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 wireless access, core networks, services, etc.

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

[0004] In addition, 3GPP has begun technical studies and standardization of NR (New Radio, or NR Radio access) as a radio access technology (Radio Access Technology: RAT) for cellular mobile communication systems for the 5th Generation (5G). Currently, 3GPP is continuing 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] In 3GPP, as an extension technology of NR, a technology called sidelink, which allows terminal devices to communicate directly with each other without going through the core network, is being considered. In addition, research has begun on a technology (UE-to-UE relay) that supports communication between terminal devices by adding other terminal devices between terminal devices.

[0007] One aspect of the present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention 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] In order to achieve the above object, one aspect of the present invention takes the following measures. That is, one aspect of the present invention is a first terminal device capable of sidelink communication, comprising a processing unit, a receiving unit for receiving a first message from a second terminal device, and a transmitting unit, 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 that is responsible for forwarding sidelink transmission 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, the integrated circuit having a function of receiving a first message from a second terminal device, a function of determining information based on a reference signal received power (RSRP: Reference Signal Received Power) of the first message received from the second terminal device, and a function of transmitting a second message including the information to a third terminal device, the first message and the second message being 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. Effect 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 description of the drawings]

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

[0014] Hereinafter, the present 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 in 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 an 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 called a Uu interface. The ng-eNB (ng E-UTRAN Node B) 100 may be a base station device. The ng-eNB 100 may have an E-UTRA protocol, which will be described later. The E-UTRA protocol may be composed of an E-UTRA User Plane (UP) protocol, which will be described later, and an E-UTRA Control Plane (CP) protocol, which will be described later. 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 called an 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 an NR protocol, which will be described later. The NR protocol may be composed of an NR user plane (User Plane: UP) protocol, which will be described later, and an NR control plane (Control Plane: CP) protocol, which will be described later. 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 called an Xn interface. The ng-eNB and the gNB may be connected 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 be connected to the 5GC via the NG interface.

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

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

[0022] Sidelink is a technology for 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 with 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." The transmission modes may be referred to as a cast type, etc.

[0024] Unicast transmission is characterized by: (1) support of one PC5-RRC connection between a paired UE; (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] In addition, broadcast transmission can be characterized as (1) transmission and reception of user traffic between UEs on the sidelink.

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

[0028] Fig. 2(A) is a diagram of a protocol stack of a control plane (CP) for SCCH using RRC configured on a PC5 interface. As shown in Fig. 2(A), the control plane protocol stack for SCCH using RRC may be composed of PHY (Physical layer) 200, which is a radio physical layer, MAC (Medium Access Control) 202, 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 RRC (Radio Resource Control) 208, which is a radio resource control layer. Also, Fig. 2(B) is a diagram of a protocol stack of a control plane for 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] Fig. 3(A) is a diagram of a protocol stack of a control plane for SBCCH configured on a PC5 interface. As shown in Fig. 3(A), the control plane protocol stack for SBCCH may be configured 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, and an RRC (Radio Resource Control) 208 which is a radio resource control layer. Fig. 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. 3B, 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 Radio Link Control (RLC) 204 which is a radio link control layer, a Packet Data Convergence Protocol (PDCP) 206 which is a packet data convergence protocol layer, and a Service Data Adaptation Protocol (SDAP) 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. Also, 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 be 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, respectively. In addition, when sidelink communication is performed using the E-UTRA technology, the SDAP layer may not be required. In order to clarify that it is a protocol for sidelink, for example, RLC may be expressed as sidelink RLC, SL RLC, PC5 RLC, etc., and for other protocols, the term "sidelink", "SL", or "PC5" may be added to the beginning to indicate that they are protocols for sidelink.

