Communication terminal, base station, and communication system

Abstract

To provide a low-latency and highly reliable wireless communication technique.SOLUTION: A communication system includes a plurality of communication terminals (UE) capable of communicating with each other in a sidelink, and a base station that wirelessly communicates with each of the plurality of communication terminals. An SLBWP, which is a bandwidth portion (BWP) for the sidelink, is set separately from a ULBWP, which is a bandwidth portion for an uplink.SELECTED DRAWING: Figure 35

Description

[Technical field]

[0001] The present invention 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, a base station pre-configures a portion of the carrier frequency band (hereinafter sometimes referred to as a Bandwidth Part (BWP)) for a 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] Also, 3GPP is considering several new technologies, such as time-sensitive networks (see Non-Patent Document 20 (3GPP RP-182090)), local caches (see Non-Patent Document 21 (3GPP RP-172726)), and preemption in side links (see Non-Patent Document 22 (3GPP R1-1810593)). [Prior art documents] [Non-patent literature]

[0056] [Non-Patent Document 1] 3GPP TS 36.300 V15.2.0 [Non-Patent Document 2] 3GPP S1-083461 [Non-Patent Document 3] 3GPP TR 36.814 V9.2.0 [Non-Patent Document 4] 3GPP TR 36.912 V15.0.0 [Non-Patent Document 5] "Scenarios, requirements and KPIs for 5G mobile and wireless system", ICT-317669-METIS / D1.1

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[0057] In 3GPP, support for a time sensitive network (TSN) is being considered in order to meet the requirements for ultra-reliable and low latency communication (URLLC) (see non-patent document 20 (3GPP RP-182090)). In a time sensitive network, time synchronization between multiple UEs is required (see non-patent document 23 (3GPP TR22.804 V16.1.0)). As a method of time synchronization between multiple UEs, time synchronization between a base station and each UE is being considered (see non-patent document 24 (3GPP R3-185808), non-patent document 25 (3GPP TS36.331 V15.3.0), and non-patent document 26 (3GPP R2-1817173)). However, when mobility occurs, the UE does not know the propagation delay between the UE and the destination base station, so the UE time may suddenly change before and after the mobility. This causes problems with malfunctions in systems that use TSN.

[0058] Also, in order to satisfy the requirement of low latency characteristics in NR sidelink (SL) communication, the introduction of preemption in NR SL communication has been proposed (see non-patent document 22 (3GPP R1-1810593) and non-patent document 27 (3GPP R1-1810775)). However, since a specific method of SL preemption is not disclosed, a problem occurs in that preemption cannot be implemented in SL communication, and the requirement of low latency characteristics cannot be satisfied.

[0059] In view of the above problems, one of the objects of the present invention is to provide a low-latency, highly reliable wireless communication technology in NR. [Means for solving the problem]

[0060] According to the present invention, there is provided a communication terminal in a communication system including a plurality of communication terminals capable of communicating with each other in a sidelink, and a base station that wirelessly communicates with each of the plurality of communication terminals, wherein a bandwidth portion (BWP) for the sidelink, that is, an SLBWP, is set separately from a bandwidth portion for an uplink, that is, an ULBWP.

[0061] Also, according to the present invention, there is provided a base station in a communication system including a plurality of communication terminals capable of communicating with each other in a sidelink, and a base station that wirelessly communicates with each of the plurality of communication terminals, wherein a bandwidth portion (BWP) for the sidelink, that is, an SLBWP, is set separately from a bandwidth portion for the uplink, that is, an ULBWP. Furthermore, according to the present invention, there is provided a communication system comprising a plurality of communication terminals capable of communicating with each other in a sidelink, and a base station that wirelessly communicates with each of the plurality of communication terminals, in which a bandwidth portion (BWP) for the sidelink, that is, an SLBWP, is set separately from a bandwidth portion for the uplink, that is, an ULBWP. Effect of the Invention

[0062] According to the present invention, it is possible to provide a low-latency, highly reliable wireless communication technology.

[0063] The objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description and the accompanying drawings. [Brief description of the drawings]

[0064] [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 a DC using gNB connected to an 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] FIG. 10 is a diagram showing an overview of the operation of UE time correction when handover occurs in the first embodiment. [Figure 15] FIG. 11 is a sequence diagram showing an operation of UE time correction when handover occurs in the first embodiment. [Figure 16] FIG. 11 is a sequence diagram showing another example of the operation of UE time correction when handover occurs in accordance with the first embodiment. [Figure 17] FIG. 11 is a sequence diagram showing an example in which a UE estimates the TA of a target base station when a handover occurs and performs an operation of correcting the UE time, in accordance with the first embodiment. [Figure 18] FIG. 11 is a sequence diagram showing an example of an operation of correcting time between base stations, in accordance with the first modification of the first embodiment. [Figure 19]A sequence diagram showing the operation of switching the PDU session used for data transmission and switching the base station to which the UE connects, for embodiment 2. [Figure 20] A sequence diagram showing the operation of switching the PDU session used for data transmission and switching the base station to which the UE connects, for embodiment 2. [Figure 21] A sequence diagram showing another example of the operation of switching a PDU session used for data transmission and switching a base station to which a UE connects, for embodiment 2. [Figure 22] A sequence diagram showing another example of the operation of switching a PDU session used for data transmission and switching a base station to which a UE connects, for embodiment 2. [Figure 23] FIG. 13 is a diagram showing an overview of preemption in SL communication in accordance with the fourth embodiment. [Figure 24] FIG. 13 is a diagram showing a first example of a preemption method in SL communication according to the fourth embodiment. [Diagram 25] FIG. 13 is a diagram showing a second example of a preemption method in SL communication according to the fourth embodiment. [Figure 26] FIG. 13 is a diagram showing a third example of a preemption method in SL communication according to the fourth embodiment. [Figure 27] FIG. 13 is a diagram showing a fourth example of a preemption method in SL communication according to the fourth embodiment. [Figure 28] FIG. 13 is a diagram showing an overview of preemption in SL communication in accordance with a first modification of the fourth embodiment. [Figure 29] FIG. 13 is a diagram showing a first example of a preemption method in SL communication according to a first modification of the fourth embodiment. [Diagram 30] FIG. 13 is a diagram showing a second example of a preemption method in SL communication according to the first modification of the fourth embodiment. [Diagram 31] FIG. 13 is a diagram showing a third example of a preemption method in SL communication according to the first modification of the fourth embodiment. [Diagram 32]FIG. 13 is a diagram showing a case where SLRP is set in the UL carrier of Uu in accordance with the fifth embodiment. [Diagram 33] FIG. 13 is a diagram showing a case in which preemption is permitted for SL communication with respect to UL resources of Uu in accordance with the fifth embodiment. [Diagram 34] FIG. 13 is a diagram showing a case in which preemption is permitted for resources in an SLRP for UL communication of Uu, in accordance with the fifth embodiment. [Diagram 35] FIG. 23 is a diagram showing a case in which two SLRPs and an SLBWP are configured within the same carrier, in accordance with the sixth embodiment. [Diagram 36] FIG. 23 is a conceptual diagram showing support for SUL in addition to non-SUL in SL according to the seventh embodiment. [Figure 37] FIG. 23 is a diagram showing a case in which the numerology is the same for non-SUL and SUL, in accordance with the seventh embodiment. [Figure 38] FIG. 23 is a diagram showing a case in which the numerology is made different between non-SUL and SUL in the seventh embodiment. [Figure 39] FIG. 23 is a diagram showing an example of a sequence for performing SL communication in an SL SUL in the seventh embodiment. [Diagram 40] FIG. 23 is a diagram showing an example of a sequence for performing SL communication in an SL SUL in the seventh embodiment. [Diagram 41] FIG. 23 is a diagram showing another example of a sequence for performing SL communication in an SL SUL in accordance with the seventh embodiment. [Diagram 42] FIG. 23 is a diagram showing another example of a sequence for performing SL communication in an SL SUL in accordance with the seventh embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0065] 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.

[0066] 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."

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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."

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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).

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] The control plane control unit 505 includes a NAS security unit 505-1, an SAE bearer control unit 505-2, an idle state mobility management unit 505-3, etc., and performs 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.

[0094] 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.

[0095] FIG. 11 is a block diagram showing the configuration of 5GC. FIG. 11 shows the configuration of the 5GC unit 214 shown in FIG. 3 described above. FIG. 11 shows 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.

[0096] If the data received from the Data Network is control data, the control data is passed from the Data Network communication unit 521 to the session management unit 527 via the user plane 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.

[0097] The control plane control unit 525 includes a NAS security unit 525-1, a PDU session control unit 525-2, an idle state mobility management unit 525-3, etc., and performs 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.

[0098] The 5GC unit 214 distributes paging signals to one or more base stations 203 and / or base station 213. The 5GC unit 214 also performs mobility control in an idle state. The 5GC unit 214 manages a tracking area list when the mobile terminal is in an idle state, an inactive state, 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.

[0099] 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.

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

[0101] Next, in step ST602, for the synchronized cell, a cell-specific reference signal (CRS), which is a reference signal (RS) transmitted from the base station for each cell, is detected and the RS received power (Reference Signal Received Power: RSRP) is measured. 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.

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

[0103] 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.

[0104] Next, in step ST605, the DL-SCH of the cell is received based on the cell configuration information in the MIB, and SIB (System Information Block) 1 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).

[0105] Next, in step ST606, the communication terminal compares the TAC of the SIB1 received in step ST605 with the TAC portion of the tracking area identity (TAI) in the tracking area list that the communication terminal already holds. The tracking area list is also called a TAI list. The TAI is identification information for identifying a tracking area, and is composed of 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.

[0106] 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.

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

[0108] An apparatus constituting a core network (hereinafter sometimes referred to as a "core network side apparatus") updates the tracking area list based on 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.

[0109] 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.

[0110] 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.

[0111] 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.

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

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

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

[0115] FIG. 13 shows an example of a cell configuration in NR. In an NR cell, 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.

[0116] 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 more than one.

[0117] In time synchronization between a base station and a UE in TSN, the base station may broadcast information related to time synchronization to the UE, or may notify the UE individually. The information may be included in system information or RRC signaling, for example, signaling of downlink information notification (DL Information Transfer). The information may be time reference information (hereinafter, timing reference). The timing reference may be information combining information related to a specific system frame and time, for example, information indicating the time at the end of a specific system frame. The UE may set its own UE time using the information.

[0118] In the information included in the timing reference, information on a specific subframe may be combined with a time instead of a specific system frame, for example, information indicating the time at the end of the subframe. Alternatively, information on a specific slot may be combined with a time, for example, information indicating the time at the end of the slot, in the information included in the timing reference. Instead of the end time mentioned above, the start time may be used. This allows, for example, the UE to shorten the waiting time until the time, and as a result, the UE can quickly set its own UE's time.

[0119] The timing reference transmitted from the base station to the UE may be generated, for example, using time information acquired by the base station from a Global Navigation Satellite System (GNSS) or a Regional Navigation Satellite System (RNSS), or may be generated using time information signaled from a location information server to the base station, or may be generated using time information signaled by an upper network device (e.g., AMF and / or SMF) to the base station, or may be generated using time information acquired from a time server. For example, time synchronization in the entire communication system is possible when the base station transmits to the UE a timing reference using time information signaled by an upper network device to the base station.

[0120] The UE may correct its own UE time derived using the timing reference. The correction may be, for example, to correct a propagation delay between the base station and the UE. In the correction, for example, a timing advance (TA) may be used. In the communication system, for example, the TA may be regarded as a round-trip propagation delay time between the base station and the UE. The UE may add half the value of the TA to its own UE time and use the result as its own UE time after correction.

[0121] However, no time synchronization method is disclosed when UE mobility occurs. Therefore, when mobility occurs, the UE cannot smoothly synchronize with the destination base station. For example, if the TA between the destination base station and the UE is different from the TA between the pre-movement base station and the UE, the UE time may suddenly change when the TA is used to correct the UE time. This causes a problem of malfunction in a system using TSN.

[0122] Solutions to the aforementioned problems are disclosed below.

[0123] In correcting the UE's own time, the UE simultaneously applies the timing reference received from the target base station and the TA received from the target base station. In other words, the UE does not correct the UE's own time using only one of the timing reference and the TA.

[0124] The UE corrects its own UE time by simultaneously using both the timing reference of the destination base station and the TA of the destination base station. For example, the timing reference plus half the value of the TA may be used as the own UE time. The UE may use the own UE time derived using the timing reference and the TA from the source base station before the derivation.

[0125] The UE may hold the timing reference and / or TA received from the source base station. The holding may be performed, for example, during handover from the source base station to the destination base station, or after the handover. The holding after the handover may be performed, for example, until both the TA of the destination base station and the timing reference of the destination base station are received. The holding may be performed for the timing reference received from the source base station. The UE may derive its own UE time using the TA and the timing reference. The derivation may use the clock of the UE. The derivation of the UE time using the TA and the timing reference from the source base station may continue, for example, until the handover is completed. This allows the UE to maintain its own UE time, for example, even when the handover fails.

[0126] The UE may establish uplink synchronization with the destination base station before correcting the UE's own UE time using the timing reference and TA from the destination base station, or may establish uplink synchronization with the destination base station simultaneously with the correction of the UE's own UE time. In establishing the uplink synchronization, the UE may use the TA received from the destination base station. The UE may hold both the TA received from the destination base station and the TA received from the source base station. This allows, for example, the UE to quickly establish uplink synchronization with the destination base station while maintaining the UE's own UE time.

[0127] After correcting the UE time using the timing reference and TA from the destination base station, the UE may release the TA received from the source base station and the timing reference received from the source base station, which can reduce memory usage in the UE, for example.

[0128] Figure 14 is a diagram showing an overview of the operation of UE time correction when mobility occurs. In Figure 14, the times of the source base station and the destination base station are assumed to be synchronized with the reference time used as the reference in the 5G system. In Figure 14, a square surrounded by a solid line represents an SFN.

[0129] At timing 1401 shown in Fig. 14, it is assumed that the UE knows the propagation delay d1 from the source base station to the UE itself. The source base station notifies the UE of a timing reference indicating that the time at the end of a specific SFN is t1. At timing 1402, the UE sets the time of the UE itself at the time of receiving the signal at the end of the SFN as the time (t1+d1) obtained by adding the propagation delay d1 to the time t1 included in the timing reference.

[0130] Assume that the UE is handed over from the source base station to the destination base station at timing 1403 shown in Fig. 14. Assume that the UE knows the propagation delay d2 from the destination base station to the UE at timing 1404. The destination base station notifies the UE of a timing reference indicating that the time at the end of a specific SFN different from the above is t2. At timing 1405, the UE resets the time of the UE at the time of receiving the signal at the end of the SFN to the time t2 included in the timing reference plus the propagation delay d2 (t2+d2).

[0131] In FIG. 14, the case where the timing reference is information indicating the time at the end of a specific SFN is shown, but the time at the end of a specific subframe may be used, the time at the end of a specific slot may be used, the time at the end of a specific minislot may be used, or the time at the end of a specific symbol may be used. Instead of the time at the end, the time at the beginning may be used. In the above case, the square surrounded by the solid line in FIG. 14 may be a subframe, a slot, a minislot, or a symbol. This makes it possible to shorten the time from when the UE receives the timing reference to when the specific time included in the timing reference is reached. As a result, the UE can quickly perform time synchronization.

[0132] The base station may broadcast the timing reference or may notify the UE individually. For notifying the timing reference, system information, RRC dedicated signaling, MAC signaling, or L1 / L2 signaling may be used. As an example of a case where MAC signaling is used as the timing reference, information on the time at a predetermined timing (e.g., the start or end of a slot / minislot) of a slot or minislot including the MAC signaling may be included. As an example of a case where L1 / L2 signaling is used as the timing reference, information on the time at a predetermined timing (e.g., the start or end of a slot / minislot) of a slot or minislot including the L1 / L2 signaling may be included.

[0133] A UE in an RRC_INACTIVE state or an RRC_IDLE state may obtain a timing reference. The UE may obtain a timing reference, for example, by using system information broadcast from a base station. The UE may set its own UE time by using the timing reference. The UE may determine the uncertainty in its own UE time by using a cell radius of the base station. The cell radius may be broadcast by the base station, for example. This enables time synchronization, for example, in a communication system, regardless of the RRC state of the UE.

[0134] The timing reference notification from the base station to the UE may be a notification targeted only at the UE (e.g., a notification including the C-RNTI of the UE) or may be a notification to multiple UEs. The multiple UEs may be, for example, multiple UEs in a beam to which the UE belongs (e.g., all UEs in the beam, or some UEs in the beam). The multiple UEs may be all UEs. In the timing reference notification from the base station to the multiple UEs, for example, a group common PDCCH may be used. This allows, for example, the base station to notify many UEs of the timing reference, thereby improving the efficiency of the communication system.

[0135] The UE may request the base station to notify the timing reference. The request may be made, for example, by using a signaling of a system information request, for example, a PRACH including a random access preamble of the system information request, or may use RRC dedicated signaling. As an example of using RRC dedicated signaling, the request may be included in a signaling of an RRC reconfiguration complete, or new RRC dedicated signaling may be provided. Based on the request, the base station may notify the UE of the timing reference. This allows, for example, the UE to quickly acquire the timing reference without waiting for the system information broadcast period.

[0136] As another example of a request for a timing reference, the UE may make the request to an upper NW device. The upper NW device may be, for example, an AMF or an SMF. The request from the UE to the SMF may be made via the AMF. NAS signaling may be used for the request. The request may or may not include information on a base station that is to receive the timing reference. The upper NW device may use the request to instruct the base station to notify the UE of the timing reference. For example, signaling on the NG interface may be used for the instruction. The base station to which the upper NW device instructs may be the same as the base station indicated in the information included in the request from the UE to the upper NW device. The base station may use the instruction to notify the UE of the timing reference. This allows, for example, the upper NW device to control timing reference notification from the base station to the UE, thereby improving efficiency in the communication system.

[0137] As another example of the notification of the timing reference, NAS signaling may be used. The upper NW device may notify the UE of the timing reference. The upper NW device may be, for example, an AMF, an SMF, or a UPF. The SMF may provide the timing reference to the UE via the AMF. In the above case, the upper NW device may acquire the frame timing of the base station. The base station may notify the upper NW device of information regarding the frame timing. For example, the NG interface may be used for the notification. This makes it possible to establish synchronization between UEs under different base stations in a 5G system. As another example, a location information server may notify the UE of the timing reference. Instead of acquiring the frame timing, the upper NW device may acquire subframe timing, slot timing, minislot timing, or symbol timing.

[0138] Fig. 15 is a sequence diagram showing the operation of UE time correction when handover occurs. Fig. 15 shows an example in which both the source base station and the destination base station are NR base stations (gNBs). Fig. 15 also shows an example in which the UE acquires the timing reference from the destination gNB by signaling a downlink information notification (DLInformationTransfer) from the destination gNB. In Fig. 15, unless otherwise specified, it is assumed that the Xn interface is used for communication between the source gNB and the destination gNB.

[0139] In Step ST1501 shown in FIG. 15, the source gNB decides to hand over the UE to the target gNB. In Step ST1502, the source gNB notifies the target gNB of a handover request. In Step ST1503, the target gNB performs admission control.

[0140] In Step ST1504 shown in FIG. 15, the target gNB notifies the source gNB of an acknowledgment (Handover Request Acknowledge) to the handover request. In Step ST1505, the source gNB instructs the UE to perform a handover to the target gNB. For example, signaling of RRC reconfiguration may be used for the instruction. In Step ST1506, the UE switches the destination base station from the source gNB to the target gNB. In Step ST1506, the UE may use its own UE time derived using the timing reference and TA received from the source gNB. In Step ST1506, the UE may hold the timing reference and TA received from the source gNB.

[0141] In step ST1507 shown in FIG. 15, the UE transmits a PRACH to the target gNB. In step ST1508, the target gNB transmits a random access response (RAR) to the UE. The target gNB may include a TA and / or an uplink grant in the RAR of step ST1508 and notify the UE of the same. The UE may use the TA to establish uplink synchronization with the target gNB in ​​step ST1509. In step ST1509, the UE may not correct its own UE time. In step ST1510, the UE may use the uplink grant to notify the target gNB of information indicating that handover has been completed. The notification of the information may be performed using, for example, an RRC reconfiguration complete (RRCReconfigurationComplete).

[0142] In step ST1511 shown in FIG. 15, the target gNB notifies the UE of a timing reference. For this notification, RRC signaling, for example, downlink information notification (DL Information Transfer), may be used. In step ST1512, the UE performs its own UE time correction using the TA received in step ST1508 and the timing reference received in step ST1511. The time correction may be, for example, setting a time obtained by adding half the value of the TA to the time included in the timing reference as the time at the point in time specified by the timing reference. In step ST1512, the UE may discard the timing reference of the source gNB and the TA of the source gNB.

[0143] In FIG. 15, an example in which RRC dedicated signaling is used to notify the timing reference is shown, but system information may be used to notify the timing reference. The UE may obtain the timing reference using the system information. This makes it possible to reduce the amount of signaling from the target gNB to the subordinate UE, for example.

[0144] Step ST1510 shown in FIG. 15 illustrates a case where the UE notifies the target gNB of information indicating that handover has been completed. The notification may include a timing reference notification request from the UE to the target gNB. For example, information related to the timing reference notification request may be included in signaling of RRC reconfiguration complete (RRCReconfigurationComplete) transmitted from the UE to the target gNB. The target gNB may notify the UE of the timing reference using the request. This allows, for example, the target gNB to quickly notify the UE of the timing reference.

[0145] The timing reference of the target base station may be notified to the UE before the handover. The target base station may notify the source base station of the timing reference of its own gNB. For the notification, signaling in an inter-base station interface (e.g., an Xn interface) may be used. For example, the timing reference may be included in a signaling of a handover request acknowledgment and notified. The source base station may notify the UE of the timing reference of the target base station using the signaling of the response. For example, the source base station may notify the UE of the timing reference of the target base station by including the timing reference in a signaling of a handover instruction (e.g., RRC reconfiguration). The UE may obtain the timing reference of the target base station using the signaling of the instruction. The UE may correct its own UE time using a TA received from the target base station and the timing reference. The correction may be performed, for example, after receiving the TA. This allows, for example, the UE to quickly perform its own UE time correction.

[0146] Fig. 16 is a sequence diagram showing another example of the operation of UE time correction when handover occurs. Fig. 16 shows an example in which both the source base station and the destination base station are NR base stations (gNBs). Fig. 16 also shows an example in which the UE acquires a timing reference from the destination gNB by using a handover command. In Fig. 16, the same step numbers are assigned to processes common to Fig. 15, and common explanations are omitted.

[0147] Steps ST1501 to ST1503 shown in FIG. 16 are the same as those in FIG.

[0148] In Step ST1604 shown in FIG. 16, the target gNB notifies the source gNB of an acknowledgment (Handover Request Acknowledge) to the handover request. The target gNB notifies the source gNB of the response including the timing reference of its own gNB. In Step ST1605, the source gNB instructs the UE to perform a handover to the target gNB. The source gNB notifies the UE of the instruction including the timing reference of the target gNB. For example, signaling of RRC reconfiguration may be used for the instruction. In Step ST1506, the UE switches the connection destination base station from the source gNB to the target gNB. In Step ST1506, the UE acquires the timing reference of the target gNB from the handover instruction received in Step ST1605. In Step ST1506, the UE may use its own UE time derived using the timing reference received from the source gNB and the TA. In step ST1506, the UE may hold the timing reference and TA received from the source gNB.

[0149] Steps ST1507 to ST1509 shown in FIG. 16 are the same as those in FIG.

[0150] In Step ST1611 shown in Fig. 16, the UE corrects its own UE time by using the TA received in Step ST1508 and the timing reference received in Step ST1605. The method of correcting the time may be the same as the example disclosed in Fig. 15. In Step ST1611, the UE may discard the timing reference of the source gNB and the TA of the source gNB.

[0151] Step ST1510 shown in FIG. 16 is the same as that in FIG.

[0152] The UE may use only the latest timing reference among the timing references received multiple times. For example, when the UE receives both a timing reference broadcast from the base station and a timing reference notified individually, the UE may use only the timing reference received later. The UE may discard the timing reference received earlier. This may improve the accuracy of the UE time, for example.

