Terminal device, method, and integrated circuit

Abstract

To provide a terminal device, a method, and an integrated circuit that efficiently perform communication control in side link communication.SOLUTION: A first terminal device capable of side link communication receives a first message from a second terminal device, determines information based on a reference signal received power (RSRP) of the first message received from the second terminal device, and transmits a second message including the information to a third terminal device. The first message and the second message are messages used for selecting a terminal device in charge of transferring side link communication performed by the second terminal device to the third terminal device.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a terminal device, a method, and an integrated circuit. [Background technology]

[0002] The 3rd Generation Partnership Project (3GPP [registered trademark]), a standardization project for cellular mobile communication systems, is conducting technical studies and formulating standards for cellular mobile communication systems, including radio access, core networks, services, etc.

[0003] For example, technical studies and standardization of E-UTRA (Evolved Universal Terrestrial Radio Access) have begun in 3GPP as a radio access technology (RAT) for 3.9G and 4G cellular mobile communication systems. 3GPP is currently conducting technical studies and standardization of E-UTRA extension technologies. E-UTRA is also called Long Term Evolution (LTE: registered trademark), and the extension technologies are sometimes called LTE-Advanced (LTE-A) and LTE-Advanced Pro (LTE-A Pro).

[0004] Additionally, 3GPP has begun technical studies and standardization of NR (New Radio, or NR Radio access) as a radio access technology (RAT) for 5th Generation (5G) cellular mobile communication systems. 3GPP is currently conducting technical studies and standardization of NR extension technologies. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] 3GPP TS 38.331 v17.2.0, "Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specifications" pp37-1107 [Non-Patent Document 2] 3GPP TS 38.321 v17.1.0, "NR; Medium Access Control (MAC) protocol specification" pp17-104 [Non-Patent Document 3] 3GPP TS 38.213 v17.1.0, "NR; Physical layer procedures for control" pp14-20 [Non-Patent Document 4] 3GPP TS 38.215 v17.1.0, "NR; Physical layer measurements" pp16-18 [Non-Patent Document 5] 3GPP TS 23.304 v17.2.1, "Proximity based Services (ProSe) in the 5G System (5GS)" pp12-97 [Non-Patent Document 6] 3GPP TS 38.300 v17.2.0, "NR; NR and NG-RAN Overall Description" pp31-170 [Non-Patent Document 7] RP-221262, "Revised WID on NR sidelink relay enhancements" [Non-Patent Document 8] 3GPP TR 23.700-33 v1.1.0, "Study on system enhancement for Proximity based Services (ProSe) in the 5G System (5GS); Phase 2" [Summary of the Invention] [Problem to be solved by the invention]

[0006] 3GPP is considering a technology called sidelink, which allows terminal devices to communicate directly with each other without going through the core network, as an extension technology of NR. In addition, research has begun on a technology (UE-to-UE relay) that allows other terminal devices to be added between terminal devices and supports communication between terminal devices.

[0007] One aspect of the present invention has been made in consideration of the above-mentioned circumstances, and one of its objects is to provide a terminal device, a base station device, a communication method, and an integrated circuit that can efficiently perform communication control. [Means for solving the problem]

[0008] To achieve the above object, one aspect of the present invention provides the following: That is, one aspect of the present invention provides a first terminal device capable of sidelink communication, the first terminal device including a processing unit, a receiving unit for receiving a first message from a second terminal device, and a transmitting unit, wherein the processing unit determines information based on Reference Signal Received Power (RSRP) of the first message received from the second terminal device, the transmitting unit transmits a second message including the information to a third terminal device, and the first message and the second message are messages used to select a terminal device responsible for forwarding sidelink transmissions of the second terminal device to the third terminal device.

[0009] Another aspect of the present invention is a method for a first terminal device capable of sidelink communication, comprising the steps of receiving a first message from a second terminal device, determining information based on Reference Signal Received Power (RSRP) of the first message received from the second terminal device, and transmitting a second message including the information to a third terminal device, wherein the first message and the second message are messages used to select a terminal device responsible for forwarding sidelink transmissions of the second terminal device to the third terminal device.

[0010] Another aspect of the present invention is an integrated circuit implemented in a first terminal device capable of sidelink communication, having the following functions: receiving a first message from a second terminal device; determining information based on Reference Signal Received Power (RSRP) of the first message received from the second terminal device; and transmitting a second message including the information to a third terminal device, wherein the first message and the second message are messages used to select a terminal device responsible for forwarding sidelink transmissions of the second terminal device to the third terminal device.

[0011] These comprehensive or specific aspects may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium, or may be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium. [Effects of the Invention]

[0012] According to one aspect of the present invention, a terminal device, a method, and an integrated circuit can realize efficient communication control processing. [Brief explanation of the drawings]

[0013] [Figure 1]1 is a schematic diagram of a communication system according to an embodiment of the present invention. [Figure 2] FIG. 10 is a diagram illustrating an example of a protocol configuration of a side link according to the present embodiment. [Figure 3] FIG. 10 is a diagram illustrating an example of a protocol configuration of a side link according to the present embodiment. [Figure 4] FIG. 10 is a diagram illustrating an example of a protocol configuration of a side link according to the present embodiment. [Figure 5] FIG. 2 is a block diagram showing the configuration of a terminal device according to the embodiment. [Figure 6] FIG. 10 is a diagram illustrating an example of a protocol configuration of a side link according to the present embodiment. [Figure 7] FIG. 10 is a diagram illustrating an example of a protocol configuration of a side link according to the present embodiment. [Figure 8] 10 shows an example of processing in this embodiment. [Figure 9] 10 shows an example of processing in this embodiment. [Figure 10] 10 shows an example of processing in this embodiment. [Figure 11] 10 shows an example of processing in this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, this embodiment will be described in detail with reference to the drawings.

[0015] In this embodiment, the names of the nodes and entities and the processes performed by the nodes and entities when the radio access technologies are NR and E-UTRA will be described, but this embodiment may be applied to other radio access technologies. The names of the nodes and entities in this embodiment may be different names.

[0016] Fig. 1 is a schematic diagram of a communication system according to this embodiment. Note that the functions of each node, radio access technology, core network, interface, etc. described using Fig. 1 are only some of the functions closely related to this embodiment, and the system may have other functions.

[0017] E-UTRA may be a radio access technology. E-UTRA may also be the air interface between the UE 122 and the ng-eNB 100. The air interface 112 between the UE 122 and the ng-eNB 100 may be referred to as the Uu interface. The ng-eNB (ng E-UTRAN Node B) 100 may be a base station device. The ng-eNB 100 may have the E-UTRA protocol described below. The E-UTRA protocol may be composed of the E-UTRA User Plane (UP) protocol described below and the E-UTRA Control Plane (CP) protocol described below. The ng-eNB 100 may terminate the E-UTRA user plane protocol and the E-UTRA control plane protocol for the UE 122. A radio access network composed of eNBs may be referred to as E-UTRAN.

[0018] NR may be a radio access technology. NR may also be an air interface between the UE 122 and the gNB 102. The air interface 112 between the UE 122 and the gNB 102 may be referred to as a Uu interface. The gNB (g Node B) 102 may be a base station device. The gNB 102 may have the NR protocol described below. The NR protocol may be composed of an NR user plane (User Plane: UP) protocol described below and an NR control plane (Control Plane: CP) protocol described below. The gNB 102 may terminate the NR user plane protocol and the NR control plane protocol for the UE 122.

[0019] The interface 110 between the ng-eNB 100 and the gNB 102 may be referred to as an Xn interface. The ng-eNB and the gNB may connect to the 5GC via an interface called an NG interface (not shown). The 5GC may be a core network. One or more base station devices may connect to the 5GC via the NG interface.

[0020] A state in which a base station device can be connected to only via the Uu interface may be referred to as Inside NG-RAN Coverage or In-Coverage (IC). A state in which a base station device cannot be connected to only via the Uu interface may be referred to as Outside NG-RAN Coverage or Out-of-Coverage (OOC). The air interface 114 between UEs 122 may be referred to as a PC5 interface. Communication between UEs 122 via the PC5 interface may be referred to as sidelink (SL) communication. A terminal device capable of sidelink communication may be referred to as a sidelink communication-capable terminal device.

[0021] In the following description, the ng-eNB 100 and / or the gNB 102 will also be referred to simply as a base station device, and the UE 122 will also be referred to simply as a terminal device or a UE. The PC5 interface will also be referred to simply as PC5, and the Uu interface will also be referred to simply as Uu.

[0022] Sidelink is a technology that enables direct communication between terminal devices via PC5, and sidelink transmission and reception on PC5 is performed inside and outside the NG-RAN coverage.

