Method by which device performs communication in wireless communication system, and device therefor

Abstract

A device according to various embodiments can: report measurement information to a first base station; receive an HO command from the first base station; on the basis that the HO command configures, as a target base station, a base station related to NTN, transmit, to the first base station, information about a time gap related to transmission of a RACH preamble; and transmit the RACH preamble to the target base station.

Description

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

[0001] The present invention relates to a method for a terminal to perform handover in a wireless communication system and a device therefor.

[0002] Wireless communication systems are multiple access systems that support communication with multiple users by sharing available system resources (e.g., bandwidth, transmission power, etc.). Examples of multiple access systems include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and multi-carrier frequency division multiple access (MC-FDMA).

[0003] Sidelink (SL) refers to a communication method that establishes a direct link between user equipment (UE), allowing voice or data to be exchanged directly between terminals without going through a base station (BS). SL is being considered as a solution to address the burden on base stations due to rapidly increasing data traffic.

[0004] V2X (vehicle-to-everything) refers to a communication technology that exchanges information with other vehicles, pedestrians, and infrastructure-based objects 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 Uu interface.

[0005] Meanwhile, as more and more communication devices demand greater communication capacity, the need for improved mobile broadband communication compared to existing radio access technology (RAT) is emerging. Accordingly, communication systems that consider services or terminals sensitive to reliability and latency are being discussed. Next-generation wireless access technologies that consider improved mobile broadband communication, massive machine type communication (MTC), and ultra-reliable and low latency communication (URLLC) can be called new radio access technology (RAT) or new radio (NR). NR can also support vehicle-to-everything (V2X) communication.

[0006] Figure 1 is a diagram for comparing and explaining V2X communication based on RAT before NR and V2X communication based on NR.

[0007] 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) were 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.

[0008] For example, a CAM may include basic vehicle information such as dynamic vehicle status information, such as direction and speed, static vehicle data, such as dimensions, external lighting conditions, and route history. For example, a terminal may broadcast a CAM, and the latency of the CAM may be less than 100 ms. For example, in the event of an emergency, such as a vehicle breakdown or accident, a terminal may generate a DENM and transmit it to other terminals. For example, all vehicles within the transmission range of the terminal may receive the CAM and / or DENM. In this case, the DENM may have a higher priority than the CAM.

[0009] Since then, various V2X scenarios have been proposed in NR in relation to V2X communications. For example, various V2X scenarios may include vehicle platooning, advanced driving, extended sensors, and remote driving.

[0010] For example, based on vehicle platooning, vehicles can dynamically form groups and move together. For example, to perform platoon operations based on vehicle platooning, vehicles in the group can receive periodic data from the lead vehicle. For example, vehicles in the group can use this periodic data to narrow or widen the gap between vehicles.

[0011] For example, based on improved driving, vehicles can become 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. Furthermore, for example, each vehicle can share driving intentions with nearby vehicles.

[0012] For example, based on extended sensors, raw data, 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, a vehicle can perceive its environment better than it can perceive using its own sensors.

[0013] For example, based on remote driving, a remote driver or V2X application can operate or control the remote vehicle for people who cannot drive or for remote vehicles located in hazardous environments. For example, in cases where the route is predictable, such as public transportation, cloud computing-based driving can be utilized to operate or control the remote vehicle. Additionally, access to a cloud-based back-end service platform, for example, can be considered for remote driving.

[0014] 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 communication.

[0015] The technical problem to be solved by the present invention is to provide a method for performing communication more accurately and efficiently.

[0016] 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 pertains from the description below.

[0017] A method by a UE (User Equipment) according to one aspect may include: reporting measurement information to a first base station; receiving a HO (Handover) command from the first base station; transmitting information about a time gap related to transmission of a RACH preamble (Random Access Channel preamble) to the first base station based on the HO command setting a base station related to a Non-Terrestrial Network (NTN) as a target base station; and transmitting the RACH preamble to the target base station.

[0018] Alternatively, the UE may be allowed to transmit and receive data with the first base station for a specific time period even after transmission of the RACH preamble.

[0019] Alternatively, the specific time interval may be determined based on an end point of the time gap and a reception prediction point in time at which reception of a random access response (RAR) responding to the RACH preamble is predicted.

[0020] Alternatively, the UE may report information to the first base station about the time at which the connection with the first base station is terminated, and terminate the connection with the first base station after the elapse of the specific time period.

[0021] Alternatively, the time gap may be determined based on the time required to transmit the RACH preamble by frequency switching from a first frequency band for the first base station to a second frequency band for the target base station, and to frequency switch from the second frequency band to the first frequency band.

[0022] Alternatively, information about the time gap may be transmitted to the first base station via a Medium Access Control-Control Element (MAC-CE).

[0023] Alternatively, the information about the time gap may include information about the duration, and the time gap may be a time interval lasting for the duration from the transmission time of the MAC-CE.

[0024] Alternatively, the RACH preamble may be transmitted to the target base station based on the information about the time gap transmitted to the first base station.

[0025] Alternatively, the target base station may be an NTN cell or a TN (Terrestrial Network) cell connected via the NTN cell.

[0026] According to another aspect, at least one non-transitory computer-readable recording medium includes instructions that, when executed by at least one processor, perform operations, which may include reporting measurement information to a first base station; receiving a HO (Handover) command from the first base station; transmitting information about a time gap related to transmission of a RACH preamble (Random Access Channel preamble) to the first base station based on the HO command setting a base station associated with a Non-Terrestrial Network (NTN) as a target base station; and transmitting a RACH preamble to the target base station.