[0032] In the present embodiment, when the E-UTRA protocol and the NR protocol are to be distinguished from each other, PHY, MAC, RLC, PDCP, and RRC may be referred to as PHY for E-UTRA or PHY for LTE, MAC for E-UTRA or MAC for LTE, RLC for E-UTRA or RLC for LTE, PDCP for E-UTRA or PDCP for LTE, and RRC for E-UTRA or RRC for LTE, respectively. Also, 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 RLC for LTE, E-UTRA PDCP or LTE PDCP, and E-UTRA RRC or RRC for LTE, respectively. Also, when the E-UTRA protocol and the NR protocol are to be distinguished from each other, PHY, MAC, RLC, PDCP, and RRC may be referred to as PHY for NR, MAC for NR, RLC for NR, PDCP for NR, and RRC for NR, 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] The following 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 called MAC PDU (Protocol Data Unit), RLC PDU, PDCP PDU, and SDAP PDU, respectively. Also, 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 called MAC SDU (Service Data Unit), RLC SDU, PDCP SDU, and SDAP SDU, respectively. Also, a segmented RLC SDU may be called an RLC SDU segment.

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

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

[0037] Hereinafter, the meaning of "A is given (provided) by the upper layer" or "A is given (provided) by the upper layer" may mean that the upper layer (mainly the RRC layer, the MAC layer, etc.) of the terminal device receives A from the base station device or another terminal device, and the received A is given (provided) to the physical layer of the terminal device from the upper layer of the terminal device. For example, in a terminal device, "being provided with upper layer parameters" may mean receiving an upper layer signal from a base station device or another terminal device, and providing the upper layer parameters included in the received upper layer signal to the physical layer of the terminal device from the upper 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 sets the received upper layer parameter in the upper layer. However, setting an upper layer parameter in a terminal device may include setting a default parameter that is given in advance to the upper layer of the terminal device. When describing the 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 be provided with 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 a 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 regarding 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 functions of the MAC will be described. The MAC may be called a MAC sublayer. The MAC may have a function of mapping various logical channels to corresponding transport channels. The logical channels may be identified by a logical channel identity (or logical channel ID). The MAC may be connected to the upper RLC via a logical channel. The logical channels may be divided into a control channel for transmitting control information and a traffic channel for transmitting user information depending on the type of information to be transmitted. The MAC may have a function of multiplexing MAC SDUs belonging to one or more different logical channels and providing them to the PHY. The MAC may also have a function of de-multiplexing MAC PDUs provided from the PHY and providing them to the upper layer via the logical channel to which each MAC SDU belongs. The MAC may also have a function of performing error correction through HARQ (Hybrid Automatic Repeat reQuest). The MAC may also have a function of reporting scheduling information. The MAC may have a function to perform priority processing between terminal devices using dynamic scheduling. The MAC may also have a function to perform priority processing between logical channels within one terminal device. The MAC may have a function to perform priority processing of overlapping resources within one terminal device. The E-UTRA MAC may have a function to identify Multimedia Broadcast Multicast Services (MBMS). The NR MAC may have a function to identify Multicast / Broadcast Services (MBS). The MAC may have a function to select a transport format.The MAC may have a function of performing discontinuous reception (DRX) and / or discontinuous transmission (DTX), a function of executing a random access (RA) procedure, a power headroom report (PHR) function for notifying information on available transmission power, a buffer status report (BSR) function for notifying information on the amount of data in the transmission buffer, and the like. The NR MAC may have a bandwidth adaptation (BA) function. The MAC PDU format used in the E-UTRA MAC may differ from the MAC PDU format used in the NR MAC. The MAC PDU may include a MAC control element (MAC CE), which is an element for performing control in the MAC.

[0046] In addition, the MAC sublayer may provide additional services and functions on 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 for broadcasting sidelink system information from one terminal device to one or more terminal devices. The SBCCH may be mapped to the SL-BCH, which is a sidelink transport channel.

[0049] The SCCH (Sidelink Control Channel) may be a logical channel for sidelink 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 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. The STCH may be mapped to the SL-SCH, which is a sidelink transport channel.