[0023] There are three transmission modes for NR SL communication, and SL communication is performed in one of the transmission modes using a pair of a source layer-2 (L2) ID and a destination layer-2 (L2) ID. The source layer-2 ID and the destination layer-2 ID may be referred to as a source L2 ID and a destination L2 ID, respectively. The three transmission modes are "unicast transmission," "groupcast transmission," and "broadcast transmission." Note that the transmission modes may also be referred to as a "cast type," etc.

[0024] Unicast transmission is characterized by (1) support for one PC5-RRC connection between a pair of UEs, (2) transmission and reception of control information and user traffic between UEs on the sidelink, (3) support for sidelink HARQ feedback, (4) transmit power control on the sidelink, (5) support for RLC AM, and (6) radio link failure detection for the PC5-RRC connection.

[0025] Groupcast transmission is characterized by (1) transmitting and receiving user traffic between UEs belonging to a sidelink group, and (2) supporting sidelink HARQ feedback.

[0026] Broadcast transmission is also characterized as (1) transmission and reception of user traffic between UEs on the sidelink.

[0027] 2 and 3 are diagrams illustrating an example of a protocol architecture for NR sidelink communication according to this embodiment. Note that the functions of each protocol described using FIG. 2 and / or FIG. 3 are only some of the functions closely related to this embodiment, and other functions may also be included. Note that in this embodiment, a sidelink (SL) may be a link between terminal devices.

[0028] Figure 2(A) is a diagram of a protocol stack of a control plane (CP) for an SCCH using RRC configured on a PC5 interface. As shown in Figure 2(A), the control plane protocol stack for an SCCH using RRC may be composed of a PHY (Physical layer) 200, which is a radio physical layer, a MAC (Medium Access Control) 202, which is a medium access control layer, a RLC (Radio Link Control) 204, which is a radio link control layer, a PDCP (Packet Data Convergence Protocol) 206, which is a packet data convergence protocol layer, and an RRC (Radio Resource Control) 208, which is a radio resource control layer. Figure 2(B) is a diagram of a protocol stack of a control plane for an SCCH using PC5-S configured on a PC5 interface. As shown in FIG. 2(B), the control plane protocol stack for SCCH using PC5-S may be composed of PHY (Physical layer) 200, which is a wireless physical layer, MAC (Medium Access Control) 202, which is a medium access control layer, RLC (Radio Link Control) 204, which is a radio link control layer, PDCP (Packet Data Convergence Protocol) 206, which is a packet data convergence protocol layer, and PC5-S (PC5 Signalling) 210, which is a PC5 signaling layer.

[0029] Figure 3(A) is a diagram of a protocol stack of a control plane for SBCCH configured on a PC5 interface. As shown in Figure 3(A), the control plane protocol stack for SBCCH may be configured with a PHY (Physical layer) 200, which is a radio physical layer, a MAC (Medium Access Control) 202, which is a medium access control layer, a RLC (Radio Link Control) 204, which is a radio link control layer, and an RRC (Radio Resource Control) 208, which is a radio resource control layer. Figure 3(B) is a diagram of a protocol stack of a user plane (UP) for STCH configured on a PC5 interface. As shown in FIG. 3(B), the user plane protocol stack for the STCH may be composed of a PHY (Physical layer) 200, which is a radio physical layer, a MAC (Medium Access Control) 202, which is a medium access control layer, a RLC (Radio Link Control) 204, which is a radio link control layer, a PDCP (Packet Data Convergence Protocol) 206, which is a packet data convergence protocol layer, and an SDAP (Service Data Adaptation Protocol) 310, which is a service data adaptation protocol layer.

[0030] The AS (Access Stratum) layer may be a layer including some or all of the PHY 200, MAC 202, RLC 204, PDCP 206, SDAP 310, and RRC 208. The PC5-S 210 and Discovery 400 described later may be layers higher than the AS layer.

[0031] In this embodiment, the terms PHY (PHY layer), MAC (MAC layer), RLC (RLC layer), PDCP (PDCP layer), SDAP (SDAP layer), RRC (RRC layer), and PC5-S (PC5-S layer) may be used. In this case, PHY (PHY layer), MAC (MAC layer), RLC (RLC layer), PDCP (PDCP layer), SDAP (SDAP layer), RRC (RRC layer), and PC5-S (PC5-S layer) may respectively refer to the PHY (PHY layer), MAC (MAC layer), RLC (RLC layer), PDCP (PDCP layer), SDAP (SDAP layer), RRC (RRC layer), and PC5-S (PC5-S layer) of the NR sidelink protocol. Note that when sidelink communication is performed using E-UTRA technology, the SDAP layer may not be required. To clarify that it is a protocol for sidelink, for example, RLC may be expressed as sidelink RLC, SL RLC, PC5 RLC, etc., and other protocols may also be expressed as protocols for sidelink by adding "sidelink," "SL," or "PC5" to the beginning.

[0032] In addition, in this embodiment, when distinguishing between E-UTRA protocols and NR protocols, PHY, MAC, RLC, PDCP, and RRC may be referred to as E-UTRA PHY or LTE PHY, E-UTRA MAC or LTE MAC, E-UTRA RLC or LTE RLC, E-UTRA PDCP or LTE PDCP, and E-UTRA RRC or LTE RRC, respectively. Furthermore, PHY, MAC, RLC, PDCP, and RRC may be referred to as E-UTRA PHY or LTE PHY, E-UTRA MAC or LTE MAC, E-UTRA RLC or LTE RLC, E-UTRA PDCP or LTE PDCP, and E-UTRA RRC or LTE RRC, respectively. Furthermore, when distinguishing between E-UTRA protocols and NR protocols, PHY, MAC, RLC, PDCP, and RRC may be referred to as NR PHY, NR MAC, NR RLC, NR PDCP, and NR RRC, respectively. PHY, MAC, RLC, PDCP, and RRC may also be referred to as NR PHY, NR MAC, NR RLC, NR PDCP, and NR RRC, respectively.

[0033] This section describes entities in the AS layer of E-UTRA and / or NR. An entity having some or all of the physical layer functions may be referred to as a PHY entity. An entity having some or all of the MAC layer functions may be referred to as a MAC entity. An entity having some or all of the RLC layer functions may be referred to as an RLC entity. An entity having some or all of the PDCP layer functions may be referred to as a PDCP entity. An entity having some or all of the SDAP layer functions may be referred to as an SDAP entity. An entity having some or all of the RRC layer functions may be referred to as an RRC entity. The PHY entity, MAC entity, RLC entity, PDCP entity, SDAP entity, and RRC entity may be referred to as PHY, MAC, RLC, PDCP, SDAP, and RRC, respectively.

[0034] Note that data provided from MAC, RLC, PDCP, and SDAP to lower layers, and / or data provided from lower layers to MAC, RLC, PDCP, and SDAP, may be referred to as MAC PDU (Protocol Data Unit), RLC PDU, PDCP PDU, and SDAP PDU, respectively. Data provided from higher layers to MAC, RLC, PDCP, and SDAP, and / or data provided from MAC, RLC, PDCP, and SDAP to higher layers, may be referred to as MAC SDU (Service Data Unit), RLC SDU, PDCP SDU, and SDAP SDU, respectively. A segmented RLC SDU may be referred to as an RLC SDU segment.

[0035] Here, the base station apparatus and the terminal apparatus exchange (transmit and receive) signals in a higher layer on the Uu interface. The higher layer may be referred to as the upper layer, and the terms may be interchangeable. For example, the base station apparatus and the terminal apparatus may transmit and receive RRC messages (also referred to as RRC signaling) in a Radio Resource Control (RRC) layer. The base station apparatus and the terminal apparatus may also transmit and receive MAC Control Elements (MAC CEs) in a Medium Access Control (MAC) layer. The RRC layer of the terminal apparatus acquires system information broadcast from the base station apparatus. Here, the RRC messages, system information, and / or MAC control elements are also referred to as higher layer signals (higher layer signaling) or higher layer parameters (higher layer parameters). Each of the parameters included in the higher layer signals received by the terminal apparatus may be referred to as a higher layer parameter. For example, in PHY layer processing, an upper layer means a layer higher than the PHY layer, and therefore may mean one or more of a MAC layer, an RRC layer, an RLC layer, a PDCP layer, an NAS (Non Access Stratum) layer, etc. For example, in MAC layer processing, an upper layer may mean one or more of an RRC layer, an RLC layer, a PDCP layer, an NAS layer, etc.

