First communication terminal device, second communication terminal device, base station device, and communication system

Abstract

To provide a communication terminal device and a communication system that ensure the quality of service (QoS) required for a service in sidelink communication and improve the reliability of the service.SOLUTION: A communication system includes a base station and a plurality of communication terminals configured to be able to perform communication with the base station and terminal-to-terminal communication. A first communication terminal transmits a scheduling request for terminal-to-terminal communication with a second communication terminal to a third communication terminal. The third communication terminal transmits the scheduling request received from the first communication terminal to the base station. In response to the scheduling request received from the third communication terminal, the base station generates scheduling information for terminal-to-terminal communication between the first communication terminal and the second communication terminal, and transmits the scheduling information to the third communication terminal. The third communication terminal transmits the scheduling information received from the base station to the first communication terminal.SELECTED DRAWING: None

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 wireless sections and System Architecture Evolution (SAE) for the overall system configuration including a core network and a wireless access network (hereinafter collectively referred to as a network) (for example, Non-Patent Documents 1 to 5). This communication method is also called a 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. Also, 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, which are described in Non-Patent Document 1 (Chapter 5), will be described with reference to FIG. 1. FIG. 1 is an explanatory diagram showing the configuration of a radio frame used in an LTE communication system. In FIG. 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 signal includes 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 device (hereinafter, sometimes simply referred to as a "base station") to a communication terminal device (hereinafter, sometimes simply referred to as a "communication terminal") such as a mobile terminal device (hereinafter, sometimes 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 OFDM (Orthogonal Frequency Division Multiplexing) symbols used for PDCCHs from the base station. 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 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 (Acknowledgement) / Nack (Negative Acknowledgement), which are response signals to uplink transmission. The PDCCH is also called an L1 / L2 control signal.

[0009] A 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 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. 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 is a response signal to a downlink transmission. The PUCCH carries Channel State Information (CSI). The CSI is composed 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 a 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] A Physical Uplink Shared Channel (PUSCH) is a channel for uplink transmission from a communication terminal to a base station. An 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 is a response signal to an 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 known symbols 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 (DM-RS) Demodulation Reference Signal (PRS), 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 known symbol in the LTE communication system. Two types of uplink reference signals are defined: a data demodulation reference signal (DM-RS) and a sounding reference signal (SRS).

[0016] The transport channel described in Non-Patent Document 1 (Chapter 5) will be explained. Among the downlink transport channels, the broadcast channel (BCH) is broadcast to the entire coverage of the base station (cell). The BCH is mapped to the 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) of 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 of communication terminals to enable low power consumption of the communication terminals. The PCH is required to be 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] Let us explain about HARQ. HARQ is a technology that improves the communication quality of a transmission line by combining Automatic Repeat reQuest (ARQ) and Forward Error Correction. HARQ has the advantage that error correction works effectively by retransmission even for transmission lines whose communication quality changes. In particular, it is possible to obtain further quality improvement by combining the reception result of the initial transmission and the reception result of the retransmission when retransmitting.

[0023] An example of a retransmission method will be described below. If the received data cannot be decoded correctly on the receiving side, in other words, if a CRC (Cyclic Redundancy Check) error occurs (CRC=NG), the receiving side will send a "Nack" to the transmitting side. The transmitting side that receives the "Nack" will retransmit the data. If the received data can be decoded correctly on the receiving side, in other words, if no CRC error occurs (CRC=OK), the receiving side will send an "Ack" to the transmitting side. The transmitting side that receives the "Ack" will send the next data.

[0024] The logical channel described in Non-Patent Document 1 (Chapter 6) will be explained. The Broadcast Control Channel (BCCH) is a downlink channel for broadcast system control information. The logical channel BCCH 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 transport channel, the Downlink Shared Channel (DL-SCH). In the uplink direction, CCCH is mapped to a transport channel, the Uplink Shared Channel (UL-SCH).

[0027] The Multicast Control Channel (MCCH) is a downlink channel for point-to-multipoint transmission. The MCCH is used for transmission of 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. DCCH is used when a communication terminal is in an RRC connection. 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. DTCH is mapped to an uplink shared channel (UL-SCH) in uplink and to a downlink shared channel (DL-SCH) in downlink.

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

[0031] CGI stands for Cell Global Identifier. ECGI stands for E-UTRAN Cell Global Identifier. CSG (Closed Subscriber Group) 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 for tracking the location of this communication terminal is called a tracking area.

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

[0034] In the LTE-A system, in order to support wider frequency bandwidths (transmission bandwidths) up to 100 MHz, Carrier Aggregation (CA) is being considered, which aggregates two or more Component Carriers (CCs) (also called "aggregation"). 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 a 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 set of serving cells 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] New technologies for LTE-A include a technology that supports wider bandwidth (Wider Bandwidth Extension) and a 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] In addition, in 3GPP, in order to handle the huge traffic in the future, the use of small eNBs (hereinafter sometimes referred to as "small-scale base station devices") that configure small cells is being considered. For example, technologies are being considered that improve frequency utilization efficiency and increase communication capacity by installing many small eNBs and configuring many small cells. 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 performing 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 is on the rise, and communication speeds are also getting faster. Once LTE and LTE-A are fully operational, communication speeds are expected to become even faster.

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

[0043] Compared to the LTE system, the 5G wireless access system requires a system capacity that is 1,000 times greater, a data transmission speed that is 100 times greater, data processing delay that is one-tenth (1 / 10), and 100 times the number of simultaneous connections of communication terminals, while also achieving further reductions in power consumption and reductions in equipment costs.

[0044] In order to meet such demands, 3GPP is currently working on 5G standards as Release 15 (see Non-Patent Documents 6 to 18). The technology for 5G wireless sections 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 for the downlink and OFDM and DFT-s-OFDM (DFT-spread-OFDM) for the uplink.

[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] In the NR frame configuration, various subcarrier intervals, i.e., various numerologies, are supported. In NR, regardless of the numerology, one subframe is 1 millisecond, and one slot is composed of 14 symbols. In addition, the number of slots included in one subframe is one in a numerology with a subcarrier interval of 15 kHz, and increases in proportion to the subcarrier interval in other numerologies (see Non-Patent Document 13 (TS38.211 V15.2.0)).

[0050] In NR, downlink synchronization signals are transmitted from base stations as synchronization signal bursts (hereinafter sometimes referred to as SS bursts) at a predetermined cycle with a predetermined duration. An SS burst is composed 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 by changing the beam. An SS block is composed 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 in the same way as in the downlink.

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

[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 that BWP, thereby reducing power consumption in the UE.

[0054] In 3GPP, the following DC forms are being considered: DC by LTE base stations and NR base stations connected to the EPC, DC by NR base stations connected to the 5G core system, and DC by LTE base stations and NR base stations connected to the 5G core system (see non-patent documents 12, 16, and 19).

[0055] In addition, 3GPP is considering several new technologies. For example, it is considering supporting services using side link (SL) communication in both EPS and 5G core systems (Non-Patent Documents 1, 20, 21, 22). 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 V15.7.0 [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 V15.0.0 [Non-Patent Document 5] "Scenarios, requirements and KPIs for 5G mobile and wireless system", ICT-317669-METIS / D1.1

Non-licensed Document 6

Non-licensed Document 7

Non-licensed Document 8

Non-licensed literature 9

Non-licensed literature 10

Non-licensed Document 11

Non-licensed Document 12

Non-licensed Document 13

Non-licensed Document 14

Non-licensed Document 15

Non-licensed Document 16

Non-licensed Document 17

Non-licensed Document 18

Non-licensed Document 19

Non-licensed Document 20

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 (Non-Patent Documents 1, 20, 21, 22). In SL communication, communication is performed between terminals. In SL communication, it has been proposed that a terminal other than the terminal performing the terminal-to-terminal communication performs SL communication scheduling (Non-Patent Document 23). In SL communication, in addition to direct communication between terminals, indirect communication via a relay has also been proposed (Non-Patent Document 24). In SL communication using not only terminals performing such SL communication but also other terminals, the problem is how to satisfy the QoS required for the service and how to improve the reliability of the service.

[0058] In view of the above-mentioned problems, one of the objects of the present disclosure is to provide a technique for ensuring the QoS required for a service and improving the reliability of the service in SL communication. [Means for solving the problem]

[0059] A first communication terminal device of the present disclosure is a first communication terminal device that communicates with a second communication terminal device, the first communication terminal device having a control unit and a transceiver, the first communication terminal device communicating directly with a base station device, the second communication terminal device communicating with the base station device via the first communication terminal device, the control unit using the transceiver to transmit a request for a policy for communicating with the second communication terminal device in sidelink communication to a core network, receiving the policy from the base station device using the transceiver, and using the policy to communicate with the second communication terminal device in the sidelink communication.

[0060] A second communication terminal device of the present disclosure is a second communication terminal device that communicates with a first communication terminal device, the second communication terminal device having a control unit and a transceiver, the first communication terminal device communicating directly with a base station device, the second communication terminal device communicating with the base station device via the first communication terminal device, the control unit using the transceiver to transmit a request for a policy for communicating with the first communication terminal device in sidelink communication to a core network, receiving the policy from the base station device using the transceiver, and using the policy to communicate with the first communication terminal device in the sidelink communication.

[0061] The base station device of the present disclosure is a base station device that is directly connected to a first communication terminal device and connected to a second communication terminal device via the first communication terminal device, the base station device having a control unit and a transceiver, the control unit transmits the policy to the first communication terminal device using the transceiver in response to a core network receiving from the first communication terminal device a request for a policy for communicating with the second communication terminal device in sidelink communication, the policy being used by the first communication terminal device to communicate with the second communication terminal device in the sidelink communication.

[0062] The communication system of the present disclosure includes a base station device, a first communication terminal device, and a second communication terminal device, wherein the first communication terminal device communicates directly with the base station device, the second communication terminal device communicates with the base station device via the first communication terminal device, the first communication terminal device transmits a request to a core network for a policy for communicating with the second communication terminal device in sidelink communication, the base station device transmits the policy to the first communication terminal device in response to the core network receiving the request, the first communication terminal device receives the policy from the base station device, and the first communication terminal device uses the policy to communicate with the second communication terminal device in the sidelink communication. The communication system of the present disclosure includes a base station device, a first communication terminal device, and a second communication terminal device, wherein the first communication terminal device communicates directly with the base station device, the second communication terminal device communicates with the base station device via the first communication terminal device, the second communication terminal device transmits a request to a core network for a policy for communicating with the first communication terminal device in sidelink communication, the base station device transmits the policy to the second communication terminal device in response to the core network receiving the request, the second communication terminal device receives the policy from the base station device, and the second communication terminal device uses the policy to communicate with the first communication terminal device in the sidelink communication. Effect of the Invention

[0063] According to the present disclosure, in SL communication, it is possible to ensure the QoS required for the service and improve the reliability of the service.

[0064] The objects, features, aspects, and advantages of the present disclosure will become more apparent from the following detailed description and the accompanying drawings. [Brief description of the drawings]

[0065] [Figure 1] FIG. 1 is an explanatory diagram showing the configuration of a radio frame used in an LTE communication system. [Diagram 2]1 is a block diagram showing the overall configuration of a communication system 200 based on the LTE standard that is being discussed in 3GPP. [Diagram 3] FIG. 2 is a block diagram showing the overall configuration of a communication system 210 of the NR standard being discussed in 3GPP. [Figure 4] FIG. 1 is a diagram illustrating a DC configuration using eNBs and gNBs connected to an EPC. [Diagram 5] This is a diagram of the DC configuration using gNB connected to the NG core. [Figure 6] This is a diagram showing the configuration of DC using eNBs and gNBs connected to the NG core. [Figure 7] This is a diagram showing the configuration of DC using eNBs and gNBs connected to the NG core. [Figure 8] FIG. 3 is a block diagram showing a configuration of a mobile terminal 202 shown in FIG. [Figure 9] FIG. 3 is a block diagram showing a configuration of a base station 203 shown in FIG. [Figure 10] FIG. 2 is a block diagram showing the configuration of an MME. [Figure 11] A block diagram showing the configuration of 5GC. [Figure 12] 1 is a flowchart showing an overview of operations from cell search to standby performed by a communication terminal (UE) in an LTE communication system. [Figure 13] FIG. 1 is a diagram showing an example of a cell configuration in an NR system. [Figure 14] A sequence diagram showing an example in which a gNB performs scheduling for SL communication between UEs in embodiment 1. [Figure 15] A sequence diagram showing an example in which a gNB performs scheduling for SL communication between UEs in embodiment 1. [Figure 16] FIG. 11 is a sequence diagram showing an example in which an S-UE performs scheduling for SL communication with other UEs, in accordance with a first variant of the first embodiment. [Figure 17] FIG. 11 is a sequence diagram showing an example in which an S-UE performs scheduling for SL communication with other UEs, in accordance with a first variant of the first embodiment. [Figure 18] FIG. 11 is a sequence diagram showing an example in which an S-UE performs scheduling for SL communication with other UEs, in accordance with a second variant of the first embodiment. [Figure 19] FIG. 11 is a sequence diagram showing an example in which an S-UE performs scheduling for SL communication with other UEs, in accordance with a second variant of the first embodiment. [Figure 20] FIG. 11 is a sequence diagram showing an example in which an S-UE performs scheduling for SL communication with other UEs, in accordance with a third variant of the first embodiment. [Figure 21] FIG. 11 is a diagram illustrating an example of a preemption process by an S-UE in accordance with the second embodiment. [Figure 22] FIG. 11 is a diagram illustrating an example of a method of transmitting a PI from UE-TX1 to UE-RX1 in accordance with the second embodiment. [Diagram 23] FIG. 11 is a diagram illustrating an example of a method of transmitting a PI from UE-TX1 to UE-RX1, in accordance with the first modification of the second embodiment. [Figure 24] FIG. 1 is a conceptual diagram showing a conventional example in which unicast communication is performed between UE-TX and UE-RX via a relay UE. [Diagram 25] FIG. 11 is a conceptual diagram showing an example of performing groupcast communication between UE-TX and multiple UE-RX via a relay UE, in accordance with a third embodiment. [Figure 26] FIG. 11 is a sequence diagram showing an example of performing groupcast communication between UE-TX and a plurality of UE-RX via a relay UE, in accordance with the third embodiment. [Figure 27] FIG. 11 is a sequence diagram showing an example of performing groupcast communication between UE-TX and a plurality of UE-RX via a relay UE, in accordance with the third embodiment. [Figure 28] FIG. 11 is a sequence diagram showing another example of performing group cast communication between UE-TX and a plurality of UE-RX via a relay UE, in accordance with the third embodiment. [Figure 29] FIG. 13 is a conceptual diagram showing an example of performing groupcast communication between UE-TX and multiple UE-RX via a relay UE, in accordance with a first modification of the third embodiment. [Diagram 30] FIG. 13 is a sequence diagram showing an example of performing group cast communication between UE-TX and a plurality of UE-RX via a relay UE, in accordance with the first modification of the third embodiment. [Diagram 31] FIG. 13 is a sequence diagram showing an example of performing group cast communication between UE-TX and a plurality of UE-RX via a relay UE, in accordance with the first modification of the third embodiment. [Diagram 32] FIG. 13 is a sequence diagram showing another example of performing group cast communication between UE-TX and a plurality of UE-RX via a relay UE, in accordance with the first modification of the third embodiment. [Diagram 33] FIG. 13 is a sequence diagram showing another example of performing group cast communication between UE-TX and a plurality of UE-RX via a relay UE, in accordance with the first modification of the third embodiment. [Diagram 34] FIG. 13 is a conceptual diagram showing an example of performing groupcast communication between UE-TX and multiple UE-RX via a relay UE, in accordance with a second modification of the third embodiment. [Diagram 35] FIG. 13 is a sequence diagram showing an example of performing groupcast communication between UE-TX and a plurality of UE-RX via a relay UE, in accordance with a second modification of the third embodiment. [Diagram 36] FIG. 13 is a diagram illustrating an example of a protocol configuration of each node when indirect communication between UEs is performed via a relay UE in SL, in accordance with the fourth embodiment. [Figure 37] FIG. 11 is a diagram showing an example of a fourth embodiment in which, in a relay UE, an RLC bearer setup between UE-TX and the relay UE is the same as an RLC bearer setup between the relay UE and UE-RX. [Figure 38] FIG. 13 is a diagram showing another example of the protocol configuration of each node when performing indirect communication between UEs via a relay UE in SL, according to the fourth embodiment. [Figure 39] FIG. 13 is a conceptual diagram showing packet duplication when indirect communication is performed via a relay UE in SL communication, according to the first modification of the fourth embodiment. [Diagram 40]FIG. 11 is a diagram illustrating an example of a protocol configuration for packet duplication when indirect communication is performed via a relay UE in SL communication, in accordance with a first modification of the fourth embodiment. [Diagram 41] FIG. 11 is a diagram showing another example of a protocol configuration for packet duplication when indirect communication is performed via a relay UE in SL communication, in accordance with the first modification of the fourth embodiment. [Diagram 42] FIG. 11 is a conceptual diagram of an example in which a relay UE concatenates and relays data in SL communication, according to a second modification of the fourth embodiment. [Diagram 43] FIG. 11 is a diagram showing a first example of a protocol configuration for a relay UE to concatenate and relay data in SL communication, in accordance with a second variant of the fourth embodiment. [Diagram 44] FIG. 11 is a diagram showing a second example of a protocol configuration for a relay UE to concatenate and relay data in SL communication, according to a second modification of the fourth embodiment. [Diagram 45] FIG. 11 is a diagram showing a third example of a protocol configuration for a relay UE to concatenate and relay data in SL communication, in accordance with the second modification of the fourth embodiment. [Figure 46] FIG. 13 is a diagram showing an example in which a plurality of system information area IDs are set for one cell in accordance with the fifth embodiment. [Figure 47] This figure shows an example of embodiment 5 in which multiple SIBs are provided in one SIB containing the same type of information, with one or more pieces of information being different within the SIB. [Figure 48] FIG. 13 is a diagram showing a first example in which different information is set for each system information area ID in one SIB, in accordance with the fifth embodiment. [Figure 49] FIG. 13 is a diagram showing a second example in which different information is set for each system information area ID in one SIB, in accordance with the fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0066] Embodiment 1 Fig. 2 is a block diagram showing the overall configuration of an LTE-based 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.

[0067] Here, the term "communication terminal device" includes not only mobile terminal devices such as mobile mobile phone terminal devices, but also stationary devices such as sensors. In the following description, the "communication terminal device" may be simply referred to as a "communication terminal."

[0068] 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 in a base station 203, E-UTRAN is composed of one or more base stations 203.

[0069] A control protocol RRC (Radio Resource Control) between the mobile terminal 202 and the base station 203 performs broadcast, 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.

[0070] In RRC_IDLE, PLMN (Public Land Mobile Network) selection, System Information (SI) broadcast, paging, cell re-selection, 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.

[0071] The base station 203 is composed of one or more eNBs 207. A system composed of 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 called a "network."

[0072] The eNB207 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 eNB207 and the MME unit 204. A plurality of MME units 204 may be connected to one eNB207. The eNBs 207 are connected to each other via an X2 interface, and control information is communicated between the eNBs 207.

[0073] The MME unit 204 is an upper device, specifically an upper node, and controls a 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.

[0074] The base station 203 may configure one cell or multiple cells. Each cell has a predetermined range as a coverage area in which communication with the mobile terminal 202 is possible, and performs wireless communication with the mobile terminal 202 within the coverage area. When one base station 203 configures multiple cells, each cell is configured to be able to communicate with the mobile terminal 202.

[0075] FIG. 3 is a block diagram showing the overall configuration of a 5G communication system 210 being discussed in 3GPP. FIG. 3 will be described. The radio access network is called NG-RAN (Next Generation Radio Access Network) 211. The UE 202 is capable of wireless communication with an NR base station device (hereinafter referred to as "NR base station (NG-RAN NodeB: gNB)") 213, and transmits and receives signals via wireless communication. The core network is called 5G Core (5G Core: 5GC).

[0076] If control protocols for UE202, such as RRC (Radio Resource Control), and user plane (hereinafter sometimes referred to as U-Plane), 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 the NR base station 213, the NG-RAN is composed of one or more NR base stations 213.

[0077] The function of the control protocol RRC (Radio Resource Control) between the UE 202 and the NR base station 213 is similar to 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.

[0078] RRC_IDLE and RRC_CONNECTED are the same as those in the LTE system. In RRC_INACTIVE, the connection between the 5G core and the NR base station 213 is maintained, and system information (SI) is reported, paging, cell re-selection, mobility, and the like are performed.

[0079] The gNB 217 is connected to an AMF / SMF / UPF unit (hereinafter sometimes referred to as a "5GC unit") 214 including 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. A plurality of 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.

[0080] 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 of the cells is configured to be capable of communicating with the UE 202.

[0081] The gNB 217 may be divided into a central unit (hereinafter, sometimes referred to as CU) 218 ​​and a distributed unit (hereinafter, sometimes referred to as DU) 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 by an F1 interface, and control information and / or user data are communicated between the CU 218 and the DU 219.

[0082] In a 5G communication system, a Unified Data Management (UDM) function and a Policy Control Function (PCF) described in Non-Patent Document 22 (3GPP TS23.501 V16.1.0) may be included. The UDM and / or PCF may be included in the 5GC unit in FIG.

[0083] A 5G communication system may include a non-3GPP interworking function (N3IWF) described in non-patent document 22 (3GPP TS23.501 V16.1.0). The N3IWF may terminate an access network (AN) between the UE and the N3IWF in non-3GPP access between the UE and the N3IWF.

[0084] FIG. 4 is a diagram showing a configuration of DC by eNB and gNB connected to EPC. In FIG. 4, solid lines indicate U-Plane connections, and dashed lines indicate C-Plane connections. In FIG. 4, eNB223-1 is a master base station, and gNB224-2 is a secondary base station (this DC configuration may be referred to as EN-DC). In FIG. 4, an example is shown 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.

[0085] FIG. 5 is a diagram showing a DC configuration by a gNB connected to an NG core. In FIG. 5, a solid line indicates a U-Plane connection, and a dashed line indicates a C-Plane connection. In FIG. 5, gNB 224-1 is a master base station, and gNB 224-2 is a secondary base station (this DC configuration may be referred to as NR-DC). In FIG. 5, an example is shown in which a U-Plane connection between 5GC unit 214 and gNB 224-2 is made via gNB 224-1, but it may be made directly between 5GC unit 214 and gNB 224-2.

[0086] FIG. 6 is a diagram showing a configuration of DC by eNB and gNB connected to the NG core. In FIG. 6, a solid line indicates a U-Plane connection, and a dashed line indicates a C-Plane connection. In FIG. 6, eNB226-1 becomes a master base station, and gNB224-2 becomes a secondary base station (this DC configuration may be referred to as NG-EN-DC). In FIG. 6, an example is shown in which U-Plane connection between 5GC unit 214 and gNB224-2 is made via eNB226-1, but it may be made directly between 5GC unit 214 and gNB224-2.

[0087] FIG. 7 is a diagram showing another configuration of DC by eNB and gNB connected to the NG core. In FIG. 7, solid lines indicate U-Plane connections, and dashed lines indicate C-Plane connections. In FIG. 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). In FIG. 7, an example is shown in which U-Plane connection between 5GC unit 214 and eNB226-2 is made via gNB224-1, but it may be made directly between 5GC unit 214 and eNB226-2.

[0088] FIG. 8 is a block diagram showing the configuration of the mobile terminal 202 shown in FIG. 2. The transmission process of the mobile terminal 202 shown in FIG. 8 will be described. First, the control data from the protocol processing unit 301 and the user data from the application unit 302 are stored in the transmission data buffer unit 303. The data stored in the transmission data buffer unit 303 is passed to the encoder unit 304, where encoding such as error correction is performed. There may be data that is directly output from the transmission data buffer unit 303 to the modulation unit 305 without encoding. The data that has been encoded by the encoder unit 304 is modulated by the modulation unit 305. Precoding in MIMO may be performed by the modulation unit 305. The modulated data is converted into a baseband signal, and then output to the frequency conversion unit 306, where it is converted into a radio transmission frequency. Thereafter, a transmission signal is transmitted from the antennas 307-1 to 307-4 to the base station 203. Although the case where the number of antennas is four is illustrated in FIG. 8, the number of antennas is not limited to four.

[0089] Moreover, the reception process of the mobile terminal 202 is executed as follows. Radio signals from the base station 203 are received by the antennas 307-1 to 307-4. The received signal is converted from a radio reception frequency to a baseband signal by the frequency conversion unit 306, and demodulated by the demodulation unit 308. The demodulation unit 308 may perform weight calculation and multiplication. The demodulated data is passed to the decoder unit 309, where decoding such as error correction is performed. Of the decoded data, the control data is passed to the protocol processing unit 301, and the user data is passed to the application unit 302. A series of processes of the mobile terminal 202 is controlled by the control unit 310. Therefore, although the 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 the mobile terminal 202 for transmission and the number of antennas used for reception may be the same or different.

[0090] FIG. 9 is a block diagram showing the configuration of the base station 203 shown in FIG. 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 between the base station 203 and the 5GC. The EPC communication unit 401, the 5GC communication unit 412, and the other base station communication unit 402 each transmit and receive information to and from 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.

[0091] The data stored in the transmission data buffer unit 404 is passed to the encoder unit 405, where it is subjected to encoding such as error correction. There may be data that is directly output from the transmission data buffer unit 404 to the modulation unit 406 without being subjected to encoding. The encoded data is modulated by the modulation unit 406. The modulation unit 406 may perform precoding in MIMO. The modulated data is converted into a baseband signal, and then output to the 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 the antennas 408-1 to 408-4. Although the case where the number of antennas is four is illustrated in FIG. 9, the number of antennas is not limited to four.

[0092] The reception process of the base station 203 is executed as follows. A radio signal from one or more mobile terminals 202 is received by the antenna 408. The received signal is converted from a radio reception frequency to a baseband signal by the frequency conversion unit 407, and demodulated by the demodulation unit 409. The demodulated data is passed to the decoder unit 410, where decoding such as error correction is performed. Of the decoded data, the control data is passed to the protocol processing unit 403 or the 5GC communication unit 412 or the EPC communication unit 401 and the other base station communication unit 402, and the 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 the 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 by the base station 203 for transmission and the number of antennas used for reception may be the same or different.

[0093] Fig. 9 is a block diagram showing the configuration of base station 203, but base station 213 may have a similar configuration. In addition, in Fig. 8 and Fig. 9, the number of antennas of mobile terminal 202 and the number of antennas of base station 203 may be the same or different.

[0094] FIG. 10 is a block diagram showing the configuration of an MME. FIG. 10 shows the configuration of the MME 204a included in the MME unit 204 shown in FIG. 2 described above. The PDN GW communication unit 501 transmits and receives data between the MME 204a and the PDN GW. The base station communication unit 502 transmits and receives data between the MME 204a and the base station 203 via the S1 interface. 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 the 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.

