First terminal device, second terminal device, and communication system

Abstract

To reduce power consumption in a communication system using terminal-to-terminal communication.SOLUTION: A communication system includes a plurality of terminal devices (202) that perform unicast communication in sidelink communication via a PC5 interface, where the plurality of terminal devices include a first terminal device (UE-TX), which is a terminal device on a transmitting side, and a second terminal device (UE-RX), which is a terminal device on a receiving side. The first terminal device determines a DRX (Discontinuous Reception) setting for the receiving operation of the second terminal device in unicast communication and transmits the DRX setting to the second terminal device.SELECTED DRAWING: Figure 32

Description

[Technical Field]

[0001] The present disclosure relates to wireless communication technology. [Background technology]

[0002] 3GPP (3rd Generation Partnership Project), a standardization organization for mobile communication systems, is considering a communication method called Long Term Evolution (LTE) for the wireless section and System Architecture Evolution (SAE) for the overall system configuration including the core network and radio access network (hereinafter collectively referred to as the network) (see, for example, Non-Patent Documents 1 to 5). This communication method is also called the 3.9G (3.9 Generation) system.

[0003] LTE uses OFDM (Orthogonal Frequency Division Multiplexing) for downlink and SC-FDMA (Single Carrier Frequency Division Multiple Access) for uplink as its access method. Unlike W-CDMA (Wideband Code Division Multiple Access), LTE does not include circuit switching and is only a packet communication method.

[0004] The decisions made by 3GPP regarding the frame configuration in the LTE system, as described in Non-Patent Document 1 (Chapter 5), will be explained using Figure 1. Figure 1 is an explanatory diagram showing the configuration of a radio frame used in an LTE communication system. In Figure 1, one radio frame is 10 ms. The radio frame is divided into 10 equally sized subframes. The subframe is divided into two equally sized slots. The first and sixth subframes of each radio frame include a downlink synchronization signal. The synchronization signals include a primary synchronization signal (P-SS) and a secondary synchronization signal (S-SS).

[0005] The decisions made by 3GPP regarding the channel configuration in the LTE system are described in Non-Patent Document 1 (Chapter 5). It is assumed that the same channel configuration as that of a non-CSG cell is used in a CSG (Closed Subscriber Group) cell.

[0006] The Physical Broadcast Channel (PBCH) is a channel for downlink transmission from a base station (hereinafter simply referred to as a "base station") to a communication terminal (hereinafter simply referred to as a "communication terminal") such as a mobile terminal (hereinafter simply referred to as a "mobile terminal"). A BCH transport block is mapped to four subframes in a 40 ms interval. There is no explicit signaling of the 40 ms timing.

[0007] The Physical Control Format Indicator Channel (PCFICH) is a channel for downlink transmission from a base station to a communication terminal. The PCFICH notifies the communication terminal of the number of Orthogonal Frequency Division Multiplexing (OFDM) symbols used for PDCCHs. The PCFICH is transmitted every subframe.

[0008] The Physical Downlink Control Channel (PDCCH) is a channel for downlink transmission from a base station to a communication terminal. The PDCCH reports resource allocation information for a Downlink Shared Channel (DL-SCH), which is one of the transport channels described below, resource allocation information for a Paging Channel (PCH), which is also one of the transport channels described below, and Hybrid Automatic Repeat reQuest (HARQ) information for the DL-SCH. The PDCCH carries an uplink scheduling grant. The PDCCH carries Acknowledgement (Ack) / Negative Acknowledgement (Nack), which are response signals to uplink transmissions. The PDCCH is also called an L1 / L2 control signal.

[0009] The Physical Downlink Shared Channel (PDSCH) is a channel for downlink transmission from a base station to a communication terminal. A Downlink Shared Channel (DL-SCH), which is a transport channel, and a PCH, which is also a transport channel, are mapped to the PDSCH.

[0010] A physical multicast channel (PMCH) is a channel for downlink transmission from a base station to communication terminals, and a multicast channel (MCH), which is a transport channel, is mapped to the PMCH.

[0011] The Physical Uplink Control Channel (PUCCH) is a channel for uplink transmission from a communication terminal to a base station. The PUCCH carries Ack / Nack, which are response signals to downlink transmissions. The PUCCH carries Channel State Information (CSI). The CSI consists of a Rank Indicator (RI), a Precoding Matrix Indicator (PMI), and a Channel Quality Indicator (CQI) report. The RI is information on the rank of the channel matrix in MIMO. The PMI is information on the precoding weight matrix used in MIMO. The CQI is quality information that indicates the quality of received data or the quality of the communication path. The PUCCH also carries a Scheduling Request (SR).

[0012] The Physical Uplink Shared Channel (PUSCH) is a channel for uplink transmission from a communication terminal to a base station. The Uplink Shared Channel (UL-SCH), which is one of the transport channels, is mapped to the PUSCH.

[0013] The Physical Hybrid ARQ Indicator Channel (PHICH) is a channel for downlink transmission from a base station to a communication terminal. The PHICH carries Ack / Nack, which are response signals to uplink transmission. The Physical Random Access Channel (PRACH) is a channel for uplink transmission from a communication terminal to a base station. The PRACH carries a random access preamble.

[0014] Downlink reference signals (RS) are symbols known in LTE communication systems. The following five types of downlink reference signals are defined: Cell-specific Reference Signal (CRS), MBSFN Reference Signal, UE-specific reference signal Demodulation Reference Signal (DM-RS), Positioning Reference Signal (PRS), and Channel State Information Reference Signal (CSI-RS). Measurement of the physical layer of a communication terminal includes measurement of the reference signal received power (RSRP).

[0015] Similarly, the uplink reference signal is a symbol known in LTE communication systems. Two types of uplink reference signals are defined: a data demodulation reference signal (DM-RS) and a sounding reference signal (SRS).

[0016] The transport channels described in Non-Patent Document 1 (Chapter 5) will be explained below. Among the downlink transport channels, a broadcast channel (BCH) is broadcast to the entire coverage of the base station (cell). The BCH is mapped to a physical broadcast channel (PBCH).

[0017] Retransmission control using HARQ (Hybrid ARQ) is applied to the Downlink Shared Channel (DL-SCH). DL-SCH can be broadcast to the entire coverage of a base station (cell). DL-SCH supports dynamic or semi-static resource allocation. Semi-static resource allocation is also called persistent scheduling. DL-SCH supports discontinuous reception (DRX) in communication terminals to reduce power consumption of communication terminals. DL-SCH is mapped to the Physical Downlink Shared Channel (PDSCH).

[0018] The Paging Channel (PCH) supports DRX in communication terminals to enable low power consumption in communication terminals. The PCH is required to broadcast to the entire coverage of the base station (cell). The PCH is mapped to physical resources such as the Physical Downlink Shared Channel (PDSCH) that can be dynamically used for traffic.

[0019] The Multicast Channel (MCH) is used for broadcasting to the entire coverage of a base station (cell). The MCH supports SFN combining of MBMS (Multimedia Broadcast Multicast Service) services (MTCH and MCCH) in multi-cell transmission. The MCH supports semi-static resource allocation. The MCH is mapped to the PMCH.

[0020] Among the uplink transport channels, the Uplink Shared Channel (UL-SCH) is subject to retransmission control using HARQ (Hybrid ARQ). The UL-SCH supports dynamic or semi-static resource allocation. The UL-SCH is mapped to the Physical Uplink Shared Channel (PUSCH).

[0021] The Random Access Channel (RACH) is limited to control information. The RACH is subject to collision risk. The RACH is mapped to the Physical Random Access Channel (PRACH).

[0022] We will explain HARQ. HARQ is a technology that improves the communication quality of a transmission channel by combining Automatic Repeat reQuest (ARQ) and Forward Error Correction. HARQ has the advantage that error correction works effectively through retransmission even on transmission channels where communication quality varies. In particular, by combining the reception results of the initial transmission and the retransmission when retransmitting, it is possible to achieve further quality improvement.

[0023] An example of a retransmission method will be explained below. If the receiving side is unable to decode the received data correctly, in other words, if a CRC (Cyclic Redundancy Check) error occurs (CRC=NG), the receiving side will send a "Nack" to the sending side. The sending side, having received the "Nack," will retransmit the data. If the receiving side is able to decode the received data correctly, in other words, if no CRC error occurs (CRC=OK), the receiving side will send an "Ack" to the sending side. The sending side, having received the "Ack," will send the next data.

[0024] The logical channels described in Non-Patent Document 1 (Chapter 6) will be explained below. The Broadcast Control Channel (BCCH) is a downlink channel for broadcast system control information. The BCCH, which is a logical channel, is mapped to the broadcast channel (BCH) or the downlink shared channel (DL-SCH), which are transport channels.

[0025] The Paging Control Channel (PCCH) is a downlink channel for transmitting paging information and changes to system information. The PCCH is used when the network does not know the cell location of the communication terminal. The PCCH, which is a logical channel, is mapped to the Paging Channel (PCH), which is a transport channel.

[0026] A Common Control Channel (CCCH) is a channel for transmission control information between a communication terminal and a base station. CCCH is used when a communication terminal does not have an RRC connection with the network. In the downlink direction, CCCH is mapped to a Downlink Shared Channel (DL-SCH), which is a transport channel. In the uplink direction, CCCH is mapped to an Uplink Shared Channel (UL-SCH), which is a transport channel.

[0027] The Multicast Control Channel (MCCH) is a downlink channel for point-to-multipoint transmission. The MCCH is used to transmit MBMS control information for one or several MTCHs from the network to communication terminals. The MCCH is used only by communication terminals receiving MBMS. The MCCH is mapped to the Multicast Channel (MCH), which is a transport channel.

[0028] A dedicated control channel (DCCH) is a channel that transmits dedicated control information between a communication terminal and a network on a one-to-one basis. The DCCH is used when the communication terminal is in an RRC connection. The DCCH is mapped to an uplink shared channel (UL-SCH) in the uplink and to a downlink shared channel (DL-SCH) in the downlink.

[0029] A Dedicated Traffic Channel (DTCH) is a one-to-one communication channel for transmitting user information to an individual communication terminal. DTCH exists in both uplink and downlink. In uplink, DTCH is mapped to an uplink shared channel (UL-SCH) and in downlink, it is mapped to a downlink shared channel (DL-SCH).

[0030] The Multicast Traffic Channel (MTCH) is a downlink channel for transmitting traffic data from the network to communication terminals. The MTCH is a channel used only by communication terminals receiving MBMS. The MTCH is mapped to the Multicast Channel (MCH).

[0031] CGI stands for Cell Global Identifier. ECGI stands for E-UTRAN Cell Global Identifier. Closed Subscriber Group (CSG) cells are introduced in LTE, LTE-A (Long Term Evolution Advanced) (described below), and UMTS (Universal Mobile Telecommunication System).

[0032] The location of a communication terminal is tracked in units of an area consisting of one or more cells. Location tracking is performed to track the location of the communication terminal even when it is in standby mode and to enable the communication terminal to be called, in other words, to allow the communication terminal to receive calls. The area used for tracking the location of this communication terminal is called a tracking area.

[0033] 3GPP is also working on the development of the Long Term Evolution Advanced (LTE-A) standard as Release 10 (see Non-Patent Documents 3 and 4). LTE-A is based on the LTE wireless communication system, and is configured by adding several new technologies to it.

[0034] In the LTE-A system, carrier aggregation (CA) is being considered, which aggregates two or more component carriers (CCs) (also called "aggregation") to support wider frequency bandwidths (transmission bandwidths) up to 100 MHz. CA is described in Non-Patent Document 1.

[0035] When CA is configured, the UE has only one RRC connection with the network (NW). In the RRC connection, one serving cell provides NAS mobility information and security input. This cell is called the primary cell (PCell). In the downlink, the carrier corresponding to the PCell is the downlink primary component carrier (DL PCC). In the uplink, the carrier corresponding to the PCell is the uplink primary component carrier (UL PCC).

[0036] Depending on the UE's capabilities, a secondary cell (SCell) is configured to form a serving cell set together with the PCell. In the downlink, the carrier corresponding to the SCell is the downlink secondary component carrier (DL SCC). In the uplink, the carrier corresponding to the SCell is the uplink secondary component carrier (UL SCC).

[0037] A set of serving cells, which includes one PCell and one or more SCells, is configured for one UE.

[0038] Furthermore, new technologies for LTE-A include wider bandwidth extension and Coordinated Multiple Point transmission and reception (CoMP) technology. CoMP, which is being considered for LTE-A by 3GPP, is described in Non-Patent Document 1.

[0039] Furthermore, in order to handle future massive traffic volumes, 3GPP is considering using small eNBs (hereinafter sometimes referred to as "small-scale base station devices") that configure small cells. For example, technologies are being considered that aim to increase communication capacity by installing a large number of small eNBs and configuring a large number of small cells to improve frequency utilization efficiency. Specifically, there is dual connectivity (abbreviated as DC), in which a UE connects to two eNBs to communicate. DC is described in Non-Patent Document 1.

[0040] Of the eNBs that perform dual connectivity (DC), one may be referred to as a "master eNB (abbreviated as MeNB)" and the other as a "secondary eNB (abbreviated as SeNB)."

[0041] Mobile network traffic volume is on the rise, and communication speeds are also increasing. Once LTE and LTE-A are fully operational, communication speeds are expected to increase even further.

[0042] Furthermore, in response to the increasing sophistication of mobile communications, fifth-generation (hereinafter sometimes referred to as "5G") wireless access systems are being considered, with the goal of launching services after 2020. For example, in Europe, an organization called METIS has compiled requirements for 5G (see Non-Patent Document 5).

[0043] The requirements for a 5G wireless access system are that it will have 1,000 times the system capacity, 100 times the data transmission speed, one-tenth (1 / 10) the data processing delay, and 100 times the number of simultaneous connections of communication terminals compared to an LTE system, while also achieving further reductions in power consumption and lower equipment costs.

[0044] To meet these demands, 3GPP is currently working on 5G standards as Release 15 (see Non-Patent Documents 6 to 19). 5G wireless access technology is called "New Radio Access Technology" ("New Radio" is abbreviated as "NR").

[0045] The NR system is being developed based on the LTE system and LTE-A system, but the following changes and additions have been made to the LTE system and LTE-A system.

[0046] The NR access method uses OFDM in the downlink direction and OFDM and DFT-s-OFDM (DFT-spread-OFDM) in the uplink direction.

[0047] NR allows the use of higher frequencies than LTE in order to improve transmission speeds and reduce processing delays.

[0048] In NR, cell coverage is ensured by forming a narrow beam-shaped transmission and reception range (beamforming) and changing the direction of the beam (beam sweeping).

[0049] The NR frame structure supports various subcarrier spacings, i.e., various numerologies. In NR, regardless of the numerology, one subframe is 1 millisecond and one slot consists of 14 symbols. The number of slots included in one subframe is one in a numerology with a subcarrier spacing of 15 kHz, but increases in proportion to the subcarrier spacing in other numerologies (see Non-Patent Document 13 (TS38.211)).

[0050] In NR, downlink synchronization signals are transmitted from base stations as synchronization signal bursts (hereinafter sometimes referred to as SS bursts) at predetermined intervals for a predetermined duration. SS bursts consist of synchronization signal blocks (hereinafter sometimes referred to as SS blocks) for each beam of the base station. The base station transmits the SS blocks of each beam within the duration of the SS burst, changing the beam. SS blocks consist of P-SS, S-SS, and PBCH.

[0051] In NR, the influence of phase noise is reduced by adding a Phase Tracking Reference Signal (PTRS) as a downlink reference signal for NR. PTRS is also added to the uplink reference signal, just like in the downlink.

[0052] In NR, slot format indication (SFI) has been added to the information contained in the PDCCH in order to flexibly switch between DL and UL within a slot.

[0053] In addition, in NR, the base station pre-configures a portion of the carrier frequency band (hereinafter sometimes referred to as the Bandwidth Part (BWP)) for the UE, and the UE transmits and receives data to and from the base station using this BWP, thereby reducing power consumption in the UE.

[0054] 3GPP is considering the following DC forms: DC by LTE base stations and NR base stations connected to EPC, DC by NR base stations connected to a 5G core system, and DC by LTE base stations and NR base stations connected to a 5G core system (see Non-Patent Documents 12, 16, and 19).

[0055] Additionally, 3GPP is considering supporting services (or applications) using side link (SL) communication in both the EPS and the 5G core system (see Non-Patent Documents 1, 16, 20, 21, 22, and 23). Services using SL communication include, for example, V2X services and proximity services. [Prior art documents] [Non-patent literature]

[0056] [Non-Patent Document 1] 3GPP TS 36.300 V16.2.0 [Non-patent document 2] 3GPP S1-083461 [Non-patent document 3] 3GPP TR 36.814 V9.2.0 [Non-patent document 4] 3GPP TR 36.912 V16.0.0 [Non-patent document 5] "Scenarios, requirements and KPIs for 5G mobile and wireless system", ICT-317669-METIS / D1.1

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Non-licensed literature 9

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Non-licensed Document 21

[0057] Support for various services using SL communication (also called PC5 communication) is being considered in both EPS and the 5G core system (see Non-Patent Documents 1, 16, 20, 21, 22, and 23). In SL communication, communication is performed between terminals. In SL communication, not only direct communication between terminals but also communication between a UE and a network via a relay has been proposed (see Non-Patent Documents 20 and 23). In such communication via a relay, the issue is how to reduce the power consumption of terminals.

[0058] In view of the above-mentioned problems, one of the objects of the present disclosure is to reduce power consumption in a communication system that uses terminal-to-terminal communication. [Means for solving the problem]

[0059] The communication system according to the present disclosure is a communication system comprising a base station, a first communication terminal configured to perform wireless communication with the base station, and a second communication terminal configured to perform terminal-to-terminal communication with the first communication terminal, wherein the first communication terminal is configured to relay communication between the second communication terminal and the base station, and when there is no data to be transmitted or received between the second communication terminal and the base station for a predetermined period of time, the first communication terminal releases its connection with the base station and transitions to an idle state. A communication terminal according to the present disclosure is a communication terminal configured to perform wireless communication with a base station, wherein the communication terminal is configured to perform terminal-to-terminal communication with other communication terminals and to relay communication between the other communication terminals and the base station, and is characterized in that when there is no data to be transmitted or received between the other communication terminals and the base station for a predetermined period of time, the communication terminal releases its connection with the base station and transitions to an idle state. [Effects of the Invention]

[0060] According to the present disclosure, it is possible to reduce power consumption in a communication system that uses terminal-to-terminal communication.

[0061] The objects, features, aspects, and advantages of the present disclosure will become more apparent from the following detailed description and the accompanying drawings. [Brief explanation of the drawings]

[0062] [Figure 1] FIG. 1 is an explanatory diagram showing the configuration of a radio frame used in an LTE communication system. [Figure 2] 1 is a block diagram showing the overall configuration of an LTE communication system 200 being discussed in 3GPP. [Figure 3] FIG. 2 is a block diagram showing the overall configuration of a communication system 210 conforming to the NR standard under discussion in 3GPP. [Figure 4] This is a diagram illustrating the configuration of DC using eNB and gNB connected to EPC. [Figure 5] This is a diagram of the DC configuration using gNB connected to the NG core. [Figure 6] This is a diagram illustrating the configuration of DC using eNB and gNB connected to the NG core. [Figure 7] This is a diagram illustrating the configuration of DC using eNB and gNB connected to the NG core. [Figure 8] FIG. 3 is a block diagram showing the configuration of a mobile terminal 202 shown in FIG. [Figure 9] FIG. 3 is a block diagram showing the configuration of a base station 203 shown in FIG. [Figure 10] FIG. 2 is a block diagram illustrating the configuration of an MME. [Figure 11] A block diagram showing the configuration of 5GC. [Figure 12] 1 is a flowchart showing an outline of operations from cell search to standby operation performed by a communication terminal (UE) in an LTE communication system. [Figure 13] FIG. 1 is a diagram illustrating an example of a cell configuration in an NR system. [Figure 14] FIG. 2 is a sequence diagram showing an example of a method for performing communication between a UE and a NW via a relay UE according to the first embodiment. [Figure 15] FIG. 2 is a sequence diagram showing an example of a method for performing communication between a UE and a NW via a relay UE according to the first embodiment. [Figure 16] FIG. 2 is a sequence diagram showing an example of a method for performing communication between a UE and a NW via a relay UE according to the first embodiment. [Figure 17] FIG. 10 is a sequence diagram showing an example of a method for performing communication between a UE and a NW via a relay UE, according to a first modification of the first embodiment. [Figure 18] FIG. 10 is a sequence diagram showing an example of a method for performing communication between a UE and a NW via a relay UE, according to a first modification of the first embodiment. [Figure 19] FIG. 10 is a sequence diagram showing an example of a method for performing communication between a UE and a NW via a relay UE, according to a first modification of the first embodiment. [Figure 20] FIG. 10 is a sequence diagram showing an example of a method for performing communication between a UE and a NW via a relay UE, according to a second modification of the first embodiment. [Figure 21] FIG. 10 is a sequence diagram showing an example of a method for performing communication between a UE and a NW via a relay UE, according to a second modification of the first embodiment. [Figure 22] FIG. 10 is a sequence diagram showing an example of a method for performing communication between a UE and a NW via a relay UE, according to a second modification of the first embodiment. [Figure 23]FIG. 11 is a sequence diagram showing an example of a method for performing communication between a UE and a NW via a relay UE according to the third embodiment. [Figure 24] FIG. 11 is a sequence diagram showing an example of a method for performing communication between a UE and a NW via a relay UE according to the third embodiment. [Figure 25] FIG. 13 is a sequence diagram showing an example of a method for performing communication between a UE and a NW via a relay UE, according to a first modification of the third embodiment. [Figure 26] FIG. 13 is a sequence diagram showing an example of a method for performing communication between a UE and a NW via a relay UE, according to a first modification of the third embodiment. [Figure 27] This is a sequence diagram showing an example of a method for notifying information regarding communication between a remote UE and a network via a relay UE between a remote UE, a relay UE, and a gNB connected to the relay UE, for variant example 1 of embodiment 3. [Figure 28] FIG. 13 is a conceptual diagram showing a first example of PC5 DRX setting according to the fourth embodiment. [Figure 29] FIG. 13 is a conceptual diagram showing a second example of PC5 DRX setting according to the fourth embodiment. [Figure 30] FIG. 13 is a conceptual diagram showing a third example of PC5 DRX setting according to the fourth embodiment. [Figure 31] FIG. 13 is a conceptual diagram showing a fourth example of PC5 DRX setting according to the fourth embodiment. [Figure 32] FIG. 13 is a sequence diagram showing a first example of a method for aligning DRX in both directions in direct communication between UEs at PC5, according to the fourth embodiment. [Figure 33] FIG. 13 is a sequence diagram showing a first example of a method for aligning DRX in both directions in direct communication between UEs at PC5, according to the fourth embodiment. [Figure 34] FIG. 13 is a sequence diagram showing a second example of a method for aligning DRX in both directions in direct communication between UEs at PC5, according to the fourth embodiment. [Figure 35] FIG. 13 is a sequence diagram showing a second example of a method for aligning DRX in both directions in direct communication between UEs at PC5, according to the fourth embodiment. [Figure 36] FIG. 11 is a sequence diagram showing an example of a method for performing PC5 DRX configuration between a remote UE and a relay UE in communication between the remote UE and a NW via the relay UE, according to the fourth embodiment. [Figure 37] FIG. 11 is a sequence diagram showing an example of a method for performing PC5 DRX configuration between a remote UE and a relay UE in communication between the remote UE and a NW via the relay UE, according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0063] Embodiment 1 Fig. 2 is a block diagram showing the overall configuration of an LTE communication system 200 being discussed in 3GPP. Fig. 2 will now be described. The radio access network is called E-UTRAN (Evolved Universal Terrestrial Radio Access Network) 201. A mobile terminal device (hereinafter referred to as "mobile terminal (User Equipment: UE)") 202, which is a communication terminal device, is capable of wireless communication with a base station device (hereinafter referred to as "base station (E-UTRAN NodeB: eNB)") 203, and transmits and receives signals via wireless communication.

[0064] Here, the term "communication terminal device" includes not only mobile terminal devices such as mobile cell phone terminal devices, but also stationary devices such as sensors. In the following description, the term "communication terminal device" may be simply referred to as a "communication terminal."

[0065] If control protocols for mobile terminals 202, such as RRC (Radio Resource Control), and user planes (hereinafter sometimes referred to as U-Planes), such as PDCP (Packet Data Convergence Protocol), RLC (Radio Link Control), MAC (Medium Access Control), and PHY (Physical layer), terminate at base stations 203, E-UTRAN is composed of one or more base stations 203.

[0066] The control protocol RRC (Radio Resource Control) between the mobile terminal 202 and the base station 203 performs broadcasting, paging, RRC connection management, etc. The states of the base station 203 and the mobile terminal 202 in RRC include RRC_IDLE and RRC_CONNECTED.

[0067] In RRC_IDLE, PLMN (Public Land Mobile Network) selection, system information (SI) broadcast, paging, cell reselection, mobility, etc. are performed. In RRC_CONNECTED, the mobile terminal has an RRC connection and can transmit and receive data with the network. In addition, in RRC_CONNECTED, handover (HO), measurement of neighbor cells, etc. are performed.

[0068] The base station 203 is configured by one or more eNBs 207. A system configured by the core network EPC (Evolved Packet Core) and the radio access network E-UTRAN 201 is called an EPS (Evolved Packet System). The core network EPC and the radio access network E-UTRAN 201 are sometimes collectively referred to as a "network."

[0069] The eNB 207 is connected to a Mobility Management Entity (MME), or a Serving Gateway (S-GW), or an MME / S-GW unit (hereinafter sometimes referred to as an "MME unit") 204 including an MME and an S-GW via an S1 interface, and control information is communicated between the eNB 207 and the MME unit 204. Multiple MME units 204 may be connected to one eNB 207. The eNBs 207 are connected to each other via an X2 interface, and control information is communicated between the eNBs 207.

[0070] The MME unit 204 is an upper device, specifically an upper node, and controls the connection between the eNB 207, which is a base station, and the mobile terminal (UE) 202. The MME unit 204 constitutes the EPC, which is a core network. The base station 203 constitutes the E-UTRAN 201.

[0071] Base station 203 may configure one cell or multiple cells. Each cell has a predetermined range as coverage, which is the range within which communication with mobile terminal 202 is possible, and performs wireless communication with mobile terminal 202 within the coverage. When one base station 203 configures multiple cells, each cell is configured to be able to communicate with mobile terminal 202.

