WO2025014091A1 - Method for performing relay communication in wireless communication system and apparatus therefor - Google Patents

Abstract

Disclosed, according to various embodiments, are a method by which a terminal selects a candidate relay terminal in a wireless communication system, and an apparatus therefor. Disclosed are a method and an apparatus therefor, the method comprising the steps of: receiving configuration information related to relay communication; receiving discovery messages from a plurality of relay terminals; and selecting a first number or more of candidate relay terminals for the relay communication from among the plurality of relay terminals on the basis of the discovery messages and the configuration information.

Description

Method for performing relay communication in a wireless communication system and device therefor

The present invention relates to a method for selecting a relay terminal to perform relay communication among a plurality of relay terminals in a wireless communication system and to a device therefor.

A wireless communication system is a multiple access system that supports communication with multiple users by sharing available system resources (e.g., bandwidth, transmission power, etc.). Examples of multiple access systems include a CDMA (code division multiple access) system, an FDMA (frequency division multiple access) system, a TDMA (time division multiple access) system, an OFDMA (orthogonal frequency division multiple access) system, an SC-FDMA (single carrier frequency division multiple access) system, and an MC-FDMA (multi carrier frequency division multiple access) system.

Sidelink (SL) refers to a communication method that establishes a direct link between user equipment (UE) to directly exchange voice or data between terminals without going through a base station (BS). SL is being considered as a solution to solve the burden on base stations due to rapidly increasing data traffic.

V2X (vehicle-to-everything) refers to a communication technology that exchanges information with other vehicles, pedestrians, and objects with built-in infrastructure through wired/wireless communication. V2X can be divided into four types: V2V (vehicle-to-vehicle), V2I (vehicle-to-infrastructure), V2N (vehicle-to-network), and V2P (vehicle-to-pedestrian). V2X communication can be provided through the PC5 interface and/or the Uu interface.

Meanwhile, as more and more communication devices require greater communication capacity, there is a growing need for improved mobile broadband communication over existing Radio Access Technology (RAT). Accordingly, communication systems that consider services or terminals sensitive to reliability and latency are being discussed, and the next-generation radio access technology that considers improved mobile broadband communication, massive MTC (Machine Type Communication), URLLC (Ultra-Reliable and Low Latency Communication), etc. can be called new RAT (new radio access technology) or NR (new radio). V2X (vehicle-to-everything) communication can also be supported in NR.

Figure 1 is a diagram for explaining and comparing V2X communication based on RAT before NR and V2X communication based on NR.

In relation to V2X communication, in RATs prior to NR, methods for providing safety services based on V2X messages such as Basic Safety Message (BSM), Cooperative Awareness Message (CAM), and Decentralized Environmental Notification Message (DENM) have been mainly discussed. V2X messages may include location information, dynamic information, attribute information, etc. For example, a terminal may transmit a CAM of a periodic message type and/or a DENM of an event triggered message type to another terminal.

For example, CAM may include basic vehicle information such as vehicle dynamic status information such as direction and speed, vehicle static data such as dimensions, exterior lighting status, and route history. For example, the terminal may broadcast CAM, and the latency of the CAM may be less than 100ms. For example, when an emergency situation such as vehicle breakdown or accident occurs, the terminal may generate DENM and transmit it to other terminals. For example, all vehicles within the transmission range of the terminal may receive CAM and/or DENM. In this case, DENM may have a higher priority than CAM.

Since then, various V2X scenarios have been proposed in NR in relation to V2X communication. For example, various V2X scenarios may include vehicle platooning, advanced driving, extended sensors, and remote driving.

For example, based on vehicle platooning, vehicles can dynamically form a group and move together. For example, in order to perform platoon operations based on vehicle platooning, vehicles belonging to the group can receive periodic data from the lead vehicle. For example, vehicles belonging to the group can use the periodic data to reduce or increase the gap between vehicles.

For example, based on improved driving, the vehicles can be semi-autonomous or fully automated. For example, each vehicle can adjust its trajectories or maneuvers based on data acquired from local sensors of nearby vehicles and/or nearby logical entities. Additionally, for example, each vehicle can share driving intentions with nearby vehicles.

For example, based on the extended sensors, raw data or processed data, or live video data acquired through local sensors can be exchanged between vehicles, logical entities, pedestrian terminals, and/or V2X application servers. Thus, for example, the vehicle can perceive the environment better than it can perceive using its own sensors.

For example, based on remote driving, for a person who cannot drive or a remote vehicle located in a dangerous environment, a remote driver or V2X application can operate or control the remote vehicle. For example, in the case of predictable paths such as public transportation, cloud computing-based driving can be used to operate or control the remote vehicle. In addition, for example, access to a cloud-based back-end service platform can be considered for remote driving.

Meanwhile, a method to specify service requirements for various V2X scenarios, such as vehicle platooning, enhanced driving, expanded sensors, and remote driving, is being discussed in NR-based V2X communications.

The technical problem to be solved by the present invention is to provide a method for performing relay communication more accurately and efficiently.

The technical challenges are not limited to the technical challenges mentioned above, and other technical challenges not mentioned will be clearly understood by those skilled in the art to which the present invention belongs from the description below.

In a wireless communication system according to one aspect, a method for a terminal to select a candidate relay terminal includes: a step of receiving configuration information related to relay communication; a step of receiving discovery messages from a plurality of relay terminals; and a step of selecting a first or more number of candidate relay terminals for the relay communication from among the plurality of relay terminals based on the discovery messages and the configuration information, wherein the first number can be determined based on a height of the terminal and the configuration information.

Alternatively, the first number is characterized in that it is determined differently for each height range based on the setting information.

Alternatively, the discovery message may be characterized by including information about the flight path.

Alternatively, the candidate relay terminal is characterized as being a relay terminal having a flight path within a predetermined error range from the flight path of the terminal among the plurality of relay terminals.

Alternatively, the candidate relay terminal is characterized in that it is a relay terminal located within a selection allowable height range set by the setting information among the plurality of relay terminals.

Alternatively, the selection of the candidate relay terminal is characterized in that it is performed based on the height of the terminal falling within a specific height range included in the setting information.

Alternatively, the method further comprises a step of reporting information about the candidate relay terminals of the first number or more to the base station.

Alternatively, the terminal is characterized in that it forms a second or more number of indirect links for the relay communication based on the selected candidate relay terminals.

Alternatively, the second number is characterized in that it is determined based on the setting information and the height of the terminal.

Alternatively, the terminal is characterized as being an Unmanned Aerial Vehicle (UAV) remote terminal.

According to another aspect, a non-transitory computer-readable storage medium having recorded thereon instructions for performing the method for selecting a candidate relay terminal described above may be provided.

According to another aspect, a terminal may be provided that performs the method for selecting a candidate relay terminal described above.

According to another aspect, a processing device may be provided for controlling a terminal performing the method for selecting a candidate relay terminal described above.

According to another aspect, a method for a base station to receive candidate relay information from a terminal in a wireless communication system includes the steps of: transmitting configuration information related to relay communication to the terminal; receiving the candidate relay information for a first or more number of candidate relay terminals selected from among the plurality of relay terminals; and selecting at least one relay terminal to perform relay communication from among the first or more number of candidate relay terminals, and transmitting information about the at least one selected terminal to the terminal, wherein the first number can be determined based on a height of the terminal and the configuration information.

According to another aspect, a base station performing a method of receiving candidate relay information from a terminal as described above may be provided.

According to one embodiment of the present invention, relay communication can be performed more accurately and efficiently in a wireless communication system.

The effects that can be obtained in various embodiments are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art to which the present invention pertains from the description below.

The drawings appended hereto are included to provide an understanding of the present invention and to illustrate various embodiments of the present invention and, together with the description of the specification, serve to explain the principles of the present invention.

Figure 1 is a diagram for explaining and comparing V2X communication based on RAT before NR and V2X communication based on NR.

Figure 2 shows the structure of the LTE system.

Figure 3 shows the structure of the NR system.

Figure 4 shows the structure of a radio frame of NR.

Figure 5 shows the slot structure of an NR frame.

FIG. 6 illustrates a communication structure that can be provided in a 6G system according to one embodiment of the present disclosure.

FIG. 7 illustrates an electromagnetic spectrum according to one embodiment of the present disclosure.

Figure 8 shows a radio protocol architecture for SL communication.

Figure 9 shows a terminal performing V2X or SL communication.

Figure 10 shows resource units for V2X or SL communication.

FIG. 11 illustrates an example of a BWP according to one embodiment of the present disclosure.

FIG. 12 illustrates a procedure for a terminal to perform V2X or SL communication according to a resource allocation mode according to one embodiment of the present disclosure.

Figure 13 illustrates a procedure for path switching from a direct path to an indirect path.

Figure 14 schematically illustrates how to switch from a direct route to an indirect route.

FIG. 15 and FIG. 16 are diagrams for explaining a procedure for U2U relay selection (UE-to-UE Relay Selection) without relay discovery.

Figure 17 schematically illustrates a flat protocol stack for L2 U2U relay.

Figures 18 to 22 are drawings for explaining the U2X system.

Figure 23 is a drawing for explaining how a terminal selects a relay terminal.

Figure 24 is a diagram for explaining a method for a base station to receive candidate relay information from a terminal.

Figure 25 illustrates a communication system applied to the present invention.

Figure 26 illustrates a wireless device that can be applied to the present invention.

Fig. 27 shows another example of a wireless device applied to the present invention. The wireless device can be implemented in various forms depending on the use-example/service.

Figure 28 illustrates a vehicle or autonomous vehicle to which the present invention is applied.

A wireless communication system is a multiple access system that supports communication with multiple users by sharing available system resources (e.g., bandwidth, transmission power, etc.). Examples of multiple access systems include a CDMA (code division multiple access) system, an FDMA (frequency division multiple access) system, a TDMA (time division multiple access) system, an OFDMA (orthogonal frequency division multiple access) system, an SC-FDMA (single carrier frequency division multiple access) system, and an MC-FDMA (multi carrier frequency division multiple access) system.

Sidelink refers to a communication method that establishes a direct link between user equipment (UE) to directly exchange voice or data between terminals without going through a base station (BS). Sidelink is being considered as a solution to solve the burden on base stations due to rapidly increasing data traffic.

V2X (vehicle-to-everything) refers to a communication technology that exchanges information with other vehicles, pedestrians, and objects with built-in infrastructure through wired/wireless communication. V2X can be divided into four types: V2V (vehicle-to-vehicle), V2I (vehicle-to-infrastructure), V2N (vehicle-to-network), and V2P (vehicle-to-pedestrian). V2X communication can be provided through the PC5 interface and/or the Uu interface.

Meanwhile, as more and more communication devices require greater communication capacity, there is a growing need for improved mobile broadband communication over existing Radio Access Technology (RAT). Accordingly, communication systems that consider services or terminals sensitive to reliability and latency are being discussed, and the next-generation radio access technology that considers improved mobile broadband communication, massive MTC, and URLLC (Ultra-Reliable and Low Latency Communication) can be called new RAT (new radio access technology) or NR (new radio). V2X (vehicle-to-everything) communication can also be supported in NR.

The following technology can be used in various wireless communication systems, such as CDMA (code division multiple access), FDMA (frequency division multiple access), TDMA (time division multiple access), OFDMA (orthogonal frequency division multiple access), and SC-FDMA (single carrier frequency division multiple access). CDMA can be implemented with wireless technologies such as UTRA (universal terrestrial radio access) or CDMA2000. TDMA can be implemented with wireless technologies such as GSM (global system for mobile communications)/GPRS (general packet radio service)/EDGE (enhanced data rates for GSM evolution). OFDMA can be implemented with wireless technologies such as IEEE (institute of electrical and electronics engineers) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, E-UTRA (evolved UTRA). IEEE 802.16m is an evolution of IEEE 802.16e, providing backward compatibility with systems based on IEEE 802.16e. UTRA is part of UMTS (universal mobile telecommunications system). 3GPP (3rd generation partnership project) LTE (long term evolution) is a part of E-UMTS (evolved UMTS) that uses E-UTRA (evolved-UMTS terrestrial radio access), employing OFDMA in the downlink and SC-FDMA in the uplink. LTE-A (advanced) is an evolution of 3GPP LTE.

5G NR is a new clean-slate type mobile communication system that is the successor technology to LTE-A and has the characteristics of high performance, low latency, and high availability. 5G NR can utilize all available spectrum resources, from low frequency bands below 1 GHz to intermediate frequency bands between 1 GHz and 10 GHz, and high frequency (millimeter wave) bands above 24 GHz.

For clarity of explanation, the description will focus on LTE-A or 5G NR, but the technical idea of the embodiment(s) is not limited thereto.

Figure 2 shows the structure of an applicable LTE system. This may be called an Evolved-UMTS Terrestrial Radio Access Network (E-UTRAN), or a Long Term Evolution (LTE)/LTE-A system.

Referring to FIG. 2, the E-UTRAN includes a base station (20; BS) that provides a control plane and a user plane to a terminal (10). The terminal (10) may be fixed or mobile, and may be called by other terms such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a mobile terminal (MT), a wireless device, etc. The base station (20) refers to a fixed station that communicates with the terminal (10), and may be called by other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), an access point, etc.

Base stations (20) can be connected to each other through the X2 interface. The base station (20) is connected to an EPC (Evolved Packet Core, 30) through the S1 interface, more specifically, to an MME (Mobility Management Entity) through the S1-MME and to an S-GW (Serving Gateway) through the S1-U.

EPC (30) consists of MME, S-GW, and P-GW (Packet Data Network-Gateway). MME has terminal connection information or terminal capability information, and this information is mainly used for terminal mobility management. S-GW is a gateway with E-UTRAN as an end point, and P-GW is a gateway with PDN as an end point.

The layers of the Radio Interface Protocol between the terminal and the network can be divided into L1 (the first layer), L2 (the second layer), and L3 (the third layer) based on the three lower layers of the Open System Interconnection (OSI) standard model, which is widely known in communication systems. Among these, the physical layer belonging to the first layer provides an information transfer service using a physical channel, and the RRC (Radio Resource Control) layer located in the third layer controls radio resources between the terminal and the network. To this end, the RRC layer exchanges RRC messages between the terminal and the base station.

Figure 3 shows the structure of the NR system.

Referring to FIG. 3, the NG-RAN may include a gNB and/or an eNB that provides user plane and control plane protocol termination to the UE. FIG. 7 illustrates a case where only a gNB is included. The gNB and the eNB are connected to each other via an Xn interface. The gNB and the eNB are connected to a 5th generation core network (5G Core Network: 5GC) via an NG interface. More specifically, they are connected to an access and mobility management function (AMF) via an NG-C interface, and to a user plane function (UPF) via an NG-U interface.

Figure 4 shows the structure of a radio frame of NR.