[0095] When 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. When 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.

[0096] 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 general processing for the control plane (hereinafter, sometimes referred to as 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 called the LTE-IDLE state or simply idle), generation and control of paging signals in the idle state, addition, deletion, update, search, and tracking area list management of one or more mobile terminals 202 under its control.

[0097] The MME 204a distributes a paging signal 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 a mobile terminal is in an idle state and in an active state. The MME 204a initiates a paging protocol by transmitting a paging message to a cell that belongs 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.

[0098] 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 the case where the 5GC unit 214 shown in FIG. 5 includes the AMF configuration, the SMF configuration, and the 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 is 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.

[0099] 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 control 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.

[0100] 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 general processing for the control plane (hereinafter, sometimes referred to as 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 a standby state (also called an idle state; RRC_IDLE state, or simply idle), generation and control of paging signals in a standby state, addition, deletion, update, search, tracking area list management, etc. of one or more mobile terminals 202 under its umbrella.

[0101] 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, and 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.

[0102] Next, an example of a cell search method in a communication system is shown. Fig. 12 is a flow chart showing an outline of a 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, the communication terminal 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.

[0103] 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.

[0104] 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. A code that has a one-to-one correspondence with the PCI is used for the reference signal (RS). By correlating with the 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.

[0105] 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 among one or more cells detected up to step ST602.

[0106] Next, in step ST604, the PBCH of the best cell is received to obtain a 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 DL (downlink) system bandwidth (also called transmission bandwidth configuration: dl-bandwidth), the number of transmitting antennas, SFN (System Frame Number), and the like.

[0107] 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 in the broadcast information BCCH is obtained. SIB 1 includes information on access to the cell, information on cell selection, and scheduling information of other SIBs (SIBk; k is an integer ≧2). SIB 1 also includes a tracking area code (TAC).

[0108] 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 a 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 code number of the tracking area.

[0109] If the TAC received in step ST605 is the same as the TAC included in the tracking area list as a result of the comparison in step ST606, the communication terminal enters standby mode in the cell. If the TAC received in step ST605 is not included in the tracking area list as a result of the comparison, 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.

[0110] 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.

[0111] An apparatus constituting a core network (hereinafter sometimes referred to as a "core network side apparatus") updates the tracking area list based on an identification number (such as a UE-ID) of a 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. After that, the communication terminal enters standby mode in the cell.

[0112] The spread of smartphones and tablet terminal devices has led to an explosive increase in traffic via cellular wireless communications, raising concerns about a shortage of wireless resources around the world. In response to this, efforts are being made to create smaller cells and promote spatial separation in order to improve frequency utilization efficiency.

[0113] In a conventional cell configuration, a cell configured by an eNB has a relatively wide coverage area. Conventionally, a cell is configured to cover a certain area by the relatively wide coverage areas of a plurality of cells configured by a plurality of eNBs.

[0114] In the case of small cell configuration, the cell configured by the eNB has a narrower coverage range than the coverage of the cell configured by the conventional eNB. Therefore, as in the past, in order to cover a certain area, a large number of small cell eNBs are required compared to the conventional eNBs.

[0115] 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 that has been made into 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."

[0116] The macro eNB may be, for example, a “Wide Area Base Station” as described in Non-Patent Document 7.

[0117] 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.

[0118] FIG. 13 shows an example of a cell configuration in NR. In an NR cell, a narrow beam is formed and transmitted while changing the direction. In the example shown in FIG. 13, at a certain time, the base station 750 transmits and receives with a mobile terminal using a beam 751-1. At another time, the base station 750 transmits and receives with a mobile terminal using a beam 751-2. In the same manner, the base station 750 transmits and receives with a mobile terminal using one or more of the beams 751-3 to 751-8. In this way, the base station 750 configures a wide-range cell.

[0119] 13 shows an example in which the number of beams used by the base station 750 is eight, but the number of beams may be different from eight. Also, in the example shown in FIG. 13, the number of beams used simultaneously by the base station 750 is one, but it may be multiple.

[0120] In 3GPP, Side Link (SL) is supported for D2D (Device to Device) communication and V2V (Vehicle to Vehicle) communication (see Non-Patent Document 1). SL is defined by the PC5 interface.

[0121] 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 the UE.

[0122] The physical sidelink discovery channel (PSDCH) carries sidelink discovery messages from the UE.

[0123] The physical sidelink control channel (PSCCH) carries control information from the UE for sidelink and V2X sidelink communications.

[0124] The physical sidelink shared channel (PSSCH) carries data from the UE for sidelink and V2X sidelink communications.

[0125] The transport channel used for SL (see Non-Patent Document 1) will be described below. A sidelink broadcast channel (SL-BCH) has a predetermined transport format, and is mapped to the PSBCH, which is a physical channel.

[0126] The Sidelink discovery channel (SL-DCH) has periodic broadcast transmissions of a fixed size and a predefined format. The SL-DCH supports both UE autonomous resource selection and eNB scheduled resource allocation. There is a collision risk with UE automatic resource selection, and there is no collision when the UE is allocated dedicated resources by the eNB. The SL-DCH supports HARQ combining but not HARQ feedback. The SL-DCH is mapped to the PSDCH, which is a physical channel.

[0127] The Sidelink Shared Channel (SL-SCH) supports broadcast transmission. The SL-SCH supports both UE autonomous resource selection and eNB scheduled resource allocation. There is a collision risk with UE automatic resource selection, and there is no collision when the UE is allocated dedicated resources by the eNB. The SL-SCH also supports HARQ combining but does not support HARQ feedback. The SL-SCH also supports dynamic link adaptation by changing the transmit power, modulation and coding. The SL-SCH is mapped to the PSSCH, which is a physical channel.

[0128] The logical channels used for SL (see Non-Patent Document 1) will be described. The Sidelink Broadcast Control Channel (SBCCH) is a channel for sidelink to broadcast sidelink system information from one UE to other UE. The SBCCH is mapped to the SL-BCH, which is a transport channel.

[0129] The Sidelink Traffic Channel (STCH) is a one-to-many sidelink 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, which is a transport channel.

[0130] 3GPP is considering supporting V2X communication in NR as well. The study of V2X communication in NR is proceeding 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.

[0131] 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 21 (TS23.287)).

[0132] For unicast and groupcast communications, support for HARQ feedback (Ack / Nack), CSI reporting, etc. is being considered.

[0133] 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 21 (TS23.287)). For example, PC5-S signaling is implemented to establish a link for implementing SL, i.e., PC5 communication. The link is implemented in the V2X layer and is also called a Layer 2 link.

[0134] Also, support for RRC signaling in SL communication is being considered (see Non-Patent Document 21 (TS23.287)). RRC signaling in SL communication is also called 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 performing V2X communication using PC5 communication.

[0135] Conventionally, in sidelink communication (SL communication), scheduling for SL communication between a transmitting UE (referred to as UE-TX) and a receiving UE (referred to as UE-RX) is performed by a gNB serving the UE-TX or by the UE-TX itself. The mode in which the gNB serving the UE-TX performs the scheduling is called mode-1, and the mode in which the UE-TX performs the scheduling is called mode-2 (see Non-Patent Document 23).

[0136] For example, in a V2X service using SL communication, there are cases where the gNB performs scheduling for SL communication and cases where the UE-TX itself performs scheduling. When the gNB performs scheduling for SL communication, the V2X policy / parameters of the V2X service performed between the UE-TX and the UE-RX using SL communication are provided from the CN to the gNB in ​​response to a V2X policy provision request from the UE-TX to the CN (see Non-Patent Document 21). Also, when the UE-TX itself performs scheduling, the V2X policy / parameters are provided from the CN to the UE-TX in response to a V2X policy provision request from the UE-TX to the CN (see Non-Patent Document 21).

[0137] 3GPP has proposed to subdivide mode-2, which is a method in which the UE-TX itself performs scheduling. As a method of subdivision, it has been proposed that the UE selects resources for SL communication of other UEs (mode-2(b)), and that the UE performs scheduling for SL communication of other UEs (mode-2(d)) (see Non-Patent Document 23).

[0138] In the case of methods such as mode-2(b) and mode-2(d), the UE that performs resource selection and scheduling (hereinafter referred to as a scheduling UE (S-UE)) needs to recognize the V2X policy / parameters between UE-TX and UE-RX that actually perform the V2X service using SL communication. However, since the S-UE is neither a gNB nor a UE that actually performs SL communication for the V2X service, the V2X policy / parameters are not provided to the S-UE in the conventional method.

[0139] This causes a problem that the S-UE cannot perform scheduling suitable for the V2X policy / parameters of the SL communication between the UE-TX and the UE-RX, and the QoS required for the V2X service performed between the UE-TX and the UE-RX is not satisfied.

[0140] In the first embodiment, a method for solving such a problem will be disclosed.

[0141] The UE-TX performs a V2X policy / parameter providing process to the CN in advance via a RAN node such as a gNB. In the V2X policy / parameter providing process, the UE-TX requests the CN to provide the V2X policy / parameter via the gNB. The CN that receives the request provides the V2X policy / parameter to the gNB. The CN that receives the request may provide the V2X policy / parameter to the UE-TX. The V2X policy or V2X parameter may be, for example, a V2X policy or V2X parameter on the PC5 (also referred to as a PC5 reference point). The V2X parameter may be a QoS parameter or the like.

[0142] The CN node may be a PCF. The PCF may provide the V2X policy / parameters to the gNB via the AMF. Alternatively, the CN node may be an AMF. This is effective in the case where the AMF stores the V2X policy / parameters of the UE-TX acquired from the PCF in advance.

[0143] When the UE-TX is under the control of the gNB, the UE-TX may perform a V2X policy / parameter provision process. The gNB may acquire V2X policies / parameters of multiple UE-TXs under its control. This allows the gNB to acquire the V2X policies / parameters of the UE-TX from the CN.

[0144] The gNB may store the V2X policy / parameter of the UE-TX acquired from the CN. The gNB may store the V2X policy / parameter in association with the identifier of the UE-TX and / or information for identifying the V2X service. The gNB becomes able to recognize which UE-TX and which V2X service the V2X policy / parameter belongs to.

[0145] The gNB performs scheduling for SL communication for the UE-TX. In this specification, resource selection and / or scheduling may be simply referred to as scheduling.

[0146] This paper discloses a method in which the gNB performs scheduling for SL communication on the UE-TX. When SL communication occurs, the UE-TX is connected to the S-UE and is not directly connected to the gNB. Therefore, how the gNB performs scheduling on the UE-TX becomes an issue. This paper discloses a method in which the gNB performs scheduling for SL communication on the UE-TX.

[0147] The UE-TX transmits a scheduling request for SL communication to the S-UE. When the S-UE receives a scheduling request for SL communication from the UE-TX, the S-UE may determine whether the S-UE can connect to the gNB or is currently connected. For example, when the S-UE is within the coverage of the gNB, the S-UE can connect to the gNB or is currently connected. When the S-UE is outside the coverage of the gNB, the S-UE is not connected to the gNB and cannot connect. When the S-UE can connect to the gNB, the S-UE performs a connection process with the gNB and transmits a scheduling request for SL communication of the UE-TX to the gNB. When the S-UE is connected to the gNB, the S-UE transmits a scheduling request for SL communication of the UE-TX to the gNB. The connection state may be an RRC connection.

[0148] When the S-UE is not connected to the gNB and cannot be connected, the S-UE may perform SL communication scheduling for the UE-TX. For this method, for example, the method disclosed in the second modification of the first embodiment or the third modification of the first embodiment may be applied.

[0149] The gNB that receives a scheduling request for SL communication of the UE-TX from the S-UE performs scheduling for SL communication for the UE-TX. At this time, the gNB may use the V2X policy / parameter of the UE-TX acquired from the CN and recorded in the gNB. By performing SL scheduling using the V2X policy / parameter of the UE-TX, it becomes possible to perform SL scheduling so as to satisfy the QoS required for the V2X service that the UE-TX performs using SL communication.

[0150] The gNB notifies the UE-TX of the SL communication scheduling information for the UE-TX via the S-UE. The UE-TX performs SL communication between the UE-TX and the UE-RX using the SL communication scheduling information received via the S-UE. In this way, the gNB that is not directly connected to the UE-TX can perform SL communication scheduling for the UE-TX.

[0151] The following (1) to (10) are disclosed as specific examples of information to be included in the scheduling request notified from the UE-TX to the S-UE.

[0152] (1) Information indicating that this is a scheduling request.

[0153] (2) Information for identifying the source UE.

[0154] (3) Information for identifying the destination UE.

[0155] (4) V2X capability.

[0156] (5) V2X service information.

[0157] (6) Application layer information.

[0158] (7)PC5 link information.

[0159] (8)PC5 QoS Flow information.

[0160] (9) SL bearer information.

[0161] (10) A combination of (1) to (9) above.

[0162] The information (1) may be, for example, information indicating that the information is a request for resource allocation or scheduling for SL communication performed by the UE-TX.

[0163] The information (2) may be, for example, a UE identifier. The information (2) may be a layer 2 ID (L2 ID) used by the UE-TX in SL communication. This allows the S-UE to recognize which UE-TX has made the scheduling request.

[0164] The information (3) may be, for example, a UE identifier. The information (3) may be a layer 2 ID (L2 ID) used by a UE-RX that performs SL communication with a UE-TX. This allows the S-UE to recognize which UE-RX the scheduling request is for SL communication with.

[0165] The information (4) may be, for example, information on whether the UE-TX has V2X capability. The information (4) may be information on whether the UE-TX has PC5 capability. The S-UE can recognize whether the UE-TX is capable of SL communication.

[0166] The information in (5) may be, for example, a V2X service identifier. The information in (5) may be a provider service identifier (PSID) or an intelligent transport systems application identifier (ITS-AID). This allows the S-UE to recognize which V2X service the scheduling request is for.

[0167] The information (6) may be, for example, an application layer identifier. The information (6) may be an identifier corresponding to an object in which the UE-TX is mounted. The object in which the UE-TX is mounted may be, for example, a car, a pedestrian, etc. An identifier for identifying the object in which the UE-TX is mounted may be used as an identifier for identifying the UE-TX. This enables the S-UE to recognize which application the scheduling request is for.

[0168] The information in (7) may be, for example, a PC5 link identifier. The information in (7) may be a PC5 link identifier assigned by the UE-TX to perform SL communication. If the SL communication to be performed is unicast communication, the information in (7) may be a PC5 unicast link identifier. This allows the S-UE to recognize which PC5 link the scheduling request is for.

[0169] The information (8) may be, for example, a PC5 QoS Flow identifier, which enables the S-UE to recognize which PC5 QoS Flow the scheduling request is for.

[0170] The information (9) may be, for example, the ID of a bearer used in SL communication between UE-TX and UE-RX. The ID of the bearer may be the ID of a DRB or the ID of an SRB. This allows the S-UE to recognize which SL bearer the scheduling request is for.

[0171] A signaling indicating a scheduling request may be newly provided on the PC5 link. By distinguishing this signaling from other signaling, it is possible to reduce reception errors at the S-UE.

[0172] A method of transmitting a scheduling request from UE-TX to S-UE is disclosed. A PC5 link (higher layer link) is established in advance between UE-TX and S-UE. Alternatively, UE-TX may establish a PC5 link with S-UE when a V2X service using SL communication occurs. Alternatively, UE-TX may establish a PC5 link with S-UE when a PC5 link for a V2X service using SL communication is established with UE-RX.

[0173] The UE-TX may transmit a scheduling request to the S-UE using the signaling at the time of the PC5 link establishment. The S-UE can receive the scheduling request from the UE-TX early and can transmit the scheduling request received from the UE-TX to the gNB early.

[0174] Alternatively, the UE-TX may transmit a scheduling request to the S-UE using SL RRC signaling, which is effective in transmitting, for example, AS layer V2X capability information and SL bearer information to the S-UE.

[0175] As another method, the UE-TX may transmit a scheduling request to the S-UE using SL MAC signaling. The UE-TX may include the above-mentioned information in the MAC CE and notify it. The UE-TX may notify the scheduling request using the PSSCH. For example, in a state where a PC5 link (higher layer link) is established in advance between the UE-TX and the S-UE, when a V2X service using SL communication occurs in the UE-TX, the UE-TX can notify the S-UE of the scheduling request early. The S-UE can transmit the scheduling request received from the UE-TX to the gNB early.

[0176] As another method, the UE-TX may include the scheduling request in the SCI and transmit it to the S-UE. The UE-TX may notify the scheduling request using the PSCCH. The S-UE can receive the scheduling request without receiving the PSSCH. The S-UE can transmit the scheduling request received from the UE-TX to the gNB earlier.

[0177] As another method, a signal for the scheduling request may be provided. For example, a signal to which a predetermined code is assigned may be provided. Examples of the predetermined code include an orthogonal code and a Zadoff-Chu (ZC) sequence. The S-UE may individually assign the predetermined code to the UE-TX. This enables the S-UE to recognize which UE-TX has sent the signal for the scheduling request. The signal for the scheduling request may be notified in advance from the S-UE to the UE-TX. The UE-TX transmits the signal for the scheduling request to the S-UE. The S-UE receives the scheduling request from the UE-TX. In this way, the amount of resources used for the scheduling request can be reduced. This allows for an improvement in communication capacity and rapid scheduling.

[0178] Resources used for transmitting a scheduling request from the UE-TX to the S-UE may be reserved periodically. The period may be notified in advance between the S-UE and the UE-TX. For example, the period may be set by the S-UE and notified from the S-UE to the UE-TX. Alternatively, the period may be set by the UE-TX and notified from the UE-TX to the S-UE. The period may be configured in advance in the UE-TX, or may be stored in, for example, a SIM. The period may be notified, for example, when a PC5 link is established or when an RRC connection is established.

[0179] In this way, the UE-TX and the S-UE can transmit and receive the scheduling request. In addition, the S-UE can recognize the timing when the scheduling request is transmitted from the UE-TX, so that efficient reception is possible. The power consumption of the S-UE can be reduced.

[0180] The information to be included in the scheduling request notified from the S-UE to the gNB may be a part or all of the information to be included in the scheduling request notified from the UE-TX to the S-UE. In addition, information for identifying the S-UE may be included. The information for identifying the S-UE may be, for example, a UE identifier. The UE identifier may be a UE identifier assigned by the gNB. The gNB can recognize which S-UE the scheduling request is from.

[0181] The present invention discloses signaling used for a scheduling request notified from an S-UE to a gNB. An RRC connection is established between the S-UE and the gNB in ​​advance. Alternatively, the S-UE may establish an RRC connection with the gNB when receiving a scheduling request for SL communication from the UE-TX.

[0182] The S-UE may transmit a scheduling request to the gNB using signaling during the RRC connection establishment process. The gNB can receive the scheduling request from the S-UE early and can perform scheduling for the UE-TX early.

[0183] Alternatively, the S-UE may transmit the scheduling request to the gNB using RRC signaling, which is useful, for example, when the scheduling request is transmitted after the RRC connection is established.

[0184] As another method, the S-UE may transmit a scheduling request to the gNB using MAC signaling. The S-UE may include the above-mentioned information in the MAC CE and notify it. The S-UE may notify the scheduling request using the PUSCH. For example, when the S-UE receives a scheduling request for SL communication from the UE-TX in a state where an RRC connection is established between the S-UE and the gNB in ​​advance, the S-UE can notify the gNB of the scheduling request early. The gNB can perform scheduling for the UE-TX early.

[0185] Alternatively, the S-UE may transmit the scheduling request to the gNB via UCI. The S-UE may also transmit the scheduling request via PUCCH. The gNB can then schedule the UE-TX even earlier.

[0186] The S-UE may notify the gNB of information on the connected UE-TX. Alternatively, the S-UE may notify the gNB of information on the UE-TX to be scheduled. The UE-TX information may be information for identifying the UE-TX. The S-UE may notify the UE-TX information by using signaling during the RRC connection establishment process with the gNB. Alternatively, the S-UE may notify the UE-TX information after the RRC connection is established. The S-UE may notify the UE-TX information by using RRC signaling. The notification of the information may be performed separately from a scheduling request from the S-UE to the gNB.

[0187] In this way, the gNB can recognize the UE-TX to which the S-UE under its control is connected or to which scheduling is to be performed. By receiving the information, the gNB can determine whether or not it has acquired V2X policy / parameter information of the UE-TX to which the S-UE under its control is connected or to which scheduling is to be performed.

[0188] The gNB may set an SL bearer configuration to be used for the V2X service of the UE-TX to which the S-UE is connected or to which scheduling is to be performed. The gNB may set an SL bearer configuration to be used for the V2X service of the UE-TX using the acquired V2X policy / parameters of the UE-TX. The gNB notifies the UE-TX of the SL bearer configuration of the UE-TX via the S-UE.

[0189] The gNB may configure an SDAP for SL used for the V2X service of the UE-TX to which the S-UE is connected or to which scheduling is to be performed. The gNB may configure an SDAP for SL used for the V2X service of the UE-TX using the acquired V2X policy / parameters of the UE-TX. An example of the SDAP configuration is mapping from a PC5 QoS flow to an SL bearer. The gNB notifies the UE-TX of the SDAP configuration of the UE-TX via the S-UE.

[0190] The gNB may set an SR configuration for the UE-TX to which the S-UE is connected or to which scheduling is to be performed. The gNB may set the SR configuration in association with an LCID. The gNB may also set the SR configuration in association with the UE-TX. Alternatively, an SR for the UE-TX may be provided. In this way, it is possible to distinguish between an SR for SL communication performed by the S-UE itself and an SR for SL communication performed by the UE-TX scheduled by the S-UE.

[0191] The gNB notifies the S-UE of the set SR configuration. The gNB may notify the SR configuration by using signaling during the RRC connection establishment process performed by the S-UE and the gNB. Alternatively, the gNB may notify the SR configuration after the RRC connection is established. The gNB may notify the SR configuration by using RRC signaling. In this way, the gNB can notify the S-UE of the SL bearer configuration to be used for the V2X service of the UE-TX to which the S-UE is connected or to which scheduling is to be performed.

[0192] The S-UE may transmit a scheduling request to the gNB by including the SR in the SR. The S-UE may transmit the SR using the PUCCH.

[0193] FIG. 14 and FIG. 15 are sequence diagrams showing an example in which a gNB performs scheduling for SL communication between UEs in accordance with the first embodiment. FIG. 14 and FIG. 15 are connected at the position of a boundary line BL1415. SL communication is performed between UE-TX and UE-RX. UE-TX performs a process of providing V2X policy / parameters to CN via a gNB that is a RAN node. In step ST1401, UE-TX notifies gNB of a V2X policy / parameter request. UE-TX may perform a V2X policy / parameter request using a registration request transmitted for location registration or a service request transmitted for providing a service.

[0194] For example, the UE-TX may include information on the V2X service in a V2X policy / parameter request and notify the UE-TX. The UE-TX may include V2X capability in a V2X policy / parameter request and notify the UE-TX. In a case where SL communication is specialized, the UE-TX may notify the PC5 capability. By receiving the V2X capability, the gNB can determine that the UE-TX is capable of SL communication, and performs a V2X policy / parameter providing process for the CN.

[0195] In Step ST1402, the gNB notifies the AMF of a V2X policy / parameter request. As described above, the gNB may make a V2X policy / parameter request using a registration request transmitted for location registration or a service request transmitted for providing a service. The gNB may include an identifier of the UE-TX, which is the transmission source, in the V2X policy / parameter request. The AMF can determine that the UE-TX is capable of SL communication, and performs a V2X policy / parameter providing process for the PCF.

[0196] In Step ST1403, the AMF selects a PCF having policy / parameter information of the V2X service. If a registration request or a service request is used, a registration process or a service request process is performed in Step ST1404. In the case of a registration request, in Step ST1405, the AMF notifies the UE-TX of the receipt of the registration.

[0197] The AMF that has selected the PCF in Step ST1403 notifies the PCF of a V2X policy / parameter request in Step ST1406. For example, a UE policy control create request (Npcf_UEPolicyControl Create Request), which is signaling between the AMF and the PCF, may be used. In Step ST1407, the PCF that has received the V2X policy / parameter request determines the V2X policy / parameter to be provided to the UE-TX.

[0198] The PCF that has determined the V2X policy / parameter to be provided to the UE-TX provides the V2X policy / parameter to the gNB. The PCF may also provide the V2X policy / parameter to the UE-TX. In Step ST1408, the PCF notifies the AMF of the V2X policy / parameter of the UE-TX. The V2X policy / parameter may include, for example, a QoS parameter for SL communication (PC5 QoS Parameter). The V2X policy / parameter may be the V2X policy / parameter disclosed in Non-Patent Document 21. For the notification, a UE policy control create response (Npcf_UEPolicyControl Create Response), which is signaling between the AMF and the PCF, may be used.

[0199] In Step ST1410, the AMF stores the V2X policy / parameters of the UE-TX received from the PCF. In Step ST1411, the AMF notifies the gNB of the V2X policy / parameters of the UE-TX. The AMF may notify information regarding service authentication of the UE-TX. The information may be information indicating that the UE-TX has been authenticated for the V2X service. The gNB becomes able to recognize the V2X policy / parameters of the UE-TX by receiving the V2X policy / parameters of the UE-TX from the AMF.

[0200] By storing the V2X policy / parameter of the UE-TX received from the PCF, for example, when a V2X policy / parameter request of the UE-TX is received from a gNB after this process, the AMF can notify the gNB of the V2X policy / parameter of the UE-TX stored in its own AMF. The gNB may be a gNB served by the AMF.

[0201] In Step ST1409, the AMF may notify the UE-TX of the V2X policy / parameters of the UE-TX. The AMF may notify the UE-TX of the parameters via the gNB. This allows the UE-TX to recognize the V2X policy / parameters. When the UE-TX enters the coverage of the gNB, the UE-TX may update the V2X policy / parameters. For this update, the UE-TX may perform the above-mentioned V2X policy / parameter providing process. In this way, the UE-TX can update the V2X policy / parameters as appropriate.

[0202] In step ST1412, the gNB stores the V2X policy / parameters of the UE-TX received from the AMF. The gNB may also store information related to service authentication of the UE-TX. The gNB may store part or all of this information. This makes it possible to appropriately reduce the storage capacity. The gNB may store the V2X policies / parameters of multiple UE-TXs that have performed the V2X policy / parameter provision process. The gNB may store the UE-TXs and the V2X policies / parameters in association with each other.

[0203] In Step ST1413, the UE-TX establishes a PC5 link with the S-UE in order to obtain scheduling information for SL communication with the UE-RX from the S-UE. In Step ST1414, the UE-TX, in which V2X service data using SL communication has occurred, notifies the S-UE of a scheduling request for the SL communication. The UE-TX includes in the request the above-mentioned information, such as, for example, the V2X capability (which may be the PC5 capability) and the identifier of its own UE-TX. The UE-TX may notify the request, for example, by using SL RRC signaling. Before performing the SL RRC signaling, the UE-TX may perform a process of establishing an SL RRC connection with the S-UE.