[0072] Figure 3 is a block diagram showing the overall configuration of a 5G communication system 210 being discussed in 3GPP. The following describes Figure 3. The radio access network is referred to as a Next Generation Radio Access Network (NG-RAN) 211. The UE 202 is capable of wireless communication with an NR base station device (hereinafter referred to as an "NR base station (NG-RAN NodeB: gNB)") 213, and transmits and receives signals via wireless communication. The core network is referred to as a 5G Core (5GC).

[0073] If control protocols for UE202, such as RRC (Radio Resource Control), and user planes (hereinafter sometimes referred to as U-Planes), such as SDAP (Service Data Adaptation Protocol), PDCP (Packet Data Convergence Protocol), RLC (Radio Link Control), MAC (Medium Access Control), and PHY (Physical layer), terminate at an NR base station 213, the NG-RAN is composed of one or more NR base stations 213.

[0074] The function of the control protocol RRC (Radio Resource Control) between the UE 202 and the NR base station 213 is the same as that of LTE. The states of the NR base station 213 and the UE 202 in the RRC include RRC_IDLE, RRC_CONNECTED, and RRC_INACTIVE.

[0075] RRC_IDLE and RRC_CONNECTED are the same as those in the LTE system. RRC_INACTIVE maintains the connection between the 5G core and the NR base station 213, and performs system information (SI), paging, cell reselection, mobility, and the like.

[0076] The gNB 217 is connected to an AMF / SMF / UPF unit (hereinafter sometimes referred to as the "5GC unit") 214, which includes an Access and Mobility Management Function (AMF), a Session Management Function (SMF), or a User Plane Function (UPF), or an AMF, SMF, and UPF, via an NG interface. Control information and / or user data are communicated between the gNB 217 and the 5GC unit 214. The NG interface is a collective term for the N2 interface between the gNB 217 and the AMF, the N3 interface between the gNB 217 and the UPF, the N11 interface between the AMF and the SMF, and the N4 interface between the UPF and the SMF. Multiple 5GC units 214 may be connected to one gNB 217. The gNBs 217 are connected to each other via an Xn interface, and control information and / or user data are communicated between the gNBs 217.

[0077] The NR base station 213 may configure one or more cells, similar to the base station 203. When one NR base station 213 configures multiple cells, each cell is configured to be able to communicate with the UE 202.

[0078] The gNB 217 may be divided into a central unit (hereinafter, sometimes referred to as a CU) 218 ​​and distributed units (hereinafter, sometimes referred to as DUs) 219. One CU 218 is configured in the gNB 217. One or more DUs 219 are configured in the gNB 217. The CU 218 is connected to the DU 219 via an F1 interface, and control information and / or user data is communicated between the CU 218 and the DU 219.

[0079] In a 5G communication system, a Unified Data Management (UDM) function and a Policy Control Function (PCF) described in Non-Patent Document 21 (3GPP TS23.501) may be included. The UDM and / or PCF may be included in the 5GC unit in FIG. 3.

[0080] A 5G communication system may include a Non-3GPP Interworking Function (N3IWF) described in Non-Patent Document 21 (3GPP TS23.501). The N3IWF may terminate an Access Network (AN) between the UE and the N3IWF in non-3GPP access between the UE and the N3IWF.

[0081] Fig. 4 is a diagram showing a DC configuration by eNBs and gNBs connected to EPC. In Fig. 4, solid lines indicate U-Plane connections, and dashed lines indicate C-Plane connections. In Fig. 4, eNB223-1 serves as the master base station, and gNB224-2 serves as the secondary base station (this DC configuration may be referred to as EN-DC). Fig. 4 shows an example in which U-Plane connection between MME unit 204 and gNB224-2 is made via eNB223-1, but it may also be made directly between MME unit 204 and gNB224-2.

[0082] Figure 5 is a diagram showing the configuration of DC by a gNB connected to an NG core. In Figure 5, solid lines indicate U-Plane connections, and dashed lines indicate C-Plane connections. In Figure 5, gNB 224-1 is the master base station, and gNB 224-2 is the secondary base station (this DC configuration may be referred to as NR-DC). Figure 5 shows an example in which U-Plane connection between 5GC unit 214 and gNB 224-2 is made via gNB 224-1, but it may also be made directly between 5GC unit 214 and gNB 224-2.

[0083] Figure 6 is a diagram showing a DC configuration by eNB and gNB connected to the NG core. In Figure 6, solid lines indicate U-Plane connections, and dashed lines indicate C-Plane connections. In Figure 6, eNB226-1 is the master base station, and gNB224-2 is the secondary base station (this DC configuration may be referred to as NG-EN-DC). Figure 6 shows an example in which U-Plane connection between 5GC unit 214 and gNB224-2 is made via eNB226-1, but it may also be made directly between 5GC unit 214 and gNB224-2.

[0084] Figure 7 is a diagram showing another configuration of DC by eNB and gNB connected to the NG core. In Figure 7, solid lines indicate U-Plane connections, and dashed lines indicate C-Plane connections. In Figure 7, gNB224-1 is the master base station, and eNB226-2 is the secondary base station (this DC configuration may be referred to as NE-DC). Figure 7 shows an example in which U-Plane connection between 5GC unit 214 and eNB226-2 is made via gNB224-1, but it may also be made directly between 5GC unit 214 and eNB226-2.

[0085] FIG. 8 is a block diagram showing the configuration of mobile terminal 202 shown in FIG. 2. The transmission process of mobile terminal 202 shown in FIG. 8 will be described. First, control data from protocol processing unit 301 and user data from application unit 302 are stored in transmission data buffer unit 303. The data stored in transmission data buffer unit 303 is passed to encoder unit 304, where it is subjected to encoding processes such as error correction. Some data may be output directly from transmission data buffer unit 303 to modulation unit 305 without being encoded. The data encoded by encoder unit 304 is modulated by modulation unit 305. Precoding in MIMO may be performed by modulation unit 305. The modulated data is converted into a baseband signal, and then output to frequency conversion unit 306, where it is converted into a radio transmission frequency. Thereafter, a transmission signal is transmitted to base station 203 from antennas 307-1 to 307-4. Although FIG. 8 illustrates an example in which the number of antennas is four, the number of antennas is not limited to four.

[0086] Furthermore, the reception process of mobile terminal 202 is performed as follows. Radio signals from base station 203 are received by antennas 307-1 to 307-4. The received signals are converted from a radio reception frequency to a baseband signal by frequency conversion unit 306, and demodulated by demodulation unit 308. Demodulation unit 308 may also perform weight calculation and multiplication processing. The demodulated data is passed to decoder unit 309, where decoding processing such as error correction is performed. Of the decoded data, control data is passed to protocol processing unit 301, and user data is passed to application unit 302. A series of processes of mobile terminal 202 is controlled by control unit 310. Therefore, although control unit 310 is omitted in FIG. 8, it is connected to each unit 301 to 309. In FIG. 8, the number of antennas used by mobile terminal 202 for transmission and the number of antennas used for reception may be the same or different.

[0087] 2. The transmission process of the base station 203 shown in FIG. 9 will be described. The EPC communication unit 401 transmits and receives data between the base station 203 and the EPC (such as the MME unit 204). The 5GC communication unit 412 transmits and receives data between the base station 203 and the 5GC (such as the 5GC unit 214). The other base station communication unit 402 transmits and receives data with other base stations. The EPC communication unit 401, the 5GC communication unit 412, and the other base station communication unit 402 each exchange information with the protocol processing unit 403. The control data from the protocol processing unit 403, and the user data and control data from the EPC communication unit 401, the 5GC communication unit 412, and the other base station communication unit 402 are stored in the transmission data buffer unit 404.

[0088] The data stored in transmission data buffer unit 404 is passed to encoder unit 405, where it undergoes encoding processing such as error correction. Some data may be output directly from transmission data buffer unit 404 to modulation unit 406 without undergoing encoding processing. The encoded data is modulated by modulation unit 406. MIMO precoding may be performed by modulation unit 406. The modulated data is converted into a baseband signal, and then output to frequency conversion unit 407, where it is converted into a radio transmission frequency. Thereafter, a transmission signal is transmitted to one or more mobile terminals 202 from antennas 408-1 to 408-4. Although FIG. 9 illustrates an example in which the number of antennas is four, the number of antennas is not limited to four.

[0089] The reception process of the base station 203 is performed as follows: A radio signal from one or more mobile terminals 202 is received by an antenna 408. The received signal is converted from a radio reception frequency to a baseband signal by a frequency conversion unit 407, and demodulated by a demodulation unit 409. The demodulated data is passed to a decoder unit 410, where decoding processes such as error correction are performed. Of the decoded data, control data is passed to the protocol processing unit 403, the 5GC communication unit 412, the EPC communication unit 401, or the other base station communication unit 402, and user data is passed to the 5GC communication unit 412, the EPC communication unit 401, and the other base station communication unit 402. A series of processes of the base station 203 is controlled by a control unit 411. Therefore, although the control unit 411 is omitted in FIG. 9, it is connected to each unit 401 to 410. In FIG. 9, the number of antennas used for transmission by the base station 203 and the number of antennas used for reception may be the same or different.

[0090] 9 is a block diagram showing the configuration of base station 203, but a similar configuration may also be used for base station 213. In addition, in FIGS. 8 and 9, the number of antennas in mobile terminal 202 and the number of antennas in base station 203 may be the same or different.

[0091] 10 is a block diagram showing the configuration of an MME. FIG. 10 shows the configuration of an MME 204a included in the MME unit 204 shown in FIG. 2 described above. A PDN GW communication unit 501 transmits and receives data between the MME 204a and a PDN GW. A base station communication unit 502 transmits and receives data via the S1 interface between the MME 204a and a base station 203. If the data received from the PDN GW is user data, the user data is passed from the PDN GW communication unit 501 to the base station communication unit 502 via a user plane communication unit 503, and transmitted to one or more base stations 203. If the data received from the base station 203 is user data, the user data is passed from the base station communication unit 502 to the PDN GW communication unit 501 via the user plane communication unit 503, and transmitted to the PDN GW.

[0092] If the data received from the PDN GW is control data, the control data is passed from the PDN GW communication unit 501 to the control plane control unit 505. If the data received from the base station 203 is control data, the control data is passed from the base station communication unit 502 to the control plane control unit 505.

[0093] The control plane control unit 505 includes a NAS security unit 505-1, an SAE bearer control unit 505-2, an idle state mobility management unit 505-3, etc., and performs overall processing for the control plane (hereinafter sometimes referred to as the C-Plane). The NAS security unit 505-1 performs security for NAS (Non-Access Stratum) messages, etc. The SAE bearer control unit 505-2 performs management of SAE (System Architecture Evolution) bearers, etc. The idle state mobility management unit 505-3 performs mobility management in the idle state (also referred to as the LTE-IDLE state or simply idle), generation and control of paging signals in the idle state, addition, deletion, update, and search of tracking areas for one or more mobile terminals 202 under its control, tracking area list management, etc.

[0094] The MME 204a distributes paging signals to one or more base stations 203. The MME 204a also performs mobility control in an idle state. The MME 204a manages a tracking area list when the mobile terminal is in an idle state and an active state. The MME 204a initiates a paging protocol by transmitting a paging message to a cell belonging to a tracking area in which the UE is registered. The idle state mobility management unit 505-3 may manage the CSG, CSG ID, and whitelist of the eNB 207 connected to the MME 204a.

[0095] FIG. 11 is a block diagram showing the configuration of 5GC. FIG. 11 shows the configuration of the 5GC unit 214 shown in FIG. 3 described above. FIG. 11 shows a case where the 5GC unit 214 shown in FIG. 5 includes an AMF configuration, an SMF configuration, and a UPF configuration. The Data Network communication unit 521 transmits and receives data between the 5GC unit 214 and the Data Network. The base station communication unit 522 transmits and receives data via the S1 interface between the 5GC unit 214 and the base station 203, and / or the NG interface between the 5GC unit 214 and the base station 213. If the data received from the Data Network is user data, the user data is passed from the Data Network communication unit 521 to the base station communication unit 522 via the user plane communication unit 523, and transmitted to one or more base stations 203 and / or base stations 213. If the data received from base station 203 and / or base station 213 is user data, the user data is passed from base station communication unit 522 to data network communication unit 521 via user plane communication unit 523 and transmitted to the data network.

[0096] If the data received from the Data Network is control data, the control data is passed from the Data Network communication unit 521 to the session management unit 527 via the user plane communication unit 523. The session management unit 527 passes the control data to the control plane control unit 525. If the data received from the base station 203 and / or base station 213 is control data, the control data is passed from the base station communication unit 522 to the control plane control unit 525. The control plane control unit 525 passes the control data to the session management unit 527.

[0097] The control plane control unit 525 includes a NAS security unit 525-1, a PDU session control unit 525-2, an idle state mobility management unit 525-3, etc., and performs overall processing for the control plane (hereinafter sometimes referred to as the C-Plane). The NAS security unit 525-1 performs security for NAS (Non-Access Stratum) messages, etc. The PDU session control unit 525-2 performs management of PDU sessions between the mobile terminal 202 and the 5GC unit 214, etc. The idle state mobility management unit 525-3 performs mobility management in the idle state (also referred to as the RRC_IDLE state or simply idle), generation and control of paging signals in the idle state, addition, deletion, update, and search of tracking areas for one or more mobile terminals 202 under its control, tracking area list management, etc.

[0098] The 5GC unit 214 distributes paging signals to one or more base stations 203 and / or base station 213. The 5GC unit 214 also performs mobility control in an idle state. The 5GC unit 214 manages a tracking area list when the mobile terminal is in an idle state, an inactive state, or an active state. The 5GC unit 214 initiates a paging protocol by transmitting a paging message to a cell belonging to a tracking area in which the UE is registered.

[0099] Next, an example of a cell search method in a communication system is shown. Fig. 12 is a flowchart showing an outline of the process from cell search to standby operation performed by a communication terminal (UE) in an LTE communication system. When the communication terminal starts a cell search, in step ST601, it synchronizes slot timing and frame timing using a primary synchronization signal (P-SS) and a secondary synchronization signal (S-SS) transmitted from a surrounding base station.

[0100] P-SS and S-SS are collectively called the Synchronization Signal (SS). The Synchronization Signal (SS) is assigned a synchronization code that corresponds one-to-one to the PCI assigned to each cell. 504 different PCIs are being considered. These 504 different PCIs are used to achieve synchronization and to detect (identify) the PCI of the synchronized cell.

[0101] Next, in step ST602, for the synchronized cell, a cell-specific reference signal (CRS), which is a reference signal (RS) transmitted from the base station for each cell, is detected and the RS received power (Reference Signal Received Power: RSRP) is measured. The RS uses a code that has a one-to-one correspondence with the PCI. By correlating with this code, it is possible to separate the cell from other cells. By deriving the code for the RS of the cell from the PCI identified in step ST601, it is possible to detect the RS and measure the RS received power.

[0102] Next, in step ST603, the cell with the best RS reception quality, for example, the cell with the highest RS reception power, that is, the best cell, is selected from one or more cells detected up to step ST602.

[0103] Next, in step ST604, the PBCH of the best cell is received to obtain the BCCH, which is broadcast information. A MIB (Master Information Block), which includes cell configuration information, is mapped to the BCCH on the PBCH. Therefore, the MIB can be obtained by receiving the PBCH and obtaining the BCCH. Examples of MIB information include the DL (downlink) system bandwidth (also called transmission bandwidth configuration: dl-bandwidth), the number of transmitting antennas, and the SFN (System Frame Number).

[0104] Next, in step ST605, the DL-SCH of the cell is received based on the cell configuration information in the MIB, and SIB (System Information Block) 1 is obtained from the broadcast information BCCH. SIB 1 includes information on access to the cell, information on cell selection, and scheduling information for other SIBs (SIBk; k is an integer greater than or equal to 2). SIB 1 also includes a tracking area code (TAC).

[0105] Next, in step ST606, the communication terminal compares the TAC of the SIB1 received in step ST605 with the TAC portion of the tracking area identity (TAI) in the tracking area list that the communication terminal already holds. The tracking area list is also called a TAI list. The TAI is identification information for identifying a tracking area, and is composed of an MCC (Mobile Country Code), an MNC (Mobile Network Code), and a TAC (Tracking Area Code). The MCC is a country code. The MNC is a network code. The TAC is a tracking area code number.

[0106] If the comparison in step ST606 shows that the TAC received in step ST605 is the same as the TAC included in the tracking area list, the communication terminal enters standby mode in the cell. If the comparison shows that the TAC received in step ST605 is not included in the tracking area list, the communication terminal requests a core network (EPC) including an MME, etc., to change the tracking area in order to perform a Tracking Area Update (TAU) through the cell.

[0107] In the example shown in Fig. 12, an example of operations from cell search to standby in the LTE system is shown, but in the NR system, in addition to the best cell, the best beam may be selected in step ST603. Also, in the NR system, beam information, for example, a beam identifier, may be acquired in step ST604. Also, in the NR system, scheduling information of remaining minimum SI (RMSI) may be acquired in step ST604. In the NR system, RMSI may be received in step ST605.

[0108] An apparatus constituting a core network (hereinafter sometimes referred to as a "core network side apparatus") updates the tracking area list based on the identification number (e.g., UE-ID) of the communication terminal sent from the communication terminal together with a TAU request signal. The core network side apparatus transmits the updated tracking area list to the communication terminal. The communication terminal rewrites (updates) the TAC list held by the communication terminal based on the received tracking area list. Thereafter, the communication terminal enters standby operation in the cell.

[0109] The widespread use of smartphones and tablet devices has led to an explosive increase in cellular wireless communication traffic, raising concerns about a shortage of wireless resources worldwide. In response to this, efforts are being made to develop small cells and promote spatial separation in order to improve frequency utilization efficiency.

[0110] In a conventional cell configuration, a cell configured by an eNB has a relatively wide coverage area. Conventionally, a cell is configured so that a certain area is covered by the relatively wide coverage areas of multiple cells configured by multiple eNBs.

[0111] In the case of small cell configuration, a cell configured by an eNB has a narrower coverage area than a cell configured by a conventional eNB. Therefore, as in the past, a larger number of small cell configuration eNBs are required to cover a certain area compared to conventional eNBs.

[0112] In the following description, a cell with a relatively large coverage, such as a cell configured by a conventional eNB, is referred to as a "macro cell," and an eNB that configures the macro cell is referred to as a "macro eNB." Also, a cell with a relatively small coverage, such as a cell configured as a small cell, is referred to as a "small cell," and an eNB that configures the small cell is referred to as a "small eNB."

[0113] The macro eNB may be, for example, a "Wide Area Base Station" as described in Non-Patent Document 7.

[0114] The small eNB may be, for example, a low-power node, a local area node, a hotspot, etc. Also, the small eNB may be a pico eNB constituting a pico cell, a femto eNB constituting a femto cell, a HeNB, a remote radio head (RRH), a remote radio unit (RRU), a remote radio equipment (RRE), or a relay node (RN). Also, the small eNB may be a "local area base station" or a "home base station" as described in Non-Patent Document 7.

[0115] FIG. 13 shows an example of a cell configuration in NR. In an NR cell, narrow beams are formed and transmitted while changing direction. In the example shown in FIG. 13, at a certain time, base station 750 transmits and receives signals to and from a mobile terminal using beam 751-1. At another time, base station 750 transmits and receives signals to and from a mobile terminal using beam 751-2. In a similar manner, base station 750 transmits and receives signals to and from a mobile terminal using one or more of beams 751-3 to 751-8. In this way, base station 750 configures a wide-area cell.

[0116] 13 shows an example in which the number of beams used by the base station 750 is 8, but the number of beams may be different from 8. Also, in the example shown in FIG. 13, the number of beams used simultaneously by the base station 750 is 1, but it may be multiple.

[0117] 3GPP supports Side Link (SL) for D2D (Device to Device) communication and V2V (Vehicle to Vehicle) communication (see Non-Patent Document 1 and Non-Patent Document 16). SL is defined by the PC5 interface.

[0118] The physical channels used for SL (see Non-Patent Document 1) will be described below. A physical sidelink broadcast channel (PSBCH) carries information related to the system and synchronization, and is transmitted from a UE.

[0119] The physical sidelink discovery channel (PSDCH) carries sidelink discovery messages from the UE.

[0120] The physical sidelink control channel (PSCCH) carries control information from the UE for sidelink and V2X sidelink communications.

[0121] The physical sidelink shared channel (PSSCH) carries data from the UE for sidelink and V2X sidelink communications.

[0122] The physical sidelink feedback channel (PSFCH) carries HARQ feedback on the sidelink from UEs that receive a PSSCH transmission to the UE that transmitted the PSSCH.

[0123] The transport channel used for SL (see Non-Patent Document 1) will be described below. The sidelink broadcast channel (SL-BCH) has a predetermined transport format and is mapped to the PSBCH, which is a physical channel.

[0124] The Sidelink Discovery Channel (SL-DCH) has periodic broadcast transmissions of a fixed size and a predetermined format. The SL-DCH supports both UE autonomous resource selection and eNB-scheduled resource allocation. UE autonomous resource selection involves a collision risk, whereas when the UE is allocated dedicated resources by the eNB, there is no collision. The SL-DCH supports HARQ combining but not HARQ feedback. The SL-DCH is mapped to the PSDCH, a physical channel.

[0125] The Sidelink Shared Channel (SL-SCH) supports broadcast transmission. It supports both UE autonomous resource selection and eNB-scheduled resource allocation. While UE autonomous resource selection involves a collision risk, there is no collision when the UE is allocated dedicated resources by the eNB. The SL-SCH also supports HARQ combining but not HARQ feedback. The SL-SCH also supports dynamic link adaptation by varying transmit power, modulation, and coding. The SL-SCH is mapped to the PSSCH, a physical channel.

[0126] The logical channels used for SL (see Non-Patent Document 1) will be described. The Sidelink Broadcast Control Channel (SBCCH) is a sidelink channel for broadcasting sidelink system information from one UE to other UEs. The SBCCH is mapped to the SL-BCH, which is a transport channel.

[0127] The Sidelink Traffic Channel (STCH) is a point-to-multipoint traffic channel for transmitting user information from one UE to other UEs. The STCH is used only by UEs with sidelink communication capability and UEs with V2X sidelink communication capability. Point-to-point communication between two sidelink-capable UEs is also realized by the STCH. The STCH is mapped to the SL-SCH, a transport channel.

[0128] The Sidelink Control Channel (SCCH) is a control channel for transmitting control information from one UE to another UE. The SCCH is mapped to the SL-SCH, which is a transport channel.

[0129] 3GPP is considering supporting V2X communication in NR as well. The study of V2X communication in NR is being carried out based on the LTE system and LTE-A system, but the following changes and additions have been made from the LTE system and LTE-A system.

[0130] In LTE, SL communication was limited to broadcast. In NR, support for unicast and groupcast as SL communication in addition to broadcast is being considered (see Non-Patent Document 22 (TS23.287)).

[0131] For unicast and groupcast communications, support for HARQ feedback (Ack / Nack), CSI reporting, etc. is being considered.

[0132] In order to support unicast and groupcast in addition to broadcast in SL communication, support for PC5-S signaling is being considered (see Non-Patent Document 22 (TS23.287)). For example, PC5-S signaling is implemented to establish a link for implementing SL, i.e., PC5 communication. This link is implemented in the V2X layer and is also called a Layer 2 link.

[0133] Furthermore, support for RRC signaling in SL communication is being considered (see Non-Patent Document 22 (TS23.287)). RRC signaling in SL communication is also referred to as PC5 RRC signaling. For example, it has been proposed to notify UE capabilities between UEs performing PC5 communication, and to notify AS layer settings for V2X communication using PC5 communication.

[0134] In SL communication, communication between a UE and a network via a relay has been proposed (see Non-Patent Documents 20 and 23). A relay between a UE and a network may be referred to as a UE-to-network relay or a UE-to-network relay. In this disclosure, a UE that performs relaying between a UE and a network may be referred to as a relay UE.

[0135] For example, there may be a need to communicate not only between UEs within the coverage of a RAN node (e.g., gNB) but also between UEs that are farther away and the RAN node. In such cases, a method using a UE-to-NW relay may be considered. For example, communication between a gNB and a UE (sometimes referred to as a remote UE) may be performed via a relay UE. Communication between the gNB and the relay UE is performed via Uu, and communication between the relay UE and the remote UE is performed via PC5.

[0136] Conventionally, in a 5G system, a PDU session is established between a UE and a NW in communication between the UE and the NW. However, in a UE-to-NW relay, communication between the UE and the NW is performed via a relay UE, so conventional methods cannot be applied. This paper discloses a PDU session when communication between a UE and a NW is performed via a relay UE.

[0137] A PDU session is established between the relay UE and the NW. A PDU session is established between the relay UE and a CN-side node. The CN-side node may be a UPF. A PDU session may be established between the relay UE and a data network (DN). A PC5-S link is established between the relay UE and the remote UE. Communication is performed between the UE and the NW via the relay UE using the PDU session and the PC5-S link.

[0138] A PDU session for relaying is established between the relay UE and the CN node. A PC5-S link is established between the relay UE and the remote UE. The relay UE notifies the AMF or SMF of information about the relay UE. This may be performed during the PDU session establishment process. The remote UE notifies the relay UE of information about the remote UE. The remote UE may also notify the AMF or SMF of information about the remote UE. Specific examples of the information about the relay UE and remote UE include a UE identifier and IP information. The IP information may be an IP address. Another specific example of the information about the remote UE may be information about the PC5-S link between the remote UE and the relay UE. The information about the PC5-S link may be, for example, a PC5-S link identifier, a source UE identifier, a destination UE identifier, PC5 QoS flow information, a PC5 QoS flow identifier, SLRB setting information, an SLRB identifier, or a combination of these.

[0139] The IP address of the remote UE may be IPv4, which can avoid the complexity of the device design. The IP address of the remote UE may be IPv6, which can accommodate a large number of UEs in the communication network.

[0140] The relay UE may store information about the remote UE. Also, the AMF / SMF may store information about the remote UE. The information about the remote UE may be associated with the relay UE. The information about the remote UE may be stored in association with the relay UE. The information about the remote UE may be associated with a PDU session established between the relay UE and the NW. The information about the remote UE may be stored in association with a PDU session established between the relay UE and the NW. For example, the information about the remote UE may be stored in the context of the relay UE. By associating the information about the remote UE with the relay UE or associating the information about the remote UE with a PDU session established between the relay UE and the NW, for example, the AMF / SMF can recognize that the PDU session is not simply a PDU session between the relay UE and the CN, but is a PDU session for relaying to the remote UE.