[0153] Another solution is disclosed. The UE may estimate the TA of the destination base station. The UE may correct its own UE time using the estimated TA and a timing reference from the destination base station. The UE may estimate the TA of the destination base station using the difference between the propagation delay from the destination base station and the propagation delay from the source base station. The estimation in the UE may be applicable, for example, when the slot timing (or frame timing, the same applies below) at the time of transmission of the destination base station and the source base station is the same. The estimation in the UE may be applicable, for example, in mobility between TRPs (Transmission Reception Points). This allows the UE to correct its own UE time before starting a random access process, for example.

[0154] The UE may hold the slot timing of the source base station. The UE may hold the TA of the source base station. The UE may acquire the slot timing of the destination base station. The UE may derive the TA of the destination base station by using the difference between the slot timing of the destination base station and the slot timing of the destination base station, and the TA from the source base station. For example, the UE may estimate the TA from the destination base station by adding the doubled value of the difference between the slot timing of the destination base station and the slot timing of the destination base station to the TA from the source base station. This allows, for example, the UE to correct its own UE time before performing random access processing with the destination base station. In the above, the UE may not perform random access processing with the destination base station. The UE may establish uplink synchronization with the destination base station using the estimated TA. This allows, for example, the UE to quickly perform handover processing.

[0155] The handover command signaling from the source base station to the UE may include information on the frame timing of the source base station and the destination base station. The information may be, for example, information indicating whether the frame timing of both base stations is the same, information on whether TA estimation is performed, or information on the difference in frame timing between both base stations. The information on the difference may be information at the time of transmission from both base stations. The UE may or may not perform TA estimation using the information, and may decide whether or not to perform TA estimation. This allows, for example, the UE to quickly perform TA estimation.

[0156] The source base station may acquire information on the slot timing of the destination base station. The source base station may acquire the information, for example, by using a cell search. The source base station may derive information on the frame timing of the source base station and the destination base station using the acquired information. The information on the frame timing of the source base station and the destination base station may be the same as described above. The source base station may notify the UE of the derived information. As another example, the destination base station may acquire information on the slot timing of the source base station. The destination base station may acquire the information, for example, by using a cell search. The destination base station may notify the source base station of information on the slot timing of the source base station and the destination base station using the acquired information. For example, the source base station may notify the UE of the information. This allows, for example, the source base station or the destination base station to acquire information on the slot timing of each other's base station.

[0157] The UE may acquire the frame timing of the destination gNB. The acquisition operation in the UE may be performed, for example, during measurement. The UE may notify the source gNB of information on the acquired timing, or may notify information on the difference between the frame timing of the source gNB and the frame timing of the destination gNB. The above-mentioned notification may be included in a measurement result report from the UE to the source gNB, for example. The source gNB may use the notification to derive a TA for the connection between the destination gNB and the UE. The destination gNB may derive the TA and notify the source gNB of the TA. The source gNB may notify the UE of the TA. The notification may be included in a handover command from the source gNB to the UE, for example. This allows the UE to quickly acquire the TA, and as a result, the UE can quickly establish synchronization with the destination gNB.

[0158] FIG. 17 is a sequence diagram showing an example in which a UE estimates the TA of a destination base station when a handover occurs and performs an operation of UE time correction. FIG. 17 shows an example in which both the source base station and the destination base station are NR base stations (gNBs). FIG. 17 shows an example in which the frame timing of the source gNB and the destination gNB are the same. FIG. 17 also shows an example in which a UE obtains a timing reference from a destination gNB by using a handover command. In FIG. 17, the same step numbers are assigned to processes common to FIG. 15 and FIG. 16, and common explanations are omitted.

[0159] In step ST1701 shown in FIG. 17, the UE receives an SS block from the source gNB and acquires the frame timing of the source gNB.

[0160] Steps ST1501 to ST1503 shown in Fig. 17 are the same as those in Fig. 15. Steps ST1604, ST1605, and ST1506 are the same as those in Fig. 16.

[0161] In step ST1707 shown in FIG. 17, the UE receives an SS block from the target gNB and acquires the frame timing of the target gNB. In step ST1708, the UE estimates the TA at the target gNB using the frame timing of the source gNB acquired in step ST1701 and the frame timing of the target gNB acquired in step ST1707. In step ST1711, the UE corrects its own UE time using the TA estimated in step ST1708 and the timing reference received in step ST1605. The method of the time correction may be the same as the example disclosed in FIG. 15. In step ST1711, the UE may discard the timing reference of the source gNB and the TA of the source gNB.

[0162] Steps ST1507 to ST1509, ST1611, and ST1510 shown in FIG. 17 are the same as those in FIG.

[0163] 17 shows an example in which the UE performs its own UE time correction twice, which enables the UE to quickly acquire the time after handover, and to acquire highly accurate time by the second correction, for example.

[0164] Although an example in which the UE corrects its own UE time twice has been shown in Fig. 17, the UE may correct its own UE time only once. For example, step ST1611 shown in Fig. 17 may not be performed. This makes it possible to reduce the amount of processing in the UE, for example.

[0165] FIG. 17 shows an example in which the UE performs step ST1707 of receiving an SS block from the target gNB after step ST1506 of switching to the target gNB. In contrast, the UE may receive an SS block from the target gNB before switching to the target gNB. For example, the UE may receive an SS block from the target gNB and hold frame timing from the target gNB in ​​measurements before the handover decision in step ST1501. This allows the UE to quickly perform destination TA estimation after switching to the target gNB, for example.

[0166] The UE may perform its own UE time correction using only the TA from the destination gNB. The correction may be performed, for example, when the time is synchronized between the source gNB and the destination gNB. The source gNB may notify the UE of information regarding time synchronization with the destination gNB. The information may be, for example, information regarding the presence or absence of time synchronization, or information regarding the accuracy of time synchronization. The UE may perform its own UE time correction using the information regarding time synchronization and the TA from the destination gNB. This, for example, makes it unnecessary for the UE to receive a timing reference from the destination gNB, and as a result, the UE time correction can be performed quickly.

[0167] The UE may discard the received timing reference. For example, if the UE performs handover before the SFN included in the timing reference arrives, the UE may discard the timing reference. As another example, if the UE receives multiple timing references, the UE may discard the timing reference that is not the latest. This can, for example, prevent malfunction of the UE time.

[0168] When the UE performs handover before the SFN included in the timing reference arrives, the UE may set or correct its own UE time based on the SFN before the handover. This makes it possible to reduce, for example, signaling between the base station and the UE.

[0169] The UE may extend the uncertainty of its own UE time. The amount of extension of the uncertainty may be determined using the clock accuracy of the own UE. For example, the amount of extension of the uncertainty may be a value obtained by multiplying the clock error per unit time of the own UE by the elapsed time since the last time the own UE time was corrected or the last time the uncertainty extension was performed. The extension operation may be performed when a handover occurs or when a handover does not occur. For example, the extension operation may be performed while the timing reference is not received from the base station.

[0170] As another example, the UE may extend the uncertainty when a handover occurs. The extension may be performed when a timing reference is received from the destination base station, or when a TA from the destination base station is not received. For example, the UE may add a time value corresponding to a propagation delay of a distance of half the cell radius of the destination base station to the uncertainty. The UE may assume that the TA from the destination base station is a time value corresponding to a propagation delay of a distance of half the cell radius. The UE may correct the UE time using the timing reference from the destination base station and the assumed TA. This allows the UE to quickly derive the UE time after a handover, for example.

[0171] The method in the first embodiment may be applied to inter-DU mobility and / or inter-TRP mobility other than the handover exemplified as inter-base station mobility. This makes it possible to prevent the time of UE from suddenly changing in mobility, even when a base station has a plurality of DUs and / or TRPs. As a result, it is possible to prevent malfunction in the communication system.

[0172] Here, the base station, the DU, and the TRP have in common that they are communication devices configured to be able to wirelessly communicate with the UE. Therefore, the mobility between base stations, the mobility between DUs, and the mobility between TRPs can also be referred to as the mobility between communication devices.

[0173] The method in the first embodiment may be applied to the movement of a UE between communication devices. For example, when the TA is changed, the method in the first embodiment may be applied. The UE may simultaneously use the changed TA and the timing reference received after the TA change to correct its own UE time. This makes it possible to prevent a sudden change in the own UE time when, for example, the TA is changed, and as a result, it becomes possible to prevent malfunctions in the communication system.

[0174] During the movement between communication devices, the UE may correct its own UE time using the difference in downlink frame timing between the previous correction of its own UE time and the changed TA, and the changed TA. When deriving the difference, the UE may retain information on the downlink frame timing at the previous correction of its own UE time. The correction may be performed before the UE receives a timing reference after changing the TA. This allows, for example, the UE to quickly correct its own UE time after receiving the changed TA.

[0175] According to the first embodiment, it is possible to prevent a sudden change in UE time when mobility occurs, and as a result, it is possible to prevent malfunctions in a system using TSN.

[0176] Variation 1 of the first embodiment Time synchronization between a base station and a UE in TSN may be applied when using DC.

[0177] Each time the UE receives a timing reference from the master base station and / or the secondary base station, the UE performs its own UE time correction.

[0178] The UE may prioritize the timing reference from the master base station, e.g., the UE may discard the timing reference transmitted from the secondary base station, which may, e.g., avoid complexities in the communication system.

[0179] As another example, the UE may prioritize a timing reference from a secondary base station. For example, when the master base station is an eNB and the secondary base station is a gNB, the UE may prioritize a timing reference from the secondary base station. The gNB may be more accurate than the eNB. This allows, for example, the UE time to be maintained with high accuracy.

[0180] As another example, the UE may decide which of the base stations to prioritize the timing reference from. For example, information on the accuracy of the time of each base station may be used for the decision in the UE. For example, the UE may prioritize the timing reference from the base station with higher accuracy. The information on accuracy may be, for example, information on the uncertainty included in the timing reference. This may, for example, improve the accuracy of the UE time.

[0181] As another example, the base station itself may determine which base station to prioritize the timing reference from and notify the UE. In the notification, RRC signaling, MAC signaling, or L1 / L2 signaling may be used. The base station making the decision may be the master base station or the secondary base station. For example, information on the accuracy of the time of each base station may be used for the decision in the base station. For example, the master base station may decide to prioritize the timing reference from the base station with high accuracy. The information on the accuracy may be, for example, information on the uncertainty included in the timing reference. This makes it possible to improve the accuracy of the UE time, for example.

[0182] As another example of the determination in the UE, the validity period of the timing reference disclosed in the second modification of the first embodiment may be used. For example, the UE may prioritize the timing reference from the base station with the longer validity period. This can provide, for example, the same effect as described above. The same may be applied to the determination in the base station.

[0183] As another example of the determination in the UE, the maximum value of the validity period may be used. The master base station and / or the secondary base station may inform the UE of information on the maximum validity period of the timing reference, or may notify the UE individually. This makes it possible to prevent, for example, the phenomenon that the base station determined by the UE alternates due to timing reference updates over time. The same may be used in the determination in the base station.

[0184] As another example, the upper NW device may notify the UE of information regarding which base station the UE uses as a timing reference. The upper NW device may be a 5G core device, such as an AMF or an SMF. As another example, the upper NW device may be an EPC, such as an MME. The notification may be, for example, NAS signaling, or a combination of signaling in the interface between the upper NW device and the base station and signaling in the interface between the base station and the UE (for example, RRC signaling, MAC signaling, L1 / L2 signaling).

[0185] As another example, the UE may hold multiple times. For example, the UE may hold both a time set and / or corrected using a timing reference from a master base station and a time set and / or corrected using a timing reference from a secondary base station. This makes it possible to prevent a sudden change in the UE time even when the time is different between the master base station and the secondary base station. As a result, it is possible to prevent malfunctions in the communication system.

[0186] As another example of the UE holding multiple times, a different UE time may be provided for each service requirement used by the UE. For example, the UE may hold a UE time for each different network slicing. This allows, for example, time management for different service requirements used by the UE to be flexibly performed.

[0187] The timing reference information may include information about the source base station. The master base station and / or the secondary base station may include information about the base station in the timing reference information and notify the UE. The information about the base station may be, for example, an identifier indicating whether the base station is the master base station or the secondary base station. The UE may use the information about the source base station to identify the base station that is the source of the timing reference.

[0188] The timing reference information may not include information about the source base station. The UE may use information about the communication path with the base station, such as information about the bearer used, to determine which time the data is associated with. This can, for example, avoid complexity in the communication system.

[0189] Information indicating which base station's timing reference is used for the time may be included or added to data transmitted from the base station to the UE. The inclusion or addition of the information may be performed by, for example, the UPF, the AMF, or the base station. When the base station includes or adds the information, the inclusion or addition of the information may be performed by the RRC layer, the SDAP layer, a layer higher than the RRC layer or the PDCP layer, the RLC layer, or the MAC layer. The base station may notify the UE of the information by using RRC signaling, by being included in the SDAP header, by being included in the PDCP header, as a PDCP control PDU, by being included in the RLC header, as an RLC control PDU, as a MAC header, as MAC signaling, or as L1 / L2 signaling. The UE may use the information to determine which time the data is associated with.

[0190] The UPF or the AMF may determine which base station uses the timing reference from which the data is processed. For example, the UPF may determine the U-plane data, the AMF may determine the C-plane data, or the AMF may determine both the U-plane data and the C-plane data. In the determination, for example, information on the accuracy of the time of each base station may be used. The information may be, for example, information on uncertainty included in the timing reference. The information on the accuracy may be notified from each base station to the UPF and / or the AMF, or the UE may notify the AMF. In the notification from each base station to the UPF and / or the AMF, the NG interface may be used. In the notification from the UE to the AMF, NAS signaling may be used. The AMF may notify the UPF of the information, or may notify the UPF of information on the determination. The notification from the AMF to the UPF may be performed via the SMF. The UPF and / or the AMF may determine to use the time of a base station having a highly accurate time, for example. This enables, for example, highly accurate time synchronization between UEs.

[0191] As another example, data transmitted from a base station to a UE may not include information indicating which base station's timing reference is used at the time. The UE may determine which time the data is associated with by using information on a communication path with the base station, for example, information on a bearer used.

[0192] As another example of a time correction method in the UE, the UE may expand the uncertainty of its own UE time. For example, the UE may use a range including a time derived using a timing reference from a master base station and a time derived using a timing reference from a secondary base station as the uncertainty of its own UE time. The UE may set its own UE time to a value between the two times, for example, the median value of the two times. This makes it possible to avoid, for example, complexity in the design of the communication system.

[0193] Another solution is disclosed. The UE may request a base station to correct its time. The base station may be a master base station or a secondary base station. When the UE transmits a time correction request to the secondary base station, the UE may transmit the request directly to the secondary base station, or may transmit the request to the secondary base station via the master base station. The base station may use the request to correct its own time.

[0194] The UE may determine a base station to be subjected to time correction using information on timing references from each base station. In determining a base station to be subjected to correction, for example, a base station with low accuracy may be set as a correction target. This makes it possible to perform time synchronization with a base station with high accuracy, for example, and as a result, synchronization between UEs in a communication system can be performed with high accuracy. As another example of determining a base station to be subjected to correction, a base station with high accuracy may be set as a correction target.

[0195] As another example of the time correction of the base station, the UE may notify the upper NW device of a correction request for the time of the base station. The upper NW device may be, for example, the AMF. For example, NAS signaling may be used for the notification from the UE to the upper NW device. The upper NW device may notify the base station of the request. The base station may use the notification to correct the time of its own base station.

[0196] As another example, the base station may notify the upper NW of information related to the time of the base station. The upper NW device may be, for example, an AMF. The upper NW device may use the information to notify the base station of a time correction request. The base station may use the notification to correct the time of the base station.

[0197] The request may include information indicating that it is a request for time correction, may include information about the base station to which the time is to be corrected, or may include information about the amount of time correction. The information about the base station to which the time is to be corrected may be, for example, an identifier indicating whether the base station is a master base station or a secondary base station. The information about the amount of time correction may be given, for example, as a correction amount in a predetermined time unit. The base station may correct its own time using the information included in the request. The base station may notify the UE of information indicating that the correction has been completed. The notification of the completion information may be performed via the other base station or via an upper NW device.

[0198] Time correction may occur between base stations, for example, using a request from the UE.

[0199] The base station to which the time is to be corrected may broadcast or notify the UE under its control of a timing reference using the corrected time. The UE under its control may then correct its own UE time using the timing reference. This allows, for example, time synchronization between UEs in a communication system.

[0200] Fig. 18 is a sequence diagram showing an example of the operation of correcting the time between base stations. Fig. 18 shows an example in which a UE requests a master base station (MN) to correct the time of a secondary base station (SN). Fig. 18 shows an example in which an MN requests an SN to correct the time. In Fig. 18, it is assumed that the UE has already acquired TA from the MN and the SN.

[0201] In step ST2001 shown in FIG.18, the MN notifies the UE of a timing reference. The UE uses the timing reference from the MN to derive UE time (hereinafter, may be referred to as UE time referred to by the MN). In step 2002, the SN notifies the UE of the timing reference. The UE uses the timing reference from the SN to derive UE time (hereinafter, may be referred to as UE time referred to by the SN).

[0202] In step ST2003 shown in FIG.18, the UE compares the UE time referred to the MN with the UE time referred to the SN. The comparison of both UE times may be performed, for example, by using whether or not there is an overlap between the UE time referred to the MN and its uncertainty range and the UE time referred to the SN and its uncertainty range. For example, when there is an overlap, the UE may determine that both UE times match.

[0203] If both UE times match in step ST2003 shown in FIG. 18, the UE returns to the operation of receiving timing references of both base stations in step ST2001 and step ST2002 in step 2004. If both UE times are different in step ST2003, the UE transmits a correction request for the SN time to the MN in step ST2005. The request may include information indicating that the correction target is the SN, or may include information regarding the amount of time correction. The UE may derive the amount of correction using the difference between both UE times.

[0204] In step ST2006 shown in Fig. 18, the MN requests the SN to correct its time. The request may include information on the amount of correction of the SN time. The information may be the amount of correction that the MN acquired from the UE in step ST2005. In step ST2007, the SN corrects the time of its own base station using the information on the amount of time correction acquired in step ST2006.

[0205] In step ST2008 shown in Fig. 18, the SN notifies the MN of the completion of the time correction of its own base station. In step ST2009, the MN notifies the UE of an acknowledgment to the SN time correction request. The notification in step ST2009 may be a notification indicating the completion of the SN time correction.

[0206] Steps ST2010 and ST2011 shown in Fig. 18 are the same as steps ST2001 and ST2002. In step ST2011, the SN notifies the timing reference by using the corrected time. The UE derives the MN-referred UE time and the SN-referred UE time by using the timing references acquired in steps ST2010 and ST2011, respectively.

[0207] Another solution is disclosed. The UE may set its own UE time in a range where the UE time and the uncertainty range of the time obtained using the timing reference from the master base station overlap with the UE time and the uncertainty range of the time obtained using the timing reference from the secondary base station. For example, the UE may set its own UE time to the median value of the overlapping range, or may define a range including the overlapping range as the uncertainty range of the own UE time. This allows the UE to improve the accuracy of its own UE time by using timing references from two base stations, for example.

[0208] The method of correcting the time of the base station disclosed in the first modification of the first embodiment may be applied to handover, which makes it possible to realize time synchronization between base stations, for example.

[0209] As an example of time correction of a base station at the time of handover, the time of the source base station may be corrected. The UE may request the destination base station to correct the time of the source base station. The UE may notify the destination base station of the request after the UE acquires the timing reference and TA of the destination base station. The UE may correct its own UE time before notifying the destination base station of the request, after the notification, or simultaneously with the notification. The destination base station may request the source base station to correct its time. The information included in the request from the UE to the destination base station and the request from the destination base station to the source base station may be the same as the information disclosed above. The source base station may correct the time of its own base station using the request from the destination base station.

[0210] As another example, the time of the destination base station may be corrected. The UE may request a time correction from the destination base station. The request from the UE to the destination base station may be notified after the UE acquires the timing reference and TA of the destination base station. The information included in the request from the UE to the destination base station may be the same as the information disclosed above. The destination base station may correct the time of its own base station using the request from the UE. The UE may correct its own UE time using the corrected timing reference and TA from the destination base station.

[0211] The UE may determine whether to correct the time of the source base station or the destination base station during handover. For example, the time of the base station with the lower time accuracy may be corrected. As another example, the source base station or the destination base station may be determined.

[0212] The upper NW device may instruct the base station to correct the time of the base station during handover. The UE may notify the upper NW device of information on the time correction from each base station. For example, NAS signaling may be used for the notification. The method of correcting the time of the base station using the instruction from the upper NW device to the base station may be the same as the method of correcting the time using the upper NW device in the above-mentioned DC.

[0213] As another example, the UE may determine its own UE time using both the timing reference from the destination base station and the timing reference from the source base station. For example, the UE may determine its own UE time in a range where the own UE time and the uncertainty range of the time obtained using the timing reference from the destination base station overlap with the own UE time and the uncertainty range of the time obtained using the timing reference from the destination base station. This makes it possible to improve the time accuracy in the UE, for example.

[0214] The method of correcting the time of a base station disclosed in this first modification of the first embodiment may be applied to correcting the time of a base station adjacent to a UE. The base station may be a base station to which the UE is not connected. The application of the above method may be applied when the difference in frame timing between the adjacent base station and the base station to which the UE is connected is known in any device in the communication system.

[0215] The UE may acquire a timing reference of the neighboring base station. The timing reference acquired by the UE may be broadcast from the neighboring base station. The UE may estimate the TA of the neighboring base station by using the frame timing of the neighboring base station. The estimation may be performed by the method disclosed in the first embodiment. The UE may request a time correction of the neighboring base station from a base station to which the UE is connected. The request may be made by RRC signaling, MAC signaling, or L1 / L2 signaling. The base station to which the UE is connected may request a time correction from the neighboring base station. Information included in the request from the UE to the connected base station and information included in the request from the base station to which the UE is connected to the neighboring base station may be the same as the information disclosed in the present modification 1 of the first embodiment. The neighboring base station may correct the time of its own base station by using the request from the base station to which the UE is connected.

[0216] In time correction of neighboring base stations, the upper network device may instruct the base station to do so, similar to time correction of a base station during handover.

[0217] As another example, the UE may determine its own UE time using a timing reference from a destination base station and a timing reference from a neighboring base station. For example, the UE may determine its own UE time in a range where the own UE time and the uncertainty range of the time obtained using the timing reference from the destination base station overlap with the own UE time and the uncertainty range of the time obtained using the timing reference from the neighboring base station. In the above, the neighboring base station may be one or more. This makes it possible to improve the time accuracy in the UE, for example.

[0218] The method in the first modification of the first embodiment may be applied to the movement of a UE between communication devices. For example, when a UE receives timing references from multiple DUs, the UE may determine its own UE time using the timing reference from the DU with the highest accuracy of the timing reference, or the UE may determine its own UE time and uncertainty range in a range where the own UE time and its uncertainty range obtained using the timing references from both DUs overlap. This makes it possible to improve the accuracy of the UE time, for example.

[0219] As another example, a UE immediately before handover may communicate with a source base station using a DU with a long validity period of a timing reference among connectable DUs. This makes it possible to prevent, for example, deterioration of the accuracy of the UE's own time during handover of the UE.

[0220] According to this first modification of the first embodiment, the base station with which the UE is time-synchronized becomes clear, and as a result, it is possible to prevent malfunctions in the communication system. Also, in the DC, it is possible to correct the time error between the base stations, and as a result, it is possible to increase the number of UEs that can be time-synchronized in the communication system.

[0221] Variation 2 of embodiment 1 In NR, beamforming is used, so the gNB needs to notify the UE of the timing reference in multiple beam directions. Therefore, it takes time for the base station to transmit the timing reference to the UE. As a result, for example, if the clock accuracy of the UE is low, the error of the UE time may increase.

[0222] A method for solving the aforementioned problems is disclosed.

[0223] A validity period of the timing reference is set. The validity period may be set in the UE. The validity period may be determined in advance by a standard. The validity period may be, for example, a fixed value or may be determined using the clock accuracy of the UE. Information regarding the validity period may be included in the UE capabilities. The information may be, for example, the validity period or information regarding the clock accuracy of the UE.