[0204] When the S-UE receives the scheduling request from the UE-TX in Step ST1414, in Step ST1415, the S-UE transmits a scheduling request for the UE-TX to the gNB. The S-UE includes in the request the above-mentioned information, such as the V2X service, the V2X capability (which may be the PC5 capability), and the identifier of the UE requesting scheduling (the identifier of the UE-TX). The S-UE may notify the request, for example, by using RRC signaling of Uu. Before performing the RRC signaling of Uu, the S-UE may perform a process of establishing an RRC connection of Uu with the gNB.

[0205] In this way, the gNB can receive a scheduling request of the UE-TX that performs SL communication. In step ST1416, the gNB that receives the scheduling request of the UE-TX from the S-UE derives the V2X policy / parameters of the UE-TX that made the scheduling request from the V2X policy / parameters stored in step ST1412. The gNB performs scheduling for SL communication for the UE-TX using the V2X policy / parameters. In this way, scheduling suitable for the V2X policy / parameters is performed for the UE-TX.

[0206] In step ST1417, the gNB transmits scheduling information for SL communication of the UE-TX to the S-UE. For example, RRC signaling may be used. In step ST1418, the S-UE notifies the UE-TX of the scheduling information for SL communication of the UE-TX received from the gNB. The gNB may transmit the information, for example, in an SCI and on a PSCCH. The UE-TX performs SL communication with the UE-RX using the scheduling information received from the S-UE. The UE-TX may establish a PC5 link before performing the SL communication with the UE-RX. Also, the UE-TX may establish an RRC connection. Also, the UE-TX may notify the UE-TX of necessary RRC signaling.

[0207] In this way, in the SL communication between UE-TX and UE-RX, scheduling is performed using the V2X policy / parameters of the V2X service using the SL communication. This makes it possible to perform scheduling according to the QoS desired for the V2X service.

[0208] In the above, it has been disclosed that the scheduling request from the S-UE to the gNB includes information indicating which UE-TX's SL communication the scheduling request is for. The gNB may use the information to determine whether the PC5 QoS parameters of the UE-TX are present in the recorded PC5 QoS parameters. If the PC5 QoS parameters of the UE-TX are present, the gNB performs scheduling for the S-UE using the PC5 QoS parameters of the UE-TX.

[0209] If the PC5 QoS parameters of the UE-TX are not present, the gNB may make a V2X policy / parameter request of the UE-TX to the PCF. The V2X policy / parameter request of the UE-TX may be made via the AMF. In this case, when the AMF receives the V2X policy / parameter request of the UE-TX from the gNB, the AMF makes a V2X policy / parameter request of the UE-TX to the PCF. When the PCF receives the V2X policy / parameter request of the UE-TX, the PCF notifies the gNB of the V2X policy / parameter of the UE-TX. The PCF may make the notification via the AMF.

[0210] The AMF may store the V2X policy / parameter of the UE-TX received from the PCF. The gNB may store the V2X policy / parameter of the UE-TX received from the PCF. The AMF and the gNB may store part or all of this information. The storage capacity can be appropriately reduced.

[0211] If the AMF stores the V2X policy / parameter of the UE-TX, the AMF may provide the V2X policy / parameter of the UE-TX to the gNB. If the AMF does not store the V2X policy / parameter of the UE-TX, the AMF may notify the PCF of the V2X policy / parameter request of the UE-TX. In this way, there are cases where the signaling of the V2X policy / parameter request and provision does not need to be performed to the PCF. This reduces the signaling load and the processing delay time.

[0212] The gNB may make a V2X policy / parameter request for the UE-TX to a neighboring gNB. The gNB may include information for identifying the target UE-TX and / or information for identifying the source gNB in ​​the V2X policy / parameter request. The gNB may transmit the V2X policy / parameter for the UE-TX to a neighboring gNB. The gNB may transmit information for identifying the target UE-TX and / or information for identifying the source gNB together with the V2X policy / parameter. When the gNB that receives the V2X policy / parameter request stores the V2X policy / parameter for the UE-TX, the gNB may transmit the V2X policy / parameter for the UE-TX to the requesting gNB. The gNB may transmit information for identifying the target UE-TX and / or information for identifying the source gNB and / or information for identifying the requesting gNB together with the V2X policy / parameter. The UE-TX's V2X policy / parameter request and V2X policy / parameter transmission between gNBs may use the Xn interface.

[0213] In this way, the V2X policy / parameters of the UE-TX can be shared between the gNBs. When the V2X policy / parameters of the UE-TX are not present in the stored PC5 QoS parameters, the gNB may perform the above-mentioned process of requesting the V2X policy / parameters of the UE-TX between the gNBs. In this way, the V2X policy / parameters of the UE-TX can be acquired between the gNBs. Even if the gNB to which the S-UE is connected is different from the gNB that performed the V2X policy / parameter provision process for the UE-TX, the gNB can acquire the V2X policy / parameters of the UE-TX.

[0214] By using the method disclosed in the first embodiment, the gNB can perform SL communication scheduling based on the QoS parameters required for the V2X service of the UE-TX. In addition, the S-UE does not need to perform scheduling, and the S-UE does not need to obtain the QoS parameters of the V2X service of the UE-TX. This reduces the complexity of processing and reduces the signaling load.

[0215] Variation 1 of the first embodiment In the first modification of the first embodiment, another method for solving the problem described in the first embodiment will be disclosed.

[0216] The UE-TX performs a process of providing a V2X policy / parameter to the CN in advance via a RAN node such as a gNB. This method may be the method disclosed in the first embodiment. The gNB may also store the V2X policy / parameter of the UE-TX acquired from the CN. This method may also be the method disclosed in the first embodiment.

[0217] The S-UE requests the gNB to provide the V2X policy / parameters of the UE-TX that is to be scheduled. The UE-TX may transmit a request for scheduling for SL communication to the S-UE. When the S-UE receives the scheduling request for SL communication from the UE-TX, the S-UE may request the gNB to provide the V2X policy / parameters of the UE-TX.

[0218] The following (1) to (7) are disclosed as specific examples of information to be included in a request for provision of V2X policy / parameters notified from the S-UE to the gNB.

[0219] (1) Information indicating a request to provide V2X policy / parameters.

[0220] (2) Information for identifying UE-TX.

[0221] (3) Information for identifying the S-UE.

[0222] (4) V2X capability of UE-TX.

[0223] (5) UE-TX V2X service information.

[0224] (6) Application layer information of UE-TX.

[0225] (7) A combination of (1) to (6) above.

[0226] The information (1) may be, for example, information indicating that this is a request for provision of V2X policy / parameters for SL communication implemented by UE-TX.

[0227] The information (2) may be, for example, a UE identifier. The information (2) may be an identifier of the UE-TX. The information (2) may be a layer 2 ID (L2 ID) used by the UE-TX in SL communication. The gNB can recognize which UE-TX is requesting the provision of V2X policy / parameters.

[0228] The information in (3) may be, for example, a UE identifier. The information in (3) may be an identifier of a UE that performs scheduling for UE-TX. The information in (3) may be a Layer 2 ID (L2 ID) used by an S-UE. This allows the gNB to recognize which UE performs scheduling for UE-TX.

[0229] The information in (4) may be, for example, information on whether the UE-TX has V2X capability. The information in (4) may be information on whether the UE-TX has PC5 capability. The gNB becomes able to recognize whether the UE-TX is capable of SL communication.

[0230] The information in (5) may be, for example, a V2X service identifier. The information in (5) may be a provider service identifier (PSID) or an intelligent transport systems application identifier (ITS-AID). This enables the gNB to recognize which V2X service the request for providing V2X policies / parameters is for.

[0231] The information in (6) may be, for example, an application layer identifier. The information in (6) may be an identifier corresponding to an object in which the UE-TX is mounted. The object in which the UE-TX is mounted may be, for example, a car, a pedestrian, or the like. An identifier for identifying an object in which the UE-TX is mounted may be used as an identifier for identifying the UE-TX. The gNB becomes able to recognize for which application the request for provision of V2X policy / parameters is made.

[0232] The method of notifying the gNB of the V2X policy / parameter provision request from the S-UE may be appropriately applied to the method of notifying the gNB of the scheduling request from the S-UE disclosed in the first embodiment. For example, signaling used for the scheduling request notified from the S-UE to the gNB may be appropriately applied.

[0233] The gNB notifies the S-UE of the V2X policy / parameter of the UE-TX acquired from the CN. When the gNB receives a V2X policy / parameter request of the UE-TX, the gNB may notify the S-UE of the V2X policy / parameter of the UE-TX. In this way, the S-UE can acquire the V2X policy / parameter of the UE-TX to which scheduling is to be performed.

[0234] The gNB may notify the S-UE of some or all of the V2X policy / parameters of the UE-TX. For example, the gNB may notify only the PC5 QoS parameters included in the V2X policy / parameters. This makes it possible to reduce the amount of information notified from the gNB to the S-UE.

[0235] The gNB may notify the V2X policy / parameter of the UE-TX by using signaling during the RRC connection establishment process. Alternatively, the gNB may notify the V2X policy / parameter of the UE-TX after the RRC connection is established. The gNB may notify the V2X policy / parameter of the UE-TX by using RRC signaling. In this manner, the gNB can notify the S-UE of the V2X policy / parameter used for the V2X service of the UE-TX to which the S-UE is connected or to which scheduling is to be performed.

[0236] The S-UE may store the V2X policy / parameter of the UE-TX acquired from the gNB. The S-UE may store the V2X policy / parameter in association with the identifier of the UE-TX and / or information for identifying the V2X service. The S-UE becomes able to recognize which UE-TX and which V2X service the V2X policy / parameter belongs to.

[0237] The S-UE performs scheduling for SL communication for the UE-TX. A method for the S-UE to perform scheduling for SL communication for the UE-TX is disclosed. The UE-TX may transmit a request for scheduling for SL communication to the S-UE. As a specific example of information to be included in the scheduling request notified from the UE-TX to the S-UE, and a method of transmitting the scheduling request from the UE-TX to the S-UE, the method disclosed in the first embodiment may be applied as appropriate. The S-UE may perform scheduling for the UE-TX by receiving the scheduling request.

[0238] When the S-UE receives a scheduling request for SL communication from the UE-TX, the S-UE determines whether or not it has acquired the V2X policy / parameters of the UE-TX from the gNB. If the S-UE has acquired the V2X policy / parameters of the UE-TX from the gNB, the S-UE performs scheduling of the UE-TX using the V2X policy / parameters of the UE-TX.

[0239] If the S-UE has not acquired the V2X policy / parameter of the UE-TX from the gNB, the S-UE may notify the gNB of the V2X policy / parameter request of the UE-TX. As a result, the gNB notifies the S-UE of the V2X policy / parameter of the UE-TX. The S-UE performs scheduling of the UE-TX using the acquired V2X policy / parameter of the UE-TX.

[0240] When the S-UE receives a scheduling request for SL communication from the UE-TX, the S-UE may determine whether the S-UE can connect to the gNB or is currently connected. For example, when the S-UE is within the coverage of the gNB, the S-UE can connect to the gNB or is currently connected. When the S-UE is outside the coverage of the gNB, the S-UE is not connected to the gNB and cannot connect. When the S-UE can connect to the gNB, the S-UE may perform a connection process with the gNB and transmit a V2X policy / parameter request of the UE-TX to the gNB. When the S-UE is connected to the gNB, the S-UE may transmit a V2X policy / parameter request of the UE-TX to the gNB. The connection state may be an RRC connection.

[0241] The S-UE may set up a bearer for SL communication of the UE-TX. A bearer for SL communication may be called an SL bearer. When the S-UE acquires the V2X policy / parameter of the UE-TX, the S-UE may set up the SL bearer of the UE-TX. The S-UE may set up the SL bearer by RRC for SL.

[0242] The S-UE may set up an SL bearer when a PC5 link with the UE-TX is established. The S-UE may set up an SL bearer in response to an RRC connection establishment process with the UE-TX. The S-UE may set up an SL bearer when an RRC signaling such as an RRC connection request is received from the UE-TX. RRC signaling for an SL bearer setting request may be provided. By using the RRC signaling, the S-UE can process the signaling and the SL bearer setting process in the RRC layer. In other words, inter-layer processing is not required.

[0243] When the S-UE receives a scheduling request for SL communication from the UE-TX, the S-UE may set up a bearer for SL communication of the UE-TX. The scheduling request for SL communication may include information on a request for setting up an SL bearer, for example, information on whether or not to request setting up an SL bearer. If the information requesting setting up an SL bearer is included, the S-UE may set up an SL bearer for the UE-TX. The above-mentioned conditions for setting up an SL bearer may be applied in appropriate combination.

[0244] The S-UE notifies the UE-TX of the SL bearer that it has set up for the UE-TX. The S-UE's RRC for SL may set up the SL bearer. The S-UE may assign an LCID to each bearer when setting up the SL bearer. The S-UE may assign an LCID to each signaling bearer and each data communication bearer. As a notification method, the signaling used when establishing a PC5 link may be used, or RRC signaling may be used. By the S-UE setting up a bearer to be used for SL communication between other UEs, the S-UE can perform scheduling for SL communication between other UEs in association with the bearer.

[0245] The S-UE may configure an SDAP for SL used for the V2X service of the UE-TX. The S-UE may configure the SDAP using the acquired V2X policy / parameter of the UE-TX. The SDAP configuration may include, for example, mapping from a PC5 QoS flow to an SL bearer. The S-UE notifies the UE-TX of the SDAP configuration.

[0246] The S-UE may set the SDAP when a PC5 link with the UE-TX is established. The S-UE may set the SDAP when a PC5 link is established with the UE-TX. The S-UE may set the SDAP in response to an RRC connection establishment process with the UE-TX. The S-UE may set the SDAP when an RRC signaling such as an RRC connection request is received from the UE-TX. Signaling for an SL SDAP setting request may be provided. The signaling may be PC5 signaling or RRC signaling.

[0247] When the S-UE receives a scheduling request for SL communication from the UE-TX, the S-UE may configure the SDAP of the UE-TX. The scheduling request for SL communication may include information on a request for configuring the SDAP for SL, for example, information on whether or not to request the configuration of the SDAP for SL. When the information requesting the configuration of the SDAP is included, the S-UE may configure the SDAP for SL for the UE-TX.

[0248] The S-UE notifies the UE-TX of the setting of the SDAP for SL of the UE-TX that has been set. The SDAP for SL of the S-UE may set the SDAP for SL of the UE-TX. As a notification method, signaling at the time of PC5 link establishment or RRC signaling may be used. In this manner, the S-UE is able to set the SDAP for SL for the UE-TX.

[0249] An SR (Suscheduling Request) for SL may be provided. SR may be a function of SL MAC. SR may be included in MAC CE. The SR configuration may be set in advance by RRC for SL. SL SR may be set in association with LCID. Alternatively, SL SR may be set in association with RLC bearer. SR setting may be performed by the UE that performs scheduling. For example, when S-UE schedules SL communication between other UEs, S-UE sets SR, and when UE-TX schedules SL communication, UE-TX sets SR. The setting of SR for SL may be notified by using RRC signaling between UEs. Alternatively, the setting of SR for SL may be notified when PC5 link is established between UEs.

[0250] The SR setting information may be included in the setting of the SL bearer and notified. For example, when SL data occurs in the UE-TX, the UE-TX may notify the S-UE of the SR as a scheduling request. The UE-TX may transmit the SR using the PSSCH. In this way, it is possible to use the SR of the SL for the scheduling request.

[0251] The SR for SL may be one of the methods of transmitting a scheduling request from the UE-TX to the S-UE disclosed in the first embodiment. The S-UE may transmit a scheduling request of the UE-TX to the gNB using the scheduling request. For example, the method may be used for transmitting a scheduling request when data is dynamically generated in the UE-TX. In this way, the SR for SL can be used both when the gNB performs scheduling and when the S-UE performs scheduling. It is possible to simplify the process for the scheduling request.

[0252] Fig. 16 and Fig. 17 are sequence diagrams showing an example in which an S-UE performs scheduling for SL communication with other UEs in the first modification of the first embodiment. Fig. 16 and Fig. 17 are connected at the position of a boundary line BL1617. In Fig. 16 and Fig. 17, the same step numbers are assigned to steps common to Fig. 14 and Fig. 15, and common explanations are omitted. SL communication is performed between UE-TX and UE-RX. UE-TX performs a process of providing V2X policy / parameters with CN via gNB. The gNB stores the V2X policy / parameters of UE-TX.

[0253] When the S-UE receives the scheduling request from the UE-TX in Step ST1414, in Step ST1501, the S-UE transmits a V2X policy / parameter request of the UE-TX to the gNB. The S-UE includes in the request the above-mentioned information, such as the V2X service, the V2X capability (which may be PC5 capability), and the identifier of the UE requesting the V2X policy / parameter (the identifier of the UE-TX). The S-UE may notify the request, for example, by using RRC signaling of Uu. Before performing the RRC signaling of Uu, the S-UE may perform a process of establishing an RRC connection of Uu with the gNB.

[0254] In this way, the gNB can receive a V2X policy / parameter request of the UE-TX that performs SL communication. The gNB that receives the V2X policy / parameter request of the UE-TX from the S-UE derives the V2X policy / parameter of the UE-TX that made the V2X policy / parameter request from the V2X policy / parameter stored in Step ST1412. In Step ST1502, the gNB notifies the S-UE of the V2X policy / parameter of the UE-TX. For example, RRC signaling may be used.

[0255] In step ST1503, the S-UE performs scheduling for SL communication using the V2X policy / parameters of the UE-TX received from the gNB. In this way, scheduling suitable for the V2X policy / parameters is performed for the UE-TX. The S-UE may store the V2X policy / parameters of the UE-TX received from the gNB. The S-UE may store a part or all of this information. This makes it possible to appropriately reduce the storage capacity. In step ST1418, the S-UE notifies the UE-TX of the scheduling information. For example, the S-UE may include the information in the SCI and transmit it on the PSCCH. The UE-TX performs SL communication with the UE-RX using the scheduling information received from the S-UE.

[0256] In this way, in the SL communication between UE-TX and UE-RX, scheduling is performed using the V2X policy / parameters of the V2X service using the SL communication. This makes it possible to perform scheduling according to the QoS desired for the V2X service.

[0257] There are cases where the gNB to which the S-UE transmits a V2X policy / parameter provision request for the UE-TX is different from the gNB to which the UE-TX performed the V2X policy / parameter provision request process. For example, there are cases where the S-UE connects to a gNB different from the gNB to which the UE-TX performed the V2X policy / parameter provision request process due to the UE-TX moving together with the S-UE. In such cases, the gNB may not have acquired the V2X policy / parameters for the UE-TX. A method for solving such a problem is disclosed.

[0258] As described above, it has been disclosed that a V2X policy / parameter provision request from an S-UE to a gNB includes information indicating which UE-TX's SL communication the V2X policy / parameter provision request is for. The gNB may use the information to determine whether or not the PC5 QoS parameters of the UE-TX are present in the recorded PC5 QoS parameters. If the PC5 QoS parameters of the UE-TX are present, the gNB transmits the PC5 QoS parameters of the UE-TX to the S-UE.

[0259] If the PC5 QoS parameters of the UE-TX are not present, the gNB may make a V2X policy / parameter request of the UE-TX to the PCF. The V2X policy / parameter request of the UE-TX may be made via the AMF. In this case, when the AMF receives the V2X policy / parameter request of the UE-TX from the gNB, the AMF makes a V2X policy / parameter request of the UE-TX to the PCF. When the PCF receives the V2X policy / parameter request of the UE-TX, the PCF transmits the V2X policy / parameter of the UE-TX to the gNB. The PCF may perform the notification via the AMF. When the gNB receives the V2X policy / parameter of the UE-TX, the gNB transmits the V2X policy / parameter of the UE-TX to the S-UE.

[0260] The AMF may store the V2X policy / parameter of the UE-TX received from the PCF. The gNB may store the V2X policy / parameter of the UE-TX received from the PCF. The S-UE may store the V2X policy / parameter of the UE-TX received from the PCF. The AMF, the gNB, and the S-UE may store a part or all of this information. The storage capacity can be appropriately reduced.

[0261] If the AMF stores the V2X policy / parameters of the UE-TX, the AMF may provide the V2X policy / parameters of the UE-TX to the gNB. The gNB transmits the V2X policy / parameters of the UE-TX to the S-UE. If the AMF does not store the V2X policy / parameters of the UE-TX, the AMF may notify the PCF of the V2X policy / parameter request of the UE-TX. In this way, there are cases where the signaling of the V2X policy / parameter request and provision does not need to be performed to the PCF. This reduces the signaling load and the processing delay time.

[0262] Also, the V2X policy / parameters of the UE-TX may be shared between gNBs. The method may be appropriately applied to the method disclosed in the first embodiment. Even if the S-UE requests the provision of the V2X policy / parameters to a gNB different from the gNB that performed the V2X policy / parameter provision process by the UE-TX, the different gNB can acquire the V2X policy / parameters of the UE-TX and can transmit the V2X policy / parameters of the UE-TX to the S-UE.

[0263] By using the method disclosed in the first modification of the first embodiment, the S-UE can perform scheduling for SL communication based on the QoS parameters required for the V2X service of the UE-TX. Therefore, the S-UE can perform scheduling for SL communication between UEs in a group or a specific area. In this way, by enabling the S-UE to perform scheduling for SL communication, interference reduction in SL communication between other UEs and low latency of SL communication can be achieved.

[0264] Variation 2 of embodiment 1 In the second modification of the first embodiment, another method for solving the problem described in the first embodiment will be disclosed.

[0265] The UE-TX performs a V2X policy / parameter providing process for the CN via the S-UE. In the V2X policy / parameter providing process, the UE-TX requests the CN to provide the V2X policy / parameter via the S-UE. The UE-TX may request the CN to provide the V2X policy / parameter via the S-UE and the gNB. For example, the UE-TX transmits a V2X policy / parameter providing request to the S-UE. The S-UE that receives the request transmits a V2X policy providing request of the UE-TX to the gNB. The gNB that receives the request notifies the CN that it will transmit the V2X policy providing request.

[0266] A V2X policy / parameter provision request may be made from the S-UE to the CN. The V2X policy / parameter request process from the S-UE to the CN may be appropriately applied to the V2X policy / parameter request process performed from the UE-TX to the CN via the gNB, as disclosed in the first embodiment. The request may include information indicating that it is a V2X policy / parameter request process of the UE-TX. The CN can recognize that the request is not a V2X policy / parameter request of the S-UE, but a V2X policy / parameter request of the UE-TX. The V2X policy / parameter of the UE-TX can be provided.

[0267] The CN that receives the request provides the V2X policy / parameter to the S-UE. For example, the PCF may provide the V2X policy / parameter of the UE-TX to the S-UE via the AMF and the gNB. For example, NAS signaling may be used to notify the V2X policy / parameter of the UE-TX from the AMF to the S-UE.

[0268] The CN that receives the request may provide the V2X policy / parameter to the UE-TX. The CN may provide the V2X policy / parameter to the UE-TX via the gNB and the S-UE. For example, the CN transmits the V2X policy / parameter to the gNB. The gNB that receives the V2X policy / parameter transmits the V2X policy / parameter of the UE-TX to the S-UE. The CN and / or the gNB may notify the S-UE of a part or all of the V2X policy / parameter. For example, only the PC5 QoS parameter of the V2X policy / parameter may be notified. The amount of information to be notified can be reduced. The S-UE that receives the V2X policy / parameter may transmit the V2X policy / parameter of the UE-TX to the UE-TX. The CN and / or the gNB and / or the S-UE may notify the UE-TX of a part or all of the V2X policy / parameter. For example, only the PC5 QoS parameter of the V2X policy / parameter may be notified. The amount of information to be notified can be reduced.

[0269] The V2X policy or V2X parameter may be, for example, a V2X policy or V2X parameter on PC5 (also referred to as a PC5 reference point) as in the first embodiment. The V2X parameter may be a QoS parameter.

[0270] The CN node may be a PCF. The PCF may provide the V2X policy / parameters to the S-UE via the AMF. Alternatively, the CN node may be an AMF. This is effective in the case where the AMF stores the V2X policy / parameters of the UE-TX acquired from the PCF in advance.

[0271] The UE-TX may connect to the S-UE and perform a V2X policy / parameter provision process. The S-UE may obtain V2X policies / parameters of multiple UE-TXs that are targets of scheduling. This allows the S-UE to obtain the V2X policies / parameters of the UE-TXs from the CN.

[0272] The S-UE may store the V2X policy / parameter of the UE-TX acquired from the CN. The S-UE may store the V2X policy / parameter in association with the identifier of the UE-TX and / or information for identifying the V2X service. The S-UE becomes able to recognize which UE-TX and which V2X service the V2X policy / parameter belongs to.

[0273] FIG. 18 and FIG. 19 are sequence diagrams showing an example in which the S-UE performs scheduling for SL communication with other UEs in the second modification of the first embodiment. FIG. 18 and FIG. 19 are connected at the position of the boundary line BL1819. In FIG. 18 and FIG. 19, the same step numbers are assigned to steps common to FIG. 16 and FIG. 17, and common explanations are omitted. SL communication is performed between the UE-TX and the UE-RX. The UE-TX performs a process of providing a V2X policy / parameter with the CN via the S-UE. In step ST1601, the UE-TX notifies the S-UE of a V2X policy / parameter request. The UE-TX may notify the CN side of a registration request transmitted for location registration or a service request transmitted for providing a service via the S-UE. The UE-TX may perform a V2X policy / parameter request using the registration request or the service request.

[0274] For example, the UE-TX may include information on the V2X service in a V2X policy / parameter request and notify the same. The UE-TX may include V2X capability in a V2X policy / parameter request and notify the same. In a case where the UE-TX is specialized for SL communication, the UE-TX may notify the PC5 capability. By receiving the V2X capability, the S-UE can determine that the UE-TX is capable of SL communication, and performs a V2X policy / parameter providing process for the gNB.

[0275] In Step ST1602, the S-UE notifies the gNB of a V2X policy / parameter request. As described above, the S-UE may make a V2X policy / parameter request using a registration request transmitted for location registration or a service request transmitted for providing a service. The S-UE may include an identifier of the UE-TX, which is the transmission source, in the V2X policy / parameter request. The gNB can determine that the UE-TX is capable of SL communication, and performs a V2X policy / parameter providing process for the AMF.

[0276] In Step ST1603, the gNB notifies the AMF of a V2X policy / parameter request. As described above, the gNB may make a V2X policy / parameter request using a registration request transmitted for location registration or a service request transmitted for providing a service. The gNB may include an identifier of the UE-TX, which is the transmission source, in the V2X policy / parameter request. The AMF can determine that the UE-TX is capable of SL communication, and performs a V2X policy / parameter providing process for the PCF.