Referring to FIG. 4, a radio frame can be used in uplink and downlink transmission in NR. A radio frame has a length of 10 ms and can be defined as two 5 ms half-frames (Half-Frames, HF). A half-frame can include five 1 ms subframes (Subframes, SF). A subframe can be divided into one or more slots, and the number of slots in a subframe can be determined according to the subcarrier spacing (SCS). Each slot can include 12 or 14 OFDM (A) symbols according to the cyclic prefix (CP).

When normal CP is used, each slot can include 14 symbols. When extended CP is used, each slot can include 12 symbols. Here, the symbols can include OFDM symbols (or CP-OFDM symbols), SC-FDMA (Single Carrier - FDMA) symbols (or DFT-s-OFDM (Discrete Fourier Transform-spread-OFDM) symbols).

Table 1 below illustrates the number of symbols per slot ((N ^slot _symb ), the number of slots per frame ((N ^frame,u slot )) and the number of slots per subframe ((N ^subframe,u _{slot )} ) depending on the SCS setting (u) when normal CP is used.

SCS (15*2 ^u ) N ^slot _symb N ^frame,u _slot N ^subframe,u _slot 15KHz (u=0) 14 10 1 30KHz (u=1) 14 20 2 60KHz (u=2) 14 40 4 120KHz (u=3) 14 80 8 240KHz (u=4) 14 160 16

Table 2 illustrates the number of symbols per slot, the number of slots per frame, and the number of slots per subframe according to SCS when extended CP is used.

SCS (15*2 ^u ) N ^slot _symb N ^frame,u _slot N ^subframe,u _slot 60KHz (u=2) 12 40 4

In an NR system, OFDM(A) numerology (e.g., SCS, CP length, etc.) may be set differently between multiple cells that are merged into one terminal. Accordingly, the (absolute time) section of a time resource (e.g., subframe, slot, or TTI) (conveniently referred to as TU (Time Unit)) consisting of the same number of symbols may be set differently between the merged cells.

In NR, multiple numerologies or SCS can be supported to support various 5G services. For example, when the SCS is 15 kHz, wide area in traditional cellular bands can be supported, and when the SCS is 30 kHz/60 kHz, dense-urban, lower latency and wider carrier bandwidth can be supported. When the SCS is 60 kHz or higher, a bandwidth greater than 24.25 GHz can be supported to overcome phase noise.

The NR frequency band can be defined by two types of frequency ranges. The two types of frequency ranges can be FR1 and FR2. The numerical value of the frequency range can be changed, and for example, the two types of frequency ranges can be as shown in Table 3 below. Among the frequency ranges used in the NR system, FR1 can mean "sub 6GHz range", and FR2 can mean "above 6GHz range" and can be called millimeter wave (mmW).

Frequency Range designation Corresponding frequency range Subcarrier Spacing (SCS) FR1 450MHz - 6000MHz 15, 30, 60kHz FR2 24250MHz - 52600MHz 60, 120, 240kHz

As described above, the numerical value of the frequency range of the NR system can be changed. For example, FR1 can include a band of 410 MHz to 7125 MHz as shown in Table 4 below. That is, FR1 can include a frequency band of 6 GHz (or 5850, 5900, 5925 MHz, etc.) or higher. For example, the frequency band of 6 GHz (or 5850, 5900, 5925 MHz, etc.) or higher included in FR1 can include an unlicensed band. The unlicensed band can be used for various purposes, for example, it can be used for communication for vehicles (e.g., autonomous driving).

Frequency Range designation Corresponding frequency range Subcarrier Spacing (SCS) FR1 410MHz - 7125MHz 15, 30, 60kHz FR2 24250MHz - 52600MHz 60, 120, 240kHz

Figure 5 shows the slot structure of an NR frame.

Referring to FIG. 5, a slot includes multiple symbols in the time domain. For example, in the case of a normal CP, one slot may include 14 symbols, but in the case of an extended CP, one slot may include 12 symbols. Or, in the case of a normal CP, one slot may include 7 symbols, but in the case of an extended CP, one slot may include 6 symbols.

A carrier includes a plurality of subcarriers in the frequency domain. An RB (Resource Block) can be defined as a plurality (for example, 12) of consecutive subcarriers in the frequency domain. A BWP (Bandwidth Part) can be defined as a plurality of consecutive (P)RBs ((Physical) Resource Blocks) in the frequency domain and can correspond to one numerology (for example, SCS, CP length, etc.). A carrier can include at most N (for example, 5) BWPs. Data communication can be performed through activated BWPs. Each element can be referred to as a Resource Element (RE) in the resource grid, and one complex symbol can be mapped.

Meanwhile, the wireless interface between terminals or between terminals and a network may be composed of an L1 layer, an L2 layer, and an L3 layer. In various embodiments of the present disclosure, the L1 layer may mean a physical layer. In addition, for example, the L2 layer may mean at least one of a MAC layer, an RLC layer, a PDCP layer, and an SDAP layer. In addition, for example, the L3 layer may mean an RRC layer.

FIG. 6 illustrates a communication structure that can be provided in a 6G system according to an embodiment of the present disclosure. The embodiment of FIG. 6 can be combined with various embodiments of the present disclosure.

New network characteristics in 6G could include:

- Satellite integrated network

- Connected intelligence: Unlike previous generations of wireless communication systems, 6G is revolutionary and will update the wireless evolution from “connected things” to “connected intelligence.” AI can be applied at each stage of the communication process (or at each stage of signal processing, as described below).

- Seamless integration of wireless information and energy transfer

- Ubiquitous super 3D connectivity: Access to networks and core network functions of drones and very low Earth orbit satellites will create ubiquitous super 3D connectivity in 6G.

Some general requirements from the new network characteristics of 6G as mentioned above can be as follows:

- small cell networks

- Ultra-dense heterogeneous network

- High-capacity backhaul

- Radar technology integrated with mobile technology: High-precision localization (or location-based services) through communications is one of the functions of 6G wireless communication systems. Therefore, radar systems will be integrated with 6G networks.

- Softwarization and virtualization

Below, the core implementation technologies of the 6G system are described.

- Artificial Intelligence: Introducing AI into communications can simplify and improve real-time data transmission. AI can use a lot of analytics to determine how complex target tasks are performed. In other words, AI can increase efficiency and reduce processing delays. Time-consuming tasks such as handover, network selection, and resource scheduling can be performed instantly using AI. AI can also play a significant role in M2M, machine-to-human, and human-to-machine communications. AI can also be a rapid communication in Brain Computer Interface (BCI). AI-based communication systems can be supported by metamaterials, intelligent structures, intelligent networks, intelligent devices, intelligent cognitive radios, self-sustaining wireless networks, and machine learning.

- THz communication (terahertz communication): The data rate can be increased by increasing the bandwidth. This can be done by using sub-THz communication with wide bandwidth and applying advanced massive MIMO technology. THz waves, also known as sub-millimeter waves, generally refer to the frequency band between 0.1 THz and 10 THz with corresponding wavelengths ranging from 0.03 mm to 3 mm. The 100 GHz–300 GHz band range (Sub THz band) is considered to be the main part of the THz band for cellular communications. Adding the Sub THz band to the mmWave band will increase the capacity of 6G cellular communications. Of the defined THz bands, 300 GHz–3 THz is in the far infrared (IR) frequency band. The 300 GHz–3 THz band is part of the optical band but is at the boundary of the optical band, just behind the RF band. Therefore, this 300 GHz–3 THz band shows similarities with RF.

FIG. 7 illustrates an electromagnetic spectrum according to an embodiment of the present disclosure. The embodiment of FIG. 7 can be combined with various embodiments of the present disclosure. Key characteristics of THz communications include (i) widely available bandwidth to support very high data rates, and (ii) high path loss at high frequencies (highly directional antennas are indispensable). The narrow beam width generated by the highly directional antenna reduces interference. The small wavelength of THz signals allows a much larger number of antenna elements to be integrated into devices and BSs operating in this band. This enables the use of advanced adaptive array techniques to overcome range limitations.

- Large-scale MIMO technology

- Hologram beamforming (HBF)

- Optical wireless technology

- Free space optical transmission backhaul network (FSO backhaul network)

- Quantum communication

- Cell-free communication

- Integration of wireless information and power transmission

- Integration of wireless communication and sensing

- Integrated access and backhaul network

- Big data analysis

- Reconfigurable intelligent surface

- Metaverse

- Block-chain

- Unmanned aerial vehicles (UAV): UAVs or drones will be a crucial element in 6G wireless communications. In most cases, high-speed data wireless connectivity can be provided using UAV technology. The base station (BS) entity can be installed on the UAV to provide cellular connectivity. UAVs may have certain features not found in fixed BS infrastructure such as easy deployment, robust line-of-sight links, and freedom of movement with controlled mobility. During emergency situations such as natural disasters, deployment of terrestrial communication infrastructure is not economically feasible and sometimes cannot provide services in volatile environments. UAVs can easily handle such situations. UAVs will be a new paradigm in wireless communications. This technology facilitates three basic requirements of wireless networks namely eMBB, URLLC, and mMTC. UAVs can also support several purposes such as enhancing network connectivity, fire detection, disaster emergency services, security and surveillance, pollution monitoring, parking monitoring, and accident monitoring. Therefore, UAV technology is recognized as one of the most important technologies for 6G communications.

- Autonomous driving (self-driving): V2X (vehicle to everything), a key element of building autonomous driving infrastructure, can be a technology that allows cars to communicate and share with various elements on the road for autonomous driving, such as vehicle to vehicle (V2V) wireless communication and vehicle to infrastructure (V2I) wireless communication. In order to maximize the performance of autonomous driving and ensure high safety, fast transmission speed and low-latency technology are essential. In addition, in the future, autonomous driving may need to go beyond the level of delivering warnings or guidance messages to drivers and actively intervene in vehicle operation and directly control the vehicle in dangerous situations. To this end, the amount of information that needs to be transmitted and received may become enormous, so 6G is expected to maximize autonomous driving with faster transmission speeds and lower latency than 5G.

Fig. 8 shows a radio protocol architecture for SL communication. Specifically, Fig. 8 (a) shows a user plane protocol stack of NR, and Fig. 8 (b) shows a control plane protocol stack of NR.

Below, the SL synchronization signal (Sidelink Synchronization Signal, SLSS) and synchronization information are described.

SLSS is an SL-specific sequence and may include a Primary Sidelink Synchronization Signal (PSSS) and a Secondary Sidelink Synchronization Signal (SSSS). The PSSS may be referred to as a Sidelink Primary Synchronization Signal (S-PSS), and the SSSS may be referred to as a Sidelink Secondary Synchronization Signal (S-SSS). For example, length-127 M-sequences may be used for the S-PSS, and length-127 Gold sequences may be used for the S-SSS. For example, a terminal may detect an initial signal (signal detection) and acquire synchronization using the S-PSS. For example, the terminal may acquire detailed synchronization and detect a synchronization signal ID using the S-PSS and the S-SSS.

PSBCH (Physical Sidelink Broadcast Channel) may be a (broadcast) channel through which basic (system) information that a terminal must know first before transmitting and receiving an SL signal is transmitted. For example, the basic information may be information related to SLSS, duplex mode (DM), TDD UL/DL (Time Division Duplex Uplink/Downlink) configuration, resource pool related information, type of application related to SLSS, subframe offset, broadcast information, etc. For example, in order to evaluate PSBCH performance, in NR V2X, the payload size of PSBCH may be 56 bits including a 24-bit CRC.

S-PSS, S-SSS and PSBCH may be included in a block format supporting periodic transmission (e.g., SL SS (Synchronization Signal)/PSBCH block, hereinafter referred to as S-SSB (Sidelink-Synchronization Signal Block)). The S-SSB may have the same numerology (i.e., SCS and CP length) as the PSCCH (Physical Sidelink Control Channel)/PSSCH (Physical Sidelink Shared Channel) in a carrier, and a transmission bandwidth may be within a (pre-)configured SL BWP (Sidelink BWP). For example, the bandwidth of the S-SSB may be 11 RB (Resource Block). For example, the PSBCH may span 11 RBs. And, the frequency location of the S-SSB may be (pre-)configured. Therefore, the terminal does not need to perform hypothesis detection in frequency to discover the S-SSB in the carrier.

Meanwhile, in the NR SL system, multiple numerologies having different SCS and/or CP lengths may be supported. In this case, as the SCS increases, the length of the time resource for a transmitting terminal to transmit an S-SSB may become shorter. Accordingly, the coverage of the S-SSB may decrease. Therefore, in order to ensure the coverage of the S-SSB, the transmitting terminal may transmit one or more S-SSBs to a receiving terminal within one S-SSB transmission period according to the SCS. For example, the number of S-SSBs that the transmitting terminal transmits to the receiving terminal within one S-SSB transmission period may be pre-configured or configured for the transmitting terminal. For example, the S-SSB transmission period may be 160 ms. For example, an S-SSB transmission period of 160 ms may be supported for all SCSs.

For example, when the SCS is 15 kHz at FR1, the transmitting terminal can transmit one or two S-SSBs to the receiving terminal within one S-SSB transmission period. For example, when the SCS is 30 kHz at FR1, the transmitting terminal can transmit one or two S-SSBs to the receiving terminal within one S-SSB transmission period. For example, when the SCS is 60 kHz at FR1, the transmitting terminal can transmit one, two, or four S-SSBs to the receiving terminal within one S-SSB transmission period.

For example, when the SCS is 60 kHz at FR2, the transmitting terminal can transmit 1, 2, 4, 8, 16, or 32 S-SSBs to the receiving terminal within one S-SSB transmission period. For example, when the SCS is 120 kHz at FR2, the transmitting terminal can transmit 1, 2, 4, 8, 16, 32, or 64 S-SSBs to the receiving terminal within one S-SSB transmission period.

Meanwhile, when SCS is 60 kHz, two types of CP can be supported. In addition, the structure of the S-SSB transmitted by the transmitting terminal to the receiving terminal may be different depending on the CP type. For example, the CP type may be Normal CP (NCP) or Extended CP (ECP). Specifically, for example, when the CP type is NCP, the number of symbols to which the PSBCH is mapped in the S-SSB transmitted by the transmitting terminal may be 9 or 8. On the other hand, for example, when the CP type is ECP, the number of symbols to which the PSBCH is mapped in the S-SSB transmitted by the transmitting terminal may be 7 or 6. For example, the PSBCH may be mapped to the first symbol in the S-SSB transmitted by the transmitting terminal. For example, the receiving terminal receiving the S-SSB may perform an AGC (Automatic Gain Control) operation in the first symbol section of the S-SSB.

Figure 9 shows a terminal performing V2X or SL communication.

Referring to Fig. 9, the term terminal in V2X or SL communication may mainly mean a user's terminal. However, if a network device such as a base station transmits and receives a signal according to a communication method between terminals, the base station may also be considered a type of terminal. For example, terminal 1 may be a first device (100), and terminal 2 may be a second device (200).