[0224] A timer for the validity period may be provided. The timer may be provided in the base station. The UE may notify the base station of information regarding the validity period. The notification may be, for example, a notification of UE capabilities. The base station may use the notification to set a timer for the validity period of the timing reference in the UE. The timer may be initialized and started by a notification or broadcast of the timing reference from the base station to the UE. The base station may notify the UE of the timing reference when the timer expires. This makes it possible to prevent, for example, an increase in an error in the UE time.

[0225] A timer for the validity period may be provided in the UE. The UE may initialize and start the timer by receiving a timing reference broadcast or notified from the base station. The UE may request a timing reference from the base station when the timer expires. The request may be made by RRC signaling, MAC signaling, or L1 / L2 signaling. The base station may notify the UE of the timing reference using the request. This makes it possible to prevent, for example, an increase in error in the UE time.

[0226] Another solution is disclosed. The UE may always acquire the timing reference that is periodically broadcast. The base station may broadcast or notify the UE of the broadcast cycle of the timing reference in advance. This makes it possible to prevent, for example, an increase in the error of the UE time.

[0227] As another example, the UE may acquire the timing reference that is periodically broadcast in some broadcast cycles. For example, the UE may acquire the timing reference every several cycles. The number of cycles may be determined using, for example, the clock accuracy in the UE. This may eliminate the need for the UE to perform a reception operation for some timing reference broadcasts, thereby reducing power consumption in the UE.

[0228] The UE may notify the base station of information regarding whether or not individual notification of the timing reference is required. For example, when time accuracy can be sufficiently maintained by only receiving the periodically notified timing reference, the UE may notify the base station that individual notification of the timing reference is not required. The information may be included in, for example, the UE capabilities. The base station may use the information not to notify the UE of the timing reference individually. This may, for example, improve the efficiency of the communication system.

[0229] The timer in the present modified example 2 of the first embodiment may be applied to the validity period and / or the TA. The validity period and / or the timer of the TA may be provided as a timer different from the timeAlignmentTimer described in Non-Patent Document 17 (3GPP TS 38.321 V15.2.0). The validity period and / or the timer may be set to a value shorter than the above-mentioned timeAlignmentTimer. The setting method and operation of the timer of the TA may also be the same as the timer of the timing reference. For example, the base station may notify the UE of the TA when the timer in the TA expires. The UE may correct its own UE time using the TA. As another example, the value of the timer may be determined using the moving speed of the UE. The moving speed may be, for example, the moving speed in the radial direction of the cell. This allows, for example, the base station to quickly grasp the TA change caused by the UE movement, and as a result, the accuracy of the UE time can be maintained.

[0230] The base station may obtain the moving speed of the UE by using the uplink RS. For example, the moving speed of the UE may be derived by using the Doppler shift amount of the uplink RS. The uplink RS may be, for example, a DMRS, an SRS, or a PTRS. As another example, the uplink RS may be an RS for positioning.

[0231] Both the timing reference timer and the TA timer may be used, which may, for example, further improve the accuracy of the UE time.

[0232] According to this second modification of the first embodiment, it is possible to prevent an increase in time error caused by a clock error in the UE.

[0233] Embodiment 2 In communication of U-plane data and / or C-plane data in TSN, latency may be constant.

[0234] However, when mobility such as handover occurs, there is a problem that latency varies when the mobility occurs and before and after the occurrence. In addition, there is a problem that latency in communication between the base station and the UE varies due to a shortage of frequency resources and / or time resources in the base station.

[0235] A method for solving the aforementioned problems is disclosed.

[0236] The UE communicates using a plurality of PDU sessions. The plurality of PDU sessions may be provided on a path passing through a master base station and a path passing through a secondary base station, respectively. The plurality of PDU sessions may be set for one network slicing. The UE transmits and receives data in a PDU session passing through a base station where no mobility occurs. The PDU session through which data is transmitted and received may be switched between the plurality of PDU sessions.

[0237] For example, when the master base station is switched, the UE may switch the uplink data transmission path to a path passing through the secondary base station, and the UPF may switch the downlink data transmission path to a path passing through the secondary base station.

[0238] As another example, when the secondary base station is switched, the UE may switch the uplink data transmission path to a path passing through the master base station, and the UPF may switch the downlink data transmission path to a path passing through the master base station.

[0239] The master base station may instruct the UE to switch the uplink data transmission path. The master base station may be the previous master base station when the master base station is switched. The instruction may include information indicating which base station to use as the path, or may include information on the data to be the target of the path switching. The information on the data to be the target of the path switching may be, for example, information on the QoS flow, information on the bearer, or information on the PDU session. The UE may use the instruction to switch the path used for uplink data transmission. This makes it possible to switch the transmission path only for data that requires the transmission path switching, and as a result, it is possible to prevent congestion in the transmission path to be switched to.

[0240] The UE may transmit a response to the instruction to the master base station, which makes it possible to prevent, for example, a discrepancy in an uplink data communication path between the UE and the master base station, and as a result, to prevent malfunctions in the communication system.

[0241] After the switching instruction, the UE may receive the downlink data from the base station before the switching, or from the base station after the switching. This makes it possible to prevent the loss of downlink data before and after switching of the downlink data transmission path in the UPF, for example.

[0242] The instruction from the master base station to the UE may be RRC signaling. For example, the instruction may be included in signaling of RRC reconfiguration. This makes it possible to avoid design complexity in the communication system, for example. As another example, the instruction may be MAC signaling. For example, a MAC CE for switching the path may be provided. This makes it possible for the master base station to quickly notify the UE of switching the uplink data transmission path. As another example, the instruction may be L1 / L2 signaling. This makes it possible for the master base station to more quickly notify the UE of the switching.

[0243] The response from the UE to the master base station may be RRC signaling, MAC signaling, or L1 / L2 signaling, for example, RRCReconfigurationComplete signaling, a HARQ response to the MAC CE containing the indication, or other signaling.

[0244] The master base station may instruct the AMF to switch the downlink data transmission path in the UPF. The master base station may be the original master base station when the master base station is switched. The AMF may transfer the instruction to the UPF. The instruction may be transferred from the AMF to the UPF via the SMF. The instruction may include information indicating which base station to use as the path, or may include information on the data to be the target of the path switching. The information on the data to be the target of the path switching may be, for example, information on the QoS flow or information on the PDU session. The UPF may use the instruction to switch the path used for downlink data transmission. This makes it possible to switch the transmission path only for data that requires the transmission path switching, and as a result, it is possible to prevent congestion in the transmission path to be switched to.

[0245] The UPF may transmit a response to the instruction to the AMF. The transmission of the response may be performed via the SMF. The AMF may transfer the response to the master base station. This makes it possible to prevent, for example, a discrepancy regarding an uplink data communication path between an upper network device and a master base station, and as a result, to prevent malfunctions in the communication system.

[0246] After the switchover instruction, the UPF may receive the uplink data from the base station before the switchover, or from the base station after the switchover. This makes it possible to prevent, for example, the loss of uplink data before and after the switchover of the uplink data transmission path in the UE.

[0247] The instruction from the master base station to the AMF may be signaling in the NG interface. The signaling for transmitting the instruction may be existing signaling or may be newly provided. The same may be applied to the transfer of the instruction from the AMF to the UPF. The same may be applied to the response of the instruction from the UPF to the AMF. The same may be applied to the transfer of the response from the AMF to the UE.

[0248] An active / deactive state may be provided for the PDU session. The activation and deactivation of the PDU session may be used in switching the communication path as described above. The UE and / or the UPF may transmit data using an active PDU session. The UE and / or the UPF may receive data in an active PDU session, and may also receive data in a deactive PDU session. This may provide, for example, the same effects as those described above.

[0249] In the above-mentioned multiple PDU sessions, it is preferable to set the latency between the UPF and the UE to be the same. This makes it possible to maintain a constant latency in data transmission and reception before and after switching the PDU session used for data transmission, for example.

[0250] In data transmission and reception between a UE and a UPF, a transmitting device may notify information regarding the transmission time of the transmission data, or may notify information regarding the time when the receiving device should receive the data. The transmitting device may be a UE or a UPF. The receiving device may be a UPF or a UE. The time when the data should be received may be, for example, the time when the receiving device should transfer the data to a higher layer. The time may be, for example, a time in milliseconds, a time using a subframe number, a time using a slot number, a time using a minislot number, a time using a symbol number, or a time combining a plurality of the above. The transmitting device may, for example, give a timestamp to the transmission data. The timestamp may be the same information as the above-mentioned time. The timestamp may be given in a higher layer, in an SDAP, in a PDCP, in an RLC, or in a MAC. As another example, the information on the transmission time may be notified using NAS signaling, RRC signaling, MAC signaling, or L1 / L2 signaling. The receiving device may derive the timing using the information on the transmission time. The receiving device may remove the timestamp in the received data. The above method may be applied to multiple PDU sessions between the UE and the UPF. This makes it possible, for example, to make the latency in data transmission and reception between the UE and the UPF the same for multiple PDU sessions.

[0251] The AMF may notify the UPF and / or the UE of information regarding the latency between the UPF and the UE. The information may be, for example, a latency required for communication between the UPF and the UE. The notification may be, for example, via signaling on the NG interface or via NAS signaling. The UPF and / or the UE may obtain the latency between the UPF and the UE using the information.

[0252] In data transmission and reception between the UE and the UPF, notification of information on the transmission time of the transmission data from the transmitting device and / or information on the time at which the receiving device should receive may be applied in periodic data transmission and reception. For example, the information on the time at which the receiving device should receive may be a combination of a period and an offset, i.e., one of the times at which the receiving device should receive. Information indicating that the data transmission and reception is periodic data transmission and reception may be included. The UE and / or the UPF may use the information to forward the received data to a higher layer. This makes it possible to maintain a constant latency even in periodic data transmission and reception, for example.

[0253] Figures 19 and 20 are sequence diagrams showing the operation of switching the PDU session used for data transmission and switching the base station to which the UE connects in the second embodiment. Figures 19 and 20 are connected at the position of the boundary line BL1920. Figures 19 and 20 show an example of transmission and reception of U-plane data between the UE and the UPF. In the example shown in Figures 19 and 20, the PDU session used for data transmission is switched from a PDU session passing through the source master base station (source MN) to a PDU session passing through a secondary base station, and the master base station to which the UE connects is switched from the source MN to the destination MN.

[0254] In steps ST2500 and ST2501 shown in Fig. 19, data is transmitted and received between the UE and the UPF via the source MN. Step ST2500 shows data transmission and reception between the UPF and the source MN, and step ST2501 shows data transmission and reception between the source MN and the UE.

[0255] 19, the source MN decides to switch the master base station from its own base station to the target MN. In Step ST2502, the source MN may decide not to switch the secondary base station.

[0256] In step ST2505 shown in FIG. 19, the source MN requests the AMF to switch the PDU session used for downlink U-plane data transmission between the UE and the UPF from the PDU session via its own base station to the PDU session via the source SN. In step ST2508, the AMF notifies the UPF of the request for switching, and the UPF notifies the AMF of the completion of the switching. The notification of the request and the notification of the completion may be performed via the SMF. The UPF uses the notification of the request to switch the PDU session used for downlink U-plane data transmission from the PDU session via the source MN to the PDU session via the source SN.

[0257] In steps ST2510 and ST2511 shown in FIG. 19, the UPF transmits downlink U-plane data to the UE via the source SN. Step ST2510 shows data transmission from the UPF to the source SN, and step ST2511 shows data transmission from the source SN to the UE. In steps ST2512 and ST2513, the UE transmits uplink U-plane data to the UPF via the source MN. Step ST2512 shows data transmission from the UE to the source MN, and step ST2513 shows data transmission from the source MN to the UPF.

[0258] 19, the AMF transmits to the source MN a positive response to the PDU session switching request of Step ST2505. The transmission of the positive response may be performed by using the switching completion notification notified to the AMF from the UPF in Step ST2508.

[0259] In step ST2515 shown in FIG. 19, the source MN instructs the UE to switch the PDU session used for transmitting uplink U-plane data between the UE and the UPF from the PDU session via its own base station to the PDU session via the source SN. The instruction may be included in, for example, the signaling of RRC reconfiguration. Using the instruction, the UE switches the PDU session used for transmitting uplink U-plane data from the PDU session via the source MN to the PDU session via the source SN.

[0260] In steps ST2520 and ST2521 shown in Fig. 19, data is transmitted and received between the UE and the UPF via the source SN. Step ST2520 shows data transmission and reception between the UPF and the source SN, and step ST2521 shows data transmission and reception between the source SN and the UE.

[0261] 19, the UE notifies the source MN of a response to the switch instruction in Step ST2515. The response may be notified using signaling of RRC reconfiguration complete (RRCReconfigurationComplete).

[0262] In Step ST2523 shown in FIG. 19, the source MN notifies the target MN of a handover request. This notification may include information indicating that the secondary base station is not to be switched. In Step ST2524, the target MN performs admission control for the handover.

[0263] In Step ST2525 shown in Fig. 20, the target MN makes a secondary node addition request to the source SN. In Step ST2526, the source SN notifies the target MN of a secondary node addition request acknowledgement.

[0264] In Step ST2527 shown in FIG. 20, the target MN sends an acknowledgement (Handover Request Acknowledge) to the source MN in response to the handover request in Step ST2523.

[0265] In Step ST2528 shown in FIG. 20, the source MN transmits a secondary node release request to the source SN. After the request is transmitted, data transmission and reception between the UE and the UPF via the source SN may be continued. The source MN may include, in the request, information indicating that data transmission and reception via the source SN will be continued.

[0266] Steps ST2530 and ST2531 shown in FIG. 20 are the same as steps ST2520 and ST2521, respectively.

[0267] In Step ST2533 shown in FIG. 20, the source SN notifies the source MN of an affirmative response to the secondary node release request (Secondary Node Release Request Acknowledge).

[0268] In Step ST2535 shown in FIG. 20, the source MN instructs the UE to perform a handover from its own base station to the target MN. The instruction may be included in, for example, signaling of RRC reconfiguration. The instruction may include information indicating that the secondary base station will not change. Using the instruction, the UE performs a handover from the source MN to the target MN without changing the secondary base station from the source SN. In Step ST2537, a random access process is performed between the UE and the target MN. In Step ST2538, the UE notifies the target MN of the completion of the handover. For the notification, for example, signaling of RRC reconfiguration complete may be used. In Step ST2539, the target MN notifies the source SN of secondary node reconfiguration complete.

[0269] Steps ST2540 and ST2541 shown in FIG. 20 are the same as steps ST2520 and ST2521, respectively.

[0270] In Step ST2542 shown in FIG. 20, the target MN notifies the AMF of a request to switch the path of the PDU session between the UE and the UPF via the source MN from the path via the source MN to the target MN. The notification of the request may be performed, for example, by using signaling of a PDU session path switch request. In Step ST2545, the AMF notifies the UPF of the request for switching, and the UPF notifies the AMF of the completion of the switching. The notification of the request and the notification of the completion may be performed via the SMF. The UPF uses the notification of the request to switch the path of the PDU session between the UE and the UPF via the source MN from the path via the source MN to the target MN.

[0271] In Step ST2547 shown in Fig. 20, the AMF transmits to the target MN a positive response to the PDU session path switching request in Step ST2542. The transmission of the positive response may be performed by using the switching completion notification notified to the AMF from the UPF in Step ST2545.

[0272] In Step ST2548 shown in Fig. 20, the target MN instructs the source MN to release the UE context. This instruction may be performed by using signaling of UE context release, for example.

[0273] Steps ST2550 and ST2551 shown in FIG. 20 are the same as steps ST2520 and ST2521, respectively.

[0274] In FIG. 19 and FIG. 20, an example has been disclosed in which the downlink data transmission PDU session switching shown in steps ST2505 to ST2514 is performed before the uplink data transmission PDU session switching shown in steps ST2515 to ST2522. In contrast, the downlink data transmission PDU session switching may be performed after the uplink data transmission PDU session switching. As another example, the uplink data transmission PDU session switching may be performed in the middle of the downlink data transmission PDU session switching. For example, step ST2515 may be performed between steps ST2505 to ST2514. As another example, the downlink data transmission PDU session switching may be performed in the middle of the uplink data transmission PDU session switching. For example, step ST2505 may be performed between steps ST2515 to ST2522. This makes it possible to improve the flexibility of the communication system, for example.

[0275] 19 and 20 show the switching of the path of transmission and reception of U-plane data, but the switching of the transmission and reception path may also be performed in the C-plane. In the switching of the transmission and reception path in the C-plane, the transmission and reception of C-plane data may be performed between the UE and the AMF. This makes it possible to prevent, for example, the fluctuation of latency associated with the switching of the base station even in the C-plane data.

[0276] FIG. 21 and FIG. 22 are sequence diagrams showing another example of the operation of switching the PDU session used for data transmission and switching the base station to which the UE is connected in the second embodiment. FIG. 21 and FIG. 22 are connected at the position of the boundary line BL2122. FIG. 21 and FIG. 22 show an example of transmission and reception of U-plane data between the UE and the UPF. In the example shown in FIG. 21 and FIG. 22, the PDU session used for data transmission is switched from a PDU session passing through the source secondary base station (source SN) to a PDU session passing through the destination master base station, and the secondary base station to which the UE is connected is switched from the source SN to the destination SN. Here, an example will be described in which the operation shown in FIG. 21 and FIG. 22 is performed following the operation shown in FIG. 19 and FIG. 20. In FIG. 21 and FIG. 22, the same step numbers are assigned to the same processes as those in FIG. 19 and FIG. 20, and common explanations will be omitted.

[0277] In steps ST2600 and ST2601 shown in Fig. 21, data is transmitted and received between the UE and the UPF via the source SN. Step ST2600 shows data transmission and reception between the UPF and the source SN, and Step ST2601 shows data transmission and reception between the source SN and the UE.

[0278] In Step ST2602 shown in FIG. 21, the target MN decides to switch the secondary base station from the source SN to the target SN.

[0279] In Step ST2605 shown in Fig. 21, the target MN requests the AMF to switch the PDU session used for downlink U-plane data transmission between the UE and the UPF from the PDU session via the source SN to the PDU session via its own base station. Step ST2508 is the same as in Fig. 19. Using the notification of the request, the UPF switches the PDU session used for downlink U-plane data transmission from the PDU session via the source SN to the PDU session via the target MN.

[0280] In steps ST2610 and ST2611 shown in FIG.21, the UPF transmits downlink U-plane data to the UE via the target MN. Step ST2610 shows data transmission from the UPF to the target MN, and step ST2611 shows data transmission from the target MN to the UE. In steps ST2612 and ST2613, the UE transmits uplink U-plane data to the UPF via the source SN. Step ST2613 shows data transmission from the UE to the source SN, and step ST2614 shows data transmission from the source SN to the UPF.

[0281] In Step ST2614 shown in Fig. 21, the AMF transmits to the target MN a positive response to the PDU session switching request in Step ST2605. The transmission of the positive response may be performed by using the switching completion notification notified to the AMF from the UPF in Step ST2508.

[0282] In step ST2615 shown in FIG. 21, the target MN instructs the UE to switch the PDU session used for transmitting uplink U-plane data between the UE and the UPF from the PDU session via the source SN to the PDU session via its own base station. The instruction may be included in, for example, the signaling of RRC reconfiguration. Using the instruction, the UE switches the PDU session used for transmitting uplink U-plane data from the PDU session via the source SN to the PDU session via the target MN.

[0283] In Steps ST2620 and ST2621 shown in Fig. 21, data is transmitted and received between the UE and the UPF via the target MN. Step ST2620 shows data transmission and reception between the UPF and the target MN, and Step ST2621 shows data transmission and reception between the target MN and the UE.

[0284] In Step ST2622 shown in Fig. 21, the UE notifies the target MN of a response to the switch instruction in Step ST2615. The response may be notified using signaling of RRC reconfiguration complete (RRCReconfigurationComplete).

[0285] In Step ST2625 shown in FIG. 22, the target MN makes a secondary node addition request to the target SN. In Step ST2626, the target SN notifies the target MN of a secondary node addition request acknowledgement.

[0286] In Step ST2628 shown in FIG. 22, the target MN makes a secondary node release request to the source SN. In Step ST2633, the source SN notifies the target MN of a secondary node release request acknowledgement to the secondary node release request.

[0287] In Step ST2635 shown in FIG. 22, the target MN instructs the UE to switch the secondary base station from the source SN to the target SN. This instruction may be included in signaling of RRC reconfiguration, for example. The UE may use this instruction to change the secondary base station from the source SN to the target SN. In Step ST2636, the UE notifies the target MN of the completion of the SN base station switch. For this notification, signaling of RRC reconfiguration complete, for example, may be used. In Step ST2638, the target MN notifies the target SN of secondary node reconfiguration complete. In Step ST2639, a random access process is performed between the UE and the target SN.

[0288] Steps ST2640 and ST2641 shown in FIG. 22 are the same as steps ST2620 and ST2621, respectively.

[0289] In Step ST2642 shown in FIG. 22, the target MN notifies the AMF of switching of a path from via the source SN to the target SN for a PDU session between the UE and the UPF via the source SN. The notification may be performed, for example, by using signaling of a PDU session resource modify indication. In Step ST2645, the AMF transfers the switch notification to the UPF, and the UPF notifies the AMF of the completion of the switch. The notification of the switch and the notification of the completion may be performed via the SMF. Using the notification of the switch, the UPF switches the path from via the source SN to the target SN for a PDU session between the UE and the UPF via the source SN.

[0290] In Step ST2647 shown in Fig. 22, the AMF transmits an acknowledgement to the target MN in response to the PDU session resource change notification in Step ST2642. The transmission of the acknowledgement may be performed by using the switching completion notification notified to the AMF from the UPF in Step ST2645.

[0291] In Step ST2648 shown in Fig. 22, the target MN instructs the source SN to release the UE context. This instruction may be performed by using signaling of UE context release, for example.

[0292] Steps ST2650 and ST2651 shown in FIG. 22 are the same as steps ST2620 and ST2621, respectively.

[0293] 21 and 22, similarly to Fig. 19 and Fig. 20, the downlink data transmission PDU session switching shown in steps ST2605 to ST2614 may be performed after or during the uplink data transmission PDU session switching shown in steps ST2615 to ST2622. Also, the uplink data transmission PDU session switching shown in steps ST2615 to ST2622 may be performed during the downlink data transmission PDU session switching shown in steps ST2605 to ST2614. This makes it possible to improve the flexibility of the communication system, for example.

[0294] In Fig. 21 and Fig. 22, similarly to Fig. 19 and Fig. 20, the transmission and reception path may be switched in the C plane. In the transmission and reception path switching in the C plane, the C plane data may be transmitted and received between the UE and the AMF, or the C plane data may be transmitted and received between the UE and the SMF. This makes it possible to prevent, for example, the fluctuation of latency accompanying the switching of the base station in the C plane data.

[0295] The operations shown in Figures 19 and 20 and the operations shown in Figures 21 and 22 may be performed alternately. This makes it possible to maintain a constant latency in data transmission and reception between the UE and the upper NW device, for example, even when the UE continues to move.

[0296] In a method in which a UE communicates using multiple PDU sessions, multiple UPFs may be used. For example, each of the different PDU sessions may pass through a different UPF. In a communication in which multiple UPFs are used, a device on a data network (DN) in non-patent document 30 (3GPP TS23.501 V15.3.0) may transmit and receive data to and from a UE using the multiple UPFs. A master base station may request an AMF to switch a downlink data transmission path. The AMF may transfer the request to the device on the DN. The transfer may be performed via an SMF. The device on the DN may use the transferred request to switch a PDU session used for downlink data transmission. The master base station may instruct the UE to switch a PDU session used for uplink data transmission. The instruction from the master base station to the UE may be the same as described above. As a result, for example, the same effect as described above can be obtained in a communication in which multiple UPFs are used.

[0297] Another solution is disclosed. Handover to a base station that does not satisfy the latency requirement is not performed. The source base station notifies the destination base station of the latency requirement. The destination base station uses the latency requirement to decide whether to accept or reject the handover.