[0141] The AMF / SMF notifies the UPF of information about the remote UE. The UPF can also recognize the information about the remote UE. The information about the remote UE may be notified in association with the relay UE. The information about the remote UE may be notified in association with the PDU session established between the relay UE and the NW. By associating the information about the remote UE with the relay UE or the PDU session established between the relay UE and the NW, for example, the UPF can recognize that the PDU session is not simply a PDU session between the relay UE and the CN, but is a PDU session for relaying to the remote UE.

[0142] In this way, the PDU session between the relay UE and the NW is associated with the PC5-S link between the relay UE and the remote UE.

[0143] The relay UE, as a router for the remote UE, forwards the PC5-S link between the remote UE and the relay UE and the PDU session between the relay UE and the NW, and may use information about the remote UE for the forwarding.

[0144] In this way, data communication between the remote UE and the UPF becomes possible via the relay UE.

[0145] As described above, communication between a remote UE and a network via a relay UE is performed with a PDU session established between the relay UE and the network. The relay UE must maintain a connection with the network. Furthermore, communication between a remote UE and a network via a relay UE is performed with a PC5-S link established between the remote UE and the relay UE. The remote UE must maintain a connection with the relay UE. Therefore, communication between a remote UE and a network via a relay UE increases the power consumption of the relay UE and the remote UE.

[0146] Terminals performing SL communication are expected to be installed not only in vehicles but also carried by pedestrians. Such terminals have a limited battery capacity. Furthermore, even if terminals are equipped with abundant batteries, low power consumption is required for building an ecological society. Therefore, reducing the power consumption of terminals performing SL communication, such as relay UEs and remote UEs in communications between remote UEs and networks via relay UEs, is an issue.

[0147] A method for solving such problems is disclosed.

[0148] A relay UE capable of UE-to-NW relay is permitted to transition to RRC_Idle. A relay UE capable of UE-to-NW relay may be permitted to transition to CM_Idle. In other words, the RRC connection between the relay UE and the gNB may be released. The PDU session between the relay UE and the NW may be released. The above transitions and releases may be performed even if a PC5-S link is established between the remote UE and the relay UE.

[0149] An RRC release process is performed between the gNB and the relay UE. The gNB may initiate an RRC release for the relay UE. The relay UE may request an RRC release from the gNB. Upon receiving the RRC release request, the gNB performs an RRC release process with the relay UE. Furthermore, when the AMF performs a PDU session release process for the gNB, the gNB may perform an RRC release process with the relay UE. In this way, it is possible to transition the relay UE to the RRC_Idle state. It is possible to reduce the power consumption of the relay UE.

[0150] The relay UE and NW nodes may perform the PDU session release process. The NW nodes include gNB, AMF, SMF, and UPF. The NW nodes may include a DN (Data Network). The AMF may initiate the PDU session release process between the relay UE and NW. The SMF may request the AMF to release the PDU session. The UPF may request the AMF to release the PDU session via the SMF. The relay UE may request the AMF to release the PDU session. The AMF that receives the PDU session release request performs the PDU session release process between the relay UE and NW. This makes it possible to release resources used for the PDU session in the relay UE. This reduces the power consumption of the relay UE and improves the utilization efficiency of radio resources.

[0151] The AMF performs a process to release (release) the CM connection between the relay UE and the NW. The AMF may initiate the release of the CM connection. The relay UE may request the AMF to release the CM connection. The gNB may request the AMF to release the CM connection with the relay UE. Upon receiving the CM connection release request, the AMF performs a process to release the CM connection with the relay UE. The AMF may also perform a CM connection release process when it receives a PDU session release request. In this way, it is possible to transition the relay UE to the CM_Idle state. It is possible to reduce the power consumption of the relay UE.

[0152] The processes of releasing the RRC connection, the PDU session, and the CM connection may be performed separately. By performing some or all of these release processes, it is possible to reduce the power consumption of the relay UE.

[0153] The above-mentioned release process may be performed while the PC5-S link between the relay UE and the remote UE is connected, or may be performed without releasing the PC5-S link between the relay UE and the remote UE.

[0154] For example, when communication between the remote UE and the NW is temporarily lost, the above-described release process may be performed. Furthermore, when communication between the remote UE and the NW is periodically performed, the above-described release process may be performed during the period when the communication is not performed. For example, when service data communication between the remote UE and the NW is lost, only the PDU session release process may be performed. For example, when service data communication between the remote UE and the NW is lost, the PDU session release process, RRC connection release process, and CM connection release process may also be performed. For example, when data communication including service data communication and signaling between the remote UE and the NW is lost, the PDU session release process, RRC connection release process, and CM connection release process may also be performed. By performing the above-described release process, releasing the connection between the relay UE and the NW, and transitioning the relay UE to the RRC_Idle or CM_Idle state, it is possible to reduce the power consumption of the relay UE.

[0155] The method for determining whether to perform or request the release process in the relay UE or NW node is disclosed. When there is no data of the PDU session for a predetermined period of time, the method determines whether to perform or request the release process.

[0156] The predetermined period may be statically determined by a standard or the like. Alternatively, the predetermined period may be configurable by a network node. The predetermined period may be configurable semi-statically. For example, the AMF or PCF may set the predetermined period. For example, the AMF may set the predetermined period using QoS when establishing a PDU session. The node that sets the predetermined period notifies each node of the set predetermined period.

[0157] The relay UE or NW node may measure timing information related to data communication in the PDU session. For example, the relay UE or NW node may measure the timing at which data communication occurs in the PDU session. For example, the relay UE or NW node may measure the period since data was communicated in the PDU session. The relay UE or NW node may derive a traffic pattern from the measured timing information related to data communication. The derivation may be performed, for example, using statistical processing.

[0158] The measurement results may be stored in the node that performed the measurement. Alternatively, the measurement results may be notified to another NW node or a server. The other NW node or the server may derive a traffic pattern from the measurement results. The node that derives the traffic pattern may notify the relay UE or the NW node of the derived traffic pattern.

[0159] In this way, the relay UE and the NW node can obtain time information related to data communication in the PDU session. The relay UE and the NW node can use the time information to determine whether there is data for a predetermined period of time.

[0160] The predetermined period may be set in a timer. For example, when data is communicated in a PDU session, the timer is started. When new data is communicated, the timer is initialized. When the timer expires without data communication, the above-mentioned release process is performed or a request for the above-mentioned release process is performed.

[0161] Another method for determining whether or not to perform the release process is disclosed. When there is no data from the PC5-S link for a predetermined period of time, it is determined whether or not to perform the release process.

[0162] The predetermined period may be statically determined by a standard or the like. Alternatively, the predetermined period may be configurable by a network node. The predetermined period may be configurable semi-statically. For example, the AMF or PCF may set the predetermined period. For example, the AMF may set the predetermined period using the QoS of the service communicated between the remote UE and the network. The node that sets the predetermined period notifies the relay UE or the remote UE of the set predetermined period.

[0163] The relay UE or the remote UE may measure timing information related to data communication on the PC5-S link. For example, the relay UE or the remote UE may measure the timing of data communication on the PC5-S link. For example, the relay UE or the remote UE may measure the period of time since data was communicated on the PC5-S link. The relay UE or the remote UE may derive a traffic pattern from the measured timing information related to data communication. The derivation may be performed using, for example, statistical processing.

[0164] The measurement results may be stored in the relay UE or the remote UE that performed the measurement. Alternatively, the measurement results may be notified from the remote UE to another NW node or a server via the relay UE. Alternatively, the measurement results may be notified from the relay UE to another NW node or a server. The other NW node or a server may derive a traffic pattern from the measurement results. The node that derives the traffic pattern may notify the remote UE or the relay UE of the derived traffic pattern.

[0165] In this way, the remote UE and the relay UE can obtain time information related to data communication in the PC5-S link, and the remote UE and the relay UE can use the time information to determine whether there is data for a predetermined period of time.

[0166] The predetermined period may be set in a timer. For example, when data is communicated on the PC5-S link, the timer is started. When new data is communicated, the timer is initialized. When the timer expires without data communication, the above-mentioned release process is performed or a request for the above-mentioned release process is performed.

[0167] The predetermined period set for the PDU session and the predetermined period set for the PC5-S link may be different. This allows for flexible setting according to the respective communication timings. Alternatively, the predetermined periods may be set to the same value. The same setting can be used for both the PC5-S link and the PDU session according to the service used for communication between the remote UE and the NW. This also facilitates the release process described above. By setting the predetermined period to the same value, for example, a relay UE that has established a PDU session with the PC5-S link can manage the predetermined period with a single timer. This avoids the complexity of the decision to transition to the release process described above.

[0168] In this way, if there is no data communication for a predetermined period of time, the relay UE can be transitioned to the RRC_Idle or CM_Idle state, thereby reducing the power consumption of the relay UE.

[0169] A request for RRC release between the relay UE and the gNB may be made by the remote UE, or the remote UE may request the RRC release from the relay UE or the gNB.

[0170] The remote UE may request the release of the PDU session between the relay UE and the NW. The remote UE may request the relay UE, the gNB, the AMF, the SMF, the UPF, or the DN to release the PDU session.

[0171] The remote UE may request the release of the CM connection between the relay UE and the NW. The remote UE may request the relay UE, the gNB, or the AMF to release the CM connection.

[0172] Since the remote UE recognizes the service that communicates with the NW, it is easy for the remote UE to determine when communication between the remote UE and the NW is temporarily suspended. By requesting the release process between the relay UE and the NW, the remote UE can transition to the RRC_Idle or CM_Idle state of the relay UE, which is appropriate for the communication service between the remote UE and the NW.

[0173] To determine whether to perform or request the release process in the remote UE, the method of determining whether to perform or request the release process when there is no data on the PC5-S link for a predetermined period of time can be appropriately applied. The presence or absence of data communication in the PDU session is determined based on the presence or absence of data communication on the PC5-S link. This determination is valid because both the PC5-S link between the remote UE and the relay UE and the PDU session between the relay UE and the NW are used for communication between the remote UE and the NW.

[0174] In this way, if there is no data communication on the PC5-S link for a predetermined period of time, the remote UE can transition the relay UE to the RRC_Idle or CM_Idle state, thereby reducing the power consumption of the relay UE.

[0175] This paper discloses a method for releasing the connection between a relay UE and a network when there is no data communication between the relay UE and the network via the relay UE. It also discloses a process for transitioning the relay UE to the RRC_Idle or CM_Idle state. When data is generated for the relay UE while the relay UE is in the RRC_Idle or CM_Idle state, it is possible to notify the relay UE that the data has been generated. However, when data is generated from an AS (Application Server) or DN to the remote UE while the relay UE is in the RRC_Idle or CM_Idle state, it is not possible to notify the remote UE that the data has been generated. This makes it impossible to send data to the remote UE via the relay UE.

[0176] A method for solving such problems is disclosed.

[0177] In the above-described communication method between a remote UE and a NW, it has been shown that the AMF may store information about the remote UE in association with the relay UE. Information associating the relay UE with the remote UE may be provided. In the present disclosure, information associating the relay UE with the remote UE may be simply referred to as association information. The remote UE associated with the relay UE may be a remote UE that performs communication between the NW and a remote UE with which the relay UE has established a PDU session. The remote UE associated with the relay UE may be a remote UE that has established a PC5-S link with the relay UE.

[0178] Multiple remote UEs may be associated with one relay UE. This is effective when a remote UE communicates with a network via one relay UE. Multiple relay UEs may be associated with one remote UE. This is effective when a remote UE communicates with a network via multiple relay UEs.

[0179] The AMF may perform mobility management of the remote UE. The AMF can perform mobility management of the remote UE by having related information of the remote UE. The AMF may associate with the relay UE and perform mobility management of the remote UE together with mobility management of the relay UE.

[0180] The association information may be a list. The association information may include information about each UE. Examples of the information about each UE include an identifier, IP information, a service type, and slice information. The association information may also include information about a remote UE. The association information may be a list indicating associated remote UEs, with the relay UE as an index. The AMF can create a list including the remote UE as an information element of the relay UE that has obtained the remote UE-related information, making it easy to create the list, for example.

[0181] The association information may be a list indicating the associated relay UEs, with the remote UE as an index. The AMF can create a list including the relay UE as an information element of the remote UE, so that, for example, when the AMF receives a notification of data generation for the remote UE, it can easily search for the relay UE associated with the remote UE.

[0182] In the communication between the remote UE and the NW via the relay UE, the process of transitioning the relay UE to the RRC_Idle or CM_Idle state has been disclosed. The AMF maintains association information even when the relay UE enters the RRC_Idle or CM_Idle state.

[0183] Information about the remote UE may be updated as appropriate. When information about the remote UE is updated, the remote UE may notify the relay UE, AMF, or SMF of the updated information. The relay UE may notify the AMF or SMF of the updated information about the remote UE. When information about a relay UE that the remote UE connects to is updated, the remote UE may notify the AMF or SMF of the updated information. For example, when a relay UE newly connects to the remote UE, the relay UE may notify the AMF or SMF of the information about the remote UE. For example, when the relay UE receives updated information about the remote UE from the remote UE, the relay UE may notify the AMF or SMF of the updated information about the remote UE.

[0184] The relay UE may also notify the AMF or SMF of information about the remote UE whose connection with the relay UE has been released. The relay UE may also notify information indicating that the connection between the relay UE and the remote UE has been released.

[0185] The AMF may use this updated information to update the association information.

[0186] The AMF may include the association information in the context information of the relay UE.

[0187] During the PDU session release process or the process of transitioning the relay UE to the RRC_Idle or CM_Idle state, for example, the gNB may request the AMF to release the relay UE context. When the AMF receives a request to release the relay UE context, it performs the relay UE context release process. The AMF discards the relay UE context.

[0188] When the association information is included in the context information of the relay UE, a problem occurs in that the association information is released together with the release of the context of the relay UE. To avoid this, the AMF may retain the context information of the relay UE including the association information even when the relay UE is in the RRC_Idle or CM_Idle state. Alternatively, the AMF may retain only the association information in the context information of the relay UE even when the relay UE is in the RRC_Idle or CM_Idle state.

[0189] The context release message may include information indicating that some or all of the context information is retained. The retained context information may be association information. In this way, the AMF can determine whether to retain the association information even when the relay UE enters RRC_Idle or CM_Idle state.

[0190] Although the above description discloses that the AMF creates and stores the association information, the relay UE or the gNB may also create and store the association information. When performing a PDU session release process or a process of transitioning the relay UE to an RRC_Idle or CM_Idle state, the relay UE or the gNB may notify the AMF or the SMF of the association information. At that time, the relay UE or the gNB may notify the latest updated association information. The AMF retains the latest updated association information even when the relay UE enters an RRC_Idle or CM_Idle state.

[0191] By doing this, when a relay UE is in RRC_Idle or CM_Idle state, for example, if data is generated for a remote UE and the AMF receives a notification of the data generation for the remote UE, the AMF can easily detect the relay UE associated with the remote UE.

[0192] When the relay UE receives signaling indicating data generation for the remote UE in the RRC_Idle or CM_Idle state, the AMF notifies the relay UE associated with the remote UE of paging. The AMF may use the association information to detect the relay UE associated with the remote UE. The AMF notifies the relay UE of paging via the gNB connected to the relay UE.

[0193] The AMF may include, in the paging to the relay UE, information indicating that the paging is due to data generated for the remote UE. Alternatively, the AMF may include, in the paging to the relay UE, information about the remote UE. The AMF may include, as information about the remote UE, for example, a UE identifier, in the paging to the relay UE. In this way, the relay UE can recognize that the paging is due to data generated for the remote UE.

[0194] A relay UE that has received a paging establishes a PDU session with the NW. When the relay UE that has received a paging receives information indicating that the paging is due to data generated for the remote UE, it establishes a PDU session with the NW. The PDU session may be for relaying. The PDU session may be for communication with the remote UE that generated the data. In this way, a PDU session for communication between the remote UE and the NW can be established between the relay UE and the NW. Even after the relay UE has transitioned to the RRC_Idle or CM_Idle state, if data for the remote UE is generated, a PDU session can be established again between the relay UE and the NW, and communication between the remote UE and the NW can be performed using the PDU session.

[0195] The relay UE that has received the paging may transition to a connected state with the NW. The relay UE that has received the paging may transition to an RRC_Connected or CM_Connected state with the NW. In this way, the state between the relay UE and the NW becomes a connected state again, and communication between the remote UE and the NW becomes possible via the relay UE.

[0196] If a relay UE that receives a paging message from the AMF is not connected to a remote UE to which the generated data is to be sent, the relay UE may notify the gNB or AMF of information indicating that the relay UE is not connected to the remote UE to which the data is to be sent. The AMF may notify the SMF or UPF of information indicating that the relay UE is not connected to the remote UE to which the data is to be sent. The UPF may notify the AS or DN of information indicating that the relay UE is not connected to the remote UE to which the data is to be sent. The remote UE may be notified to the source of the data sent to the remote UE that the remote UE is not connected.

[0197] When the AMF receives information from the relay UE or the gNB indicating that the relay UE is not connected to the remote UE to which data is to be transmitted, the AMF may update the association information. This eliminates the need to retransmit paging to the relay UE. This reduces the amount of signaling and the risk of malfunction in communication processing between the remote UE and the NW via the relay UE.

[0198] It has been disclosed that the AMF notifies the relay UE of paging via the gNB. By using paging, the relay UE can perform discontinuous reception (DRX). By receiving paging from the gNB at a paging cycle (sometimes referred to as a paging DRX cycle in this disclosure), the relay UE can recognize whether data has been generated for the remote UE.

[0199] In this way, the relay UE can perform DRX, thereby enabling the power consumption of the relay UE to be reduced.

[0200] 14 to 16 are sequence diagrams showing an example of a method for communicating between a UE and a NW via a relay UE according to the first embodiment. FIGS. 14 to 16 are connected at the positions of boundaries BL1415 and BL1516. FIGS. 14 to 16 disclose a method for transitioning the relay UE to an RRC_Idle or CM_Idle state when there is no data between the remote UE and the NW. In step ST1401, the relay UE performs a process for establishing a PDU session with the gNB, AMF, SMF, and UPF, and establishes a PDU session between the relay UE and the UPF. The relay UE may perform the process for establishing the PDU session before performing relaying.

[0201] In Step ST1402, a discovery process is performed between the remote UE and the relay UE to detect a data transmission destination. In this discovery process, the relay UE may notify information indicating that it has relay capability between the NW and the UE. By receiving this information, the remote UE can recognize that it is able to communicate with the NW via the relay UE.

[0202] In this discovery process, the remote UE may notify information indicating that it is searching for a relay UE between the NW and the UE. The remote UE may notify information requesting connection to the NW. The remote UE may notify information requesting relay to the NW. The remote UE may notify information indicating that the destination is the NW. By receiving this information, the relay UE can recognize that the remote UE is requesting connection to the NW via its own relay UE.

[0203] In Step ST1403, a process of establishing a PC5 link is performed between the remote UE and the relay UE. As the process of establishing a PC5 link, for example, a PC5-S link establishment process is performed. In Step ST1403, the remote UE that has detected a relay UE for communication with the NW may perform a PC5-S link establishment process with the relay UE. Through this process, a PC5-S link is established between the remote UE and the relay UE. In this process, the remote UE may notify information requesting connection to the NW, information requesting relay to the NW, or information indicating that the destination is the NW. The relay UE can recognize that the remote UE is requesting connection to the NW via its own relay UE.

[0204] In Step ST1404, AS configuration may be notified between the remote UE and the relay UE. The AS configuration may include, for example, an SLRB configuration for data communication or an SLRB identifier. The configuration of a PC5 QoS flow between the remote UE and the relay UE and the configuration of an SLRB to which the PC5 QoS flow is mapped may be performed using the QoS required for the service communicated between the remote UE and the NW. For example, the remote UE derives QoS-related information corresponding to the generated service. The remote UE may configure a PC5 QoS flow and a PC5 QoS flow identifier from the QoS-related information. The remote UE also configures an SLRB to which the PC5 QoS flow is mapped. The remote UE may set an identifier for the SLRB configuration. In this way, PC5 communication that satisfies the QoS required for the service can be achieved.

[0205] The mapping information of QoS and SLRB setting may be configured in advance in the remote UE. When the remote UE is out of the coverage of the gNB, the remote UE may configure the SLRB using the mapping information of QoS and SLRB setting configured in advance in the remote UE.

[0206] The QoS-related information may include PC5 QoS parameters (sometimes referred to simply as QoS parameters, with PC5 omitted). The PC5 QoS parameters may include, for example, PQI (see Non-Patent Document 22 (TS23.287)). The QoS-related information may also include QoS characteristics (see Non-Patent Document 22 (TS23.287)). The PC5 QoS parameters and QoS characteristics may be referred to as a QoS profile.

[0207] The QoS-related information may include a PC5 QoS flow identifier (PQI), which may be used to identify the QoS flow established by the remote UE for data communication with the relay UE over PC5.

[0208] The PC5-S link establishment process may include a process for establishing a PC5-S link from a remote UE to a relay UE, or a process for establishing a PC5-S link from a relay UE to a remote UE, or a process for establishing a PC5-S link from a remote UE to a relay UE and from a relay UE to a remote UE.

[0209] After the PC5-S link establishment process from the remote UE to the relay UE and the process of notifying the relay UE of the AS setting for SL communication, a PC5-S link establishment process from the relay UE to the remote UE and the process of notifying the relay UE of the AS setting for SL communication may be performed.

[0210] After processing for establishing a PC5-S link from the remote UE to the relay UE and from the relay UE to the remote UE, processing for notifying the remote UE of the AS setting for SL communication to the relay UE and the relay UE to the remote UE of the AS setting for SL communication may be performed.

[0211] This allows for two-way SL communication, i.e., communication from the remote UE to the relay UE and communication from the relay UE to the remote UE.

[0212] In Step ST1405, the remote UE notifies the AMF of remote UE-related information via the relay UE and the gNB. In Step ST1406, the AMF stores the remote UE-related information in the context of the relay UE to associate the information with the relay UE. The AMF may store information about the remote UE in association with the relay UE. The AMF may store association information that associates the relay UE with the remote UE.

[0213] In Step ST1407, the AMF notifies the SMF of remote UE-related information. The AMF may notify the SMF of association information between the relay UE and the remote UE. In Step ST1408, the SMF notifies the UPF of remote UE-related information. The SMF may notify the SUPF of association information between the relay UE and the remote UE. In this way, the UPF can recognize that the PDU session established with the relay UE is for relaying with the remote UE. Therefore, for example, when DL data to the remote UE occurs, the UPF can transmit the DL data to the remote UE via the relay UE.

[0214] In Step ST1409, UL data communication is enabled between the remote UE and the UPF, and in Step ST1410, DL data communication is enabled between the UPF and the remote UE.

[0215] In Step ST1411, the UPF determines whether or not data is generated for the remote UE in the communication between the remote UE and the NW. For example, if no data is generated for a predetermined period of time, the UPF may determine that no data is generated. In Step ST1412, the UPF, which has determined that no data is generated for the remote UE, notifies the SMF of a release request for the PDU session between the relay UE and the NW used for the communication between the remote UE and the NW via the relay UE. The UPF may use association information between the remote UE and the relay UE to identify the PDU session between the relay UE and the NW used for the communication between the remote UE and the NW via the relay UE. The UPF can now determine which relay UE and NW to request the release of the PDU session established between for the data to the remote UE.

[0216] In Step ST1413, the SMF notifies the AMF of a release request for the PDU session between the relay UE and the NW. In Step ST1414, the AMF performs a release process for the PDU session between the relay UE and the NW between the relay UE, the gNB, the SMF, and the UPF. In Step ST1415, an RRC connection release process is performed between the relay UE and the gNB, and a CM connection release process is performed between the relay UE, the gNB, and the AMF. As a result, the relay UE transitions to the RRC_Idle or CM_Idle state. The relay UE that has transitioned to the RRC_Idle or CM_Idle state starts receiving paging with the DRX setting for paging broadcast from the gNB.

[0217] In step ST1416, the AMF holds remote UE-related information. The AMF holds association information that associates the remote UE with the relay UE. By holding the association information between the remote UE and the relay UE even after the relay UE transitions to the RRC_Idle or CM_Idle state, as described above, when data is sent to the remote UE or when an incoming call occurs, the AMF can determine the relay UE to which paging should be notified.

[0218] In step ST1417, the UPF receives data from the AS or DN for the remote UE. In step ST1418, the UPF holds the data for the remote UE. In step ST1419, the UPF notifies the SMF of the occurrence of data for the remote UE. In step ST1420, the SMF that has received the notification may notify the UPF of a data occurrence notification response. If there is no data occurrence notification response, the UPF may notify the remote UE again of the occurrence of data. This can reduce malfunctions. In step ST1421, the SMF notifies the AMF of the occurrence of data for the remote UE. In step ST1422, the AMF that has received the notification may notify the SMF of a data occurrence notification response. If there is no data occurrence notification response, the SMF may notify the SMF again of the occurrence of data. This can reduce malfunctions.

[0219] The AMF that has received the data generation notification for the remote UE identifies which relay UE to notify of the paging, using the association information between the remote UE and the relay UE that it has stored. In Step ST1423, the AMF notifies the gNB connected to the identified relay UE of the paging. As described above, the AMF may include information indicating that the paging is for the remote UE in the paging. In Step ST1424, the gNB notifies the relay UE of the paging. The gNB may include information indicating that the paging is for the remote UE in the paging.

[0220] In Step ST1425, the relay UE that has received the paging performs a PDU session establishment process. It may also perform a service request process. The service request process causes the relay UE to perform a PDU session establishment process. In this process, the relay UE establishes an RRC connection with the gNB. The relay UE also establishes a CM connection with the AMF. The information in the paging indicating that the paging is for a remote UE allows the relay UE to recognize that the paging is for a remote UE. The relay UE that recognizes that the paging is for a remote UE can establish a PDU session for relaying.

[0221] In step ST1426, the UPF transmits the data that was held for the remote UE to the gNB connected to the relay UE, and the gNB transmits the data to the relay UE, which then becomes able to transmit the data to the remote UE.

