, vending machines, and other household appliances.

[0437] Although the embodiment of this example has been described in detail above with reference to the drawings, the specific configuration is not limited to this example, and design modifications within the scope of the gist of this example are also included. Furthermore, this example can be modified in various ways within the scope of the claims, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of this example. Furthermore, configurations in which elements described in each of the above embodiments are substituted with elements that achieve the same effect are also included.

Claims

1. User Equipment (UE) including a transceiver unit and a controller, the UE operating as a first 5G Proximity based Services (ProSe) multi-hop UE-to-UE (U2U) relay UE, wherein in a first 5G ProSe direct link establishment procedure between the UE and a second 5G ProSe multi-hop U2U relay UE, the transceiver unit receives a first PROSE direct link establishment request message from the second 5G ProSe multi-hop U2U relay UE, and in a second 5G ProSe direct link establishment procedure between the UE and a target 5G ProSe end UE, the transceiver unit transmits a second PROSE direct link establishment request message to the target 5G ProSe end UE, and the transceiver unit receives a second PROSE direct link establishment rejection message from the target 5G ProSe end UE, the second PROSE direct link establishment rejection message including a first cause value and a timer value of a first back-off timer, If the timer value of the second back-off timer is greater than the timer value of the first back-off timer, the transceiver unit transmits, to the second 5G ProSe multi-hop U2U relay UE, a first PROSE direct link establishment rejection message including a second reason value and the timer value of the second back-off timer; If the timer value of the first back-off timer is greater than the timer value of the second back-off timer, the transceiver unit transmits, to the second 5G ProSe multi-hop U2U relay UE, a first PROSE direct link establishment rejection message including the first reason value and the timer value of the first back-off timer, wherein the first reason value indicates that a target 5G ProSe end UE is unavailable, the timer value of the first back-off timer is a timer value of a timer for limiting initiation of a second 5G ProSe direct link establishment procedure, the second reason value indicates that a 5G ProSe multi-hop U2U relay UE is unavailable, and the timer value of the second back-off timer is a timer value of a timer for limiting initiation of a second 5G ProSe direct link establishment procedure.a timer value of a timer for limiting the initiation of a ProSe direct link establishment procedure.

2. User Equipment (UE) including a transceiver unit and a controller, the UE operating as a first 5G Proximity based Services (ProSe) multi-hop UE-to-UE (U2U) relay UE, in a 5G ProSe direct link establishment procedure between the UE and a second 5G ProSe multi-hop U2U relay UE, the transceiver unit transmitting a PROSE direct link establishment request message to the second 5G ProSe multi-hop U2U relay UE, the transceiver unit receiving a PROSE direct link establishment rejection message including a cause value and a timer value of a back-off timer from the second 5G ProSe multi-hop U2U relay UE, the controller starting a timer using the timer value of the back-off timer, the transceiver unit not re-executing the 5G ProSe direct link establishment procedure with the second 5G ProSe multi-hop U2U relay UE if the timer is running, the cause value indicating that the 5G ProSe multi-hop U2U relay UE is unavailable, The UE, wherein the timer value of the backoff timer is a timer value of a timer for limiting the start of a 5G ProSe direct link establishment procedure.

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