[0051] An example of the function of the RLC will be described. The RLC may be called an RLC sublayer. The E-UTRA RLC may have a function of segmenting and / or concatenating data provided from the PDCP of the upper layer and providing it to a lower layer. The E-UTRA RLC may have a function of reassembling and reordering data provided from the lower layer and providing it to the upper layer. The NR RLC may have a function of adding a sequence number independent of the sequence number added by the PDCP to data provided from the PDCP of the upper layer. The NR RLC may also have a function of segmenting data provided from the PDCP and providing it to the lower layer. The NR RLC may also have a function of reassembling data provided from the lower layer and providing it to the upper layer. The RLC may also have a function of retransmitting data and / or a function of requesting retransmission (Automatic Repeat reQuest: ARQ). RLC may also have a function for performing error correction by ARQ. The control information, which is sent from the receiving side of RLC to the transmitting side to perform ARQ and indicates the data that needs to be retransmitted, may be called a status report. The status report transmission instruction, which is sent from the transmitting side of RLC to the receiving side, may be called a poll. RLC may also have a function for detecting data duplication. RLC may also have a function for 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 divided, and an RLC header does not need to be added. The TM RLC entity is a uni-directional entity and may be configured as a transmitting TM RLC entity or a receiving TM RLC entity.In UM, the division and / or concatenation of data received from a higher layer, the addition of an RLC header, etc. are performed, but the retransmission control of data is not required. The UM RLC entity may be a unidirectional entity or a bi-directional entity. If the UM RLC entity is a unidirectional entity, the UM RLC entity may be configured as a transmitting UM RLC entity or a receiving UM RLC entity. If the UM RLC entity is a bi-directional 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 division and / or concatenation of data received from a higher layer, the addition of an RLC header, the retransmission control of data, etc. are performed. The AM RLC entity is a bi-directional 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 called a TMD PDU. Also, data provided to a lower layer in UM and / or data provided from a lower layer may be called a UMD PDU. Data provided to a lower layer in AM or data provided from a lower layer may be called 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 called RLC DATA PDUs (RLC Data PDUs). Control RLC PDUs may be called RLC CONTROL PDUs (RLC Control PDUs).

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

[0053] An example of the function of PDCP will be described. PDCP may be called a PDCP sublayer. PDCP may have a function of 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 sections. A protocol used for header compression / decompression of IP packets may be called ROHC (Robust Header Compression) protocol. A protocol used for header compression / decompression of Ethernet frames may be called EHC (Ethernet (registered trademark) Header Compression) protocol. PDCP may also have a function of data encryption / decryption. PDCP may also have a function of data integrity protection / integrity verification. PDCP may also have a re-ordering function. PDCP may also have a function of retransmitting PDCP SDUs. PDCP may also have a function of discarding data using a discard timer. PDCP may also have a duplication function. PDCP may also have a function of discarding duplicated received data. The PDCP entity is a bidirectional entity and may be composed of a transmitting PDCP entity and a receiving PDCP entity. The PDCP PDU format used in E-UTRA PDCP may differ from the PDCP PDU format used in NR PDCP. The PDCP PDU may include a data PDCP PDU and a control PDCP PDU. 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 on the PC5 interface is not supported.

[0055] An example of the function of the SDAP will be described. The SDAP is a service data adaptation protocol layer. In the sidelink, the SDAP may have a function of mapping a sidelink QoS flow sent from a terminal device to another terminal device with a sidelink data radio bearer (DRB). The SDAP may also have a function of storing mapping rule information. The SDAP may also have a function of marking a QoS flow identifier (QoS Flow ID: QFI). The SDAP PDU may include a data SDAP PDU and a control SDAP PDU. The data SDAP PDU may be called an SDAP DATA PDU (SDAP Data PDU). The control SDAP PDU may be called an SDAP CONTROL PDU (SDAP Control PDU). In the sidelink, the SDAP entity of the terminal device may exist for each destination for any of unicast transmission, groupcast transmission, and broadcast transmission associated with the destination. Additionally, reflective QoS is not supported on PC5 interfaces.