[0222] Furthermore, since a PDU session is established between the relay UE and the UPF in Step ST1425, data (sometimes referred to as UL data) can also be transmitted from the remote UE to the NW.

[0223] This allows the relay UE to transition to the RRC_Idle or CM_Idle state in communication between the remote UE and the NW via the relay UE. Even when the relay UE transitions to the RRC_Idle or CM_Idle state, RRC connection and CM connection become possible again as data is generated, and a PDU session for relaying can be established.

[0224] The case where data is generated from an AS, DN, etc. to a remote UE when a relay UE is in RRC_Idle or CM_Idle state has been disclosed. Here, the case where service data is generated from a remote UE will be disclosed.

[0225] The remote UE transmits the generated data to the relay UE. When the relay UE receives data from the remote UE, it performs a process of establishing a PDU session with the NW. By doing this, even after the relay UE has transitioned to the RRC_Idle or CM_Idle state, if data is generated from the remote UE, a PDU session can be established again between the relay UE and the NW. This enables communication between the remote UE and the NW using the PDU session. The relay UE that has received data from the remote UE may transition to a connected state with the NW. The relay UE that has received data from the remote UE may transition to an RRC_Connected or CM_Connected state with the NW. By doing this, the state between the relay UE and the NW becomes a connected state again, and communication between the remote UE and the NW becomes possible via the relay UE.

[0226] Another method is disclosed. The remote UE notifies the relay UE of a PDU session establishment request. The PDU session may be a PDU session for relay. The PDU session establishment request may include reason information. The reason information indicates the reason for requesting PDU session establishment. The reason information may be, for example, data generation or a relay processing request. By providing reason information and including it in the PDU session establishment request, the relay UE can recognize the reason for which the PDU session is requested. Upon receiving the PDU session establishment request from the remote UE, the relay UE performs PDU session establishment processing with the NW. After establishing the PDU session, the relay UE may notify the remote UE of completion of PDU session establishment. The remote UE transmits data to the relay UE.

[0227] With the establishment of the PDU session, the relay UE may transition to a connected state with the NW. The relay UE may transition to an RRC_Connected or CM_Connected state with the NW. In this way, the state between the relay UE and the NW becomes a connected state again, and communication between the remote UE and the NW becomes possible via the relay UE.

[0228] The remote UE may notify the relay UE of an RRC connection request. Alternatively, the remote UE may notify the relay UE of a CM connection request. Reason information may be included in the RRC connection request or the CM connection request. The reason information indicates the reason for requesting the RRC connection or the CM connection. The reason information may be, for example, data generation or a relay processing request. By providing reason information and including it in the request, the relay UE can recognize the reason for the RRC connection or the CM connection. Upon receiving the request, the relay UE may transition to an RRC_Connected or CM_Connected state with the NW. In this way, the state between the relay UE and the NW becomes connected again, and communication between the remote UE and the NW becomes possible via the relay UE. Furthermore, the remote UE may notify the relay UE of a request to establish a PDU session. By establishing a PDU session with the NW, the relay UE can communicate data from the remote UE to the NW.

[0229] The relay UE may notify the remote UE whether a PDU session has been established with the NW. The relay UE may notify the remote UE whether it is in an RRC_Idle state with the NW. The relay UE may notify the remote UE whether it is in a CM_Idle state with the NW. RRC state information or CM state information may be provided. The relay UE may notify the remote UE of the RRC state information and / or CM state information with the NW. The information may be notified using PC5-S signaling or RRC signaling. The information may also be notified using PSCCH or PSSCH. Early notification is possible. In this way, the remote UE can recognize the connection status between the relay UE and the NW.

[0230] When service data occurs in the remote UE, the remote UE may determine whether to notify the above-mentioned PDU session establishment request, RRC connection request, or CM connection request depending on the connection status between the relay UE and the NW.

[0231] When the connection between the relay UE and the NW is released or when the PDU session established between the relay UE and the NW is released, the relay UE may notify the remote UE of information indicating the release of the connection between the relay UE and the NW or the release of the PDU session between the relay UE and the NW. For example, when the connection between the relay UE and the NW is released due to deterioration in communication quality between the relay UE and the gNB, the relay UE notifies the remote UE of information indicating the release of the connection between the relay UE and the NW. The remote UE that receives the information may change the relay UE.

[0232] The information may be notified using PC5-S signaling or RRC signaling. Furthermore, the information may be notified using PSCCH or PSSCH. This allows for early notification. For example, this allows a remote UE to quickly change a relay UE that can relay with the network.

[0233] This section describes a case where a relay UE moves across tracking areas. The relay UE may perform a Tracking Area Update (TAU) process with the NW. The relay UE notifies the AMF of information related to its own relay UE and information related to the connected remote UE. The relay UE may notify the information during or after the TAU process. The AMF, having received the information related to the relay UE and the remote UE, creates association information. The above-mentioned method may be applied as appropriate as processing in the AMF. In this way, even in a situation where the relay UE moves across tracking areas, when data for the remote UE is generated, it becomes possible for the NW to transmit data to the remote UE.

[0234] In a situation where a relay UE moves across tracking areas, a connection with a remote UE may not be maintained. In such a case, the relay UE may not notify the AMF of information related to the remote UE with which the connection is not maintained. Alternatively, the relay UE may notify the AMF of the release or discard of information related to the remote UE. Furthermore, the relay UE may not establish a PDU session used for relay communication with the remote UE. In this way, when the connection between the relay UE and the remote UE is not maintained, it is possible to avoid establishing a PDU session or retaining association information with the remote UE in the AMF. This makes it possible to avoid unnecessary processing, thereby reducing malfunctions and power consumption as a system.

[0235] A method for a remote UE to change a relay UE is disclosed. The remote UE performs a discovery process to detect a relay UE having a PDU session for relaying. The relay UE may transmit information indicating whether it has a PDU session for relaying in the discovery process. For example, the relay UE may transmit the information by including it in a solicitation message. In this way, the remote UE can detect a relay UE having a PDU session for relaying in the discovery process.

[0236] The remote UE measures the reception quality (which may be reception power) from one or more relay UEs, including the connected relay UE, and selects the relay UE with the best communication quality. If the selected relay UE is different from the connected relay UE (sometimes referred to as S-relay UE), the remote UE releases the PC5-S link with the S-relay UE and establishes a PC5-S link with the selected relay UE (sometimes referred to as T-relay UE).

[0237] When a remote UE performs a process to release the PC5-S link with an S-relay UE, the remote UE may perform the release process without notifying the S-relay UE. The S-relay UE may measure the period since the last communication with the remote UE. The S-relay UE may release the PC5-S link with the remote UE if the period since the last communication with the remote UE exceeds a predetermined period. The predetermined period may be managed by a timer.

[0238] The S-relay UE may release the PC5-S link if there is no data on the resource periodically selected and reserved by the remote UE for a predetermined number of consecutive times.

[0239] As a PC5-S link release process, resources used for the PC5-S link connection may be released. Also, an RRC release process may be performed. Resources used for the RRC connection may be released.

[0240] When a PC5-S link is established between the remote UE and the T-relay UE, the T-relay UE establishes a PDU session for relaying with the NW. As a method for this, the above-mentioned method may be applied as appropriate.

[0241] In this way, the T-relay UE and the remote UE are associated with each other. This enables data communication between the remote UE and the network via the T-relay UE. If there is no data between the remote UE and the network, the PDU session may be released. The connection between the T-relay UE and the network may be released. As a method for this, the above-mentioned methods may be applied as appropriate.

[0242] In this way, even if the remote UE changes the relay UE, communication between the remote UE and the NW is possible via the changed relay UE.

[0243] By using the method disclosed herein, in communication between a remote UE and a network via a relay UE, the relay UE can transition to the CM_Idle or RRC_Idle state. Since the relay UE can receive paging messages in the DRX cycle for paging, it is possible to reduce the power consumption of the relay UE.

[0244] In the above description, it has been disclosed that a PDU session is established between a relay UE and a CN for communication between a remote UE and a network. One PDU session may be established for relaying communication between multiple remote UEs and a network. In other words, a relay UE may relay communication between multiple remote UEs and a network through one relay PDU session established with a CN. In this way, multiple remote UEs can communicate with a network via one relay UE.

[0245] Communication between a new remote UE and a NW may be performed using the PDU session established for initial communication between the remote UE and the NW. At this time, the PDU session may be modified. For example, if the PDU session initially established for relaying is not suitable for the service performed between the new remote UE and the NW, the PDU session may be modified. The relay UE may request modification of the PDU session. The remote UE may notify the relay UE of information about the service to be communicated with the NW. The relay UE may use the information about the service obtained from the remote UE to determine whether to modify the PDU session.

[0246] A CN node, such as an AMF, SMF, or UPF, may request modification of a PDU session. The remote UE may notify the CN node via a relay UE or a gNB of information about services communicating with the NW. The CN node may use the information about services obtained from the remote UE to determine whether to modify the PDU session.

[0247] A PDU session for relay may be set for each relay UE. A PDU session for relay may be managed for each relay UE. A PDU session for relay may be managed by an identifier of the relay UE. An identifier of the relay UE may be used as an identifier of the UE for which a PDU session for relay is set. An identifier of the relay UE may be included in the setting information of the PDU session for relay.

[0248] In a situation where multiple remote UEs are communicating with a network using one PDU session, even when communication between one remote UE and the network is terminated, the PDU session may be modified. The above-mentioned method may be applied appropriately. Whether to modify the PDU session may be determined using information about the service for which communication between the remote UE and the network is terminated.

[0249] The above-mentioned PDU session release process is performed for one PDU session. In communications between multiple remote UEs and a network using one relay PDU session, the above-mentioned release process may be performed when communications between all remote UEs and the network are temporarily suspended. For example, the above-mentioned release process may be performed during a period when communications between all remote UEs and the network are not being performed. These methods may be applied as appropriate to the above-mentioned methods.

[0250] Another method is disclosed. Multiple PDU sessions may be established for relaying communications between multiple remote UEs and the NW. In other words, the relay UE may relay communications between multiple remote UEs and the NW using multiple relay PDU sessions established with the CN. For example, one PDU session may be established for communications between each remote UE and the NW. In this way, multiple remote UEs can communicate with the NW via one relay UE.

[0251] For the first communication between one remote UE and the NW, one PDU session is established between the relay UE and the CN. For the communication between a new remote UE and the NW, a new PDU session is established in addition to the previously established PDU session between the relay UE and the CN. A PDU session appropriate for the service to be performed between the new remote UE and the NW is established.

[0252] After the PC5-S link is established between the new remote UE and the relay UE, a new PDU session may be established between the relay UE and the CN for relay communication between the new remote UE and the NW, allowing the establishment of a PDU session suitable for communication between the remote UE and the NW.

[0253] Before a PC5-S link is established between the new remote UE and the relay UE, a new PDU session for relay communication between the new remote UE and the NW may be established between the relay UE and the CN. When the new remote UE communicates with the NW via the relay UE, the already established PDU session can be used, and communication between the remote UE and the NW via the relay UE can be started early.

[0254] Multiple PDU sessions are established for one relay UE. Each PDU session may be configured for each remote UE. Each PDU session may be managed for each remote UE. Each PDU session may be managed by the identifier of the remote UE. The identifier of the remote UE may be used as the identifier of the UE for which each PDU session is configured. The identifier of the remote UE may be included in the configuration information of the PDU session. Each PDU session may be managed not only by the identifier of the remote UE, but also by the identifier of the relay UE and the identifier of the remote UE. For example, the identifier of the remote UE may be set in addition to the identifier of the relay UE in the configuration information of the PDU session. In this way, it becomes possible to identify the PDU session for each remote UE.

[0255] In a situation where multiple remote UEs are communicating with a NW using multiple PDU sessions, even when communication between one remote UE and the NW is terminated, the PDU session for that remote UE may be released. The PDU session release process described above may be performed for each PDU session for each remote UE.

[0256] In communications between multiple remote UEs and a network using multiple relay PDU sessions, if communications between all remote UEs and the network are temporarily lost, the above-described RRC connection release process or CM connection release process may be performed. For example, the above-described RRC connection release process or CM connection release process may be performed during a period when communications between all remote UEs and the network are not being performed. These methods may be appropriately applied using the above-described methods.

[0257] Another method is disclosed. The above-described method of establishing one PDU session for relaying communications between multiple remote UEs and a network may be combined with the method of establishing multiple PDU sessions for relaying communications between multiple remote UEs and a network. One or more PDU sessions may be established for relaying communications between one or more remote UEs and a network. For example, one PDU session may be established for a group of multiple remote UEs for relaying communications between the remote UEs in the group and the network. For example, one PDU session may be established for one or more remote UEs using the same service. This allows for flexible establishment of PDU sessions depending on the service being communicated between the remote UE and the network.

[0258] Variation 1 of Embodiment 1 Another method for solving the problem described in the first embodiment will be disclosed.

[0259] The UE determines the RRC state (Preferred RRC State) desired for other UEs. Preferred RRC states include RRC_Idle, RRC_Inactive, and RRC_Connected. RRC state information desired for other UEs may be provided. The UE notifies the gNB of the RRC state information desired for other UEs. The gNB may use the received desired RRC state information to transition the RRC state of the other UE.

[0260] The remote UE determines the RRC state desired for the relay UE. The remote UE notifies the gNB of the RRC state information desired for the relay UE. The remote UE notifies the gNB connected to or camped on the relay UE of the RRC state information desired for the relay UE via the relay UE. The gNB connected to or camped on the relay UE can transition the RRC state of the relay UE, so it is preferable for the remote UE to notify the gNB connected to or camped on the relay UE of the RRC state information desired for the relay UE.

[0261] For example, when there is no communication data between the remote UE and the NW, the remote UE determines the RRC state desired for the relay UE to be RRC_Idle. The remote UE sets the RRC state information desired for the relay UE to RRC_Idle and notifies the gNB connected to the relay UE of the RRC state information desired for the relay UE via the relay UE. The gNB connected to the relay UE may transition the RRC state of the relay UE using the received RRC state information desired for the relay UE. For example, if the relay UE is in an RRC connected state, the gNB may perform an RRC connection release procedure to transition the relay UE to an RRC_Idle state.

[0262] The requested RRC status information may include information for identifying which UE the request is for. Information for identifying which UE the request is for may be notified together with the requested RRC status information. In this way, the node that receives the requested RRC status information can recognize which UE the RRC status information is for.

[0263] The requested RRC status information may include information for identifying which UE has made the request. Information for identifying which UE has made the request may be notified together with the requested RRC status information. In this way, the node that receives the requested RRC status information can recognize which UE has made the request.

[0264] The remote UE may notify the relay UE of the desired RRC state information via PC5-S signaling. Even if RRC configuration for data transmission is not configured on the PC5 link, the desired RRC state information can be notified between the remote UE and the relay UE. This allows for early notification of the desired RRC state information. Alternatively, the remote UE may notify the relay UE of the desired RRC state information via PC5 RRC signaling. This allows for RRC processing in the relay UE. As will be described later, when the relay UE notifies the gNB of the desired RRC state information via RRC signaling, the processing can be unified within the RRC. This avoids complexity and reduces malfunctions.

[0265] When the relay UE is in the RRC_Connected state, the relay UE may notify the gNB connected to the relay UE of the desired RRC status information received from the remote UE by RRC signaling. For example, as described above, when the relay UE notifies the gNB of the desired RRC status information received from the remote UE by using PC5 RRC signaling between the remote UE and the relay UE, this can avoid the process from becoming complicated. The desired RRC status information may be included in UE assistance information and notified by RRC signaling.

[0266] When a relay UE is in RRC_Idle or RRC_Inactive state, the relay UE may notify the camped gNB of the desired RRC status information received from the remote UE using a Random Access (RA) procedure. For example, in the case of a 4-step RACH (see Non-Patent Document 16 (TS38.300)), the relay UE may notify the desired RRC status information using MSG3. In the case of MSG3, it is possible to improve the probability of arrival by using a collision avoidance procedure. The relay UE may notify the desired RRC status information using, for example, a 2-step RACH procedure. In the case of a 2-step RACH (see Non-Patent Document 16 (TS38.300)), the relay UE may notify the desired RRC status information using MSGA. The relay UE may notify the desired RRC status information using MSGA using PUSCH. This allows for earlier notification.

[0267] When the relay UE is in the RRC_Idle or RRC_Inactive state, the relay UE may establish an RRC connection with the gNB and then notify the gNB of the desired RRC status information received from the remote UE, using the method used when the relay UE is in the RRC_Connected state as described above.

[0268] In this way, the remote UE can notify the gNB to which the relay UE is connected of the RRC state information it has determined and requested from the relay UE. The gNB can recognize the requested RRC state, which UE is making the request, and which UE the request is for from the received requested RRC state information. The gNB may use the received requested RRC state information to transition or maintain the RRC state of the relay UE.

[0269] For example, when the relay UE is in an RRC connected state and the remote UE determines that there is no more communication data between the relay UE and the NW, the remote UE sets the RRC state information it requests the relay UE to RRC_Idle and notifies the relay UE of the setting information. The remote UE may include information indicating the remote UE's request and the request to the relay UE in the notification. The relay UE notifies the gNB to which it is connected. The gNB that receives the information may use the information to decide to transition the relay UE to the RRC_Idle state. The gNB performs an RRC connection release process with the relay UE.

[0270] The gNB may notify the AMF of a release request for the PDU session between the relay UE and the NW. The AMF that receives the request may perform a release process for the PDU session between the relay UE and the NW. The AMF may also perform a CM connection release process with the relay UE. The relay UE that has transitioned to the RRC_Idle or CM_Idle state receives paging from the gNB in ​​a paging DRX cycle. As these methods, the above-mentioned methods may be applied as appropriate. Even after the relay UE has transitioned to the RRC_Idle or CM_Idle state, if data for the remote UE is generated, it is possible to transmit data to the remote UE.

[0271] The gNB may make a decision different from the RRC state request for the relay UE. The gNB may notify the remote UE of the RRC state of the relay UE determined by the gNB. The remote UE can then know what the state of the relay UE will be. For example, the remote UE can decide whether to make a request again. For example, the remote UE can decide whether to change the relay UE.

[0272] If the gNB determines that the RRC state for the relay UE is different from the request, it may notify the remote UE of a rejection message. The gNB may include reason information in the rejection message. The remote UE can recognize the reason why the request was rejected. The gNB may also include the RRC state determined by the gNB in ​​the rejection message. The remote UE can then recognize what the state of the relay UE will be. For example, the remote UE can determine whether to make a request again. For example, the remote UE can determine whether to change the relay UE.

[0273] Figures 17 to 19 are sequence diagrams showing an example of a method for communicating between a UE and a NW via a relay UE, according to Variant 1 of Embodiment 1. Figures 17 to 19 are connected at the positions of borders BL1718 and BL1819. Figures 17 to 19 disclose a method for transitioning a relay UE to an RRC_Idle or CM_Idle state when there is no data between the remote UE and the NW, by the remote UE notifying a gNB connected to the relay UE of RRC state information requested of the relay UE. In Figures 17 to 19, steps common to Figures 14 to 16 are assigned the same step numbers, and common explanations will be omitted.

[0274] In Steps ST1409 and ST1410, the remote UE transmits and receives data to and from the NW. The remote UE determines whether or not data is generated in communication between the remote UE and the NW. For example, the remote UE may determine that no data is generated when it recognizes from service-related information that no data is generated for a predetermined period of time. The remote UE that has determined that no data is generated sets the RRC state information that it requests the relay UE to RRC_Idle. In Step ST1501, the remote UE notifies the gNB to which the relay UE is connected of the RRC state information that it requests the UE to send, via the relay UE. The remote UE may include information indicating which UE the request is from, in the RRC state information.

[0275] The gNB that has received the RRC state information can recognize that the RRC state request for the relay UE is RRC_Idle. Furthermore, since the request is from the remote UE, the gNB can recognize that it is a request for communication for relaying. In Step ST1502, the gNB uses the RRC state information requested for the relay UE to determine whether to transition or maintain the RRC state of the relay UE. Here, the gNB determines to transition the relay UE to RRC_Idle.

[0276] In Step ST1503, the gNB notifies the AMF of a request to release the PDU session for relay between the relay UE and the NW. In Step ST1414, the AMF performs a PDU session release process between the relay UE and the NW. Step ST1414 and subsequent steps are common to Figures 14 to 16, so description thereof will be omitted.

[0277] In this way, the remote UE can notify the gNB connected to the relay UE of the RRC state it requests the relay UE to be in. The gNB can recognize the request and can transition or maintain the relay UE in the RRC state of the relay UE requested by the remote UE.

[0278] The remote UE may notify the relay UE of RRC state information requested from the relay UE. For example, when multiple remote UEs are connected to the relay UE, the multiple remote UEs may notify the relay UE of RRC state information requested from the relay UE. The relay UE may derive RRC state information requested for itself using the RRC state information requested from the relay UE received from one or more remote UEs.

[0279] For example, if all of the RRC status information requested to the relay UE received from one or more remote UEs is RRC_Idle, the relay UE sets the RRC status information requested to the own UE to RRC_Idle.For example, if any one of the RRC status information requested to the relay UE received from one or more remote UEs is RRC_Connected, the relay UE sets the RRC status information requested to the own UE to RRC_Connected.

[0280] The relay UE notifies the gNB to which the relay UE is connected or camped on of the derived RRC state information desired for the relay UE. The gNB that receives the information may use the information to determine whether to transition or maintain the RRC state of the relay UE. For example, when the gNB receives from the relay UE that the RRC state information desired for the relay UE is RRC_Idle, if the relay UE is in an RRC connected state, the gNB may perform an RRC connection release procedure to transition the relay UE to the RRC_Idle state.

[0281] The above-mentioned method may be applied as a method for a remote UE to notify a relay UE of RRC status information requested from another UE. The above-mentioned method may be applied as a method for a relay UE to notify a gNB of RRC status information requested from the relay UE.

[0282] In this way, for example, when a relay UE is connected to multiple remote UEs, the relay UE can set the RRC state desired for the relay UE and notify the gNB of the RRC state desired for the relay UE. The gNB can use the received information to transition or maintain the RRC state of the relay UE. Therefore, it becomes possible to control the RRC state of the relay UE according to the data communication states of the multiple remote UEs connected to the relay UE.

[0283] The remote UE may notify the AMF of RRC state information requested from another UE. The remote UE may notify the AMF via the relay UE and the gNB of the RRC state information requested from the relay UE. Furthermore, the relay UE may notify the AMF of the RRC state information requested from the relay UE. The AMF that has received the information may use the information to determine whether to release or maintain the PDU session between the relay UE and the NW. For example, if the AMF receives from the remote UE via the gNB that the RRC state information requested from the relay UE is RRC_Idle, the AMF may release the PDU session between the relay UE and the NW. Upon releasing the PDU session, the gNB may perform an RRC connection release procedure with the relay UE. Furthermore, the AMF may perform a CM connection release procedure. In this way, the relay UE can transition to an RRC_Idle or CM_Idle state. The relay UE that has transitioned to the RRC_Idle or CM_Idle state receives paging from the gNB at a paging DRX cycle.

[0284] Desired CM state information may be provided. Desired CM states include CM_Idle and CM_Connected. Desired CM state information may be provided by the UE itself. Desired CM state information may be provided for other UEs. The UE may notify the AMF of the desired CM state information. The UE may notify the AMF of the desired CM state information using NAS signaling. The UE may notify the gNB of the information using RRC signaling, and the gNB may notify the AMF of the information using N2 signaling. The UE may notify the UE connected via PC5 of the desired CM state information. The UE may use PC5-S signaling or PC5 RRC signaling. The AMF that receives the desired CM state information determines which UE the CM state information is desired for, and uses the CM state information of the UE to determine whether to transition or maintain the CM state of the UE.

[0285] For example, when the remote UE determines that there is no more communication data between the remote UE and the NW, it sets the CM state information requested of the relay UE to CM_Idle and notifies the AMF of this setting information via the relay UE and the gNB. When the relay UE is in a CM connection, the AMF determines to transition the relay UE to CM_Idle using the received CM state information requested of the relay UE, and performs CM connection release processing. With the release of the CM connection between the relay UE and the NW, the gNB executes RRC connection release processing with the relay UE. In this way, it is possible to transition the relay UE to the CM_Idle or RRC_Idle state.

[0286] The AMF may make a decision different from the CM state request for the relay UE. The AMF may notify the remote UE of the CM state of the relay UE determined by the AMF. The remote UE can then know what the state of the relay UE will be. For example, the remote UE can decide whether to make a request again. For example, the remote UE can decide whether to change the relay UE.

[0287] If the AMF determines that the CM state of the relay UE is different from the request, it may notify the remote UE of a rejection message. The AMF may include reason information in the rejection message. The remote UE can recognize the reason why the request was rejected. The AMF may also include the CM state determined by the gNB in ​​the rejection message. The remote UE can then recognize what the state of the relay UE will be. For example, the remote UE can determine whether to make a request again. For example, the remote UE can determine whether to change the relay UE.

[0288] The remote UE may notify the relay UE of the CM state information it requests the relay UE to provide. For example, if multiple remote UEs are connected to the relay UE, the multiple remote UEs may notify the relay UE of the CM state information they request the relay UE to provide. The relay UE may derive the CM state information it requests from itself using the CM state information it receives from one or more remote UEs.

[0289] For example, if all of the CM status information requested from the relay UE received from one or more remote UEs is CM_Idle, the relay UE sets the CM status information requested from the own UE to CM_Idle.For example, if any one of the CM status information requested from the relay UE received from one or more remote UEs is CM_Connected, the relay UE sets the CM status information requested from the own UE to CM_Connected.

[0290] The relay UE notifies the gNB to which the relay UE is connected or camped on of the derived CM state information desired for the relay UE. The gNB that receives the information may use the information to determine whether to transition or maintain the CM state of the relay UE. For example, when the gNB receives from the relay UE that the CM state information desired for the relay UE is CM_Idle, if the relay UE is in a CM connected state, the gNB may send a CM connection release request to the AMF to transition the relay UE to the CM_Idle state.

[0291] The relay UE may notify the AMF of the derived CM state information desired for the relay UE. The relay UE may notify the AMF via the gNB to which the relay UE is connected or the gNB on which the relay UE is camped. The AMF that receives the information may use the information to determine whether to transition or maintain the CM state of the relay UE. For example, when the AMF receives from the relay UE that the CM state information desired for the relay UE is CM_Idle, if the relay UE is in a CM connected state, the AMF may perform a CM connection release process to transition to the CM_Idle state.