For example, terminal 1 can select a resource unit corresponding to a specific resource within a resource pool, which means a set of a series of resources. Then, terminal 1 can transmit an SL signal using the resource unit. For example, terminal 2, which is a receiving terminal, can be configured with a resource pool in which terminal 1 can transmit a signal, and can detect a signal of terminal 1 within the resource pool.

Here, if terminal 1 is within the connection range of the base station, the base station can inform terminal 1 of the resource pool. On the other hand, if terminal 1 is outside the connection range of the base station, another terminal can inform terminal 1 of the resource pool, or terminal 1 can use a pre-configured resource pool.

In general, a resource pool can be composed of multiple resource units, and each terminal can select one or multiple resource units to use for its SL signal transmission.

Figure 10 shows resource units for V2X or SL communication.

Referring to Fig. 10, the entire frequency resources of the resource pool can be divided into NF units, and the entire time resources of the resource pool can be divided into NT units. Accordingly, a total of NF * NT resource units can be defined within the resource pool. Fig. 13 shows an example in which the resource pool repeats with a period of NT subframes.

As shown in Fig. 10, one resource unit (e.g., Unit #0) may appear repeatedly periodically. Or, in order to obtain a diversity effect in the time or frequency dimension, the index of the physical resource unit to which one logical resource unit is mapped may change in a pre-determined pattern over time. In the structure of such resource units, a resource pool may mean a set of resource units that a terminal that wishes to transmit an SL signal can use for transmission.

Resource pools can be subdivided into several types. For example, depending on the content of the SL signal transmitted from each resource pool, resource pools can be divided as follows.

(1) Scheduling Assignment (SA) may be a signal that includes information such as the location of resources used by a transmitting terminal for transmission of an SL data channel, MCS (Modulation and Coding Scheme) or MIMO (Multiple Input Multiple Output) transmission method required for demodulation of other data channels, and TA (Timing Advance). SA may also be transmitted multiplexed with SL data on the same resource unit, and in this case, the SA resource pool may mean a resource pool in which SA is multiplexed with SL data and transmitted. SA may also be called an SL control channel.

(2) SL data channel (Physical Sidelink Shared Channel, PSSCH) may be a resource pool used by a transmitting terminal to transmit user data. If SA is multiplexed and transmitted together with SL data on the same resource unit, only SL data channels excluding SA information may be transmitted in the resource pool for the SL data channel. In other words, REs (Resource Elements) used to transmit SA information on individual resource units within the SA resource pool may still be used to transmit SL data in the resource pool of the SL data channel. For example, a transmitting terminal may transmit PSSCH by mapping it to consecutive PRBs.

(3) The discovery channel may be a resource pool for transmitting terminals to transmit information such as their IDs. Through this, the transmitting terminals can enable adjacent terminals to discover themselves.

Even when the content of the SL signal described above is the same, different resource pools may be used depending on the transmission/reception properties of the SL signal. For example, even when it is the same SL data channel or discovery message, it may be again divided into different resource pools depending on the transmission timing determination method of the SL signal (for example, whether it is transmitted at the time of reception of a synchronization reference signal or whether it is transmitted by applying a certain timing advance at the time of reception), the resource allocation method (for example, whether the base station designates transmission resources of individual signals to individual transmitting terminals or whether individual transmitting terminals select individual signal transmission resources on their own within the resource pool), the signal format (for example, the number of symbols that each SL signal occupies in one subframe or the number of subframes used for transmission of one SL signal), the signal strength from the base station, the transmission power strength of the SL terminal, etc.

FIG. 11 illustrates an example of a BWP according to an embodiment of the present disclosure. The embodiment of FIG. 11 can be combined with various embodiments of the present disclosure. In the embodiment of FIG. 11, it is assumed that there are three BWPs.

Referring to FIG. 11, a common resource block (CRB) may be a carrier resource block numbered from one end of a carrier band to the other end. And, a PRB may be a numbered resource block within each BWP. Point A may indicate a common reference point for a resource block grid.

The BWP can be set by a point A, an offset from point A (NstartBWP) and a bandwidth (NsizeBWP). For example, point A can be an outer reference point of PRBs of a carrier where subcarrier 0 of all nucleos (e.g., all nucleosides supported by the network on that carrier) is aligned. For example, the offset can be the PRB spacing between the lowest subcarrier in a given nucleometry and point A. For example, the bandwidth can be the number of PRBs in a given nucleometry.

SLSS (Sidelink Synchronization Signal) is a SL (sidelink) specific sequence and may include PSSS (Primary Sidelink Synchronization Signal) and SSSS (Secondary Sidelink Synchronization Signal). The PSSS may be referred to as S-PSS (Sidelink Primary Synchronization Signal) and the SSSS may be referred to as S-SSS (Sidelink Secondary Synchronization Signal). For example, length-127 M-sequences may be used for S-PSS and length-127 Gold sequences may be used for S-SSS. For example, a terminal may detect an initial signal (signal detection) and obtain synchronization using S-PSS. For example, the terminal can obtain detailed synchronization using S-PSS and S-SSS and detect a synchronization signal ID.

PSBCH (Physical Sidelink Broadcast Channel) may be a (broadcast) channel through which basic (system) information that a terminal must know first before transmitting and receiving an SL signal is transmitted. For example, the basic information may be information related to SLSS, duplex mode (DM), TDD UL/DL (Time Division Duplex Uplink/Downlink) configuration, resource pool related information, type of application related to SLSS, subframe offset, broadcast information, etc. For example, in order to evaluate PSBCH performance, in NR V2X, the payload size of PSBCH may be 56 bits including a 24-bit CRC (Cyclic Redundancy Check).

S-PSS, S-SSS and PSBCH may be included in a block format supporting periodic transmission (e.g., SL SS (Synchronization Signal)/PSBCH block, hereinafter referred to as S-SSB (Sidelink-Synchronization Signal Block)). The S-SSB may have the same numerology (i.e., SCS and CP length) as the PSCCH (Physical Sidelink Control Channel)/PSSCH (Physical Sidelink Shared Channel) in a carrier, and a transmission bandwidth may be within a (pre-)configured SL BWP (Sidelink BWP). For example, the bandwidth of the S-SSB may be 11 RB (Resource Block). For example, the PSBCH may span 11 RBs. And, the frequency location of the S-SSB may be (pre-)configured. Therefore, the terminal does not need to perform hypothesis detection in frequency to discover the S-SSB in the carrier.

FIG. 12 illustrates a procedure for a terminal to perform V2X or SL communication according to a resource allocation mode according to an embodiment of the present disclosure. The embodiment of FIG. 12 can be combined with various embodiments of the present disclosure.

Referring to (a) of FIG. 12, in resource allocation mode 1, the base station can schedule SL resources to be used by the terminal for SL transmission. For example, in step S1200, the base station can transmit information related to SL resources and/or information related to UL resources to the first terminal. For example, the UL resources can include PUCCH resources and/or PUSCH resources. For example, the UL resources can be resources for reporting SL HARQ feedback to the base station.

For example, the first terminal may receive information related to a DG (dynamic grant) resource and/or information related to a CG (configured grant) resource from the base station. For example, the CG resource may include a CG type 1 resource or a CG type 2 resource. In this specification, the DG resource may be a resource that the base station configures/allocates to the first terminal via DCI (downlink control information). In this specification, the CG resource may be a (periodic) resource that the base station configures/allocates to the first terminal via DCI and/or an RRC message. For example, in case of a CG type 1 resource, the base station may transmit an RRC message including information related to the CG resource to the first terminal. For example, in case of a CG type 2 resource, the base station may transmit an RRC message including information related to the CG resource to the first terminal, and the base station may transmit DCI related to activation or release of the CG resource to the first terminal.

In step S1510, the first terminal may transmit a PSCCH (e.g., Sidelink Control Information (SCI) or 1st-stage SCI) to the second terminal based on the resource scheduling. In step S1220, the first terminal may transmit a PSSCH (e.g., 2nd-stage SCI, MAC PDU, data, etc.) related to the PSCCH to the second terminal. In step S1230, the first terminal may receive a PSFCH related to the PSCCH/PSSCH from the second terminal. For example, HARQ feedback information (e.g., NACK information or ACK information) may be received from the second terminal via the PSFCH. In step S1240, the first terminal may transmit/report HARQ feedback information to the base station via a PUCCH or a PUSCH. For example, the HARQ feedback information reported to the base station may be information generated by the first terminal based on the HARQ feedback information received from the second terminal. For example, the HARQ feedback information reported to the base station may be information generated by the first terminal based on a rule set in advance. For example, the DCI may be DCI for scheduling of SL.

Referring to (b) of FIG. 12, in resource allocation mode 2, a terminal can determine an SL transmission resource within an SL resource set by a base station/network or a preset SL resource. For example, the set SL resource or the preset SL resource may be a resource pool. For example, the terminal can autonomously select or schedule resources for SL transmission. For example, the terminal can perform SL communication by selecting a resource by itself within the set resource pool. For example, the terminal can select a resource by itself within a selection window by performing sensing and resource (re)selection procedures. For example, the sensing can be performed on a subchannel basis. For example, in step S1210, a first terminal that has selected a resource by itself within a resource pool can transmit a PSCCH (e.g., SCI (Sidelink Control Information) or 1st-stage SCI) to a second terminal using the resource. In step S1220, the first terminal can transmit a PSSCH (e.g., 2nd-stage SCI, MAC PDU, data, etc.) related to the PSCCH to the second terminal. In step S1230, the first terminal can receive a PSFCH related to the PSCCH/PSSCH from the second terminal.

Referring to (a) or (b) of FIG. 12, for example, the first terminal may transmit an SCI to the second terminal on the PSCCH. Or, for example, the first terminal may transmit two consecutive SCIs (e.g., 2-stage SCIs) to the second terminal on the PSCCH and/or the PSSCH. In this case, the second terminal may decode the two consecutive SCIs (e.g., 2-stage SCIs) to receive the PSSCH from the first terminal. In this specification, the SCI transmitted on the PSCCH may be referred to as a 1st SCI, a 1st SCI, a 1st-stage SCI, or a 1st-stage SCI format, and the SCI transmitted on the PSSCH may be referred to as a 2nd SCI, a 2nd SCI, a 2nd-stage SCI, or a 2nd-stage SCI format.

Referring to (a) or (b) of FIG. 12, in step S1530, the first terminal can receive the PSFCH. For example, the first terminal and the second terminal can determine the PSFCH resource, and the second terminal can transmit the HARQ feedback to the first terminal using the PSFCH resource.

Referring to (a) of FIG. 12, in step S1540, the first terminal may transmit SL HARQ feedback to the base station through PUCCH and/or PUSCH.

Figure 13 illustrates a procedure for path switching from a direct path to an indirect path.

The procedure illustrated in Fig. 13 is based on the connection management and path switching procedure from direct to indirect path described in the TR document (3GPP TR 38.836) related to Rel-17 NR SL. The remote UE needs to establish its own PDU session/DRB with the network before user plane data transmission.

The PC5-RRC aspect PC5 unicast link establishment procedure of Rel-16 NR V2X can be reused to establish a secure unicast link for layer 2 UE-to-Network relaying (L2 U2N relay) between the remote UE and the relay UE before the remote UE establishes a Uu RRC connection with the network via the relay UE.

For both in-coverage and out-of-coverage, when the remote UE initiates the first RRC message for connection establishment with the gNB, the PC5 L2 configuration for transmission between the remote UE and the U2N relay UE can be based on the RLC/MAC configuration defined in the standard. The establishment of Uu SRB1/SRB2 and DRB of the remote UE follows the legacy Uu configuration procedure for L2 U2N relay. The high-level connection establishment procedure illustrated in Fig. 13 applies to L2 UE-to-Network Relay.

In step S1300, the remote UE and the relay UE can perform a discovery procedure and establish a PC5-RRC connection in step S1301 based on the existing Rel-16 procedure.

In step S1302, the remote UE can transmit the first RRC message (i.e., RRCSetupRequest) to establish connection with the gNB via the Relay UE using the default L2 configuration of PC5. The gNB responds to the remote UE with an RRCSetup message (S1303). The RRCSetup delivery to the remote UE uses the default configuration of PC5. If the relay UE is not started in RRC_CONNECTED, it needs to perform its own connection establishment upon receiving the message for the default L2 configuration of PC5.

In step S1304, the gNB and the relay UE perform a relay channel setup procedure via Uu. Depending on the configuration of the gNB, the relay/remote UE sets up an RLC channel to relay SRB1 to the remote UE via PC5. This step prepares a relay channel for SRB1.

In step S1305, a remote UE SRB1 message (e.g., an RRCSetupComplete message) is transmitted to the gNB through the relay UE using the SRB1 relay channel over PC5. And the remote UE is RRC connected over Uu.

In steps S1306 and S1307, the remote UE and the gNB establish security according to legacy procedures and the security message is delivered through the Relay UE.

In steps S1308 and S1309, the gNB sends RRCReconfiguration to the remote UE through the relay UE to set up relay SRB2/DRB. The remote UE sends RRCReconfigurationComplete to the gNB through the relay UE in response.

In step S1310, the gNB sets up an additional RLC channel between the gNB and the relay UE for traffic relay. Depending on the configuration of the gNB, the relay/remote UE sets up an additional RLC channel between the remote UE and the relay UE for traffic relay.

For L2 UE-to-Network relay, in addition to the connection setup procedure:

- RRC reconfiguration and RRC disconnection procedures can reuse legacy RRC procedures with message content/configuration design left in the WI phase.

- RRC connection re-establishment and RRC connection resumption procedures can reuse existing RRC procedures as a baseline by considering the connection establishment procedure of the above L2 U2N relay to handle relay-specific parts along with message content/composition design. Message content/composition can be defined later.

Figure 14 schematically illustrates how to switch from a direct route to an indirect route.

A direct remote UE can be switched to an indirect relay UE for service continuity of L2 U2N relay based on the procedure illustrated in Fig. 14.

Referring to FIG. 14, in step S1401, the remote UE may report one or more candidate relay UEs after measuring/discovering the candidate relay UEs. The remote UE may filter appropriate relay UEs that meet upper layer criteria when reporting. The report of at least one candidate relay may include ID and SL RSRP information of the relay UE, where PC5 measurement related details may be determined later.

In step S1402, the gNB decides to switch to the target relay UE and the target (re)configuration is optionally transmitted to the relay UE (S1403).

In step S1404, the RRC reconfiguration message to the remote UE may include the ID of the target relay UE, the target Uu, and the PC5 configuration.

In step S1405, if the connection is not yet established, the remote UE establishes a PC5 connection with the target relay UE.

In step S1406, the remote UE feeds back RRCReconfigurationComplete to the gNB through the target path using the target configuration provided in RRCReconfiguration.