[0036] Furthermore, terminal devices also exchange (transmit and receive) signals in higher layers on the PC5 interface. Terminal devices may transmit and receive RRC messages (also referred to as RRC signaling) in the Radio Resource Control (RRC) layer. Terminal devices may also transmit and receive MAC Control Elements (MAC CEs) in the Medium Access Control (MAC) layer. Here, RRC messages and / or MAC control elements are also referred to as higher layer signals (higher layer signaling) or higher layer parameters (higher layer parameters). Each of the parameters included in higher layer signals received by a terminal device may be referred to as a higher layer parameter. For example, in PHY layer processing, the higher layer refers to a layer higher than the PHY layer, and may therefore refer to one or more of the MAC layer, RRC layer, RLC layer, PDCP layer, PC5-S layer, Discovery layer, etc. For example, in MAC layer processing, the upper layer may refer to one or more of the RRC layer, RLC layer, PDCP layer, PC5-S layer, Discovery layer, etc.

[0037] Hereinafter, the meaning of "A is given (provided) by an upper layer" or "A is given (provided) by an upper layer" may mean that an upper layer (mainly an RRC layer, a MAC layer, etc.) of a terminal device receives A from a base station device or another terminal device, and the received A is given (provided) to a physical layer of the terminal device from the upper layer of the terminal device. For example, in a terminal device, "being provided with an upper layer parameter" may mean receiving an upper layer signal from a base station device or another terminal device, and providing an upper layer parameter included in the received upper layer signal from the upper layer of the terminal device to the physical layer of the terminal device. Setting an upper layer parameter in a terminal device may mean that the upper layer parameter is given (provided) to the terminal device. For example, setting an upper layer parameter in a terminal device may mean that the terminal device receives an upper layer signal from a base station device or another terminal device, and setting the received upper layer parameter in the upper layer. However, setting an upper layer parameter in a terminal device may also include setting a default parameter that is given in advance to an upper layer of the terminal device. When describing transmission of an RRC message from a terminal device to a base station device or another terminal device, the expression "submitting a message from the RRC entity of the terminal device to a lower layer" may be used. In the terminal device, "submitting a message to a lower layer" from the RRC entity may mean submitting a message to the PDCP layer. In the terminal device, "submitting a message to a lower layer" from the RRC layer may mean submitting to a PDCP entity corresponding to each SRB, since RRC messages are transmitted using SRBs (SRB0, SRB1, SRB2, SRB3, etc.). When the RRC entity of the terminal device receives an indication from a lower layer, the lower layer may mean one or more of the PHY layer, MAC layer, RLC layer, PDCP layer, etc.

[0038] An example of the function of the PHY will be described. The PHY of a terminal device may have a function of transmitting and receiving data transmitted via a sidelink (SL) physical channel with the PHY of another terminal device. The PHY may be connected to a higher MAC via a transport channel. The PHY may pass data to the MAC via the transport channel. The PHY may also receive data from the MAC via the transport channel. In the PHY, a Radio Network Temporary Identifier (RNTI) may be used to identify various control information.

[0039] Here, the physical channels will be described. The physical channels used for wireless communication between a terminal device and another terminal device may include the following physical channels.

[0040] PSBCH (Physical Sidelink Broadcast CHannel) PSCCH (Physical Sidelink Control CHannel) PSSCH (Physical Sidelink Shared Channel) PSFCH (Physical Sidelink Feedback CHannel)

[0041] The PSBCH may be used to broadcast system information required by the terminal device.

[0042] The PSCCH may be used to indicate resources and other transmission parameters for the PSSCH.

[0043] The PSSCH may be used to transmit data and control information related to HARQ / CSI feedback to other terminal devices.

[0044] The PSFCH may be used to carry HARQ feedback to other terminal devices.

[0045] An example of the MAC function will be described. The MAC may be referred to as a MAC sublayer. The MAC may have the function of mapping various logical channels to corresponding transport channels. A logical channel may be identified by a logical channel identity (or logical channel ID). The MAC may be connected to the higher-level RLC via a logical channel. Depending on the type of information to be transmitted, the logical channel may be divided into a control channel for transmitting control information and a traffic channel for transmitting user information. The MAC may have the function of multiplexing MAC SDUs belonging to one or more different logical channels and providing them to the PHY. The MAC may also have the function of demultiplexing MAC PDUs provided by the PHY and providing them to the higher layer via the logical channel to which each MAC SDU belongs. The MAC may also have the function of performing error correction through HARQ (Hybrid Automatic Repeat reQuest). The MAC may also have the function of reporting scheduling information. The MAC may have the function of prioritizing between terminal devices using dynamic scheduling. The MAC may also have the function of prioritizing between logical channels within one terminal device. The MAC may have the function of prioritizing overlapping resources within one terminal device. The E-UTRA MAC may have the function of identifying Multimedia Broadcast Multicast Services (MBMS). The NR MAC may have the function of identifying Multicast / Broadcast Services (MBS). The MAC may have the function of selecting a transport format.The MAC may have functions such as discontinuous reception (DRX) and / or discontinuous transmission (DTX), a random access (RA) procedure, a power headroom report (PHR) function that notifies information about available transmission power, and a buffer status report (BSR) function that notifies information about the amount of data in the transmission buffer. The NR MAC may have a bandwidth adaptation (BA) function. The MAC PDU format used in the E-UTRA MAC may differ from that used in the NR MAC. The MAC PDU may also include a MAC control element (MAC CE), which is an element for controlling the MAC.

[0046] In addition, the MAC sublayer may provide additional services and functions over the PC5 interface, such as radio resource selection for selecting radio resources for sidelink transmission, filtering of packets received in sidelink communication, priority processing between uplink and sidelink, and reporting of sidelink channel state information (Sidelink CSI).

[0047] This section describes the sidelink (SL) logical channels used in E-UTRA and / or NR, and the mapping between the sidelink logical channels and transport channels.

[0048] The SBCCH (Sidelink Broadcast Control Channel) may be a logical channel for sidelink broadcasting sidelink system information from one terminal device to one or more terminal devices, and may be mapped to the SL-BCH, which is a sidelink transport channel.

[0049] The SCCH (Sidelink Control Channel) may be a sidelink logical channel for transmitting control information such as a PC5-RRC message or a PC5-S message from one terminal device to one or more terminal devices. The SCCH may also be mapped to the SL-SCH, which is a sidelink transport channel.

[0050] The STCH (Sidelink Traffic Control Channel) may be a sidelink logical channel for transmitting user information from one terminal device to one or more terminal devices, and may be mapped to the SL-SCH, which is a sidelink transport channel.

[0051] An example of the RLC function will be described. The RLC may also be called an RLC sublayer. The E-UTRA RLC may have the function of segmenting and / or concatenating data provided by the PDCP in the upper layer and providing it to the lower layer. The E-UTRA RLC may have the function of reassembling and reordering data provided by the lower layer and providing it to the upper layer. The NR RLC may have the function of adding a sequence number independent of the sequence number added by PDCP to data provided by the PDCP in the upper layer. The NR RLC may also have the function of segmenting data provided by PDCP and providing it to the lower layer. The NR RLC may also have the function of reassembling data provided by the lower layer and providing it to the upper layer. The RLC may also have the function of data retransmission and / or retransmission request (Automatic Repeat reQuest: ARQ). RLC may also have the function of performing error correction using ARQ. The control information sent from the receiving side of RLC to the transmitting side to indicate data that needs to be retransmitted in order to perform ARQ may be called a status report. The status report transmission instruction sent from the transmitting side of RLC to the receiving side may be called a poll. RLC may also have the function of detecting data duplication. RLC may also have the function of discarding data. RLC may have three modes: transparent mode (TM), unacknowledged mode (UM), and acknowledged mode (AM). In TM, data received from the upper layer is not segmented, and an RLC header does not need to be added. The TM RLC entity is a unidirectional entity and may be configured as a transmitting TM RLC entity or a receiving TM RLC entity.In UM, the UM RLC entity performs functions such as segmenting and / or concatenating data received from a higher layer and adding an RLC header, but does not require data retransmission control. The UM RLC entity may be a unidirectional or bidirectional entity. If the UM RLC entity is a unidirectional entity, it may be configured as a transmitting UM RLC entity or a receiving UM RLC entity. If the UM RLC entity is a bidirectional entity, the UM RRC entity may be configured as a UM RLC entity consisting of a transmitting side and a receiving side. In AM, the UM RLC entity may perform functions such as segmenting and / or concatenating data received from a higher layer, adding an RLC header, and controlling data retransmission. The AM RLC entity is a bidirectional entity and may be configured as an AM RLC consisting of a transmitting side and a receiving side. Note that data provided to a lower layer in TM and / or data provided from a lower layer may be referred to as a TMD PDU. Data provided to a lower layer in UM and / or data provided from a lower layer may be referred to as a UMD PDU. Furthermore, data provided to or from a lower layer in AM may be referred to as an AMD PDU. The RLC PDU format used in E-UTRA RLC may differ from the RLC PDU format used in NR RLC. RLC PDUs may include data RLC PDUs and control RLC PDUs. Data RLC PDUs may be referred to as RLC DATA PDUs (RLC Data PDUs). Control RLC PDUs may be referred to as RLC CONTROL PDUs (RLC Control PDUs).