[0292] As a method for the remote UE to notify the relay UE of the CM state information requested from other UEs, the above-mentioned method for notifying the requested RRC state information may be appropriately applied.

[0293] In this way, for example, when a relay UE is connected to multiple remote UEs, the relay UE can set a desired CM state for itself and notify the gNB or AMF of the desired CM state for itself. The gNB or AMF can use the received information to transition or maintain the CM state of the relay UE. Therefore, it is possible to control the CM state of the relay UE according to the data communication states of multiple remote UEs connected to the relay UE.

[0294] By using the method disclosed herein, in communication between a remote UE and a network via a relay UE, the relay UE can transition to the CM_Idle or RRC_Idle state depending on whether the remote UE has data to communicate with the network. Since the relay UE can receive data in the paging DRX cycle, it is possible to reduce the power consumption of the relay UE.

[0295] Variation 2 of Embodiment 1 Another method for solving the problem described in the first embodiment will be disclosed.

[0296] In the first embodiment, a method for transitioning a relay UE to a CM_Idle or RRC_Idle state in communication between a remote UE and a NW via a relay UE has been disclosed. The relay UE that has transitioned to the CM_Idle or RRC_Idle state receives paging from the gNB in ​​a paging DRX cycle. Paging methods include CN initiated paging and RAN initiated paging.

[0297] As CN-initiated paging, there is a method of using a paging DRX cycle broadcast by a cell (sometimes referred to as a cell-specific paging DRX cycle). In this method, the cell sets the paging DRX cycle. The gNB may also set the paging DRX cycle of the cell configured by the gNB. The cell's paging DRX cycle is set for each cell. For this reason, in communication between a remote UE and a NW via a relay UE, it is not possible to set a cell-specific paging DRX cycle suitable for the relay UE.

[0298] There is a method of using a UE-specific paging DRX cycle for CN-initiated paging. This method makes it possible to set a paging DRX cycle for each UE. Therefore, in communication between a remote UE and a network via a relay UE, a paging DRX cycle can be set for each relay UE. However, in communication between a remote UE and a network via a relay UE, it is the remote UE that generates communication data, and the relay UE does not generate communication data. Therefore, it is not possible to set a paging DRX interval suitable for the service occurring between the remote UE and the network. A method for solving this problem is disclosed.

[0299] The UE sets DRX-related information of other UEs that it requests. In this disclosure, this information is referred to as DRX-related information requested from other UEs. The UE determines the DRX-related information that it requests from other UEs. Specific examples of the requested DRX-related information include a DRX cycle for paging, a paging frame, and a paging slot.

[0300] Other specific examples of desired DRX-related information include a paging reception period and a cycle of the paging reception period. The paging reception period and the cycle of the paging reception period may be an integer multiple of the paging DRX cycle for each cell. The integer value may be used as information on the paging reception period and the cycle of the paging reception period. As a paging DRX processing method using this information, for example, the UE may receive a paging during a paging reception period, and then receive a paging during the next paging reception period one paging reception period cycle after the start of the paging reception period.

[0301] The above specific examples may be combined as the desired DRX-related information.

[0302] The UE notifies the AMF of DRX-related information it requests from other UEs. The AMF uses the received requested DRX-related information to derive paging DRX configuration for the other UEs. The paging DRX configuration may be a UE-specific paging DRX configuration. Specific examples of paging DRX configuration include a paging DRX cycle, a paging frame, and a paging slot.

[0303] Other specific examples of the paging DRX setting include a paging reception period and a cycle of the paging reception period. The paging reception period and the cycle of the paging reception period may be an integer multiple of the paging DRX cycle for each cell. The integer value may be used as information on the paging reception period and the cycle of the paging reception period.

[0304] The above-mentioned specific examples may be combined as the DRX setting for paging.

[0305] The requested DRX-related information may include information for identifying which UE the request is for. Information for identifying which UE the request is for may be notified together with the requested DRX-related information. In this way, a node that receives the requested DRX-related information can recognize which UE the DRX-related information is for.

[0306] The requested DRX-related information may include information for identifying which UE has made the request. Information for identifying which UE has made the request may be notified together with the requested DRX-related information. In this way, a node that receives the requested DRX-related information can recognize which UE has requested the DRX-related information.

[0307] The requested DRX-related information may include information about the service. Information about the service may be notified together with the requested DRX-related information. For example, an identifier for identifying the service, the QoS of the service, etc. may be notified. In this way, a node that receives the requested DRX-related information can recognize what service the requested DRX corresponds to.

[0308] The AMF notifies the other UE of the derived other UE-specific paging DRX configuration. The AMF may notify the other UE of the derived configuration via a gNB to which the other UE is connected. The other UE receives paging using the received other UE-specific paging DRX configuration. In this way, it is possible to notify a UE other than the UE that requested the DRX-related information of a UE-specific paging DRX configuration according to the requested DRX-related information. The UE can receive paging using the paging DRX configuration set according to the DRX-related information requested by the other UE.

[0309] For example, in communication between a remote UE and a NW via a relay UE, the remote UE determines DRX-related information requested from the relay UE. The remote UE notifies the AMF of the DRX-related information requested from the relay UE. The remote UE notifies the AMF of the DRX-related information requested from the relay UE via the relay UE and the gNB. The AMF performs paging DRX configuration for the relay UE using the received DRX-related information requested from the relay UE. The paging DRX configuration may be a paging DRX configuration specific to the relay UE. The paging DRX configuration may be for the relay.

[0310] The remote UE may notify the AMF of the DRX-related information requested from the relay UE when the DRX-related information requested from the relay UE occurs in the remote UE. As another method, the remote UE may include the DRX-related information requested from the relay UE in the remote UE-related information notified from the remote UE to the AMF and notify the AMF. As another method, the DRX-related information requested from the relay UE may be notified in the registration process or service request process of the remote UE. The registration process or service request process of the remote UE may be performed to the AMF via the relay UE and the gNB connected to the relay UE. When the remote UE knows in advance the DRX-related information requested from the relay UE, the notification can be made early.

[0311] As a method for the remote UE to notify the relay UE of the DRX-related information it requests the relay UE to transmit, it is preferable to appropriately apply the method for the remote UE to notify the relay UE of the requested RRC state information, which is disclosed in the first modification of the first embodiment, and similar effects can be obtained.

[0312] The relay UE may notify the AMF of the DRX-related information requested of the relay UE by NAS signaling. Alternatively, RRC signaling may be used for notification from the relay UE to the gNB, and N2 signaling may be used for notification from the gNB to the AMF. Furthermore, as a method for notifying the gNB of the DRX-related information requested of the relay UE, the method disclosed in Variant 1 of Embodiment 1 for notifying the gNB of the requested RRC state information may be applied as appropriate. Similar effects can be obtained.

[0313] The AMF notifies the relay UE of the derived DRX configuration for paging dedicated to the relay UE. The AMF may notify the derived configuration via the gNB to which the relay UE is connected. The relay UE receives paging using the received DRX configuration for paging dedicated to the relay UE.

[0314] The AMF may notify the relay UE of the paging DRX configuration for each relay UE after the AMF derives the configuration. For example, the AMF may notify the relay UE of the configuration in a PDU session establishment process between the relay UE and the NW. For example, the AMF may notify the relay UE of the configuration in an RRC connection release process or a CM connection release process.

[0315] The AMF may notify the relay UE of the paging DRX configuration for each relay UE by NAS signaling. Alternatively, the AMF may notify the gNB by N2 signaling, and the gNB may notify the relay UE by RRC signaling.

[0316] The AMF may configure a DRX for paging that is different from the DRX-related information requested of the relay UE. The AMF may not configure a DRX for paging for each UE individually. The AMF may notify the remote UE of the DRX for paging configured for the relay UE. The remote UE can recognize the DRX for paging configured for the relay UE. The AMF may include reason information in the notification. If the AMF configures a DRX for paging that is different from the DRX-related information requested of the relay UE, the remote UE can recognize the reason. This allows the remote UE to determine, for example, whether to make a request again.

[0317] The remote UE may notify the AMF of a request to reset DRX-related information requested of the relay UE. The remote UE may notify the AMF that it does not request the relay UE to configure DRX. The AMF can recognize that the remote UE does not request the relay UE to configure DRX. The AMF may use the notification to determine whether the relay UE should cancel the UE-specific DRX configuration for paging. The AMF may notify the relay UE of the cancellation of the UE-specific DRX configuration for paging. In this way, the relay UE does not need to perform paging reception processing based on the UE-specific DRX configuration for paging. The AMF may notify the remote UE that the relay UE has canceled the UE-specific DRX configuration for paging. In this way, the remote UE can recognize whether the relay UE is performing paging reception processing based on the UE-specific DRX configuration for paging.

[0318] In this way, it is possible to notify the relay UE of the UE-specific DRX configuration for paging according to the DRX-related information requested by the remote UE, and the relay UE can receive paging using the DRX configuration for paging set according to the DRX-related information requested by the remote UE.

[0319] When a relay UE is connected to one or more remote UEs, the above method may be applied to each remote UE. One or more remote UEs each determine DRX-related information requested from the relay UE. Each remote UE notifies the AMF of the DRX-related information requested from the relay UE. The AMF configures one or more paging DRX configurations for the relay UE using the DRX-related information requested from the relay UE received from each remote UE. The AMF may configure paging DRX for the relay UE for each remote UE. The one or more paging DRX configurations may be paging DRX configurations individual to the relay UE. The paging DRX configuration may be for the relay.

[0320] The AMF notifies the relay UE of the derived paging DRX configuration for one or more relay UEs. The relay UE receives paging using the received paging DRX configuration for one or more relay UEs. In this way, even when multiple remote UEs are connected to the relay UE, the relay UE can receive paging at a paging DRX cycle corresponding to the DRX cycle desired by each remote UE.

[0321] The remote UE may notify the relay UE of DRX-related information requested to the relay UE. For example, when multiple remote UEs are connected to the relay UE, the multiple remote UEs may notify the relay UE of DRX-related information requested to the relay UE. The relay UE may derive DRX-related information requested to itself using the DRX-related information requested to the relay UE received from one or more remote UEs.

[0322] For example, the relay UE selects the shortest DRX cycle from the DRX-related information requested of the relay UE received from one or more remote UEs, and sets the selected DRX cycle as the DRX-related information requested of the relay UE.

[0323] The relay UE notifies the AMF of the derived DRX-related information requested for its own UE. The relay UE may notify the AMF of the information via the gNB. The AMF performs paging DRX configuration for the relay UE using the received DRX-related information requested for the relay UE. The paging DRX configuration may be a paging DRX configuration specific to the relay UE. The paging DRX configuration may be for the relay. The AMF notifies the relay UE of the derived paging DRX configuration specific to the relay UE. The AMF may notify the derived configuration via the gNB to which the relay UE is connected. The relay UE receives paging using the received relay UE-specific paging DRX configuration.

[0324] In this way, even when a remote UE generates data for a relay UE connected to one or more remote UEs, it is possible to reduce the amount of delay due to the DRX cycle for paging to the relay UE.

[0325] The above-mentioned methods may be applied as appropriate as a method for a remote UE to notify a relay UE of DRX-related information requested of other UEs, a method for a relay UE to notify an AMF of RRC status information requested of its own relay UE, and a method for an AMF to notify a relay UE of DRX settings for paging.

[0326] 20 to 22 are sequence diagrams showing an example of a method for communicating between a UE and a NW via a relay UE according to the second modification of the first embodiment. FIGS. 20 to 22 are connected at the positions of boundary lines BL2021 and BL2122. FIGS. 20 to 22 disclose an example in which, when there is no data between the remote UE and the NW, the remote UE notifies the gNB connected to the relay UE of DRX-related information requested of the relay UE. According to this example, the relay UE is able to receive paging at the paging DRX cycle desired by the remote UE. In FIGS. 20 to 22, steps common to those in FIGS. 14 to 16 are assigned the same step numbers, and common explanations will be omitted.

[0327] In Step ST1405, the remote UE notifies the AMF of the remote UE-related information, thereby enabling communication between the remote UE and the NW. In Step ST1601, the remote UE notifies the AMF of the DRX-related information it requests the relay UE to send. The remote UE notifies the AMF of the DRX-related information it requests the relay UE to send, via the relay UE and the gNB. The DRX-related information it requests the relay UE to set is configured by the remote UE. For example, the remote UE may derive a data generation cycle from the service-related information and use this information to set the DRX-related information it requests the relay UE to send, such as a DRX cycle for paging. The remote UE may include, in the DRX-related information, information indicating which UE is making the request to which UE. The remote UE may notify the DRX-related information together with the remote UE-related information it notifies the AMF in Step ST1405, or by including the DRX-related information in the remote UE-related information in Step ST1405. This allows for early processing by the gNB.

[0328] The AMF that has received the DRX-related information can recognize the paging DRX configuration for the relay UE. Furthermore, since the request is from the remote UE, the AMF can recognize that it is a request for communication for relay. In Step ST1602, the AMF derives the paging DRX configuration for the relay UE using the paging DRX-related information requested of the relay UE. The paging DRX configuration may be a UE-specific DRX configuration. The paging DRX configuration can be performed individually for each relay UE.

[0329] In Step ST1603, the AMF notifies the relay UE via the gNB of the paging DRX configuration for the relay UE. When the relay UE transitions to RRC_Idle or CM_Idle, the relay UE receives paging using this paging DRX configuration. The relay UE may receive paging using both the paging DRX configuration broadcast by the cell and the paging DRX configuration received from the AMF. Alternatively, the relay UE may receive paging using the DRX configuration having a shorter DRX cycle.

[0330] Data generation between the remote UE and the NW ceases, and in Step ST1415, an RRC connection release procedure is performed between the relay UE and the gNB, and a CM connection release procedure is performed between the relay UE, the gNB, and the AMF. As a result, the relay UE transitions to an RRC_Idle or CM_Idle state. In Step ST1604, the relay UE receives paging with the DRX configuration received from the AMF.

[0331] In Step ST1417, data is generated in the remote UE, and in Step ST1421, the AMF receives a data generation notification from the SMF. In Step ST1605, the AMF that has received the data generation notification may suspend notification of paging to the relay UE via the gNB until the DRX timing for paging set for the relay UE. In this way, it is possible to notify paging at an appropriate timing.

[0332] By using the method disclosed herein, in communication between a remote UE and a network via a relay UE, it is possible to configure the relay UE for DRX for paging according to the generation cycle of data that the remote UE communicates with the network. The relay UE can receive data at a DRX cycle for paging that is suited to the generation cycle of data that the remote UE communicates with the network, thereby enabling low power consumption of the relay UE.

[0333] Embodiment 2 Another method for solving the problem described in the first embodiment will be disclosed.

[0334] A relay UE capable of UE-to-NW relay is allowed to transition to RRC_Inactive. The RRC connection between the relay UE and the gNB may be suspended. A relay UE capable of UE-to-NW relay remains in CM_Connected state. In RRC_Inactive state, RRC is suspended and CM is connected. The PDU session between the relay UE and the NW may be released. The above process may be performed even if a PC5-S link is established between the remote UE and the relay UE.

[0335] The transition process to RRC_Inactive is disclosed. RRC stop process is performed between the gNB and the relay UE. The gNB may initiate the RRC stop process for the relay UE. For example, the gNB may notify the relay UE of an RRC release message with suspend information. This causes the RRC stop process to be performed between the gNB and the relay UE. The relay UE may request the gNB to stop RRC. Upon receiving the RRC stop request, the gNB performs the RRC stop process with the relay UE. Also, when the AMF performs a PDU session release process for the gNB, the gNB may perform the RRC stop process with the relay UE. The CM connection between the relay UE and the NW is maintained. The AMF may maintain the CM connection between the relay UE and the NW. The relay UE may maintain the CM_Connected state. By maintaining the CM connection, a CM state transition is not required when the relay UE communicates with the NW again, enabling communication with low latency.

[0336] For the release process of the PDU session by the relay UE and NW nodes, the method disclosed in embodiment 1 may be applied as appropriate.

[0337] The PC5-S link between the relay UE and the remote UE may be connected while the transition process to RRC_Inactive is performed. Alternatively, the release process may be performed without releasing the PC5-S link between the relay UE and the remote UE.

[0338] For example, when communication between the remote UE and the NW is temporarily lost, the above-mentioned transition process to RRC_Inactive may be performed. Also, when communication between the remote UE and the NW is performed periodically, the above-mentioned transition process to RRC_Inactive may be performed during the period when the communication is not performed. By performing the above-mentioned transition process to RRC_Inactive and transitioning the relay UE to the RRC_Inactive state, it is possible to reduce the power consumption of the relay UE.

[0339] As a method for transitioning to RRC_Inactive in a relay UE or a network node, the method disclosed in the first embodiment may be applied as appropriate. For example, as a method for determining transition to RRC_Inactive, the method disclosed in the first embodiment for determining whether to perform or request release processing in a relay UE or a network node may be applied as appropriate.

[0340] A request for transition to RRC_Inactive between the relay UE and the gNB may be made by the remote UE. Alternatively, the remote UE may request the relay UE or the gNB to transition to RRC_Inactive.

[0341] Since the remote UE recognizes the service for communication with the NW, the remote UE can easily determine when communication between the remote UE and the NW is temporarily suspended. By requesting the transition to the RRC_Inactive state between the relay UE and the NW, the remote UE can perform a transition process of the relay UE to the RRC_Inactive state suitable for the communication service between the remote UE and the NW. In this way, for example, when there is no data communication on the PC5-S link for a predetermined period of time, the remote UE can transition the relay UE to the RRC_Inactive state, thereby reducing the power consumption of the relay UE.

[0342] When a gNB receives data from the UPF via the relay UE or signaling from the AMF to the relay UE while the relay UE is in the RRC_Inactive state, the gNB notifies the relay UE associated with the remote UE of paging. This paging is called RAN paging. RAN paging is performed by one or more gNBs in a predetermined area to UEs served by them. This predetermined area is called RNA (RAN Notification Area).

[0343] A gNB notifies surrounding gNBs of RAN paging. Xn signaling may be used for this notification. A gNB included in an RNA transmits the received RAN paging to a UE being served by the gNB. In this way, a gNB in ​​an RNA can transmit RAN paging to a UE being served by the gNB.

[0344] The RAN paging transmitted from a gNB to a UE served by the gNB and / or the RAN paging notified from a gNB to neighboring gNBs may include information indicating that the paging is due to the occurrence of data or signaling for a remote UE. Alternatively, the paging for a relay UE may include information about the remote UE, such as a UE identifier. In this way, the relay UE receiving the RAN paging can recognize that the paging is due to the occurrence of data for the remote UE.

[0345] Upon receiving the RAN paging, the relay UE transitions to RRC_Connected with the NW. Upon receiving the RAN paging, the relay UE may notify the gNB of an RRC Resume Request. The gNB requests the previous serving gNB of the relay UE to notify it of the RAN UE context. The previous serving gNB of the relay UE notifies the gNB of the RAN UE context. The previous serving gNB of the relay UE may include association information between the relay UE and the remote UE in the RAN UE context. The previous serving gNB of the relay UE may include the association information in the RAN UE context of the relay UE.

[0346] A RAN UE context for the remote UE may be established. The association information may be included in the RAN UE context for the remote UE. The gNB may store the RAN UE context information for the remote UE. The gNB may store the association information separately from the RAN UE context information. A previous serving gNB of the relay UE may notify the gNB of the RAN UE context for the remote UE together with the RAN UE context for the relay UE. Alternatively, the previous serving gNB of the relay UE may notify the gNB of the association information together with the RAN UE context for the relay UE.

[0347] A gNB that receives an RRC Resume Request from the relay UE may request the previous serving gNB of the relay UE to notify the RAN UE context of the remote UE. The previous serving gNB of the relay UE notifies the requesting gNB of the RAN UE context of the remote UE.

[0348] A gNB that receives an RRC Resume Request from a relay UE may request the previous serving gNB of the relay UE to notify the association information between the remote UE where data or signaling occurred and the relay UE. The previous serving gNB of the relay UE notifies the requesting gNB of the association information between the remote UE and the relay UE.

[0349] In this way, the gNB to which the relay UE is newly connected can recognize the association between the remote UE and the relay UE, and the gNB can reduce malfunctions when notifying the remote UE of data or signaling via the relay UE.

[0350] The gNB, which receives association information between the remote UE and the relay UE from the relay UE's previous serving gNB, notifies the relay UE of RRC reconnection. The relay UE transitions to the RRC_Connected state. The relay UE notifies the gNB of the completion of transition to the RRC_Connected state. Path switching processing is performed in the gNB, AMF, SMF, and UPF. In this way, when data for the remote UE is generated, the relay UE can transition to the RRC_Connected state.

[0351] A relay UE that receives a RAN paging may establish a PDU session with the gNB to which it was connected before transitioning to RRC_Inactive. When a relay UE that receives a paging receives information indicating that the paging is due to data generated for the remote UE, it establishes a PDU session with the NW. The PDU session may be for relaying. The PDU session may be for communication with the remote UE that generated the data. In this way, a PDU session for communication between the remote UE and the NW can be established between the relay UE and the NW. Even after the relay UE transitions to the RRC_Inactive state, if data for the remote UE is generated, a PDU session can be established again between the relay UE and the NW. This enables communication between the remote UE and the NW using the PDU session.

[0352] In this way, the relay UE can perform DRX in the paging DRX cycle of the RAN paging, thereby enabling reduction in power consumption of the relay UE.

[0353] As a process when service data is received from a remote UE while the relay UE is in the RRC_Inactive state, the process disclosed in the first embodiment when service data is received from a remote UE while the relay UE is in the RRC_Idle or CM_Idle state may be applied as appropriate. For example, a transition process from RRC_Inactive to RRC_Connected and a PDU session establishment process may be performed. In this way, data can be communicated from the remote UE to the NW.

[0354] The method disclosed in Variant 1 of Embodiment 1 may also be applied. Variant 1 of Embodiment 1 discloses a method in which a remote UE determines an RRC state desired for a relay UE and notifies the determined RRC state information to a gNB connected to the relay UE. RRC_Inactive may be set as the RRC state desired for the relay UE. The gNB connected to the relay UE may transition the RRC state of the relay UE using the received RRC state information desired for the relay UE. For example, if the relay UE is in an RRC connected state, an RRC stop procedure may be performed to transition the relay UE to an RRC_Inactive state.

[0355] In this way, in communication between the remote UE and the NW via the relay UE, the relay UE can transition to the RRC_Inactive state depending on whether or not there is data for the remote UE to communicate with the NW. Since the relay UE can receive data in the DRX cycle for RAN paging, it is possible to reduce the power consumption of the relay UE.

[0356] A UE-specific DRX may be configured as the RAN paging DRX. Specific examples of the RAN paging DRX configuration include a paging DRX cycle, a paging frame, a paging slot, etc., and these may be combined. The gNB may configure the relay UE with a UE-specific DRX for RAN paging. The gNB may notify the relay UE of the UE-specific DRX configuration for RAN paging when the relay UE is in an RRC_Connected state. For example, the gNB may notify the relay UE of the DRX configuration by including it in RRC stop signaling.

[0357] The AMF may configure a UE-specific DRX for RAN paging for the relay UE. The AMF may notify the relay UE of the configuration of the UE-specific DRX for RAN paging when the relay UE is in an RRC_Connected state. For example, the AMF may notify the DRX configuration by NAS signaling. Alternatively, the AMF may use N2 signaling for notification to the gNB and RRC signaling for notification to the relay UE.

[0358] The gNB may notify neighboring gNBs of DRX-related information for RAN paging. The gNB may notify the information by including it in the RAN paging information or may notify it together with the RAN paging information. In this way, the gNB in ​​the RNA can send paging to the relay UE with the same DRX configuration for RAN paging.

[0359] In this way, by configuring the relay UE with individual DRX settings for RAN paging, it is possible to configure the relay UE with DRX settings suitable for the data communication interval between the remote UE and the network, thereby reducing unnecessary power consumption in the relay UE, and reducing delays in data communication between the remote UE and the network via the relay UE.

[0360] The method disclosed in the second modification of the first embodiment may be applied. The method disclosed in the second modification of the first embodiment may be appropriately applied to a method in which the AMF configures a UE-specific DRX for RAN paging for the relay UE. Similar effects can be obtained.

[0361] In the second modification of the first embodiment, a method in which the AMF configures DRX for paging for each UE has been disclosed, but the RAN node, for example, the gNB, may configure DRX instead of the AMF. The gNB connected to the relay UE may also configure DRX. Since the gNB configures DRX for RAN paging, the method disclosed in the second modification of the first embodiment is processed by the gNB, not the AMF. This makes it possible to avoid the processing from becoming complicated. Furthermore, it is possible to reduce the amount of signaling between the gNB and the AMF.

[0362] By using the method disclosed herein, it is possible to transition a relay UE to an RRC_Inactive state in communication between a remote UE and a network via the relay UE. Since the relay UE can receive paging at the RAN paging DRX cycle, power consumption can be reduced. Furthermore, it is possible to individually configure the RAN paging DRX for the relay UE according to the generation cycle of data that the remote UE communicates with the network. Since the relay UE can receive data at the RAN paging DRX cycle that is appropriate for the generation cycle of data that the remote UE communicates with the network, power consumption of the relay UE can be reduced. Furthermore, it is possible to reduce delays in data communication between the remote UE and the network via the relay UE.

[0363] Embodiment 3 Another method for solving the problem described in the first embodiment will be disclosed.

[0364] A relay UE capable of UE-to-NW relay may maintain the RRC_Connected state while performing the relaying procedure. The RRC connection may not be released. A relay UE capable of UE-to-NW relay may maintain the CM_Connected state while performing the relaying procedure. The CM connection may not be released. A relay UE capable of UE-to-NW relay may maintain the PDU session between the relay UE and the NW while performing the relaying procedure. The PDU session may not be released.

[0365] The above-mentioned process may be performed even when a PC5-S link is established between the remote UE and the relay UE. The period during which the relay process is performed may be the period from when a PDU session for relaying is established between the relay UE and the NW to when the PDU session for relaying is released.

[0366] The gNB configures DRX for the relay UE. The relay UE configures DRX in the RRC connected state. DRX in the RRC connected state is sometimes referred to as C-DRX. By doing so, the relay UE can perform DRX processing when data communication is performed between the remote UE and the NW via the relay UE. This makes it possible to reduce the power consumption of the relay UE.