[0277] In Step ST1601, in order for the UE-TX to transmit a V2X policy / parameter request to the S-UE, the UE-TX may establish a PC5 link with the S-UE. Also, the UE-TX may establish an RRC connection in SL. The UE-TX may transmit the request, for example, by RRC signaling in SL.

[0278] In Step ST1602, in order for the S-UE to transmit a V2X policy / parameter request for UE-TX to the gNB, the S-UE may establish an RRC connection for Uu with the gNB. The S-UE may transmit the request, for example, by RRC signaling for Uu.

[0279] The signaling from the UE-TX to the AMF in steps ST1601, ST1602, and ST1603 may be transmitted by NAS signaling. The signaling from the UE-TX to the AMF may be included in a message of the NAS layer and transmitted by NAS signaling. Information included in the NAS message from the UE-TX to the AMF may be included in an RRC message of SL to the S-UE as container information and transmitted by RRC signaling, and may be included in an RRC message of Uu from the S-UE to the gNB and transmitted by RRC signaling. Not only the V2X policy / parameter request, but also the NAS message notified between the UE-TX and the AMF may be transmitted using the above-mentioned method. Even when an S-UE is interposed between the UE-TX and the AMF, it is possible to notify the NAS signaling.

[0280] When the AMF receives the V2X policy / parameter request of the UE-TX from the gNB in ​​Step ST1603, the AMF performs a V2X policy / parameter providing process for the PCF. The PCF performs a V2X policy / parameter providing process for the gNB. In addition, the PCF may perform a V2X policy / parameter providing process for the UE-TX.

[0281] When the gNB receives the V2X policy / parameters of the UE-TX from the CN in Step ST1411, in Step ST1604, the gNB transmits the V2X policy / parameters of the UE-TX to the S-UE that has made the V2X policy / parameter request for the UE-TX. RRC signaling may be used. The gNB may transmit information related to authentication of the UE-TX to the S-UE. In this way, the S-UE can recognize the V2X policy / parameters of the UE-TX.

[0282] In step ST1605, the S-UE stores the V2X policy / parameters of the UE-TX received from the gNB. The S-UE may also store information related to service authentication of the UE-TX. The S-UE may store part or all of this information. This makes it possible to appropriately reduce the storage capacity. The S-UE may store the V2X policies / parameters of multiple UE-TXs that have performed the V2X policy / parameter provision process. The S-UE may store the UE-TX and the V2X policy / parameters in association with each other.

[0283] When the S-UE receives the scheduling request from the UE-TX in step ST1414, in step ST1503, it derives the V2X policy / parameter of the UE-TX that has made the V2X policy / parameter request from the V2X policy / parameter stored in step ST1605. The S-UE performs scheduling for SL communication using the derived V2X policy / parameter of the UE-TX. In this way, scheduling suitable for the V2X policy / parameter is performed for the UE-TX.

[0284] In Step ST1418, the S-UE notifies the UE-TX of the scheduling information. The UE-TX performs SL communication with the UE-RX using the scheduling information received from the S-UE.

[0285] In this way, in the SL communication between UE-TX and UE-RX, scheduling is performed using the V2X policy / parameters of the V2X service using the SL communication. This makes it possible to perform scheduling according to the QoS desired for the V2X service.

[0286] By using the method disclosed in this modified example 2, the S-UE can acquire the QoS parameters of the V2X service of the UE-TX. Even if the gNB has not acquired the QoS parameters of the V2X service of the UE-TX in advance, the S-UE can acquire the QoS parameters of the V2X service of the UE-TX. The S-UE can perform scheduling for SL communication based on the QoS parameters of the V2X service of the UE-TX. By the S-UE performing scheduling for SL communication, interference reduction and low latency in SL communication between UEs can be achieved.

[0287] Variation 3 of embodiment 1 In the third modification of the first embodiment, another method for solving the problem described in the first embodiment will be disclosed.

[0288] The UE-TX transmits the V2X policy / parameters that the UE-TX has to the S-UE. The V2X that the UE-TX has may be a V2X policy / parameters that are preset in the UE, for example, a V2X policy / parameters that are preset in the SIM of the UE. The S-UE may transmit a request for providing the V2X policy / parameters to the UE-TX. In this way, even if the S-UE is outside the coverage of the gNB, the S-UE can acquire the V2X policy / parameters of the UE-TX. The S-UE can perform scheduling for SL communication for the UE-TX by using the acquired V2X policy / parameters of the UE-TX.

[0289] When the UE-TX moves into the coverage of the gNB, the UE-TX may perform a V2X policy / parameter providing process for the CN via the gNB. In the V2X policy / parameter providing process, the CN provides the UE-TX with the V2X policy / parameter. The UE-TX may update the V2X policy / parameter held in the UE-TX itself with the V2X policy / parameter acquired from the CN via the gNB. In this way, the V2X policy / parameter can be updated. The UE-TX may transmit the updated V2X policy / parameter to the S-UE. In this way, the UE-TX can provide the updated V2X policy / parameter to the S-UE, and the S-UE can perform scheduling for the UE-TX using the V2X policy / parameter.

[0290] Fig. 20 is a sequence diagram showing an example in which an S-UE performs scheduling for SL communication with other UEs in accordance with the third modification of the first embodiment. In Fig. 20, the same step numbers are assigned to steps common to Figs. 18 and 19, and common explanations are omitted. SL communication is performed between UE-TX and UE-RX. UE-TX provides V2X policies / parameters to S-UE. In Step ST1701, UE-TX transmits V2X policies / parameters held in its own UE-TX to S-UE.

[0291] When a PC5 link is established between the UE-TX and the S-UE in Step ST1413, the UE-TX may transmit the V2X policy / parameters to the S-UE. Alternatively, when an RRC connection is established between the UE-TX and the S-UE, the UE-TX may transmit the V2X policy / parameters to the S-UE when the RRC connection is established. Alternatively, the UE-TX may transmit the V2X policy / parameters to the S-UE by using RRC signaling of the SL.

[0292] In this way, the S-UE can acquire the V2X policy / parameters of the UE-TX. When the S-UE receives the V2X policy / parameters from the UE-TX in Step ST1701, the S-UE stores the V2X policy / parameters of the UE-TX in Step ST1605.

[0293] When the S-UE receives the scheduling request from the UE-TX in step ST1414, in step ST1503, it derives the V2X policy / parameter of the UE-TX that has made the V2X policy / parameter request from the V2X policy / parameter stored in step ST1605. The S-UE performs scheduling for SL communication using the derived V2X policy / parameter of the UE-TX. In this way, scheduling suitable for the V2X policy / parameter is performed for the UE-TX.

[0294] In Step ST1418, the S-UE notifies the UE-TX of the scheduling information. The UE-TX performs SL communication with the UE-RX using the scheduling information received from the S-UE.

[0295] In this way, in the SL communication between UE-TX and UE-RX, scheduling is performed using the V2X policy / parameters of the V2X service using the SL communication. This makes it possible to perform scheduling according to the QoS desired for the V2X service.

[0296] By using the method disclosed in this third modification, the S-UE can acquire the QoS parameters of the V2X service of the UE-TX. Even if the S-UE is outside the coverage of the gNB, the S-UE can acquire the QoS parameters of the V2X service of the UE-TX. The S-UE can perform scheduling for SL communication based on the QoS parameters of the V2X service of the UE-TX. By the S-UE performing scheduling for SL communication, interference and delay in SL communication between UEs can be reduced.

[0297] The S-UE may determine whether to use the method disclosed in the second modification of the first embodiment or the method disclosed in the third modification of the first embodiment based on whether the S-UE can connect to the gNB or is currently connected. For example, when the S-UE is in the coverage of the gNB, the S-UE can connect to the gNB or is currently connected. For example, when the S-UE is in the coverage of the gNB, the method disclosed in the second modification of the first embodiment is used. The S-UE may perform a connection process with the gNB and make a request to the CN to provide the V2X policy / parameters of the UE-TX.

[0298] When the S-UE is outside the coverage of the gNB, the method of the third modification of the first embodiment is used. The S-UE may request the UE-TX for the V2X policy / parameters. In this way, the S-UE can acquire the V2X policy / parameters of the UE-TX according to its own location and the connection state with the gNB.

[0299] The S-UE may notify the UE-TX that performs scheduling of information indicating whether the S-UE is in the coverage of the gNB or out of coverage. The S-UE may notify the UE-TX that performs scheduling of information indicating whether the S-UE can connect to the gNB or is currently connected. The UE-TX can determine whether the S-UE can connect to the gNB or not.

[0300] The UE-TX may determine whether to use the method disclosed in the second modification of the first embodiment or the method disclosed in the third modification of the first embodiment, based on whether the S-UE can connect to the gNB or is currently connected. For example, when the S-UE is within the coverage of the gNB, the method disclosed in the second modification of the first embodiment is used. The S-UE may perform a connection process with the gNB and make a request to the CN for providing the V2X policy / parameters of the UE-TX.

[0301] When the S-UE is outside the coverage of the gNB, the method of the third modification of the first embodiment is used. The UE-TX may provide the S-UE with the V2X policy / parameters of the UE-TX. In this way, the S-UE can acquire the V2X policy / parameters of the UE-TX according to its own location and the connection state with the gNB.

[0302] Embodiment 2 It has been proposed to use SL communication not only for vehicle-to-vehicle communication but also for other services, such as communication between wearable devices and communication between robots and control devices used in factories. In such cases, SL communication is performed between many UEs. To perform SL communication, it is necessary to detect and reserve available resources from SL communication resources. However, when SL communication is performed between many UEs, congestion occurs. This causes problems such as an increased delay time until SL communication starts or the impossibility of SL communication, even for V2X services that require low latency.

[0303] As a method for solving such problems, the introduction of preemption has been proposed in SL communication. Preemption is a technology that preempts data transmission to a UE that is already in progress with transmission to another UE that requires low latency characteristics (see Non-Patent Document 16).

[0304] In the second embodiment, another method for solving the above-mentioned problem will be disclosed.

[0305] The S-UE pre-empts an existing inter-UE communication with another inter-UE communication that requires low latency. The S-UE uses resources scheduled for SL communication between some UEs (e.g., between UE-TX1 and UE-RX1) for SL communication between other UEs (e.g., between UE-TX2 and UE-RX2). The S-UE schedules SL communication between other UEs using resources scheduled for SL communication between some UEs.

[0306] The S-UE notifies the UE-TX (UE-TX1) that scheduled first of information on preemption. The S-UE notifies the UE-TX (UE-TX2) that scheduled later of the scheduling information. The preemption information notified by the S-UE to the UE-TX1 may be information indicating that the scheduled resource is preempted. The information may include resource allocation information to be preempted. The information may be referred to as a preemption indication (PI).

[0307] UE-TX1 stops transmission using the resource notified by the S-UE in the PI. Alternatively, UE-TX1 may set the transmission power to 0 or may reduce the transmission power. UE-TX2 performs SL communication using the scheduling information notified by the S-UE. In this way, the S-UE can use resources scheduled for SL communication between one UE for SL communication between other UEs.

[0308] If the resources scheduled for SL communication between UE-TX1 and UE-RX1 are preempted, and if nothing is done, UE-RX1 will erroneously receive data for SL communication between UE-TX2 and UE-RX2. A method for solving such a problem is disclosed.

[0309] UE-TX1 notifies UE-RX1 of information related to preemption. The information related to preemption notified by UE-TX1 to UE-RX1 may be a PI. By receiving the PI notified from UE-TX1, UE-RX1 can recognize resources preempted for communication between other UEs, and can avoid receiving or decoding data of the resources. Alternatively, UE-RX1 may discard the received data. In this way, it is possible to avoid erroneous reception at UE-RX1.

[0310] Fig. 21 is a diagram showing an example of a preemption process by an S-UE according to the second embodiment. The horizontal axis indicates time, and the vertical axis indicates frequency. Fig. 21 shows a case in which an S-UE schedules resources scheduled for SL communication between UE-TX1 and UE-RX1 for SL communication between UE-TX2 and UE-RX2.

[0311] When the S-UE receives a scheduling request from UE-TX1, it performs resource reservation and scheduling for UE-TX1 and notifies UE-TX1 of the scheduling information. UE-TX1 performs scheduling for SL communication to UE-RX1 according to the received scheduling information, and performs SL communication. In FIG. 21, the resources scheduled for SL communication between UE-TX1 and UE-RX1 are indicated by diagonal lines.

[0312] The S-UE receives a scheduling request from UE-TX2. Having received the scheduling request, the S-UE determines the priority of the SL communication performed between UE-TX2 and UE-RX2. The S-UE may determine the priority based on the QoS of the service performed in the SL communication. If the S-UE determines that the priority of the SL communication performed between UE-TX2 and UE-RX2 is higher than the priority of the SL communication performed between UE-TX1 and UE-RX1 that was previously scheduled, the S-UE decides to schedule the resources scheduled for the SL communication between UE-TX1 and UE-RX1 for the SL communication between UE-TX2 and UE-RX2.

[0313] The S-UE determines the resources to be preempted for UE-TX2, performs scheduling for UE-TX2, and notifies UE-TX2 of the scheduling information.The S-UE also notifies UE-TX1 of the preemption information indicating that the already scheduled resources have been preempted.

[0314] UE-TX1, which has received the preemption information from S-UE, stops transmission to UE-RX1 using the preempted resource. UE-TX1 also notifies UE-RX1 of the preemption information indicating that the resource has been preempted. This allows UE-RX1 to avoid erroneous reception of the preempted resource for communication between other UEs.

[0315] UE-TX2, which has received the scheduling information from S-UE, performs scheduling for SL communication to UE-RX2 in accordance with the scheduling information, and performs SL communication.

[0316] In this way, it becomes possible to use resources scheduled for SL communication between UE-TX1 and UE-RX1 for SL communication between UE-TX2 and UE-RX2. SL communication between UE-TX2 and UE-RX2 can be performed with priority.

[0317] A method of transmitting PI from S-UE to UE-TX1 is disclosed. S-UE may transmit PI using SL communication with UE-TX1. PC5 link signaling may be used, or AS layer signaling may be used. For example, RRC signaling may be used. More information can be notified. Alternatively, MAC signaling may be used. Retransmission processing can improve reception quality. Alternatively, S-UE may include PI in SCI and transmit it on PSCCH. UE-TX1 can receive PI early. In this way, UE-TX1 can receive PI from S-UE.

[0318] The following (1) to (10) are disclosed as specific examples of information to be included in the PI transmitted from the S-UE to the UE-TX1.

[0319] (1) Information indicating that a resource will be preempted.

[0320] (2) Resource allocation information to be preempted.

[0321] (3) Information for identifying the destination UE.

[0322] (4) Information for identifying the source UE.

[0323] (5) Offset from PI reception to preemption resource.

[0324] (6) Information for identifying the destination UE of the SL communication to be preempted.

[0325] (7) Information for identifying the PC5 link of the SL communication to be preempted.

[0326] (8) Information for identifying the SL bearer of the SL communication to be preempted.

[0327] (9) Information for identifying the PC5 QoS flow of the SL communication to be preempted.

[0328] (10) A combination of (1) to (9) above.

[0329] The information in (2) may be, for example, information for identifying a frequency resource and a time resource. The frequency resource may be, for example, a subcarrier unit. The time resource may be, for example, a symbol unit, a minislot unit, or a slot unit.

[0330] The information (3) may be, for example, a UE identifier. The information (3) may be an identifier of UE-TX1. The information (3) may be a layer 2 ID (L2 ID) used by UE-TX1 in SL communication. Alternatively, the information (3) may be a layer 1 ID (L1 ID) used by UE-TX1 in SL communication.

[0331] The information (4) may be, for example, a UE identifier. The information (4) may be an identifier of the S-UE. The information (4) may be a Layer 2 ID (L2 ID) used by the S-UE in SL communication. Alternatively, the information (4) may be a Layer 1 ID (L1 ID) used by the S-UE in SL communication.

[0332] The information in (5) may be, for example, the minimum time until the preempted resource after UE-TX1 receives the PI from S-UE. Instead of time, SFN, slot number, or symbol number may be used. Also, when periodic resources are scheduled from S-UE to UE-TX1, the number of resources (counter), for example, the number of resources until the preempted resource, may be used.

[0333] The information (6) may be, for example, a UE identifier. The information (6) may be an identifier of UE-RX1. The information (6) may be a layer 2 ID (L2 ID) used by UE-RX1 in SL communication. Alternatively, the information (6) may be a layer 1 ID (L1 ID) used by UE-RX1 in SL communication.

[0334] UE-TX1 may notify S-UE of the processing capability of UE-TX1. The processing capability may be, for example, the time from receiving scheduling information for SL communication until scheduling becomes possible, or the time from receiving a PI until transmission can be stopped. Prior to preemption, UE-TX1 may notify S-UE of the processing capability of UE-TX1. S-UE may derive the above-mentioned offset using the processing capability received from UE-TX1. In this way, preemption taking into account the processing capability of UE-TX1 becomes possible.

[0335] The S-UE notifies UE-TX2 of scheduling information for SL communication to be performed with UE-RX2.

[0336] A method of transmitting a PI from UE-TX1 to UE-RX1 is disclosed. UE-TX1 may transmit the PI using SL communication with UE-RX1. The notification method may apply the above-mentioned method of transmitting a PI from S-UE to UE-TX1. A specific example of information to be included in the PI transmitted from UE-TX1 to UE-RX1 may also be applied. The offset in (5) above may be, for example, an offset to a preemption resource before UE-RX1 receives a PI from UE-TX1.

[0337] Fig. 22 is a diagram showing an example of a method of transmitting a PI from UE-TX1 to UE-RX1 according to the second embodiment. The horizontal axis indicates time, and the vertical axis indicates frequency. Fig. 22 shows a case where S-UE schedules the second slot of three slots scheduled for SL communication between UE-TX1 and UE-RX1 for SL communication between UE-TX2 and UE-RX2.

[0338] The first and third slots are used for SL communication between UE-TX1 and UE-RX1. The second slot is used by UE-TX2 to perform SL communication with UE-RX2 according to the scheduling information received from S-UE. UE-TX2 transmits SCI including scheduling information on PSCCH and transmits data on PSSCH. Also, UE-TX1 stops transmission to UE-RX1 in the second slot according to the PI received from S-UE.

[0339] The PI transmitted from UE-TX1 to UE-RX1 is transmitted on the PSCCH of the slot next to the preempted slot (the slot scheduled from UE-TX1 to UE-RX1). UE-TX1 transmits the PI on the PSCCH together with the SCI or includes the PI in the SCI. In this way, UE-RX1 can receive the PI from UE-TX1. By receiving the PI from UE-TX1, UE-RX1 can recognize that the second slot has been preempted for SL communication of another UE. UE-RX1 should discard the data received in the second slot. In this way, UE-RX1 can avoid erroneous reception.

[0340] Beam-related information may be notified together with scheduling information from UE-TX1 to UE-RX1 and from UE-TX2 to UE-RX2. The beam-related information includes information about beams from UE-TX to UE-RX, information about beams from UE-RX to UE-TX, and information about the correspondence between these beams. In this way, SL communication using beams between UE-TX and UE-RX is enabled.

[0341] By using the method disclosed in the second embodiment, it becomes possible for the S-UE to use resources scheduled for SL communication between certain UEs for SL communication between other UEs. By the S-UE performing preemption, it is possible to facilitate preemption processing in SL communication between multiple UEs, particularly in SL communication between UEs in which the UE-TX performing SL communication are different. Even when SL communication is performed between many UEs, it is possible to enable SL communication with low latency for V2X services that require low latency.

[0342] In addition, the UE-TX2 only needs to perform SL communication according to the normal scheduling notified by the S-UE. Therefore, the preemption process only needs to be performed in the UE-to-UE communication in which the scheduled resources are preempted. This makes it possible to avoid the preemption process becoming complicated.

[0343] Variation 1 of embodiment 2 In the first modification of the second embodiment, another method for solving the problem shown in the second embodiment will be disclosed.

[0344] UE-TX2 transmits information on preemption to UE-RX1. A method of transmitting PI is disclosed. PI may be transmitted using SL communication between UE-TX2 and UE-RX2. As a notification method, PI may be included in PSCCH and transmitted. UE-TX2 transmits PI by including it in PSCCH to be transmitted to UE-RX2. UE-TX1 may transmit PI by including it in PSCCH together with SCI for SL scheduling to UE-RX1. Alternatively, UE-TX1 may transmit PI in SCI on PSCCH. UE-TX1 may transmit PI by including it in PSCCH. As information to be included in PI, specific examples of information disclosed in the first embodiment may be applied.

[0345] A PSCCH that can be received by UEs performing SL communication is used as the PSCCH used for transmitting the PI. An SCI that can be received by UEs performing SL communication may be used as the SCI used for transmitting the PI. By using a PSCCH or SCI that can be received by UEs performing SL communication, rather than a PSCCH or SCI that can only be received by a specific UE (e.g., UE-RX2 performing SL communication with UE-TX2), for transmitting the PI, UE-RX1 that does not perform SL communication with UE-TX2 can receive the PI.

[0346] The S-UE notifies UE-TX2 of information on preemption. The preemption information notified by the S-UE to UE-TX2 may be information indicating that resources scheduled for SL communication of other UEs are to be preempted. The information may include resource allocation information of the resources to be preempted. As a method of notifying PI from the S-UE to UE-TX2, the PI notification method from the S-UE to UE-TX1 disclosed in the first embodiment may be appropriately applied.

[0347] The S-UE notifies the UE-TX2 of the scheduling information. The S-UE may transmit the PI together with the scheduling information or may include the PI in the scheduling information. In this way, the PI can be notified without increasing the amount of signaling from the S-UE to the UE-TX2.

[0348] By receiving the PI transmitted from the S-UE, the UE-TX2 can recognize which resource is the preempted resource. The UE-TX2 may notify the UE-RX1 of the information on the preemption by using the PI information. The notification of the PI from the UE-TX2 to the UE-RX1 may be performed by applying the above-mentioned method. In this way, the UE-RX1 can recognize that the already scheduled resource has been preempted.

[0349] Fig. 23 is a diagram showing an example of a method of transmitting a PI from UE-TX1 to UE-RX1 in accordance with the first modification of the second embodiment. The horizontal axis indicates time, and the vertical axis indicates frequency. Fig. 23 shows a case in which S-UE schedules the second slot of three slots scheduled for SL communication between UE-TX1 and UE-RX1 for SL communication between UE-TX2 and UE-RX2. Explanation of parts common to Fig. 22 will be omitted.

[0350] The S-UE transmits scheduling information of the second slot to be preempted to UE-TX2. The S-UE notifies UE-TX2 of preemption information (PI) indicating that the resource is a preempted resource together with the scheduling information. The S-UE may notify PI by including it in the scheduling information. In this way, UE-TX2 can recognize that the second slot is a preempted resource.

[0351] The second slot is used by UE-TX2 to perform SL communication with UE-RX2 according to the scheduling information received from the S-UE. UE-TX2 transmits SCI including scheduling information on the PSCCH, and transmits data on the PSSCH. UE-TX2 transmits PI for UE-RX1 together with the SCI or by including the SCI in the SCI. UE-TX2 transmits PI for UE-RX1 by including the PSCCH in the PSCCH. The PSCCH used for transmitting PI for UE-RX1 is a PSCCH that can be received by a UE performing SL communication.

[0352] In this way, UE-RX1 becomes able to receive the PI from UE-TX1. By receiving the PI from UE-TX1, UE-RX1 can recognize that the second slot has been preempted for SL communication between other UEs. UE-RX1 does not receive data in the second slot. In this way, UE-RX1 can avoid erroneous reception.

[0353] By using the method disclosed in the first modification of the second embodiment, it becomes possible for the S-UE to use resources scheduled for SL communication between certain UEs for SL communication between other UEs. By the S-UE performing preemption, it is possible to facilitate preemption processing in SL communication between multiple UEs, particularly in SL communication between UEs in which the UE-TX performing SL communication are different. Even when SL communication is performed between many UEs, it is possible to enable SL communication with low latency for V2X services that require low latency.

[0354] In addition, UE-RX1 can quickly recognize resources that have been preempted for SL communication between other UEs. This prevents UE-RX1 from receiving unnecessary data. This reduces the use of buffer capacity and discard processing for unnecessary received data, thereby preventing preemption processing in UE-RX1 from becoming complicated.

[0355] Another method for enabling the preemption process is disclosed. The S-UE may provide resources (PI resources) used for transmitting information related to preemption. The S-UE may notify the UE-TX of scheduling information of the PI resources. The PI resources may be, for example, periodic resources. For example, frequency and time resources may be used. The UE-TX receives the scheduling information of the PI resources. The UE-TX notifies the UE-RX of the scheduling information of the PI resources. The UE-RX receives the scheduling information of the PI resources. The UE-RX receives the PI resources using the received scheduling information of the PI resources.

[0356] The UE-TX transmits information about preemption to the UE-RX using the resources for PI. This allows the UE-RX receiving the resources for PI to receive the information about preemption from the UE-TX.

[0357] The UE-TX, whose already scheduled resources are to be preempted, may notify the UE-RX of information regarding preemption using the PI resources, so that the UE-RX, which is to be preempted, can receive the information regarding preemption.

[0358] The PI resource may be a resource that all UE-RX can receive, for example, a PSCCH, so that the preempted UE-RX can receive information about the preemption.

[0359] The S-UE may set the PI resource for each UE-TX individually. The PI resource can be set for each UE-TX. The S-UE may notify the PI resource for each UE-TX individually.

[0360] The S-UE may set the PI resources individually for each SL communication between the UE-TX and the UE-RX. The PI resources can be set for each SL communication between the UE-TX and the UE-RX. The S-UE may notify the UE-TX of the PI resources for each SL communication between the UE-TX and the UE-RX.

[0361] The UE-TX transmits information about preemption to the UE-RX using the individually set PI resource as described above. This allows the UE-RX receiving the PI resource to receive the preemption information from the UE-TX.

[0362] In this way, preemption processing is possible even when S-UE performs scheduling with other UEs. By providing PI resources, it is possible to reduce malfunctions in preemption processing between UE-TX and UE-RX. Even when SL communication is performed between many UEs, it is possible to enable low-latency SL communication for V2X services that require low latency.

[0363] In the method disclosed in the above-mentioned embodiment 2 and the first modification of the embodiment 2, the preemption process for multiple SL communications with different combinations of UE-TX and UE-RX is disclosed. These methods may be appropriately applied to the preemption process for multiple SL communications performed by one UE-TX. For example, these methods may be appropriately applied to the preemption process in the SL communication between UE-TX1 and UE-RX1 and the SL communication between UE-TX1 and UE-RX2. It is preferable to replace UE-TX2 with UE-TX1 in the above-mentioned disclosed method. The same effect can be obtained.