[0052] In the sidelink, TM may be used for SBCCH, only UM is used for groupcast and broadcast transmission, and UM and AM are available for unicast transmission. In the sidelink, UM for groupcast and broadcast transmission supports only unidirectional transmission.

[0053] An example of PDCP functionality is described below. PDCP may be called a PDCP sublayer. PDCP may have a function for maintaining sequence numbers. PDCP may also have a header compression / decompression function for efficiently transmitting user data such as IP packets and Ethernet frames over wireless interfaces. The protocol used for IP packet header compression / decompression may be called the ROHC (Robust Header Compression) protocol. The protocol used for Ethernet frame header compression / decompression may be called the EHC (Ethernet (registered trademark) Header Compression) protocol. PDCP may also have a data encryption / decryption function. PDCP may also have data integrity protection / verification functions. PDCP may also have a reordering function. PDCP may also have a PDCP SDU retransmission function. PDCP may also have a data discard function using a discard timer. PDCP may also have a duplication function. PDCP may also have a function for discarding duplicately received data. The PDCP entity is a bidirectional entity and may consist of a transmitting PDCP entity and a receiving PDCP entity. The PDCP PDU format used in E-UTRA PDCP may differ from that used in NR PDCP. PDCP PDUs may include data PDCP PDUs and control PDCP PDUs. The data PDCP PDU may be called a PDCP DATA PDU (PDCP Data PDU). The control PDCP PDU may be called a PDCP CONTROL PDU (PDCP Control PDU).

[0054] In addition, the following restrictions apply to PDCP functions and services in Sidelink: (1) Out-of-order delivery may only be supported with unicast transmission. (2) Duplication over the PC5 interface is not supported.

[0055] An example of SDAP functionality will be described. SDAP is a service data adaptation protocol layer. In the sidelink, the SDAP may perform mapping between sidelink QoS flows transmitted from a terminal device to another terminal device and sidelink data radio bearers (DRBs). The SDAP may also store mapping rule information. The SDAP may also perform QoS flow ID (QFI) marking. SDAP PDUs may include data SDAP PDUs and control SDAP PDUs. The data SDAP PDU may be called SDAP DATA PDU (SDAP Data PDU). The control SDAP PDU may be called SDAP CONTROL PDU (SDAP Control PDU). In the sidelink, a terminal device may have one SDAP entity for each destination for unicast transmission, groupcast transmission, or broadcast transmission associated with the destination. Also, reflective QoS is not supported on PC5 interfaces.

[0056] An example of RRC functionality will be described. RRC may support services and functions such as the transfer of PC5-RRC messages between peer UEs over the PC5 interface, the maintenance and release of PC5-RRC connections between two UEs, and the detection of sidelink radio link failures for PC5-RRC connections. A PC5-RRC connection is a logical connection between two UEs corresponding to a pair of source L2ID and destination L2ID, and is considered established after the corresponding PC5 unicast link is established. A PC5-RRC connection and a PC5 unicast link have a one-to-one correspondence. A UE may have multiple PC5-RRC connections with one or more UEs for different pairs of source L2ID and destination L2ID. Separate PC5-RRC procedures and messages may be used by a UE to transfer UE capabilities and sidelink configurations to a peer UE. Both peer UEs may exchange their UE capabilities and sidelink configurations with each other using separate bidirectional procedures. The UE releases the PC5-RRC connection if it is not interested in sidelink transmission, if a sidelink radio link failure is detected for the PC5-RRC connection, and if the Layer 2 link release procedure is completed.

[0057] A UE performing sidelink transmission may transmit a PSCCH and a PSSCH in association with each other. Note that sidelink transmission may involve transmitting a signal and / or data (message) via a sidelink physical channel (e.g., PSBCH, PSSCH, PSCCH), and sidelink reception may involve receiving a signal and / or data (message) via a sidelink physical channel. Communication using sidelink transmission and sidelink reception may also be referred to as sidelink communication. A UE may recognize the data (message) based on the signal. Each PSSCH transmission may be associated with a PSCCH (a PSCCH) transmission. A PSCCH transmission may carry a first SCI (first stage of the SCI) associated with the PSSCH transmission, and a second SCI (second stage of the SCI) may be carried within the resources of the PSSCH (the PSSCH). Note that a PSCCH transmission may include the first SCI, and a PSSCH transmission may include the second SCI. Furthermore, PSCCH transmission and PSSCH transmission may be referred to as sidelink transmission, and SCI may be sidelink control information. The first SCI may include information in a format called SCI format 1-A and may be used for scheduling the PSSCH and the second SCI on the PSSCH. SCI format 1-A may include information such as data priority, frequency and time resources on which the PSSCH is transmitted, resource reservation period, DMRS allocation pattern, second SCI format, beta offset indication value, number of DMRS ports, information indicating modulation and coding scheme, and other information. Furthermore, the SCI carried on the PSSCH may be the second SCI, and the second SCI may transport sidelink scheduling information and / or information related to inter-UE coordination. The second SCI may contain information in a format referred to as SCI Format 2-A, SCI Format 2-B, or SCI Format 2-C, etc.SCI Format 2-A, SCI Format 2-B, and SCI Format 2-C may include information such as HARQ process-related information, information indicating whether data is new, a redundancy version, a source ID identifying a source UE, a destination ID identifying a destination UE, and information indicating whether HARQ feedback is possible. SCI Format 2-A may additionally include information indicating a cast type and information indicating whether channel state information (CSI) is requested. SCI Format 2-B may additionally include a zone identifier and request information regarding communication range. SCI Format 2-C may additionally include information indicating whether channel state information is requested and information indicating whether inter-UE coordination information is provided or requested. When SCI Format 2-C includes information for providing inter-UE coordination information, SCI Format 2-C may additionally include information indicating a resource combination, information indicating the position of the first resource, position information of the reference slot, information indicating the type of resource set, a lowest subchannel index, and the like. When SCI format 2-C includes information requesting inter-UE coordination information, SCI format 2-C may additionally include information indicating priority, the number of subchannels, the resource reservation interval, the position of a resource selection window, the type of resource set, etc. Note that each SCI format may include information other than the above-mentioned information.

[0058] Next, the procedure for a UE to receive a PSSCH will be described. When a UE detects SCI format 1-A on a PSCCH, it can decode the PSSCH according to the detected SCI format 2-A or SCI format 2-B and the associated PSSCH resource configuration configured by a higher layer. Note that the UE does not need to decode more than one PSCCH for each PSCCH resource candidate. Also, if the UE does not support the modulation and coding scheme indicated in SCI format 1-A, it does not need to decode the corresponding SCI format 2-A or SCI format 2-B, or the PSSCH associated with SCI format 1-A.

[0059] Furthermore, if PSSCH is set in a parameter indicating whether the DMRS used for L1 RSRP measurement during a sensing operation is the DMRS of the PSCCH or the DMRS of the PSSCH in the higher (RRC) layer, the UE may measure the PSSCH RSRP from the DMRS resource elements for the PSSCH associated with the received SCI format 1-A, and if PSCCH is set, the UE may measure the PSCCH RSRP from the DMRS resource elements for the PSCCH associated with the received SCI format 1-A.

[0060] A terminal device capable of sidelink communication may perform discovery. Discovery may be performed in Model A or Model B. Figure 4 shows the protocol stack for the discovery procedure. Model A may use a single discovery protocol message, while Model B may use two discovery protocol messages. The single discovery protocol message in Model A may be an Announcement message, while the discovery protocol messages in Model B may be a Solicitation message and a Response message. Note that the Announcement message, Solicitation message, and Response message may be collectively referred to as a Discovery message, and messages with other names used in the discovery procedure may also be referred to as Discovery messages. An overview of the procedures for Model A and Model B in ProSe Direct Discovery is provided below.