[0367] The gNB configures C-DRX for the relay UE. The gNB can configure C-DRX for each UE. Therefore, the gNB can configure C-DRX for each relay UE individually. However, in communication between a remote UE and a network via a relay UE, it is the remote UE that generates communication data, and the relay UE does not generate communication data. For this reason, the gNB connected to the relay UE cannot configure C-DRX for the relay UE that is suitable for the service occurring between the remote UE and the network. A method for solving this problem is disclosed.

[0368] The UE sets C-DRX-related information of other UEs that it requests. In this disclosure, this information is referred to as C-DRX-related information requested from other UEs. The UE determines the C-DRX-related information to request from other UEs. Specific examples of the requested C-DRX-related information include a DRX cycle, an on-interval, an inactivity timer, a retransmission timer, an HARQ inactivity timer, and the like, and these may be combined.

[0369] The UE notifies the gNB of C-DRX related information it requests other UEs to use. The gNB uses the received requested C-DRX related information to derive C-DRX configuration for the other UEs. The C-DRX configuration may be a UE-specific C-DRX configuration. Specific examples of the C-DRX configuration include a DRX cycle, an on-interval, an inactivity timer, a retransmission timer, an HARQ inactivity timer, and the like, and these may be combined.

[0370] The requested C-DRX-related information may include information for identifying which UE the request is for. The requested C-DRX-related information may be notified together with the information for identifying which UE the request is for. In this way, a node that receives the requested C-DRX-related information can recognize which UE the C-DRX-related information is for.

[0371] The requested C-DRX-related information may include information for identifying which UE has requested it. Information for identifying which UE has requested it may be notified together with the requested C-DRX-related information. In this way, a node that receives the requested C-DRX-related information can recognize which UE has requested the C-DRX-related information.

[0372] The gNB notifies the other UE of the derived other-UE-specific C-DRX configuration. The gNB may notify the other UE of the derived configuration via a gNB to which the other UE is connected. The other UE performs DRX processing using the received other-UE-specific C-DRX configuration. The other UE performs reception operation during the DRX active period. For example, the other UE receives a PDCCH during the DRX active period. The other UE does not receive a PDCCH outside the DRX active period. In this manner, it is possible to notify a UE other than the UE that requested the C-DRX-related information of a UE-specific C-DRX configuration corresponding to the requested C-DRX-related information. The UE can perform DRX processing using the C-DRX configuration set according to the C-DRX-related information requested by the other UE.

[0373] For example, in communication between a remote UE and a network via a relay UE, the remote UE determines DRX-related information requested from the relay UE. The remote UE notifies the gNB of the C-DRX-related information requested from the relay UE via the relay UE. The gNB performs C-DRX configuration for the relay UE using the received C-DRX-related information requested from the relay UE. The C-DRX configuration may be individual to the relay UE. The C-DRX configuration may also be for the relay.

[0374] As a method for notifying the relay UE of C-DRX related information requested from the remote UE, the method for notifying the relay UE of requested RRC status information, disclosed in the first modification of the first embodiment, may be applied as appropriate. It is preferable to use C-DRX information instead of the RRC status information, and the same effect can be obtained.

[0375] As a method for notifying the gNB of C-DRX related information requested from the relay UE, the method for notifying the gNB of requested RRC state information from the relay UE disclosed in Variant 1 of Embodiment 1 may be applied as appropriate. It is preferable to use C-DRX information instead of the RRC state information, and similar effects can be obtained.

[0376] In this way, the remote UE can notify the gNB to which the relay UE is connected of the C-DRX related information it has decided to request from the relay UE. The gNB can recognize the requested C-DRX configuration, which UE has made the request, and which UE the request is for from the received requested C-DRX related information. The gNB configures the C-DRX of the relay UE using the received requested C-DRX related information.

[0377] For example, the remote UE derives a data communication interval between the remote UE and the NW from a service communicating with the NW. The remote UE may determine whether the service is performed periodically, and if so, derive the period. The remote UE may use the derived data communication interval and period to determine C-DRX-related information to request from the relay UE. The remote UE may configure the C-DRX-related information to request from the relay UE so that the C-DRX configuration is appropriate for the derived data communication interval and period.

[0378] As another method, the remote UE may measure time information related to data in the PC5-S link. The remote UE may derive a data communication interval and a traffic pattern from the measurement results. As these methods, the methods disclosed in the first embodiment may be applied as appropriate. The remote UE may configure C-DRX related information requested of the relay UE using the derived data communication interval and traffic pattern. The remote UE may configure C-DRX related information requested of the relay UE so that the C-DRX configuration is suitable for the derived data communication interval and traffic pattern.

[0379] In this way, the remote UE can derive a C-DRX setting that it requests from the relay UE, which is suitable for the service of communication with the NW.

[0380] The gNB derives a C-DRX configuration for the relay UE using the received C-DRX-related information requested of the relay UE. The C-DRX configuration may be a UE-specific configuration. The gNB notifies the relay UE of the derived relay UE-specific C-DRX configuration. The relay UE can perform DRX processing using the received relay UE-specific C-DRX configuration.

[0381] The gNB may configure a C-DRX setting that differs from the C-DRX-related information requested from the relay UE. The gNB may not configure a C-DRX setting. The gNB may notify the remote UE of the C-DRX setting configured for the relay UE. The remote UE can recognize the C-DRX setting configured for the relay UE. The gNB may include reason information in the notification. If the gNB configures a C-DRX setting that differs from the C-DRX-related information requested by the remote UE, the remote UE can recognize the reason. This allows the remote UE to determine, for example, whether to make a request again.

[0382] The remote UE may notify the gNB of a request to reset C-DRX-related information requested of the relay UE. The remote UE may notify the gNB that it does not request the relay UE to configure C-DRX. The gNB can recognize that the remote UE does not request the relay UE to configure C-DRX. The gNB may use this notification to determine whether the relay UE should cancel the C-DRX configuration. The gNB may notify the relay UE of the cancellation of the C-DRX configuration. In this way, the relay UE does not need to perform DRX processing with the C-DRX configuration. The gNB may notify the remote UE that the C-DRX configuration of the relay UE has been canceled. In this way, the remote UE can recognize whether the relay UE is performing DRX processing with the C-DRX configuration.

[0383] When a relay UE is connected to one or more remote UEs, the above method may be applied to each remote UE. The one or more remote UEs each determine C-DRX-related information requested from the relay UE. Each remote UE notifies the gNB of the C-DRX-related information requested from the relay UE. The gNB configures one or more C-DRX configurations for the relay UE using the C-DRX-related information requested from the relay UE received from each remote UE. The gNB may configure the C-DRX configuration for the relay UE for each remote UE. The one or more C-DRX configurations may be individual C-DRX configurations for the relay UE. The C-DRX configurations may be for the relay.

[0384] The gNB notifies the relay UE of the derived C-DRX configuration for one or more relay UEs. The relay UE performs DRX processing using the received C-DRX configuration for one or more relay UEs. In this way, even when multiple remote UEs are connected to the relay UE, the relay UE can perform DRX processing at a C-DRX cycle corresponding to the DRX cycle desired by each remote UE.

[0385] The remote UE may notify the relay UE of C-DRX related information requested to the relay UE. For example, when multiple remote UEs are connected to the relay UE, the multiple remote UEs may notify the relay UE of C-DRX related information requested to the relay UE. The relay UE may derive the C-DRX related information requested to itself using the C-DRX related information requested to the relay UE received from one or more remote UEs.

[0386] For example, the relay UE selects the shortest DRX period from the C-DRX related information requested of the relay UE received from one or more remote UEs, and sets the selected DRX period as the C-DRX related information requested of the relay UE.

[0387] The relay UE notifies the gNB of the derived C-DRX related information desired for its own UE. The gNB performs C-DRX configuration for the relay UE using the received C-DRX related information desired for the relay UE. The C-DRX configuration may be a configuration individual to the relay UE. The C-DRX configuration may be for the relay. The gNB notifies the relay UE of the derived C-DRX configuration individual to the relay UE. The relay UE performs DRX processing using the received C-DRX configuration individual to the relay UE.

[0388] In this way, even when a remote UE generates data for a relay UE connected to one or more remote UEs, it is possible to reduce the amount of delay due to the C-DRX cycle for the relay UE.

[0389] The above-mentioned methods may be applied as appropriate as a method for a remote UE to notify a relay UE of C-DRX-related information requested of other UEs, a method for a relay UE to notify a gNB of C-DRX-related information requested of its own relay UE, and a method for a gNB to notify a relay UE of C-DRX settings.

[0390] 23 and 24 are sequence diagrams showing an example of a method for communicating between a UE and a NW via a relay UE according to the third embodiment. Figures 23 and 24 are connected at the boundary line BL2324. Figures 23 and 24 disclose an example in which a remote UE notifies a gNB connected to the relay UE of C-DRX-related information requested of the relay UE. According to this example, the relay UE can perform DRX processing at a C-DRX cycle desired by the remote UE. In Figures 23 and 24, steps common to Figures 14 to 16 are assigned the same step numbers, and common descriptions will be omitted. Figures 23 and 24 show a state in which the relay UE maintains an RRC connection and a CM connection.

[0391] In Step ST1405, the remote UE notifies the AMF of the remote UE-related information, thereby enabling communication between the remote UE and the NW. In Step ST1701, the remote UE notifies the gNB of the C-DRX-related information it requests the relay UE to communicate with. The remote UE notifies the gNB of the C-DRX-related information it requests the relay UE to communicate with via the relay UE. The C-DRX-related information it requests the relay UE to communicate with is configured by the remote UE. For example, the remote UE may derive a data generation cycle from service-related information and use this information to configure the C-DRX-related information it requests the relay UE to communicate with, such as a DRX cycle or a DRX-on period. The remote UE may include, in the C-DRX-related information, information indicating which UE is making the request to which UE. The remote UE may notify the C-DRX-related information together with the remote UE-related information it notifies the AMF in Step ST1405, or by including the C-DRX-related information in the remote UE-related information in Step ST1405. This will enable early processing with gNB.

[0392] The gNB that has received the DRX-related information can recognize the C-DRX configuration for the relay UE. Furthermore, since the request is from the remote UE, the gNB can recognize that it is a request for communication for relaying. In Step ST1702, the gNB derives the C-DRX configuration for the relay UE using the paging DRX-related information requested of the relay UE. The C-DRX configuration may be a DRX configuration for each UE. The C-DRX configuration can be performed individually for each relay UE.

[0393] In Step ST1703, the gNB notifies the relay UE of the C-DRX configuration for the relay UE. In Step ST1704, the relay UE implements the received C-DRX configuration. The relay UE performs transmission and reception with the gNB using this C-DRX configuration.

[0394] The relay UE may support mobility, for example, the relay UE may support a cell reselection procedure, and the relay UE may support an HO procedure.

[0395] This section discloses a case where a relay UE performs HO. The relay UE may perform HO processing between a source gNB and a target gNB. The source gNB notifies the target gNB of information related to the relay UE that performs HO and information related to the remote UE connected to the relay UE. The source gNB may notify the target gNB of this information by including it in HO request signaling that it notifies. The target gNB, having received the information related to the relay UE and the remote UE, may create association information. The target gNB establishes a PDU session between the relay UE and the NW. In this way, even in a situation where the relay UE performs HO, when data to the remote UE is generated, the data can be transmitted from the NW to the remote UE via the target gNB and the relay UE.

[0396] In a situation where a relay UE performs HO, the connection with the remote UE may not be maintained. In such a case, the relay UE may notify the source gNB or the target gNB of information indicating that the connection with the remote UE is not maintained. Alternatively, the relay UE may notify the source gNB or the target gNB of the release or discard of information related to the remote UE. In addition, the target gNB may not establish a PDU session between the relay UE and the NW to be used for relay communication with the remote UE.

[0397] The source gNB or the target gNB may notify the AMF of information indicating that the connection with the remote UE is not maintained. Alternatively, the source gNB or the target gNB may notify the AMF of the release or discard of information related to the remote UE. In addition, the AMF may not establish a PDU session between the relay UE and the NW for relay communication with the remote UE.

[0398] By doing so, in a situation where the relay UE performs HO, if the connection between the relay UE and the remote UE is not maintained, it is possible to prevent the establishment of a PDU session, the retention of association information with the remote UE in the gNB and / or AMF, etc. It is possible to avoid unnecessary processing, and as a system, it is possible to reduce malfunctions and power consumption.

[0399] By using the method disclosed herein, in communication between a remote UE and a network via a relay UE, the relay UE can perform DRX processing at a C-DRX cycle without transitioning the relay UE to an RRC_Idle or RRC_Inactive state. This reduces the power consumption of the relay UE. Furthermore, it is possible to individually configure the C-DRX settings for the relay UE depending on the intervals at which data is generated and the traffic pattern of the data that the remote UE communicates with the network. Since the relay UE can perform DRX processing with a C-DRX setting appropriate for the intervals at which data is generated and the traffic pattern of the data that the remote UE communicates with the network, it is possible to reduce the power consumption of the relay UE. Furthermore, it is possible to reduce delays in data communication between the remote UE and the network via the relay UE.

[0400] It has been disclosed that the gNB configures DRX for the relay UE. As another example, the gNB may configure SPS for the relay UE. As another example, the gNB may configure CG for the relay UE. A relay UE configured with SPS or CG may activate transmission and reception processing using resources configured by the SPS or resources configured by the CG. In this way, it is possible to reduce the power consumption of the relay UE when data communication is performed between a remote UE and a network via the relay UE.

[0401] Variation 1 of embodiment 3 Another method for solving the problem described in the first embodiment will be disclosed.

[0402] In the third embodiment, a method is disclosed in which a remote UE notifies a gNB of C-DRX related information that the remote UE requests a relay UE to have, and the gNB uses the information to configure C-DRX for the relay UE. In this first modification of the third embodiment, a method is disclosed in which a traffic pattern is used instead of the C-DRX related information.

[0403] The remote UE derives a traffic pattern in communication with the NW. The method of deriving the traffic pattern may be the method disclosed in the third embodiment, as appropriate. For example, the remote UE derives a traffic pattern between the remote UE and the NW from a service communicating with the NW. For example, the remote UE may measure time information related to data in a PC5-S link and derive a traffic pattern from the measurement results.

[0404] In communication between the remote UE and the NW via the relay UE, the remote UE derives a traffic pattern and notifies the gNB of the traffic pattern via the relay UE.

[0405] Information indicating which UE the traffic pattern is for may be provided. For example, a UE identifier may be used as this information. Information indicating which service the traffic pattern is for may be provided. For example, a service identifier may be used as this information. Information indicating which QoS flow the traffic pattern is for may be provided. A PC5 QoS flow may be used as the QoS flow. For example, a QoS flow identifier may be used. The remote UE may notify the gNB of some or all of this information together with the traffic pattern via the relay UE. In this way, the gNB can recognize which UE the traffic pattern is for, which service the traffic pattern is for, and which QoS flow the traffic pattern is for.

[0406] The gNB uses the traffic pattern to configure C-DRX for the relay UE, which may be a dedicated C-DRX configuration for the relay UE, or may be a C-DRX configuration for the relay UE.

[0407] The method of notifying the traffic pattern from the remote UE to the relay UE may be the same as the method disclosed in the first modification of the first embodiment, in which the remote UE notifies the relay UE of desired RRC status information. It is preferable to use the traffic pattern instead of the RRC status information, and the same effect can be obtained.

[0408] The method of notifying the traffic pattern from the relay UE to the gNB may be appropriately applied to the method of notifying the desired RRC state information from the relay UE to the gNB disclosed in Variant 1 of Embodiment 1. It is preferable to use the traffic pattern instead of the RRC state information, and the same effect can be obtained.

[0409] In this way, the traffic pattern derived by the remote UE can be notified to the gNB to which the relay UE is connected.

[0410] The gNB derives a C-DRX configuration for the relay UE using the traffic pattern received from the remote UE. The C-DRX configuration may be a UE-specific configuration. The gNB notifies the relay UE of the derived relay UE-specific C-DRX configuration. The relay UE can perform DRX processing using the received relay UE-specific C-DRX configuration.

[0411] The gNB may notify the remote UE of the C-DRX configuration set in the relay UE. The remote UE can recognize the C-DRX configuration set in the relay UE. The gNB may include reason information in the notification. For example, the remote UE can determine whether to change the traffic pattern notification cycle or whether to notify the traffic pattern.

[0412] When a relay UE is connected to one or more remote UEs, the above method may be applied to each remote UE. The one or more remote UEs each determine a traffic pattern. Each remote UE notifies the gNB of its traffic pattern. The gNB configures one or more C-DRX configurations for the relay UE using the traffic patterns received from each remote UE. The gNB may configure the C-DRX configuration for the relay UE for each remote UE. The one or more C-DRX configurations may be individual C-DRX configurations for the relay UE. The C-DRX configuration may be for the relay.

[0413] The gNB notifies the relay UE of the derived C-DRX configuration for one or more relay UEs. The relay UE performs DRX processing using the received C-DRX configuration for one or more relay UEs. In this way, even when multiple remote UEs are connected to the relay UE, the relay UE can perform DRX processing at a C-DRX cycle according to the traffic pattern of each remote UE.

[0414] Although the above description discloses that the remote UE derives the traffic pattern, the relay UE may derive the traffic pattern of the communication between the remote UE and the NW. For example, the relay UE measures communication data of the PC5 link between the remote UE and the relay UE. The method disclosed in the first embodiment may be applied as appropriate.

[0415] The relay UE notifies the gNB of the derived traffic pattern of communication between the remote UE and the NW. There may be one or more remote UEs. The relay UE notifies the gNB of the traffic pattern of communication between the remote UE and the NW derived for each remote UE. The gNB configures one or more C-DRX configurations for the relay UE using the traffic pattern of communication between the remote UE and the NW received from the relay UE. The one or more C-DRX configurations may be individual C-DRX configurations for the relay UE. The C-DRX configuration may be for the relay.

[0416] The gNB notifies the relay UE of the derived C-DRX configuration for one or more relay UEs. The relay UE performs DRX processing using the received C-DRX configuration for one or more relay UEs. In this way, even when multiple remote UEs are connected to the relay UE, the relay UE can perform DRX processing at a C-DRX cycle that corresponds to the traffic pattern of communication between each remote UE and the NW.

[0417] This method may be combined with the method disclosed in the third embodiment. For example, the remote UE may notify the relay UE of a traffic pattern. For example, if multiple remote UEs are connected to the relay UE, the multiple remote UEs may notify the relay UE of their traffic patterns. The relay UE derives C-DRX-related information required for itself using the traffic patterns received from one or more remote UEs.

[0418] The relay UE notifies the gNB of the derived C-DRX related information desired for its own relay UE. The gNB performs C-DRX configuration for the relay UE using the received C-DRX related information desired for the relay UE. The C-DRX configuration may be a configuration individual to the relay UE. The C-DRX configuration may be for the relay. The gNB notifies the relay UE of the derived C-DRX configuration individual to the relay UE. The relay UE performs DRX processing using the received C-DRX configuration individual to the relay UE.

[0419] In this way, even when a remote UE generates data for a relay UE connected to one or more remote UEs, it is possible to reduce the amount of delay due to the C-DRX cycle for the relay UE.

[0420] 25 and 26 are sequence diagrams showing an example of a method for communicating between a UE and a NW via a relay UE according to a first modification of the third embodiment. FIGS. 25 and 26 are connected at the boundary line BL2526. FIGS. 25 and 26 disclose an example in which a remote UE notifies a gNB connected to the relay UE of a traffic pattern. According to this example, the relay UE can perform DRX processing at a C-DRX cycle according to the traffic pattern. In FIGS. 25 and 26, steps common to those in FIGS. 23 and 24 are assigned the same step numbers, and common descriptions will be omitted.

[0421] In Step ST1405, the remote UE notifies the AMF of the remote UE-related information, thereby enabling communication between the remote UE and the NW. In Step ST1801, the remote UE notifies the gNB of a traffic pattern. The remote UE notifies the gNB of the traffic pattern via the relay UE. The remote UE may derive the traffic pattern, for example, from service-related information communicated between the remote UE and the NW. The traffic pattern may be notified together with the remote UE-related information notified from the remote UE to the AMF in Step ST1405, or may be included in the remote UE-related information in Step ST1405. This allows for early processing by the gNB.

[0422] In Step ST1802, the gNB that has received the traffic pattern from the remote UE derives a C-DRX configuration for the relay UE using the traffic pattern. The C-DRX configuration may be a UE-specific DRX configuration. The C-DRX configuration can be performed individually for each relay UE.

[0423] In Step ST1803, the gNB notifies the relay UE of the C-DRX configuration for the relay UE. In Step ST1804, the relay UE implements the received C-DRX configuration. The relay UE performs transmission and reception with the gNB using this C-DRX configuration.

[0424] By using the method disclosed herein, in communication between a remote UE and a network via a relay UE, the relay UE can perform DRX processing in a C-DRX cycle without transitioning the relay UE to an RRC_Idle or RRC_Inactive state. This reduces the power consumption of the relay UE. Furthermore, it is possible to individually configure the C-DRX settings for the relay UE according to the traffic pattern of data that the remote UE communicates with the network. Since the relay UE can perform DRX processing with a C-DRX setting appropriate for the traffic pattern of data that the remote UE communicates with the network, it is possible to reduce the power consumption of the relay UE. Furthermore, it is possible to reduce delays in data communication between the remote UE and the network via the relay UE.

[0425] This disclosure discloses a method for notifying information relating to communication between a remote UE and a network via a relay UE, among the remote UE, the relay UE, and a gNB connected to the relay UE. Fig. 27 is a sequence diagram showing an example of a method for notifying information relating to communication between a remote UE and a network via a relay UE, among the remote UE, the relay UE, and a gNB connected to the relay UE.

[0426] The gNB notifies the relay UE of a setting for reporting information about communication between the remote UE and the NW via the relay UE. RRC signaling may be used for the notification. For example, an Other Config message may be used. The relay UE, upon receiving the setting for reporting information, may notify the remote UE of the setting for reporting information. The relay UE may notify information indicating which information is about communication between the remote UE and the NW via the relay UE. Examples of the information include the above-mentioned RRC status information requested from other UEs, C-DRX-related information requested from other UEs, traffic patterns, etc.

[0427] PC5-S signaling may be used to notify the remote UE of the information report settings. Even if PC5 RRC settings are not configured, early notification is possible. Alternatively, PC5 RRC signaling may be used. This has a high affinity with the RRC processing from the gNB to the relay UE, and it is possible to avoid complication of the processing. For example, a message for setting the UE assistance information report may be provided. Alternatively, PC5 MAC signaling may be used. This allows early notification with low error. Alternatively, PSCCH or PSSCH may be used. This allows even earlier notification.

[0428] The remote UE that has received the information reporting configuration derives the information based on the information reporting configuration. For example, if RRC status information requested for other UEs is configured, the remote UE derives the RRC status information requested for other UEs. The remote UE notifies the relay UE of the derived information reporting. As a notification method, the above-mentioned method of notifying the remote UE of the information reporting configuration may be appropriately applied. As RRC signaling, for example, a UE assistance information message may be provided.

[0429] The relay UE that receives the information report notifies the gNB of the information report. As a notification method, the above-mentioned method of notifying the relay UE of the setting of the information report from the gNB may be applied as appropriate. As RRC signaling, for example, a UE assistance information message may be used. In this way, the gNB can obtain information about communication between the remote UE and the NW via the relay UE from the remote UE.

[0430] The gNB can acquire the above-mentioned information, such as RRC status information requested of the relay UE, C-DRX-related information requested of the relay UE, traffic pattern information, etc. This allows the gNB to use this information to control the connection status and DRX settings of the relay UE.

[0431] Embodiment 4 Another method for solving the problem described in the first embodiment will be disclosed.

[0432] DRX processing is performed in direct communication between UEs in PC5. A DRX setting method for direct communication between UEs in PC5 is disclosed. In this disclosure, DRX in direct communication between UEs in PC5 may be referred to as PC5 DRX. Also, in direct communication between UEs in PC5, the transmitting UE may be referred to as UE-TX, and the receiving UE may be referred to as UE-RX. In direct communication between UEs in PC5, there are two methods: one in which UE-TX selects and reserves resources for SL communication (called mode 2), and one in which a gNB to which UE-TX is connected schedules resources for SL communication (called mode 1).

[0433] This section describes the PC5 DRX setting in mode 2. UE-TX sets PC5 DRX. UE-TX notifies UE-RX, the opposing UE in direct communication between UEs in PC5, of the PC5 DRX setting. UE-RX performs DRX processing in direct communication between UEs in PC5 using the PC5 DRX setting received from UE-TX.

[0434] UE-TX may notify UE-RX of the PC5 DRX configuration using PC5-S signaling. This allows for early notification. Alternatively, UE-TX may notify UE-RX of the PC5 DRX configuration using PC5 RRC signaling. UE-TX may notify UE-RX of the PC5 DRX configuration as an AS configuration. Alternatively, UE-TX may notify UE-RX of the PC5 DRX configuration using PC5 MAC signaling. Alternatively, UE-TX may notify UE-RX of the PC5 DRX configuration using PSCCH or PSSCH. This allows for dynamic and early notification after PC5 DRX is configured.

[0435] The activation or deactivation of PC5 DRX may be configurable. For example, the PC5 DRX setting is notified by PC5-S signaling or PC5 RRC signaling, and the PC5 DRX activation / deactivation information is notified by PC5 MAC signaling or PSCCH or PSSCH. The UE-RX that receives the PC5 DRX activation / deactivation information activates / deactivates PC5 DRX according to the information. In this way, the PC5 DRX setting is notified in advance, and the activation or deactivation of PC5 DRX processing can be dynamically performed.

[0436] This section describes the PC5 DRX configuration in mode 1. The gNB configures PC5 DRX for the UE-TX. The gNB notifies the UE-TX of the PC5 DRX configuration. If the UE-TX does not recognize the PC5 DRX configuration, it cannot perform PC5 DRX processing with the UE-RX. Therefore, by notifying the UE-TX of the PC5 DRX configuration from the gNB, the UE-TX can perform PC5 DRX processing. After receiving the PC5 DRX configuration from the gNB, the UE-TX notifies the UE-RX of the PC5 DRX configuration. If the UE-RX does not recognize the PC5 DRX configuration, it cannot perform PC5 DRX processing with the UE-TX. Therefore, by receiving the PC5 DRX configuration configured by the gNB from the UE-TX, the UE-RX can perform PC5 DRX processing.