[0298] Information on latency requirements may be included in the signaling of a handover request notified from the source base station to the destination base station. The information may be set for each QoS flow used by the UE or for each bearer used by the UE. The destination base station may use the information to decide whether to accept / reject the handover for each QoS flow and / or for each bearer. The destination base station may be notified of the QoS flows and / or bearers for which the handover is accepted.

[0299] In the 5G system, time synchronization may be performed. For example, time synchronization may be performed between an upper network device and a base station.

[0300] The upper NW device may notify the base station of the timestamp. The base station may notify the upper NW device of the timestamp. The upper NW device may derive a transmission delay from the device to the base station using the timestamp transmitted by the device itself and the timestamp transmitted by the base station to the device itself. The upper NW device may notify the base station of the transmission delay. The base station may correct the time of the base station itself using the transmission delay.

[0301] Time synchronization may be performed between the base stations. In the synchronization between the base stations, the above-mentioned method of time synchronization between the upper network device and the base station may be applied, or the method disclosed in the first modification of the first embodiment may be applied.

[0302] According to the second embodiment, it becomes possible to maintain a constant communication latency even when mobility occurs.

[0303] Embodiment 3 The base station may hold downlink data to be transmitted to the UE. The held downlink data (hereinafter, sometimes referred to as local cache data) may be transmitted from the UPF to the base station. The base station may transmit the local cache data to the UE.

[0304] However, when the UE undergoes handover between base stations, the destination base station does not hold the local cache data, which causes a problem of increased latency in receiving the data at the UE.

[0305] A solution to the aforementioned problems is disclosed.

[0306] The target base station also holds local cache data, which may be transmitted from the source base station.

[0307] The transmission of the local cache data from the source base station to the destination base station may be performed simultaneously with the transmission of a handover request from the source base station to the destination base station, or may be performed after the transmission of the handover request, which allows, for example, the destination base station to quickly obtain the local cache data.

[0308] As another example, the transmission of the local cache data from the source base station to the destination base station may be performed after, for example, a handover request acknowledgment from the destination base station to the source base station. This makes it unnecessary to transmit the local cache data to the selected destination base station again when, for example, the destination base station rejects the handover request. As a result, it is possible to improve the efficiency of the communication system.

[0309] As another example, the UPF may transmit local cache data to the destination base station. The destination base station may request the UPF to transmit the local cache data to the destination base station. This can reduce the load on the interface between base stations, for example.

[0310] The source base station may release the locally cached data, for example, after the source base station receives the handover request acknowledgement, which may reduce the memory usage in the source base station.

[0311] Another solution is disclosed. A plurality of base stations hold local cache data. The plurality of base stations may be, for example, base stations in the same RAN Notification Area (RNA) as the source base station, or may be base stations in the same tracking area as the source base station. As another example, the source base station may determine the base station that holds the local cache data, or the upper NW device may determine it. The source base station or the upper NW device may determine the base station that holds the local cache data by using, for example, location information of the UE. The plurality of base stations may hold the local cache data, for example, before the start of handover. This makes it possible to prevent congestion in the communication system during handover processing, for example.

[0312] The source base station may notify the destination base station of information indicating which data of the local cache data should be transmitted to the UE (or which data onward). A sequence number may be provided in the local cache data. The sequence number may be provided separately from the PDCP SN. The sequence number may be provided, for example, for each packet. The information may include the sequence number, may include the PDCP SN, or may include information combining the sequence number and the PDCP SN. This makes it possible to prevent duplication or loss of the locally cached data after handover, for example.

[0313] The UE may notify the base station of information on data that the UE wishes to start receiving in the local cache data. The information may include the sequence number, may include the PDCP SN, or may include information combining the sequence number and the PDCP SN. The notification from the UE to the base station may be performed, for example, when data communication to the UE is resumed, or may be used in fast forward and / or rewind in data communication from the base station to the UE, or may be performed at the time of handover of the UE. The resumption of data communication to the UE may be, for example, when the UE returns from RRC_INACTIVE to RRC_CONNECTED. The UE may hold the sequence number, may hold the PDCP SN, or may hold information combining the sequence number and the PDCP SN at the time of transition to RRC_INACTIVE. This may improve the flexibility of local cache data transmission from the base station to the UE, for example.

[0314] As another example of the sequence number of the locally cached data, the sequence number may be associated with the PDCP SN. For example, the sequence number may be obtained by adding or subtracting a predetermined offset to the PDCP SN. In the above, one PDCP PDU may be generated from one packet of the locally cached data. This can avoid complexity in the communication system, for example.

[0315] The source base station may notify the destination base station of the combination of information on the offset value and information on the PDCP SN for which the next PDCP PDU should be generated, which can reduce the size of signaling in inter-base station communications, for example.

[0316] The UE may notify the base station of only the PDCP SN of the data that the UE wishes to start receiving in the local cache data. The base station may derive a sequence number in the local cache data of the data that the UE wishes to start receiving, using information on the offset value and the PDCP SN. As another example, the UE may notify the base station of a sequence number of the local cache data of the data that the UE wishes to start receiving. The base station may derive a PDCP SN of the data that the UE wishes to start receiving in the local cache data, using the sequence number and information on the offset value. The above notification may be performed using a PDCP control PDU or may be performed using RRC signaling. This may, for example, reduce the amount of signaling between the UE and the base station.

[0317] As another example of the sequence number of the local cache data, a TCP sequence number may be used. The above-mentioned notification from the source base station to the destination base station may include the TCP sequence number. The source base station may hold information regarding a combination of the TCP sequence number in the local cache data and the PDCP SN. The above-mentioned notification from the UE to the base station may include the TCP sequence number. This, for example, makes it unnecessary to provide a new number in the communication system, and as a result, it is possible to avoid complexity in the communication system.

[0318] The local cache data in the third embodiment may be applied to uplink communication transmitted from a UE to a base station. The local cache may be used, for example, for user data transmitted from a UE to another UE via a base station. In addition, the local cache may be used to terminate a communication protocol (e.g., TCP) with the UE in the base station, for example, when the communication speed from the UE to a peer in the application layer of the UE is high (e.g., the communication distance is long, or there are many routing devices between the UE and the peer).

[0319] The local cache data in the uplink communication may be transferred from the source base station to the destination base station. The local cache data may be held in a plurality of base stations.

[0320] The source base station may notify the UE of information indicating which data of the local cache data (or data after) should be transmitted to the UE. A sequence number may be provided in the local cache data. The sequence number may be provided separately from the PDCP SN. The sequence number may be provided, for example, for each packet. The UE may use the information to determine data to start uplink transmission to the destination base station. This makes it possible to prevent, for example, duplicate transmission or missing data in uplink communication as well.

[0321] According to the third embodiment, even in a situation where a handover occurs, the UE can reduce the latency of downlink and / or uplink communication, and can ensure the reliability of the downlink and / or uplink communication.

[0322] Embodiment 4 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.

[0323] 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.

[0324] The physical sidelink discovery channel (PSDCH) carries sidelink discovery messages from the UE.

[0325] The physical sidelink control channel (PSCCH) carries control information from the UE for sidelink and V2X sidelink communications.

[0326] The physical sidelink shared channel (PSSCH) carries data from the UE for sidelink and V2X sidelink communications.

[0327] 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.

[0328] The Sidelink discovery channel (SL-DCH) has periodic broadcast transmissions of a fixed size and a predefined format. It 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. It also supports HARQ combining, but does not support HARQ feedback. The SL-DCH is mapped to the PSDCH, which is a physical channel.

[0329] The Sidelink Shared Channel (SL-SCH) supports broadcast transmission. It 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. It also supports HARQ combining, but does not support HARQ feedback. It also supports dynamic link adaptation by changing transmission power, modulation and coding. The SL-SCH is mapped to the PSSCH, which is a physical channel.

[0330] 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.

[0331] The Sidelink Traffic Channel (STCH) is a one-to-multiple sidelink traffic channel for transmitting user information from one UE to other UEs. 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 STCH. STCH is mapped to the transport channel SL-SCH.

[0332] 3GPP is also considering support for V2X communications in NR. The study of V2X communications in NR is proceeding based on the LTE and LTE-A systems, but the following changes and additions have been made from the LTE and LTE-A systems:

[0333] In LTE, SL communication was limited to broadcast. In NR, support for unicast and groupcast, in addition to broadcast, is being considered for SL communication (see Non-Patent Document 28 (3GPP RP-182111)).

[0334] For unicast and groupcast communications, support for HARQ feedback (Ack / Nack), CSI reporting, etc. is being considered.

[0335] Low latency is required for NR SL communication. In order to meet the requirement of low latency, the introduction of preemption has been proposed for NR SL communication (Non-Patent Document 22 (3GPP R1-1810593), Non-Patent Document 27 (R1-1810775)). 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 (Non-Patent Document 16 (TS38.300)).

[0336] In SL, a transmitting UE may transmit data for multiple services, and the receiving UE may be different for each service. In such a case, the UE that receives the resource of the communication to be preempted is different from the UE that receives the resource of the communication to be preempted. The transmitting UE needs to notify the receiving UE that it has been preempted and that it will preempt, respectively. The method of such notification has not yet been disclosed.

[0337] As described above, the specific method of preemption has not yet been disclosed in SL. Therefore, the problem arises that the requirement for low delay characteristics cannot be met because preemption cannot be implemented. In the fourth embodiment, a method for solving such a problem is disclosed.

[0338] In normal SL communication, the transmitting UE (transmitting UE) transmits scheduling information such as PSSCH resource allocation information and the UE (receiving UE) that is the communication target in SL control information (SCI) on the PSCCH. The transmitting UE also transmits the PSSCH according to the scheduling information. By receiving the PSCCH, the receiving UE recognizes that the data is intended for its own UE, receives the PSSCH according to the scheduling information, and acquires the data.

[0339] Preemption will be disclosed. The transmitting UE transmits information indicating preemption (PI: Preemption Indication) on the PSCCH. The transmitting UE may transmit the information indicating preemption by including it in the SCI on the PSCCH. The transmitting UE may transmit the resource allocation information of the communication to be preempted and the information indicating preemption on the PSCCH. The transmitting UE may transmit the resource allocation information of the communication to be preempted and the information indicating preemption on the SCI on the PSCCH. The transmitting UE may transmit the information on the PSCCH of the communication to be preempted. Scheduling information of the communication to be preempted may be used instead of the resource allocation information of the communication to be preempted described above. The transmitting UE may transmit the scheduling information of the communication to be preempted and the information indicating preemption on the PSCCH by including it in the SCI on the PSCCH.

[0340] In SL, all UEs performing SL communication can receive the PSCCH of the configured resource pool. Both the receiving UE in the preempting communication and the receiving UE in the preempted communication can receive the PSCCH. Therefore, the receiving UE in the preempting communication can receive resource allocation information, and the receiving UE in the preempted communication can receive information indicating preemption.

[0341] The SCI may be divided into two. For example, SCI1 and SCI2. Two different channels may be provided for transmitting each SCI. For example, PSCCH1 and PSCCH2. One PSCCH, for example PSCCH1, can be received by all UEs for which a resource pool is set, similar to the conventional PSCCH. The other PSCCH, for example PSCCH2, differs from the conventional PSCCH and can be received only by one UE or a group of UEs.

[0342] Information indicating preemption may be included in SCI1 of PSCCH1 that can be received by all UEs for which a resource pool is configured. Resource allocation information of the communication to be preempted and information indicating preemption may be included in SCI1 of PSCCH1 that can be received by all UEs for which a resource pool is configured. Other information may be included in SCI2. In this way, both the receiving UE in the communication to be preempted and the receiving UE in the communication to be preempted can receive SCI1 of PSCCH1.

[0343] The receiving UE of the communication to be preempted receives the PSCCH and determines whether the SCI includes a PI. If the PI is not included, the receiving UE determines that the communication is not preempted. If the PI is included, the receiving UE determines that the communication is preempted. If the receiving UE of the communication to be preempted determines that the communication is preempted, it does not receive the resources allocated in the PSCCH.

[0344] The PI may include allocation information of the preempted resources. In this case, when the receiving UE of the preempted communication determines that it is preempted, it does not receive the resources allocated by the resource allocation information included in the PI. In this way, the receiving UE of the preempted communication can prevent the receiving UE from receiving the PSSCH transmitted in the preempted resources and intended for other receiving UEs.

[0345] The receiving UE of the communication to be preempted receives the PSCCH and judges whether the SCI includes the identifier of its own UE as the target UE. If the identifier of its own UE is not included, the receiving UE judges that the data is not sent to its own UE and does not receive the PSSCH. If the identifier of its own UE is included, the receiving UE judges that the data is sent to its own UE and receives the PSSCH using the scheduling information included in the SCI. In this way, the receiving UE of the communication to be preempted can receive the PSSCH transmitted in the preempted resource.

[0346] The communication resource to be preempted may be a reserved resource or a resource to which data is actually allocated. The method disclosed above can be applied to the case where a reserved resource is preempted.

[0347] Five specific examples of information contained in PI are disclosed below. (1) Information indicating preemption. (2) Information about the resource to be preempted. (3) Information indicating the reception process when preempted. (4) Information regarding the receiving UE of the communication to be preempted. (5) A combination of (1) to (4).

[0348] Regarding the above (1), the information indicating preemption may be information indicating whether preemption has occurred or not, or may be information indicating that preemption has occurred.

[0349] Regarding the above (2), the information on the resources to be preempted may be resource allocation information. The resource information may be time-frequency information. For example, it may be a slot number, a slot number, a PRB number, a PRB number, etc. The time unit may be TTI, a slot, a minislot, a symbol, 1 / n symbol (n is a positive integer), a CBG (Code Block Group), etc. The frequency unit may be PRB, a subcarrier, etc.

[0350] The information of the preempted resource may be time information only. In this case, the frequency resource may be the same as the frequency resource that has already been allocated or reserved. In this way, the information of the preempted resource can be reduced.

[0351] The RS in the SL may be excluded from the resources to be preempted. For example, the DMRS may be excluded. For example, when preemption is performed on a symbol-by-symbol basis, the symbols excluding the DMRS may be included in the resources to be preempted. By using the DMRS, the receiving UE of the preempted communication can improve the possibility of demodulating the data mapped to the slot including the preempted resource.

[0352] Regarding the above (3), the reception process when preempted may be a process of not receiving only the preempted resource, or a process of not receiving a specific resource including the preempted resource. The specific resource may be, for example, a slot. Alternatively, the specific resource may be a plurality of consecutive slots. As another example, the reception process when preempted may be a process of not receiving all the preempted data for some resources. In this way, the reception process can be simplified. The reception process described here may be a data demodulation process.

[0353] Regarding the above (4), the information on the receiving UE of the communication to be preempted may be information for identifying the receiving UE. For example, the information may be an identifier of the UE. The receiving UE to be preempted can be explicitly indicated, and the occurrence of malfunction can be reduced.

[0354] The PSCCH including the PI may be the PSCCH of the slot / minislot in which resource allocation of the preempted resource is performed. In this way, when the PSCCH is transmitted on the preempted resource, the PI can be notified by the PSCCH. Alternatively, the PSCCH including the PI may be the PSCCH next to the slot in which resource allocation of the preempted resource is performed. In this way, even when the PSCCH is not transmitted on the preempted resource, the PI can be notified by the PSCCH.

[0355] The transmitting UE may transmit information about the receiving UE of the communication to be preempted on the PSCCH. The transmitting UE may transmit information about the receiving UE of the communication to be preempted on the PSCCH by including the information in the SCI together with the scheduling information including the resource allocation information of the communication to be preempted and the PI. The information about the receiving UE of the communication to be preempted may be information for identifying the receiving UE. The information may be, for example, an identifier of the UE.

[0356] When the information about the receiving UE of the communication to be preempted is transmitted on the PSCCH, the transmission of the PI may be omitted. The transmitting UE transmits the information about the receiving UE of the communication to be preempted and the scheduling information including the resource allocation information of the communication to be preempted in the SCI on the PSCCH.

[0357] The receiving UE of the communication to be preempted receives the PSSCH and can recognize that the data is for another UE from the information about the receiving UE of the communication to be preempted. The receiving UE of the communication to be preempted may not receive the resources indicated in the resource allocation information.

[0358] The receiving UE of the communication to be preempted receives the PSCCH, recognizes from the information about the receiving UE of the communication to be preempted that the scheduling information is intended for the UE itself, and receives the PSSCH in accordance with the scheduling information.

[0359] When performing preemption, the transmitting UE may not transmit to the receiving UE of the preempted communication only using the preempted resources. In this way, it is possible to minimize the data that is not transmitted to the receiving UE of the preempted communication. As another method, the transmitting UE may not transmit to the receiving UE of the preempted communication using a predetermined resource including the preempted resource. The predetermined resource may be, for example, one or more CBGs (Code Block Groups), or one or more slots. For example, when multiple slots are scheduled, the transmitting UE may not transmit to the receiving UE of the preempted communication using multiple slots including the preempted resources. In this way, it is possible to simplify the processing of the transmitting UE.

[0360] When the transmitting UE transmits data to a resource other than the preempted resource among resources scheduled for the receiving UE of the preempted communication, the transmitting UE may rate-match the transmission data to the resource other than the preempted resource and transmit the data. The transmitting UE can transmit data using the resource scheduled. Information on rate matching may be notified from the transmitting UE to the receiving UE. The information indicating the reception process in the case of the preemption may be included in the PI and notified from the transmitting UE to the receiving UE.

[0361] When performing preemption, the transmission process of the transmitting UE for the receiving UE of the communication to be preempted may be appropriately associated with the reception process of the receiving UE in the case of preemption. For example, when the transmitting UE does not transmit one slot including the preempted resource to the receiving UE of the communication to be preempted in preemption, the reception process of the receiving UE may be a process of not receiving one slot including the preempted resource. In this case, the transmitting UE may notify the receiving UE of the transmission process method of the transmitting UE for the receiving UE of the communication to be preempted, instead of the information indicating the reception process in the case of preemption described above.

[0362] This enables preemption in SL, which requires low latency. Therefore, preemption can be implemented in SL communication, which requires low latency, and the low latency required for communication can be satisfied.

[0363] Fig. 23 is a diagram showing an overview of preemption in SL communication. Fig. 23 shows a case where the transmitting UE of the communication to be preempted and the transmitting UE of the communication to be preempted are the same, and the receiving UE of the communication to be preempted and the receiving UE of the communication to be preempted are different. Assume that UE1 is the transmitting UE, UE2 is the receiving UE of the communication to be preempted, and UE3 is the receiving UE of the communication to be preempted. Assume that the communication from UE1 to UE3 is communication that requires lower latency characteristics.

[0364] Resource reservation is performed from UE1 to UE2. Here, it is assumed that resource reservation is performed periodically. The example in FIG. 23 shows that three slots of resources are periodically reserved. However, one slot may be reserved, or multiple slots may be reserved. In this way, when resource reservation from UE1 to UE2 has already been performed, transmission of an SL to UE3 is triggered in UE1. UE1 performs a transmission process and selects resources. Resource selection is performed within a selection window.

[0365] The shorter the resource selection window, the shorter the time until transmission and the lower the latency. However, when the resource selection window is shortened, the number of selectable resources decreases, and the possibility that the resources are already reserved increases. By making reserved resources preemptible, the number of selectable resources can be increased.

[0366] UE1 decides to preempt resources already reserved for UE2 for communication with UE3, which requires low latency characteristics. Here, UE1 preempts the second slot after transmission processing. UE1 transmits to UE3 using the preempted resources. UE1 may not transmit to UE2 using the preempted resources. Here, UE1 does not transmit to UE2 in the second slot.

[0367] In this way, UE1 preempts and transmits resources that have already been reserved for UE2 to UE3. In this way, it becomes possible to perform communication with UE3, which requires lower latency characteristics, with lower latency.

[0368] Fig. 24 is a diagram showing a first example of a preemption method in SL communication. Like Fig. 23, Fig. 24 shows three slots including resources to be preempted. PSCCH, PSSCH, GAP, and PSFCH are mapped to each slot. PSCCH and PSSCH are transmitted from the transmitting UE. GAP is a non-transmission period. PSFCH is a feedback channel, which includes HARQ feedback (Ack, Nack), CSI report, SRS, etc., and is transmitted from the receiving UE.

[0369] Fig. 24 shows a case where three slots of resources have already been reserved from UE1 to UE2, and the second slot is preempted. SL transmission to UE3 is triggered in UE1, and UE1 decides to preempt the resource of the second slot after transmission processing for communication to UE3. Since the first and third slots are used for transmission to UE2 as usual, PSCCH and PSSCH are transmitted from UE1 to UE2.

[0370] The SCI is mapped to the PSCCH. The SCI may include a slot configuration. For example, the SCI may include a configuration such as the number of symbols and symbol numbers to which the PSSCH, GAP, and PSFCH are mapped. In this way, the receiving UE can recognize the configuration of the slot transmitted from the transmitting UE.

[0371] UE1 preempts the second slot after the transmission process for UE3 for communication with UE3. In the second slot, resources for UE2 are preempted. In the second preempted slot, UE1 transmits PSCCH and PSSCH for UE3. The preempted slot may be configured to map GAP and PSFCH. UE1 transmits scheduling information such as resource allocation information for PSSCH and PI in the PSCCH of the preempted slot.

[0372] Scheduling information such as resource allocation information of the PSSCH may be included in the SCI, and the SCI and PI may be transmitted on the PSCCH. Scheduling information such as resource allocation information of the PSSCH and PI may be included in the SCI, and transmitted on the PSCCH. Also, information for identifying the UE 3 may be included in the SCI.

[0373] In SL communication, any receiving UE can receive the PSCCH in the resource pool. Therefore, both UE2 and UE3 can receive the PSCCH in the second slot. UE2 can determine whether the resources are preempted or not depending on whether the received PSCCH contains a PI. If a PI is not included, UE2 determines that the scheduling is for its own UE, and receives the PSSCH using the scheduling information. If a PI is included, UE2 determines that the resources are preempted, and does not receive the resources allocated by the PSCCH.

[0374] In this way, it is possible to prevent UE2 from erroneously receiving resources preempted by other UEs. UE3 receives the PSCCH in the second slot, recognizes that the PSSCH is addressed to itself, and can receive the PSSCH using the scheduling information included in the SCI.

[0375] This preemption method makes preemption possible in SL communications. It is possible to preempt resources that have already been allocated or reserved for communications that require low latency. This makes it possible to satisfy the requirement for low latency.

[0376] When UE1 performs preemption for UE3, it may not transmit only the preempted resources to UE2. In this way, it is possible to minimize the data that is not transmitted to UE2. As another method, UE1 may not transmit slots including preempted resources to UE2. Alternatively, when multiple slots are scheduled, UE1 may not transmit multiple slots including the preempted resources to UE2. In this way, it is possible to simplify the processing of UE1 and UE2.

[0377] For the transmission process from UE1 to UE2, a setting suitable for the reception process in the case of preemption, disclosed in the specific example of information included in the PI, may be used. These transmission processing methods and reception processing methods may be associated in advance. Which transmission processing method and which reception processing method are to be used may be statically determined by a standard or the like, or may be set by the gNB and notified to the UE of the SL communication. Alternatively, which transmission processing method and which reception processing method are to be used may be preconfigured in the UE in advance.

[0378] When preempting the first slot reserved or scheduled from UE1 to UE2, UE1 notifies UE3 of scheduling information in the PSCCH of the first slot. Also, UE1 notifies UE2 of a PI in the PSCCH of the first slot. Scheduling information for UE3 is mapped to the PSCCH of the first slot, but scheduling information for UE2 is not mapped. Therefore, UE2 cannot receive the scheduling information in the first slot. In such a case, the transmission process of UE1 may be a process of not transmitting to UE2 in the first slot, and the reception process of UE2 may be a process of not receiving in the first slot.

[0379] In this way, it is possible to prevent UE2 from erroneously receiving data for UE3 in the first slot. UE2 should receive the PSCCH in the second slot. If the PSSCH is scheduled in the second slot from UE1 to UE2, UE2 will be able to receive the scheduling information and can receive the PSSCH.

[0380] When preempting the first slot reserved or scheduled from UE1 to UE2, UE1 does not need to notify PI for UE2 in the PSCCH of the first slot. UE1 may notify only scheduling information for UE3 in the PSCCH of the first slot. When UE2 recognizes that the first slot is scheduled for UE3, UE2 may not receive the first slot. In this way, it is possible to prevent UE2 from erroneously receiving data for UE3 in the first slot.