[0061] In Model A, a UE that sends an announce message may be referred to as an announcing UE, and a UE that monitors the announce message may be referred to as a monitoring UE. The announce message may include information such as the discovery message type, ProSe Application Code or ProSe Restricted Code, and security protection element, and may also include metadata information. The announce message is transmitted using a destination Layer-2 ID (L2ID) and a source Layer-2 ID (L2ID), and the monitoring UE determines the destination L2ID to receive the announce message. Note that the destination L2ID may be the Layer-2 identifier of the destination UE, and the source L2ID may be the Layer-2 identifier of the source UE.

[0062] In Model B, a UE that sends an INVITE message may be referred to as a discoverer UE, and a UE that receives the INVITE message and / or sends a response message to the discoverer UE may be referred to as a discoveree UE. The INVITE message may include information such as a discovery message type, a ProSe Query Code, and a security protection element. The INVITE message is sent using a destination L2 ID and a source L2 ID, and the discoveree UE determines the destination L2 ID to receive the INVITE message. The discoveree UE responding to the INVITE message sends a response message. The response message may include information such as a discovery message type, a ProSe Response Code, and a security protection element, and may also include metadata information. The response message is sent using a source L2 ID, and the destination L2 ID is set to the source L2 ID of the received INVITE message.

[0063] Discovery may include types other than ProSe Direct Discovery, which discovers other UEs for direct communication with them, such as Group Member Discovery, which discovers one or more UEs for intragroup communication using a sidelink, and 5G ProSe UE-to-Network Relay Discovery, which discovers candidate relay UEs for connecting to a network via a relay UE. Note that the above-described discovery is an example of discovery provided by an application called ProSe, but other than the above-described types, different types of discovery may exist depending on the application or service performing sidelink communication. Furthermore, the information included in the discovery protocol message may differ depending on the type of discovery, and additional messages may be sent to transmit additional information.

[0064] 4 is a diagram showing an example of a protocol configuration including a discovery protocol according to this embodiment. As shown in FIG. 4, a discovery plane protocol stack including the discovery protocol may be composed of a PHY (Physical layer) 200, which is a wireless physical layer, a MAC (Medium Access Control) 202, which is a medium access control layer, a Radio Link Control (RLC) 204, which is a radio link control layer, a PDCP (Packet Data Convergence Protocol) 206, which is a packet data convergence protocol layer, and a Discovery 400, which is a discovery protocol layer. Discovery 400 may be a protocol used to process discovery-related procedures. The interface between UEs performing discovery may be referred to as PC5-D.

[0065] Multiple resource pools for transmitting messages (discovery messages) in the discovery procedure may be configured, or one or more resource pools may be configured exclusively for discovery. If a resource pool dedicated to discovery is configured, the UE may use the resource pool dedicated to discovery as the resource pool for transmitting discovery messages. If a resource pool dedicated to discovery is not configured, the UE may use the resource pool for sidelink communication as the resource pool for transmitting discovery messages. Note that multiple resource pools for sidelink communication and multiple resource pools dedicated to discovery may be configured simultaneously. Each resource pool may be configured by UE-dedicated signaling or may be configured in advance.

[0066] A Direct Communication Request (DCR) message is also described. The Direct Communication Request message may be a message used to establish a unicast link. The DCR message may include at least a source UE identifier, and if the target UE identifier is provided by the application layer, may also include a target UE identifier. It may also include other information, such as security information and application information. The DCR message may be transmitted by unicast or broadcast using a source L2 ID and a destination L2 ID. The discovery message and the DCR message may be transmitted via sidelink.

[0067] A sidelink signaling radio bearer (SRB) may be configured for each unicast PC5-RRC connection. A sidelink SRB used to transmit PC5-S messages before PC5-S security is established may be referred to as SL-SRB0. A sidelink SRB used to transmit PC5-S messages for establishing PC5-S security may be referred to as SL-SRB1. A sidelink SRB used to transmit protected PC5-S messages after PC5-S security is established may be referred to as SL-SRB2. A sidelink SRB used to transmit protected PC5-RRC signaling after PC5-S security is established may be referred to as SL-SRB3. A sidelink SRB used to transmit and / or receive discovery messages in NR may be referred to as SL-SRB4. Note that PC5-RRC signaling may be RRC signaling between UEs transmitted over PC5. Note that PC5-RRC signaling may be referred to as a PC5-RRC message, etc.

[0068] UE-to-UE relay may refer to a technology in which a source UE communicates with a destination UE via sidelink communication with a relay UE. The relay UE may have the function and / or role of forwarding (or relaying) data received from the source UE for the destination UE to the destination UE. The source UE, destination UE, and relay UE may be called by different names. For example, the source UE and destination UE may be called remote UE or U2U Remote UE, and the relay UE may be called U2U relay UE. The term UE-to-UE relay may also be referred to as U2U relay.

[0069] 6 and 7 show examples of a control plane (CP) and user plane (UP) protocol stack in a Layer 2 (L2) UE-to-UE (U2U) relay. As shown in FIGS. 6 and 7, an SRAP 600 may be present. The SRAP 600 may be referred to as an SRAP layer (Sidelink Relay Adaptation Protocol layer), an SRAP layer, or the like, or a different name may be used. As shown in FIGS. 6 and 7, the PHY 200, MAC 202, RLC 204, and SRAP 600 may be associated between a remote UE and an L2 U2U relay UE, and between the L2 U2U relay UE and other remote UEs, respectively. Furthermore, the PDCP 206, RRC 208, and SDAP 310 may be associated between a remote UE and other remote UEs. As shown in FIG. 2, a PC5-S 210 may be used instead of the RRC 208 to control the PC5 connection between the remote UE and other remote UEs (not shown). In a protocol stack for Layer 3 (L3) UE-to-UE relay, the PHY 200, MAC 202, RLC 204, PDCP 206, RRC 208, and SDAP 210 may be associated between the remote UE and the U2U relay UE, and between the U2U relay UE and other remote UEs, respectively, and the SRAP 600 may not be configured (not shown). In the L3 U2U relay, a layer higher than the SDAP may have a function for transmitting data received over a Uu link over a PC5 link. The SRAP layer may be included in the AS layer.

[0070] Here, the SRAP will be described. The SRAP layer may include a SRAP sublayer. The SRAP sublayer may exist above the RLC sublayer for the control plane and user plane of the PC5 interface, and below the PDCP sublayer for the control plane and user plane of the PC5 interface. The SRAP sublayer on the PC5 may be used for bearer mapping. In an L2 U2U Relay UE, the SRAP sublayer may include one SRAP entity on the PC5 interface between the source UE and the relay UE, and a separate collocated SRAP entity on the PC5 interface between the relay UE and the destination UE. In an L2 U2U Remote UE, the SRAP sublayer may include only one SRAP entity on one PC5 interface. The SRAP entity associated between the Remote UE and the Relay UE via the PC5 interface may be specifically referred to as a PC5-SRAP. Each SRAP entity may have a transmitter and a receiver. On the PC5 interface, the transmitter of the SRAP entity of the L2 U2U Remote UE may be associated with the receiver of the SRAP entity of the L2 U2U Relay UE, and the receiver of the SRAP entity of the L2 U2U Remote UE may be associated with the transmitter of the SRAP entity of the L2 U2U Relay UE.

[0071] The SRAP entity may also have a function to forward data, a function to determine the UE ID field and the bearer ID field of the SRAP header to be added to the data packet, a function to determine the egress link, a function to determine the egress RLC channel, and other functions.

[0072] Furthermore, when a remote UE transmits sidelink data to another remote UE, the remote UE may be referred to as a source UE, and the other remote UE may be referred to as a destination UE. Similarly, in the reverse case, when another remote UE transmits sidelink data to a remote UE, the other remote UE may be referred to as a source UE, and the remote UE may be referred to as a destination UE. Note that the source UE may be referred to as a source remote UE, or simply as a remote UE, or these terms may be interchangeable. The destination UE may be referred to as a destination remote UE, or simply as a remote UE, or target UE, or these terms may be interchangeable. The source UE and the destination UE may be identified by different names, or may be referred to as a U2U source UE, a U2U destination UE, or the like to clarify that they are terminals performing U2U relay. Furthermore, to clarify that communication is performed via an L2 U2U relay, the UEs may be referred to as, for example, an L2 U2U source UE or an L2 U2U destination UE, and similarly, to clarify that communication is performed via an L3 U2U relay, the UEs may be referred to as, for example, an L3 U2U source UE or an L3 U2U destination UE. Not only when either a remote UE or another remote UE transmits sidelink data, but also when forming a U2U relay pair (a pair of one remote UE, one relay UE, and another remote UE), a UE that first transmits a discovery message other than the U2U relay UE may be referred to as a source UE, and a UE that is neither a source UE nor a U2U relay UE in the U2U relay may be referred to as a destination UE, or names such as source UE and destination UE may be used simply to distinguish between two remote UEs.