In step S1407, the data path is switched.

FIG. 15 and FIG. 16 are diagrams for explaining a procedure for U2U relay selection (UE-to-UE Relay Selection) without relay discovery.

For a given scenario (TR 23.752 section 6.8), when a source UE wants to communicate with a target UE, the source UE may first try to find the target UE by transmitting a Direct Communication Request or Solicitation message containing target UE information. If the source UE cannot reach the target UE directly, it will try to discover a UE-to-UE relay to reach the target UE which may also trigger the relay to discover the target UE. The source UE may integrate the discovery of the target UE and/or the discovery/selection of a U2U relay based on the following two alternatives:

- Alternative 1: U2U relay discovery/selection can be integrated into the unicast link setup procedure (see clause 6.3.3 of TS 23.287).

- Alternative 2: U2U relay discovery/selection can be integrated into the Model B direct discovery procedure.

A new field may be added to the Direct Communication Request or Solicitation message to indicate whether a relay is available for communication. The new field may be defined as Relay_indication. When a (source) UE intends to broadcast a Direct Communication Request or Solicitation message, the request message may include Relay_indication for whether a U2U relay is available. Meanwhile, for Release 17, it may be assumed that the value of Relay_indication is restricted to a single hop.

When the U2U relay receives the request message with the Relay_indication set, the U2U relay can decide whether to forward the request message (i.e., modify the message and broadcast it nearby). For example, the U2U relay can decide whether to forward the request message by considering the Application ID, authorization policy (e.g., Relay for a specific ProSe service), current traffic load of the Relay, radio status between the Source UE and the Relay UE, etc. if there is a Relay Service Code.

Alternatively, multiple U2U relays may be used to reach the target UE (case 1), or the target UE may directly receive the request message from the source UE (case 2). In this case, the target UE may choose whether to respond to either the first or the second case. For example, the target UE may choose whether to respond to either the first or the second case based on signal strength, local policy (e.g., traffic load of the UE-UE relay), relay service code (if there is a relay service code), and/or operator policy (e.g., always preferring direct communication or using only some specific UE-UE relays).

Alternatively, the source UE may receive responses to the request message from multiple U2U relays, or may receive responses to the request message directly from the target UE. In this case, the source UE may select a communication path (direct path or indirect path) based on signal strength or operator policy (e.g., always preferring direct communication or using only some specific UE-UE relays).

Specifically, the above-described alternative 1 can be performed as described in Table 5 and FIG. 15.

6.8.2 Procedures
6.8.2.1 UE-to-UE relay discovery and selection is integrated into the unicast link establishment procedure (Alternative 1)
Fig 14 illustrates the procedure of the proposed method.
0. UEs are authorized to use the service provided by the UE-to-UE relays. UE-to-UE relays are authorized to provide service of relaying traffic among UEs. The authorization and the parameter provisioning can use solutions for KI#8, eg Sol#36. The authorization can be done when UEs/relays are registered to the network. Security related parameters may be provisioned so that a UE and a relay can verify the authorization with each other if needed.
1. UE-1 wants to establish unicast communication with UE-2 and the communication can be either through direct link with UE-2 or via a UE-to-UE relay. Then UE-1 broadcasts Direct Communication Request with relay_indication enabled. The message will be received by relay-1, relay-2. The message may also be received by UE-2 if it is in the proximity of UE-1. UE-1 includes source UE info, target UE info, Application ID, as well as Relay Service Code if there is any. If UE-1 does not want relay to be involved in the communication, then it will made relay_indication disabled.
NOTE 1: The data type of relay_indication can be determined in Stage 3. Details of Direct Communication Request/Accept messages will be determined in stage 3.
2. Relay-1 and relay-2 decide to participate in the procedure. They broadcast a new Direct Communication Request message in their proximity without relay_indication enabled. If a relay receives this message, it will just drop it. When a relay broadcasts the Direct Communication Request message, it includes source UE info, target UE info and Relay UE info (eg Relay UE ID) in the message and use Relay's L2 address as the source Layer-2 ID. The Relay maintains association between the source UE information (eg source UE L2 ID) and the new Direct Communication Request.
3. UE-2 receives the Direct Communication Requests from relay-1 and relay-2. UE-2 may also receive Direct Communication Request message directly from the UE-1 if the UE-2 is in the communication range of UE-1.
4. UE-2 chooses relay-1 and replies with Direct Communication Accept message. If UE-2 directly receives the Direct Communication Request from UE-1, it may choose to setup a direct communication link by sending the Direct Communication Accept message directly to UE-1. After receiving Direct Communication Accept, a UE-to-UE relay retrieves the source UE information stored in step 2 and sends the Direct Communication Accept message to the source UE with its Relay UE info added in the message.
After step 4, UE-1 and UE-2 have respectively setup the PC5 links with the chosen UE-to-UE relay.
NOTE 2: The security establishment between the UE1 and Relay-1, and between Relay-1 and UE-2 are performed before the Relay-1 and UE-2 send Direct Communication Accept message. Details of the authentication/security establishment procedure are determined by SA WG3. The security establishment procedure can be skipped if there already exists a PC5 link between the source (or target) UE and the relay which can be used for relaying the traffic.
5. UE-1 receives the Direct Communication Accept message from relay-1. UE-1 chooses path according to eg policies (eg always choose direct path if it is possible), signal strength, etc. If UE-1 receives Direct Communication Accept / Response message request accept directly from UE-2, it may choose to setup a direct PC5 L2 link with UE-2 as described in clause 6.3.3 of TS 23.287 [5], then step 6 is skipped.
6a. For the L3 UE-to-UE Relay case, UE-1 and UE-2 finish setting up the communication link via the chosen UE-to-UE relay. The link setup information may vary depending on the type of relay, eg L2 or L3 relaying. Then UE-1 and UE-2 can communicate via the relay. Regarding IP address allocation for the source/remote UE, the addresses can be either assigned by the relay or by the UE itself (eg link-local IP address) as defined in clause 6.3.3 of TS 23.287 [5].
6b. For the Layer 2 UE-to-UE Relay case, the source and target UE can setup an end-to-end PC5 link via the relay. UE-1 sends a unicast E2E Direct Communication Request message to UE-2 via the Relay-1, and UE-2 responds with a unicast E2E Direct Communication Accept message to UE-1 via the Relay-1. Relay-1 transfers the messages based on the identity information of UE-1/UE-2 in the Adaptation Layer.
NOTE 3: How Relay-1 can transfer the messages based on the identity information of UE-1/UE-2 in the Adaptation Layer requires cooperation with RAN2 during the normative phase.
NOTE 4: In order to make a relay or path selection, the source UE can setup a timer after sending out the Direct Communication Request for collecting the corresponding response messages before making a decision. Similarly, the target UE can also setup a timer after receiving the first copy of the Direct Communication Request / message for collecting multiple copies of the message from different paths before making a decision.
NOTE 5: In the first time when a UE receives a message from a UE-to-UE relay, the UE needs to verify if the relay is authorized to be a UE-to-UE relay. Similarly, the UE-to-UE relay may also need to verify if the UE is authorized to use the relay service. The verification details and the how to secure the communication between two UEs through a UE-to-UE relay is to be defined by SA WG3.

Alternative 2 described above can be performed as described in Table 6 and Fig. 16.

6.8.2.2 UE-to-UE relay discovery and selection is integrated into Model B direct discovery procedure (Alternative 2)
Depicted in Fig 15 is the procedure for UE-UE Relay discovery Model B, and the discovery/selection procedure is separated from hop by hop and end-to-end link establishment.
1. UE-1 broadcasts discovery solicitation message carrying UE-1 info, target UE info (UE-2), Application ID, Relay Service Code if any, the UE-1 can also indicate relay_indication enabled.
2. On reception of discovery solicitation, the candidate Relay UE-R broadcasts discovery solicitation carrying UE-1 info, UE-R info, Target UE info. The Relay UE-R uses Relay's L2 address as the source Layer-2 ID.
3. The target UE-2 responds the discovery message. If the UE-2 receives discovery solicitation message in step 1, then UE-2 responds discovery response in step 3b with UE-1 info, UE-2 info. If not and UE-2 receives discovery solicitation in step 2, then UE-2 responds discovery response message in step 3a with UE-1 info, UE-R info, UE-2 info.
4. On reception of discovery response in step 3a, UE-R sends discovery response with UE-1 info, UE-R info, UE-2 info. If more than one candidate Relay UEs responding discovery response message, UE-1 can select one Relay UE based on eg implementation or link qualification.
5. The source and target UE may need to setup PC5 links with the relay before communicating with each other. Step 5a can be skipped if there already exists a PC5 link between the UE-1 and UE-R which can be used for relaying. Step 5b can be skipped if there already exists a PC5 link between the UE-2 and UE-R which can be used for relaying.
6a. Same as step 6a described in clause 6.8.2.1.
6b. For the Layer-2 UE-to-UE Relay, the E2E unicast Direct Communication Request message is sent from UE1 to the selected Relay via the per-hop link (established in steps 5a) and the Adaptation layer info identifying the peer UE (UE3 ) as the destination. The UE-to-UE Relay transfers the E2E messages based on the identity information of peer UE in the Adaptation Layer. The initiator (UE1) knows the Adaptation layer info identifying the peer UE (UE3) after a discovery procedure. UE3 responds with E2E unicast Direct Communication Accept message in the same way.
NOTE 1: For the Layer 2 UE-to-UE Relay case, whether step5b is performed before step 6b or triggered during step 6b will be decided at normative phase.
NOTE 2: How Relay-1 can transfer the messages based on the identity information of UE-1/UE-2 in the Adaptation Layer requires cooperation with RAN2 during the normative phase.
6.8.3 Impacts on services, entities and interfaces
UE impacts to support new Relay related functions.

Figure 17(a) schematically illustrates a flat protocol stack for L2 U2U relay.

Fig. 17(a) illustrates a user plane protocol stack for an L2 U2U relay, and Fig. 17(b) illustrates a control plane protocol stack for an L2 U2U relay. Table 7 below provides a description related to Fig. 17 regarding the Architecture and Protocol Stack of a Layer-2 Relay.

5.5 Layer-2 Relay
5.5.1 Architecture and Protocol Stack
For L2 UE-to-UE Relay architecture, the protocol stacks are similar to L2 UE-to-Network Relay other than the fact that the termination points are two Remote UEs. The protocol stacks for the user plane and control plane of L2 UE-to-UE Relay architecture are described in Figure 5.5.1-1 and Figure 5.5.1-2.
An adaptation layer is supported over the second PC5 link (ie the PC5 link between Relay UE and Destination UE) for L2 UE-to-UE Relay. For L2 UE-to-UE Relay, the adaptation layer is put over RLC sublayer for both CP and UP over the second PC5 link. The sidelink SDAP/PDCP and RRC are terminated between two Remote UEs, while RLC, MAC and PHY are terminated in each PC5 link.
For the first hop of L2 UE-to-UE Relay,
- The N:1 mapping is supported by first hop PC5 adaptation layer between Remote UE SL Radio Bearers and first hop PC5 RLC channels for relaying.
- The adaptation layer over first PC5 hop between Source Remote UE and Relay UE supports to identify traffic destined to different Destination Remote UEs.
For the second hop of L2 UE-to-UE Relay,
- The second hop PC5 adaptation layer can be used to support bearer mapping between the ingress RLC channels over first PC5 hop and egress RLC channels over second PC5 hop at Relay UE.
- PC5 Adaptation layer supports the N:1 bearer mapping between multiple ingress PC5 RLC channels over first PC5 hop and one egress PC5 RLC channel over second PC5 hop and supports the Remote UE identification function.
For L2 UE-to-UE Relay,
- The identity information of Remote UE end-to-end Radio Bearer is included in the adaptation layer in first and second PC5 hop.
- In addition, the identity information of Source Remote UE and/or the identity information of Destination Remote UE are candidate information to be included in the adaptation layer, which are to be decided in WI phase.

Below, we detail U2X for broadcast remote ID and direct DAA (Detect-and-Avoid) support over PC5 (see TR 23.700-58).

UAV (Unmanned Aerial Vehicle)-to-everything (U2X)

Figures 18 to 22 are drawings for explaining the U2X system.

The key points of the proposed U2X solution for the given scenario (TR 23.700-58) are as follows:

- U2X can support BRID and Direct DAA by leveraging the V2X mechanism defined in TS 23.287. In this case, both LTE PC5 and NR PC5 defined in TS 23.285 are supported and RAT selection can be performed based on U2XP.

- Communication mode: BRID (Broadcasting UAV identification) can use Broadcast communication mode. DAA can use Broadcast communication mode to advertise UAV information. Broadcast over PC5 or Unicast over PC5 can be used between two or more UAVs for DAA de-collision. Unicast over Uu over U2X AS may not be supported in the above-described U2X solution. Groupcast mode for NR based PC5 may not be supported in the above-described U2X solution. When NR PC5 is selected, connectionless Groupcast communication can be used for DAA. Meanwhile, application layer managed Groupcast may not be considered in this release due to lack of clear requirement.

- U2X can be supported in a U2X Application Server that interfaces with the operator network via NEF, as is the case with V2X Application Servers.

Meanwhile, the above given scenario/solution needs to allow for multiple deployment scenarios where a dedicated service set can be defined and where the U2X AS and USS providing the UAV are the same or different entities.

- U2X policy (U2XP) can be defined to provide configuration parameters to UE for U2X communication via PC5 reference point or Uu reference point. The configuration parameters can be preset in ME (Mobile Equipment), set in UICC (universal IC card), pre-set in ME and set in UICC, provided/updated by U2X application server via PCF (policy control function) and/or V1 reference point, or provided/updated to UE by PCF. Here, UE needs to consider the U2X policies in priority order: provided/updated by PCF, provided/updated by U2X application server via V1 reference point, configured in UICC, and pre-configured in ME. De-conflicting policy can be a policy indicating communication mode for de-confliction (unicast or broadcast), communication frequency for de-confliction, etc.

- As with V2X, the Tx profile or NR Tx profile can be determined based on the U2XP mapping of the U2X service type.

- Both UAVs with UICC and UAVs without UICC (i.e. not subscribed to MNO) can be supported. Here, UAVs without UICC can perform U2X communication only if they are approved as “Not provided in E-UTRA” and “Not provided in NR”.

- U2X communication parameters of the U2X application server or PCF can be transmitted via the UAV-C UE.

- In addition to the existing parameters for V2X, the radio parameters for PC5 RAT (e.g. LTE PC5, NR PC5) can be set such as geographical area, altitude restriction and validity timer. Such additional information/parameters may be required to control PC5 usage policy-wise based on the specific location of the UAV.

- Definition of DAA/UAV service types may go beyond the scope of the given scenarios described above.