[0056] An example of the functionality of RRC will be described. RRC may support services and functions such as transfer of PC5-RRC messages between peer UEs on the PC5 interface, maintenance and release of PC5-RRC connection between two UEs, and detection of sidelink radio link failure for PC5-RRC connection. A PC5-RRC connection is a logical connection between two UEs corresponding to a pair of source L2ID and destination L2ID, and is considered to be established after the corresponding PC5 unicast link is established. There is a one-to-one correspondence between the PC5-RRC connection and the PC5 unicast link. A UE may have multiple PC5-RRC connections to one or multiple UEs for different pairs of source L2ID and destination L2ID. Separate PC5-RRC procedures and messages may be used by the UE to transfer UE capabilities and sidelink configuration to the peer UE. Both peer UEs may also exchange their UE capabilities and sidelink configuration with each other using separate bidirectional procedures. The UE releases the PC5-RRC connection if there is no interest 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 in association with a PSSCH. Note that the sidelink transmission may be transmitting a signal and / or data (message) via a physical channel for sidelink (PSBCH, PSSCH, PSCCH, etc.), and the sidelink reception may be receiving a signal and / or data (message) via a physical channel for sidelink. Also, communication using sidelink transmission and sidelink reception may be referred to as sidelink communication. The UE may recognize the data (message) based on the signal. Each PSSCH transmission may be associated with a PSCCH (a PSCCH) transmission. The PSCCH transmission may carry a first SCI (1st stage of the SCI) associated with the PSSCH transmission, and a second SCI (2nd stage of the SCI) may be carried within the resources of the PSSCH (the PSSCH). Note that the PSCCH transmission may include the first SCI, and the PSSCH transmission may include the second SCI. Also, the PSCCH transmission and the PSSCH transmission may be referred to as sidelink transmission, and the 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. The 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 arrangement pattern, second SCI format, beta offset indication value, number of DMRS ports, information indicating modulation and coding scheme, and other information. Also, the SCI carried on the PSSCH may be the second SCI, and the second SCI may transport sidelink scheduling information and / or inter-UE coordination related information. The second SCI may contain information in a format designated 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, redundancy version, source ID for identifying a source UE, destination ID for 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 an identifier indicating a zone and request information regarding a 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 information for providing inter-UE coordination information is included in SCI format 2-C, SCI format 2-C may additionally include information such as information indicating a resource combination, information indicating a first resource position, position information of a reference slot, information indicating a type of resource set, and a lowest subchannel index. When SCI format 2-C includes information requesting inter-UE coordination information, SCI format 2-C may additionally include information such as priority, number of subchannels, resource reservation interval, position of resource selection window, information indicating type of resource set, etc. Each SCI format may include information other than the above-mentioned information.

[0058] Next, the procedure of the UE receiving the PSSCH will be described. When the UE detects SCI format 1-A on the 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 the higher layer. Note that the UE does not need to decode more than one PSCCH in 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 and SCI format 2-B, and 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 a higher (RRC) layer, the UE may measure the PSSCH RSRP from the DMRS resource element 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 element 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 and Model B. Figure 4 shows a protocol stack in a discovery procedure. Model A may use a single discovery protocol message, and Model B may use two discovery protocol messages. The single discovery protocol message in Model A may be an Announcement message, and the discovery protocol messages in Model B may be a Solicitation message and a Response message. The Announcement message, the Solicitation message, and the Response message may be collectively referred to as a Discovery message, and messages with other names used in the discovery procedure may be referred to as Discovery messages. Below, an overview of the procedures of Model A and Model B in ProSe Direct Discovery is shown.

[0061] In Model A, a UE that transmits 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 a discovery message type, a ProSe Application Code or a ProSe Restricted Code, and a security protection element, and may additionally include metadata information. The announce message is transmitted using a destination layer-2 ID (D2ID) and a source layer-2 ID (S2ID), and the monitoring UE determines a destination layer-2 ID to receive the announce message. Note that the destination layer-2 ID may be a Layer-2 identifier of the destination UE, and the source layer-2 ID may be a Layer-2 identifier of the source UE.