[0364] The methods disclosed in the above-mentioned second embodiment and the first modification of the second embodiment may be appropriately applied to the preemption process for a plurality of SL communications performed by one UE-RX. For example, these methods may be appropriately applied to the preemption process in the SL communications between UE-TX1 and UE-RX1 and the SL communications between UE-TX2 and UE-RX1. It is advisable to replace UE-RX2 with UE-RX1 in the above-mentioned disclosed methods. Similar effects can be obtained.

[0365] UE-TX2 may notify UE-RX1 of the PI together with the scheduling information. For example, in the first modification of the second embodiment, UE-TX2 is notified of the scheduling information and the PI from the S-UE. UE-TX2 may notify UE-RX1 of both the scheduling information and the PI. In this way, it becomes possible to perform the preemption process. It becomes possible to obtain the same effect.

[0366] As another method, UE-RX1 may receive scheduling from UE-TX2, and when the scheduled resources are the same as the resources scheduled by UE-TX1, determine that the previously scheduled resources have been preempted. In this way, UE-RX1 can receive data normally without mistaking data from UE-TX2 for data from UE-TX1.

[0367] The methods disclosed in the above-mentioned second embodiment and the first modification of the second embodiment may be appropriately applied to preemption processing targeting multiple SL communications between one UE-TX and one UE-RX. For example, these methods may be appropriately applied to preemption processing in different multiple SL communications between UE-TX1 and UE-RX1. In the above-mentioned disclosed methods, the SL communications between UE-TX1 and UE-RX1 and the SL communications between UE-TX2 and UE-RX2 may be replaced with different SL communications between UE-TX1 and UE-RX1, respectively. Similar effects can be obtained.

[0368] Embodiment 3 In SL communication, in addition to direct communication between UEs, indirect communication via a relay has been proposed (see Non-Patent Document 24). A relay between UEs may be called a UE-to-UE relay or an inter-UE relay. In this specification, a UE that performs inter-UE relay may be called a relay UE.

[0369] For example, when multiple UEs traveling in a convoy approach an intersection, direct communication between the UEs may not be possible due to blocking by a building. Also, a UE may need to communicate not only with nearby UEs but also with multiple UEs that are farther away. In such cases, a method using a UE-to-UE relay may be considered. However, in the conventionally proposed UE-to-UE relay, only unicast communication, which is one-to-one communication, is applied to communication from the transmitting UE (UE-TX) to the relay UE and from the relay UE to the receiving UE (UE-RX). This causes a problem in that communication with multiple UEs is not possible.

[0370] In the third embodiment, a method for solving such problems will be disclosed.

[0371] Groupcast communication is performed in a relay between UEs. A UE performs groupcast communication with multiple UEs via a relay UE. A communication method between UE-TX and relay UE may be different from a communication method between relay UE and UE-RX. As a specific method, unicast communication is performed between UE-TX and relay UE, and groupcast communication is performed between relay UE and multiple UE-RX. In this way, communication is performed from UE-TX to multiple UE-RX via relay UE.

[0372] 24 is a conceptual diagram showing a conventional example in which unicast communication is performed between UE-TX and UE-RX via a relay UE. Unicast communication is performed between UE-TX and relay UE, and unicast communication is also performed between relay UE and UE-RX.

[0373] FIG. 25 is a conceptual diagram showing an example of performing groupcast communication between UE-TX and multiple UE-RX via a relay UE in the third embodiment. Unicast communication is performed between UE-TX and the relay UE, and groupcast communication is performed between the relay UE and multiple UE-RX. In this way, communication is performed from UE-TX to multiple UE-RX via the relay UE.

[0374] A detailed method for a UE to perform groupcast communication with multiple UEs via a relay UE is disclosed. The relay UE broadcasts information on communication methods that the relay UE can implement. By broadcasting information on communication methods that the relay UE can implement, rather than information simply indicating that relaying is possible, other UEs that receive the information can recognize communication methods that the relay UE can implement. The relay UE may transmit information on communication methods that the relay UE can implement to a specific UE. This is effective, for example, when the relay UE recognizes the UE that transmits the information.

[0375] As a method of transmitting the information to a specific UE, the notification may be performed by PC5 signaling between the specific UE and the relay UE, the notification may be performed when a PC5 link is established or after the establishment, or the notification may be performed by RRC signaling, or the notification may be performed when an RRC connection is established or after the establishment.

[0376] The information on the communication method includes, for example, unicast communication, groupcast communication, broadcast communication, and the like.

[0377] The relay UE may report V2X service information that the relay UE can implement. Alternatively, the relay UE may transmit the information to a specific UE. The V2X service information may be associated with information on the communication method. The association is not limited to one-to-one, but may be one-to-many, many-to-one, or many-to-many. By associating, it is possible to specify and indicate the communication method in the V2X service, for example, unicast communication is possible in V2X service #1 and groupcast communication is possible in V2X service #2.

[0378] The relay UE may report information on the number of UEs and the number of groups that the relay UE can operate. Alternatively, the relay UE may transmit the information to a specific UE. The V2X service information may be associated with information on the communication method. For example, the information may be the number of UEs that can be communicated in unicast communication, or the number of groups that can be communicated in groupcast communication. In this way, the UE-TX can recognize the number of UEs and the number of groups that the relay UE can operate.

[0379] Information about relaying may be provided as a capability of the UE. The information may be, for example, the above-mentioned available communication method, the number of UEs or groups that can perform relaying, etc. The number of UEs or groups that can perform relaying may be a maximum value. For example, the capability may be notified to other UEs, S-UEs, or gNBs. In this way, the above-mentioned nodes can recognize the capability of the relay UE.

[0380] The relay UE may report the number of UEs or groups that the relay UE can relay, minus the number of UEs or groups that have already performed relaying, from the maximum number of UEs or groups that the relay UE can perform relaying. Alternatively, the relay UE may transmit the information to a specific UE. In this way, the UE-TX can detect UEs that can perform relaying.

[0381] The UE-TX notifies the relay UE of information on the communication method when relaying. For example, when the UE-TX requests groupcast communication from the relay UE, the UE-TX transmits a request for UE-to-UE relay to the relay UE. The UE-TX notifies the relay UE of information on the communication method when relaying by including the information in the request for UE-to-UE relay to be transmitted to the relay UE. It is preferable to set groupcast communication as information on the communication method for requesting groupcast communication. In this way, the UE-TX can request the relay UE of the communication method between the relay UE and UE-RX. The relay UE may also set the received communication method. In this way, the UE-TX can set the communication method between the relay UE and UE-RX.

[0382] The UE-TX notifies the relay UE of information for identifying the SL communication destination. Unlike direct communication between UEs, the final SL communication destination is not the relay UE but the UE-RX. Therefore, the relay UE needs to identify the destination to be relayed. Therefore, it is recommended that the UE-TX notify the relay UE of information for identifying the SL communication destination.

[0383] Also, unlike unicast communication, the information for identifying the SL communication destination may be information for identifying a group of SL communication destinations. For example, when the UE-TX requests groupcast communication from the relay UE, the UE-TX notifies the relay UE of information for identifying the SL communication destination by including it in a request for UE-to-UE relay to be transmitted to the relay UE. Alternatively, the UE-TX may notify the relay UE of the information in a process for establishing a PC5 link. Alternatively, the UE-TX may notify the relay UE of the information when performing a UE-to-UE relay service.

[0384] As information for identifying the SL communication destination, for example, a destination group identifier may be used. A layer 2 (L2) destination group identifier may be used. In this way, the UE-TX can transmit the communication destination to be group-cast in the SL communication to the relay UE. Also, the relay UE can recognize the SL communication destination. The relay UE can perform relaying to the group of SL communication destinations.

[0385] By receiving the destination group identifier, the relay UE may determine to perform group cast communication when relaying. The UE-TX may transmit the destination group identifier to the relay UE instead of the information notified as the communication method when relaying. The relay UE may determine whether to perform group cast using the destination group identifier. This can reduce the notification of the communication method when relaying from the UE-TX to the relay UE.

[0386] The relay UE notifies the UE-RX of information for identifying the source of the SL communication. Unlike direct communication between UEs, the source of the SL communication is the UE-TX, not the relay UE. By notifying the UE-RX of information for identifying the source of the SL communication, the UE-RX can recognize the source of the relayed data.

[0387] Figures 26 and 27 are sequence diagrams showing an example of performing groupcast communication between UE-TX and multiple UE-RX via a relay UE according to the third embodiment. Figures 26 and 27 are connected at the position of a boundary line BL2627. Unicast communication is performed between UE-TX and the relay UE, and groupcast communication is performed between the relay UE and multiple UE-RX. In this way, communication is performed from UE-TX to multiple UE-RX via the relay UE.

[0388] The UE-TX detects UEs capable of relaying groupcast communication. To enable the detection, the relay UE broadcasts information on the communication methods that the relay UE can implement. In the method disclosed in Fig. 26 and Fig. 27, the relay UE uses a discovery process (see Non-Patent Document 22) to broadcast information on the communication methods that the relay UE can implement.

[0389] Step ST2303 is a sequence in the case where the discovery process of model A is used. In step ST2304, the relay UE1 judges whether or not it can relay groupcast communication. The relay UE1 may make the judgment in step ST2304 based on the capability of the relay UE1 itself. In step ST2305, the relay UE1 broadcasts an announcement message. The relay UE1 broadcasts information on the communication method that can be relayed by including it in the announcement message. For example, if the relay UE1 can relay groupcast communication, the relay UE1 may notify information indicating that it can relay groupcast communication by including it in the announcement message. The communication method to be notified is not limited to one, and may be multiple. For example, if the relay UE1 can relay unicast communication and groupcast communication, the relay UE1 may notify information indicating that it can relay unicast communication and groupcast communication by including it in the announcement message.

[0390] Step ST2306 is a sequence for the case where the discovery process of model B is used. In Step ST2307, the UE-TX broadcasts a solicitation message to detect a relay capable of relaying groupcast communication. The UE-TX may include information requesting relay of groupcast communication in the solicitation message.

[0391] In Step ST2308, relay UE1 judges whether or not it can relay groupcast communication. In Step ST2309, relay UE1 notifies UE-TX of a response message. UE-TX may include an identifier of the source UE in the solicitation message. The identifier of the source UE may be, for example, a layer 2 ID. Relay UE1 may use the identifier of the source UE included in the solicitation message to judge which UE-TX to notify of the response message.

[0392] The relay UE 1 transmits the response message including information on the communication method that can be relayed. For example, if the relay UE 1 can relay groupcast communication, the relay UE 1 may notify the response message including information indicating that the groupcast relay communication is possible. The communication method to be notified is not limited to one, and may be multiple.

[0393] By receiving the announce message of step ST2305 or the response message of step ST2309, the UE-TX can obtain information on the communication method that can be relayed, which is included in these messages. The UE-TX can recognize the communication method that the relay UE1 can relay. For example, when the UE-TX receives information that the groupcast communication can be relayed from a plurality of relay UEs, the UE-TX selects one relay UE. For example, the communication quality between the UE-TX and the relay UE may be used as the selection index. The SL RSRP or RSRQ may be used as the communication quality. Also, for example, the distance between the UE-TX and the relay UE may be used as the selection index.

[0394] In step ST2310, the UE-TX notifies the selected relay UE (relay UE1 in Figs. 26 and 27) of information on the communication method when performing relaying. In this embodiment 3, group cast communication is exemplified as the communication method when performing relaying. The UE-TX may notify information on the communication method when performing relaying by including it in a communication request message for starting unicast communication between UEs. The UE-TX can request or set relaying in group cast communication by transmitting information on the communication method when performing relaying to relay UE1.

[0395] In step ST2311, the UE-TX establishes a connection for unicast communication with the relay UE1. The connection establishment may be the establishment of a PC5 link or may be the establishment of an RRC connection in SL. In step ST2312, the UE-TX transmits data to be relayed by a service using SL communication to the relay UE1. The data communication of the service is unicast communication between the UE-TX and the relay UE1.

[0396] At this time, the UE-TX may transmit the identifier of the final SL communication destination to the relay UE 1. In the third embodiment, since groupcast is performed from the relay UE 1 to the final communication destination, the identifier of the final SL communication destination may be a group identifier. The group identifier may be a layer 2 communication destination group identifier.

[0397] As a method of transmitting the identifier of the final SL communication destination from the UE-TX to the relay UE1, the notification may be made by PC5 signaling between the UE-TX and the relay UE. The notification may be made when or after the PC5 link is established. Alternatively, the notification may be made by RRC signaling. The notification may be made when or after the RRC connection is established. As another method, the notification may be made by SL MAC signaling. For example, the notification may be made by providing information of the final SL communication destination as a CE of the SL MAC. As another method, the notification may be made by L1 signaling. For example, the notification may be made by providing information of the final SL communication destination in the SCI and on the PSCCH.

[0398] In step ST2313, the relay UE1 transmits the data of the service using the SL communication received from the UE-TX to the final communication destination by groupcast communication. When performing groupcast communication, the relay UE1 may set the identifier of the final SL communication destination group received from the UE-TX as the identifier of the communication destination. Also, when performing groupcast communication, the relay UE1 may transmit the identifier of the UE-TX.

[0399] The UE-RX receives the relayed data when the identifier of the final destination group for the data relayed by the service using SL communication matches the identifier of the SL destination group corresponding to the SL communication service that the UE-RX desires to receive. In this way, the UE-RX can receive the data that has been groupcast communicated from the UE-TX via the relay UE1.

[0400] Furthermore, the UE-RX can identify the source of the groupcast communication by receiving the identifier of the UE-TX for the data relayed by the service using the SL communication.

[0401] In this way, groupcast communication can be performed from UE-TX to multiple UE-RX via the relay UE.

[0402] FIG. 28 is a sequence diagram showing another example of performing groupcast communication between UE-TX and multiple UE-RX via a relay UE, according to the third embodiment. Unicast communication is performed between UE-TX and relay UE, and groupcast communication is performed between relay UE and multiple UE-RX. In this way, communication is performed from UE-TX to multiple UE-RX via relay UE. In FIG. 28, steps common to FIG. 26 and FIG. 27 are assigned the same step numbers, and common explanations are omitted.

[0403] 26 and 27 disclose examples using the discovery process. FIG. 28 discloses an example not using the discovery process. In Step ST2401, the UE-TX broadcasts information on the communication method when performing relaying. Here, group cast communication is illustrated as an example of the communication method when performing relaying. The UE-TX may broadcast information on the communication method when performing relaying by including it in a communication request message for starting unicast communication between UEs. The UE-TX can request or set relaying in group cast communication by transmitting information on the communication method when performing relaying to the relay UE1.

[0404] The UE-TX may report a communication destination identifier indicating that the destination is a relay together with information on the communication method when relaying. The UE-TX may report the communication destination identifier indicating that the destination is a relay by including it in a communication request message for starting unicast communication between UEs. The communication destination identifier indicating that the destination is a relay may be an identifier of the L2 layer. The communication destination identifier indicating that the destination is a relay may be statically determined in advance by a standard or the like. Alternatively, the communication destination identifier indicating that the destination is a relay may be configured in advance in the UE, for example, may be set in the SIM. Alternatively, the communication destination identifier indicating that the destination is a relay may be provided from the CN as a V2X policy / parameter. Alternatively, the communication destination identifier indicating that the destination is a relay may be provided from another service function, for example, a service function such as a proximity service. The relay UE1 can receive a communication request message for starting unicast communication between UEs addressed to the relay UE by using the communication destination identifier.

[0405] When the relay UE receives a communication request message for starting unicast communication between UEs in Step ST2401, the relay UE judges in Step ST2403 whether or not it can relay groupcast communication. The relay UE1 may make the judgment in Step ST2403 based on the capability of the relay UE1 itself. If the relay UE1 judges that it can relay groupcast communication, it notifies the UE-TX of an inter-UE unicast communication request response message in Step ST2405. The relay UE1 may use the identifier of the source UE included in the inter-UE unicast communication request message to judge to which UE-TX to notify the inter-UE unicast communication request response message.

[0406] The relay UE 1 transmits information about the communication method that can be relayed in a response message for the unicast communication request between UEs. For example, if the relay UE 1 can relay groupcast communication, the relay UE 1 may transmit information indicating that it can relay groupcast communication in a response message for the unicast communication request between UEs. The communication method to be notified is not limited to one, and may be multiple.

[0407] The UE-TX may determine that unicast communication with the relay UE1 has been established by receiving an inter-UE unicast communication request response message from the relay UE1. When the UE-TX receives information indicating that groupcast communication can be relayed from multiple relay UEs, the UE-TX selects one relay UE. For example, the communication quality between the UE-TX and the relay UE may be used as the selection index. For example, SL RSRP or RSRQ may be used as the communication quality. Also, for example, the distance between the UE-TX and the relay UE may be used as the selection index.

[0408] In step ST2312, the UE-TX transmits data to be relayed by the service using SL communication to the relay UE1 with which unicast communication has been established. The data communication for the service is unicast communication between the UE-TX and the relay UE1. In step ST2313, the relay UE1 transmits the data for the service using SL communication received from the UE-TX to the final destination by groupcast communication. When performing groupcast communication, the relay UE1 may set the identifier of the final SL communication destination group received from the UE-TX as the identifier of the destination. Furthermore, the relay UE1 may transmit the identifier of the UE-TX when performing groupcast communication.

[0409] Using the identifier of the SL communication destination group corresponding to the SL communication service that the UE-RX desires to receive, the UE-RX receives the data that has been group-cast communicated from the UE-TX via the relay UE 1. The UE-RX may also identify the source of the group-cast communication by receiving the identifier of the UE-TX for the data relayed by the service using the SL communication.

[0410] In this way, groupcast communication from UE-TX to multiple UE-RX is possible via the relay UE. For example, when UE-TX performs groupcast communication to a group consisting of multiple UEs, it is possible to expand the range between UE-TX and multiple UE-RX that can communicate with each other by performing groupcast communication via a relay. Also, even if there is an obstacle between UE-TX and UE-RX, it is possible to improve the communication quality between UE-TX and multiple UE-RX by performing groupcast communication via a relay.

[0411] In the examples disclosed in Fig. 24 to Fig. 27, a case where one relay UE is used is shown. The method disclosed in the third embodiment is not limited to the case where one relay UE is used, and multiple relay UEs may be used. Unicast communication may be set between UE-TX and multiple UEs, and relaying by groupcast communication may be performed between multiple relay UEs and multiple UE-RX. In this way, groupcast communication can be performed to UE-RX that is farther away than the UE-RX.

[0412] The UE-TX may determine whether to perform relaying. When the UE-TX determines to perform relaying, the above-mentioned method may be applied to the relay UE as appropriate. For example, the distance between the UE-TX and the UE-RX may be used as an index for determining whether the UE-TX performs relaying. When a predetermined distance is exceeded, it may be determined to use a relay UE. For example, the reception quality (which may be reception power) from the UE-TX in the UE-RX may be used. When the reception power falls below a predetermined reception power, it may be determined to use a relay UE. For example, the radio wave propagation delay time from the UE-TX in the UE-RX may be used. When a predetermined radio wave propagation delay time is exceeded, it may be determined to use a relay UE. For example, the number of Nacks from the UE-RX may be used. When the number of Nacks exceeds a predetermined number, it may be determined to use a relay UE.

[0413] Variation 1 of embodiment 3 In the first modification of the third embodiment, another method for solving the problem shown in the third embodiment will be disclosed.

[0414] Groupcast communication is performed in a relay between UEs. A UE performs groupcast communication with multiple UEs via a relay UE. A communication method between UE-TX and a relay UE may be different from a communication method between a relay UE and UE-RX. As a specific method, groupcast communication is performed between UE-TX and a relay UE, and unicast communication is performed between the relay UE and multiple UE-RX. In this way, communication is performed from UE-TX to multiple UE-RX via the relay UE.

[0415] FIG. 29 is a conceptual diagram showing an example of performing groupcast communication between UE-TX and multiple UE-RX via a relay UE in the first modification of the third embodiment. Groupcast communication is performed between UE-TX and the relay UE, and unicast communication is performed between the relay UE and multiple UE-RX. In this way, communication is performed from UE-TX to multiple UE-RX via the relay UE.

[0416] The relay UE receives groupcast communication that the relay UE can relay. For example, the relay UE receives information for identifying a SL destination group of the groupcast communication, and receives the groupcast communication when the received information matches the destination identification information of the V2X service using the groupcast communication that the relay UE can relay. In this way, the relay UE can receive data transmitted by groupcast from the UE-TX.

[0417] When a relay UE receives information for identifying an SL destination group for groupcast communication, the relay UE uses the information for identifying the SL destination group to relay the received data to the SL destination group.

[0418] When communication between the relay UE and UE-RX is unicast communication, the relay UE may detect the UE-RX using information for identifying the SL communication destination group. When the UE-RX receives information for identifying the desired SL communication destination group, it may establish a PC5 link with the relay UE and perform unicast communication. The number of UE-RX that performs unicast communication with the relay UE may be one or more. In this way, groupcast communication from the UE-TX to the UE-RX is possible.

[0419] FIG. 30 and FIG. 31 are sequence diagrams showing an example of performing groupcast communication between UE-TX and multiple UE-RX via a relay UE in the first modification of the third embodiment. FIG. 30 and FIG. 31 are connected at the position of a boundary line BL3031. Groupcast communication is performed between UE-TX and relay UE, and unicast communication is performed between relay UE and multiple UE-RX. In this way, communication is performed from UE-TX to multiple UE-RX via relay UE. In the example of FIG. 30 and FIG. 31, a discovery process is used between relay UE and UE-RX.

[0420] In step ST2604, the UE-TX, in which data for a service using SL communication has been generated, performs groupcast communication in SL. When performing groupcast communication, the UE-TX notifies information on a communication method for relaying. In the first modification of the third embodiment, unicast communication is exemplified as a communication method for relaying. In this manner, it becomes possible to request or set relaying in unicast communication.

[0421] In the groupcast communication in step ST2604, the UE-TX may transmit the identifier of the communication destination by including it in information on the communication method when relaying. The method of setting the identifier of the communication destination in the SL communication between the UE-TX and the relay UE1 disclosed in the third embodiment may be appropriately applied as the method of setting the identifier of the communication destination. In this way, the relay UE becomes able to receive the groupcast communication from the UE-TX.

[0422] In the examples of Fig. 30 and Fig. 31, another method is disclosed. A relay UE derives an identifier of a communication destination corresponding to a service that the relay UE can relay. The derivation method may be statically determined in advance by a standard or the like. Alternatively, the derivation method may be configured in advance in the UE, for example, set in the SIM. Alternatively, the derivation method may be provided by the CN as a V2X policy / parameter. Alternatively, the derivation method may be provided by another service function, for example, a service function such as a proximity service.

[0423] In step ST2604, the UE-TX performs groupcast communication. In the groupcast communication, the UE-TX may set an identifier of a destination group corresponding to a service using SL communication as an identifier of the destination. The identifier of the destination group may be an identifier of the L2 layer. The relay UE receives data when the identifier of the final destination group for data of a service using SL communication transmitted from the UE-TX matches the identifier of a destination group corresponding to an SL communication service that the relay UE can relay. In this way, the relay UE can receive data transmitted by groupcast communication from the UE-TX.

[0424] In steps ST2607 and ST2608, the relay UE judges whether or not relaying is possible using the communication method received in step ST2604. The relay UE may make this judgment based on its own relay UE's capability. If relaying is possible using the received communication method, the relay UE decides to relay in steps ST2614 and ST2616. If relaying is not possible using the received communication method, the relay UE decides not to relay in steps ST2613 and ST2615. The examples in Figures 30 and 31 disclose the case where relay UE1 and relay UE2 decide to relay.

[0425] In Step ST2609, the relay UE 1 performs a discovery process to detect UEs performing unicast communication. Step ST2609 is a case in which mode A is used. In Step ST2617, the relay UE 1 transmits an announce message. The relay UE 1 may set, in the announce message, an identifier of a communication destination group corresponding to a service using SL communication as an identifier of the communication destination.

[0426] In Step ST2611, the relay UE1 may perform a discovery process to detect a UE performing unicast communication. Step ST2611 corresponds to the case where Mode B is used. In Step ST2610, the UE-RX transmits a solicitation message. The UE-RX may set, in the message, an identifier of a communication destination group corresponding to a service using SL communication. Furthermore, the UE-RX may include, in the message, information requesting relay of the service.

[0427] When the relay UE1 receives a solicitation message from the UE-RX1, the relay UE1 uses an identifier of a communication destination group corresponding to a service using SL communication and information requesting relaying, which are included in the message, to determine to perform unicast communication with the UE-RX1. For example, when the relay UE1 receives solicitation messages from multiple UE-RXs, the relay UE1 may select one UE-RX. For example, the communication quality between the relay UE and the UE-RX may be used as the selection index. For example, the SL RSRP or RSRQ may be used as the communication quality. In addition, for example, the distance between the relay UE and the UE-RX, the radio wave propagation delay time, or the number of Nacks may be used as the selection index.

[0428] The relay UE1 may select multiple UE-RXs instead of one UE-RX. The relay UE1 may perform unicast communication with each UE-RX. The relay UE1 may relay SL communication data from UE-TX to each UE-RX by using unicast communication. In FIG. 30 and FIG. 31, the relay UE1 decides to perform unicast communication with UE-RX1. In step ST2618, the relay UE1 notifies UE-RX1 of a response message.

[0429] When the UE-RX receives response messages from multiple relay UEs, it may select one relay UE. As a selection index, for example, the communication quality, distance, radio wave propagation delay time, or number of Nacks between the relay UE and the UE-RX may be used as described above.

[0430] The UE-RX may select multiple relay UEs. The UE-RX may connect to multiple relay UEs. The UE-RX receives data from the UE-TX via multiple relay UEs. In this way, redundancy of the communication path is obtained. Therefore, the reliability of groupcast communication from the UE-TX to the UE-RX can be improved.

[0431] When the UE-RX receives the same data from multiple relay UEs, it may leave one of the data and discard the other data. For example, the UE-RX may leave the first successfully received data and discard the data received after that. The determination of whether the data is the same or not may be performed, for example, using a sequence number (SN) assigned to the data by PDCP of the UE-TX. The data may be determined to be the same when the SNs overlap. Alternatively, a sequence number may be assigned to the V2X packet and the determination may be performed using the sequence number. The data may be determined to be the same when the sequence numbers of the V2X packets overlap. Alternatively, the determination may be performed using a QoS flow identifier and an SN assigned by PDCP. The data may be determined to be the same when both the QoS flow identifier and the SN assigned by PDCP overlap. In this way, the UE-RX can discard data received later. Even if the UE-RX is connected to multiple relay UEs, it is possible to receive group cast communication data from the UE-TX.

[0432] In Step ST2619, UE-RX1 transmits a communication request message for starting unicast communication between UEs to the selected relay UE (relay UE1 in Figs. 30 and 31). UE-RX1 may notify information requesting relaying by including it in the message. Furthermore, UE-RX1 may notify an identifier of a destination group corresponding to a service using SL communication and an identifier of its own UE-RX1 by including it in the message. These identifiers may be identifiers of the L2 layer.