[0381] Processing of data of resources preempted to UE2 is disclosed. UE1 may transmit data of resources preempted to UE2 on remaining resources. To transmit on remaining resources, UE1 may perform rate matching, so that preempted data can be transmitted early.

[0382] As another method, UE1 may transmit the data of the preempted resource to UE2 using the next reserved resource. The number of resource reselections may be set in the NR SL. After the transmission using the reserved resource is performed a predetermined number of times, resource selection is performed again and resource reservation is performed again. In this way, it is possible to avoid monopolizing resources by the own UE.

[0383] If the transmission through the reserved resource has not reached a predetermined number of reselections, UE1 transmits the data of the resource preempted for UE2 on the next reserved resource. If the transmission through the reserved resource has reached a predetermined number of reselections, UE1 reselects the resource to re-reserve the resource and transmits the data on the newly reserved resource.

[0384] When a newly reserved resource is used for data transmission of a preempted resource, the reselection count may not be counted. The reselection count may not be decremented. In this way, it is possible to avoid further increase in delay time in data transmission of the preempted resource.

[0385] UE1 may perform a new resource selection and reservation to transmit data of the preempted resources to UE2. The resource selection and reservation may be non-periodic or may be dynamic. A short-term resource reservation may be performed. This method may be applied even if the preempted resources are periodic. In this way, the preempted data can be transmitted early without waiting for the next reserved resource.

[0386] Alternatively, UE1 may not perform special processing for data of preempted resources for UE2. If HARQ feedback is applied, UE1 may not perform special processing for data of preempted resources for UE2. If HARQ feedback is applied, UE1 may follow HARQ. If UE2 cannot receive scheduled data, it transmits Nack to UE1. UE1 performs retransmission upon receiving Nack. In HARQ retransmission, UE1 may include information indicating which data is to be retransmitted in SCI. The information indicating which data is to be retransmitted may be, for example, a HARQ process identifier. In this way, UE2 can receive scheduled data.

[0387] Also, when repetition transmission is applied and HARQ feedback is applied, UE1 may not perform special processing for data of preempted resources for UE2. Even if one transmission of the repetition transmission is preempted, UE2 can receive the scheduled data by other repetition transmissions.

[0388] In this way, by not carrying out special processing for data in preempted resources, it is possible to simplify the preemption processing in the transmitting UE and the receiving UE.

[0389] Fig. 25 is a diagram showing a second example of a preemption method in SL communication. Unlike Fig. 24, Fig. 25 illustrates a preemption method in the case where three slots including resources to be preempted are scheduled consecutively. PSCCH, PSSCH, GAP, and PSFCH are mapped in three consecutive slots. PSCCH is mapped to the first slot of the three consecutive slots. GAP and PSFCH are mapped to the last slot of the three consecutive slots.

[0390] In the example of Fig. 24, the PSCCH in the second slot to be preempted includes scheduling information such as resource allocation information of the PSSCH and a PI. In the example of Fig. 25, since scheduling is performed from UE1 to UE2 using three consecutive slots, the PSCCH is not transmitted in the second slot. Therefore, UE2 does not receive the PSCCH in the second slot. Even if a PI is transmitted in the PSCCH in the second slot, UE2 does not receive the PI.

[0391] In order to solve such a problem, in the example of FIG. 25, UE1 transmits PI by including it in the PSCCH of the slot next to the slots scheduled consecutively. UE2 receives the PSCCH of the slot next to the slots scheduled consecutively. This allows UE2 to determine whether PI is included in the PSCCH. Therefore, UE2 can determine whether resources are preempted.

[0392] UE2 may hold the received data until it determines whether resources are preempted in consecutive scheduled slots. If resources are preempted, UE2 receives data excluding the preempted resources. If resources are not preempted, UE2 receives data from three consecutive slots. In this way, UE2 can avoid erroneous reception of preempted data.

[0393] The PSCCH in the second slot is transmitted from UE1 to UE3, and does not include a PI. UE3 obtains scheduling information of the PSSCH by receiving the PSCCH in the second slot, and becomes able to receive the PSSCH.

[0394] Although it has been disclosed that UE1 transmits the PI in the PSCCH of the slot next to the consecutively scheduled slot, another method will be disclosed. UE1 may transmit the PI in the PSCCH of the reserved or allocated slot next to the consecutively scheduled slot for UE2. UE2 receives the PSCCH of the reserved or allocated slot for its own UE following the consecutively scheduled slot. This allows UE2 to determine whether the PSCCH includes the PI. Therefore, UE2 can determine whether the resource is preempted.

[0395] When preempting the first slot reserved or scheduled from UE1 to UE2, UE1 notifies UE3 of scheduling information in the PSCCH of the first slot. UE1 may also notify UE2 of PI in the PSCCH of the first slot. Scheduling information for UE3 is mapped to the PSCCH of the first slot, and scheduling information for UE2 is not mapped. For this reason, UE2 cannot receive the scheduling information in the first slot. In such a case, the transmission process of UE1 may be a process of not transmitting to UE2 in three consecutive slots, and the reception process of UE2 may be a process of not receiving in three consecutive slots. In this way, it is possible to prevent UE2 from erroneously receiving data for UE3 in the first to third slots.

[0396] When preempting the first slot reserved or scheduled from UE1 to UE2, UE1 does not need to notify PI for UE2 in the PSCCH of the first slot. UE1 may notify only scheduling information for UE3 in the PSCCH of the first slot. When UE2 recognizes that the first slot is scheduled for UE3, it is preferable that UE2 not receive three consecutive slots. In this way, it is possible to prevent UE2 from erroneously receiving data for UE3 in the first to third slots.

[0397] By using such a preemption method, preemption is possible even if scheduling is performed over multiple consecutive slots in SL communication.

[0398] Fig. 26 is a diagram showing a third example of a preemption method in SL communication. Like Fig. 25, Fig. 26 shows an example of a preemption method in the case where three slots including a resource to be preempted are scheduled consecutively. Unlike Fig. 25, Fig. 26 shows a case where the resource to be preempted is a minislot.

[0399] When the resource to be preempted is a minislot, UE1 transmits the PI in the PSCCH of the next slot of the consecutively scheduled slots, similar to the method disclosed in Figure 26. UE2 receives the PSCCH of the next slot of the consecutively scheduled slots. This allows UE2 to determine whether the PSCCH contains the PI. Therefore, UE2 can determine whether the resource is preempted.

[0400] The PSCCH of the minislot to be preempted in the second slot is transmitted from UE1 to UE3, and does not include a PI. UE3 obtains scheduling information of the PSSCH by receiving the PSCCH of the minislot, and is able to receive the PSSCH.

[0401] When a resource including a PSCCH region of the first slot reserved or scheduled from UE1 to UE2 is preempted in a minislot, UE1 notifies UE3 of scheduling information in the PSCCH of the minislot. UE1 may also notify UE2 of a PI in the PSCCH of the minislot. Scheduling information for UE3 is mapped to the PSCCH of the minislot, and scheduling information for UE2 is not mapped. For this reason, UE2 cannot receive scheduling information of three consecutive slots. In such a case, the transmission process of UE1 may be a process of not transmitting to UE2 in three consecutive slots, and the reception process of UE2 may be a process of not receiving in three consecutive slots. In this way, it is possible to prevent UE2 from erroneously receiving data for UE3 in the first to third slots.

[0402] When a resource including the PSCCH area of ​​the first slot reserved or scheduled from UE1 to UE2 is preempted in a minislot, UE1 does not need to notify UE2 of a PI in the PSCCH of the minislot. UE1 may notify only scheduling information for UE3 in the PSCCH of the minislot. When UE2 recognizes that UE3 is scheduled in the resource of the minislot, UE2 may not receive three consecutive slots. In this way, it is possible to prevent UE2 from erroneously receiving data for UE3 in the first to third slots.

[0403] A receiving UE needs to receive the PSCCH of a minislot in SL communication. When data is scheduled in a minislot in SL communication, the receiving UE receives the PSCCH of that minislot. If the receiving UE does not know the transmission timing of the PSCCH of the minislot, it cannot receive the PSCCH. This causes a problem that the receiving UE cannot receive the PSCCH of the minislot. Here, a method for solving such a problem is disclosed.

[0404] A method for setting minislots in SL is disclosed. The setting of minislots in SL is performed by a transmitting UE. The transmitting UE sets minislots in SL and notifies the receiving UE of the setting. The notification may be performed using the PSCCH of a normal slot. Information for setting minislots may include, for example, the number of symbols in a minislot, the number of symbols and / or symbol numbers of PSCCH, the number of symbols and / or symbol numbers of PSSCH, the number of symbols and / or symbol numbers of RS, etc. The number of symbols and / or symbol numbers of GAP and PSFCH may be included in the information for setting minislots.

[0405] Information indicating the relationship with a normal slot may be included in the information for setting a minislot. The information indicating the relationship with a normal slot may be, for example, information indicating which symbols the minislot is located in from which symbols in a normal slot. The target minislot may be set by the symbol number of the normal slot. The same applies to the minislots PSCCH, PSSCH, GAP, and PSFCH. In this way, it is possible to set the minislot.

[0406] Another method is disclosed in which a transmitting UE notifies a receiving UE of minislot configuration. Information for minislot configuration may be notified using MAC signaling. Information for minislot configuration may be included in MAC control information. Information for minislot configuration may be notified by PC5 signaling. Alternatively, when an RRC connection is established between opposing UEs in SL unicast communication, information for minislot configuration may be notified using SL RRC signaling. Information for minislot configuration may be included in SL RRC information.

[0407] Another method for a transmitting UE to notify a receiving UE of a minislot setting is disclosed. The transmitting UE notifies the receiving UE of the minislot setting by PSBCH. The transmitting UE includes the minislot setting in broadcast information, maps it to PSBCH, and notifies it. In this way, when a minislot is set for each transmitting UE, it is not necessary to notify the receiving UE of the minislot setting individually. It is possible to reduce the amount of signaling in SL communication.

[0408] Information indicating activation and / or deactivation of minislot configuration may be provided. Hereinafter, this information is referred to as act / deact information of minislot configuration. The transmitting UE notifies the receiving UE of the act / deact information of minislot configuration. To notify this information, a method for notifying information for minislot configuration may be applied.

[0409] For example, the transmitting UE notifies the receiving UE of information for setting minislots. Thereafter, the transmitting UE notifies act information of the minislot settings. An identifier may be provided for each minislot setting, and the identifier may be notified together with the act / deact information of the minislot setting. In this way, even when multiple minislot settings exist, it becomes possible to recognize which minislot setting should be activated.

[0410] Upon receiving the act information for the minislot setting, the receiving UE applies the minislot setting. The transmitting UE transmits in the minislot, and the receiving UE receives in the minislot. The transmitting UE notifies the receiving UE of the deact information for the minislot setting. Upon receiving the deact information for the minislot setting, the receiving UE cancels the minislot setting. The receiving UE may receive in a normal slot. In this way, it is possible to end the minislot setting in SL.

[0411] In this way, minislots can be set in SL, and transmission and reception using minislots becomes possible.

[0412] Another method for setting minislots in SL is disclosed. The gNB sets minislots in SL. The gNB sets minislots in SL and notifies the transmitting UE of the setting. The transmitting UE notifies the receiving UE of the setting of the received minislots in SL. The Uu interface between the gNB and UE is used for the notification. The gNB may include information for setting minislots in SL in DCI and notify the transmitting UE of SL communication by PDCCH. Dynamic setting is possible. Alternatively, the gNB may notify the transmitting UE of SL communication of minislot setting information in SL by MAC signaling. Alternatively, the gNB may notify the transmitting UE of SL communication of minislot setting information in SL by RRC signaling. Reception errors can be reduced.

[0413] The information for minislot setting may be the same as that described above. The method for notifying the receiving UE of the minislot setting from the transmitting UE in the SL communication may be the same as that described above.

[0414] The act / deact of the minislot setting may be set by the transmitting UE of SL communication. The transmitting UE of SL communication sets the act / deact of the minislot setting and notifies the receiving UE. This method may be applied to the method described above. By the transmitting UE setting the act / deact of the minislot setting, it becomes possible to set the minislot according to the service of the data to be transmitted in SL. This makes it possible to shorten the setting time until the act / deact of the minislot setting.

[0415] Other methods of act / deact for minislot setting are disclosed. The act / deact for minislot setting may be set by the gNB. The gNB sets act / deact for minislot setting and notifies the transmitting UE of SL communication. The transmitting UE that receives act / deact information for minislot setting may notify the receiving UE of the information. The notification method of the information for minislot setting described above may be applied to these notification methods. By the gNB setting act / deact for minislot setting, it becomes possible to take into consideration the settings for other UEs performing SL communication. It becomes possible to reduce conflicts of resources for minislot setting.

[0416] By using such a preemption method, preemption of minislots is possible in SL communication.

[0417] Fig. 27 is a diagram showing a fourth example of a preemption method in SL communication. As in Fig. 25, Fig. 27 illustrates a preemption method in the case where three slots including a resource to be preempted are scheduled consecutively. In the example of Fig. 27, UE3 is set to receive the PSCCH region of every slot even when three consecutive slots are scheduled. This may be statically determined by a standard or the like.

[0418] Alternatively, the gNB may notify the UE performing SL communication of information indicating that the PSCCH region of each slot is to be received. The gNB may include the information in the SIB and notify the UE, or may notify the UE by RRC signaling. Alternatively, the information may be preset in the UE.

[0419] Another method is shown. Information indicating that the PSCCH region of every slot is received, or information indicating whether or not the PSCCH region of every slot is received, may be included in the PSCCH of the first slot. The information may be included in the PSCCH that includes the scheduling information when scheduling is performed in a plurality of consecutive slots. In this way, UE2 can receive information indicating that the PSCCH region of every slot is received by receiving the scheduling of a plurality of consecutive slots from UE1. For example, when UE1 prints the resource of the second slot to UE3, UE1 transmits information indicating that the PSCCH region of every slot is received to UE2. In this way, UE2 can receive the PSCCH of the second slot.

[0420] Also, UE1 transmits a PI for UE2 in the PSCCH of the second slot. As in the example of Fig. 24, UE1 transmits an SCI including scheduling information such as resource allocation information of the PSSCH for UE3 and a PI for UE2 in the PSCCH of the second slot. In this way, UE2 can receive the PI.

[0421] When preempting the first slot reserved or scheduled from UE1 to UE2, UE1 notifies UE3 of scheduling information in the PSCCH of the first slot. Also, UE1 notifies UE2 of a PI in the PSCCH of the first slot. Scheduling information for UE3 is mapped to the PSCCH of the first slot, but scheduling information for UE2 is not mapped. Therefore, UE2 cannot receive the scheduling information in the first slot. In such a case, the transmission process of UE1 may be a process of not transmitting to UE2 in the first slot, and the reception process of UE2 may be a process of not receiving in the first slot.

[0422] In this way, it is possible to prevent UE2 from erroneously receiving data for UE3 in the first slot. When the UE receives the PSCCH area of ​​every slot, for example, when it is statically determined by a standard or the like to receive the PSCCH area of ​​every slot, or when it is notified by a gNB, UE2 may receive the PSCCH of the second slot. When the PSSCH is scheduled from UE1 to UE2 in the second slot, the scheduling information can be received, and the PSSCH can be received.

[0423] When preempting the first slot reserved or scheduled from UE1 to UE2, UE1 does not need to notify PI for UE2 in the PSCCH of the first slot. UE1 may notify only scheduling information for UE3 in the PSCCH of the first slot. When UE2 recognizes that the first slot is scheduled for UE3, UE2 may not receive the first slot. In this way, it is possible to prevent UE2 from erroneously receiving data for UE3 in the first slot.

[0424] The PI may include information indicating that the PSCCH region of each slot is to be received. UE1 notifies UE2 of the PI in the PSCCH of the first slot. As a result, when the PSSCH is scheduled from UE1 to UE2 in the second slot, the scheduling information can be received, and the PSSCH can be received.

[0425] By using the method disclosed in FIG. 27, unlike the method disclosed in FIG. 25 or FIG. 26, UE1 does not need to transmit a PI for UE2 in the next slot of the multiple slots scheduled consecutively. Therefore, UE2 can determine whether a resource has been preempted or not earlier by receiving a PI earlier. UE2 can demodulate data earlier by excluding the preempted resource. In addition, UE2 does not need to hold data until receiving a PI included in the next slot. This can reduce the data buffer capacity in UE2.

[0426] Another example of a preemption method in SL communication is disclosed. A resource for PI transmission is provided. The resource for PI transmission may be provided within the reserved resource or the allocated resource of the communication to be preempted, but outside the resource to be preempted. The resource for PI transmission may be a time-frequency resource. The time unit of the resource may be, for example, a slot, a minislot, a symbol, or 1 / n symbol. The frequency unit of the resource may be, for example, a PRB or a subcarrier.

[0427] The configuration of the resource for PI transmission may be, for example, a slot number, a number of symbols, a symbol number, a number of PRBs, a PRB number, etc. The resource configuration for PI transmission may be statically determined in advance by a standard or the like. Alternatively, the gNB may determine the resource configuration for PI transmission and notify the determined resource configuration to a UE performing SL communication by SIB. Alternatively, the gNB may determine the resource configuration for PI transmission and notify the determined resource configuration to a transmitting UE for SL communication by RRC signaling. The transmitting UE may notify the receiving UE of the resource configuration for PI transmission by PSCCH.

[0428] Alternatively, the transmitting UE in the SL communication may determine the resource configuration for PI transmission and notify the receiving UE of the determined configuration. The transmitting UE may notify the receiving UE of the resource configuration for PI transmission by the PSCCH. When the transmitting UE and / or the receiving UE in the SL communication receive the resource configuration for PI transmission, the transmitting UE and / or the receiving UE can transmit and receive PI using the resource configuration for PI transmission.

[0429] The transmitting UE transmits the PI using the resource for PI transmission. A channel including the PI may be provided and mapped to the resource for PI transmission. The PI may be included in the PSCCH and mapped to the resource for PI transmission. When the receiving UE is notified of the resource configuration for PI transmission, the receiving UE may receive the resource for PI transmission.

[0430] Alternatively, information indicating activation and / or deactivation of PI transmission resource reception may be provided. The transmitting UE transmits act / deact information of PI transmission resource reception to the receiving UE on the PSCCH. When the receiving UE receives the act information of PI transmission resource reception, the receiving UE receives PI transmission resources using the PI transmission resource configuration. When the receiving UE receives the deact information of PI transmission resource reception, the receiving UE ends reception of PI transmission resources using the PI transmission resource configuration.

[0431] A specific example will be disclosed. When scheduling is performed using multiple consecutive slots, the transmitting UE uses the symbol immediately before the GAP of the last slot as a resource for PI transmission. The transmitting UE transmits the PI using that symbol. The transmitting UE may transmit the resource configuration for PI transmission to the receiving UE using the PSCCH of the first slot. In this way, the receiving UE can receive the resource configuration for PI transmission and can receive the PI using that configuration.

[0432] By using such a method, even when a resource scheduled in a plurality of consecutive slots is to be preempted, the PI can be transmitted in the plurality of consecutive slots. Therefore, unlike the examples of Figs. 25 and 26, the transmitting UE does not need to transmit the PI in the PSCCH of the slot next to the consecutive slots. Furthermore, the receiving UE only needs to receive the configured resource for transmitting the PI in order to receive the PI. Therefore, unlike the method shown in Fig. 27, the receiving UE does not need to receive the PSCCH of every slot. Furthermore, the receiving UE only needs to receive the reserved resource or the allocated resource of the communication to be preempted in order to receive the PI. This makes it possible to simplify the processing in the receiving UE.

[0433] In the above method, a resource for PI transmission is provided. The transmitting UE transmits a PI in the resource for PI transmission. At this time, the transmitting UE does not transmit data. Here, another example of a preemption method in SL communication is disclosed.

[0434] The transmitting UE multiplexes the PI or a channel including the PI with data in the resource for PI transmission and transmits the multiplexed data. The transmitting UE may multiplex the PSCCH including the PI with data in the resource for PSCCH. As a multiplexing method, code multiplexing may be used. As a code multiplexing method, for example, a method of multiplying the channel including the PI by a predetermined scrambling code may be used. Alternatively, a predetermined ZC (Zadoff-Chu) sequence may be used for the channel including the PI.

[0435] The predetermined scrambling code or the predetermined ZC sequence may be statically determined in advance by a standard or the like, or may be notified from the transmitting UE to the receiving UE. In this way, the receiving UE can separate and demodulate the PI from the data, and can receive the PI.

[0436] The data or the RS for data demodulation and the channel including the PI may be multiplied by different scrambling codes. Alternatively, different ZC sequences may be used for the data or the RS for data demodulation and the channel including the PI. These scrambling codes or ZC sequences may be statically determined in advance by a standard or the like. Alternatively, the gNB may determine the scrambling code or ZC sequence and notify the determined scrambling code or ZC sequence to the UE performing SL communication. Alternatively, the transmitting UE may determine the scrambling code or ZC sequence and notify the determined scrambling code or ZC sequence to the receiving UE. In this way, the receiving UE becomes able to demodulate the data and the PI separately, and is able to receive the data and the PI.

[0437] Another example of a preemption method in SL communication is disclosed. A resource for PI transmission is provided outside the reserved resource or allocated resource of the communication to be preempted. The resource configuration for PI transmission may be periodic. The resource configuration for PI transmission, the notification method for the resource configuration for PI transmission, and the PI transmission and reception method in the transmitting UE and the receiving UE may be the same as the above example, that is, the example disclosed in the case where the resource for PI transmission is provided within the reserved resource or allocated resource of the communication to be preempted and outside the preempted resource.

[0438] A transmitting UE performing SL communication may exclude resources for PI transmission and select resources for SL communication for resource reservation, thereby making it possible to avoid collision between resources for SL communication and resources for PI transmission.

[0439] In this way, it is possible to increase the number of candidates for resources for PI transmission, and it is also possible to perform PI transmission without reducing resources for communications to be preempted.

[0440] The resource for transmitting the PI may be provided inside or outside the reserved or allocated resource of the communication to be preempted. The method disclosed above may be applied.

[0441] In the example of the above figure, a case where resource reservation from UE1 to UE2 is performed periodically is disclosed. The method disclosed in the present embodiment 4 may not be applied to a case where resource reservation or scheduling from UE1 to UE2 is performed periodically, for example, may be applied to a case where resource reservation or scheduling from UE1 to UE2 is performed non-periodically. The method disclosed in the present embodiment 4 may be applied to a case where resource reservation or scheduling from UE1 to UE2 is performed dynamically. It is possible to obtain the same effect.

[0442] The transmitting UE may determine whether preemption is possible. The transmitting UE determines whether resources reserved or scheduled for communication of a certain service can be preempted for communication of another service. Information about the service may be used for the determination. The information about the service may be, for example, QoS information, QCI, PPPP, a required delay time, a required slew rate, etc.

[0443] For example, if a service of data to be transmitted later requires a shorter delay time than a service that has already been reserved or scheduled, preemption is possible.

[0444] Here is a specific example. The transmitting UE reserves resources for communication of a service with a required latency of L1. In this state, it is assumed that the transmitting UE generates transmission data for a service with a required latency of L2. Here, it is assumed that the required latency L2 is shorter than the required latency L1 (L1>L2). In this way, if the required latency of the service that occurs later is shorter, preemption is possible. The transmitting UE compares the required latency of these services, and if the required latency of the service that occurs later is shorter, it determines that preemption is possible.

[0445] These determinations may be made in the SL MAC. The SL MAC may determine whether preemption is possible using information about the service. The SL MAC may obtain information about the service from a higher layer. By determining whether preemption is possible in the SL MAC, it is possible to facilitate coordination of scheduling for the communication to be preempted and scheduling for the communication to be preempted.

[0446] The method disclosed in the fourth embodiment enables preemption in SL. Therefore, in a situation where a transmitting UE transmits data for a plurality of services, even if the receiving UE is different for each service, preemption can be performed in SL communication for a service that requires low latency. This makes it possible to satisfy the low latency required for communication.