[0437] The gNB may notify the UE-TX of the PC5 DRX configuration by RRC signaling. Alternatively, the gNB may notify the UE-TX of the PC5 DRX configuration by MAC signaling. Alternatively, the gNB may notify the UE-TX of the PC5 DRX configuration by PDSCH. The notification of the PC5-DRX configuration from the UE-TX to the UE-RX may be performed by applying the method disclosed in Mode 2 as appropriate.

[0438] Activation or deactivation of PC5 DRX may be configurable. For example, the gNB notifies the UE-TX of the PC5 DRX configuration via RRC signaling. The UE-TX notifies the UE-RX of the PC5 DRX configuration via PC5 RRC signaling. The gNB notifies the UE-TX of PC5 DRX activation / deactivation information via MAC signaling or PDCCH. The UE-TX notifies the UE-RX of the PC5 DRX activation / deactivation information via PSCCH or PSSCH. Upon receiving the PC5 DRX activation / deactivation information, the UE-RX activates / deactivates PC5 DRX according to the information.

[0439] Alternatively, the PC5 DRX setting may be notified before the notification of PC5 DRX activation / deactivation. In this way, even in mode 1, the PC5 DRX setting can be notified in advance, and activation or deactivation of PC5 DRX processing can be performed dynamically.

[0440] The UE-TX may request PC5 DRX configuration from the gNB. The UE-TX notifies the gNB of the PC5 DRX configuration request. The UE-TX may notify the gNB of service-related information for PC5 communication with the UE-RX. The UE-TX may notify the gNB of the SL traffic pattern for PC5 communication with the UE-RX. The UE-TX may notify this information together with the PC5 DRX configuration request or by including it in the PC5 DRX configuration request. The gNB may use this information to configure PC5 DRX for the UE-TX. The gNB can then configure PC5 DRX suitable for PC5 communication between the UE-TX and the UE-RX.

[0441] In Mode 1, when the gNB performs dynamic scheduling for the UE-TX, it may not allow scheduling outside the active period of PC5 DRX. The UE-TX does not need to receive scheduling from the gNB, such as PDCCH, on Uu while communication via PC5 is not active due to the PC5 DRX setting. This allows for reduced power consumption by the UE-TX.

[0442] The time required for processing from when the UE-TX receives DCI until when it transmits the PSCCH or PSSCH in PC5, or the time set for this processing, may be taken into consideration. For example, when the gNB performs dynamic scheduling on the UE-TX, scheduling may not be permitted from the timing of transitioning out of the active period of PC5 DRX until a predetermined timing (for example, a timing earlier than the timing of transitioning into the active period by the time required for the above processing or the time set for the above processing). The UE-TX becomes able to transmit the PSCCH or PSSCH immediately after transitioning into the active period of PC5 DRX.

[0443] The gNB may use the PC5 DRX configuration for the UE-TX to perform DRX configuration between the gNB and the UE-TX. In the present disclosure, the DRX configuration between the gNB and the UE-TX may be referred to as the Uu DRX configuration. For example, the gNB may adjust the PC5 DRX configuration and the Uu DRX configuration so that both active periods coincide (in other words, align them). Alternatively, the gNB may adjust the PC5 DRX configuration and the Uu DRX configuration so that both active periods are contiguous. Alternatively, the gNB may adjust the PC5 DRX configuration and the Uu DRX configuration so that the period from the start of one active period to the end of both active periods is short, even if both active periods are discontinuous. For example, the gNB may perform Uu DRX configuration and PC5 DRX configuration taking into account the time required for processing from receiving DCI to transmitting PSCCH or PSSCH via PC5 or the time set for this processing. For example, the Uu DRX active transition timing may be set earlier than the PC5 DRX active transition timing by the time required for the above processing or the time set for the above processing.

[0444] In this way, it is possible to reduce the power consumption of the UE-TX.

[0445] In mode 1, when the gNB configures a Configured Grant (CG) of PC5 for the UE-TX, the UE-TX, upon receiving the CG setting of PC5 from the gNB, may notify the UE-RX of the CG setting of PC5. For example, by recognizing the CG setting configured for the UE-TX, the UE-RX can perform reception from the UE-TX using the CG setting. The UE-RX can simply perform reception from the UE-TX at the resource timing configured by the CG. This reduces the power consumption of the UE-RX. Furthermore, by using the CG, when data is generated in the UE-TX, the UE-TX can transmit the data to the UE-RX with low latency.

[0446] The gNB may configure both PC5 CG and PC5 DRX for the UE-TX. For example, if low latency is required, PC5 CG may be used, and if low latency is not required, PC5 DRX may be used.

[0447] The gNB may prohibit the UE-TX from simultaneously setting PC5 CG and PC5 DRX. This makes it possible to avoid complicated processing.

[0448] PC5 DRX may be set for each UE or for each UE-TX. When performing data communication with multiple UE-RX, it is preferable to perform data communication with the multiple UE-RX during the DRX active period set for the UE-TX.

[0449] PC5 DRX may be set for each UE-RX. When performing data communication with multiple UE-TX, it is preferable to perform data communication with the multiple UE-TX during the DRX active period set for the UE-RX.

[0450] PC5 DRX may be configured for each opposing UE pair. This allows for a PC5 DRX configuration suitable for the service communicated between the opposing UE pair. PC5 DRX may be configured for each PC5-S link. This allows for a PC5 DRX configuration suitable for the service communicated between the opposing UE pair. PC5 DRX may be configured for each PC5 QoS flow. This allows for a PC5 DRX configuration suitable for the QoS of the service communicated between the opposing UE pair.

[0451] The above-mentioned PC5 DRX setting may be one or more. Also, multiple PC5 DRX settings may be combined. This allows for flexible DRX setting. This allows for PC5 DRX settings suitable for various SL traffic patterns.

[0452] As specific examples of PC5 DRX setting information, the following (1) to (8) are disclosed.

[0453] (1)PC5 DRX cycle.

[0454] (2) PC5 DRX on interval.

[0455] (3)PC5 DRX offset.

[0456] (4) PC5 DRX inactivity period.

[0457] (5)PC5 DRX retransmission period.

[0458] (6) PC5 DRX retransmission inactivity period.

[0459] (7) PC5 DRX frequency band.

[0460] (8) A combination of (1) to (7).

[0461] With regard to (1) above, multiple PC5 DRX cycles may be set. For example, multiple PC5 DRX settings with different cycles may be set. For example, cycle A and a longer cycle B may be set. PC5 DRX processing is first performed using cycle A, and cycle A is performed for a specified period or a specified number of times. If no data is generated during that time, the system switches to cycle B. If data is generated during the PC5 DRX processing in cycle B, the system switches to cycle A. This makes it possible to flexibly set PC5 DRX settings according to the frequency of communication.

[0462] In mode 2, the PC5 DRX-on interval in (2) above may be set to be equal to or longer than the SL resource selection window period. Alternatively, the PC5 DRX-on interval may be set to be equal to the SL resource selection window period. In this way, at least one SL resource selected in the SL resource selection window period falls within the PC5 DRX-on interval. During the PC5 DRX-on interval, PSCCH and PSSCH can be transmitted using the SL resource.

[0463] In mode 2, the PC5 DRX offset in (3) above may be set to coincide with the start timing of the SL resource selection window. This allows the PC5 DRX-on interval to be set so that the SL resource selected during the SL resource selection window period falls within the PC5 DRX-on interval.

[0464] The above (1) to (6) may be managed by a timer.

[0465] The PC5 DRX frequency band in (7) above indicates the frequency resource used during the PC5 DRX active period. The resource may be in units of subcarriers, RBs (Resource Blocks), or subchannels. The resource may also be in units of BWPs (Band Width Parts). The carrier frequency may be set as the PC5 DRX frequency band. In Mode 2, a frequency band including the frequencies of the SL resource selection and reserved resources may be set as the PC5 DRX frequency band. This allows the UE-RX to limit the frequency bands used to search for transmissions from the UE-TX. This simplifies processing and reduces the power consumption required for searching.

[0466] FIG. 28 is a conceptual diagram showing a first example of PC5 DRX settings according to the fourth embodiment. In FIG. 28, the PC5 DRX settings include a PC5 DRC period, a PC5 DRX offset, and a PC5 DRX-on interval. The PC5 DRX-on interval occurs at the PC5 DRX period. The start of the PC5 DRX-on interval is set by the PC5 DRX offset. The PC5 DRX offset may be set not only in units of subframes or radio frames, but also in units of symbols or slots. This allows for more precise time settings.

[0467] The resources selected and reserved for SL communication from UE-TX to UE-RX are valid during the PC5 DRX active period. During the PC5 DRX active period, data can be transmitted from UE-TX to UE-RX using the reserved resources. Outside the PC5 DRX active period, data cannot be transmitted from UE-TX to UE-RX using the reserved resources. In the example of Figure 28, the PC5 DRX active period is the PC5 DRX on interval. Outside the PC5 DRX active period is the period excluding the PC5 DRX on interval.

[0468] Fig. 29 is a conceptual diagram showing a second example of PC5 DRX setting according to the fourth embodiment. In Fig. 29, a PC5 DRX inactivity period is set as the PC5 DRX setting. The following mainly describes the differences between Fig. 29 and Fig. 28. If a PSCCH or PSSCH occurs during a PC5 DRX on period, a further PC5 DRX active period is set for the PC5 DRX inactivity period from the occurrence of the PSCCH or PSSCH. If data is transmitted from UE-TX to UE-RX during a PC5 DRX on period, a further PC5 DRX active period may be set for the PC5 DRX inactivity period from the transmission of the data.

[0469] If a PSCCH or PSSCH occurs during this PC5 DRX inactivity period, the PC5 DRX active period is continued for a further PC5 DRX inactivity period from the occurrence of the PSCCH or PSSCH.If data is transmitted from UE-TX to UE-RX during this PC5 DRX inactivity period, the PC5 DRX active period may be continued for a further PC5 DRX inactivity period from the transmission of the data.

[0470] In this disclosure, the PSCCH, PSSCH, or data in PC5 may be simply referred to as data.

[0471] The timing may be statically determined in advance by a standard or the like. Alternatively, the timing may be included in the PC5 DRX configuration information. For example, the start of the PC5 DRX inactivity period may be the start timing of the slot following the slot in which data is generated. For example, it may be specified by symbol instead of slot.

[0472] If no data occurs within the PC5 DRX inactivity period after the last PSCCH occurrence, the PC5 DRX active period will be exceeded and the PC5 DRX active period will remain exceeded until the start of the next PC5 DRX on interval.

[0473] The resources selected and reserved for SL communication from UE-TX to UE-RX are valid during the PC5 DRX active period. During the PC5 DRX active period, data can be transmitted from UE-TX to UE-RX using the reserved resources. Outside the PC5 DRX active period, data cannot be transmitted from UE-TX to UE-RX using the reserved resources. In the example of Figure 29, the PC5 DRX active period is the period from the start of the PC5 DRX on interval to the end of the PC5 DRX inactivity period. The PC5 DRX outside the active period is the period from the end of the PC5 DRX inactivity period to the start of the PC5 DRX on interval.

[0474] This section discloses a PC5 DRX processing method for mode 2. When data is generated, the UE-TX searches for resources for SL communication before the PC5 DRX on interval. The UE-TX may also search for resources for SL communication in advance, regardless of when data is generated. Resource selection and reservation are possible early upon data generation. The UE-TX selects and reserves resources for the PC5 DRX on interval. When the UE-TX runs out of reserved resources for SL communication, it selects and reserves resources for SL communication again. The UE-TX may select and reserve resources multiple times during the PC5 DRX on interval. Furthermore, the UE-TX may select and reserve resources multiple times not only during the PC5 DRX on interval, but also during the active period of PC5 DRX.

[0475] The number of resources reserved for SL communication (sometimes referred to as a reselection counter) may be limited to within the PC5 DRX-on interval. This makes it possible to improve the efficiency of resource usage for other UEs. If the number of resources reserved for SL communication is set within the PC5 DRX-on interval, resource selection and reservation may be performed again during the PC5 DRX-on interval. If the reselection counter for a reserved resource becomes 0 during a DRX-on interval, the resource may be selected and reserved again. The number of resources reserved for SL communication (sometimes referred to as a reselection counter) does not need to be limited to within the PC5 DRX-on interval. This makes it possible to reduce the processing by the UE-TX of selecting and reserving resources again during an active period of PC5 DRX. This makes it possible to avoid the complexity caused by this processing.

[0476] If data is transmitted within a PC5 DRX on interval, a PC5 DRX inactivity period is started. If data is transmitted within a PC5 DRX inactivity period, a PC5 DRX inactivity period is started again. If the number of resources reserved for SL communication at the start of a PC5 DRX inactivity period is less than the resources available during the PC5 DRX inactivity period, the UE-TX may select and reserve resources again. If the reselection counter for resources reserved for SL communication becomes 0 during a PC5 DRX inactivity period, the UE-TX may select and reserve resources again. This method makes it possible to reserve resources for SL communication during a PC5 DRX active period.

[0477] Repetition transmission may be performed in SL communication. The repetition transmission may be performed during an active period of PC5 DRX. The repetition transmission may initiate a PC5 DRX inactivity period. The UE-TX may perform repetition transmission using resources for SL communication during the active period of PC5 DRX. The repetition transmission can improve the reception quality in the UE-RX.

[0478] When transitioning to a period outside the PC5 DRX active period, the UE-TX may release the reserved SL communication resources. Information indicating the release of SL communication resources may be provided. When this information is transmitted, it is preferable not to transition to a PC5 DRX inactivity period. When the UE-TX releases the reserved SL communication resources, it transmits this information. For example, the UE-TX may include this information in the PSCCH. Other UEs can receive the information. Other UEs can recognize that the resources reserved by the UE-TX that transmitted the information have been released. It is possible to improve the utilization efficiency of SL communication resources. Another control channel or signal may be provided for transmitting this information.

[0479] For example, the UE-TX may transmit the information in the last resource of the PC5 DRX inactivity period, or in the first resource after transitioning out of the PC5 DRX active period. In this way, the UE-TX can transmit the information immediately before or after transitioning out of the PC5 DRX active period.

[0480] UE-TX schedules UE-RX using SL communication resources during the active period of PC5 DRX, and transmits data according to the scheduling. If a PC5 DRX inactivity period is not set, and the amount of data exceeds the amount that can be transmitted in a DRX-on interval, the data may be transmitted in the next DRX-on interval.

[0481] This section discloses a PC5 DRX processing method for Mode 1. UE-TX performs DRX processing according to the PC5 DRX configuration received from the gNB. The PC5 DRX configuration may be performed using the method described above as appropriate. The DRX processing method may be performed using the method disclosed for Mode 2 as appropriate. However, UE-TX may use the PC5 DRX resources received from the gNB without selecting or reserving resources.

[0482] This document discloses DRX processing in UE-RX in Mode 1 and Mode 2. UE-RX derives the start timing of the PC5 DRX on interval using the PC5 DRX configuration received from UE-TX, and receives the PSCCH or PSSCH from UE-TX during the PC5 DRX on interval. In LTE, the SCI, which is PC5 control information, is included in the PSCCH. In NR, this information is included in both the PSCCH and PSSCH. UE-RX can receive the SCI from UE-TX by receiving the PSCCH or PSSCH. UE-RX receives data according to the scheduling information in the received SCI.

[0483] When an inactivity period is configured, UE-RX receives data from UE-TX in a PC5 DRX on interval and receives PSCCH or PSSCH from UE-TX from the time of data reception for the PC5 DRX inactivity period. If there is data during this PC5 DRX inactivity period, the PC5 DRX inactivity period begins again. If there is no data during this PC5 DRX inactivity period, the PC5 DRX active period ends after the end of the PC5 DRX inactivity period. UE-RX stops receiving PSCCH or PSSCH outside the PC5 DRX active period.

[0484] UE-RX receives PSCCH or PSSCH from UE-TX in the next PC5 DRX on interval using the PC5 DRX cycle. In this way, UE-RX receives PSCCH, PSSCH, or data during the PC5 DRX active period, and does not receive PSCCH, PSSCH, or data outside the PC5 DRX active period.

[0485] In this way, in direct communication between UEs in PC5, by performing PC5 DRX setting between UE-TX and UE-RX, it is possible to reduce the power consumption of the UE.

[0486] In NR, support for unicast and groupcast communication is being considered in PC5. For unicast and groupcast, HARQ using feedback is being considered. This document discloses the HARQ retransmission method when PC5 DRX is configured.

[0487] A period for retransmission may be provided. The aforementioned PC5 DRX retransmission period may be set. When a retransmission occurs, the UE-TX performs the retransmission within the set PC5 DRX retransmission period. Also, a period from reception of a HARQ feedback signal to retransmission may be set. The aforementioned PC5 DRX retransmission inactivity period may be set. After receiving a feedback signal, the UE-TX does not perform retransmission during the DRX retransmission inactivity period. The UE-TX may start the PC5 DRX retransmission period at the end timing of the PC5 DRX retransmission inactivity period.

[0488] FIG. 30 is a conceptual diagram showing a third example of PC5 DRX configuration according to the fourth embodiment. A PC5 DRX retransmission period and a PC5 DRX retransmission inactivity period are configured as the PC5 DRX configuration. In FIG. 30, differences from FIG. 29 will be mainly described. If data occurs within a PC5 DRX on interval, the PC5 DRX active period continues for a further PC5 DRX inactivity period from the occurrence of the data. If no data is transmitted from UE-TX to UE-RX within the PC5 DRX inactivity period, the PC5 DRX active period ends and the UE transitions to the end of the PC5 DRX active period.

[0489] During the PC5 DRX-on interval, UE-RX receives data transmitted from UE-TX to UE-RX. UE-RX transmits a feedback signal to UE-TX at the timing set for feedback (feedback timing). UE-RX may transmit the feedback signal using a feedback channel (PSFCH). Ack / Nack for the received data may be used as the feedback signal.

[0490] The feedback timing may be set by the UE-TX. The UE-TX notifies the UE-RX of the feedback timing. The UE-TX may notify the UE-RX of feedback resource information. The UE-TX may notify the feedback timing information together with the feedback resource information or by including it in the feedback resource information. The UE-TX may notify the resource information and timing information by RRC signaling of PC5. The UE-TX may notify the resource information and timing information by including it in AS configuration. Alternatively, the UE-TX may notify the resource information and timing information by including it in MAC signaling of PC5. Alternatively, the UE-TX may notify the resource information and timing information by including it in SCI. Early and dynamic notification becomes possible.

[0491] The reselection counters of resources reserved for SL communication may be set separately for initial transmission and feedback. Alternatively, the reselection counters of resources reserved for SL communication may be set for both initial transmission and feedback. Multiple HARQs may be processed in SL communication. The reselection counters of resources reserved for SL communication may be set for each HARQ.

[0492] The feedback timing may be configured by the gNB. The feedback resources may be configured by the gNB. For example, in Mode 1, the gNB notifies the UE-TX of this information together with other scheduling information. The UE-TX may notify the UE-RX of the received feedback timing and feedback resource information. The gNB may include the resource information and timing information in RRC signaling of Uu and notify the UE-TX. Alternatively, the gNB may include the resource information and timing information in MAC signaling of Uu and notify the UE-TX. Alternatively, the gNB may include the resource information and timing information in DCI and notify the UE-TX. The above-mentioned method may be applied as a method for notifying the information from UE-TX to UE-RX.

[0493] The feedback signal may be transmitted and received outside the PC5 DRX active period.

[0494] For example, as shown in Fig. 30, a feedback signal may be transmitted and received after the end of a PC5 DRX inactivity period. The feedback timing may be set to a period longer than the PC5 DRX inactivity period. The UE-RX transmits a feedback signal at the set feedback timing after the end of the PC5 DRX inactivity period. The UE-TX receives the feedback signal at the set feedback timing.

[0495] UE-TX performs retransmission if it receives Nack at the configured feedback timing, or if it does not receive anything. UE-TX searches, selects, and reserves resources for SL communication to be used within the PC5 DRX retransmission period, and performs retransmission using the reserved resources within the PC5 DRX retransmission period. UE-RX receives retransmission from UE-TX within the PC5 DRX retransmission period. UE-RX receives PSCCH and PSSCH from UE-TX within the PC5 DRX retransmission period, and receives retransmitted data. The PC5 DRX retransmission period becomes the PC5 DRX active period. In this way, retransmission processing can be performed even when PC5 DRX configuration is performed.

[0496] Retransmission may be applied to the determination of transition to a PC5 DRX inactivity period. If retransmission occurs during a PC5 DRX on interval or a PC5 DRX inactivity period, transition to a PC5 DRX inactivity period may be made again. This makes it possible to set the PC5 DRX active period according to the occurrence of data (including retransmitted data). This is effective, for example, when the feedback timing is set short.

[0497] Retransmissions may not be applied to the decision to transition to a PC5 DRX inactivity period. Even if a retransmission occurs during a PC5 DRX on interval or a PC5 DRX inactivity period, a transition to a PC5 DRX inactivity period will not occur again. This makes it possible to distinguish between retransmissions and initial transmissions. It is possible to set the PC5 DRX active period according to the occurrence of initial transmission data, regardless of retransmission processing. This is effective, for example, when communication quality is good and retransmissions are rare.

[0498] Fig. 31 is a conceptual diagram showing a fourth example of PC5 DRX setting according to the fourth embodiment. Fig. 31 shows a case where retransmission is applied to the determination of transition to a PC5 DRX inactivity period. The following mainly describes the parts of Fig. 31 that are different from Fig. 29. If data occurs within a PC5 DRX on interval, the PC5 DRX active period continues from the occurrence of the data for the PC5 DRX inactivity period.

[0499] For example, a feedback signal may be transmitted and received during a PC5 DRX inactivity period. The feedback timing may be set to a period shorter than the PC5 DRX inactivity period. The UE-RX transmits a feedback signal at the set feedback timing after the end of the PC5 DRX inactivity period. The UE-TX receives the feedback signal at the set feedback timing.

[0500] UE-TX performs retransmission if it receives Nack at the configured feedback timing, or if it does not receive anything. UE-TX performs retransmission within the PC5 DRX inactivity period. If UE-TX performs retransmission within the PC5 DRX inactivity period, it starts the PC5 DRX inactivity period again. If no data (including retransmitted data) is sent from UE-TX to UE-RX within the PC5 DRX inactivity period, the PC5 DRX active period ends and the UE transitions to outside the PC5 DRX active period.

[0501] UE-RX only needs to receive data (including retransmission data) from UE-TX during the PC5 DRX active period. UE-RX only needs to receive PSCCH and PSSCH during the PC5 DRX interval and PC5 DRX inactivity period, and receive data (including retransmission data) from UE-TX. To achieve this, the processing method for PC5 DRX configuration disclosed in FIG. 29 can be applied.

[0502] In this way, it is possible to avoid the PC5 DRX processing between UE-TX and UE-RX becoming complicated.

[0503] Although the example in FIG. 31 shows a case where neither a PC5 DRX retransmission period nor a PC5 DRX retransmission inactivity period is set, the PC5 DRX retransmission period and the PC5 DRX retransmission inactivity period may be set. For example, both periods are set so that the PC5 DRX retransmission period is included within the PC5 DRX inactivity period. Although this complicates the PC5 DRX processing between UE-TX and UE-RX, it becomes possible to apply unified processing, including cases where the PC5 DRX retransmission period is set outside the PC5 DRX inactivity period. This allows for flexible setting of the retransmission period, thereby avoiding complication of processing even in such cases.

[0504] In the above-mentioned method, the case where Ack / Nack in HARQ feedback is used as feedback information is disclosed. Other feedback information may be used. The other feedback information may be appropriately applied when the feedback timing and feedback resource are configured by the UE-TX or the gNB. Similar effects can be obtained.

[0505] In the present disclosure, the UE in which service data is generated is referred to as UE-TX. For example, if UE-TX is referred to as UE1 and UE-RX is referred to as UE2, when service data is generated in UE2 and the data is transmitted to UE1, it is advisable to apply the method of the present disclosure by treating UE2 as UE-TX and UE1 as UE-RX. Similar effects can be obtained.

[0506] The feedback information includes CSI report information transmitted from UE-RX (UE2) to UE-TX (UE1). By applying the method of the present disclosure with UE2 as UE-TX and UE1 as UE-RX, the CSI report information may be transmitted and received within the PC5 DRX active period. This enables transmission and reception of information requiring a larger amount of information, such as CSI report information.

[0507] If UE1 and UE2 are UEs performing direct UE-to-UE communication using PC5, PC5 DRX configuration may be performed in both directions of communication. In PC5 DRX configuration for communication from UE1 to UE2, UE1 is the transmitting UE and UE2 is the receiving UE. Therefore, UE1 should be set as UE-TX and UE2 as UE-RX, and the above-mentioned method should be applied as appropriate. In PC5 DRX configuration for communication from UE2 to UE1, UE2 is the transmitting UE and UE1 is the receiving UE. Therefore, UE2 should be set as UE-TX and UE1 should be set as UE-RX, and the above-mentioned method should be applied as appropriate.

[0508] This disclosure discloses a method for matching (i.e., aligning) PC5 DRX configurations in both directions in PC5 direct communication between UEs. As described above, the PC5 DRX configurations in both directions may be performed, for example, so that both active periods are matched (i.e., aligned). Alternatively, the PC5 DRX configurations in both directions may be performed, for example, so that both active periods are continuous. Alternatively, for example, even if both active periods are discontinuous, the PC5 DRX configurations in both directions may be performed so that the period from the start of one active period to the end of both active periods is short.

[0509] For example, the PC5 DRX configuration in one direction may be adjusted to match the PC5 DRX configuration in the other direction. The PC5 DRX configuration in either direction may be performed first. For example, the PC5 DRX configuration for communication from UE1 to UE2 may be performed, and the PC5 DRX configuration for communication from UE2 to UE1 may be adjusted to match the PC5 DRX configuration for communication from UE1 to UE2. For example, either UE may perform the PC5 DRX configuration in both directions so that the PC5 DRX configurations in both directions are adjusted. For example, a gNB connected to either UE may perform the PC5 DRX configuration in both directions so that the PC5 DRX configurations in both directions are adjusted.

[0510] The previously set PC5 DRX setting information may be notified to a node that matches the PC5 DRX settings for both directions.The node that matches the PC5 DRX settings for both directions can use the previously set PC5 DRX setting to set the PC5 DRX setting that will be set later so that the PC5 DRX settings for both directions are matched.