[0433] In Step ST2620, relay UE1 establishes a connection for unicast communication with UE-RX. The connection establishment may be the establishment of a PC5 link or may be the establishment of an SL RRC connection. In Step ST2621, relay UE1 relays data of a service using SL communication received from UE-TX to UE-RX1. The relay transmission of the data of the service is unicast communication between relay UE1 and UE-RX1.

[0434] In step ST2621, relay UE1 transmits data of the service using SL communication received from UE-TX to UE-RX1 by unicast communication. When relay UE1 performs unicast communication with UE-RX1, relay UE1 may set the identifier of UE-RX1 as the identifier of the communication destination. Alternatively, relay UE1 may set the identifier of the final SL communication destination group received from UE-TX as the identifier of the communication destination. Furthermore, relay UE1 may transmit the identifier of UE-TX when performing groupcast communication.

[0435] In the relayed SL communication, UE-RX1 may receive data whose destination is its own identifier UE-RX1. Alternatively, UE-RX1 may receive the relayed data when the identifier of the final destination group for the data relayed by the service using SL communication matches the identifier of the SL destination group corresponding to the SL communication service that UE-RX1 desires to receive. In this way, UE-RX can receive data that is group-cast communicated from UE-TX via relay UE1.

[0436] Furthermore, UE-RX1 is able to identify the source of the groupcast communication by receiving the identifier of UE-TX for the data relayed by the service using the SL communication.

[0437] When relay UE2 decides to relay groupcast communication from UE-TX, in steps ST2622 to ST2627, it performs discovery processing and connection establishment for unicast communication with UE-RX (UE-RX4 in Figs. 30 and 31), and relays data of the service using SL communication received from UE-TX. The relay transmission of the data of the service is unicast communication between relay UE2 and UE-RX4. These are the same as the method in the case of relay UE1 described above.

[0438] In this way, groupcast communication from UE-TX to multiple UE-RXs is possible via the relay UE.

[0439] FIG. 32 and FIG. 33 are sequence diagrams showing another example of performing groupcast communication between UE-TX and multiple UE-RX via a relay UE in the first modification of the third embodiment. FIG. 32 and FIG. 33 are connected at the position of the boundary line BL3233. Unicast communication is performed between UE-TX and relay UE, and groupcast communication is performed between relay UE and multiple UE-RX. In this way, communication is performed from UE-TX to multiple UE-RX via relay UE. In FIG. 32 and FIG. 33, steps common to FIG. 30 and FIG. 31 are assigned the same step numbers, and common explanations are omitted.

[0440] In Fig. 30 and Fig. 31, an example in which the discovery process is used between the relay UE and UE-RX is disclosed. In Fig. 32 and Fig. 33, an example in which the discovery process is not used is disclosed. When the RIRE-UE1 decides to relay the groupcast communication from the UE-TX in Step ST2614, the RIRE-UE1 broadcasts a communication request message for starting unicast communication between UEs in Step ST2701. The relay UE1 may notify information indicating that the relay will be performed by including it in the communication request message. In addition, the relay UE1 may notify an identifier of a destination group corresponding to a service using SL communication and an identifier of its own relay UE1 by including it in the communication request message. These identifiers may be identifiers of the L2 layer.

[0441] When UE-RX (UE-RX1 in Figures 32 and 33) receives a communication request message from relay UE1 to start UE-to-UE unicast communication, if the identifier of the destination group corresponding to a service using SL communication contained in the message matches the identifier of the SL destination group corresponding to the SL communication service that the UE-RX wishes to receive, it decides to perform UE-to-UE unicast communication with relay UE1.

[0442] In step ST2702, UE-RX1 notifies relay UE1 of an inter-UE unicast communication request response message. By receiving the inter-UE unicast communication request response message from UE-RX1, relay UE1 may determine that a connection for unicast communication with UE-RX1 has been established. The connection establishment may be the establishment of a PC5 link or the establishment of an SL RRC connection. When relay UE1 receives inter-UE unicast communication request response messages from multiple UE-RX1, relay UE1 may select one UE-RX or multiple UE-RX. When relay UE1 selects multiple UE-RX, relay UE1 may perform unicast communication with each UE-RX. The aforementioned index may be applied as a selection index.

[0443] In Step ST2703, relay UE1 relays data of the service using SL communication received from UE-TX to UE-RX1. The relay transmission of the data of the service is performed by unicast communication between relay UE1 and UE-RX1.

[0444] In step ST2703, relay UE1 transmits data of the service using SL communication received from UE-TX to UE-RX1 by unicast communication. When relay UE1 performs unicast communication with UE-RX1, relay UE1 may set the identifier of UE-RX1 as the identifier of the communication destination. Alternatively, relay UE1 may set the identifier of the final SL communication destination group received from UE-TX as the identifier of the communication destination. Furthermore, relay UE1 may transmit the identifier of UE-TX when performing groupcast communication.

[0445] In the relayed SL communication, UE-RX1 may receive data whose destination is its own identifier UE-RX1. Alternatively, UE-RX1 may receive the relayed data when the identifier of the final destination group for the data relayed by the service using SL communication matches the identifier of the SL destination group corresponding to the SL communication service that UE-RX1 desires to receive. In this way, UE-RX can receive data that is group-cast communicated from UE-TX via relay UE1.

[0446] Furthermore, UE-RX1 is able to identify the source of the groupcast communication by receiving the identifier of UE-TX for the data relayed by the service using the SL communication.

[0447] When relay UE2 decides to relay groupcast communication from UE-TX, in steps ST2704 to ST2706, relay UE2 establishes a connection for unicast communication with UE-RX (UE-RX4 in Figs. 32 and 33) and relays data of the service using SL communication received from UE-TX. The relay transmission of the data of the service is unicast communication between relay UE2 and UE-RX4. These are the same as the method in the case of relay UE1 described above.

[0448] In this way, groupcast communication from UE-TX to multiple UE-RX is possible via the relay UE. For example, when UE-TX performs groupcast communication to a group consisting of multiple UEs, it is possible to expand the range between UE-TX and multiple UE-RX that can communicate with each other by performing groupcast communication via a relay. Also, even if there is an obstacle between UE-TX and UE-RX, it is possible to improve the communication quality between UE-TX and multiple UE-RX by performing groupcast communication via a relay.

[0449] In addition, by using groupcast communication between UE-TX and relay UE, even if communication quality between one UE-TX and relay UE is poor and communication is interrupted, groupcast communication from UE-TX to UE-RX in the group can be performed using another relay UE. This makes it possible to improve the redundancy and reliability of groupcast communication in SL.

[0450] Variation 2 of embodiment 3 In the second modification of the third embodiment, another method for solving the problem shown in the third embodiment will be disclosed.

[0451] Groupcast communication is performed in a relay between UEs. A UE performs groupcast communication with multiple UEs via a relay UE. The communication method between UE-TX and relay UE may be the same as the communication method between relay UE and UE-RX. As a specific method, groupcast communication is performed between UE-TX and relay UE, and groupcast communication is performed between relay UE and multiple UE-RX. In this way, communication is performed from UE-TX to multiple UE-RX via relay UE.

[0452] FIG. 34 is a conceptual diagram showing an example of performing groupcast communication between UE-TX and multiple UE-RX via a relay UE in the second modification of the third embodiment. Groupcast communication is performed between UE-TX and the relay UE, and groupcast communication is performed between the relay UE and multiple UE-RX. In this way, communication is performed from UE-TX to multiple UE-RX via the relay UE.

[0453] The relay UE receives groupcast communication that it can relay. As a method for receiving the groupcast communication, the method disclosed in the first modification of the third embodiment may be appropriately applied. The relay UE becomes able to receive data transmitted by the UE-TX via groupcast.

[0454] When a relay UE receives information for identifying an SL destination group for groupcast communication, the relay UE uses the information for identifying the SL destination group to relay the received data to the SL destination group.

[0455] The relay UE performs groupcast communication with UE-RX for UE-to-UE relay. Since the relay UE judges whether to perform groupcast communication with UE-RX, the method disclosed in the first modification of the third embodiment may be applied as appropriate. The relay UE may judge whether to perform groupcast communication with UE-RX by using information on the communication method notified from UE-TX. As another method, when the relay UE receives information for identifying the SL destination group of the groupcast communication from UE-TX, the relay UE may judge to perform groupcast communication with UE-RX.

[0456] When the communication between the relay UE and UE-RX is groupcast communication, the relay UE transmits information for identifying the SL communication destination group. The UE-RX receives information for identifying the SL communication destination group of the groupcast communication, and receives the groupcast communication when the received information matches the destination identification information corresponding to the V2X service using the desired groupcast communication. In this way, the UE-RX can receive data transmitted by groupcast from the UE-TX via the relay UE.

[0457] FIG. 35 is a sequence diagram showing an example of performing groupcast communication between UE-TX and multiple UE-RX via a relay UE in the second modification of the third embodiment. Groupcast communication is performed between UE-TX and the relay UE, and groupcast communication is performed between the relay UE and multiple UE-RX. In this way, communication is performed from UE-TX to multiple UE-RX via the relay UE. In FIG. 35, steps common to FIG. 26, FIG. 27, FIG. 30, and FIG. 31 are assigned the same step numbers, and common explanations are omitted.

[0458] In step ST2902, the UE-TX, in which data for a service using SL communication has been generated, performs groupcast communication in SL. When performing groupcast communication, the UE-TX notifies information on the communication method for relaying. In the second modification of the third embodiment, groupcast communication is exemplified as a communication method for relaying. In this way, it becomes possible to request or set relaying in groupcast communication. As the communication method for relaying, the method disclosed in the above-mentioned step ST2604 may be appropriately applied. In this way, the relay UE becomes able to receive data transmitted by groupcast communication from the UE-TX.

[0459] In Steps ST2607 and ST2608, the relay UE judges whether or not relaying is possible using the communication method received in Step ST2604.

[0460] When relay UE1 and relay UE2 decide to relay groupcast communication from UE-TX, they relay data of the service using SL communication received from UE-TX in steps ST2312 and ST2903. The relay transmission of the data of the service is broadcast communication between relay UE and UE-RX. These methods are the same as those in the case of relay UE1 described above. The method disclosed in step ST2312 described above may be applied as appropriate to these communication methods.

[0461] In this way, groupcast communication from UE-TX to multiple UE-RX is possible via the relay UE. For example, when UE-TX performs groupcast communication to a group consisting of multiple UEs, it is possible to expand the range between UE-TX and multiple UE-RX that can communicate with each other by performing groupcast communication via a relay. Also, even if there is an obstacle between UE-TX and UE-RX, it is possible to improve the communication quality between UE-TX and multiple UE-RX by performing groupcast communication via a relay.

[0462] In addition, by using groupcast communication for communication between UE-TX and relay UE, even if communication quality between one UE-TX and relay UE is poor and communication is interrupted, groupcast communication from UE-TX to UE-RX in the group can be performed using another relay UE. It is possible to improve the redundancy and reliability of groupcast communication in SL. In addition, by using groupcast communication for communication between relay UE and UE-RX, data of a service using SL communication received from UE-TX can be transmitted by groupcast communication to a group including many UE-RX.

[0463] The methods disclosed in the third embodiment to the second modification of the third embodiment may be combined. For example, UE-TX performs groupcast communication with UE-RX via one or more relay UEs by the method disclosed in the third embodiment, and further performs groupcast communication with UE-RX via another one or more relay UEs by the method disclosed in the first modification of the third embodiment. In this way, for example, in a case where the communication method of the relay UE is limited for each relay UE, the relay UE can be effectively utilized by setting a relay suitable for each communication method.

[0464] UE-TX may perform groupcast communication with UE-RX through direct UE-to-UE communication, and may perform groupcast communication with other UE-RX through indirect UE-to-UE communication via a relay UE. As a method for performing groupcast communication through indirect UE-to-UE communication via a relay UE, the methods disclosed in the third embodiment to the second modification of the third embodiment may be applied as appropriate. For example, when groupcast communication is required for UE-RX other than UE-RX capable of direct UE-to-UE communication, a method for performing groupcast communication through indirect UE-to-UE communication via a relay UE may be applied. In this way, groupcast communication can be performed for UE-RX that is farther away than the UE-RX.

[0465] In the method disclosed above, when group communication is performed from UE-TX to UE-RX via a relay UE, UE-RX may receive the same data from UE-TX in duplicate. This ensures redundancy in indirect communication between UEs between UE-TX and UE-RX via a relay UE, improving reliability.

[0466] However, in such a case, for example, the UE-RX will forward the duplicated data to the application layer of the V2X service. In that case, the application layer cannot determine whether the data is duplicated or not, and receives the same data multiple times. As a result, malfunction may occur.

[0467] For this reason, the application layer may discard the duplicated data. However, if the application layer cannot determine whether the data is duplicated or not, a problem remains. To solve such a problem, the UE-RX may keep one piece of data and discard the other pieces of data. As a method for this, the data discarding method disclosed in the second modification of the third embodiment when the UE-RX receives the same data from a plurality of relay UEs may be appropriately applied. Similar effects can be obtained. In addition, it is not necessary to perform processing in the application layer, and the occurrence of malfunctions can be reduced.

[0468] Embodiment 4 No disclosure has been made regarding a method for setting up a radio bearer when indirect communication is performed in SL via a relay UE. Unlike the conventional communication between a UE and a base station using a Uu interface and the direct communication between UEs in SL using a PC5 interface, a method for setting up a radio bearer when a relay UE is used in SL is required. A method for setting up a radio bearer between a source UE and a relay UE and between a relay UE and a destination UE of SL communication is required. In this fourth embodiment, a method for setting up a radio bearer when indirect communication between UEs is performed in SL via a relay UE is disclosed.

[0469] Disclosed is a protocol configuration of each node when indirect communication between UEs is performed via a relay UE in SL. FIG. 36 is a diagram showing an example of a protocol configuration of each node when indirect communication between UEs is performed via a relay UE in SL. A transmitting side UE-TX performing SL communication transmits data to a relay UE1 (UE-to-UE relay1), and the relay UE1 relays data received from the UE-TX to a receiving side UE-RX. Signaling transmitted from the UE-TX may be relayed to the UE-RX via the relay UE1. The relay UE1 relays between RLC and PDCP. In this way, the relay UE1 does not need to perform PDCP processing on the data to be relayed. This allows relaying to be performed early by the relay UE1. The indirect communication between UEs via a relay UE in SL can be performed with low delay.

[0470] A method for setting up a radio bearer in a relay UE is disclosed.

[0471] The relay UE sets up an RLC bearer between the relay UE and UE-RX. The relay UE may set up an LCID between the relay UE and UE-RX. The relay UE may set up from RLC to PHY between the relay UE and UE-RX. The UE-TX notifies the relay UE of the bearer setting between the UE-TX and the relay UE. For example, the relay UE may set up a bearer between the relay UE and UE-RX using the bearer setting between the UE-TX and the relay UE received from the UE-TX. The relay UE may notify the UE-RX of these settings. In this way, the relay UE can set up a bearer for SL communication between the relay UE and UE-RX. The relay UE can easily set up a bearer for SL communication between the relay UE and UE-RX using the load status of the relay UE itself and the radio wave propagation status between the relay UE and UE-RX.

[0472] The UE-TX may notify the relay UE of a part or all of the V2X policy / parameters of the V2X service implemented using the SL communication. For example, the relay UE may use the V2X policy / parameters to set up a bearer between the relay UE and the UE-RX. In this way, for example, even when the V2X service is implemented by indirect communication between UEs via the relay UE between UE-TX and UE-RX, it is possible to provide the V2X policy / parameters required for the V2X service.

[0473] As another method, the UE-TX may set the RLC bearer between the relay UE and UE-RX. The UE-TX may set the LCID between the relay UE and UE-RX. The UE-TX may set from the RLC to the PHY between the relay UE and UE-RX. The UE-TX may notify the UE-RX of these settings. The UE-TX may notify the UE-RX of these settings via the relay UE. The UE-TX notifies the relay UE of these settings, and the relay UE notifies the UE-RX of the settings. In this way, for example, the UE-TX can request the relay UE to set up a bearer between the relay UE and UE-RX. For example, the UE-TX can also set up a bearer between the relay UE and UE-RX according to the QoS required for the V2X service.

[0474] As the above-mentioned notification method, PC5 signaling may be used. For example, notification from UE-TX to relay UE may be performed in PC5 link establishment processing between UE-TX and relay UE. Notification from relay UE to UE-RX may be performed in PC5 link establishment processing between relay UE and UE-RX. As another notification method, RRC signaling of SL may be used. The above-mentioned setting may be notified as AS setting.

[0475] Information indicating whether the relay UE decodes the signaling or data that the UE-TX transmits to the UE-RX via the relay UE may be provided. For example, the UE-TX may notify the relay UE of the information by including it in an RLC PDU. In this way, the UE-TX can instruct the relay UE to decode the signaling or data.

[0476] When the UE-TX notifies the UE-RX of the bearer setup between the relay UE and the UE-RX via the relay UE, the relay UE may decode the setup. The UE-TX may set information indicating whether to decode to "decode" and notify the information. In this way, the relay UE can recognize the bearer setup between the relay UE and the UE-RX that is set by the UE-TX.

[0477] The configuration of the RLC bearer between the relay UE and UE-RX may not be the same as the configuration of the RLC bearer between the UE-TX and the relay UE. The configuration of the RLC bearer between the relay UE and UE-RX may be different from the configuration of the RLC bearer between the UE-TX and the relay UE. For example, only the configuration of the LCID between the relay UE and UE-RX may be different from the configuration of the LCID between the UE-TX and the relay UE.

[0478] In this way, the RLC bearer between the relay UE and UE-RX can be set regardless of the RLC bearer between the UE-TX and the relay UE. Also, the LCID between the relay UE and UE-RX can be set regardless of the LCID between the UE-TX and the relay UE. Depending on the load situation of the relay UE, the settings on the UE-TX side and the UE-RX side can be changed.

[0479] In addition, the settings from RLC to PHY between the relay UE and UE-RX may not be the same as the settings from RLC to PHY between the UE-TX and the relay UE. The settings from RLC to PHY between the relay UE and UE-RX may be different from the settings from RLC to PHY between the UE-TX and the relay UE. In this way, it becomes possible to change the settings on the UE-TX side and the UE-RX side, including the settings from MAC to PHY, depending on the load situation and the radio wave propagation environment of the relay UE.

[0480] The bearer setting between the relay UE and UE-RX may be set for each UE-TX. The identifier of the UE-TX and the bearer between the relay UE and UE-RX may be set in association with each other. The identifier of the UE-TX and the identifier of the RLC bearer may be set in association with each other. When the identifier of the RLC channel of the RLC bearer is assigned, the identifier of the UE-TX and the identifier of the RLC channel may be set in association with each other. The identifier of the UE-TX and the LCID may be set in association with each other. The relay UE may relay SL communications from multiple UE-TX. In this way, for example, even when the relay UE relays SL communications from multiple UE-TX, the UE-RX that has been notified of the bearer setting can recognize which UE-TX the bearer setting is for. Malfunctions in the UE-RX can be reduced.

[0481] Fig. 36 discloses an example in which the LCID setting between UE-TX and relay UE is different from the LCID setting between relay UE and UE-RX. The LCID between UE-TX and relay UE1 is set to 1, and the LCID between relay UE1 and UE-RX is set to 2. Mapping from LCID1 to LCID2 is performed in relay UE1. In SL communication, LCID1 is used for data transmitted from UE-TX to relay UE1, relay UE1 changes LCID1 to LCID2, and LCID2 is used for data transmitted from relay UE1 to UE-RX.

[0482] The UE-RX is notified in advance of the LCID setting used in relay transmission between the relay UE1 and the UE-RX, which enables the UE-RX to receive data of LCID2.

[0483] By following the example of Figure 36, a bearer for SL communication between the relay UE and UE-RX can be set up depending on the load condition in the relay UE and the radio wave propagation condition between the relay UE and UE-RX.

[0484] The identifier of the radio bearer between the UE-TX and the relay UE may be the same as the identifier of the radio bearer between the relay UE and the UE-RX. In the example of Fig. 36, the ID of the DRB for SL communication is set to 1. In this way, it is possible to change the LCID setting in the same DRB.

[0485] Another example of a method for establishing an RLC bearer is disclosed.

[0486] Fig. 37 is a diagram showing an example in which the LCID setting between UE-TX and relay UE is the same as the LCID setting between relay UE and UE-RX. The protocol configuration of each node is the same as that in Fig. 36, so a description is omitted. The LCID between UE-TX and relay UE1 is set to 1, and the LCID between relay UE1 and UE-RX is set to 1. In SL communication, LCID1 is used for data transmitted from UE-TX to relay UE1, and the same LCID1 is used for data transmitted from relay UE1 to UE-RX.

[0487] The UE-RX is notified in advance of the LCID setting used in relay transmission between the relay UE1 and the UE-RX, which enables the UE-RX to receive data of LCID1.

[0488] The UE-TX may request the relay UE to set the LCID between the UE-TX and the relay UE to the same as the LCID between the relay UE and the UE-RX. For example, information on whether the LCID between the UE-TX and the relay UE should be set to the same as the LCID between the relay UE and the UE-RX may be provided, and the UE-TX may notify the relay UE of the information. As another method, it may be statically determined in advance by a standard or the like that the LCID between the E-TX and the relay UE should be set to the same as the LCID between the relay UE and the UE-RX.

[0489] By following the example of Fig. 37, it is possible to facilitate the bearer setup process in the relay UE. Also, by making the LCID between the UE-TX and the relay UE the same as the LCID between the relay UE and UE-RX, it becomes possible for the UE-TX and UE-RX to use a common LCID for the same data communication.

[0490] When indirect communication between UEs is performed via a relay UE using SL communication, a status report function indicating the data reception status and a polling function for requesting a status report may be provided. These functions may be RLC functions. Examples of the data reception status include information indicating reception confirmed data and / or reception unsuccessful data, segment information in RLC, etc. These pieces of information may be associated with LCID information.

[0491] The relay UE may notify the UE-TX of a status report for the data received from the UE-TX. The UE-TX may notify the relay UE of polling. Also, the UE-RX may notify the relay UE of a status report for the data received from the relay UE. The relay UE may notify the UE-TX of polling.

[0492] The relay UE may notify the UE-TX of a status report of data received from the UE-RX. In this way, the UE-TX can receive a status report between the relay UE and the UE-RX. For example, the UE-TX can correct the bearer setting between the relay UE and the UE-RX by using the status report between the relay UE and the UE-RX so as to satisfy the QoS required for the V2X service using the SL communication via the relay UE. This is effective when applied to a case where the UE-TX sets up a bearer between the relay UE and the UE-RX.

[0493] When the LCID between the UE-TX and the relay UE is different from the LCID between the relay UE and UE-RX, a problem occurs in that the status reports are not associated with each other even though the data is the same before and after the relay. As a method for solving such a problem, the relay UE may notify the UE-TX of information associating the LCID between the UE-TX and the relay UE with the LCID between the relay UE and UE-RX. For example, the relay UE notifies the UE-TX of the LCID set for the communication to be relayed and the mapping information of the LCID. The relay UE notifies the UE-TX of the status report corresponding to those LCIDs. In this way, the UE-TX can receive the LCID and the status report corresponding to it. The UE-TX can recognize whether the notified status report is a status report between the UE-TX and the relay UE, or a status report between the relay UE and UE-RX.

[0494] Another method is disclosed. The status report between the UE-TX and the relay UE may include the status report between the relay UE and UE-RX. Alternatively, these status reports may be merged. A format of a data unit capable of including and transmitting status reports of a plurality of SL communications may be provided. The relay UE includes the status report between the relay UE and UE-RX in the status report between the UE-TX and the relay UE, and notifies the UE-TX. The status report may be a status report of data of the LCID set between the UE-TX and the relay UE. In this way, the UE-TX can receive each status report.

[0495] A polling for requesting a status report between the UE-TX and the relay UE may be provided, and the polling may be notified from the UE-TX to the relay UE. A polling for requesting a status report between the relay UE and the UE-RX may be provided, and the polling may be notified from the relay UE to the UE-RX. Alternatively, a polling for requesting a status report between the UE-TX and the relay UE and a status report between the relay UE and the UE-RX may be provided, and the polling may be notified from the UE-TX to the relay UE. In this way, it is possible to trigger various status reports.

[0496] The UE-RX may notify the UE-TX of a status report of the data received from the relay UE via the relay UE. As a notification method, the above-mentioned method in which the relay UE notifies the UE-TX of a status report of the data received from the UE-RX may be applied. The UE-TX may use the status report in the UE-RX to determine the total data communication status between the UE-TX and the relay UE and between the relay UE and the UE-RX.

[0497] In this way, for example, in the UE-TX or the relay UE, it becomes possible to set up a bearer according to the communication status between the UE-TX and the relay UE and the communication status between the relay UE and the UE-RX. Even in the case of indirect communication between UEs via the relay UE, it becomes possible to satisfy the QoS required for the V2X service using SL communication.

[0498] When indirect communication between UEs is performed using SL communication via a relay UE, information on the data transmission / reception status at the relay UE may be provided. A function for notifying the UE-TX of the information from the relay UE may be provided. The following (1) to (7) are disclosed as specific examples of the information on the data transmission / reception status at the relay UE.

[0499] (1) Information regarding PDCP that could not be received.

[0500] (2) Information about successfully transmitted PDCPs.

[0501] (3) Information about successful PDCP retransmissions.

[0502] (4) Information about buffer size.

[0503] (5) Information about data rates.

[0504] (6) Cause information.

[0505] (7) A combination of (1) to (6) above.

[0506] The information (1) may be, for example, a sequence number of a PDCP PDU that the relay UE was unable to receive from the UE-TX. The UE-TX becomes able to recognize the PDCP PDU that the relay UE was unable to receive. The information (1) may be, for example, sequence number information of a PDCP PDU that was unable to be received. Also, the information (1) may be, for example, the smallest sequence number information of the sequence numbers of the PDCP PDUs that were unable to be received. Also, for example, the information (1) may be information indicating whether or not a PDCP PDU was able to be received in a predetermined reception range (window). The information may be information indicated by a bitmap for each PDCP PDU.

[0507] The information in (2) may be, for example, the sequence number of the PDCP PDU successfully transmitted from the relay UE to the UE-RX. The UE-TX can recognize how many PDCP PDUs have been delivered from the relay UE to the UE-RX. The information in (2) may be, for example, the highest sequence number information of the successfully transmitted PDCP PDUs. The information in (2) may be, for example, the highest sequence number information of the successfully transmitted PDCP PDUs in sequence.