[0447] Variation 1 of embodiment 4 In the fourth embodiment, a preemption method is disclosed in a case where a transmitting UE of a communication to be preempted and a transmitting UE of a communication to preempt are the same. In the present first modification, a preemption method is disclosed in a case where a transmitting UE of a communication to be preempted and a transmitting UE of a communication to preempt are different.

[0448] When the transmitting UE of the communication to be preempted and the transmitting UE of the communication to be preempted are different, not only how to notify the receiving UE of the communication to be preempted that preemption has been performed, but also how to notify the transmitting UE of the communication to be preempted that preemption has been performed becomes an issue. If the transmitting UE of the communication to be preempted does not recognize that preemption has been performed, the transmitting UE will transmit data using the preempted resource, resulting in a collision with the communication to be preempted. Due to this collision, neither the receiving UE of the communication to be preempted nor the receiving UE of the communication to be preempted will be able to receive data. In this first modification, a method for solving such a problem is disclosed.

[0449] The transmitting UE of the preempting communication transmits PI2 using a resource that is receivable by the preempted transmitting UE in a slot before the preempting resource. The transmitting UE of the preempting communication may map a channel including PI2 to a resource that is receivable by the preempted transmitting UE in a slot before the preempting resource and transmit PI2. The transmitting UE of the preempting communication may transmit PI2 on a PSFCH in a slot before the preempting resource.

[0450] PI2 is information indicating preemption. Five specific examples of information included in PI2 are disclosed below. (1) Information indicating preemption. (2) Information about the resource to be preempted. (3) Information indicating the transmission process in the case of preemption. (4) Information regarding the transmitting UE of the communication to be preempted. (5) A combination of (1) to (4).

[0451] The above (1) and (2) are the same as PI.

[0452] Regarding the above (3), the transmission process when preempted may be a process of not transmitting only the preempted resources, or a process of not transmitting a specific resource including the preempted resources. The specific resource may be, for example, a slot. Alternatively, the specific resource may be a plurality of consecutive slots. As another example, the transmission process when preempted may be a process of not transmitting any data for which some resources are preempted. In this way, the transmission process can be simplified. The transmission process may also be a process of stopping transmission, or a process of turning off or reducing transmission power.

[0453] Regarding the above (4), the information on the transmitting UE of the communication to be preempted may be information for identifying the transmitting UE. For example, the information may be a UE identifier. The transmitting UE to be preempted can be explicitly indicated, and the occurrence of malfunction can be reduced.

[0454] In this way, the transmitting UE of the preempted communication can receive PI2 from the transmitting UE of the preempting communication in the receiving symbol of the slot before the preempted resource. By receiving PI2, the transmitting UE of the preempted communication can recognize the preempted resource. This makes it possible to perform a process to stop transmission in the preempted resource.

[0455] The method of transmitting scheduling information including resource allocation from the transmitting UE of the communication to be preempted to the receiving UE of the communication to be preempted, and the method of transmitting a PI from the transmitting UE of the communication to be preempted to the receiving UE of the communication to be preempted may be the same as those disclosed in embodiment 4.

[0456] In this way, preemption becomes possible when the transmitting UE of the communication to be preempted is different from the transmitting UE of the communication to be preempted.

[0457] Fig. 28 is a diagram showing an overview of preemption in SL communication. Fig. 28 shows a case where a transmitting UE of a communication to be preempted is different from a transmitting UE of a communication to be preempted. Assume that UE1 is a transmitting UE of a communication to be preempted, UE2 is a receiving UE of a communication to be preempted, UE3 is a transmitting UE of a communication to be preempted, and UE4 is a receiving UE of a communication to be preempted. Assume that communication from UE3 to UE4 is communication that requires lower latency characteristics.

[0458] A resource reservation is made from UE1 to UE2. Here, it is assumed that the resource reservation is made periodically, as in FIG. 23. In this manner, with the resource reservation from UE1 to UE2 already made, the transmission of an SL to UE4 is triggered in UE3. UE3 performs a transmission process and selects a resource. The resource selection is made within a selection window.

[0459] UE3 decides to preempt resources already reserved by UE1 for UE2 for communication with UE4, which requires low latency characteristics. Here, UE3 preempts the second slot after transmission processing. UE3 transmits to UE4 using the preempted resources. UE1 may not transmit to UE2 using the preempted resources. Here, UE1 does not transmit to UE2 in the second slot.

[0460] In this way, UE3 preempts and transmits to UE4 the resources that UE1 has already reserved for UE2. In this way, it becomes possible to perform communication with UE4, which requires low latency characteristics, with low latency.

[0461] Fig. 29 is a diagram showing a first example of a preemption method in SL communication. Fig. 29 shows three slots including resources to be preempted, similar to Fig. 28. PSCCH, PSSCH, GAP, and PSFCH are mapped to each slot.

[0462] Fig. 29 shows a case where three slots of resources have already been reserved from UE1 to UE2, and the second slot is preempted. SL transmission to UE4 is triggered in UE3, and UE3 decides to preempt the resource of the second slot after transmission processing for communication to UE4. Since the first and third slots are for normal transmission from UE1 to UE2, UE1 transmits PSCCH and PSSCH to UE2.

[0463] UE3 transmits PI2 in a symbol that UE1 can receive in the slot (i.e., the first slot) immediately before the second slot to be preempted. Here, UE3 transmits PI2 in a PSFCH in a symbol that UE1 can receive.

[0464] In this way, UE1 can receive PI2 before the second slot to be preempted. Having received PI2, UE1 can recognize the preempted resources. Therefore, UE1 can, for example, stop transmission in the preempted resources. Here, UE1 stops transmission in the second preempted slot. In this way, UE1 can avoid interfering with the communication from UE3 to UE4 in the second preempted slot.

[0465] UE3 preempts the second slot after the transmission process for UE4 for communication with UE4. In the second slot, resources for UE2 are preempted. In the second preempted slot, UE3 transmits PSCCH and PSSCH for UE4. The preempted slot may be configured to map GAP and PSFCH. UE3 transmits scheduling information such as resource allocation information of PSSCH for UE4 and PI for UE2 in the PSCCH of the preempted slot. Since UE2 can also receive PSCCH, UE2 can receive PI included in PSCCH transmitted from UE3.

[0466] In this way, it is possible to prevent UE2 from erroneously receiving resources preempted by other UEs. UE4 receives the PSCCH in the second slot, recognizes that the PSSCH is addressed to itself, and can receive the PSSCH using the scheduling information included in the SCI.

[0467] The transmitting UE of the preempting communication may multiplex PI2 or a channel including PI2 with the PSFCH and transmit the multiplexed signal in resources that the transmitting UE to be preempted can receive.

[0468] A method of multiplexing PI2 and PSFCH is disclosed. Time division multiplexing is preferably used. Multiplexing is preferably performed using symbols that UE1 can receive. Among the symbols that UE1 can receive, the symbols to which PI2 is mapped and the symbols to which PSFCH is mapped are made different. In this way, UE1 can receive PI2 and PSFCH.

[0469] The slot format setting may be changed depending on whether or not PI2 is present. For example, when PI2 is present, the number of symbols for reception in the slot is set to 2, and when PI2 is not present, the number of symbols for reception in the slot is set to 1. By doing this, when PI2 is not present, there is no need to reserve a symbol for PI2, and the symbol can be used for other purposes (for example, for transmission). This makes it possible to improve the efficiency of resource usage.

[0470] Another method of multiplexing PI2 and PSFCH is disclosed. Frequency division multiplexing may be used. Multiplexing may be performed using a frequency domain of symbols that UE1 can receive. In symbols that UE1 can receive, the frequency domain (e.g., PRB) to which PI2 is mapped is different from the frequency domain (e.g., PRB) to which PSFCH is mapped. In this way, UE1 can receive PI2 and PSFCH.

[0471] Other methods of multiplexing PI2 and PSFCH are disclosed. It is preferable to use code division multiplexing. It is preferable to multiplex using a scrambling code or a ZC sequence in symbols that UE1 can receive. In symbols that UE1 can receive, the scrambling code multiplied by PI2 is made different from the scrambling code multiplied by PSFCH. In this way, UE1 can receive PI2 and PSFCH. Multiplexing may also be performed using CS (Cyclic Shift) of the ZC sequence. Similar effects can be obtained.

[0472] PI2 may be included in the PSFCH. For example, HARQ feedback information and PI2 information may be included in the PSFCH. For example, SL feedback control information (SFCI (Sidelink Feedback Control Information)) is provided, and the information is mapped to the PSFCH. HARQ feedback information and PI2 information may be included in the SFCI.

[0473] PI2 may be included in the PSFCH, and the PSFCH may be multiplexed with the PSFCH from another UE. The multiplexing method may be the above-mentioned method. In this way, UE1 can receive PI2 and the PSFCH.

[0474] By using such a preemption method, preemption is possible in SL communication even if the transmitting UE of the communication to be preempted is different from the transmitting UE of the communication to be preempted. It is possible to preempt resources that have already been allocated or reserved for communication that requires low latency characteristics. This makes it possible to satisfy the requirement for low latency characteristics.

[0475] The method disclosed in the fourth embodiment may be applied as appropriate to the transmission process of the preempted resources in UE1 and the reception process of the preempted resources in UE2. For example, the method disclosed in the example of FIG. 24 may be applied as appropriate. Similar effects can be obtained. Also, the method disclosed in the fourth embodiment may be applied as appropriate to the processing of data of the preempted resources for UE2. For example, the method disclosed in the example of FIG. 24 may be applied as appropriate. Similar effects can be obtained.

[0476] Regarding the process of preempting the first slot reserved or scheduled from UE1 to UE2, the method disclosed in the fourth embodiment may be applied as appropriate. For example, the method disclosed in the example of Fig. 24 may be applied as appropriate. Similar effects may be obtained.

[0477] Fig. 30 is a diagram showing a second example of a preemption method in SL communication. Unlike Fig. 29, Fig. 30 illustrates a preemption method in the case where three slots including resources to be preempted are scheduled consecutively. PSCCH, PSSCH, GAP, and PSFCH are mapped in three consecutive slots. PSCCH is mapped to the first slot of the three consecutive slots.

[0478] Conventionally, the GAP and PSFCH are mapped to the last slot of three consecutive slots. In this first modification, a symbol for reception is mapped to each slot. Here, the PSFCH is mapped to the symbol for reception.

[0479] UE3 transmits PI2 in a symbol that UE1 can receive in the slot (i.e., the first slot) immediately before the second slot to be preempted. Here, UE3 transmits PI2 in a PSFCH in a symbol that UE1 can receive.

[0480] In this way, UE1 can receive PI2 before the second slot to be preempted. Having received PI2, UE1 can recognize the preempted resources. Therefore, UE1 can, for example, stop transmission in the preempted resources. Here, UE1 stops transmission in the second preempted slot. In this way, UE1 can avoid interfering with the communication from UE3 to UE4 in the second preempted slot.

[0481] In the example of Fig. 29, the PSCCH in the second slot to be preempted includes scheduling information such as resource allocation information of the PSSCH from UE3 to UE4, and a PI from UE3 to UE2. In the example of Fig. 30, since scheduling is performed from UE1 to UE2 using three consecutive slots, the PSCCH is not transmitted in the second slot. Therefore, UE2 does not receive the PSCCH in the second slot. Even if a PI is transmitted in the PSCCH in the second slot, UE2 does not receive the PI.

[0482] In order to solve such a problem, in this modification 1, UE3 transmits PI by including it in PSCCH of the slot next to the slots scheduled consecutively. UE2 receives PSCCH of the slot next to the slots scheduled consecutively. This allows UE2 to determine whether PI is included in PSCCH. Therefore, UE2 can determine whether resources are preempted.

[0483] UE2 may hold the received data until it determines whether resources are preempted in consecutive scheduled slots. If resources are preempted, UE2 receives data excluding the preempted resources. If resources are not preempted, UE2 receives data from three consecutive slots. In this way, UE2 can avoid erroneous reception of preempted data.

[0484] The PSCCH in the second slot does not include a PI and is transmitted from UE 3 to UE 4. UE 4 obtains scheduling information of the PSSCH by receiving the PSCCH in the second slot, and becomes able to receive the PSSCH.

[0485] The method disclosed in the fourth embodiment may be applied as appropriate to the transmission process of the preempted resources in UE1 and the reception process of the preempted resources in UE2. For example, the method disclosed in the example of FIG. 25 may be applied as appropriate. Similar effects can be obtained. Also, the method disclosed in the fourth embodiment may be applied as appropriate to the processing of data of the preempted resources for UE2. For example, the method disclosed in the example of FIG. 25 may be applied as appropriate. Similar effects can be obtained.

[0486] Regarding the process of preempting the first slot reserved or scheduled from UE1 to UE2, the method disclosed in the fourth embodiment may be applied as appropriate. For example, the method disclosed in the example of Fig. 25 may be applied as appropriate. Similar effects may be obtained.

[0487] By using such a preemption method, preemption is possible even if scheduling is performed over multiple consecutive slots in SL communication.

[0488] Fig. 31 is a diagram showing a third example of a preemption method in SL communication. Like Fig. 30, Fig. 31 shows an example of a preemption method in the case where three slots including a resource to be preempted are scheduled consecutively. Unlike Fig. 30, Fig. 31 shows a case where the resource to be preempted is a minislot.

[0489] When the resource to be preempted is a minislot, the UE3 transmits the PI in the PSCCH of the next slot of the consecutively scheduled slots, similar to the method disclosed in FIG. 30. The UE2 receives the PSCCH of the next slot of the consecutively scheduled slots. This allows the UE2 to determine whether the PSCCH includes the PI. Therefore, the UE2 can determine whether the resource is preempted.

[0490] The PSCCH of the minislot to be preempted in the second slot is transmitted from UE3 to UE4, and does not include a PI. UE4 obtains scheduling information of the PSSCH by receiving the PSCCH of the minislot, and becomes able to receive the PSSCH.

[0491] After UE1 receives PI2, UE1 may transmit PI to UE2 on PSCCH. UE1 can recognize the preempted resources by receiving PI2. Therefore, UE1 can transmit PI to UE2.

[0492] For example, after UE1 receives PI2, UE1 transmits the PI in the PSCCH of the next slot after the slots consecutively scheduled for UE2. The PSCCH of the slot may include information indicating which UE transmitted the PI, such as a UE identifier. The information included in the PI may be included in the PSCCH of the slot. This allows UE2 to recognize which UE transmitted the PI.

[0493] The method disclosed in the fourth embodiment may be applied as appropriate to the transmission process of the preempted resources in UE1 and the reception process of the preempted resources in UE2. For example, the method disclosed in the example of FIG. 26 may be applied as appropriate. Similar effects can be obtained. Also, the method disclosed in the fourth embodiment may be applied as appropriate to the processing of data of the preempted resources for UE2. For example, the method disclosed in the example of FIG. 26 may be applied as appropriate. Similar effects can be obtained.

[0494] Regarding the processing for preempting the resource including the PSCCH region of the first slot reserved or scheduled from UE1 to UE2 by minislot, the method disclosed in the fourth embodiment may be applied as appropriate. For example, the method disclosed in the example of FIG. 26 may be applied as appropriate. It is possible to obtain the same effect.

[0495] Other examples of the preemption method in SL communication disclosed in the fourth embodiment may be applied as appropriate. For example, a method of providing resources for PI transmission may be applied as appropriate. In the fourth embodiment, UE1 transmits a PI to UE2, but in the present first modification, UE3 transmits a PI to UE2. UE3 needs to recognize the resource configuration for PI transmission. For this reason, the gNB may notify the UE performing SL communication of the resource configuration for PI transmission by SIB. Alternatively, the gNB may determine the resource configuration for PI transmission and notify the transmitting UE of SL communication by RRC signaling. By applying these methods, UE3 can recognize the resource configuration for PI transmission.

[0496] As another method, UE1 may notify UE3 of the resource configuration for PI transmission. For example, UE1 may notify UE3 of the resource configuration for PI transmission by RRC signaling and MAC signaling. Alternatively, UE1 may notify UE3 of the resource configuration for PI transmission by PSCCH. UE3 can recognize the resource configuration for PI transmission by receiving PSCCH. This enables UE3 to transmit PI to UE2.

[0497] In the example of the above figure, a case where resource reservation from UE1 to UE2 is performed periodically is disclosed. The method disclosed in this modified example 1 may not be applied to a case where resource reservation or scheduling from UE1 to UE2 is performed periodically, for example, it may be applied to a case where resource reservation or scheduling from UE1 to UE2 is performed non-periodically. The method disclosed in this modified example 1 may be applied to a case where resource reservation or scheduling from UE1 to UE2 is performed dynamically. It is possible to obtain the same effect.

[0498] In SL communication, information related to the service may be included in the PSCCH. A transmitting UE in SL communication transmits information related to the service by including it in the PSCCH. A transmitting UE in SL communication may transmit information related to the service by including it in the SCI and transmitting it on the PSCCH. A transmitting UE in SL communication may transmit information related to the service by including it in the SCI1 and transmitting it on the PSCCH. In this way, a UE in SL communication can obtain information related to the service by receiving the PSCCH.

[0499] The determination of whether preemption is possible may be made by the transmitting UE in the communication to be preempted. The transmitting UE determines whether the resources reserved or scheduled for the communication of another UE can be preempted for the communication of its own service. Information about the service may be used for the determination.

[0500] The transmitting UE receives a PSCCH of a resource reserved or scheduled for communication of another UE to obtain information about the service. The transmitting UE may receive a PSCCH of a resource before the resource to be preempted to obtain information about the service. The transmitting UE compares information about the service of the other UE with information about the service of the own UE to determine whether preemption is possible. The method disclosed in the fourth embodiment may be applied as a method for determining whether preemption is possible based on information about the service.

[0501] As another method, information on whether preemption is possible may be provided as information on the service. For example, for a service that requires the lowest latency characteristics, information indicating that preemption is possible may be included as information on the service. A UE for which information indicating that preemption is possible is set can preempt resources reserved or scheduled for communication of other UEs.

[0502] In this way, preemption in the SL is made possible for communication of a service that requires preemption, for example, a lower delay characteristic is required in the SL.

[0503] By using the method disclosed in this modification 1, preemption in SL is possible even when the transmitting UE of the communication to be preempted and the transmitting UE of the communication to be preempted are different. Therefore, the receiving UE of the communication to be preempted can receive data early. By implementing preemption in SL communication of a service that requires low latency characteristics, it is possible to satisfy the low latency characteristics required for communication.

[0504] Embodiment 5. Resources for SL communication are configured as a resource pool (hereinafter referred to as SLRP). The SLRP is configured in advance in the UE. Alternatively, the gNB notifies the UE of the SLRP via SIB or RRC signaling.

[0505] Figure 32 is a diagram showing a case where an SLRP is set in the UL carrier of Uu. Resources are shown in slot units. The shaded hatched portion is the resource used for UL communication of Uu, and the horizontally hatched portion is the SLRP used for SL communication. The SLRP is set within the range of the BWP (BandWidth Part) set in the UL of Uu. The SLRP is set within the range of the SL BWP. In Figure 32, the frequency range of the SLRP and the frequency range of the SL BWP are the same.

[0506] In such a case, preemption between Uu's UL communication and SL communication is possible. However, nothing has been disclosed about preemption between Uu's UL communication and SL communication. Here, we will disclose how to handle preemption between Uu's UL communication and SL communication.

[0507] Resources used for Uu UL communication are not preempted for SL communication. Resources used for Uu UL communication may be prohibited or not allowed to be preempted for SL communication. Resources outside the SLRP are not preempted for SL communication. Resources outside the SLRP may be prohibited or not allowed to be preempted for SL communication.

[0508] Resources in the SLRP are not preempted for Uu's UL communication. Preemption of resources in the SLRP for Uu's UL communication may be prohibited or not permitted. Resources other than resources for Uu's UL communication are not preempted for Uu's UL communication. Preemption of resources other than resources for Uu's UL communication for Uu's UL communication may be prohibited or not permitted.

[0509] These settings may be set for each service, or only one of the settings may be set.

[0510] By doing this, SL communication will not be performed using Uu's UL communication resources. Also, Uu's communication will not be performed using SLRP. By separating the communication resources into Uu's UL communication and SL communication, for example, even if Uu's UL communication and SL communication are performed on the same carrier, Uu's UL communication and SL communication can be easily multiplexed. This simplifies the communication processing on both the network side and the terminal side.

[0511] However, when data requiring low latency occurs in SL, such data cannot be transmitted outside of SLRP and may have to wait until the timing of SLRP. This may result in the requirement of low latency not being met. The same is true in the reverse case. When data requiring low latency occurs in UL of Uu, such data cannot be transmitted in SLRP and may have to wait until the timing of resources for UL of Uu. This may result in the requirement of low latency not being met. A method for solving such problems is disclosed.

[0512] In order to solve such problems, preemption may be implemented between UL communication and SL communication of Uu. Resources used for UL communication of Uu may be preempted for SL communication. Resources used for UL communication of Uu may be permitted to be preempted for SL communication. Resources outside the SLRP may be preempted for SL communication. Resources outside the SLRP may be permitted to be preempted for SL communication.

[0513] The UL communication resources of the preempted Uu may be limited to the BWP that the SLRP is included in. The UL communication resources of the preempted Uu may be limited to the same slot as the SLRP.

[0514] As another method, a resource pool for preemption of SL communication may be provided in the UL resources of Uu. An RP for SL preemption is set for UE of SL communication. A receiving UE of SL communication receives not only the SLRP but also the RP for SL preemption using the configuration of the set RP for SL preemption. A transmitting UE of SL communication can transmit not only the SLRP but also the RP for SL preemption using the configuration of the set RP for SL preemption.

[0515] Figure 33 shows a case where preemption of UL resources of Uu for SL communication is permitted. Resources are shown in slot units. The sand-hatched areas are resources preempted for SL communication. The UL resources of Uu are used for this preemption. The resources to be preempted for SL communication are set in the BWP that includes the SLRP.

[0516] In this way, when data that requires low latency occurs in SL, SL communication can be performed by preempting the UL resources of Uu for SL communication. In particular, even if there is an interval until the next SLRP timing, SL communication can be performed without waiting for it. This makes it possible to obtain low latency characteristics.

[0517] Resources within the SLRP may be preempted for Uu's UL communications. Resources within the SLRP may be permitted to be preempted for Uu's UL communications. Resources outside of the resources for Uu's UL communications may be preempted for Uu's UL communications. Resources outside of the resources for Uu's UL communications may be permitted to be preempted for Uu's UL communications.

[0518] The preempted SL communication resources may be limited to the BWP that includes the UL communication resources of Uu. The preempted SL communication resources may be limited to the same slot as the UL communication resources of Uu.

[0519] Figure 34 is a diagram showing a case where preemption is permitted for resources in the SLRP for Uu's UL communication. Resources are shown in slot units. The hatched area is the resource preempted for Uu's UL communication. SL communication resources are used for this preemption. The resources to be preempted for Uu's UL communication are set in Uu's BWP for UL communication.

[0520] In this way, when data that requires low latency occurs in Uu's UL, Uu's UL communication can be performed by preempting SL communication resources for Uu's UL communication. In particular, even if there is an interval until the next timing of Uu's UL communication resources, Uu's UL communication can be performed without waiting. Even when the usage load of Uu's UL communication resources is high, it is possible to preempt SL communication resources. This makes it possible to obtain low latency characteristics.

[0521] Embodiment 6 It has been agreed that BWP is used in SL in NR (Non-Patent Document 29 (Draft Report of 3GPP TSG RAN WG1 #95 v0.2.0 (Spokane, USA, 12th-16h November 2018))). Each resource pool (RP) of SL is configured (in advance) within the range of one SLBWP. Figure 35 is a diagram showing a case where two SLRPs and an SLBWP are configured in the same carrier. Each SLRP is set within the frequency range of each SLBWP. However, no specific method for setting the SLBWP is disclosed. In the sixth embodiment, a method for setting the SLBWP will be disclosed.

[0522] The SLBWP is separate from the BWP of the UL of Uu. The SLBWP is set separately from the BWP set in the UL of Uu. In this way, it is possible to set up an SLRP in a frequency band different from the BWP of the UL of Uu. SL communication is possible in a frequency band different from the BWP of the UL of Uu.