[0511] By matching the PC5 DRX settings in both directions, it is possible to reduce the power consumption of UEs that perform direct UE-to-UE communication using PC5.

[0512] Figures 32 and 33 are sequence diagrams showing a first example of a method for aligning DRX in both directions in direct communication between UEs at PC5, according to embodiment 4. Figures 32 and 33 are connected at the position of boundary line BL3233. Figures 32 and 33 show a case where UE1 is located in the Out Of Coverage (OOC) of the gNB, and UE2 is located in the In Coverage (IC) of the gNB.

[0513] Since UE1 is out-of-context, in step ST2401, UE1 performs PC5 DRX configuration on UE2 for communication from UE1 to UE2. In step ST2402, UE1 notifies UE2 of the PC5 DRX configuration information. In step ST2403, UE2 performs the PC5 DRX configuration received from UE1. In step ST2404, UE2 notifies that it has completed PC5 DRX configuration for communication from UE1 to UE2. In this way, PC5 DRX configuration for communication from UE1 to UE2 becomes possible. As a result, in step ST2405, PC5 DRX processing is performed for SL communication. UE1 performs resource search, selection, and reservation for SL communication from UE1 to UE2, and performs data communication using the PC5 DRX processing.

[0514] UE2 decides to perform PC5 DRX configuration for communication from UE2 to UE1. In Step ST2406, UE2 notifies the gNB to which it is connected of a PC5 DRX configuration request for communication from UE2 to UE1. UE2 notifies the gNB of the SL traffic pattern for communication from UE2 to UE1. UE2 may also notify the gNB of service-related information for communication from UE2 to UE1 (e.g., service identifier, service type, service QoS, frequency of occurrence of service data, etc.). This allows the gNB to derive the SL traffic pattern for communication from UE2 to UE1. UE2 also notifies the gNB of PC5 DRX configuration information for communication from UE1 to UE2. UE2 may notify this information together with the request information or by including this information in the request information.

[0515] In Step ST2407, the gNB that has received the PC5 DRX setting request from UE2 to UE1 uses the information to perform PC5 DRX setting for communication from UE2 to UE1. The gNB performs PC5 DRX setting for communication from UE2 to UE1 using the DRX setting from UE1 to UE2 so that the PC5 DRX settings in both directions are matched. In this way, the gNB can match the PC5 DRX settings in both directions.

[0516] In Step ST2408, the gNB notifies UE2 of PC5 DRX setting information. In Step ST2409, UE2 performs PC5 DRX setting. Also, in Step ST2410, UE2 notifies UE1 of the PC5 DRX setting for communications from UE2 to UE1. In Step ST2411, UE1 performs PC5 DRX setting. In Step ST2412, UE1 notifies UE2 that it has completed PC5 DRX setting for communications from UE2 to UE1. This makes it possible to perform PC5 DRX processing for communications from UE2 to UE1.

[0517] In Step ST2413, UE2 notifies the gNB that PC5 DRX configuration for communication from UE2 to UE1 has been completed. UE2 may include scheduling request information for SL communication from UE2 to UE1 in the PC5 DRX configuration completion notification. Alternatively, UE2 may notify the gNB of scheduling request information for SL communication from UE2 to UE1, separately from the PC5 DRX configuration completion notification. In Step ST2414, the gNB performs resource scheduling for communication from UE2 to UE1. In Step ST2415, the gNB notifies UE2 of the scheduling information for communication from UE2 to UE1. In Step ST2416, UE2 performs data communication with UE1 using the PC5 DRX process.

[0518] In direct communication between UEs in PC5, by matching the PC5 DRX settings in both directions in this manner, it is possible to reduce the power consumption of UE1 and UE2 that perform direct communication between UEs in PC5.

[0519] Figures 34 and 35 are sequence diagrams showing a second example of a method for aligning DRX in both directions in direct communication between UEs at PC5, according to the fourth embodiment. Figures 34 and 35 are connected at the position of boundary line BL3435. Figures 34 and 35 show a case where UE1 is present in the IC of gNB1, and UE2 is present in the IC of gNB2. Since UE1 is the IC, the example shows a case where gNB1 schedules communication from UE1 to UE2 at PC4.

[0520] UE1 decides to perform PC5 DRX configuration for communication from UE1 to UE2. In Step ST2501, UE1 notifies the gNB1 to which it is connected of a PC5 DRX configuration request for communication from UE1 to UE2. UE1 notifies the gNB of the SL traffic pattern for communication from UE1 to UE2. UE1 may also notify the gNB of service-related information for communication from UE1 to UE2 (e.g., service identifier, service type, service QoS, frequency of occurrence of service data, etc.). This enables gNB1 to derive the SL traffic pattern for communication from UE1 to UE2.

[0521] In Step ST2502, the gNB1 that has received the PC5 DRX setting request from UE1 to UE2 uses the information to perform PC5 DRX setting for communications from UE1 to UE2. In Step ST2503, the gNB1 notifies UE1 of the PC5 DRX setting information. In Step ST2504, UE1 performs PC5 DRX setting. Also, in Step ST2505, UE1 notifies UE2 of the PC5 DRX setting for communications from UE1 to UE2. In Step ST2506, UE2 performs PC5 DRX setting. In Step ST2507, UE2 notifies UE1 that it has completed PC5 DRX setting for communications from UE1 to UE2. This makes it possible to perform PC5 DRX processing for communications from UE1 to UE2.

[0522] In Step ST2508, UE1 notifies gNB1 that PC5 DRX configuration for communication from UE1 to UE2 has been completed. UE1 may include scheduling request information for SL communication from UE1 to UE2 in the PC5 DRX configuration completion notification. Alternatively, UE1 may notify gNB1 of scheduling request information for SL communication from UE1 to UE2, separately from the PC5 DRX configuration completion notification. In Step ST2509, gNB1 performs resource scheduling for communication from UE1 to UE2. In Step ST2510, gNB1 notifies UE1 of scheduling information for communication from UE1 to UE2. In Step ST2511, UE1 performs data communication with UE2 using the PC5 DRX process.

[0523] UE2 decides to perform PC5 DRX setting in communication from UE2 to UE1. After UE2 decides to perform PC5 DRX setting in communication from UE2 to UE1, the method of performing data communication with UE1 using PC5 DRX processing may be appropriately applied to the methods disclosed in Figures 32 and 33. Steps ST2406 to ST2416 in Figures 32 and 33 may be applied. Similar effects can be obtained.

[0524] By doing this, even when both UE1 and UE2 are gNB ICs, it becomes possible to execute PC5 DRX processing that matches the PC5 DRX settings in both directions in direct UE-to-UE communication via PC5. This makes it possible to reduce the power consumption of UE1 and UE2 that perform direct UE-to-UE communication via PC5.

[0525] In communication between a remote UE and a network via a relay UE, PC5 DRX setup is performed between the remote UE and the relay UE. PC5 DRX processing is performed between the remote UE and the relay UE. In communication between a remote UE and a network via a relay UE, PC5 communication is performed between the remote UE and the relay UE. As a method for setting PC5 DRX between the remote UE and the relay UE, the DRX setup method for direct communication between UEs in PC5 described above may be applied as appropriate.

[0526] For example, in SL communication from a remote UE to a relay UE, the remote UE may be designated as UE-TX and the relay UE may be designated as UE-RX. In SL communication from a relay UE to a remote UE, the relay UE may be designated as UE-TX and the remote UE may be designated as UE-RX. For example, the mode 2 method may be applied to a remote UE located in the OOC of the gNB. The mode 1 method may be applied to a relay UE located in the IC of the gNB. In this way, in communication between a remote UE and a NW via a relay UE, PC5 DRX setting between the remote UE and the relay UE can be performed, and PC5 DRX processing can be performed between the remote UE and the relay UE. This makes it possible to reduce the power consumption of the remote UE and the relay UE.

[0527] The PC5 DRX settings may be matched in both directions, that is, SL communication from the remote UE to the relay UE and SL communication from the relay UE to the remote UE (in other words, they may be aligned). As a method for this, the method of matching the PC5 DRX settings in both directions in direct communication between UEs using PC5, as described above, may be applied as appropriate. For example, the methods disclosed in Figures 32 and 33 may be applied as appropriate. UE1, UE2, and a gNB in ​​Figures 32 and 33 are the remote UE, the relay UE, and a gNB connected to the relay UE, respectively. The gNB connected to the relay UE matches the PC5 DRX settings in both directions. By matching the PC5 DRX settings in both directions in this way, it is possible to further reduce the power consumption of the remote UE and the relay UE.

[0528] In step ST2406 in FIG. 32 and FIG. 33, UE2 notifies the gNB of the SL traffic pattern from UE2 to UE1. When a relay UE is used, the relay UE does not generate service data for communication via PC5. Communication is performed from the NW to the remote UE. For this reason, the relay UE may not recognize the traffic pattern of communication to the remote UE. A method for solving such a problem will be disclosed.

[0529] In communication from the NW to the remote UE, the relay UE derives a traffic pattern from the relay UE to the remote UE. As a method of derivation, the relay UE may measure data communication from the relay UE to the remote UE at PC5. As a measurement method, the method disclosed in the first embodiment may be applied as appropriate. As another method, the remote UE may notify the relay UE of the traffic pattern from the relay UE to the remote UE. The remote UE may derive the traffic pattern from the relay UE to the remote UE from information about services communicated with the NW via the relay UE. Alternatively, the remote UE may measure data communication at PC5 to the relay UE. In this way, the relay UE can recognize the traffic pattern of communication to the remote UE.

[0530] As another method, the gNB or the UPF may derive a traffic pattern from the relay UE to the remote UE in communication from the NW to the remote UE. The measurement method described above may be applied as appropriate. If the gNB derives the traffic pattern, the gNB may use the derivation result in step ST2407 of Figures 32 and 33. If the UPF derives the traffic pattern, the UPF may notify the gNB of the derived traffic pattern. The gNB may use the traffic pattern received from the UPF in step ST2407 of Figures 32 and 33. Similar effects can be obtained.

[0531] Although the traffic pattern of communication from the NW to the remote UE has been disclosed, the above-described method may also be applied as appropriate to the traffic pattern of communication from the remote UE to the NW.

[0532] Another method is disclosed for matching (in other words, aligning) the PC5 DRX settings in both directions, SL communication from the remote UE to the relay UE and SL communication from the relay UE to the remote UE. The PC5 DRX settings are matched in both directions by taking advantage of the fact that the remote UE is connected to the gNB via the relay UE. The gNB connected to the relay UE performs the PC5 DRX settings for communication from the remote UE to the relay UE. The gNB connected to the relay UE may also perform the PC5 DRX settings in both directions between the remote UE and the relay UE.

[0533] The remote UE may request the gNB via the relay UE to set up PC5 DRX for communication from the remote UE to the relay UE. Alternatively, the relay UE may request the gNB to set up PC5 DRX for communication from the remote UE to the relay UE. Upon receiving the request, the gNB sets up PC5 DRX for communication from the remote UE to the relay UE.

[0534] The remote UE may request the gNB via the relay UE to configure PC5 DRX for both directions between the remote UE and the relay UE. Alternatively, the relay UE may request the gNB to configure PC5 DRX for both directions between the remote UE and the relay UE. Upon receiving the request, the gNB configures PC5 DRX for both directions of communication between the remote UE and the relay UE.

[0535] The gNB configures the PC5 DRX settings of both the remote UE and the relay UE so that the PC5 DRX settings of both the remote UE and the relay UE are aligned, thereby further reducing the power consumption of the remote UE and the relay UE.

[0536] 36 and 37 are sequence diagrams showing an example of a method for performing PC5 DRX configuration between a remote UE and a relay UE in communication between the remote UE and a NW via a relay UE, according to the fourth embodiment. Figures 36 and 37 are connected at the boundary line BL3637. Figures 36 and 37 show a case where the remote UE is located in the OOC of the gNB and the relay UE is located in the IC of the gNB. Figures 36 and 37 show a case where the remote UE requests the gNB to perform PC5 DRX configuration for communication from the remote UE to the relay UE, and the relay UE requests the gNB to perform PC5 DRX configuration for communication from the relay UE to the remote UE. Figures 36 and 37 show a method where a gNB connected to a relay UE configures PC5 DRX configurations in both directions between the remote UE and the relay UE so that the PC5 DRX configurations in both directions are matched.

[0537] In Step ST2601, the remote UE requests the gNB connected to the relay UE to configure PC5 DRX for communication from the remote UE to the relay UE. The request is notified via the relay UE. The remote UE may notify the traffic pattern of communication from the remote UE to the NW together with the request or by including the traffic pattern in the request. In Step ST2602, the gNB performs PC5 DRX configuration for communication from the remote UE to the relay UE. In Step ST2603, the gNB notifies the remote UE of PC5 DRX configuration information for communication from the remote UE to the relay UE. The configuration information is notified via the relay UE. In Step ST2604, the remote UE performs PC5 DRX configuration for communication from the remote UE to the relay UE.

[0538] Furthermore, in Step ST2605, the remote UE notifies the relay UE of PC5 DRX setting information for communication from the remote UE to the relay UE. In Step ST2606, the relay UE performs PC5 DRX setting for communication from the remote UE to the relay UE. In Step ST2607, the relay UE notifies the remote UE that the PC5 DRX setting has been completed. In this manner, PC5 DRX setting for communication from the remote UE to the relay UE becomes possible, and in Step ST2608, PC5 DRX processing is performed for SL communication. The remote UE performs resource search, selection, and reservation for SL communication from the remote UE to the relay UE, and performs data communication using the PC5 DRX processing.

[0539] PC5 DRX configuration is performed for communication from the relay UE to the remote UE. As a method for this, the methods disclosed in Figures 32 and 33 may be applied as appropriate. UE1, UE2, and gNB in ​​Figures 32 and 33 may be referred to as the remote UE, the relay UE, and the gNB, respectively. Steps ST2406 to ST2416 in Figures 32 and 33 may be applied as appropriate to steps ST2609 to ST2619 in Figures 36 and 37. In this way, the gNB can match the PC5 DRX configuration in both directions between the remote UE and the relay UE. This makes it possible to further reduce the power consumption of the remote UE and the relay UE.

[0540] In Step ST2609, the relay UE does not need to notify the gNB of the PC5 DRX setting information of the relay UE from the remote UE. Since the gNB has performed the PC5 DRX setting for the communication from the remote UE to the relay UE in Step ST2602, it is aware of the PC5 DRX setting. In Step ST2610, the gNB may perform the PC5 DRX setting for the communication from the relay UE to the remote UE using the PC5 DRX setting for the communication from the remote UE to the relay UE performed in Step ST2602 so as to match the PC5 DRX setting for both directions between the remote UE and the relay UE. Similar effects can be obtained.

[0541] This allows PC5 DRX settings to be configured between the remote UE and the relay UE, thereby reducing the power consumption of the remote UE and the relay UE. It also allows PC5 DRX settings to be configured in both directions between the remote UE and the relay UE. This further reduces the power consumption of the remote UE and the relay UE. In communications between the remote UE and the network via the relay UE, the power consumption of the relay UE and the remote UE can be reduced.

[0542] Embodiment 5 Another method for solving the problem described in the first embodiment will be disclosed.

[0543] In communication between a remote UE and a network via a relay UE, the DRX setting between the relay UE and the network and the PC5 DRX setting between the remote UE and the relay UE are matched (in other words, aligned). The DRX setting between the relay UE and the network may be a paging DRX setting when the relay UE is in the RRC_Idle or RRC_Inactive state, or a C-DRX setting when the relay UE is in the RRC_Connected state. The PC5 DRX setting between the remote UE and the relay UE may be a bidirectional PC5 DRX setting between the remote UE and the relay UE.

[0544] The relay UE may configure DRX settings between the relay UE and the network so that the DRX setting between the relay UE and the network and the PC5 DRX setting between the remote UE and the relay UE are matched. In the DL direction, that is, the DRX setting from the network to the relay UE and the PC5 DRX setting from the relay UE to the remote UE may be matched. In the UL direction, that is, the PC5 DRX setting from the remote UE to the relay UE and the DRX setting from the relay UE to the network may be matched. The DRX settings in both the DL and UL directions may be matched with the PC5 DRX setting.

[0545] As a method for matching the DRX setting between the relay UE and the NW with the PC5 DRX setting between the remote UE and the relay UE, the methods disclosed in the first to fourth embodiments may be applied as appropriate.

[0546] For example, the remote UE performs DRX configuration for both the DRX configuration between the relay UE and the NW and the PC5 DRX configuration between the remote UE and the relay UE so that the DRX configuration matches. The remote UE performs PC5 DRX configuration for communication between the remote UE and the relay UE. The remote UE performs PC5 DRX configuration for communication from the remote UE to the relay UE. The remote UE may also perform PC5 DRX configuration for communication from the relay UE to the remote UE. The method disclosed in the fourth embodiment may be applied as appropriate.

[0547] The remote UE uses the PC5 DRX configuration between the relay UE to configure DRX between the relay UE and the NW so that the DRX configuration between the relay UE and the NW matches the PC5 DRX configuration between the remote UE and the relay UE. The remote UE may determine DRX-related information including the DRX configuration. For example, specific examples of the DRX-related information include a paging DRX configuration requested of the relay UE, a C-DRX configuration requested of the relay UE, or a traffic pattern between the remote UE and the NW. The DRX-related information may also be a combination of these.

[0548] The remote UE notifies the NW via the relay UE of DRX-related information between the relay UE and the NW. The NW node, for example, a gNB or an AMF, uses the DRX-related information to configure DRX between the relay UE and the NW. As a method for this, the methods disclosed in the first to third embodiments of the present invention may be applied as appropriate.

[0549] By doing so, in communication between a remote UE and a network via a relay UE, it is possible to match the DRX setting between the relay UE and the network with the PC5 DRX setting between the remote UE and the relay UE. Because the remote UE is aware of the service of communication between the remote UE and the network, for example, the remote UE can perform the PC5 DRX setting and the DRX setting between the relay UE and the network based on the information it is aware of. It is possible to perform the PC5 DRX setting and the DRX setting suitable for the service of communication between the remote UE and the network.

[0550] For example, the relay UE may configure both DRX settings between the relay UE and the network and PC5 DRX settings between the remote UE and the relay UE so that the DRX settings are consistent with each other. The relay UE performs PC5 DRX settings for communication between the remote UE and the relay UE. The method disclosed in the fourth embodiment may be applied as appropriate.

[0551] The relay UE uses the PC5 DRX configuration with the remote UE to perform DRX configuration between the relay UE and the NW so that the DRX configuration between the relay UE and the NW matches the PC5 DRX configuration between the remote UE and the relay UE. The relay UE notifies the NW of DRX-related information between the relay UE and the NW. A NW node, for example, a gNB or an AMF, performs DRX configuration between the relay UE and the NW using the DRX-related information. As a method for performing these operations, the methods disclosed in Modification 1 of Embodiments 1 to 3 may be applied as appropriate.

[0552] By doing so, in communication between a remote UE and a NW via a relay UE, it is possible to match the DRX setting between the relay UE and the NW with the PC5 DRX setting between the remote UE and the relay UE. Also, by having the relay UE perform the settings, even in a case where multiple remote UEs are connected to the relay UE, it is possible to perform PC5 DRX settings and DRX settings that are suitable for the data generation pattern in communication between multiple remote UEs and the relay UE, for example.

[0553] For example, the gNB may configure both DRX settings between the relay UE and the NW and PC5 DRX settings between the remote UE and the relay UE so that the DRX settings are consistent. The gNB connected to the relay UE configures the PC5 DRX settings for communication between the remote UE and the relay UE. The method disclosed in the fourth embodiment may be applied as appropriate.

[0554] The gNB uses the PC5 DRX configuration with the remote UE to perform DRX configuration between the relay UE and the NW so that the DRX configuration between the relay UE and the NW matches the PC5 DRX configuration between the remote UE and the relay UE. The gNB may notify the NW of DRX-related information between the relay UE and the NW. A NW node, for example, an AMF, performs DRX configuration between the relay UE and the NW using the DRX-related information. As a method for performing these operations, the methods disclosed in the first to third embodiments of the present invention may be applied as appropriate.

[0555] By doing so, in communication between a remote UE and a network via a relay UE, it is possible to match the DRX setting between the relay UE and the network with the PC5 DRX setting between the remote UE and the relay UE. Also, by having the gNB perform the setting, the gNB can recognize all communication statuses of the relay UE connected to the gNB and the remote UE connected to the relay UE. Therefore, as a system, it is possible to perform more appropriate PC5 DRX setting and DRX setting in communication between a remote UE and a network via the gNB.

[0556] By doing so, in communication between the remote UE and the NW via the relay UE, it is possible to match the DRX setting between the relay UE and the NW with the PC5 DRX setting between the remote UE and the relay UE, thereby further reducing the power consumption of the remote UE and the relay UE.

[0557] When a remote UE connects to a gNB via a relay UE, the gNB may perform scheduling for communication using PC5 between the remote UE and other UEs. The remote UE may notify, via the relay UE, information about the service of communication using PC5 with other UEs. The gNB uses this information to schedule communication using PC5 to the remote UE. The gNB notifies the remote UE of the scheduling information via the relay UE, and the remote UE performs communication using PC5 with other UEs in accordance with the scheduling information received from the gNB via the relay UE.

[0558] The remote UE may notify the gNB of a scheduling request (SR) via the relay UE. The gNB may perform scheduling for the remote UE using the SR received from the remote UE via the relay UE. The remote UE may notify the gNB of a buffer status report (BSR) via the relay UE. The gNB may perform scheduling for the remote UE using the BSR received from the remote UE via the relay UE.

[0559] A PUCCH may be provided for transmission of the SR of the remote UE from the relay UE to the gNB. The gNB may configure a PUCCH for transmission of the SR of the remote UE to the relay. Alternatively, a PUSCH may be used for transmission of the SR of the remote UE from the relay UE to the gNB. The relay UE may notify the gNB of the SR of the remote UE by including it in the PUSCH. Alternatively, MAC signaling may be used for transmission of the SR of the remote UE from the relay UE to the gNB. It may be configured as a MAC CE. Alternatively, RRC signaling may be used for transmission of the SR of the remote UE from the relay UE to the gNB. It becomes possible to notify a large amount of information.

[0560] The above-mentioned method may also be applied appropriately to the transmission of the BSR of the remote UE from the relay UE to the gNB.

[0561] In this way, even if a remote UE is outside the coverage of a gNB, when it connects to a gNB via a relay UE, it can acquire scheduling information for communication using PC5 from the gNB. Since the gNB enables scheduling of communication using PC5 between a remote UE connected to a relay UE and other UEs, it is possible to reduce, for example, conflicts of resources used for these communications. This makes it possible to improve resource utilization efficiency.

[0562] In communication between a remote UE and a NW via a relay UE, the CG resource timing set between the gNB and the relay UE may be matched with the CG resource timing set between the remote UE and the relay UE. For example, the gNB may schedule the remote UE via the relay UE, and the gNB may match the CG resource timing in Uu set for the relay UE with the CG resource timing in PC5 set for the remote UE. The gNB may set the resource timings of both to be within a predetermined period. This can further reduce the power consumption of the remote UE and the relay UE.

[0563] In the present disclosure, the UE in which service data is generated is referred to as UE-TX. For example, if UE-TX is referred to as UE1 and UE-RX is referred to as UE2, when service data is generated in UE2 and the data is transmitted to UE1, it is advisable to apply the method of the present disclosure by treating UE2 as UE-TX and UE1 as UE-RX. Similar effects can be obtained.

[0564] The above-described embodiments and their modifications are merely examples, and the embodiments and their modifications can be freely combined. Furthermore, any of the components of the embodiments and their modifications can be modified or omitted as appropriate.

[0565] For example, in the above-described embodiments and their modifications, a subframe is an example of a time unit for communication in a fifth-generation base station communication system. It may also be a scheduling unit. In the above-described embodiments and their modifications, the processing described as being performed in subframe units may also be performed in TTI units, slot units, subslot units, or minislot units.

[0566] For example, the methods disclosed in the above-described embodiments and their modifications may be applied to services that use SL communication, not limited to V2X (Vehicle-to-everything) services, such as proximity-based services, public safety, communication between wearable devices, and communication between devices in factories.

[0567] Although the present disclosure has been described in detail, the above description is illustrative in all respects and is not restrictive. It is understood that countless variations not illustrated can be envisioned. [Explanation of symbols]

[0568] 200, 210 communication system, 202 communication terminal device (communication terminal), 203, 207, 213, 217, 223-1, 224-1, 224-2, 226-1, 226-2 base station device (base station), 204, 214 management device.

Claims

1. A first terminal device in a communication system, The communication system includes a plurality of terminal devices that perform unicast communication in side link communication via a PC5 interface, the plurality of terminal devices including the first terminal device that is a transmitting terminal device and a second terminal device that is a receiving terminal device; The first terminal device is configured to determine a DRX (Discontinuous reception) setting for a reception operation of the second terminal device in the unicast communication, and to transmit the DRX setting to the second terminal device. A first terminal device.

2. The first terminal device is configured to transmit the DRX configuration to the second terminal device using PC5-RRC (Radio Resource Control) signaling for AS (Access Stratum) configuration. The first terminal device according to claim 1 .

3. The DRX setting includes information on a DRX cycle and information on an offset for determining a start timing of the DRX cycle. The first terminal device according to claim 1 .

4. The DRX setting is Information regarding the on-interval; Information about periods of inactivity; Information regarding the retransmission period; Information about the retransmission inactivity period; and Including, The first terminal device according to claim 1 .

5. the on-interval, the inactivity period, the retransmission period, and the retransmission inactivity period are each set by a timer. The first terminal device according to claim 4 .

6. A second terminal device in a communication system, The communication system includes a plurality of terminal devices that perform unicast communication in side link communication via a PC5 interface, the plurality of terminal devices including a first terminal device that is a transmitting terminal device and the second terminal device that is a receiving terminal device; The second terminal device is configured to receive, from the first terminal device, a DRX (Discontinuous reception) setting for a reception operation of the second terminal device in the unicast communication, and to perform the reception operation in accordance with the DRX setting. A second terminal device.

7. A communication system including a plurality of terminal devices that perform unicast communication in sidelink communication via a PC5 interface, the plurality of terminal devices including a first terminal device that is a transmitting terminal device and a second terminal device that is a receiving terminal device, The first terminal device is configured to determine a DRX (Discontinuous reception) setting for a reception operation of the second terminal device in the unicast communication, and to transmit the DRX setting to the second terminal device. Communication system.

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