- For UAVs with UICC, the use of PC5-based communications for BRID and DAA requires successful UUAA authentication/authorization as defined in TS 23.256 and authorization via U2XP. However, the FAA does not require specific authorization for the use of PC5 for BRID or DAA. For UAVs without UICC, the use of PC5-based communications for BRID and DAA can only be authorized via U2XP. Meanwhile, U2X services can be identified by one of the ITS Application Identifier (ITS-AID), the Provider Service Identifier (PSID), or the Application Identifier (AID), depending on values specifically defined for airborne applications.

- As in TS 23.287, security for broadcast U2X communications over the PC5 reference point can be supported in U2X application layer schemes developed in other SDOs.

Referring to FIG. 18, a non-roaming 5G system architecture for U2X communication via PC5 can be configured as illustrated in FIG. 18. Here, the non-roaming 5G system architecture for U2X communication via PC5 can be applied with the reference point of TS 23.287, and may have the following differences.

- U2X1: As a reference point between the U2X application of UE and UAV-C and U2X application server, this reference point may be outside the scope of the above given scenario.

- U2X5: As a reference point between U2X applications within the UE, this reference point may/may not be specified in the release of a given scenario.

- N1: In addition to the relevant functions defined in TS 23.501 for N1, it can also be used to convey U2X policies and parameters (including service authorization) from AMF to UE for U2X services, and PC5 functions for U2X capabilities and U2X information from UE to AMF.

- N2: In addition to the relevant functions defined in TS 23.501 for N2, it can also be used to convey U2X policies and parameters (including service authorization) from AMF to NG-RAN for U2X services.

- The above solution can support UAV UEs leveraging Uu connectivity and UAV UEs not leveraging Uu connectivity (i.e., Uu capable or non-Uu capable UAV UEs). UAVs not leveraging Uu capabilities can use U2X for BRID and DAA and can be configured over U2X1 for transmissions outside the scope of 3GPP. On the other hand, UAV UEs without leveraging Uu capabilities can be part of the 3GPP ecosystem as they use U2X1 for configuration by U2X application server and implement PC5 connectivity as specified by 3GPP.

A roaming 5G system architecture for U2X communications over PC5 can be configured as illustrated in FIGS. 19 and 20. Specifically, FIG. 19 illustrates a roaming 5G system architecture for U2X communications over PC5 in a local breakout scenario, and FIG. 20 illustrates a roaming 5G system architecture for U2X communications over PC5 in a home routing scenario.

A 5G system architecture between Public Land Mobile Networks (PLMNs) for U2X communications over PC5 reference points could be as follows.

- For inter-PLMN U2X communication via PC5 reference point, PC5 parameters need to be set in a consistent manner between UEs within a specific area.

- The architecture for inter-PLMN PC5 may be similar to that defined in the non-roaming 5G system architecture for U2X communication over PC5 described with reference to Fig. 18.

AF-based service parameter provisioning for U2X communication can be defined as follows.

- As defined in TS 23.287, a 5G system may provide NEF services to enable communication between a PLMN's NF and a U2X application server. Specifically, a high level view of AF-based service parameter provisioning for U2X communication may be illustrated as illustrated in Fig. 21. The service parameters may also be pre-configured in the UAV using methods outside the scope of 3GPP (e.g., when not utilizing Uu functionality).

In a U2X scenario, the following may be considered:

- Usage/Usage of U2X for BRID: The message content for BRID can be defined according to regional regulations for BRID (e.g. message sets of ASTM F3411.19 or ASD-STAN prEN 4709-002 P1) and optionally according to regional means in compliance documents.

- Usage/Usage of U2X for DAA: Message content for DAA is defined by local regulations for DAA and may go beyond the scope of the given scenarios described above.

The procedures and mechanisms of TS 23.287 can be applied to U2X scenarios. Specifically, the procedure for broadcasting over PC5 for DAA collision resolution can be performed as shown in Fig. 22. Meanwhile, the procedure for broadcasting over PC5 for DAA collision resolution can be assumed that the UAV is provisioned with a U2X policy including a DAA collision resolution policy (e.g., unicast or broadcast communication for collision resolution, communication frequency).

Specifically, the procedure for broadcasting through PC5 for DAA collision resolution according to Fig. 22 can be performed as follows.

1. UAV1 may receive a broadcast message from UAV2, which may include application layer DAA payload (e.g., CAA level UAV ID, USS address of UAV2, speed, heading, position, etc.).

- Note 1: The Unmanned aerial system Traffic Management (UTM) Service Supplier address (USS) is not required if UAV-to-UAV collisions are resolved locally, but may be required if USS coordination of the UAVs involved in the collision is required.

2. UAV1 can deliver the DAA payload to the upper layer. The application layer can detect collisions by comparing its own trajectory and position with the broadcast message received from UAV2. When the application layer of UAV1 detects a collision, collision avoidance/collision resolution procedures can be initiated with UAV2.

3. Optionally, UAV1 can notify its USS (UTM Service Supplier) about the detected collision, including the ID of peer UAV 2.

4. UAV1 can select a communication mode (broadcast or unicast) for DAA de-collision based on inputs received from the application layer and DAA policy. If the broadcast de-collision method is selected, the following messages can be exchanged between UAVs.

5. UAV1 broadcasts a message (e.g., PC5-S message) (e.g., de-collision request message), which is part of the U2X functionality and may include DAA functionality indicating whether the UAV can participate in communication for protocol, DAA de-collision policy (broadcast based, de-collision message frequency), collision detection warning, ID of other UAVs detected in collision different from that of the corresponding CAA level UAV ID, and certain parameters (e.g., de-collision information) (e.g., trajectory correction information to avoid collision). (UAV1 broadcasts a message (e.g. PC5-S message), e.g. deconfliction request message and may include DAA capability, which is part of U2X capability and indicates whether the UAV is able to engage in communication for deconflicting protocol, DAA deconflicting policy (broadcast based, deconflicting message frequency), collision detection alert, its CAA-level UAV IDs and the one(s) from other detected conflicting UAV(s), and deconflicting specific parameters (e.g. trajectory correction information to avoid collision))

6. UAV2 may broadcast a message (e.g., PC5-S message) to provide the agreed upon DAA conflict resolution policy, updated trajectory, and other information (e.g., message conflict resolution status response, conflict resolution warning, CAA-level UAV ID of participating UAV from receiving UAV). Subsequent broadcast messages may be exchanged between UAVs until traffic conflict resolution (e.g., mutual position/trajectory monitoring) is reached, depending on the agreed upon message frequency.

The impact on services, entities, and interfaces related to the U2X described above may be as shown in Tables 8 and 9 below.

1. UE: In addition to the functions defined in TS 23.501, the UE may support the following functions:
- Report the U2X Capability (including DAA Capability) and PC5 Capability for U2X to 5GC over N1 reference point.
- Indicate U2X Policy Provisioning Request in UE Policy Container for UE triggered U2X Policy provisioning.
- Receive the U2X parameters from 5GC over N1 reference point.
- Procedures for U2X communication over PC5 reference point.
- Configuration of parameters for U2X communication. These parameters can be pre-configured in the UE, or, if in coverage, provisioned or updated by signaling over the N1 reference point from the PCF in the HPLMN or over U2X1 reference point from the U2X Application Server.
2. AMF: In addition to the functions defined in TS 23.501, the AMF performs the following functions:
- Obtain from UDM the subscription information related to U2X and store them as part of the UE context data.
- Select a PCF supporting U2X Policy/Parameter provisioning and report the PC5 Capability for U2X to the selected PCF.
- Obtain from PCF the PC5 QoS information related to U2X and store it as part of the UE context data.
- Provision the NG-RAN with indication about the UE authorization status about U2X communication over PC5 reference point.
- Provision the NG-RAN with PC5 QoS parameters related to U2X communication.
- PCF: In addition to the functions defined in TS 23.501, the PCF includes the functions described in 23.287 to provision the UE and AMF with necessary parameters in order to use U2X communication.
- UDM: Subscription management for U2X communication over PC5 reference point. The UE subscription data types are extended according to the following table 6.
3. U2X Application Server: implements a subset of the V2X AS functionality specified in TS 23.287:
- includes AF functionality, and may support at least the following capabilities:
- For U2X service parameters provisioning, the U2X AS provides the 5GC and the UAV UE (possibly via the UAVC) with parameters for U2X communications over PC5 and Uu reference points.
- UDR: In addition to the functions defined in TS 23.501, the UDR stores U2X service parameters.
- NRF: In addition to the functions defined in TS 23.501, the NRF performs PCF discovery by considering U2X capability.
- NEF: for U2X AS, the NEF supports U2X service parameters.

U2X Subscription data NR U2X Services Authorization Indicates whether the UE is authorized to use the NR sidelink for U2X services as UAV UE, UAV-C UE, or Authority UE. LTE U2X Services Authorization Indicates whether the UE is authorized to use the LTE sidelink for U2X services as UAV UE, UAV-C UE, or Authority UE. NR UE-PC5-AMBR AMBR of UE's NR sidelink (i.e. PC5) communication for U2X services. LTE UE-PC5-AMBR AMBR of UE's LTE sidelink (i.e. PC5) communication for U2X services.

Additionally, the recently discussed issues related to the above-mentioned given scenario are as shown in Table 10 below.

Measurement Reporting
- Use LTE principle as a baseline, introduce similar event H1 (aerial UE height become higher than threshold) and H2 (aerial UE height become lower than threshold. FFS if further NR enhancements are needed. FFS study scaling of RRM parameters (eg which parameters and what is the purpose/benefit of the scaling and how)
-- FFS how to limit excessive measurements and measurement reporting.
-- FFS if user consent is needed for location reporting in CONNECTED
-- FFS study the vertical movement and associated mobility for UAV UEs
- Rel-18 NR supports reporting of UAV UE's height, location and velocity. It is for further study what accuracy and reporting mechanisms are required and if further enhancements are needed.
- As in LTE, flight path plan reporting will be introduced. Location list of waypoints (3D location information) and timestamp is adopted as the basic content of flight path report. FFS if timestamp is mandatory or optional for NR. FFS if further enhancements are needed.
- Introduce similar functionality to LTE (numberofTriggeringCells). FFS whether numberoftriggerbeams for NR is required or other enhancements. FFS study how to avoid sending the measurement reports mainly due to reportOnLeave.
- A waypoint is a planned location for the UE along the flight path and is described via the existing parameter type LocationCoordinates defined in TS 37.355.
- A timestamp provides the UTC time associated with estimated time of arrival to a waypoint as baseline. FFS on granularity.
- No requirements are placed on spatial distribution of waypoints.
- A UE indicates whether flight plan information is available within the RRCReconfigurationComplete, RRCReestablishmentComplete, RRCResumeComplete, or RRCSetupComplete message. Flight path reporting uses at the UE Information request/response procedure as baseline.
- UE indicates to the network a new flight path is available in the UE (whether it is initial or update). Then, reuse the normal request/response procedure of flight path report.
- UAI message can also be used to indicate the UE has flight path availability.
- FFS whether and what triggering conditions are specified for flight update. FFS The maximum number of waypoints within flight path plan is left FFS.
- When event H1 or H2 triggers, the content of the measurement report is configurable by the network (ie it can contain UAV UEs height, location information and/or RSRP/RSRQ measurement results). FFS whether UAV UE's height is mandatorily reported and which parameter/IE is used for height reporting
- Joint use of height-dependent condition and RSRP/RSRQ/SINR-based condition for measurement report triggering is supported in NR Rel-18 UAV. The combination of existing events will be used.
- Height-dependent parameter scaling is not supported as a part of Rel-18 NR
- Do not extend the Number of triggering cells mechanism to apply to the inter-RAT scenario, ie event B1 and B2 triggering.
- Do not restrict the applicability of Number of triggering cells mechanism to FR1 only. In other words, the Number of triggering cells mechanism is applicable to FR1 and FR2 (up to network configuration).
- The UE shall not ignore or bypass the Number of triggering cells mechanism, once configured.
- Do not introduce the use of a "numberOfTriggeringBeams" mechanism.
- Do not introduce an alternative mechanism to the Number of triggering cells mechanism.
- Do not introduce an additional mechanism based on Number of changed cells.
- For the purpose of interference control (ie for number of trigger cells), do not introduce a prohibit timer mechanism.
- Report on leave is not triggered by a cell that was not previously included in the measurement report for the number of triggering cell.
- Support configuring height-dependent more-than-one configurations targeting measurement and measurement reporting enhancement. UE applies corresponding configuration based on the UE height. The proposed solutions should aim at avoiding RAN4 impacts. FFS how this would be configured (ie different MO configurations or different parameters FFS Exact parameters and details.
- Height-dependent more-than-one configurations is supported on parameter/field level (ie different fields/values within the same MO) where different values (or value ranges) of the parameter/field applies to different height or height range.
- For MO configuration parameters: at least the following will have ability to be configured with height-dependent more-than-one configurations/values, each for a specific height region: SSB-ToMeasure. Details on how to specify is FFS. FFS on UE behavior on L1 and L3 measurement.
- For MR configuration parameters: at least the following will have ability to be configured with height-dependent more-than-one configurations/values, each for a specific height region: Event A4 threshold and numberoftriggeringcells. Details on how to specify is FFS (ie maybe it can be by combination of events).
- When height-dependent more-than-one configurations are provided, UE applies the new value once it moves to new height (or height range) similar to the case of RRC reconfiguration. Need Codes, field descriptions, etc. as in legacy specifications apply.
- If a height-specific value is not explicitly configured for certain height, whether to keep using the value that was used or consider the parameter as released (ie parameter/value not applicable at this height) should be looked into case by case, and can be clarified by need code, field description, or procedural text as needed. FFS details.

Below, we describe in detail the criteria that can be used when a UAV UE selects a relay UE.

Candidate Relay UE Selection Method for UAV Remote UE

A UAV remote UE may be required to select a UAV relay UE based on criteria different from those used by a general remote UE to select a relay UE. Here, the relay UE selected by the UAV remote UE may be a UAV UE or another UE. Hereinafter, for convenience of explanation, a UE selected by the UAV remote UE for relay communication is described as a UAV relay UE or relay UE.

A UAV UE may (periodically) report its flight path to a base station (and/or a Core Network; CN) (as specified for UAV UE). Here, the flight path value may be a navigation value of the UAV, and may include values related to the expected path along which the UAV UE will reach the destination.

When the UAV remote UE reports the L2 ID of the candidate relay UE to the base station, the base station can compare (in terms of direction, speed, height, position, etc.) the flight path of the candidate relay UE with the flight path of the UAV remote UE. In this case, the base station can select a relay UE having a similar flight path to the flight path of the UAV remote UE, and establish a (SL) connection between the UAV relay UE and the selected relay UE. To this end, the candidate relay UE needs to report the L2 source ID used when transmitting the discovery message to the base station (here, all relay UEs may be assumed to be in RRC CONNECTED state).