[0523] The frequency range of the SLRP setting may be SLBWP. In Uu communication, the BWP setting is used to limit the frequency range in which the UE can communicate. In SL, by setting the SLBWP to the frequency range in which the SLRP is set, the frequency range in which the UE can communicate does not need to be wider than the frequency range of the SLRP. This makes it easier to configure the UE for SL communication.

[0524] When multiple SLRPs are set within the range of one SLBWP, the smallest frequency range including the frequency ranges of the multiple SLRPs may be set as the SLBWP. Similarly, it is not necessary to set the frequency range in which the UE can communicate wider than the smallest frequency range including the frequency ranges of the multiple SLRPs set. This makes it easier to configure the UE that performs SL communication.

[0525] A method of notifying a UE of an SLBWP is disclosed. The SLRP and SLBWP may be configured separately for the UE. As described above, the SLRP is configured in advance in the UE. Alternatively, the gNB notifies the UE of the SLRP configuration by SIB or RRC signaling. Similarly, the SLBWP is configured in advance in the UE. Alternatively, the gNB notifies the UE of the SLBWP configuration by SIB or RRC signaling. The SLBWP configuration may be included in the BWP configuration of the UL of the Uu and notified. When the SLRP and SLBWP are configured separately for the UE, it is necessary to associate which SLRP corresponds to which SLBWP.

[0526] An SLRP identifier is provided to identify the SLRP. The SLRP identifier may be included in information for setting the SLBWP. The SLRP identifier of the SLRP corresponding to the SLBWP to be set is included in information for setting the SLBWP. In this way, the UE can recognize the correspondence between the SLRP and the SLBWP. In addition, the settings of the SLRP and the SLBWP can be flexibly changed individually. The amount of information in the SIB or RRC signaling for the change can be reduced.

[0527] The setting of the SLBWP for the UE may be included in the setting of the SLRP. For example, the setting of the SLBWP may be included in the setting of the SLRP by associating the setting of the SLBWP with the setting of the SLRP. In this way, the amount of signaling to be set for the UE can be reduced.

[0528] Numerology information may be included as information for setting the SLBWP. The UE becomes able to recognize the numerology of the SLBWP resources. The numerology of the SLRP may be the numerology of the corresponding SLBWP. The UE becomes able to recognize the numerology of the SLRP as well.

[0529] The UE may notify the gNB of information regarding the frequency range in which the UE can perform SL communication. The UE may include information regarding the frequency range in its capability. The UE may notify the gNB of its UE capability. The gNB sets the SLBWP for the UE using information regarding the frequency range in which the UE can perform SL communication. The gNB notifies the UE of the SLBWP setting. In this way, the UE does not need to communicate in a frequency range that exceeds the capability of the UE. This makes it possible to reduce the occurrence of malfunctions and communication interruptions in the UE.

[0530] A UE may notify a transmitting UE in SL communication of information on a frequency range in which the UE can perform SL communication. Information on the frequency range may be included in the capability information of the UE. UE capabilities may be notified between UEs in SL communication. The transmitting UE sets the SLBWP using information on the frequency range in which the receiving UE can perform SL communication. For example, the transmitting UE may set another SLBWP on the PSCCH. The transmitting UE may notify the setting of another SLBWP and SLRP. In this way, the transmitting UE does not need to communicate in a frequency range that exceeds the capability of the receiving UE. It is possible to reduce the occurrence of malfunctions and communication interruptions between UEs.

[0531] A UE performing SL communication may be set to be able to communicate in a preset frequency range. The preset frequency range may be set as a default SLBWP. Unless a BWP is set for an individual UE, a default SLBWP may be set. The SLRP is set within the frequency range of the default SLBWP. In this way, when a UE-specific setting is not required, signaling to the UE can be omitted. Also, when a UE is outside the coverage of a cell and cannot receive an SLBWP from a gNB, the default SLBWP can be used.

[0532] An SLBWP may be set for each service. An SLRP is set within the frequency range of the SLBWP for each service. Alternatively, an SLBWP may be set for each QCI. An SLRP is set within the frequency range of the SLBWP for each QCI. A QoS index used in SL may be used instead of a QCI. The SLBWP may be a default SLBWP or an SLBWP set individually for each UE. In this way, it is possible to set an appropriate SLRP for each service.

[0533] By using the method of setting the SLBWP as disclosed in the sixth embodiment, the UE can recognize the setting of the SLBWP, and the BWP can be operated in the SL communication. The UE only needs to be able to communicate within the range of the SLBWP in the SL communication. In addition, the gNB can set the SLBWP according to the UE's SL communication capability, and can set the SLRP within the range of the SLBWP.

[0534] Embodiment 7 In NR, it is supported to operate SUL (Supplementary UpLink) in Uu (Non-Patent Document 16 (TS38.300)). In Uu, SUL is configured for each cell, and non-SUL and SUL are configured in the same cell. In addition, gNB can dynamically configure SUL for UE by PDCCH. Dynamic SUL configuration is performed for each UE and for each slot.

[0535] An SUL is provided in SL communication. SL communication may be performed using the SUL. When the communication quality of SL communication performed using a normal UL, i.e., a non-SUL, deteriorates, the communication quality can be improved by using the SUL.

[0536] FIG. 36 is a conceptual diagram showing support of SUL in addition to non-SUL in SL. Non-SUL and SUL are supported in the UL of Uu. A transmitting UE can transmit to a gNB using not only non-SUL but also SUL. In SL communication, SUL is supported in addition to non-SUL. A transmitting UE in SL communication can transmit to a receiving UE using not only non-SUL but also SUL.

[0537] The SUL for SL may be the same as the SUL set for Uu. This eliminates the need to provide a separate SUL for SL, and the need for the UE to communicate through multiple SULs. This simplifies the processing in the UE.

[0538] The SUL in SL may be different from the SUL set in Uu. The SUL in SL may be set and SL communication may be performed using the SUL. In this way, the SUL for SL can be provided separately, regardless of the SUL in Uu. The SUL in SL can be flexibly set. For example, it is possible to set the SUL according to the communication quality of the SL communication. The communication quality of the SL communication can be improved.

[0539] The SLRP configuration in the SUL may be the same as the SLRP configuration in the non-SUL, which allows, for example, the same resource allocation for SL communication in the SUL and non-SUL.

[0540] The SLRP configuration in the SUL may be different from the SLRP configuration in the non-SUL, which allows the SLRP configuration in the SUL to be set to a setting appropriate for the communication load in the SUL.

[0541] The numerology may be the same for SUL and non-SUL. In this way, for example, the timing of SLRP can be made the same. Alternatively, the numerology may be different for SUL and non-SUL. In this way, it is possible to use numerology suitable for each carrier frequency of SUL and non-SUL.

[0542] The time domain configuration of the SLRP in the SUL may be the same as the time domain configuration of the SLRP in the non-SUL. The SLRP may be set in units of symbols or in units of 1 / n symbols. In this way, the time domain configuration can be made the same even when the numerology is different.

[0543] Making the time domain configuration the same is effective, for example, in the case where the transmitting UE schedules the PSSCH on the SUL with the PSCCH on the non-SUL, as described later. Since the time domain configuration of the SLRP on the non-SUL and the SLRP on the SUL are the same, the time domain scheduling information of the PSSCH on the non-SUL and the time domain scheduling information of the PSSCH on the SUL can be made the same. This makes it possible to simplify the scheduling control using the SLRP on the SUL.

[0544] The time domain configuration of the SLRP in the SUL may be made different from the time domain configuration of the SLRP in the non-SUL. By making the time domain configuration different, the timing of the non-SUL transmission and the SUL transmission in the transmitting UE is different. This eliminates the need to distribute the transmit power that the UE can transmit between the non-SUL transmission and the SUL transmission, making it possible to improve the reception quality in each link. In addition, the receiving UE does not need to simultaneously receive the non-SUL SLRP and the SUL SLRP. This simplifies the reception process in the receiving UE.

[0545] FIG. 37 is a diagram showing a case where the numerology is the same for non-SUL and SUL. In the example of FIG. 37, the SLRP configuration of non-SUL and the SLRP configuration of SUL are the same. However, since the frequencies are different for non-SUL and SUL, the frequency of the SLRP of non-SUL and the frequency of the SLRP of SUL are different. FIG. 37 shows a case where an SLRP is set in the UL carrier of Uu. Resources are shown in slot units. The shaded hatched portion is the resource used for UL communication of Uu, and the horizontally hatched portion is the SLRP used for SL communication. For both non-SUL and SUL, the SLRP is set within the range of the BWP set in the UL of Uu. The SLRP is set within the range of the SL BWP. In FIG. 37, the frequency range of the SLRP and the frequency range of the SL BWP are set to be the same.

[0546] FIG. 38 is a diagram showing a case where the numerology is different between non-SUL and SUL. The example of FIG. 38 shows a case where the time domain configuration of the SLRP is the same for non-SUL and SUL. Resources are shown in slot units. The symbol spacing of the SUL is half that of the non-SUL. The subcarrier spacing (SCS (SubCarrier Spacing)) of the SUL is twice that of the non-SUL. The SLRP is set in units of 1 / 2 symbol in the SUL numerology. In this way, even when the numerology is different between non-SUL and SUL, the time domain configuration of the SLRP can be made the same.

[0547] A method for configuring an SUL in SL (hereinafter sometimes referred to as SL SUL) is disclosed. The SUL may be pre-configured in the UE. Alternatively, the gNB may notify the UE of the SUL configuration by SIB or RRC signaling. A method for configuring an SLRP configured in an SUL in SL is disclosed. One or more SLRPs may be configured in one SUL. One SLRP configuration may be configured in one or more SULs. The SUL and the SLRP configured in the SUL may be configured in association with each other. The SLRP configuration in the SUL may be pre-configured in the UE. Alternatively, the gNB may notify the UE of the SLRP configuration in the SUL by SIB or RRC signaling.

[0548] The configuration of the SUL and the configuration of the SLRP in the SUL may be performed separately. In such a case, information for identifying the SUL may be provided. The information may be an identifier of the SUL. Alternatively, the information may be a carrier identifier of the SUL. The information for configuring the SLRP in the SUL may include information for identifying the associated SUL. In this way, for example, even if the configuration of the SUL and the configuration of the SLRP in the SUL are performed separately, the UE can recognize which SLRP configuration is configured in which SUL.

[0549] Information for identifying an SLRP may be provided. The information may be an identifier of the SLRP. Information for identifying an associated SLRP may be included as information for configuring an SUL. In this way, even if the SUL is configured and the SLRP in the SUL is configured separately, the UE can recognize which SLRP configuration is configured in which SUL.

[0550] Unlike communication in Uu, SL communication is performed inside and outside cell coverage. The SUL in SL does not have to be set for each cell. For example, the same SUL may be set within a tracking area (TA). UE in RRC_Idle state can use the SUL when performing SL communication. The same SUL may be set within a RAN-based Notification Area (RNA). UE in RRC_inactive state can use the SUL when performing SL communication.

[0551] The SUL in SL may be set for each cell. A UE in an RRC_Connected state can use the SUL when performing SL communication. The SUL in SL may be the same as the SUL in Uu. In this way, it becomes possible to perform SL communication at the same carrier frequency as the non-SUL and SUL in Uu. The SL communication process in the UE can be simplified.

[0552] A scheduling method in SL SUL is disclosed. A case where a gNB performs scheduling is disclosed. Information indicating whether or not it is an SL SUL is provided. The gNB includes information indicating whether or not it is an SUL in DCI and notifies a transmitting UE in SL communication. The gNB may include an identifier of the SL SUL in DCI and notify the transmitting UE. The gNB may include scheduling information in DCI and notify the transmitting UE. By using these pieces of information, a transmitting UE in SL communication can select resources for SL communication in the SL SUL. The transmitting UE transmits PSCCH and PSSCH for SL communication using the resources.

[0553] The UE has a transmission function and / or a reception function (hereinafter, sometimes referred to as a transmission / reception function) in the SL SUL. The UE may notify the gNB of information related to the SL SUL. The information related to the SL SUL may include information related to the transmission / reception function in the SL SUL. The information related to the transmission / reception function in the SL SUL may include a carrier frequency, a band, a numerology, a MIMO multiplexing number, etc. that can be transmitted and / or received as the SL SUL.

[0554] The UE capability may include information about the SL SUL. The UE may notify the gNB of the UE capability. The gNB configures the UE with the SL SUL using the UE's information about the SL SUL. The gNB notifies the UE of the SL SUL configuration. In this way, the UE does not need to communicate with an SL SUL that exceeds the capabilities of the UE. This makes it possible to reduce the occurrence of malfunctions and communication interruptions in the UE.

[0555] The UE may notify the transmitting UE in the SL communication of information related to its own UE's SL SUL. Information related to the SL SUL may be included in the UE's capability information. UE capabilities may be notified between UEs in SL communication. The transmitting UE configures the SL SUL using information related to the SL SUL of the receiving UE. For example, the transmitting UE may configure the SL SUL in the PSCCH. The transmitting UE may notify the configuration of the SL SUL and the SLRP on the SUL. In this way, the transmitting UE does not need to communicate with the receiving UE in an SL SUL that exceeds its capability. It is possible to reduce the occurrence of malfunctions and communication interruptions between UEs.

[0556] When a UE with an SLRP configured on an SL SUL receives SL communication, the UE searches for the SLRP on the SL SUL. The UE may receive the PSCCH of the SLRP on the SL SUL. The UE activates the search for the SLRP upon receiving a configuration notification of the SLRP on the SL SUL. The UE deactivates the search for the SLRP upon receiving a release configuration notification of the SLRP on the SL SUL.

[0557] Information indicating activation or deactivation (act / deact) of the SL SUL may be provided. A UE that receives the act / dact information of the SL SUL activates or deactivates a search for an SLRP in the SL SUL. The gNB may notify the receiving UE of the act / deact information of the SL SUL by RRC signaling.

[0558] The use of the act / deact information of the SL SUL may be limited to cases where unicast communication or groupcast communication is performed in SL. In unicast communication or groupcast communication in SL, the receiving UE is identified, unlike broadcast communication. Therefore, the act / deact information of the SL SUL can be notified to the receiving UE by RRC signaling. In the case of broadcast communication, the act / deact information may be notified as common information by SIB or RRC signaling. This is effective when the receiving UE cannot be identified.

[0559] In this way, by providing act / deact information for the SL SUL and notifying the receiving UE, the UE does not need to continue searching for an SLRP on the SLSUL from when an SLRP is set on the SL SUL until the setting is released. The UE only needs to search for an SLRP on the SL SUL from when it receives act information on the SL SUL until it receives deact information. This reduces the power consumption of the UE.

[0560] FIG. 39 and FIG. 40 are diagrams showing an example of a sequence for performing SL communication in an SL SUL. FIG. 39 and FIG. 40 are connected at the position of a boundary line BL3940. FIG. 39 and FIG. 40 show a case where a gNB configures an SL SUL and configures an SLRP. Also, FIG. 39 and FIG. 40 show a transmitting UE and a receiving UE performing SL communication with the gNB. In step ST5701, the gNB configures an SL SUL. In step ST5702, the gNB configures an SLRP in a non-SUL (nSUL) and an SUL, respectively. In steps ST5703 and ST5704, the gNB notifies the UE of the SUL configuration, the SLRP configuration in a non-SUL, and the SLRP configuration in an SUL. For example, the gNB broadcasts these configurations by including them in an SIB. Both the transmitting UE and the receiving UE performing SL communication can receive this information.

[0561] In Step ST5706, the UE receiving the SL communication receives the PSCCH in the SLRP in the non-SUL and starts searching for the PSCCH for the UE itself. In the examples of FIG. 39 and FIG. 40, the receiving UE does not start searching for the PSCCH in the SLRP in the SUL. In Step ST5705, the UE transmitting in the SL communication transmits an SR (Scheduling Request) to the gNB in ​​order to perform unicast communication on the non-SUL. The UE may notify, together with the SR or as information about the SR, for example, an identifier of the UE (receiving UE) with which the communication is to be performed, a BSR for the SL communication, and information about the service to be communicated in the SL. The information about the service may be QoS information, QCI, PPPP, a required delay time, a required slew rate, and the like.

[0562] The SR and other information are notified from the transmitting UE to the gNB using the UL of Uu. The SR and other information may be notified from the transmitting UE to the gNB using PUCCH. Early notification is possible. Alternatively, MAC signaling or RRC signaling may be used. Since HARQ is supported in MAC signaling or RRC signaling, notification is possible with a low error rate.

[0563] In Step ST5707, the gNB determines scheduling for SL communication in non-SUL. In Step ST5708, the gNB notifies the transmitting UE of scheduling information for SL communication in non-SUL. In Step ST5709, the transmitting UE performs transmission processing using the received scheduling information. In Step ST5710, the transmitting UE performs SL transmission to the receiving UE using the scheduling information received from the gNB. The transmitting UE transmits PSCCH and PSSCH.

[0564] The transmitting UE may include, in the PSCCH, an identifier of the receiving UE performing SL communication. In this way, the receiving UE searching for the PSCCH in step ST5706 can receive the PSCCH from the transmitting UE and determine that the PSCCH is intended for the receiving UE. The receiving UE that has received the PSCCH from the transmitting UE receives the PSSCH by using the scheduling information of the PSSCH included in the PSCCH. This allows the receiving UE to receive data from the transmitting UE.

[0565] The receiving UE may transmit the reception status of the data to the transmitting UE. The receiving UE may transmit the reception status of the data as HARQ feedback information (Ack / Nack). The receiving UE may also transmit channel state information (CSI) to the transmitting UE. The receiving UE may also transmit an SRS to the transmitting UE. The receiving UE may also perform measurement and transmit the measurement result to the transmitting UE. The receiving UE may perform the measurement by measuring the RSRP and RSRQ of the RS received from the transmitting UE. Alternatively, the receiving UE may measure not only the RSRP and RSRQ of the RS from the transmitting UE, but also the RSRP and RSRQ of the RS of one or more PRBs or subchannels. The receiving UE transmits the measurement result to the transmitting UE.

[0566] In step ST5711, the transmitting UE measures SL communication on non-SUL. The transmitting UE measures communication quality using a channel or signal transmitted from the receiving UE. Alternatively, the transmitting UE may use the measurement result transmitted from the receiving UE instead of the measurement. In this way, the transmitting UE can obtain measurement information on SL communication on non-SUL. Also, the transmitting UE can recognize the communication quality of SL communication on non-SUL.

[0567] In Step ST5712, the transmitting UE transmits measurement information in non-SUL SL communication to the gNB. In Step ST5713, the gNB uses the measurement information received from the transmitting UE to determine whether or not to use SUL in SL communication. A predetermined threshold may be set for communication quality. For example, when the communication quality falls below the threshold, the gNB may determine to use SUL for SL communication.

[0568] The gNB may notify the transmitting UE of a predetermined threshold in advance. The transmitting UE decides whether or not it is better to use SUL for SL communication, based on the measurement result obtained in step ST5711. If the communication quality falls below the threshold, the transmitting UE may determine that SUL is necessary for SL communication, and may request the gNB to use SUL for SL communication in step ST5712. In step ST5713, the gNB may decide to use SUL for SL communication in response to the request from the transmitting UE.

[0569] In steps ST5714 and ST5715, the gNB notifies the act information of the SL SUL. The gNB may notify the act information of the SLRP in the SL SUL. The SL SUL is activated by the notification of the act information of the SLRP in the SL SUL. In the examples of FIG. 39 and FIG. 40, the gNB notifies the transmitting UE and the receiving UE of the act information of the SLRP in the SUL by RRC signaling. The transmitting UE and the receiving UE may notify the gNB that they have completed reception of the act information of the SLRP in the SUL. RRC signaling may be used for the notification. The receiving UE that has received the act information of the SLRP in the SUL starts searching for the PSCCH of the SLRP in the SUL in step ST5716 by using the SLRP setting in the SUL received in step ST5704.

[0570] In Step ST5717, the gNB performs scheduling for SL communication in the SUL, and in Step ST5718 notifies the transmitting UE of SL scheduling information in the SUL. In Step ST5719, the transmitting UE performs transmission processing. In Step ST5720, the transmitting UE performs transmission in SL of the SUL to the receiving UE, using the scheduling information received from the gNB. The transmitting UE transmits PSCCH and PSSCH.

[0571] The transmitting UE may include, in the PSCCH, an identifier of the receiving UE performing SL communication. In this way, the receiving UE searching for the PSCCH in step ST5716 can receive the PSCCH from the transmitting UE and determine that the PSCCH is intended for the receiving UE. The receiving UE that has received the PSCCH from the transmitting UE receives the PSSCH by using the scheduling information of the PSSCH included in the PSCCH. This allows the receiving UE to receive data from the transmitting UE.

[0572] The receiving UE may apply the method disclosed in step ST5710 to the communication on the SUL. The receiving UE may transmit the reception status of the data to the transmitting UE as feedback information. The receiving UE may transmit the reception status of the data as HARQ feedback information (Ack / Nack). The receiving UE may transmit channel state information (CSI) to the transmitting UE. The receiving UE may transmit an SRS to the transmitting UE. The receiving UE may perform measurement and transmit the measurement result to the transmitting UE. The receiving UE may measure the RSRP and RSRQ of the RS received from the transmitting UE as the measurement. Alternatively, the receiving UE may measure the RSRP and RSRQ of the RS of one or more PRBs or subchannels, not limited to the RSRP and RSRQ of the RS from the transmitting UE. The receiving UE transmits the measurement result to the transmitting UE.

[0573] In step ST5721, the transmitting UE measures the SL communication on the SUL. The transmitting UE measures the communication quality by using the channel or signal transmitted from the receiving UE. Alternatively, the transmitting UE may use the measurement result transmitted from the receiving UE instead of the measurement. In this way, the transmitting UE can obtain measurement information on the SL communication on the SUL. Also, the transmitting UE can recognize the communication quality of the SL communication on the SUL.

[0574] In step ST5722, the transmitting UE transmits measurement information on SL communication in SUL to the gNB. The gNB uses the measurement information received from the transmitting UE to determine whether or not to use non-SUL in SL communication. A predetermined threshold may be set for communication quality. For example, when the communication quality falls below the threshold, the gNB may determine to use non-SUL for SL communication.

[0575] This enables SL communication over SUL.

[0576] The same applies to the case of deactivation of the SUL. For example, the gNB that has received the measurement information of the SL communication of the SUL in step ST5722 judges whether or not to terminate the use of the SUL for SL communication. For example, if the communication quality of the SL communication in the SUL falls below a predetermined threshold, the use of the SUL for SL communication is terminated. The gNB that has decided to terminate the use of the SUL for SL communication in the SUL notifies the transmitting UE and the receiving UE of deact information of the SLRP in the SUL. The deact information may be notified by RRC signaling. The transmitting UE and the receiving UE may notify the gNB that they have completed reception of the deact information of the SLRP in the SUL. The completion of the reception may be notified by RRC signaling. The receiving UE that has received the deact information of the SLRP in the SUL terminates the search for the PSCCH of the SLRP in the SUL.

[0577] This allows the setting of SUL in SL, and also enables activation and deactivation of SUL use. Therefore, the receiving UE only needs to search for SLRP on SL SUL from the reception of SL SUL act information to the reception of deact information. This reduces the power consumption of the UE.

[0578] In the examples of Figures 39 and 40, the transmitting UE and the receiving UE do not end SL communication in the non-SUL even after receiving the activation of the SLRP in the SUL. The transmitting UE and the receiving UE may perform SL communication between the non-SUL and the SUL. Also, in the non-SUL, activation and deactivation information for non-SUL use in SL may be provided. By using a method similar to the method of notifying act / deact information in the SUL, activation and deactivation for non-SUL use in SL can be performed in the non-SUL.

[0579] In step ST5710, it has been disclosed that the receiving UE measures SL communication in non-SUL and transmits the measurement result to the transmitting UE. Also, in step ST5720, it has been disclosed that the receiving UE measures SL communication in SUL and transmits the measurement result to the transmitting UE. The measurement does not have to be limited to either non-SUL or SUL. The receiving UE may perform measurement in non-SUL and SUL. It is preferable to transmit the measurement results of non-SUL and SUL on the UL in which SL communication is being performed with the transmitting UE.