[0073] Furthermore, the UE may transmit a discovery message and / or a direct communication request message to perform U2U relay. For example, to select a relay UE for U2U relay, the source UE may transmit a discovery message or a direct communication request message. In this case, discovery may be Model B discovery. A UE (a relay UE candidate) that receives a discovery message or a direct communication request message transmitted from the source UE may transmit a discovery message or a direct communication request message to the destination UE. Furthermore, the UE (a relay UE candidate) may transmit a discovery message and / or a direct communication request message to the source UE. In this case, discovery may be Model A discovery.

[0074] In the sidelink, the reference signal received power (RSRP) measured by the UE may be, for example, the following RSRP: (a) PSBCH RSRP (b) PSSCH RSRP (c) PSCCH RSRP

[0075] The PSBCH-RSRP (PSBCH RSRP) may be defined as a linear average of power contributions of resource elements transmitting multiple Demodulation Reference Signals (DMRSs) associated with the PSBCH. Furthermore, the PSSCH-RSRP (PSSCH RSRP) may be defined as a linear average of power contributions of resource elements of antenna ports transmitting multiple DMRSs associated with the PSSCH. In the case of multiple antenna ports, the RSRP values ​​for each antenna port may be summed. The PSCCH-RSRP (PSCCH RSRP) may be defined as a linear average of power contributions of resource elements transmitting multiple DMRSs associated with the PSCCH. The DMRSs may be used to demodulate, for example, the PSBCH, PSSCH, and PSCCH signals. Furthermore, a terminal device performing sidelink communication with another terminal device may measure the RSRP (SL-RSRP) of the sidelink communication using the PSSCH or PSCCH transmitted from the other terminal device. The terminal device may also measure the RSRP (SD-RSRP) of the discovery message using, for example, the power contribution of the resource element transmitting the DMRS associated with the PSSCH carrying the discovery message.

[0076] In addition to the RSRP, the UE 122 may measure the following quantities in the sidelink measurements: (a) Sidelink received signal strength indicator (SL RSSI) (b) Sidelink channel occupancy ratio (SL CR) (c) Sidelink channel busy ratio (SL CBR)

[0077] The SL RSSI may be defined as the linear average of the power ([W]) observed on the configured subchannels in the OFDM symbols of the slots configured for the PSCCH and PSSCH, starting from the second OFDM symbol. The SL CR for slot n may be defined as the sum of the number of subchannels used for sidelink transmission from slot [na] to slot [n-1] and the number of subchannels allocated from slot [n] to slot [n+b], divided by the total number of subchannels configured from slot [na] to slot [n+b]. The SL CBR for slot n may be defined as the percentage of subchannels in the resource pool whose SL RSSI exceeds a threshold during a period configured as a CBR measurement window (slot [na] to slot [n-1]).

[0078] There are two resource allocation modes for NR sidelink communication: Mode 1, in which the UE performs sidelink transmission using resources scheduled by the base station, and Mode 2, in which the UE automatically selects resources for sidelink transmission. In Mode 1, the UE must be RRC_CONNECTED. In Mode 2, the UE can perform sidelink transmission regardless of the RRC state or whether it is inside or outside NG-RAN. In Mode 2, the UE automatically selects resources available for sidelink transmission from one or more resource pools configured before the sidelink transmission.

[0079] Based on the above description, various embodiments of the present invention will be described. Note that the above-described processes may be applied to processes that are omitted in the following description.

[0080] Fig. 5 is a block diagram showing the configuration of a terminal device (UE 122) in this embodiment. To avoid complicating the explanation, Fig. 5 shows only the main components closely related to this embodiment.

[0081] 5 includes a receiver 500 that receives control information (SCI, MAC control element, RRC signaling, etc.), discovery messages, information including user data, etc. from other terminal devices, a processor 502 that performs processing according to parameters included in the received control information, etc., and a transmitter 504 that transmits the control information (SCI, MAC control element, RRC signaling, etc.), discovery messages, information including user data, etc. to other terminal devices. In addition, the processor 502 may include some or all of the functions of various layers (e.g., a physical layer, a MAC layer, an RLC layer, a PDCP layer, a SRAP layer, an SDAP layer, an RRC layer, a PC5-S layer, a discovery layer, and an application layer). That is, the processing unit 502 may include some or all of a physical layer processing unit (PHY processing unit), a MAC layer processing unit (MAC processing unit), an RLC layer processing unit (RLC processing unit), a PDCP layer processing unit (PDCP processing unit), a SRAP layer processing unit (SRAP processing unit), an SDAP layer processing unit (SDAP processing unit), an RRC layer processing unit (RRC processing unit), a PC5-S layer processing unit (PC5-S processing unit), a Discovery layer processing unit (Discovery processing unit), and an application layer processing unit.

[0082] An example of an embodiment of the present invention will be described with reference to FIG.

[0083] When a UE 122 capable of sidelink communication receives a first message from a first terminal device in step S800, the UE 122 determines information to be transmitted to a second terminal device based on the first message received in step S802, and provides the information to the second terminal device in step S804.

[0084] In step S802, the information transmitted from UE 122 to the second terminal device may be, for example, the RSRP measured in the received first message, or may be, for example, an offset value determined based on the RSRP measured in the received first message. Additionally or alternatively, in step S802, the information transmitted from UE 122 to the second terminal device may be, for example, the RSRP (SL-RSRP) measured in sidelink communication when sidelink communication with the first terminal device is being performed, or may be, for example, an offset value determined based on the RSRP (SL-RSRP) measured in sidelink communication when sidelink communication with the first terminal device is being performed. Additionally or alternatively, in step S802, the information transmitted from UE 122 to the second terminal device may be, for example, the path loss measured in the received first message, or may be, for example, an offset value determined based on the pathloss measured in the received first message. In addition, even when sidelink communication is being performed with the first terminal device, SD-RSRP or path loss may be used instead of SL-RSRP.

[0085] In step S804, the UE 122 may provide the information to the second terminal device by transmitting a second message including the information to the second terminal device, for example. The information may be provided from the AS layer to a layer higher than the AS layer, and the layer higher than the AS layer may include the information in the second message and transmit the information to the second terminal device, or may be transmitted to the second terminal device as a MAC Control Element (MAC CE).

[0086] Furthermore, when the second terminal device receives the second message including the information from one or more terminal devices, the second terminal device may use the information and the RSRP of the received second message, or, if the second terminal device is in sidelink communication with the terminal device that transmitted the second message, the RSRP of the sidelink communication (SL-RSRP) or the path loss of the received second message to determine which terminal device to select as a relay terminal (Relay UE) in U2U relay to the first terminal device. For example, when the second terminal device receives a discovery message as the second message and is provided with an RSRP offset value as the information, the second terminal device may evaluate the RSRP of the received discovery message (SD-RSRP) taking into account the provided offset value.

[0087] Instead of passing the information to the second terminal device, the UE 122 may select a resource pool to transmit a discovery message to the second terminal device, for example, when transmitting a discovery message as a second message, based on the SD-RSRP, SL-RSRP, path loss, or offset value. For example, when using SD-RSRP, if the SD-RSRP is within a first range, the UE 122 may transmit the discovery message using a first resource pool, and if the SD-RSRP is within a second range, the UE 122 may transmit the discovery message using a second resource pool. Furthermore, if the UE 122 transmits a discovery message using a first resource pool and the second terminal device receives the discovery message from a resource pool corresponding to the first resource pool, the UE 122 may determine that the SD-RSRP is within the first range. Furthermore, the second terminal device may evaluate the RSRP of the received discovery message based on the determination to determine whether to select the UE 122 as a relay UE in U2U relay. Furthermore, similar processing may be applied when messages other than discovery messages are used as the first message and the second message.

[0088] FIG. 9 shows another example of the embodiment of the present invention.

[0089] When a UE 122 capable of sidelink communication receives a first message from a first terminal device in step S900, the UE 122 makes a decision based on the received first message in step S902, and operates based on the decision in step S904.