Alternatively, the UAV remote UE may report/select only candidate relay UEs having similar flight paths. For example, the UAV remote UE may select and report to the base station a candidate relay UE having a flight path that is within a predetermined offset in terms of direction, speed, height, position, etc. from its own flight path. To this end, the candidate relay UE may transmit a discovery message including its own flight path. However, since a security issue may arise when all flight paths are shared, the candidate relay UE may share only a part of its flight paths via the discovery message. For example, the candidate relay UE may be configured to share only a few way points from its current location via the discovery message, or may be configured to share only a flight path within a predetermined time unit (e.g., a flight path within a few seconds/minutes) via the discovery message. When information about such a flight path is included in a discovery message, the UAV remote UE can compare its own flight path value with the value of the flight path included in the discovery message, select at least one relay UE whose flight path value is within a preset offset as a candidate relay UE as a result of the comparison, and report the selected candidate relay UE to the base station.

Alternatively, the UAV remote UE may be configured to have a different number of candidate relay UEs to report/select depending on its height (and/or height range). For example, as the altitude of the UAV remote UE increases, the signal strength from the gNB may decrease and interference caused by signals from other gNBs may increase. In this case, the UAV remote UE may need to connect to one or more relay UEs (or multiple relay UEs) when it is above a certain altitude. Therefore, the UAV remote UE needs to have a different number of relay UEs to report/select depending on its height/altitude.

Alternatively, the gNB may be configured with a height (and/or height range) of selectable relay UEs by the UAV remote UE. For example, the (serving) gNB of the UAV remote UE may configure a height range to be reported as a candidate relay UE. In this case, the UAV remote UE may select only relay UEs existing within the corresponding height range as candidate relay UEs and report them to the (serving) gNB. This is because the gNB can easily determine a height range of candidate relay UEs that are deemed suitable to operate as a (serving) relay UE from the height of the current remote UE. This allows the coverage extension effect via the relay UE to be maximized.

Alternatively, whether the UAV remote UE operates as a remote UE and/or whether the UAV relay UE operates as a relay UE may be configured differently depending on the height range. For example, the UAV remote UE may be allowed to operate as a remote UE when it is located within a (configured) specific height range. Or, the UAV remote UE may be allowed to operate as a remote UE when it is outside the specific height range. The UAV relay UE may also be allowed to operate as a relay UE when it is located within a (configured) specific height range, or may be allowed to operate as a relay UE when it is outside the specific height range.

Alternatively, when the UAV remote UE drives in a cluster, the UAV remote UE may select a relay UE only within the cluster. In this case, the discovery message transmitted by the candidate relay UE may further include an ID that may indicate the cluster. The UAV remote UE belonging to the same cluster may select only candidate relay UEs having the same cluster ID, or the selection/reporting operation of the relay UE may be restricted/limited so that the relay UE reports the selected candidate relay UE to the base station.

Alternatively, when the UAV remote UE selects a candidate relay UE, the UAV remote UE may be limited to selecting a candidate relay UE in which the signal strength (SD-RSRP/SL-RSRP) between itself and the relay UE is equal to or greater than a predetermined threshold strength. And/or, the UAV remote UE may select only relay UEs existing in a specific area as candidate relay UEs. For example, the UAV remote UE may report/select only relay UEs belonging to a specific radius (/3D space) based on its position value as candidate relay UEs. Alternatively, a specific (3D location) area from which candidate relay UEs can be selected may be set for the UAV remote UE, and the UAV remote UE may select candidate relay UEs only from among relay UEs belonging to the set specific area. This may be to allow low-power operation of the remote UE through relay communication to be performed only in the specific area by separately setting/designating a specific area in which the relay UE exists.

Alternatively, the UAV remote UE may report at least one candidate relay UE to its serving base station. In this case, the base station may select one of the reported at least one candidate relay UE, and configure the remote UE to establish an SL connection/relay connection with the selected one. Alternatively, the UAV remote UE may establish an SL connection/relay with one relay UE that satisfies a predetermined criterion among the at least one candidate relay UE, and establish a connection (i.e., an indirect link) with the base station through the one relay UE to transmit and receive messages with the base station.

In this way, the proposed invention can ensure that the UAV remote UE performs relay communication more effectively by defining criteria for selecting a relay UE by a UAV remote UE that takes into account the characteristics of the UAV that are different from those of existing remote UEs on the ground.

Meanwhile, it is obvious that the relay UE in the above-described proposed invention can be expanded to include gNB, IAB-node, etc.

Figure 23 is a drawing for explaining how a terminal selects a relay terminal.

Referring to FIG. 23, the terminal may receive relay setting information for performing relay communication through a relay terminal from a base station (S231). Here, the terminal and the relay terminal may be a UAV (Unmanned Aerial Vehicle) terminal, which is a non-terrestrial terminal, as described in “Candidate Relay UE Selection Method for UAV Remote UE”. That is, the terminal may be a terminal moving at a certain altitude or higher, unlike a ground terminal, and the relay setting information may include settings for selection criteria that are different from a selection method of an existing relay terminal.

Next, the terminal may receive discovery messages from a plurality of relay terminals (S233). Here, the discovery message may include at least one of identification information of the relay terminal, cluster information to which the relay terminal belongs, a flight path of the relay terminal, altitude/height information of the relay terminal, and location information of the relay terminal.

Alternatively, the terminal may determine whether to receive the discovery message for relay communication based on the configuration information. For example, the relay configuration information may further include information on an allowance condition under which the remote terminal is permitted to perform an operation. Here, the allowance condition may be information on a specific height range. For example, the terminal may perform an operation of receiving the discovery message/signal for the relay communication when its own height is located within the specific height range. Alternatively, if the relay configuration information further includes information on a specific height range to which the relay communication is restricted, the terminal may perform an operation of receiving the discovery message/signal for the relay communication only when it is not located within the specific height range.

Alternatively, the relay configuration information may further include information on a specific height range within which the operation of the relay terminal is permitted. In this case, the terminal may operate as a relay terminal only when located within the specific height range. For example, the terminal may transmit the discovery message only when located within the specific height range. Alternatively, the relay configuration information may further include information on a specific height range within which the operation of the relay terminal is restricted. In this case, a terminal that is not located within the specific height range may perform an operation of transmitting a discovery signal/message for the relay communication.

Next, the terminal can select a candidate relay terminal from among the plurality of relay terminals based on the plurality of discovery messages received from the plurality of relay terminals and the relay configuration information (S235).

At this time, the terminal may select the candidate relay terminals based on criteria different from the relay selection criteria of the existing ground terminals. For example, the terminal may determine the number of candidate relay terminals to be selected from the plurality of relay terminals based on its own height and the relay configuration information. For example, the relay configuration information may include information for setting the number of candidate relay terminals that the terminal needs to select for relay communication by height or height range. In this case, the terminal may select the candidate relay terminals at least a first number set for the height/height range corresponding to its own height based on the relay configuration information. For example, the configuration information may be set to select K (integer) candidate relay terminals for the first height or the first height range, and to select N (integer) candidate relay terminals for the second height or the second height range. In this case, when the height/altitude of the terminal falls within the first height or the first height range, the terminal may select K or more candidate relay terminals from the plurality of relay terminals (i.e., selection/reporting of at least K candidate relay terminals is required). That is, the terminal determines the number of candidate relay terminals to be selected based on its own height/altitude and the setting information, and can select candidate relay terminals equal to the number of candidate relay terminals determined. Meanwhile, when the first height or the first height range is higher than the second height or the second height range, the K may be a larger value than the N. This is because, as the height of the terminal increases, the communication environment with the base station relatively deteriorates more, and therefore, it is necessary to form a link for relay communication with more relay terminals. For example, the relay setting information may set the number of candidate relay terminals to be selected differently for each height/height range.

Alternatively, the relay configuration information may further include condition information on a selection condition of the relay terminal. For example, the relay configuration information may include a selection allowable height range from which the terminal may select the candidate relay terminal. In this case, the terminal may select only a relay terminal located within the selection allowable height range among the plurality of relay terminals as a candidate relay terminal based on the discovery message. Alternatively, the relay configuration information may include a selection allowable height range determined based on height information reported by the terminal. That is, the base station may determine a height range of a relay terminal suitable for relay communication based on the height of the terminal, and provide relay configuration information including the height range to the terminal.

Alternatively, the terminal may select a candidate relay terminal from among the plurality of relay terminals by considering information about the flight path included in the discovery message. For example, the relay configuration information may include preset offset information related to the flight path, and the terminal may select a relay terminal having a flight path (direction, speed, height, position, etc.) within its own flight path and the preset offset range as the candidate relay terminal from among the plurality of relay terminals. Meanwhile, the flight path included in the discovery message may be a flight path within a preset time unit by considering security issues.

Alternatively, the terminal may select a candidate relay terminal from among the plurality of relay terminals based on the cluster information included in the discovery message. For example, the terminal may select only a relay terminal within the same cluster as the cluster to which it belongs from among the plurality of relay terminals as the candidate relay terminal.

Meanwhile, the selection of the above-described candidate relay terminal may be a selection operation based on the assumption that a discovery message is received above a certain threshold intensity.

Alternatively, the terminal may report candidate relay terminal information for the selected candidate relay terminal to the base station. For example, the terminal may report candidate relay terminal information for a first number of candidate relay terminals according to the relay configuration information among the plurality of relay terminals to the base station. That is, the number of candidate relay terminals to be reported by the terminal may also be determined as the first number according to the number of heights or height ranges included in the relay configuration information. In this case, the terminal may receive selection information for a second number of candidate relay terminals selected by the base station from the first number of candidate relay terminals. The terminal may perform configuration for forming an indirect link with each of the second number of candidate relay terminals. That is, the terminal may form a second number of indirect links (i.e., links connected to the base station through SL connections with relay terminals) with each of the second number of relay terminals. Here, the second number may correspond to or be smaller than the first number. At this time, as described above, the second number may also be determined to a different value depending on the height of the terminal. For example, the second number may be determined to a relatively higher value as the height of the terminal is higher.

Figure 24 is a diagram for explaining a method for a base station to receive candidate relay information from a terminal.

Referring to FIG. 24, the base station can transmit relay configuration information related to relay communication to the terminal (S241). Here, the relay configuration information can include configuration information related to a criterion for selecting a relay terminal by a UAV (Unmanned Aerial Vehicle) terminal, which is a non-terrestrial terminal, as described with reference to the "Candidate Relay UE Selection Method for UAV Remote UE" and FIG. 23. At this time, the relay configuration information can set a criterion different from the criterion for selecting a relay terminal by an existing terrestrial remote terminal for relay communication as described above. For example, the relay configuration information can set a different number of candidate relay terminals to be selected/reported as the candidate relay information according to the height/height range of the terminal.

Next, the base station can receive candidate relay information for a first number or more of candidate relay terminals selected from among the plurality of relay terminals (S243). As described with reference to “Candidate Relay UE Selection Method for UAV Remote UE” and FIG. 16, the first number can be determined based on the height of the terminal and the relay configuration information. For example, the first number can be determined to be a larger value as the height of the terminal increases.

Next, the base station may select at least one relay terminal to perform relay communication from among the first number or more candidate relay terminals, and transmit information about the selected at least one terminal to the terminal (S245). For example, the base station may comprehensively consider the flight path, height, location, etc. of each of the first number or more candidate relay terminals included in the candidate relay information, and select at least one relay terminal to perform relay communication from among the first number or more candidate relay terminals. Meanwhile, the number of the at least one relay terminal may vary depending on the height of the terminal. For example, if the height of the terminal is lower than a specific threshold height, the base station may select one relay terminal as the relay terminal for the relay communication, and if the height of the terminal is higher than a specific threshold height, the base station may select two relay terminals as the relay terminals for the relay communication. This is because the communication environment with the base station may become worse as the height of the terminal is higher, and therefore, the base station may set up a relay connection to the terminal through two or more relay terminals for smoother communication with the terminal.

In this way, the proposed invention can provide a selection/reporting opportunity for a relay terminal suitable for the characteristics of a UAV by presenting selection/reporting criteria for a relay terminal related to a UAV. Alternatively, the proposed invention can ensure stable communication with a base station through relay communication even in a communication environment where the signal strength of the base station decreases and interference increases due to an increase in the height of the terminal by increasing the number of candidate relay terminals requiring reporting/selection as the height of the terminal increases. Alternatively, the proposed invention can effectively support low-power communication using relay communication even at high altitudes/heights by setting up relay communication considering the characteristics of the UAV.

How to set local ID in multi-hop U2U operation

In order for an intermediate relay UE to know that the final destination of a message transmitted from a source remote UE in a multi-hop U2U relay operation is the target remote UE, the target remote UE's ID must be included in the message. In addition, in order for the target remote UE to know where the message was generated and transmitted when the target remote UE receives the message, the source remote UE's ID must be included in the message. That is, in multi-hop transmission, the message transmitted by the source remote UE must include the source remote UE ID and the target remote UE ID. The included ID can be the L2 ID. However, if the L2 ID is used as it is, a total of 48 bits of header are required for each MAC PDU transmission, which may cause an overhead problem. To solve this problem, a local ID smaller than the L2 ID can be used to identify the source remote UE and the target remote UE.

The local ID may be a value that the source remote UE (/target remote UE) assigns as a local ID a value that can identify the L2 IDs of the source remote UE and the target remote UE, and assigns a unique value to the intermediate relay UE. When the source remote UE performs (initial) SL configuration (e.g., RRCReconfigurationSidelink / RRCReconfigurationCompleteSidelink) to the relay UE for the 1st-hop, the source remote UE may configure a local ID that can identify the source remote UE and a local ID that can identify the target remote UE. The corresponding values may be included in the RRCReconfigurationSidelink message. Since this value is a value to indicate a mapping relationship between the L2 IDs of the source/target remote UE and the local ID that identifies the source/target remote UE, the L2 IDs of the source/target remote UE and the corresponding local ID may need to be notified together. The relay UE receiving this transmits the corresponding value as it is to the relay UE of the next hop so that the relay UE of the next hop or the local ID value that identifies the source remote UE and the target remote UE can be known. The corresponding local ID value can be a value that is used unchanged when passing through each relay UE from the source remote UE to the target remote UE. Similarly to the above, the target remote UE can also perform local ID allocation. If the target remote UE performs it, the corresponding value can be included and transmitted in the RRCReconfigurationCompleteSidelink message. In this case, the corresponding value can mean the source remote UE (L2) ID, the target remote UE (L2) ID, and/or the local ID value mapped to the source/target pair.

Local ID can be configured by the UE (/source remote UE/relay UE) for SL connection establishment to the relay UE (or) target remote UE (/connected link) to which it is connected. (The values configured by the source remote UE/relay UE of each hop can be different in HbH (hop-by-hop).)