[0508] The information in (3) may be, for example, a sequence number of a PDCP PDU that has been successfully retransmitted from the relay UE to the UE-RX. The UE-TX can recognize how many PDCP PDUs have been delivered from the relay UE to the UE-RX. The information in (3) may be, for example, information on the highest sequence number of the PDCP PDUs that have been successfully retransmitted. The information in (3) may be, for example, a sequence number of a retransmitted PDCP PDU that has been transmitted to a layer lower than PDCP in the relay UE. The information in (3) may be, for example, the highest sequence number of a retransmitted PDCP PDU that has been transmitted to a layer lower than PDCP.

[0509] The information (4) may be, for example, the amount of data that can be buffered by the relay UE. The information (4) may be, for example, the amount of data that the UE-TX is requested to transmit. The UE-TX can recognize how much data to transmit to the relay UE.

[0510] The information (5) may be, for example, a transmission data rate requested to the UE-TX, so that the UE-TX can recognize the data rate at which to transmit data to the relay UE.

[0511] The information in (6) may be, for example, information about the state of the link between the relay UE and the UE-RX. The information in (6) may be, for example, information about the state of the PC5 link, information about the radio state, or information about the RRC state. These pieces of information may be detected by the relay UE or may be reported from the UE-RX. The UE-TX can recognize the state of the link between the relay UE and the UE-RX.

[0512] The relay UE notifies the UE-TX of information related to the data transmission / reception status at the relay UE. The relay UE may associate the information with LCID information. The UE-TX may also notify the relay UE of information indicating that the information is requested. The relay UE, having received the request information, notifies the UE-TX of information related to the data transmission status at the relay UE.

[0513] In this way, the UE-TX can recognize the data transmission / reception status at the relay UE, including the data transmission / reception status between the relay UE and the UE-RX. For example, the UE-TX can correct the bearer setting between the relay UE and the UE-RX by using the status report between the relay UE and the UE-RX so as to satisfy the QoS required for the V2X service using the SL communication via the relay UE. This is effective when applied to a case where the UE-TX sets up a bearer between the relay UE and the UE-RX.

[0514] If the LCID between the UE-TX and the relay UE is different from the LCID between the relay UE and UE-RX, a problem occurs in that it is unclear which RLC bearer the information on the data transmission / reception status at the relay UE is. As a method for solving such a problem, the relay UE may notify the UE-TX of information associating the LCID between the UE-TX and the relay UE with the LCID between the relay UE and UE-RX. For example, the relay UE notifies the UE-TX of the LCID set for the communication to be relayed and the mapping information of the LCID. The relay UE notifies the UE-TX of the information on the data transmission / reception status at the relay UE using the LCID set between the UE-TX and the relay UE and the LCID set between the relay UE and UE-RX.

[0515] In this way, the UE-TX can recognize whether the information regarding the data transmission / reception status received from the relay UE is information between the UE-TX and the relay UE, or information between the relay UE and UE-RX.

[0516] Another method is disclosed. The relay UE notifies the UE-TX of information on the data transmission and reception status at the relay UE, including the data transmission and reception status between the relay UE and UE-RX, as information on the data transmission and reception status at the relay UE corresponding to the LCID set between the UE-TX and the relay UE. The relay UE may include the data transmission and reception status between the relay UE and UE-RX in the information on the data transmission and reception status at the relay UE corresponding to the LCID set between the UE-TX and the relay UE, based on the mapping between the LCID between the UE-TX and the relay UE and the LCID between the relay UE and UE-RX performed by the relay UE itself. In this way, the UE-TX can receive information on the data transmission and reception status at the relay UE, including the data transmission and reception status between the relay UE and UE-RX.

[0517] In SL communication, in order to transmit a status report indicating a data reception status or information regarding a data transmission / reception status from the UE-RX to the relay UE or from the relay UE to the UE-TX, a PC5 link may be established from the UE-RX to the relay UE or from the relay UE to the UE-TX. The establishment of the PC5 link may be performed when the PC5 link is established from the UE-TX to the relay UE or when the PC5 link is established from the relay UE to the UE-RX.

[0518] A status report indicating the data reception status or a data transmission / reception status may be notified from the UE-RX to the relay UE or from the relay UE to the UE-TX by PC5 signaling in the PC5 link. Alternatively, RRC signaling or MAC signaling may be used. In this way, it becomes possible to transmit a status report indicating the data reception status or information regarding the data transmission / reception status from the UE-RX to the relay UE or from the relay UE to the UE-TX in the SL communication.

[0519] In this way, for example, in the UE-TX or the relay UE, it becomes possible to set up a bearer according to the communication status between the UE-TX and the relay UE and the communication status between the relay UE and the UE-RX. Even in the case of indirect communication between UEs via the relay UE, it becomes possible to satisfy the QoS required for the V2X service using SL communication.

[0520] An example of a method for establishing a radio bearer is disclosed.

[0521] Fig. 38 is a diagram showing another example of the protocol configuration of each node when performing indirect communication between UEs via a relay UE in SL. Relay UE1 (UE-to-UE relay1) relays between SDAP and PDCP. In this way, relay UE1 can relay data before processing by PDCP. This allows relay UE1 to set up a radio bearer between relay UE1 and UE-RX. The radio bearer can be set up depending on the load situation of relay UE1.

[0522] A method for setting up a radio bearer in a relay UE is disclosed.

[0523] The relay UE sets up a radio bearer between the relay UE and UE-RX. The radio bearer may be an SRB or a DRB. The relay UE may notify the UE-RX of the radio bearer setting. In this manner, the relay UE can set up a bearer for SL communication between the relay UE and UE-RX. The relay UE can easily set up a bearer for SL communication between the relay UE and UE-RX by using the load situation in the relay UE itself and the radio wave propagation situation between the relay UE and UE-RX.

[0524] As another method, the UE-TX may set up a radio bearer between the relay UE and UE-RX. The UE-TX notifies the UE-RX of the radio bearer setting. The UE-TX may notify the UE-RX of the setting via the relay UE. The UE-TX notifies the relay UE of the radio bearer setting, and the relay UE notifies the UE-RX of the radio bearer setting. In this way, the UE-TX can request the relay UE to set up a bearer between the relay UE and UE-RX. For example, the UE-TX can set up a bearer between the relay UE and UE-RX according to the QoS required for the V2X service.

[0525] As a method for notifying the above-mentioned settings, the notification method disclosed in the above-mentioned RLC bearer setting method may be applied as appropriate.

[0526] The configuration of the radio bearer between the relay UE and UE-RX may not be the same as the configuration of the radio bearer between the UE-TX and the relay UE. The configuration of the radio bearer between the relay UE and UE-RX may be different from the configuration of the radio bearer between the UE-TX and the relay UE. For example, only the configuration of the radio bearer identifier between the relay UE and UE-RX and the LCID used in the RLC bearer may be different from the configuration of the radio bearer identifier between the UE-TX and the relay UE and the LCID used in the RLC bearer.

[0527] In this way, the radio bearer between the relay UE and UE-RX can be set regardless of the radio bearer between the UE-TX and the relay UE. Also, the radio bearer identifier and LCID between the relay UE and UE-RX can be set regardless of the radio bearer identifier and LCID between the UE-TX and the relay UE. Depending on the load situation of the relay UE, the settings on the UE-TX side and the UE-RX side can be changed.

[0528] In addition, the settings from RLC to PHY between the relay UE and UE-RX may not be the same as the settings from RLC to PHY between the UE-TX and the relay UE. The settings from RLC to PHY between the relay UE and UE-RX may be different from the settings from RLC to PHY between the UE-TX and the relay UE. In this way, it becomes possible to change the settings on the UE-TX side and the UE-RX side, including the settings from MAC to PHY, depending on the load situation and the radio wave propagation environment of the relay UE.

[0529] FIG. 38 discloses an example in which the setting of the DRB between the UE-TX and the relay UE is different from the setting of the DRB between the relay UE and UE-RX. A DRB1 is set between the UE-TX and the relay UE1, and a DRB2 is set between the relay UE1 and UE-RX. In the relay UE1, mapping from the DRB1 to the DRB2 is performed. In addition, an LCID1 is set in the DRB1 between the UE-TX and the relay UE1, and an LCID2 is set in the DRB2 between the relay UE1 and UE-RX. In the SL communication, the LCID1 of the DRB1 is used for data transmitted from the UE-TX to the relay UE1, the relay UE1 changes the LCID1 of the DRB1 to the LCID2 of the DRB2, and the LCID2 of the DRB2 is used for data transmitted from the relay UE1 to the UE-RX.

[0530] The UE-RX is notified in advance of the DRB identifier and LCID setting used in relay transmission between the relay UE1 and the UE-RX. This enables the UE-RX to receive data of LCID2 of the DRB2.

[0531] By following the example of Figure 38, a bearer for SL communication between the relay UE and UE-RX can be set up depending on the load condition in the relay UE and the radio wave propagation condition between the relay UE and UE-RX.

[0532] In the relay UE, multiple radio bearers may be mapped to one RLC bearer. The bearer configuration between the relay UE and UE-RX may include the identifier of the corresponding radio bearer. In this way, the number of RLC bearers configured in the relay UE can be reduced, and the configuration can be simplified.

[0533] As a protocol configuration of each node when indirect communication between UEs is performed via a relay UE in SL, relaying between SDAP and PDCP has been disclosed. As another configuration, relaying may be performed between SDAP and V2X layer. It becomes possible to relay PC5 QoS flow-based data.

[0534] In the SDAP, mapping from the PC5 QoS flow to the radio bearer is performed. Regarding the mapping from the PC5 QoS flow to the bearer, the mapping between the UE-TX and the relay UE may be different from the mapping between the relay UE and the UE-RX. In the relay UE, mapping from the QoS flow to the radio bearer is performed according to the mapping method set between the relay UE and the UE-RX. The mapping from the QoS flow to the bearer between the relay UE and the UE-RX may be set by the relay UE or may be set by the UE-TX. As for the setting method, the setting method of the DRB described above may be applied as appropriate.

[0535] In this way, the relay UE or UE-TX can set mapping from a QoS flow for SL communication between the relay UE and UE-RX to a radio bearer using the load condition at the relay UE and the radio propagation condition between the relay UE and UE-RX, etc.

[0536] In addition, the above-mentioned DRB setting methods may be combined. For example, the setting of the DRB and the mapping setting from the QoS flow to the DRB between the UE-TX and the relay UE may be different from the setting between the relay UE and the UE-RX. In this way, more flexible setting is possible.

[0537] By using the method disclosed in the fourth embodiment, it becomes possible to implement SL communication according to the QoS required for the V2X service even in indirect communication between UEs via a relay UE.

[0538] When indirect communication is performed via a relay UE in SL, the relay UE may hold data for a predetermined period. A timer may be set as the predetermined period. The relay UE holds the data to be relayed until the timer expires. The relay UE may also perform retransmission processing of the data to be relayed until the timer expires. When the timer expires, the relay UE discards the data. The relay UE may notify the UE-TX that the data has been discarded. The relay UE may notify which data has been discarded. Information on the discarded data may be added to the data transmission / reception status at the relay UE described above. The discarded data may be indicated, for example, by a PDCP sequence number.

[0539] The timer may be set by the UE-TX and notified to the relay UE. Alternatively, the relay UE may set the timer. When the relay UE sets the timer, the UE-TX or UE-RX may be notified of the timer setting. Alternatively, the timer setting may be statically determined by a standard or the like. In this way, the relay UE can recognize the timer setting.

[0540] In this way, even if the timing of data reception from UE-TX in the relay UE does not match the timing of data transmission / reception to UE-RX in the relay UE, it is possible to reduce malfunctions in the data transmission / reception processing in the relay UE.

[0541] Variation 1 of embodiment 4 In order to improve the reliability of communication between a base station and a terminal, there is a packet duplication technology that duplicates one piece of data and transmits and receives it through different routes (Non-Patent Document 16). In packet duplication, a route or a protocol used in each route may be called a leg. In SL communication as well, there is a demand for improving the reliability of SL communication for various services. However, there is no disclosure of a method of packet duplication in SL communication, particularly a method of packet duplication when indirect communication is performed in SL communication via a relay UE.

[0542] In a first modification of the fourth embodiment, a method of packet duplication in the case where indirect communication between UEs is performed via a relay UE in SL will be disclosed.

[0543] Fig. 39 is a conceptual diagram showing packet duplication in the case of indirect communication via a relay UE in SL communication, in accordance with the first modification of the fourth embodiment. The UE-TX performs packet duplication, and transmits each piece of duplicated data to the UE-RX via different relay UEs (relay UE1 and relay UE2). The UE-RX receives the duplicated data from the relay UE1 and relay UE2. If the data received from the relay UE has already been received from another relay UE, the UE-RX may discard the data received later.

[0544] In SL communication using multiple carriers (carrier frequencies), a relay is set for each carrier. UE-TX and UE-RX may perform SL communication using CA (Carrier Aggregation). A relay may be set for each CA carrier. The same relay UE may be used for one or more carriers. Also, a relay may not be set for one or more carriers. In SL communication using multiple carriers, direct communication between UEs or indirect communication between UEs via a relay UE may be set for each carrier. The method of setting a relay on each carrier may be, for example, the method disclosed in Non-Patent Document 24 or the method disclosed in the fourth embodiment.

[0545] The carrier between the relay UE and UE-RX may be set to the same as the carrier between the UE-TX and the relay UE. The same should be done when setting the relay for each CA carrier. These settings may be performed by the UE-TX or the relay UE. Alternatively, the gNB may perform these settings. Alternatively, the S-UE may perform these settings. For example, if the node that performs scheduling performs the carrier settings, the process for performing the relay can be simplified.

[0546] As another method, the carrier between the relay UE and UE-RX may be statically determined to be the same as the carrier between the UE-TX and the relay UE, etc. This makes it possible to further facilitate the process of implementing relaying, since information notification or signaling for setting is not required.

[0547] The carrier between the relay UE and UE-RX may be different from the carrier between the UE-TX and the relay UE. In this case, however, it is preferable to make the carrier between each relay UE and UE-RX different. The same should be done when setting a relay for each CA carrier. These settings may be performed by the UE-TX, the gNB, or the S-UE. It is possible to make the carrier between each relay UE and UE-RX different.

[0548] In this way, UE-TX can perform indirect communication between UEs via relay UEs on different carriers with UE-RX. By using different carriers between UE-TX and each relay UE, and also between each relay UE and UE-RX, it is possible to avoid interference between resources used for SL communication. Therefore, SL communication using multiple carriers (carrier frequencies) can be performed with high communication quality and low latency.

[0549] In packet duplication in SL communication, a relay may be set for each route. The same relay UE may be used for one or more routes. Also, a relay may not be set for one or more routes. In SL communication using multiple routes, direct communication between UEs or indirect communication between UEs via a relay UE may be set for each route. The method of setting a relay on each route may be, for example, the method disclosed in Non-Patent Document 24 or the method disclosed in the fourth embodiment.

[0550] Packet duplication may be performed using CA in SL communication. In packet duplication using CA, a relay may be set for each CA carrier. As a method for setting a relay for each CA carrier, the above-mentioned method for setting a relay for each CA carrier and the method for setting a relay for each route may be combined and applied as appropriate.

[0551] For example, in packet duplication using CA, the carrier between the relay UE and UE-RX may be set to the same as the carrier between the UE-TX and the relay UE for each path. These settings may be performed by the UE-TX or the relay UE. Alternatively, the gNB may perform these settings. Alternatively, the S-UE may perform these settings. For example, if a node that performs scheduling performs carrier settings, the process for performing relaying can be simplified.

[0552] For packet duplication in SL, UE-TX and UE-RX set up an RLC bearer for each radio bearer, the number of which is equal to the number of duplications. The duplicated data is transmitted and received using each RLC bearer. For example, if the number of packet duplications is 2, one DRB is set up for data communication that performs packet duplication, and two RLC bearers are set up in the DRB. A different LCID is assigned to each RLC bearer.

[0553] In the case of SL communication, when a relay is set for each path and packet duplication is performed, the path becomes an indirect communication between UEs via a relay UE. Therefore, it is preferable to set an RLC bearer between the relay UE-TX and the relay UE, and to set an RLC bearer between the relay UE and the UE-RX.

[0554] In SL communication, when a relay is set for each route to perform packet duplication, for example, if the LCID between relay UE-TX and relay UE is different from the LCID between relay UE and UE-RX, and the LCID between relay UE1 and UE-RX is the same as the LCID between relay UE2 and UE-RX, UE-RX will receive data of the same LCID. In that case, UE-RX cannot determine whether the received data is a packet duplication or not. In other words, packet duplication cannot be performed normally.

[0555] To solve this problem, it is advisable to set the same LCID to the RLC bearer between the relay UE-TX and the relay UE, and to the RLC bearer between the relay UE and the UE-RX. By setting the same LCID, the UE-RX can recognize which received data is a packet duplication. In addition, since the LCID set on the UE-TX side is used, the UE-RX can recognize which received data is a packet duplication even in the case of packet duplication using a route with a relay and a route without a relay.

[0556] These settings may be performed by the UE-TX or the relay UE. Alternatively, the gNB may perform these settings. Alternatively, the S-UE may perform these settings. For example, a node that performs RLC bearer settings for packet duplication may perform these settings. The settings can be facilitated. For example, the relay UE may perform these settings. The relay UE may set the LCID of the RLC bearer between the UE-TX and the relay UE itself to the LCID of the RLC bearer between the relay UE and the UE-TX.

[0557] The method of setting a bearer in indirect communication between UEs via a relay UE disclosed in the fourth embodiment may be applied as appropriate to the setting of an RLC bearer and an LCID in a path where a relay is set. For example, the method disclosed in FIG. 37 may be applied as appropriate.

[0558] Fig. 40 is a diagram showing an example of a protocol configuration for packet duplication when indirect communication is performed via a relay UE in SL communication. Fig. 40 shows packet duplication when a relay is set on a route for each carrier of CA. Fig. 40 shows a case where the number of packet duplications is set to 2. Relay UE1 is set on the route of carrier CC1, and relay UE2 is set on the route of carrier CC2.

[0559] PDCP of UE-TX performs packet duplication. For packet duplication, two RLC bearers are set in the radio bearer. LCID1 and LCID2 are set for the two RLC bearers, respectively. Data duplicated by PDCP is sent to the RLC channel of each RLC bearer and input to RLC. The duplicated data processed by RLC is assigned LCID1 and processed by MAC. In MAC, the duplicated data is mapped to different carriers. The correspondence of the mapping is predetermined and controlled by MAC. Here, the data mapped to different carriers (carrier CC1 and carrier CC2 are used) is processed by PHY and transmitted on each carrier. The duplicated data processed by RLC is assigned LCID1 and processed by MAC. In MAC, the duplicated data is mapped to different carriers. The correspondence of the mapping is predetermined and controlled by MAC. Here, the data mapped to different carriers (carrier CC1 and carrier CC2 are used) is processed by PHY and transmitted on each carrier. The duplicated data processed by RLC is assigned LCID1 and processed by MAC. In MAC, the duplicated data is mapped to different carriers. The correspondence of the mapping is predetermined and controlled by MAC. Here, the data mapped to different carriers (carrier CC1 and carrier CC2 are used) is processed by PHY and transmitted on each carrier.

[0560] Using carrier CC1, SL communication is performed between UE-TX and relay UE1 and between relay UE1 and UE-RX via relay UE1. Relay UE1 receives duplicated data from UE-TX and performs processing up to RLC. An RLC bearer is set up between relay UE1 and UE-RX. The LCID of this RLC bearer is set up to be the same as the LCID of the RLC bearer between UE-TX and relay UE1. This allows relay UE1 to send duplicated data output from the RLC channel with LCID1 set up on the receiving side to the RLC channel with LCID1 set up on the transmitting side.

[0561] Relay UE1 inputs the duplicated data to the RLC channel on the transmitting side and processes it with RLC. The duplicated data processed by RLC is assigned LCID1 and processed by MAC. The duplicated data processed by MAC is processed by PHY and transmitted on carrier CC1. UE-RX receives the duplicated data from relay UE and performs processing up to RLC. UE-RX processes the duplicated data with RLC set with LCID1, outputs it to the RLC channel, and inputs it to PDCP. PDCP in UE-RX can recognize that it is duplicated data by receiving data from the RLC channel set by packet duplication.

[0562] Using the carrier CC2, SL communication is performed between the UE-TX and the relay UE2 and between the relay UE2 and the UE-RX via the relay UE1. This is performed in the same manner as the above-mentioned method of performing SL communication via the relay UE1 using the carrier CC1.

[0563] The UE-RX processes the duplicated data output from the RLC channel of the RLC bearer set by packet duplication using PDCP, and inputs the duplicated data from PDCP to SDAP. The UE-RX PDCP determines whether the duplicated data input from RLC has already been received. If the UE-RX PDCP determines that the duplicated data input from RLC has already been received, it may discard the duplicated data received later.

[0564] By setting the LCID between UE-TX and relay UE1 to be the same as the LCID between relay UE1 and UE-RX, UE-RX can perform packet duplication normally. In this way, packet duplication can be performed when indirect communication is performed via relay UE in SL communication. This makes it possible to improve the reliability of SL communication.

[0565] In the above example, it is disclosed that the LCID between the UE-TX and the relay UE1 is set to be the same as the LCID between the relay UE1 and the UE-RX. Another example is disclosed. The LCID between the UE-TX and the relay UE may be made different from the LCID between the relay UE and the UE-RX. However, the LCID corresponding to the RLC bearer set on the path between each relay UE and the UE-RX is made different. These settings may be made by the UE-TX, the gNB, or the S-UE. It is possible to make the LCID of the RLC bearer between the relay UE and the UE-RX different on each path of packet duplication.

[0566] The node that has performed these settings notifies the UE-RX of these settings. The node may notify the UE-RX of these settings via a relay UE. In this way, the UE-RX can set the RLC bearer and LCID used in packet duplication. The UE-RX can then perform packet duplication normally.

[0567] As described above, in packet duplication, the LCID corresponding to the RLC bearer set on the path between each relay UE and UE-RX is made different, and these settings are notified to the UE-RX, so that the UE-RX can normally perform packet duplication. It is possible to perform packet duplication when indirect communication is performed via a relay UE in SL communication. This makes it possible to improve the reliability of SL communication.

[0568] The UE-TX may notify the relay UE of the release of the packet duplication setting. Alternatively, the UE-TX may notify the relay UE, and the relay UE may notify the UE-RX of the release of the packet duplication setting. This makes it possible to release the setting for packet duplication in the UE-TX. Since the bearer setting for packet duplication in the transmission process in the UE-TX, and in the relay UE and UE-RX can be released, it is possible to simplify the transmission and reception process in the relay UE and the reception process in the UE-RX.

[0569] The UE-TX may notify the UE-RX of information indicating whether to start or stop packet duplication. The UE-TX may notify the relay UE of information indicating whether to start or stop packet duplication. For example, the information may be information indicating activation or deactivation. The information may be notified together with the bearer setting for packet duplication or separately. For example, if the information indicates that packet duplication is to be started, the relay UE or UE-RX starts the packet duplication process. If the information indicates that packet duplication is to be stopped, the relay UE or UE-RX stops the packet duplication process.

[0570] In this way, the UE-RX or relay UE can recognize whether the packet duplication process has been started or stopped. It is possible to stop packet duplication while maintaining the packet duplication setting. Since there is no need to perform packet duplication process while packet duplication is stopped, it is possible to simplify the transmission process in the UE-TX, the transmission / reception process in the relay UE, and the reception process in the UE-RX. In addition, since there is no need to set packet duplication when switching from stopped to started, packet duplication can be started early. SL communication using packet duplication can be started with low delay.

[0571] In the example of Fig. 40, packet duplication when a relay is set on a route for each carrier of CA is disclosed. Another example of packet duplication when indirect communication is performed via a relay UE in SL communication is disclosed. The same carrier is used for multiple routes of packet duplication. A relay UE is set for each route of packet duplication using the same carrier.

[0572] Fig. 41 is a diagram showing another example of a protocol configuration for packet duplication in the case of indirect communication via a relay UE in SL communication. Fig. 41 discloses packet duplication when the same carrier is used for the packet duplication path. Fig. 41 discloses the case where the number of packet duplications is set to 2. Both of the two paths for packet duplication use carrier CC1, relay UE1 is set for one path, and relay UE2 is set for the other path.

[0573] The setting of the RLC bearer and LCID at each node in packet duplication and the packet duplication process are the same as those in FIG. 40, and therefore description thereof will be omitted.

[0574] When the same carrier is used for each path, interference occurs between the resources used for SL communication between UE-TX and each relay UE, and between each relay UE and UE-RX. This may result in an increase in the delay time of SL communication or communication interruption due to resource collision. A method for solving such problems is disclosed.

[0575] A different resource is set for each path of packet duplication. The resource may be an RP. Alternatively, the resource may be a resource reserved or selected for SL communication. In this way, interference between resources used for SL communication can be avoided. The RLC channel or LCID of the RLC bearer set for each path of packet duplication may be set in association with the resource.

[0576] An identifier may be provided for each path of packet duplication. The identifier of each path may be associated with a resource and configured. These configurations may be performed by the UE-TX, the gNB, or the S-UE. It is possible to make the LCID of the RLC bearer between the relay UE and the UE-RX different for each path of packet duplication.

[0577] These settings may be performed by the UE-TX or the relay UE. Alternatively, the gNB may perform these settings. Alternatively, the S-UE may perform these settings. For example, a node that performs RLC bearer settings for packet duplication may perform these settings. The node that performed the settings notifies the relay UE and / or UE-RX of the settings. When notifying the UE-RX, the node may notify the settings via the relay UE. The node that received the settings implements the settings for the RLC bearer of the node itself.

[0578] In this way, even if the same carrier is used on the packet duplication route, it is possible to avoid resource interference. As a result, the UE-RX can receive packet-duplicated data with a low error rate. This makes it possible to suppress an increase in the delay time of SL communication and reduce communication interruptions. When indirect communication is performed via a relay UE in SL communication, packet duplication makes it possible to improve the reliability of SL communication.

[0579] The UE-RX may notify the UE-TX of a packet duplication request. The UE-RX may notify the UE-TX of a packet duplication request via the relay UE. The UE-RX may notify information on the SL communication status between the relay UE and the UE-RX together with the packet duplication request. For example, the UE-RX may notify communication quality information between the relay UE and the UE-RX and information on the data reception status in the UE-RX. For example, when the number of successful data receptions via the relay UE falls below a predetermined value, the UE-RX notifies the UE-TX of a packet duplication request. The UE-TX that has received the packet duplication request from the UE-RX may use the request to determine whether or not to perform packet duplication for the UE-RX. In this way, packet duplication taking into account the data reception status in the UE-RX can be performed.

[0580] The relay UE may notify the UE-TX of a packet duplication request. The relay UE may notify information on the SL communication status between the relay UE and the UE-RX together with the packet duplication request. For example, the relay UE may notify information on the communication quality between the relay UE and the UE-RX and information on the data transmission status to the UE-RX at the relay UE. Also, for example, the relay UE may notify information on the communication quality between the relay UE and the UE-TX and information on the data reception status from the UE-TX at the relay UE.