[0090] In step S902, the determination may be, for example, determining whether the RSRP of the received first message is better than a threshold. Additionally or alternatively, in step S902, the determination may be, for example, determining whether the path loss of the received first message is better than a threshold. Additionally or alternatively, in step S902, the determination may be, for example, determining whether the RSRP in the sidelink communication (SL-RSRP) is better than a threshold when sidelink communication is being performed with the first terminal device. Note that the RSRP being better than a threshold may mean that the RSRP is equal to or greater than a threshold, and the RSRP being worse than a threshold may mean that the RSRP is less than a threshold. Furthermore, the path loss being better than a threshold may mean that the path loss is equal to or less than a threshold, and the path loss being worse than a threshold may mean that the path loss is greater than a threshold. Furthermore, the SL-RSRP being better than a threshold may mean that the SL-RSRP is equal to or greater than a threshold, and the SL-RSRP being worse than a threshold may mean that the SL-RSRP is less than the threshold. Note that the determination of whether the SL-RSRP is equal to or greater than a threshold may be replaced with a determination of whether the SL-RSRP is greater than or less than a threshold. Furthermore, the above-mentioned determination of "whether the RSRP is better than a threshold" may be replaced with a determination of "whether the RSRP is in a first range" described below.

[0091] If it is determined in step S902 that the RSRP, the path loss, or the SL-RSRP is better than a threshold, then in step S904, for example, the action may be to transmit, to a second terminal device, a second message based on the received first message, and in addition or instead, for example, the action may be to forward the received first message to a higher layer (for example, a discovery layer). Also, if it is determined in step S902 that the RSRP, the path loss, or the SL-RSRP is worse than a threshold, then in step S904, for example, the action may be not to transmit, to a second terminal device, a second message based on the received first message, and in addition or instead, for example, the action may be not to forward the received first message to a higher layer (discovery layer).

[0092] Note that the threshold value used by UE 122 to determine whether the SD-RSRP, the path loss, or the SL-RSRP is good may be set by the network, may be set in advance in UE 122 as a default setting, or may be determined by the first terminal device and transmitted by signaling of a higher layer (such as an RRC or application layer), or may be transmitted together with a discovery message by being included in a MAC CE, etc. When the determined threshold value is transmitted in the application layer, the threshold value may be transmitted as information included in a discovery message.

[0093] In each embodiment, the first message and the second message may be a discovery message, a direct communication request message, or any other message used to select a relay terminal in a U2U relay. The contents of the first message and the second message may be different. For example, the second message may include an identifier of the UE 122 in addition to the contents of the first message. An appropriate RSRP may be measured depending on the type of the first message and the second message. For example, if the first message and the second message are discovery messages, the RSRP measured using the first message and the second message may be SD-RSRP.

[0094] Note that the discovery message in each embodiment may be a discovery message used for U2U relay. For example, a discovery message transmitted from a first terminal device may include information about the first terminal device and information about the second terminal device. Also, for example, a discovery message transmitted from a UE 122 may include information about the first terminal device, information about the UE 122, and information about the second terminal device. The information about the UE 122 and each terminal device may be an identifier for identifying each terminal, or other information may be included in addition to or instead of that. Also, the discovery message may include information about the type of the discovery message.

[0095] FIG. 10 shows another embodiment of the present invention.

[0096] The UE 122 capable of sidelink communication receives a signal from a first terminal device in step S1000, makes a decision based on the signal in step S1002, and takes action based on the decision in step S1004.

[0097] The signal may be a signal carrying a discovery message, a signal carrying a Direct Communication Request message, a signal carrying a message of another higher layer (such as an application layer or a discovery layer), or a signal carrying data to be transmitted in sidelink communication between the UE 122 and the first terminal device. The UE 122 may also measure Reference Signal Received Power (RSRP) based on the signal. Additionally or alternatively, the UE 122 may identify an identifier of the first terminal device from information such as an SCI included in the signal.

[0098] In step S1002, the determination may be, for example, identifying an identifier of a first terminal device that transmitted the signal based on the signal. In this case, in step S1004, the action may be, for example, storing the identifier in a first list. In addition to the identifier, for example, an RSRP measured by UE 122 based on the signal may be stored in the first list. The RSRP and the identifier may be stored as a set in the first list, or additional different information may be included in the set. In this case, for example, UE 122 may include the RSRP and the identifier in a first set and include the first set in the first list. The first list may include one or more sets. Note that the set may be referred to as an entry.

[0099] Furthermore, the first list may be managed by an AS layer or a non-AS layer (e.g., a discovery layer, an application layer, etc.). If the first list is managed by a non-AS layer, the AS layer may provide the set or information about the set to the non-AS layer.

[0100] As another example, in step S1002, the UE 122 may determine an identifier of a first terminal device that transmitted the signal, for example, based on the signal, and may also determine whether an RSRP measured using the signal is within a first range. In this case, in step S1004, the UE 122 may perform an action based on whether the RSRP is within the first range. For example, if it is determined in step S1002 that the RSRP is within the first range, the action in step S1004 may be, for example, storing the identifier in a first list. If it is determined in step S1002 that the RSRP is not within the first range, the action in step S1004 may be, for example, not storing the identifier in the first list. If the UE 122 stores the identifier in the first list, the UE 122 may also store the RSRP in the first list. If the RSRP is stored in the first list, the RSRP and the identifier may be stored as a set in the first list, or additional different information may be included in the set. Furthermore, when UE 122 determines that the RSRP is not within a first range and determines that a first set including the identifier is included in the first list, UE 122 may delete the first set. The set may be referred to as an entry. The term "being within the first range" may mean that the RSRP is greater than Threshold 1, or that the RSRP is greater than Threshold 1 and less than Threshold 2, or that the RSRP is less than Threshold 2. The terms "greater than" and "smaller than" may be replaced with terms such as "greater than or equal to" and "less than or equal to."

[0101] As another example of the operation in step S1004, if it is determined in step S1002 that the RSRP is within the first range, the operation in step S1004 may be, for example, reporting the identifier to a higher layer, or in addition or instead notifying a higher layer (such as an application layer) that the RSRP is within the first range or similar information. If it is determined in step S1002 that the RSRP is not within the first range, the operation in step S1004 may be, for example, not reporting the identifier to a higher layer, or in addition or instead notifying a higher layer (such as an application layer) that the RSRP is not within the first range. "Notifying B that it is A" may be replaced with "not notifying B that it is not A," and "notifying B that it is not A" may be replaced with "not notifying B that it is A."

[0102] The sets stored in the first list may also be managed by time. For example, the UE 122 may start a first timer when storing the set in the first list, or may start the first timer when measuring RSRP associated with the set. When the first timer expires, the UE 122 may delete the set from the first list. If a second set having the same identifier as an identifier included in the first set is stored in the first list before the first timer expires, the UE 122 may delete the first set from the first list, or may update information other than the identifier in the first set based on the second set, restart the first timer, and not store the second set in the first list. A timer may be associated with each set, and multiple timers may operate. The timer value may be set by the base station, based on the signal, or a default value or a preset value may be used. The sets may also be managed by methods other than time. For example, the UE 122 may delete all sets included in the first list if it is no longer interested in U2U relay. A timer may be stopped and / or deleted if the set with which it is associated is deleted.

[0103] FIG. 11 shows another embodiment of the present invention.

[0104] The UE 122 capable of sidelink communication performs an information determination in step S1100 and acts based on the determination in step S1102.

[0105] In step S1100, determining the information may be, for example, determining whether a first identifier is included in a first list. For example, in Model A discovery, when a target UE (destination UE) notifies a source UE that it is close to UE 122, the first identifier may be the identifier of the target UE. For example, in Model B discovery, the first identifier may be the identifier of the destination UE indicated in a discovery message received by UE 122. For example, when UE 122 receives a DCR message from a source UE, the first identifier may be the identifier of the target UE indicated in the DCR message. Additionally or alternatively, determining the information in step S1100 may be, for example, determining whether an RSRP corresponding to the first identifier is within a first range. The RSRP corresponding to the first identifier may be an RSRP stored in a set that includes the first identifier, among one or more sets stored in the first list. Note that if the first identifier is not included in the first list, it is not necessary to determine whether the RSRP is within the first range. The RSRP being within the first range may mean that the RSRP is greater than Threshold 1, or greater than Threshold 1 and less than Threshold 2, or less than Threshold 2. The conditions "greater than" and "smaller than" may be replaced with conditions such as "greater than" and "less than." The first list may be the list described above with reference to FIG. 10. Threshold 1 and Threshold 2 may be set by a base station, default values ​​may be set, preset values ​​may be used, or they may be set by some other method.

[0106] If it is determined in step S1100 that the first identifier is included in the first list and / or the RSRP is included in the first range, the action in step S1102 may be to transmit a first message. Alternatively, if it is determined that the first identifier is not included in the first list or the RSRP is not included in the first range, the action in step S1102 may be not to transmit the first message. Note that the first message may be, for example, a discovery message that notifies a source UE that a target UE (destination UE) is close to UE 122 in Model A discovery, or may be, for example, a discovery message that UE 122 transmits to a destination UE based at least on receiving a discovery message from UE 122 in Model B discovery. For example, if UE 122 receives a DCR message from a source UE, it may be a DCR message that UE 122 transmits to a destination UE based at least on receiving the DCR message.