Alternatively, an (initial) SL configuration message (e.g., RRCReconfigurationSidelink) that the source remote UE configures to the 1st-hop relay UE may be configured with (a) value for identifying a message to be transmitted from the source remote UE to the target remote UE. The message (/SL configuration message) may include an L2 ID of the source remote UE, an L2 ID of the target remote UE, and a local ID for indicating a pair of these. The relay UE receiving the message may similarly configure (a) value (/local ID) for identifying a message to be transmitted from the source remote UE to the target remote UE, to the next relay UE heading to the target remote UE, and the value may be different (or the same) as the previous hop (e.g., the local ID value that the source remote UE configured to the 1st-hop relay UE). That is, the value may be determined by the relay UE configuring the next hop. Even when a relay UE allocates a local ID to the next relay UE, the L2 ID value of the source remote UE, the L2 ID value of the target remote UE, and a local ID value representing a pair of them may be included so that the assigned relay UE can allocate a local ID of the next hop. The value may be a value included only in the initial SL configuration message (e.g., RRCReconfigurationSidelink).

For example, if a {source remote UE (L2 ID), target remote UE (L2 ID)} pair is assigned to one local ID (A) value, the assigned relay UE can assign the same {source remote UE, target remote UE} pair to the relay UE of the next hop with the same/different local ID (B) value. (A and B can be the same value). After SL connection establishment is completed, when transmitting data (/signal), if the adaptation layer of the data transmitted by the source remote UE is included and transmitted, the 1st-hop relay UE that receives this can replace the local ID of the message with the local ID (B) and transmit it to the relay UE of the next hop. Likewise, the 2nd-hop relay UE that receives this can know from which source remote UE the message is transmitted to which target remote UE by receiving the local ID (B) (through the initial SL connection establishment process), and can transmit the message to the target remote UE by including its own assigned local ID (C) in the local ID field of the adaptation layer. When the message is transmitted to the target remote UE in this way, the target remote UE can identify which source remote UE initially transmitted the message through the header value of the adaptation layer of the message.

Alternatively, the initial SL connection establishment message (/RRCReconfigurationSidelink, RRCReconfigurationCompleteSidelink) may be transmitted without an adaptation layer header (since no local ID is allocated yet), or with a special value (0000 /11111) indicating a non-used value in the Local ID field of the adaptation layer header. In this case, an implicit convention may be established that each relay UE/source remote UE excludes the special value (00000 / 1111) from the Local ID value it allocates.

A case may be considered where the relay UE sets a local ID and notifies the previous hop of the corresponding value. Specifically, a method may be used where the relay UE allocates a local ID to be used for itself and the previous hop and notifies the relay UE/source remote UE of the previous hop of the same local ID. In this case, the local ID values allocated by each relay UE may be the same/different values for the same source remote UE (L2) ID, target remote UE (L2) ID pair. If the relay UE allocates a local ID to the relay UE/source remote UE of the previous hop, RRCReconfigurationCompleteSidelink or a separate PC5-RRC message may be used. In addition, if the relay UE allocates a local ID to the previous hop, it may be necessary to notify local ID information for the source remote UE (L2) ID, the target remote UE (L2) ID, and their pair values together.

Alternatively, if the source remote UE/relay UE has allocated a local ID for the next hop, (or) the relay UE, the target remote UE has allocated a local ID for the previous hop, and if a local ID is given, the adaptation layer can include the local ID value when transmitting data and signaling information to the corresponding hop. The relay UE and the target remote UE that receive this know which source remote UE (L2) ID and target remote UE (L2) ID the local ID is mapped to, and thus can determine where the message is headed and from which remote UE the message is sent.

Alternatively, if two different relay UEs (relay UE (A), relay UE (B)) allocate the same local ID for different source remote UE (L2) IDs, target remote UE (L2) IDs to one same next hop relay UE (relay UE (C)), the relay UE receiving it can filter the local ID using the L2 ID of the relay UE that allocates it. For example, if the relay UE (C) stores the local IDs for the source remote UE, the target remote UE and their pair, it may also store the L2 ID of the relay UE (/source remote UE) that allocates it. Even if different relay UEs allocate the same local ID, it is possible to identify the local IDs for different source/target remote UE pairs using the L2 ID of the relay UE (/source remote UE) that allocates it.

Examples of communication systems to which the invention applies

Although not limited thereto, the various descriptions, functions, procedures, proposals, methods and/or operational flowcharts of the present invention disclosed in this document may be applied to various fields requiring wireless communication/connectivity (e.g., 5G) between devices.

Hereinafter, more specific examples will be provided with reference to the drawings. In the drawings/descriptions below, the same drawing symbols may illustrate identical or corresponding hardware blocks, software blocks, or functional blocks, unless otherwise described.

Figure 25 illustrates a communication system applied to the present invention.

Referring to FIG. 25, a communication system (1) applied to the present invention includes a wireless device, a base station, and a network. Here, the wireless device means a device that performs communication using a wireless access technology (e.g., 5G NR (New RAT), LTE (Long Term Evolution)) and may be referred to as a communication/wireless/5G device. Although not limited thereto, the wireless device may include a robot (100a), a vehicle (100b-1, 100b-2), an XR (eXtended Reality) device (100c), a hand-held device (100d), a home appliance (100e), an IoT (Internet of Thing) device (100f), and an AI device/server (400). For example, the vehicle may include a vehicle equipped with a wireless communication function, an autonomous vehicle, a vehicle capable of performing vehicle-to-vehicle communication, etc. Here, the vehicle may include a UAV (Unmanned Aerial Vehicle) (e.g., a drone). XR devices include AR (Augmented Reality)/VR (Virtual Reality)/MR (Mixed Reality) devices and can be implemented in the form of HMD (Head-Mounted Device), HUD (Head-Up Display) installed in a vehicle, television, smartphone, computer, wearable device, home appliance, digital signage, vehicle, robot, etc. Portable devices can include smartphone, smart pad, wearable device (e.g., smart watch, smart glass), computer (e.g., laptop, etc.). Home appliances can include TV, refrigerator, washing machine, etc. IoT devices can include sensors, smart meters, etc. For example, base stations and networks can also be implemented as wireless devices, and a specific wireless device (200a) can act as a base station/network node to other wireless devices.

Wireless devices (100a to 100f) can be connected to a network (300) via a base station (200). Artificial Intelligence (AI) technology can be applied to the wireless devices (100a to 100f), and the wireless devices (100a to 100f) can be connected to an AI server (400) via the network (300). The network (300) can be configured using a 3G network, a 4G (e.g., LTE) network, a 5G (e.g., NR) network, etc. The wireless devices (100a to 100f) can communicate with each other via the base station (200)/network (300), but can also communicate directly (e.g., sidelink communication) without going through the base station/network. For example, vehicles (100b-1, 100b-2) can communicate directly (e.g. V2V (Vehicle to Vehicle)/V2X (Vehicle to everything) communication). Also, IoT devices (e.g., sensors) can communicate directly with other IoT devices (e.g., sensors) or other wireless devices (100a to 100f).

Wireless communication/connection (150a, 150b, 150c) can be established between wireless devices (100a to 100f)/base stations (200), and base stations (200)/base stations (200). Here, the wireless communication/connection can be achieved through various wireless access technologies (e.g., 5G NR) such as uplink/downlink communication (150a), sidelink communication (150b) (or, D2D communication), and communication between base stations (150c) (e.g., relay, IAB (Integrated Access Backhaul). Through the wireless communication/connection (150a, 150b, 150c), a wireless device and a base station/wireless device, and a base station and a base station can transmit/receive wireless signals to/from each other. For example, the wireless communication/connection (150a, 150b, 150c) can transmit/receive signals through various physical channels. To this end, at least some of various configuration information setting processes for transmitting/receiving wireless signals, various signal processing processes (e.g., channel encoding/decoding, modulation/demodulation, resource mapping/demapping, etc.), and resource allocation processes can be performed based on various proposals of the present invention.

Examples of wireless devices to which the present invention is applied

Figure 26 illustrates a wireless device that can be applied to the present invention.

Referring to FIG. 26, the first wireless device (100) and the second wireless device (200) can transmit and receive wireless signals through various wireless access technologies (e.g., LTE, NR). Here, {the first wireless device (100), the second wireless device (200)} can correspond to {the wireless device (100x), the base station (200)} and/or {the wireless device (100x), the wireless device (100x)} of FIG. 25.

A first wireless device (100) includes one or more processors (102) and one or more memories (104), and may additionally include one or more transceivers (106) and/or one or more antennas (108). The processor (102) controls the memory (104) and/or the transceiver (106), and may be configured to implement the descriptions, functions, procedures, suggestions, methods, and/or operational flowcharts disclosed in this document. For example, the processor (102) may process information in the memory (104) to generate first information/signal, and then transmit a wireless signal including the first information/signal via the transceiver (106). Additionally, the processor (102) may receive a wireless signal including second information/signal via the transceiver (106), and then store information obtained from signal processing of the second information/signal in the memory (104). The memory (104) may be connected to the processor (102) and may store various information related to the operation of the processor (102). For example, the memory (104) may perform some or all of the processes controlled by the processor (102), or may store software codes including instructions for performing the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document. Here, the processor (102) and the memory (104) may be part of a communication modem/circuit/chipset designed to implement wireless communication technology (e.g., LTE, NR). The transceiver (106) may be connected to the processor (102) and may transmit and/or receive wireless signals via one or more antennas (108). The transceiver (106) may include a transmitter and/or a receiver. The transceiver (106) may be used interchangeably with an RF (Radio Frequency) unit. In the present invention, a wireless device may also mean a communication modem/circuit/chipset.

Specifically, the first wireless device or terminal (100) may include a processor (102) and a memory (104) connected to a transceiver (106). The memory (104) may include at least one program capable of performing operations related to the embodiments described in FIGS. 23, 24 and “Candidate Relay UE Selection Method for UAV Remote UE.”

The processor (102) controls the transceiver (106) to receive configuration information related to relay communication, receive discovery messages from a plurality of relay terminals, and select a first or more number of candidate relay terminals for the relay communication from among the plurality of relay terminals based on the discovery messages and the configuration information. Here, the first number can be determined based on the height of the terminal and the configuration information.

Alternatively, a processing device including a processor (102) and a memory (104) may be configured. In this case, at least one processor; and at least one memory connected to the at least one processor and storing instructions, wherein the instructions, based on being executed by the at least one processor, cause the terminal to: receive configuration information related to relay communication, receive discovery messages from a plurality of relay terminals, and select a first or more number of candidate relay terminals for the relay communication from among the plurality of relay terminals based on the discovery messages and the configuration information. Here, the first number may be determined based on a height of the terminal and the configuration information.

The second wireless device (200) includes one or more processors (202), one or more memories (204), and may additionally include one or more transceivers (206) and/or one or more antennas (208). The processor (202) may be configured to control the memories (204) and/or the transceivers (206), and implement the descriptions, functions, procedures, suggestions, methods, and/or operational flowcharts disclosed in this document. For example, the processor (202) may process information in the memory (204) to generate third information/signals, and then transmit a wireless signal including the third information/signals via the transceivers (206). Additionally, the processor (202) may receive a wireless signal including fourth information/signals via the transceivers (206), and then store information obtained from signal processing of the fourth information/signals in the memory (204). The memory (204) may be connected to the processor (202) and may store various information related to the operation of the processor (202). For example, the memory (204) may perform some or all of the processes controlled by the processor (202), or may store software codes including commands for performing the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document. Here, the processor (202) and the memory (204) may be part of a communication modem/circuit/chip designed to implement wireless communication technology (e.g., LTE, NR). The transceiver (206) may be connected to the processor (202) and may transmit and/or receive wireless signals via one or more antennas (208). The transceiver (206) may include a transmitter and/or a receiver. The transceiver (206) may be used interchangeably with an RF unit. In the present invention, a wireless device may also mean a communication modem/circuit/chip.

Specifically, the second wireless device or base station (200) may include a processor (202) and a memory (204) coupled to a transceiver or RF transceiver (206). The memory (204) may include at least one program capable of performing operations related to the embodiments described in FIGS. 23, 24 and “Candidate Relay UE Selection Method for UAV Remote UE.”

The processor (202) controls the transceiver (206) to transmit configuration information related to relay communication, receive candidate relay information for a first or more number of candidate relay terminals selected from among the plurality of relay terminals, select at least one relay terminal to perform relay communication from among the first or more number of candidate relay terminals, and transmit information about the at least one selected terminal to the terminal. Here, the first number can be determined based on the height of the terminal and the configuration information.

Hereinafter, hardware elements of the wireless device (100, 200) will be described in more detail. Although not limited thereto, one or more protocol layers may be implemented by one or more processors (102, 202). For example, one or more processors (102, 202) may implement one or more layers (e.g., functional layers such as PHY, MAC, RLC, PDCP, RRC, SDAP). One or more processors (102, 202) may generate one or more Protocol Data Units (PDUs) and/or one or more Service Data Units (SDUs) according to the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document. One or more processors (102, 202) may generate messages, control information, data, or information according to the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document. One or more processors (102, 202) can generate signals (e.g., baseband signals) including PDUs, SDUs, messages, control information, data or information according to the functions, procedures, suggestions and/or methodologies disclosed herein and provide the signals to one or more transceivers (106, 206). One or more processors (102, 202) can receive signals (e.g., baseband signals) from one or more transceivers (106, 206) and obtain PDUs, SDUs, messages, control information, data or information according to the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed herein.

The one or more processors (102, 202) may be referred to as a controller, a microcontroller, a microprocessor, or a microcomputer. The one or more processors (102, 202) may be implemented by hardware, firmware, software, or a combination thereof. For example, one or more Application Specific Integrated Circuits (ASICs), one or more Digital Signal Processors (DSPs), one or more Digital Signal Processing Devices (DSPDs), one or more Programmable Logic Devices (PLDs), or one or more Field Programmable Gate Arrays (FPGAs) may be included in the one or more processors (102, 202). The descriptions, functions, procedures, suggestions, methods, and/or operational flowcharts disclosed in this document may be implemented using firmware or software, and the firmware or software may be implemented to include modules, procedures, functions, etc. The descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in this document may be implemented using firmware or software configured to perform one or more of the following: included in one or more processors (102, 202), or stored in one or more memories (104, 204) and driven by one or more of the processors (102, 202). The descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in this document may be implemented using firmware or software in the form of codes, instructions and/or sets of instructions.

One or more memories (104, 204) may be coupled to one or more processors (102, 202) and may store various forms of data, signals, messages, information, programs, codes, instructions and/or commands. The one or more memories (104, 204) may be comprised of ROM, RAM, EPROM, flash memory, hard drives, registers, cache memory, computer readable storage media and/or combinations thereof. The one or more memories (104, 204) may be located internally and/or externally to the one or more processors (102, 202). Additionally, the one or more memories (104, 204) may be coupled to the one or more processors (102, 202) via various technologies, such as wired or wireless connections.