[0581] For example, when the number of successful data transmissions to the UE-RX falls below a predetermined value, the relay UE notifies the UE-TX of a packet duplication request. Also, when the number of successful data receptions from the UE-TX falls below a predetermined value, the relay UE notifies the UE-TX of a packet duplication request. The UE-TX that receives the packet duplication request from the relay UE may use the request to determine whether or not to perform packet duplication for the UE-RX. In this way, packet duplication can be performed taking into account the data transmission / reception status at the relay UE.

[0582] The method disclosed in the first modification of the fourth embodiment makes it possible to perform packet duplication both in SL communication and in indirect communication between UEs via a relay. Therefore, redundancy can be obtained in indirect communication between UEs via a relay, and it becomes possible to improve the reliability of various services using SL communication.

[0583] The UE-TX may notify the relay UE of a request for packet duplication between the relay UE and UE-RX. The UE-TX notifies the relay UE of a request for packet duplication between the relay UE and UE-RX in SL communication with the UE-RX via the relay UE. The relay UE that receives the request sets up packet duplication between the relay UE and UE-RX and performs packet duplication. The relay UE may notify the UE-TX of the performance of packet duplication between the relay UE and UE-RX. The notification may be performed as a positive response to the request for packet duplication. In this way, even when the communication quality between the relay UE and UE-RX is poor, it is possible to obtain redundancy in the communication between the relay UE and UE-RX. This makes it possible to improve the reliability of the communication.

[0584] In the above description, the UE-TX requests the relay UE to perform packet duplication between the relay UE and the UE-RX, but as another method, the relay UE may determine whether to perform packet duplication between the relay UE and the UE-RX. The relay UE sets packet duplication with the UE-RX and performs packet duplication. In this way, packet duplication can be performed without waiting for a request from the UE-TX. It is possible to obtain redundancy in the communication between the relay UE and the UE-RX at an early stage, and it is possible to improve the reliability of the communication.

[0585] Variation 2 of embodiment 4 When indirect communication between UEs is performed via a relay in SL, there may be cases where multiple UE-TXs transmit data to one UE-RX via one relay. In such cases, if the relay UE relays the transmission data from each UE-TX to the UE-RX individually, the processing at the relay UE and the processing at the UE-RX become complicated.

[0586] In the second modification of the fourth embodiment, a method for solving such a problem will be disclosed.

[0587] The data transmitted from multiple UE-TXs is concatenated in the relay UE and transmitted to one UE-RX.

[0588] 42 is a conceptual diagram of an example in which a relay UE connects and relays data in SL communication in accordance with the second modification of the fourth embodiment. In SL, indirect communication between UE-TX1 and UE-RX and indirect communication between UE-TX2 and UE-RX are performed via relay UE1. Relay UE1 connects and relays data transmitted from UE-TX1 and UE-TX2 to the same UE-RX.

[0589] However, each of the multiple UE-TXs sets an RLC bearer and an LCID independently. This causes the LCID of the RLC bearer between the UE-TX and the relay UE to overlap. In this case, the same LCID is set for the data transmitted from the multiple UE-TXs in the transmission from the relay UE to the UE-RX, so the MAC of the relay UE transmits the data without distinguishing them. In addition, the MAC of the UE-RX cannot distinguish which UE-TX the data came from because the same LCID is set for the received data. This causes a problem that the UE-RX cannot distinguish the data for each UE-TX and cannot receive the data normally.

[0590] A method for solving such a problem is disclosed. In setting up an RLC bearer between a relay UE and a UE-RX, a different LCID is set for each UE-TX.

[0591] Fig. 43 is a diagram showing a first example of a protocol configuration for a relay UE to concatenate and relay data in SL communication. In SL, indirect communication between UE-TX1 and UE-RX and indirect communication between UE-TX2 and UE-RX are performed via relay UE1. Fig. 43 discloses an example in which relay UE1 concatenates and relays data transmitted from UE-TX1 and UE-TX2 to the same UE-RX.

[0592] Data generated by UE-TX1 is processed by PHY from PDCP set in radio bearer DRB1, and transmitted by carrier CC1. Relay UE1 receives the data transmitted from UE-TX1, and processes RLC from PHY. LCID1 is set as the LCID corresponding to the RLC bearer between UE-TX1 and relay UE1. Data generated by UE-TX2 is also received by relay UE1 in the same manner. Disclosed is a case where the same LCID1 is set as the LCID corresponding to the RLC bearer between UE-TX2 and relay UE1.

[0593] In the relay UE, a MAC may be set for each UE-TX. A different RLC bearer may be set for each UE-TX. In this way, even if the same LCID is set for data transmitted from multiple UE-TXs, the relay UE can distinguish the data transmitted from multiple UE-TXs.

[0594] Identifier information of the UE-TX may be provided. Identifier information of the UE-TX may be included in the RLC bearer setting. The UE-TX includes its own UE-TX identifier information in the RLC bearer setting and notifies the relay UE. The relay UE can recognize which UE-TX the RLC bearer setting is.

[0595] The RLC bearer for each UE-TX may be set in association with the radio bearer for each UE-TX. The radio bearer setting between the relay UEs for each UE-TX may include the identifier information of the UE-TX. The UE-TX includes the identifier information of its own UE-TX in the radio bearer setting and notifies the relay UE. The relay UE can recognize which UE-TX's RLC bearer is set.

[0596] The identifier of the UE-TX may be the L2 layer ID of the source. When the UE-TX notifies the relay UE of the radio bearer setting or the RLC bearer setting, the UE-TX notifies the relay UE of the L2 layer ID of the source. The relay UE can identify the UE-TX from the L2 layer ID of the source that performed the setting.

[0597] Between relay UE1 and UE-RX, an RLC bearer is set for data transmission from UE-TX1 and for data transmission from UE-TX2. The setting is performed so that the LCID of the RLC bearer for data transmission from UE-TX1 is different from the LCID of the RLC bearer for data transmission from UE-TX2. It is preferable to set the LCID set later to be different from the LCID set earlier.

[0598] In the example of Fig. 43, LCID1 is set as the LCID of the RLC bearer between UE-TX1 and relay UE1, so LCID1 is set as the LCID of the RLC bearer between relay UE1 and UE-RX. Since the same LCID1 is set as the LCID corresponding to the RLC bearer between UE-TX2 and relay UE1, LCID2 is set as the LCID of the RLC bearer between relay UE1 and UE-RX to make the LCIDs different.

[0599] These settings may be performed by the relay UE1. Alternatively, when the gNB or S-UE performs scheduling for both UE-TX1 and UE-TX2, the gNB or S-UE may perform the settings. The node that performed the settings notifies the relay UE1 and / or UE-RX of the settings. When notifying UE-RX, the node may notify the settings via the relay UE1. In this manner, a bearer can be set up between the relay UE1 and UE-RX.

[0600] Relay UE1 inputs data received from UE-TX1 to the RLC channel of the RLC bearer set between relay UE1 and UE-RX for transmission data from UE-TX1. Here, LCID1 is set. Relay UE1 inputs data received from UE-TX2 to the RLC channel of the RLC bearer set between relay UE1 and UE-RX for transmission data from UE-TX2. Here, LCID2 different from LCID1 is set.

[0601] Data input to each RLC is processed by MAC. MAC concatenates data transmitted to the same UE-RX. For example, the relay UE may use the L2 layer ID of the destination to determine whether to concatenate data. For example, if the L2 layer IDs of the destinations are the same, MAC concatenates the data. If the L2 layer IDs of the destinations are different, MAC does not concatenate the data. Since different LCIDs are assigned to the transmitted data from each UE-TX, the destinations can be distinguished even if concatenated by MAC. The relay UE may have only one transmitting MAC. The number of transmitting MACs of the relay UE may be the same as the number of UE-RXs to which the relay UE transmits. Concatenation and transmission for each UE-RX can be facilitated.

[0602] The data concatenated by the transmitting MAC of relay UE1 is processed by PHY and transmitted. UE-RX processes the data received from the relay UE by PHY and MAC. UE-RX separates the concatenated data by MAC. UE-RX uses the LCID attached to the data to determine whether it is data of the RLC bearer set for the transmission data from UE-TX1 or data of the RLC bearer set for the transmission data from UE-TX2. In the case of LCID1, the received data is separated as data of the RLC bearer set for the transmission data from UE-TX1, input to the RLC of the RLC bearer for UE-TX1, processed by the RLC, input to PDCP, processed by PDCP, and output to SDAP. In the case of LCID2, the received data is separated as data of the RLC bearer set for the transmission data from UE-TX2, input to the RLC of the RLC bearer for UE-TX2, processed by the RLC, input to PDCP, processed by PDCP, and output to SDAP.

[0603] In this way, the UE-RX can distinguish the data for each UE-TX, and the UE-RX can normally receive data from each UE-TX connected by the relay UE.

[0604] FIG. 43 discloses a case in which the LCID of the RLC bearer between UE-TX1 and the relay UE, established in UE-TX1, is the same as the LCID of the RLC bearer between UE-TX2 and the relay UE, established in UE-TX2.

[0605] 44 is a diagram showing a second example of a protocol configuration for a relay UE to concatenate and relay data in SL communication, which discloses an example in which the LCID of the RLC bearer between the UE-TX1 and the relay UE, which is set in the UE-TX1, is different from the LCID of the RLC bearer between the UE-TX2 and the relay UE, which is set in the UE-TX2.

[0606] Between relay UE1 and UE-RX, an RLC bearer is set for data transmission from UE-TX1 and for data transmission from UE-TX2. The setting is performed so that the LCID of the RLC bearer for data transmission from UE-TX1 is different from the LCID of the RLC bearer for data transmission from UE-TX2. The LCID set later is set to be different from the LCID set earlier.

[0607] In the example of Fig. 44, LCID1 is set as the LCID of the RLC bearer between UE-TX1 and relay UE1, so LCID1 is set as the LCID of the RLC bearer between relay UE1 and UE-RX. Since the same LCID2 is set as the LCID corresponding to the RLC bearer between UE-TX2 and the relay UE, this LCID is different from the LCID of the RLC bearer between UE-TX1 and relay UE. Therefore, LCID2 is set as it is as the LCID of the RLC bearer between relay UE1 and UE-RX.

[0608] In this way, it becomes possible to set a different LCID for each UE-TX in setting up an RLC bearer between the relay UE and UE-RX. The process in each node for connecting data by the relay UE is the same as that in Fig. 43, so the description is omitted. In this way, the UE-RX can separate data for each UE-TX, and can normally receive data from each UE-TX connected by the relay UE.

[0609] Fig. 45 is a diagram showing a third example of a protocol configuration for relaying data concatenated by a relay UE in SL communication. A relay UE1 (UE-to-UE relay1) relays data between SDAP and PDCP. Fig. 45 shows an example in which the setting of a DRB between the UE-TX and the relay UE is different from the setting of a DRB between the relay UE and UE-RX.

[0610] The radio bearer between UE-TX1 and the relay UE is set to DRB1, and the LCID of the RLC bearer is set to LCID 1. The radio bearer between UE-TX2 and the relay UE is set to DRB1, and the LCID of the RLC bearer is set to LCID 1. The same radio bearer identifier and the same LCID of the RLC bearer are set between UE-TX1 and the relay UE and between UE-TX2 and the relay UE.

[0611] Between relay UE1 and UE-RX, a radio bearer is set for data transmission from UE-TX1 and for data transmission from UE-TX2. The setting is performed so that the identifier and LCID of the radio bearer for data transmission from UE-TX1 are different from the identifier and LCID of the radio bearer for data transmission from UE-TX2. It is preferable to set the identifier and LCID of the radio bearer set later to be different from the identifier and LCID of the radio bearer set earlier.

[0612] In the example of FIG. 45, DRB1 is set as the identifier of the radio bearer between UE-TX1 and relay UE, and LCID1 is set as the LCID of the RLC bearer. Therefore, DRB1 is set as the identifier of the radio bearer between relay UE1 and UE-RX, and LCID1 is set as the LCID of the RLC bearer. The same DRB1 is set as the identifier of the radio bearer between UE-TX2 and relay UE, and the same LCID1 is set as the LCID corresponding to the RLC bearer. Therefore, in order to make the identifier and LCID of the radio bearer different, the same DRB2 is set as the identifier of the radio bearer between relay UE1 and UE-RX, and LCID2 is set as the LCID of the RLC bearer.

[0613] In this way, it becomes possible to set a different radio bearer identifier and a different LCID for each UE-TX in the bearer setting between the relay UE and UE-RX. The process in each node for connecting data by the relay UE is the same as that in Fig. 43, so the description is omitted. In this way, the UE-RX can separate data for each UE-TX, and can normally receive data from each UE-TX connected by the relay UE.

[0614] Another method is disclosed for concatenating data transmitted from a plurality of UE-TXs in a relay UE and transmitting the data to one UE-RX. The relay UE may map a plurality of radio bearers to one radio bearer and relay the data. The relay UE may set identifiers of different radio bearers when mapping the data. The setting may be performed by the UE-TX or the relay UE. The setting may also be associated with the identifier of the UE-TX. In this way, even when relaying between SDAP and PDCP, for example, data transmitted from a plurality of UE-TXs can be concatenated in the relay UE and transmitted to one UE-RX.

[0615] Another method is disclosed in which data transmitted from a plurality of UE-TXs is concatenated in a relay UE and transmitted to one UE-RX. The relay UE may map a plurality of QoS flows to one QoS flow and relay the data. Alternatively, the relay UE may map a plurality of QoS flows to one radio bearer and relay the data. The relay UE may set identifiers of different QoS flows when mapping the data. The setting may be performed by the UE-TX or the relay UE. The setting may also be associated with the identifier of the UE-TX. In this way, for example, even in the case of relaying between the SDAP and the V2X layer, it is possible to concatenate data transmitted from a plurality of UE-TXs in the relay UE and transmit the data to one UE-RX.

[0616] By using the method disclosed in the second modification of the fourth embodiment, when indirect communication between UEs is performed via a relay in SL, it becomes possible to transmit data from multiple UE-TXs to one UE-RX via one relay. It is not necessary to establish multiple PC5 links or RRC connections between the relay UE and UE-RX. It is possible to simplify the processing of indirect communication between UEs from multiple UE-TXs to one UE-RX via a relay UE.

[0617] Embodiment 5. In SL communication, there is an exceptional resource pool (RP) as a resource pool used during HO (see Non-Patent Document 1). However, for example, when many UEs perform HO simultaneously, all of those UEs will perform SL communication using the exceptional RP. In this case, due to congestion in the exceptional RP, resources for SL communication cannot be reserved, causing delays in communication or communication interruptions. To solve this problem, the introduction of an effective area has been proposed (see Non-Patent Document 25).

[0618] An effective area is set as an area where the RP can be used. The effective area is set to a range larger than the coverage of one cell. The effective area is set using a system information area ID (systemInformationAreaID) broadcast from the cell as system information (see non-patent document 26). The system information area ID indicates which system information area the cell belongs to, and is set for each SIB. It is advisable to set the system information area ID by the SIB that sets the RP.

[0619] As described above, by using the system information area ID as the effective area, it is possible to use the RP in a larger range. Therefore, for example, when performing HO between cells with the same system information area ID set, it is not necessary to use the exceptional RP. Therefore, it is possible to reduce congestion of the exceptional RP.

[0620] However, even if a system information area ID is used, an exception RP must be used for HO between coverage areas. Therefore, as described above, when many UEs perform HO simultaneously, congestion at the exception RP can cause communication delays or interruptions.

[0621] In the fifth embodiment, a method for solving such a problem will be disclosed.

[0622] One or more system information area IDs are configured for one cell. The cell broadcasts system information for which one or more system information area IDs are configured. When system information area IDs are configured for multiple cells, the combinations of multiple cells for which each system information area ID is configured may be different. For example, it is preferable to configure system information area IDs so that all system information area IDs are not changed during inter-cell HO.

[0623] FIG. 46 is a diagram showing an example in which multiple system information area IDs are set for one cell in the fifth embodiment. 1 is set as the system information area ID of a predetermined SIB of gNB1 to gNB5. Also, 2 is set as the system information area ID of the predetermined SIB of gNB3 and gNB5 to gNB9. The above-mentioned predetermined SIB may be some or all of the SIBs broadcast from the cell.

[0624] In a predetermined SIB broadcast by gNB1, gNB2, and gNB4, the system information area ID is set to 1. In a predetermined SIB broadcast by gNB6, gNB7, gNB8, and gNB9, the system information ID is set to 2. In a predetermined SIB broadcast by gNB3 and gNB5, the system information IDs are set to 1 and 2. In this way, it becomes possible to set multiple system information area IDs for one cell, such as gNB3 and gNB5.

[0625] In the conventional method for setting SIB and system information area ID, the system information area ID is set to the SIB. Therefore, even if multiple system information area IDs are set to the SIB, multiple values ​​cannot be set to the SIB. This invention discloses a method for solving such a problem.

[0626] In one SIB containing the same type of information, multiple SIBs are provided in which one or more pieces of information in the SIB are different. For example, SIB18 is provided with SIB18-1 and SIB18-2, each of which has different information. A system information area ID may be set for such SIBs. A different system information area ID may be set for each SIB having different information. In this way, it is possible to set SIBs having different information for each system information area ID.

[0627] 47 is a diagram showing an example of providing a plurality of SIBs each including the same type of information, each having one or more pieces of information different from the others, according to the fifth embodiment. For SIB18 having a common TX pool (commonTXpool) used in SL as the same type of information, SIB18-1 and SIB18-2 having different information values ​​are provided. In SIB18-1, common TX pool 1 (commonTXpool1) is set, and in SIB18-2, common TX pool 2 (commonTXpool2) is set.

[0628] A system information area ID is set in each of SIB18-1 and SIB18-2. The system information area ID for SIB18-1 is set to 11, and the system information area ID for SIB18-2 is set to 12. The cell broadcasts SIB18-1, SIB18-2, and the system information area IDs set for each.

[0629] In this way, the cell can broadcast multiple pieces of system information by associating each piece with a system information area ID. The UE that receives the system information broadcast from the cell can recognize the system information associated with the multiple system information areas.

[0630] Another method is disclosed. In one SIB including the same type of information, a system information area ID is set for one or more pieces of information in the SIB. In this way, in one SIB, multiple system information area IDs can be set for each piece of information. In one SIB, different information can be set for each system information area ID.

[0631] Figures 48 and 49 are diagrams showing examples in which different information is set for each system information area ID in one SIB according to the fifth embodiment. In the first example shown in Figure 48, multiple system information area IDs are set in SIB18. Common TX pool 1 (commonTXpool1) is set for the setting of system information area ID=11, and common TX pool 2 (commonTXpool2) is set for the setting of system information area ID=12.

[0632] In the second example shown in Fig. 49, a system information area ID is set for each piece of information in SIB18. A system information area ID of 11 is set for common TX pool 1 (commonTXpool1), and a system information area ID of 12 is set for common TX pool 2 (commonTXpool2).

[0633] In this way, it becomes possible to set a plurality of different pieces of information and a system information area ID corresponding to each piece of information for the SIB.

[0634] This article describes how to set up an RP for SL communication.

[0635] A cell sets one or more effective areas. When effective areas are set in multiple cells, the combination of multiple cells to which each effective area is set may be different. The target for which one cell sets one or more effective areas may be limited to the effective area for the RP for SL. The effective areas may be set so that all effective areas are not different between adjacent cells.

[0636] The above-mentioned system information area ID may be used to set the effective area of ​​the RP. The effective area may be associated with the system information area ID. The cell may set the effective area of ​​one or more RPs using the system information area ID. Alternatively, the above-mentioned method of setting the system information area ID may be appropriately applied to the setting of the effective area of ​​the RP. An effective area ID may be provided. The effective area ID may be used instead of the system information area ID. The cell may broadcast the effective area of ​​one or more RPs set to the SIB. In this way, multiple effective areas can be set for one cell.

[0637] A UE (UE-TX) performing SL communication may search all RPs configured in the SIB to select resources to be used for SL communication. If multiple system information area IDs are configured, it may search all RPs corresponding to the configured system information area IDs. During HO, the UE-TX searches and selects resources to be used for SL communication in the target cell using an RP that has the same system information area ID as the source cell configured, and performs scheduling for SL communication.

[0638] When HO is activated, for example, when an HO command is received from a source cell, the UE-TX may search all RPs set in the SIB. Alternatively, the UE-TX may search all RPs set in the SIB when the communication quality with the cell deteriorates. For example, when the communication quality with the cell falls below a predetermined threshold, the UE-TX may search all RPs set in the SIB. By searching all RPs, the UE-TX does not need to change the RP in the cell where HO is performed.

[0639] After completing HO, the UE-TX searches all RPs set in the SIB in the target cell to select resources to be used for SL communication. If multiple system information area IDs are set, it is advisable to search all RPs corresponding to the set system information area IDs. In this way, it is not necessary to change the RP during HO. After completing HO, the UE-TX can perform SL communication in the target cell using an RP different from the RP used during HO.

[0640] The cell may notify the UE of the above-mentioned system information area ID by individual signaling. The system information area can be set individually for each UE. The cell may notify the UE of the above-mentioned effective area by individual signaling. The effective area can be set individually for each UE.

[0641] Activation / deactivation may be performed for the system information area ID. Information indicating activation / deactivation of the system information area ID may be provided. Activation / deactivation may be performed for the valid area. Information indicating activation / deactivation of the valid area may be provided.

[0642] For example, the cell broadcasts multiple system information area IDs to the UE-TX. The cell sets a specific system information area ID to activation and notifies the UE-TX of the setting by UE-specific signaling. By this notification, the UE-TX may enable the activated system information area ID and use the SIB. When deactivation is notified, the UE-TX disables the deactivated system information ID and does not use the SIB. The number of the specific system information area IDs may be one or more. In this way, the system information area to be set for the UE can be flexibly changed.

[0643] For example, a cell notifies a plurality of effective areas to a UE-TX. The cell sets a specific effective area to activation or deactivation, and notifies the UE-TX of the setting by UE-specific signaling. The UE-TX may enable the activated effective area and use the RP. When deactivation is notified, the UE-TX disables the deactivated effective area and does not use the RP. In this way, the RP set for the UE can be flexibly changed.

[0644] It has been disclosed that the cell notifies the UE-TX of the system information area ID or the valid area, or the activation / deactivation by UE-specific signaling. The signaling may be RRC signaling. More information can be set. Alternatively, MAC signaling may be used. The above information may be included in the MAC CE and notified. HARQ is supported, and early and low reception error notification is possible. Alternatively, the above information may be included in the DCI and notified. Earlier notification is possible.

[0645] By using the method disclosed in the fifth embodiment, even if many UEs perform HO simultaneously, the SL communication resources are not concentrated on the exceptional RP. This makes it possible to reduce the increase in the delay time until communication and the occurrence of communication interruption due to RP congestion.

[0646] The above-described embodiments and their modifications are merely examples of the present disclosure, and the embodiments and their modifications can be freely combined within the scope of the present disclosure. In addition, any component of the embodiments and their modifications can be appropriately modified or omitted.

[0647] For example, in each of the above-mentioned embodiments and their modifications, a subframe is an example of a time unit of communication in a fifth generation base station communication system. It may be a scheduling unit. In each of the above-mentioned embodiments and their modifications, the processing described as a subframe unit may be performed in a TTI unit, a slot unit, a subslot unit, or a minislot unit.

[0648] For example, the methods disclosed in the above-described embodiments and their modified examples may be applied to services using SL communication, not limited to V2X (Vehicle-to-everything) services. For example, the methods disclosed in the above-described embodiments and their modified examples may be applied to SL communication used in various services, such as a proximity-based service, public safety, communication between wearable devices, and communication between devices in a factory.

[0649] Although the present disclosure has been described in detail, the above description is illustrative in all respects and does not limit the present disclosure. It is understood that countless variations not illustrated can be assumed without departing from the scope of the present disclosure. [Explanation of symbols]

[0650] 200, 210 communication system, 202 communication terminal device, 203 base station device.

Claims

1. A first communication terminal device communicating with a second communication terminal device, the first communication terminal device comprises a control unit and a transceiver; the first communication terminal device communicates directly with a base station device, and the second communication terminal device communicates with the base station device via the first communication terminal device; The control unit transmitting, using the transceiver, to a core network, a request for a policy for communicating with the second communication terminal device in sidelink communication; receiving the policy from the base station device using the transceiver; A first communication terminal device that communicates with the second communication terminal device in the side link communication using the policy.

2. The first communication terminal according to claim 1 , wherein the policy is received by the second communication terminal.

3. The first communication terminal device of claim 1 , wherein the control unit is configured to receive, using the transceiver, Quality of Service (QoS) parameters for the sidelink communication.

4. A second communication terminal device communicating with the first communication terminal device, the second communication terminal device comprises a control unit and a transceiver; the first communication terminal device communicates directly with a base station device, and the second communication terminal device communicates with the base station device via the first communication terminal device; The control unit transmitting, using the transceiver, to a core network, a request for a policy for communicating with the first communication terminal device in sidelink communication; receiving the policy from the base station device using the transceiver; A second communication terminal device that communicates with the first communication terminal device in the side link communication using the policy.

5. The second communication terminal according to claim 4 , wherein the policy is received by the first communication terminal.

6. The second communication terminal of claim 4, wherein the control unit is further configured to receive, using the transceiver, Quality of Service (QoS) parameters for the sidelink communication.

7. A base station device directly connected to a first communication terminal device and connected to a second communication terminal device via the first communication terminal device, The base station device includes a control unit and a transceiver, The control unit a core network, in response to receiving from the first communication terminal device a request for a policy for communicating with the second communication terminal device in side link communication, transmitting the policy to the first communication terminal device using the transceiver; A base station device, wherein the policy is used by the first communication terminal device to communicate with the second communication terminal device in the sidelink communication.

8. The base station apparatus according to claim 7 , wherein the control unit transmits the policy to the second communication terminal apparatus using the transceiver.

9. A base station device, a first communication terminal device, and a second communication terminal device, the first communication terminal device communicates directly with the base station device, and the second communication terminal device communicates with the base station device via the first communication terminal device; The first communication terminal device transmits a request for a policy for communicating with the second communication terminal device in sidelink communication to a core network; the base station device transmits the policy to the first communication terminal device in response to the core network receiving the request; the first communication terminal device receives the policy from the base station device; A communication system, wherein the first communication terminal device communicates with the second communication terminal device in the side link communication using the policy.

10. A base station device, a first communication terminal device, and a second communication terminal device, the first communication terminal device communicates directly with the base station device, and the second communication terminal device communicates with the base station device via the first communication terminal device; The second communication terminal device transmits a request for a policy for communicating with the first communication terminal device in sidelink communication to a core network; the base station device transmits the policy to the second communication terminal device in response to the core network receiving the request; the second communication terminal device receives the policy from the base station device; A communication system, wherein the second communication terminal device communicates with the first communication terminal device in the side link communication using the policy.

Images