[0062] In Model B, a UE that sends an invitation message may be referred to as a discoverer UE, and a UE that receives the invitation message and / or sends a response message to the discoverer UE may be referred to as a discoveree UE. The invitation message may include information such as a discovery message type, a ProSe Query Code, and a security protection element. The invitation message is sent using a destination L2ID and a source L2ID, and the discoveree UE determines a destination L2ID to receive the invitation message. In addition, the discoveree UE responding to the invitation 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 additionally include metadata information. The response message is sent using a source L2ID, and the destination L2ID is set to the source L2ID of the received invitation message.

[0063] Discovery may include types other than ProSe Direct Discovery, which discovers other UEs to communicate directly with other UEs, and may include Group member Discovery, which discovers one or more UEs to communicate within a group using a sidelink, and 5G ProSe UE-to-Network Relay Discovery, which discovers candidate relay UEs to connect to a network via a relay UE. The above-mentioned discovery is an example of discovery provided by an application called ProSe, but in addition to the above-mentioned types, there may be different types of discovery depending on the application or service that performs sidelink communication. Also, the information included in the discovery protocol message may differ depending on the type of discovery, and an additional message may be transmitted to transmit additional information.

[0064] FIG. 4 is a diagram of an example of a protocol configuration including a discovery protocol according to the present embodiment. As shown in FIG. 4, a protocol stack of a discovery plane including a 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 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 Discovery 400 which is a discovery protocol layer. Discovery 400 may be a protocol used to process procedures related to discovery. In addition, an interface between UEs performing discovery may be referred to as PC5-D.

[0065] A plurality of resource pools for transmitting messages (discovery messages) in a discovery procedure may be configured, or one or a plurality of resource pools may be configured exclusively for discovery. When a resource pool dedicated to discovery is configured, the UE may use the resource pool dedicated to discovery as a resource pool for transmitting a discovery message, and when a resource pool dedicated to discovery is not configured, the UE may use a resource pool for sidelink communication as a resource pool for transmitting a discovery message. Note that a plurality of resource pools for sidelink communication and a resource pool dedicated to discovery may be configured at the same time. Each resource pool may be configured by UE-dedicated signaling or may be configured in advance.

[0066] Also described is a Direct Communication Request (DCR) message. 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 may include a target UE identifier if the target UE identifier is provided by the application layer, and may include other information, such as information related to security and information related to the application. 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 in a sidelink.

[0067] A sidelink signaling radio bearer (SRB) may be configured for each unicast PC5-RRC connection. A sidelink SRB used to transmit a PC5-S message before PC5-S security is established may be referred to as SL-SRB0. A sidelink SRB used to transmit a PC5-S message for establishing PC5-S security may be referred to as SL-SRB1. A sidelink SRB used to transmit a protected PC5-S message after PC5-S security is established may be referred to as SL-SRB2. A sidelink SRB used to transmit a 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. The PC5-RRC signaling may be RRC signaling between UEs transmitted and received on PC5. In addition, PC5-RRC signaling may be referred to as a PC5-RRC message, etc.

[0068] UE-to-UE relay may be a technology in which a source UE communicates with a destination UE via sidelink communication with a relay UE. The relay UE may have a function and / or role of forwarding (or relaying) data for the destination UE received from the source 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, U2U Remote UE, etc., and the relay UE may be called U2U relay UE, etc. The term UE-to-UE relay may also be called 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 FIG. 6 and FIG. 7, an SRAP 600 may be present. The SRAP 600 may be called an SRAP layer (Sidelink Relay Adaptation Protocol layer), an SRAP layer, or a different name may be used. As shown in FIG. 6 and FIG. 7, the PHY 200, the MAC 202, the RLC 204, and the SRAP 600 may be associated between a remote UE and an L2 U2U relay UE, and between an L2 U2U relay UE and other remote UEs, respectively, and the PDCP 206, the RRC 208, and the 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 an RRC 208 to control a PC5 connection between a remote UE and another remote UE (not shown). In a protocol stack in a Layer 3 (L3) UE-to-UE relay, a PHY 200, a MAC 202, an RLC 204, a PDCP 206, an RRC 208, and an SDAP 210 may be associated between a remote UE and a U2U relay UE, and between a U2U relay UE and another remote UE, respectively, and an SRAP 600 may not be configured (not shown). In an L3 U2U relay, a layer higher than an SDAP may have a function for transmitting data received on a Uu link on a PC5 link. An SRAP layer may be included in an 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 purposes. 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 may have other functions in addition to the above.