One or more transceivers (106, 206) can transmit user data, control information, wireless signals/channels, etc., as described in the methods and/or flowcharts of this document, to one or more other devices. One or more transceivers (106, 206) can receive user data, control information, wireless signals/channels, etc., as described in the descriptions, functions, procedures, suggestions, methods and/or flowcharts of this document, from one or more other devices. For example, one or more transceivers (106, 206) can be coupled to one or more processors (102, 202) and can transmit and receive wireless signals. For example, one or more processors (102, 202) can control one or more transceivers (106, 206) to transmit user data, control information, or wireless signals to one or more other devices. Additionally, one or more processors (102, 202) may control one or more transceivers (106, 206) to receive user data, control information, or wireless signals from one or more other devices. Additionally, one or more transceivers (106, 206) may be coupled to one or more antennas (108, 208), and one or more transceivers (106, 206) may be configured to transmit and receive user data, control information, wireless signals/channels, and the like, as described in the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed herein, via one or more antennas (108, 208). In this document, one or more antennas may be multiple physical antennas, or multiple logical antennas (e.g., antenna ports). One or more transceivers (106, 206) may convert received user data, control information, wireless signals/channels, etc. from RF band signals to baseband signals in order to process the received user data, control information, wireless signals/channels, etc. using one or more processors (102, 202). One or more transceivers (106, 206) may convert processed user data, control information, wireless signals/channels, etc. from baseband signals to RF band signals using one or more processors (102, 202). For this purpose, one or more transceivers (106, 206) may include an (analog) oscillator and/or filter.

Examples of wireless devices to which the present invention is applied

Fig. 27 shows another example of a wireless device applied to the present invention. The wireless device can be implemented in various forms depending on the use-example/service (see Fig. 25).

Referring to FIG. 27, the wireless device (100, 200) corresponds to the wireless device (100, 200) of FIG. 26 and may be composed of various elements, components, units/units, and/or modules. For example, the wireless device (100, 200) may include a communication unit (110), a control unit (120), a memory unit (130), and an additional element (140). The communication unit may include a communication circuit (112) and a transceiver(s) (114). For example, the communication circuit (112) may include one or more processors (102, 202) and/or one or more memories (104, 204) of FIG. 27. For example, the transceiver(s) (114) may include one or more transceivers (106, 206) and/or one or more antennas (108, 208) of FIG. 26. The control unit (120) is electrically connected to the communication unit (110), the memory unit (130), and the additional elements (140) and controls overall operations of the wireless device. For example, the control unit (120) may control electrical/mechanical operations of the wireless device based on programs/codes/commands/information stored in the memory unit (130). In addition, the control unit (120) may transmit information stored in the memory unit (130) to an external device (e.g., another communication device) via a wireless/wired interface through the communication unit (110), or may store information received from an external device (e.g., another communication device) via a wireless/wired interface in the memory unit (130).

The additional element (140) may be configured in various ways depending on the type of the wireless device. For example, the additional element (140) may include at least one of a power unit/battery, an input/output unit (I/O unit), a driving unit, and a computing unit. Although not limited thereto, the wireless device may be implemented in the form of a robot (FIG. 25, 100a), a vehicle (FIG. 25, 100b-1, 100b-2), an XR device (FIG. 25, 100c), a portable device (FIG. 25, 100d), a home appliance (FIG. 25, 100e), an IoT device (FIG. 25, 100f), a digital broadcasting terminal, a hologram device, a public safety device, an MTC device, a medical device, a fintech device (or a financial device), a security device, a climate/environmental device, an AI server/device (FIG. 25, 400), a base station (FIG. 25, 200), a network node, etc. Wireless devices may be mobile or stationary, depending on the use/service.

In FIG. 27, various elements, components, units/parts, and/or modules within the wireless device (100, 200) may be entirely interconnected via a wired interface, or at least some may be wirelessly connected via a communication unit (110). For example, within the wireless device (100, 200), the control unit (120) and the communication unit (110) may be wired, and the control unit (120) and the first unit (e.g., 130, 140) may be wirelessly connected via the communication unit (110). In addition, each element, component, unit/part, and/or module within the wireless device (100, 200) may further include one or more elements. For example, the control unit (120) may be composed of one or more processor sets. For example, the control unit (120) may be composed of a set of a communication control processor, an application processor, an electronic control unit (ECU), a graphic processing processor, a memory control processor, etc. As another example, the memory unit (130) may be composed of RAM (Random Access Memory), DRAM (Dynamic RAM), ROM (Read Only Memory), flash memory, volatile memory, non-volatile memory, and/or a combination thereof.

Examples of vehicles or autonomous vehicles to which the present invention is applied

Fig. 28 illustrates a vehicle or autonomous vehicle applied to the present invention. The vehicle or autonomous vehicle may be implemented as a mobile robot, a car, a train, a manned/unmanned aerial vehicle (AV), a ship, etc.

Referring to FIG. 28, a vehicle or autonomous vehicle (100) may include an antenna unit (108), a communication unit (110), a control unit (120), a driving unit (140a), a power supply unit (140b), a sensor unit (140c), and an autonomous driving unit (140d). The antenna unit (108) may be configured as a part of the communication unit (110). Blocks 110/130/140a to 140d correspond to blocks 110/130/140 of FIG. 27, respectively.

The communication unit (110) can transmit and receive signals (e.g., data, control signals, etc.) with external devices such as other vehicles, base stations (e.g., base stations, road side units, etc.), servers, etc. The control unit (120) can control elements of the vehicle or autonomous vehicle (100) to perform various operations. The control unit (120) can include an ECU (Electronic Control Unit). The drive unit (140a) can drive the vehicle or autonomous vehicle (100) on the ground. The drive unit (140a) can include an engine, a motor, a power train, wheels, brakes, a steering device, etc. The power supply unit (140b) supplies power to the vehicle or autonomous vehicle (100) and can include a wired/wireless charging circuit, a battery, etc. The sensor unit (140c) can obtain vehicle status, surrounding environment information, user information, etc. The sensor unit (140c) may include an IMU (inertial measurement unit) sensor, a collision sensor, a wheel sensor, a speed sensor, an incline sensor, a weight detection sensor, a heading sensor, a position module, a vehicle forward/backward sensor, a battery sensor, a fuel sensor, a tire sensor, a steering sensor, a temperature sensor, a humidity sensor, an ultrasonic sensor, a light sensor, a pedal position sensor, etc. The autonomous driving unit (140d) may implement a technology for maintaining a driving lane, a technology for automatically controlling speed such as adaptive cruise control, a technology for automatically driving along a set path, a technology for automatically setting a path and driving when a destination is set, etc.

For example, the communication unit (110) can receive map data, traffic information data, etc. from an external server. The autonomous driving unit (140d) can generate an autonomous driving route and a driving plan based on the acquired data. The control unit (120) can control the driving unit (140a) so that the vehicle or autonomous vehicle (100) moves along the autonomous driving route according to the driving plan (e.g., speed/direction control). During autonomous driving, the communication unit (110) can irregularly/periodically acquire the latest traffic information data from an external server and can acquire surrounding traffic information data from surrounding vehicles. In addition, the sensor unit (140c) can acquire vehicle status and surrounding environment information during autonomous driving. The autonomous driving unit (140d) can update the autonomous driving route and driving plan based on the newly acquired data/information. The communication unit (110) can transmit information on the vehicle location, autonomous driving route, driving plan, etc. to an external server. External servers can predict traffic information data in advance using AI technology, etc. based on information collected from vehicles or autonomous vehicles, and provide the predicted traffic information data to vehicles or autonomous vehicles.

Here, the wireless communication technology implemented in the wireless device (XXX, YYY) of the present specification may include LTE, NR, and 6G, as well as Narrowband Internet of Things for low-power communication. At this time, for example, NB-IoT technology may be an example of LPWAN (Low Power Wide Area Network) technology, and may be implemented with standards such as LTE Cat NB1 and/or LTE Cat NB2, and is not limited to the above-described names. Additionally or alternatively, the wireless communication technology implemented in the wireless device (XXX, YYY) of the present specification may perform communication based on LTE-M technology. At this time, for example, LTE-M technology may be an example of LPWAN technology, and may be called by various names such as eMTC (enhanced Machine Type Communication). For example, the LTE-M technology can be implemented by at least one of various standards such as 1) LTE CAT 0, 2) LTE Cat M1, 3) LTE Cat M2, 4) LTE non-BL (non-Bandwidth Limited), 5) LTE-MTC, 6) LTE Machine Type Communication, and/or 7) LTE M, and is not limited to the above-described names. Additionally or alternatively, the wireless communication technology implemented in the wireless device (XXX, YYY) of the present specification can include at least one of ZigBee, Bluetooth, and Low Power Wide Area Network (LPWAN) considering low-power communication, and is not limited to the above-described names. For example, the ZigBee technology can create PAN (personal area networks) related to small/low-power digital communication based on various standards such as IEEE 802.15.4, and can be called by various names.

The embodiments described above are combinations of components and features of the present invention in a predetermined form. Each component or feature should be considered optional unless explicitly stated otherwise. Each component or feature may be implemented in a form that is not combined with other components or features. In addition, it is also possible to form an embodiment of the present invention by combining some components and/or features. The order of operations described in the embodiments of the present invention may be changed. Some components or features of one embodiment may be included in another embodiment, or may be replaced with corresponding components or features of another embodiment. It is obvious that claims that do not have an explicit citation relationship in the scope of the patent may be combined to form an embodiment or included as a new claim by post-application amendment.

In this document, the embodiments of the present invention have been mainly described with a focus on the signal transmission/reception relationship between a terminal and a base station. This transmission/reception relationship is equally/similarly extended to signal transmission/reception between a terminal and a relay or a base station and a relay. A specific operation described as being performed by a base station in this document may, in some cases, be performed by its upper node. That is, it is obvious that various operations performed for communication with a terminal in a network composed of a plurality of network nodes including a base station may be performed by the base station or other network nodes other than the base station. The base station may be replaced with terms such as a fixed station, a Node B, an eNode B (eNB), an access point, etc. In addition, the terminal may be replaced with terms such as a UE (User Equipment), an MS (Mobile Station), an MSS (Mobile Subscriber Station), etc.

Embodiments according to the present invention can be implemented by various means, for example, hardware, firmware, software, or a combination thereof. In case of implementation by hardware, an embodiment of the present invention can be implemented by one or more ASICs (application specific integrated circuits), DSPs (digital signal processors), DSPDs (digital signal processing devices), PLDs (programmable logic devices), FPGAs (field programmable gate arrays), processors, controllers, microcontrollers, microprocessors, etc.

In the case of implementation by firmware or software, one embodiment of the present invention may be implemented in the form of a module, procedure, function, etc. that performs the functions or operations described above. The software code may be stored in a memory unit and may be driven by a processor. The memory unit may be located inside or outside the processor and may exchange data with the processor by various means already known.

It will be apparent to those skilled in the art that the present invention can be embodied in other specific forms without departing from the scope of the present invention. Therefore, the above detailed description should not be construed as limiting in all aspects, but should be considered as illustrative. The scope of the present invention should be determined by a reasonable interpretation of the appended claims, and all changes within the equivalent scope of the present invention are included in the scope of the present invention.

The embodiments of the present invention as described above can be applied to various mobile communication systems.

Claims (15)

In a method for a terminal to select a candidate relay terminal in a wireless communication system, A step for receiving setup information related to relay communication; A step of receiving discovery messages from multiple relay terminals; and A step of selecting at least a first number of candidate relay terminals for the relay communication among the plurality of relay terminals based on the discovery messages and the setting information, A method wherein the first number is determined based on the height of the terminal and the setting information. In the first paragraph, A method, characterized in that the first number is determined differently for each height range based on the setting information. In the first paragraph, A method, characterized in that the discovery message includes information about the flight path. In the third paragraph, A method, characterized in that the above candidate relay terminal is a relay terminal among the plurality of relay terminals having a flight path within a predetermined error range with respect to the flight path of the terminal. In the first paragraph, A method, characterized in that the above candidate relay terminal is a relay terminal located within a selection allowable height range set by the above setting information among the plurality of relay terminals. In the first paragraph, A method characterized in that an operation related to selection of the candidate relay terminal is performed based on the height of the terminal falling within a specific height range included in the setting information. In the first paragraph, A method, characterized in that it further comprises a step of reporting information about candidate relay terminals of the first number or more to a base station. In the first paragraph, A method, characterized in that the terminal forms a second or more number of wireless links for the relay communication based on the selected candidate relay terminal. In Article 8, A method, characterized in that the second number is determined based on the setting information and the height of the terminal. In the first paragraph, A method, characterized in that the terminal is a UAV (Unmanned Aerial Vehicle) remote terminal. A computer-readable recording medium having recorded thereon a program for performing the method described in claim 1. In a terminal for selecting a candidate relay terminal in a wireless communication system, RF(Radio Frequency) transceiver; and comprising a processor connected to the RF transceiver; The processor controls the RF transceiver to receive configuration information related to relay communication, receives discovery messages from a plurality of relay terminals, and selects a first or more number of candidate relay terminals for the relay communication from among the plurality of relay terminals based on the discovery messages and the configuration information. A terminal, wherein the first number is determined based on the height of the terminal and the setting information. In a processing device for controlling a terminal for selecting a candidate relay terminal in a wireless communication system, at least one processor; and At least one memory coupled to said at least one processor and storing instructions, said instructions being executed by said at least one processor, wherein said terminal causes: Receives configuration information related to relay communication, receives discovery messages from a plurality of relay terminals, and selects at least a first number of candidate relay terminals for the relay communication from among the plurality of relay terminals based on the discovery messages and the configuration information. A processing device, wherein the first number is determined based on the height of the terminal and the setting information. In a method for a base station to receive candidate relay information from a terminal in a wireless communication system, A step of transmitting setup information related to relay communication to the above terminal; A step of receiving candidate relay information for a first or more number of candidate relay terminals selected from among the plurality of relay terminals; and A step of selecting at least one relay terminal to perform relay communication among the candidate relay terminals of the first number or more, and transmitting information about the at least one selected terminal to the terminal, A method wherein the first number is determined based on the height of the terminal and the setting information. In a base station that receives candidate relay information from a terminal in a wireless communication system, RF(Radio Frequency) transceiver; and comprising a processor connected to the RF transceiver; The processor controls the RF transceiver to transmit setting information related to relay communication, receives candidate relay information for a first or more number of candidate relay terminals selected from among the plurality of relay terminals, selects at least one relay terminal to perform relay communication from among the first or more number of candidate relay terminals, and transmits information about the at least one selected terminal to the terminal. A base station, wherein the first number is determined based on the height of the terminal and the setting information.

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