[0107] Furthermore, in Model A discovery, UE 122 may transmit the first list to a source UE by including it in a discovery message. In this case, UE 122 may transmit all sets included in the first list as a list, or may transmit some sets included in the first list as a list. Note that UE 122 may transmit the first list by including it in a message of a higher layer (such as a discovery layer or an application layer), or may transmit the first list in the form of a MAC CE or the like.

[0108] In each embodiment, the sets included in the first list may be sorted within the list. For example, the sets may be sorted in order of the size of the RSRPs included in the sets, in chronological order, or according to other rules (taking into account cell IDs, PLMN IDs, etc.). When storing RSRPs in the first list, the UE 122 may store the RSRPs in the list as measured values, or may store them as information other than measured values. When transmitting the first list, the UE 122 may transmit the RSRPs as measured values, or may transmit them as information other than measured values. The information other than measured values ​​may be, for example, an offset value determined based on the RSRPs, information indicating the range of the RSRPs, or other information. In each embodiment, the RSRP may be SD-RSRP, SL-RSRP, path loss, or may be replaced with other measured values.

[0109] In each embodiment, the UE 122 may recognize that it has received data addressed to a dedicated logical channel ID (LCID), that it has received a DCR message through a notification from an upper layer (application layer), or may recognize the reception based on other methods. The RSRP measured by the UE 122 upon receiving the DCR message may be SL-RSRP, SD-RSRP, or may be called by other names. In the above description, the term "store" may be interchangeable with terms such as "add" and "include." The terms "source UE" and "destination UE" used in each embodiment may be interchangeable with each other, or may be other names.

[0110] In each embodiment, the first terminal device, the second terminal device, and the other multiple terminal devices may be terminal devices capable of sidelink communication, similar to UE122, and may have a configuration including a receiving unit, a processing unit, and a transmitting unit.

[0111] When relay UE selection in UE-to-UE relay is performed using the operations described in Non-Patent Documents 1, 5, and 6, the UE can only evaluate the link quality with the UE to which it is directly connected. However, according to each embodiment, the UE can evaluate the relay path including not only the link quality between itself and the relay UE, but also the link quality between the relay UE and other UEs, and select a more suitable relay UE.

[0112] In the above description, expressions such as "notified" and "indicated" may be interchangeable.

[0113] In the above description, expressions such as "link," "associate," and "link" may be interchangeable.

[0114] In addition, in the above description, expressions such as "included," "included," and "was included" may be used interchangeably.

[0115] In the above description, "the above-mentioned" may be replaced with "the above-mentioned."

[0116] In the above description, expressions such as "confirmed to be...", "is set to...", and "includes..." may be interchangeable.

[0117] Furthermore, in each example of processing or each example of processing flow in the above description, some or all of the steps may not be executed. Furthermore, in each example of processing or each example of processing flow in the above description, the order of the steps may be different. Furthermore, in each example of processing or each example of processing flow in the above description, some or all of the processing within each step may not be executed. Furthermore, in each example of processing or each example of processing flow in the above description, the order of the processing within each step may be different. Furthermore, in the above description, "doing B based on A being true" may be rephrased as "doing B." In other words, "doing B" may be executed independently of "A being true."

[0118] In the above explanation, "A may be replaced with B" may mean replacing A with B, as well as replacing B with A. Also, in the above explanation, when it is written that "C may be D" and "C may be E", it may also mean that "D may be E". Also, in the above explanation, when it is written that "F may be G" and "G may be H", it may also mean that "F may be H".

[0119] In the above explanation, if the conditions "A" and "B" are contradictory conditions, the condition "B" may be expressed as the "other" condition of the condition "A."

[0120] A program running on an apparatus according to the present embodiment may be a program that controls a central processing unit (CPU) or the like to cause a computer to function so as to realize the functions of the present embodiment. The program or information handled by the program is temporarily loaded into a volatile memory such as a random access memory (RAM) during processing, or stored in a nonvolatile memory such as a flash memory or a hard disk drive (HDD), and is read, modified, or written by the CPU as necessary.

[0121] Note that a part of the device in the above-described embodiment may be realized by a computer. In this case, a program for realizing this control function may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read and executed by a computer system. The "computer system" here refers to a computer system built into the device, including hardware such as an operating system and peripheral devices. Furthermore, the "computer-readable recording medium" may be any of a semiconductor recording medium, an optical recording medium, a magnetic recording medium, etc.

[0122] Furthermore, the term "computer-readable recording medium" may also include a medium that dynamically stores a program for a short period of time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, or a medium that stores a program for a certain period of time, such as a volatile memory within a computer system that serves as a server or client in such cases. The program may also be one that realizes part of the above-mentioned functions, or one that can realize the above-mentioned functions in combination with a program already stored in the computer system.

[0123] Furthermore, each functional block or feature of the device used in the above-described embodiments may be implemented or performed by an electrical circuit, typically an integrated circuit or multiple integrated circuits. The electrical circuit designed to perform the functions described herein may include a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or a combination thereof. The general-purpose processor may be a microprocessor, or alternatively, the processor may be a conventional processor, controller, microcontroller, or state machine. The general-purpose processor or each of the aforementioned circuits may be composed of digital circuits or analog circuits. Furthermore, if advances in semiconductor technology result in the emergence of integrated circuit technology that replaces current integrated circuits, integrated circuits based on that technology may also be used.

[0124] It should be noted that the present embodiment is not limited to the above-described embodiment. In the embodiment, an example of a device is described, but the present embodiment is not limited to this, and can be applied to terminal devices or communication devices such as stationary or non-movable electronic devices installed indoors or outdoors, for example, AV equipment, kitchen equipment, cleaning / washing equipment, air conditioning equipment, office equipment, vending machines, and other household appliances.

[0125] Although this embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment and includes design modifications within the scope of the gist of this embodiment. Furthermore, this embodiment can be modified in various ways within the scope of the claims, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of this embodiment. Furthermore, configurations in which elements described in the above embodiment are substituted with elements that achieve the same effect are also included. [Explanation of symbols]

[0126] 100 ng-eNB 102 gNB 110, 112, 114 Interface 122UE 200 PHY 202 MAC 204 RLC 206 PDCP 208 RRC 210 PC5-S 310 SDAP 400 Discovery 500 Receiver 502 Processing section 504 Transmission Unit 600 SRAP

Claims

1. A first terminal device capable of sidelink communication, a processing unit; a receiving unit for receiving a first direct communication request (DCR) message from a second terminal device; a transmitter unit, the processing unit measures a Reference Signal Received Power (RSRP) of the first DCR message; The processing unit determines whether the RSRP of the first DCR message is greater than a threshold; The transmitter transmits a second DCR message to a third terminal device based on the RSRP being greater than the threshold; the first DCR message and the second DCR message are messages used to select a terminal device that will be responsible for forwarding the sidelink transmission of the second terminal device to the third terminal device; and the first DCR message includes identifiers of the second terminal device and the third terminal device; The second DCR message includes identifiers of the first terminal device, the second terminal device, and the third terminal device; Terminal device.

2. A method for a first terminal device capable of sidelink communication, comprising: receiving a first Direct Communication Request (DCR) message from a second terminal device; measuring a Reference Signal Received Power (RSRP) of the first DCR message; determining whether the RSRP of the first DCR message is greater than a threshold; and transmitting a second DCR message to a third terminal device based on the RSRP being greater than the threshold; the first DCR message and the second DCR message are messages used to select a terminal device that will be responsible for forwarding the sidelink transmission of the second terminal device to the third terminal device; and the first DCR message includes identifiers of the second terminal device and the third terminal device; The second DCR message includes identifiers of the first terminal device, the second terminal device, and the third terminal device; method.

3. An integrated circuit implemented in a first terminal device capable of sidelink communication, receiving a first Direct Communication Request (DCR) message from a second terminal device; a function of measuring Reference Signal Received Power (RSRP) of the first DCR message; determining whether the RSRP of the first DCR message is greater than a threshold; and a function of transmitting a second DCR message to a third terminal device based on the RSRP being greater than the threshold value; the first DCR message and the second DCR message are messages used to select a terminal device that will be responsible for forwarding the sidelink transmission of the second terminal device to the third terminal device; and the first DCR message includes identifiers of the second terminal device and the third terminal device; The second DCR message includes identifiers of the first terminal device, the second terminal device, and the third terminal device; Integrated circuit.

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