[0072] In addition, when a remote UE transmits data for a side link 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 data for a side link 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 may be interchangeable. The destination UE may be referred to as a destination remote UE, or simply as a remote UE, or 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, in order to clarify that they are terminals performing U2U relay. In addition, to clarify that communication is performed through an L2 U2U relay, the UE 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 through an L3 U2U relay, the UE 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 data for a side link, but also when forming a certain U2U relay pair (a pair of one remote UE, one relay UE, and another remote UE), a UE that transmits a discovery message first 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] Also, the UE may transmit a discovery message and / or a direct communication request message to perform U2U relay. For example, in order to select a relay UE for U2U relay, the source UE may transmit a discovery message or a direct communication request message. Discovery in this case may be Model B discovery. A UE (a relay UE candidate) that receives a discovery message or a direct communication request message transmitted from a source UE may transmit a discovery message or a direct communication request message to a destination UE. Also, a UE (a relay UE candidate) may transmit a discovery message and / or a direct communication request message to a source UE. Discovery in this case 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 that transmit multiple Demodulation Reference Signals (DMRSs) associated with the PSBCH. The PSSCH-RSRP (PSSCH RSRP) may be defined as a linear average of power contributions of resource elements of antenna ports that transmit multiple DMRSs associated with the PSSCH, and 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 that transmit multiple DMRSs associated with the PSCCH. The DMRS may be used to demodulate signals of the PSBCH, PSSCH, and PSCCH, for example. A terminal device that performs 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 a resource element transmitting a DMRS associated with the PSSCH carrying the discovery message.

[0076] In addition, in measurements on the sidelink, UE 122 may measure the following quantities in addition to the above-mentioned RSRP. (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 a linear average of power ([W]) observed on configured subchannels in OFDM symbols of slots configured for PSCCH and PSSCH starting from the second OFDM symbol. The SL CR in slot n may be defined as a 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 in 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 is a mode in which the UE performs sidelink transmission using resources scheduled by the base station, and Mode 2 is a mode in which the UE automatically selects resources for sidelink transmission. In Mode 1, the UE must be RRC_CONNECTED, and 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 that have been configured before performing sidelink transmission.

[0079] Various embodiments of the present invention will be described based on the above description. 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. In order to avoid complicating the explanation, Fig. 5 shows only 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 control information (SCI, MAC control element, RRC signaling, etc.), discovery messages, information including user data, etc. to other terminal devices. The processor 502 may include some or all of the functions of various layers (for example, 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] FIG. 8 shows an example of an embodiment of the present invention.

[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 by the 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. In addition to or instead of this, in step S802, the information transmitted by the UE 122 to the second terminal device may be, for example, the RSRP (SL-RSRP) measured in the sidelink communication when the UE 122 has performed sidelink communication with the first terminal device, or may be, for example, an offset value determined based on the RSRP (SL-RSRP) measured in the sidelink communication when the UE 122 has performed sidelink communication with the first terminal device. In addition to or instead of this, in step S802, the information transmitted by the 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 path loss 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. 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, when communicating in sidelink 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 offset value of RSRP 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] In addition, instead of passing the information to the second terminal device, the UE 122 may select a resource pool to transmit a discovery message to be transmitted to the second terminal device, for example, as a second message, according to the SD-RSRP, SL-RSRP, path loss, or offset value. For example, when using SD-RSRP, if the SD-RSRP is in a first range, the discovery message may be transmitted using the first resource pool, and if the SD-RSRP is in a second range, the discovery message may be transmitted using the second resource pool. In addition, if the UE 122 transmits a discovery message using the first resource pool and the second terminal device receives the discovery message in a resource pool corresponding to the first resource pool, the second terminal device may determine that the SD-RSRP is in the first range. In addition, 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 the U2U relay. Also, the same processing may be applied when messages other than a discovery message are used as the first message and the second message.