[0580] The gNB may use the non-SUL measurement results and the SUL measurement results of the receiving UE or the transmitting UE to determine whether to perform SL communication in the non-SUL or the SUL. For example, the gNB may perform SL communication in the non-SUL when the SL communication quality in the non-SUL is better than the SL communication quality in the SUL, and may perform SL communication in the SUL when the SL communication quality in the SUL is better than the SL communication quality in the non-SUL. In this way, SL communication with better communication quality is possible.

[0581] Regarding the use of non-SUL in SL, upon receiving an activation of the SLRP in the SUL, the transmitting UE and receiving UE may end transmission and reception in the non-SUL. Also, upon receiving a deactivation of the SLRP in the SUL, the transmitting UE and receiving UE may start transmission and reception in the non-SUL. In this way, SL communication using one UL, either non-SUL or SUL, is possible. The UE does not need to perform SL communication using both non-SUL and SUL. The receiving UE only needs to search for the PSCCH of either non-SUL or SUL. Power consumption of the receiving UE can be reduced.

[0582] FIG. 41 and FIG. 42 are diagrams showing an example of a sequence for performing SL communication in SL SUL. FIG. 41 and FIG. 42 are connected at the position of the boundary line BL4142. In FIG. 41 and FIG. 42, the same step numbers are assigned to steps common to FIG. 39 and FIG. 40, and common explanations are omitted. The examples of FIG. 41 and FIG. 42 are different from the examples of FIG. 39 and FIG. 40 in the method of notifying act information of SLRP in SUL. In the examples of FIG. 41 and FIG. 42, in step ST5801, the gNB transmits act information of SLRP in SUL to the transmitting UE. The gNB includes the act information of SLRP in SUL in DCI and notifies it on PDCCH. The transmitting UE that has received this act information of SLRP in SUL transmits act information of SLRP in SUL to the receiving UE in step ST5802. The transmitting UE includes the act information of SLRP in SCI and notifies it on PSCCH transmitted on non-SUL.

[0583] Since the receiving UE has received the PSCCH from the transmitting UE in the non-SUL, it can receive the act information of the SLRP in the SUL that is included in the PSCCH. Upon receiving the act information of the SLRP in the SUL, the receiving UE can start searching for the PSCCH of the SLRP in the SUL in Step ST5716.

[0584] This allows for early activation / deactivation of the SL SUL, enabling SL communication on a dynamic SL SUL, which further reduces the power consumption of the UE.

[0585] In the examples of Figures 41 and 42, the transmitting UE notifies the receiving UE of the activation / deactivation of the SL SUL. As another example, the gNB may include the act / deact information of the SLRP in the DCI and notify the receiving UE on the PDCCH. A similar effect can be obtained.

[0586] In the examples of Figures 39 and 40 and the examples of Figures 41 and 42, in SL communication on the SUL, scheduling from a transmitting UE to a receiving UE is performed using the PSCCH of the SUL. Another example will be disclosed.

[0587] In SL communication, scheduling on the SUL from a transmitting UE to a receiving UE may be performed using a non-SUL PSCCH. In SL communication, the transmitting UE may schedule the SUL PSSCH for the receiving UE using the non-SUL PSCCH. When the receiving UE receives the non-SUL PSCCH and the SUL PSSCH is scheduled, the receiving UE receives the SUL PSSCH according to the scheduling.

[0588] Information indicating whether non-SUL or SUL scheduling is to be performed may be provided. In the case of performing SL communication in one or more non-SULs and one or more SULs, information indicating which non-SUL or SUL scheduling is to be performed may be provided. Alternatively, information indicating that scheduling is to be performed in the SUL may be provided. The information may be included in the SCI. The information may be included in the SCI and mapped to the PSCCH.

[0589] When the numerologies are different between non-SUL and SUL, in order to derive the scheduling information in the SUL from the scheduling information in the non-SUL, a conversion may be performed according to the ratio of the symbol duration or SCS of each numerology.

[0590] In this way, the transmitting UE can transmit the PSCCH only on the non-SUL, which simplifies the PSCCH transmission process. Also, the receiving UE only needs to search for and receive the PSCCH on the non-SUL. This simplifies the PSCCH reception process of the receiving UE, which reduces power consumption.

[0591] Information indicating whether to perform non-SUL or SUL scheduling may be used together with SL SUL act / deact information. The transmitting UE includes SL SUL act information and scheduling information of PSSCH on SUL in SCI and notifies the receiving UE via PSCCH on non-SUL. By receiving PSCCH on non-SUL, the receiving UE can recognize that SL SUL has been activated and PSSCH has been scheduled on the SUL. The receiving UE can receive PSSCH on SUL early.

[0592] The transmitting UE includes the deactivation information of the SL SUL and the scheduling information of the PSSCH on the non-SUL in the SCI and notifies the receiving UE via the PSCCH on the non-SUL. Alternatively, when information indicating that scheduling is performed on the SUL is provided, the information is not notified. By receiving the PSCCH on the non-SUL, the receiving UE can recognize that the SL SUL has been deactivated and that the PSSCH has been scheduled on the non-SUL. The receiving UE can receive the PSSCH on the non-SUL early.

[0593] The information indicating whether non-SUL or SUL scheduling is to be performed may indicate activation / deactivation of the SL SUL. If scheduling on the SUL is indicated, the SUL may be activated. Alternatively, if scheduling on a non-SUL is indicated, the SUL may be deactivated. By transmitting and receiving information indicating whether non-SUL or SUL scheduling is to be performed for each scheduling, activation / deactivation of the SL SUL can be performed.

[0594] In the SL communication, it has been disclosed that the scheduling on the SUL from the transmitting UE to the receiving UE is performed using the PSCCH of the non-SUL. In contrast, the scheduling on the non-SUL from the transmitting UE to the receiving UE may be performed using the PSCCH of the SUL. The above-mentioned method may be applied appropriately.

[0595] In SL communication, either the non-SUL or the SUL may be set as a primary link, and the transmitting UE and the receiving UE may transmit and receive the PSCCH for SL communication on the primary link. The primary link may be set together with the setting of the SL SUL. Alternatively, the primary link may be set together with the setting of the activation / deactivation of the SL SUL.

[0596] In this way, the transmitting UE only needs to transmit the PSCCH on either the non-SUL or the SUL, simplifying the transmission process. Also, the receiving UE only needs to search for and receive the PSCCH on the non-SUL. The receiving UE's PSCCH reception process can be simplified, and power consumption can be reduced. Also, the primary link can be changed according to communication quality, communication range, communication load, etc., which improves communication quality, improves resource usage efficiency, and reduces the delay time of SL communication by reducing resource usage collisions with other UEs.

[0597] The switching between non-SUL and SUL in the UL of Uu may be linked to the switching between non-SUL and SUL in SL. For example, when the SUL is set in the UL of Uu by the gNB, the transmitting UE also sets the SL SUL in SL communication. In this way, for example, when the frequency band of the SUL of the UL of Uu and the frequency band of the SUL of SL are set to the same, it becomes possible to determine in the UL of Uu whether or not it is better to use the frequency band.

[0598] In the examples of Figures 39 and 40 and the examples of Figures 41 and 42, it has been disclosed that HARQ feedback for data transmission on the SUL is transmitted on the SUL. When symbols from the transmitting UE to the receiving UE and symbols from the receiving UE to the transmitting UE are configured in one slot, HARQ feedback may be transmitted using symbols from the receiving UE to the transmitting UE of resources reserved on the SUL for SL communication. The transmitting UE receives HARQ feedback from the receiving UE for data transmission on the SUL on the SUL.

[0599] Scheduling information for HARQ feedback transmission in the receiving UE may be included in the SCI and mapped to the PSCCH. For example, the scheduling information may be the time interval from PSCCH transmission to HARQ feedback transmission. The time unit may be, for example, a slot, a minislot, a subframe, a symbol, a TTI, etc.

[0600] By transmitting the PSSCH and HARQ feedback on the same SUL, it becomes possible to facilitate the scheduling of the HARQ feedback for the PSSCH, especially the scheduling in the time domain. This makes it possible to facilitate the scheduling control of the transmitting UE, and also to facilitate the processing from the PSSCH to the HARQ feedback in the receiving UE.

[0601] As another example of a method of transmitting HARQ feedback, HARQ feedback for data transmission on the SUL may be transmitted on the non-SUL. The HARQ feedback may be transmitted using symbols from the receiving UE to the transmitting UE on resources reserved on the non-SUL for SL communication. The transmitting UE receives HARQ feedback from the receiving UE for data transmission on the SUL on the non-SUL.

[0602] In this way, it becomes possible to transmit and receive control channels between the transmitting UE and the receiving UE on the non-SUL. Only data can be transmitted and received using the SUL. It becomes possible to offload data onto the SUL, and it becomes possible to reduce the communication load on the non-SUL.

[0603] As another example, HARQ feedback for data transmission on a non-SUL may be transmitted on the SUL, with similar benefits.

[0604] It may be possible to configure whether the HARQ feedback is transmitted in non-SUL or SUL. Information indicating whether the HARQ feedback is transmitted in non-SUL or SUL may be provided. The transmitting UE may include the information in the SCI, map it to the PSCCH, and notify the receiving UE. The information may be notified together with scheduling information of the PSSCH. Also, the information may be included in the scheduling information for transmitting the HARQ feedback.

[0605] In this way, the link for transmitting HARQ feedback can be changed depending on communication quality, communication range, communication load, etc., thereby improving communication quality, improving resource usage efficiency, and reducing the delay in SL communication by reducing resource usage collisions with other UEs.

[0606] As a method of notifying information indicating whether the HARQ feedback is to be transmitted in non-SUL or SUL, PC5 control signaling may be used from the transmitting UE to the receiving UE. Alternatively, RRC signaling may be used. Alternatively, MAC signaling may be used. This can reduce the reception error rate.

[0607] The gNB may determine whether to transmit HARQ feedback in non-SUL or SUL. The gNB includes the information in DCI and notifies the transmitting UE of the information in PDCCH. Alternatively, the information may be notified by RRC signaling or MAC signaling. The reception error rate can be reduced. The transmitting UE that receives the information may notify the receiving UE in SL communication of the information by applying the above-mentioned method.

[0608] The gNB may notify the receiving UE of the information. The notification may be made using a similar method.

[0609] By the gNB notifying the transmitting UE whether to transmit HARQ feedback via non-SUL or SUL, it is possible to reduce the latency of SL communication by reducing resource usage collisions with other UEs.

[0610] In the examples of Figures 39 and 40 and the examples of Figures 41 and 42, it is disclosed that the gNB performs SL scheduling on the SUL. Another example is disclosed. A transmitting UE in SL communication may perform SL scheduling on the SUL. A resource for SL communication may be selected from within the SLRP on the SUL. The transmitting UE senses available resources from within the SLRP on the SUL, and selects and reserves resources to be used for SL communication from among the available resources.

[0611] When the SLRP is set on the SUL by the above-mentioned method or when the SLRP on the SUL is activated, the receiving UE searches for the PSCCH in the SLRP on the SUL, thereby becoming able to receive the PSCCH from the transmitting UE.

[0612] In this way, the transmitting UE can perform SL scheduling on the SUL. Since the transmitting UE can perform SL scheduling on the SUL without waiting for scheduling from the gNB, SL communication can be performed early. SL communication can be performed with low latency.

[0613] A UE performing SL communication may transmit a synchronization signal (SS) in the SL SUL. When the SUL of Uu and the SL SUL have the same carrier frequency, the UE performing SL communication may receive the SS of the gNB to achieve synchronization. When a UE performing SL communication is outside the coverage of the gNB, the UE performing SL communication may receive the SS from a UE transmitting the SS in a nearby SL SUL to achieve synchronization. A UE performing SL communication may determine whether or not it is within the coverage of the gNB and whether or not a UE transmitting the SS is nearby using the reception power or reception quality.

[0614] For this determination, a predetermined threshold value of reception power or reception quality may be set. For example, when a UE performing SL communication receives reception power equal to or greater than the predetermined threshold value from a gNB or a UE transmitting an SS, the UE synchronizes with the gNB or the UE transmitting the SS. In this way, it is not necessary to synchronize the frame timing of non-SUL and SUL, and synchronization at SUL is possible.

[0615] By using the SUL setting method as disclosed in the seventh embodiment, it becomes possible to use the SUL in SL communication. Therefore, even in cases where the communication quality of SL communication performed via a non-SUL deteriorates, the communication quality can be improved by using the SUL.

[0616] Embodiment 8 In NR Uu communications, RLF (Radio Link Failure) processing is specified (Non-Patent Document 16 (TS38.300)). For Uu communications, RLF processing is performed when a UE loses synchronization with a gNB. When a UE cannot resynchronize with a gNB, RLF occurs, and the UE performs cell reselection and executes RRC re-establishment. If RRC re-establishment is not possible, the UE transitions to RRC_Idle.

[0617] Support for unicast and groupcast is being considered for NR SL communications. For this reason, a method of processing RLF is also required for SL communications. However, SL communications are communications between UEs, not between UEs and gNBs. For this reason, conventional RLF processing, which is the RLF for communications between UEs and gNBs, cannot be applied without any ingenuity.

[0618] The problem is how to handle the situation when SL communication between the transmitting UE and the receiving UE becomes impossible. For example, how to determine that communication has failed, and how to handle the situation when communication has failed. If these methods are unclear, the transmitting UE and the receiving UE will be unable to process or will be unable to process in a coordinated manner, and communication will not be carried out normally. In the eighth embodiment, a method for solving such problems will be disclosed.

[0619] A method for determining whether or not a synchronous state is established in unicast or groupcast communication is disclosed. A receiving UE determines whether or not a synchronous state is established. To determine whether or not a synchronous state is established, a PSCCH, not a PDCCH received from a gNB, is used. The receiving UE may determine that a synchronous state (In-Sync) is established when the PSCCH transmitted from the transmitting UE is received a predetermined number of times in succession. The receiving UE may determine that a synchronous state is established when the PSCCH is continuously received for a predetermined period of time. The receiving UE may determine that a synchronous state is established when the PSCCH is continuously received a predetermined number of times within a predetermined period of time.

[0620] The receiving UE may determine that it is out of sync when it is unable to receive the PSCCH transmitted from the transmitting UE a predetermined number of times in succession. The receiving UE may determine that it is out of sync when it is unable to receive the PSCCH transmitted from the transmitting UE for a predetermined continuous period of time. The receiving UE may determine that it is out of sync when it is unable to receive the PSCCH transmitted from the transmitting UE a predetermined number of times in succession within a predetermined period of time.

[0621] Information such as a predetermined number of times and a predetermined time used to determine whether or not the UE is in a synchronized state may be notified from the gNB to the UE performing SL communication. The information may be included in broadcast information and broadcast. The predetermined value may be determined for each cell. Alternatively, the information may be notified to each UE individually by RRC signaling. Alternatively, the information may be statically determined in advance by a standard or the like. Alternatively, the information may be preset in the UE performing SL communication.

[0622] Information such as the predetermined number of times and the predetermined time may be set for each service. The information may be set for each QoS of the service. For example, the predetermined value can be determined according to the delay time required for each service. The notification method from the gNB to the UE may be the above-mentioned method.

[0623] Another method is disclosed. As a method of determining whether or not a synchronous state is established in unicast or groupcast communication, a synchronization signal (SS) in SL (hereinafter referred to as SLSS) may be used. The receiving UE determines whether or not a synchronous state is established using the SLSS transmitted from the UE synchronized in SL. The receiving UE may determine that the UE is in a synchronized state when it is able to receive the SLSS transmitted from the UE synchronized in SL a predetermined number of times in succession. The receiving UE may determine that the UE is out of synchronization when it is unable to receive the SLSS transmitted from the UE synchronized in SL a predetermined number of times in succession.

[0624] As with synchronization in the PSCCH, synchronization may be performed not a predetermined number of times, but at a predetermined time, or a predetermined number of times within a predetermined time.

[0625] In SL, the UE with which the receiving UE synchronizes may differ from the transmitting UE. As described above, by determining whether to use PSCCH or SLSS to determine whether the UE is in a synchronized state, the receiving UE in SL communication can clearly determine whether it is in a synchronized state. As a result, the occurrence of malfunctions can be reduced.

[0626] As a method of determining whether or not the signal is in sync, a method using PSCCH and a method using SLSS may be combined. For example, when the PSCCH and SLSS are not received a predetermined number of times in a predetermined time, the signal is determined to be out of sync, and otherwise the signal is determined to be in sync. In this way, the signal can be determined to be out of sync at an early stage. The signal can be quickly moved to the next process.

[0627] Also, for example, when both PSCCH and SLSS are out of sync, it may be determined that unicast or groupcast communication is out of sync. Otherwise, it may be determined that the communication is in sync. When only PSCCH is out of sync, or when only SLSS is out of sync, the communication is in sync. In this way, it is possible to reduce the number of situations in which the communication goes out of sync. It is possible to maintain the communication state as long as possible.

[0628] The process of a UE that has determined that it is out of sync will be disclosed. The UE will perform resynchronization. If the UE determines that it is out of sync using the PSCCH, it will receive the PSCCH from the transmitting UE and perform resynchronization. In this way, the receiving UE will be able to receive the PSCCH and PSSCH from the transmitting UE. Unicast communication in SL will be possible again.

[0629] When out-of-synchronization is determined using the SLSS, the UE receives the SLSS and performs resynchronization. The SLSS may be received by receiving the SLSS of the UE that was most recently synchronized. A threshold value for the reception power or reception quality of the SLSS for resynchronization may be set, and synchronization may be performed with the SLSS of the UE that is equal to or greater than the threshold.

[0630] The thresholds of the reception power, reception quality, etc. of the SLSS for resynchronization may be the same as the thresholds of the reception power, reception quality, etc. of the SLSS for synchronization. This makes it easier to control the synchronization process. Alternatively, the thresholds of the reception power, reception quality, etc. of the SLSS for resynchronization may be different from the thresholds of the reception power, reception quality, etc. of the SLSS for synchronization. For example, the thresholds for resynchronization are made lower than the thresholds for synchronization. This makes it easier to resynchronize, and shortens the delay time until communication becomes possible again.

[0631] The receiving UE that has received the SLSS and performed resynchronization receives the PSCCH from the transmitting UE. In this way, the receiving UE is able to receive the PSCCH and PSSCH from the transmitting UE. Unicast communication in SL becomes possible again.

[0632] When out-of-synchronization is determined using the SLSS, the PSCCH from the transmitting UE may still be receivable. In such a case, the receiving UE that has received the SLSS and performed resynchronization may continue to receive the PSCCH from the transmitting UE. In such a case, unicast communication in SL can be continued.

[0633] These resynchronization methods may be used in combination as appropriate depending on the method of determining whether or not the device is in a synchronized state, making it possible to simplify processing for out-of-synchronization and resynchronization.

[0634] If the receiving UE is unable to resynchronize after it has become out of sync, it should end the SL communication. It is determined that unicast or groupcast communication in SL has ended. The receiving UE that has ended the SL communication performs new synchronization processing for SL communication, searches for the PSCCH of the SLRP, receives the PSCCH from the transmitting UE, and starts unicast or groupcast communication processing. In this way, new SL communication can be started even if the receiving UE has become out of sync due to deterioration of communication quality in the SL communication.

[0635] The receiving UE that has ended the SL communication releases the RRC settings set for these communications in the unicast communication or groupcast communication. It may also release the settings of each protocol in the SL communication. For example, the settings of PDCP, RLC, MAC, PHY, etc. in the SL communication are released. Alternatively, data buffered in PDCP, RLC, MAC, and PHY in the SL communication is discarded. In this way, it is possible to reduce the processing load and buffer capacity in the UE.

[0636] In addition, when a bearer is set in SL, the receiving UE that has terminated the SL communication may release the bearer setting. Each protocol configured in the bearer set in SL is released. The same effect can be obtained.

[0637] The time from the start of the out-of-sync state may be managed by a timer. If resynchronization occurs within the timer from the start of the out-of-sync state, the state is returned to a synchronized state and the timer is reset. If resynchronization cannot occur within the timer from the start of the out-of-sync state, the SL communication is terminated and the timer is reset. In this way, it is possible to avoid the period required for resynchronization processing from becoming too long.

[0638] If the receiving UE is unable to resynchronize after becoming out of sync, the receiving UE may not release or retain some or all of the RRC configurations configured for unicast or groupcast communication. For example, the receiving UE may not release or retain some or all of the configurations of PDCP, RLC, MAC, PHY, etc. in SL communication. Alternatively, the receiving UE may not discard or retain some or all of the data buffered in PDCP, RLC, MAC, PHY in SL communication.

[0639] Also, in the case of setting up a bearer in SL, if the receiving UE is unable to resynchronise after becoming out of sync, the receiving UE may not release or may retain some or all of the bearer setup.

[0640] The transmitting UE may retain some or all of the RRC settings or some or all of the bearer settings set for unicast or groupcast communication while the receiving UE retains them. The retention period may be set in consideration of a timer from the start of an out-of-sync state to resynchronization, and a timer from the time when resynchronization is not possible to the completion of synchronization processing for SL communication, which will be described later. If communication with the receiving UE is not resumed even after the retention period has elapsed, the transmitting UE releases some or all of the retained RRC settings or some or all of the bearer settings. In this way, even if SL communication is resumed, communication can be resumed early by using the retained settings.

[0641] If the receiving UE is unable to resynchronize after going out of synchronization, it retains some or all of these settings, performs new synchronization processing for SL communication, searches for the PSCCH of the SLRP, receives the PSCCH from the transmitting UE, and starts unicast communication or groupcast communication processing. In this way, even when new SL communication is started, communication can be started quickly by using the retained settings.

[0642] If the receiving UE is unable to resynchronize after going out of synchronization, it retains some or all of these settings, performs new synchronization processing for SL communication, searches for the PSCCH of the SLRP, receives the PSCCH from the transmitting UE, and starts unicast communication or groupcast communication processing. In this way, even when new SL communication is started, communication can be started quickly by using the retained settings.

[0643] If the receiving UE is unable to resynchronize after it has become out of sync, it may further perform resynchronization processing while retaining some or all of these settings. The further resynchronization processing may be the same as the above-mentioned resynchronization processing performed after the receiving UE has become out of sync. In this way, even if SL communication is resumed after resynchronization, communication can be resumed quickly by using the retained settings.

[0644] If resynchronization is not possible after an out-of-synchronization state, the time from the point in time when resynchronization was not possible may be managed by a timer. If a new synchronization process for SL communication is completed within the timer from the point in time when resynchroni...

Claims

1. A communication terminal in a communication system including a plurality of communication terminals capable of communicating with each other in a side link and a base station that wirelessly communicates with each of the plurality of communication terminals, A bandwidth portion (SLBWP) for the sidelink is set separately from a bandwidth portion (ULBWP) for the uplink. Communications terminal.

2. Receive configuration information indicating a configuration regarding the SLBWP from the base station by SIB or RRC signaling; The communication terminal according to claim 1.

3. Within the scope of the SLBWP, one or more sidelink resource pools are included. The communication terminal according to claim 2.

4. The configuration information includes identifiers corresponding to the one or more sidelink resource pools, The communication terminal according to claim 3.

5. The setting information includes information regarding numerology for the SLBWP, Each of the numerologies of the one or more sidelink resource pools corresponds to the numerology for the SLBWP; The communication terminal according to claim 3.

6. A preset range is provided for the SLBWP, Using the preset range when outside the coverage of the base station; The communication terminal according to claim 1.

7. transmitting UE capability information to the base station, the UE capability information including information regarding a frequency range in which sidelink communication is possible; The communication terminal according to claim 1.

8. Transmitting and receiving UE capability information indicating capabilities of the communication terminal to and from another communication terminal; The communication terminal according to claim 1.

9. A base station in a communication system including a plurality of communication terminals capable of communicating with each other in a side link, and a base station that wirelessly communicates with each of the plurality of communication terminals, A bandwidth portion (SLBWP) for the sidelink is set separately from a bandwidth portion (ULBWP) for the uplink. Base station.

10. A communication system including a plurality of communication terminals capable of communicating with each other in a side link, and a base station that wirelessly communicates with each of the plurality of communication terminals, A bandwidth portion (SLBWP) for the sidelink is set separately from a bandwidth portion (ULBWP) for the uplink. Communication systems.

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