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

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

[0090] In step S902, the determination may be, for example, determining whether the RSRP of the received first message is better than a threshold. In addition or instead, in step S902, the determination may be, for example, determining whether the path loss of the received first message is better than a threshold. In addition or instead, in step S902, the determination may be, for example, when sidelink communication is performed with the first terminal device, determining whether the RSRP in the sidelink communication (SL-RSRP) is better than a threshold. 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. Also, 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 or not the SL-RSRP is equal to or greater than the threshold may be replaced with a determination of whether or not the SL-RSRP is greater than the threshold. Furthermore, the above-mentioned determination of "whether or not the RSRP is better than the threshold" may be replaced with a determination of "whether or not 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, for example, 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, etc.). 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 to not transmit, for example, 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 not forward the received first message to a higher layer (discovery layer).

[0092] In addition, the threshold value for UE 122 to determine whether the SD-RSRP, the path loss, or the SL-RSRP is good may be set by a network, may be set in advance in UE 122 as a default setting, or the first terminal device may determine the threshold value and transmit the determined threshold value by signaling of a higher layer (RRC, application layer, etc.), or may be transmitted together with a discovery message by being included in 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 other messages 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. Depending on the types of the first message and the second message, an appropriate RSRP may be measured, and for example, when 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] 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 on the first terminal device and information on the second terminal device. For example, a discovery message transmitted from a UE 122 may include information on the first terminal device, information on the UE 122, and information on the second terminal device. The information on the UE 122 and each terminal device may be an identifier for identifying each terminal, or may include other information in addition to or instead of the identifier. The discovery message may also include information on 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 operates based on the decision in step S1004.

[0097] The signal may be a signal conveying a discovery message, a signal conveying a Direct Communication Request message, a signal conveying a message of another higher layer (such as an application layer or a discovery layer), or a signal conveying data transmitted in sidelink communication between the UE 122 and the first terminal device. The UE 122 may measure Reference Signal Received Power (RSRP) based on the signal. In addition to or instead of that, 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 operation 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. 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.). When 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 has transmitted the signal based on the signal, and may also determine whether an RSRP measured using the signal is within a first range. In this case, the UE 122 may operate in step S1004 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 operation 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 operation 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 additionally 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 "in the first range" may mean that the RSRP is greater than threshold 1, that the RSRP is greater than threshold 1 and less than threshold 2, or that the RSRP is less than threshold 2. The conditions "greater than" and "smaller than" may be replaced with conditions such as "greater than or equal to", "less than or equal to", etc.

[0101] As another example of the operation in step S1004, when it is determined in step S1002 that the RSRP is in 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 in the first range or similar information. When it is determined in step S1002 that the RSRP is not in 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 in 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 set stored in the first list may 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 the RSRP related to the set. When the first timer expires, the UE 122 may delete the set from the first list. When 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. Note that a timer may be associated with each set, and multiple timers may operate. The timer value may be set by the base station, may be set based on the signal, may be set to a default value, or may be used as a pre-set value. The set may be managed by a method other than time. For example, the UE 122 may delete all sets included in the first list when 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 sidelink communication capable UE 122 performs an information determination in step S1100 and acts based on the determination in step S1102.

[0105] In step S1100, the determination of information may be, for example, a determination of whether a first identifier is included in the 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 by 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. In addition to or instead of that, in step S1100, the determination of information may be, for example, a determination of whether an RSRP corresponding to the first identifier is in a first range. The RSRP corresponding to the first identifier may be an RSRP stored in a set including 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 in the first range. The RSRP being in 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 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. The thresholds 1 and 2 may be set by a base station, or default values ​​may be set, or preset values ​​may be used, or they may be set by other methods.

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

[0107] Also, in Model A discovery, UE 122 may transmit the first list to a source UE in a discovery message. In this case, UE 122 may transmit all sets included in the first list as a list, or may transmit a part of sets included in the first list as a list. Note that UE 122 may transmit the first list 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 rearranged in the list. For example, the sets may be rearranged 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 the 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 the measured values. The information other than the 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 RSRPs may be SD-RSRPs, SL-RSRPs, 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 by a notification from a higher layer (application layer), or may recognize the same based on other methods. The RSRP measured by the UE 122 when it receives the DCR message may be the SL-RSRP, the SD-RSRP, or may be called by other names. In the above description, the expression "store" may be replaced with expressions such as "add" and "include". The names "source UE" and "destination UE" used in each embodiment may be replaced with each other, or may be called by 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 UE 122, and 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 shown in Non-Patent Documents 1, 5, and 6, the UE can only evaluate the link quality with a directly connected UE. However, according to each embodiment, the UE can evaluate the relay route 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 addition, in the above description, expressions such as "to be notified" and "to be pointed out" may be interchangeable.

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

[0114] In addition, in the above description, expressions such as "includes," "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 addition, in the above description, expressions such as "determined to be...", "is set to...", "includes...", etc. may be interchangeable.

[0117] Furthermore, in each of the process examples or process flow examples in the above description, some or all of the steps may not be executed. Furthermore, in each of the process examples or process flow examples in the above description, the order of the steps may be different. Furthermore, in each of the process examples or process flow examples in the above description, some or all of the processing within each step may not be executed. Furthermore, in each of the process examples or process flow examples 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 "being A".

[0118] In the above explanation, "A may be replaced with B" may mean replacing A with B, as well as replacing B with A. 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". 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 condition "A" and condition "B" are contradictory conditions, condition "B" may be expressed as the "other" condition of condition "A."

[0120] The program that runs on the device according to this embodiment may be a program that controls a Central Processing Unit (CPU) or the like to make a computer function so as to realize the functions of this 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 is stored in a non-volatile memory such as a flash memory or a Hard Disk Drive (HDD), and is read, modified, and written by the CPU as necessary.

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

[0122] Furthermore, the term "computer-readable recording medium" may 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, and a medium that stores a program for a certain period of time, such as a volatile memory inside a computer system that serves as a server or client in such a case. The above program may be one that realizes part of the above-mentioned functions, or may be one that can realize the above-mentioned functions in combination with a program already recorded in the computer system.

[0123] Also, each functional block or feature of the device used in the above-mentioned embodiment may be implemented or executed by an electric circuit, i.e., typically an integrated circuit or a plurality of integrated circuits. The electric circuit designed to execute 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. Also, when an integrated circuit technology that replaces the current integrated circuits appears due to the progress of semiconductor technology, it is possible to use an integrated circuit according to that technology.

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

[0125] Although this embodiment has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes within the scope of the gist of this embodiment are also included. In addition, 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. In addition, configurations in which elements described in the above embodiment are replaced with elements that have 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 310SDAP 400 Discovery 500 Receiver 502 Processing section 504 Transmitter 600 SRAP

Claims

1. A first terminal device capable of sidelink communication, a processing unit, a receiving unit that receives a first direct communication request (DCR) message from a second terminal device, a transmitting unit, and the processing unit measures the 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, based on the RSRP being greater than the threshold, the transmitting unit transmits a second DCR message to a third terminal device, the first DCR message and the second DCR message are messages used to select a terminal device that plays a role of transferring sidelink transmission of the second terminal device to the third terminal device, 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, a terminal device.

2. A method for a first terminal device capable of sidelink communication, a step of receiving a first direct communication request (DCR) message from a second terminal device, a step of measuring the reference signal received power (RSRP) of the first DCR message, a step of determining whether the RSRP of the first DCR message is greater than a threshold, based on the RSRP being greater than the threshold, a step of transmitting a second DCR message to a third terminal device. The first DCR message and the second DCR message are messages used to select a terminal device that plays a role of transferring the sidelink transmission of the second terminal device to the third terminal device. 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, a function of receiving a first direct communication request (DCR) message from a second terminal device, a function of measuring a reference signal received power (RSRP) of the first DCR message, a function of 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. The first DCR message and the second DCR message are messages used to select a terminal device that plays a role of transferring the sidelink transmission of the second terminal device to the third terminal device. 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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