[0027] According to another aspect, a UE (User Equipment) includes an RF (Radio Frequency) transceiver; and a processor connected to the RF transceiver, wherein the processor controls the RF transceiver to report measurement information to a first base station, receives a HO (Handover) command from the first base station, and transmits information about a time gap related to transmission of a RACH preamble (Random Access Channel preamble) to the first base station based on the HO command setting a base station related to a NTN (Non-Terrestrial Network) as a target base station, and transmits a RACH preamble to the target base station.

[0028] According to another aspect, a processing device for controlling a UE (User Equipment) includes at least one processor; and at least one memory connected to the at least one processor and storing instructions that perform operations when executed by the at least one processor, wherein the operations may include reporting measurement information to a first base station; receiving a HO (Handover) command from the first base station; transmitting information about a time gap related to transmission of a RACH preamble (Random Access Channel preamble) to the first base station based on the HO command setting a base station related to a NTN (Non-Terrestrial Network) as a target base station; and transmitting a RACH preamble to the target base station.

[0029] According to another aspect, a method by a first base station may include the steps of: receiving measurement information from a UE (User Equipment); transmitting a HO (Handover) command determined based on the measurement information to the UE; and receiving information on a time gap related to transmission of a RACH preamble (Random Access Channel preamble) from the UE based on the HO command setting a base station related to a NTN (Non-Terrestrial Network) as a target base station.

[0030] According to another aspect, a base station includes an RF (Radio Frequency) transceiver; and a processor connected to the RF transceiver, wherein the processor controls the RF transceiver to receive measurement information from a UE (User Equipment), transmits a HO (Handover) command determined based on the measurement information to the UE, and based on the HO command setting a base station related to a NTN (Non-Terrestrial Network) as a target base station, information on a time gap related to transmission of a RACH preamble (Random Access Channel preamble) can be received from the UE.

[0031] According to one embodiment of the present invention, communication can be performed more accurately and efficiently in a wireless communication system. For example, even when performing HO to a target base station associated with an NTN cell with a long RTT, communication with the source base station can be guaranteed for a certain period of time, thereby maximizing UE service continuity.

[0032] 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.

[0033] The drawings attached to this specification are intended to provide an understanding of the present invention, illustrate various embodiments of the present invention, and together with the description of the specification serve to explain the principles of the present invention.

[0034] Figure 1 is a diagram for comparing and explaining V2X communication based on RAT before NR and V2X communication based on NR.

[0035] Figure 2 shows the structure of the LTE system.

[0036] Figure 3 shows the structure of the NR system.

[0037] Figure 4 shows the structure of a radio frame of NR.

[0038] Figure 5 shows the slot structure of an NR frame.

[0039] FIG. 6 illustrates a communication structure that can be provided in a 6G system according to one embodiment of the present disclosure.

[0040] FIG. 7 illustrates an electromagnetic spectrum according to one embodiment of the present disclosure.

[0041] Figure 8 shows a radio protocol architecture for SL communication.

[0042] Figure 9 shows a terminal performing V2X or SL communication.

[0043] Figure 10 shows resource units for V2X or SL communication.

[0044] FIG. 11 illustrates an example of a BWP according to one embodiment of the present disclosure.

[0045] 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.

[0046] Figure 13 is a diagram for explaining the control plane procedure of L2 U2N relay (UE-to-Network Relay).

[0047] Figures 14 to 18 are drawings for explaining the U2X system.

[0048] Figures 19 to 27 are diagrams illustrating how a UAV performs handover with respect to a satellite gNB.

[0049] FIG. 28 and FIG. 29 are drawings for explaining a method for maintaining service continuity during handover between a TN and an NTN.

[0050] Figure 30 is a diagram for explaining how a UE performs operations related to handover.

[0051] Figure 31 is a diagram for explaining how a first base station performs operations related to handover.

[0052] Figure 32 illustrates a communication system applied to the present invention.

[0053] Figure 33 illustrates a wireless device applicable to the present invention.

[0054] Figure 34 illustrates another example of a wireless device applicable to the present invention. The wireless device may be implemented in various forms depending on the use case / service.

[0055] Figure 35 illustrates a vehicle or autonomous vehicle to which the present invention is applied.

[0056] 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 code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and multi-carrier frequency division multiple access (MC-FDMA).

[0057] Sidelink refers to a communication method that establishes a direct link between user equipment (UE), allowing voice or data to be exchanged directly between terminals without going through a base station (BS). Sidelink is being considered as a solution to address the burden on base stations due to rapidly increasing data traffic.

[0058] V2X (vehicle-to-everything) refers to a communication technology that exchanges information with other vehicles, pedestrians, and infrastructure-based objects 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 Uu interface.

[0059] Meanwhile, as more and more communication devices demand greater communication capacity, the need for improved mobile broadband communication compared to existing radio access technology (RAT) is emerging. Accordingly, communication systems that consider services or terminals sensitive to reliability and latency are being discussed. Next-generation wireless access technologies that consider improved mobile broadband communication, massive MTC, and URLLC (Ultra-Reliable and Low Latency Communication) can be called new radio access technology (RAT) or new radio (NR). NR can also support V2X (vehicle-to-everything) communication.

[0060] The following technologies 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, and 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.

[0061] 5G NR, the successor to LTE-A, is a new clean-slate mobile communications system featuring high performance, low latency, and high availability. 5G NR can utilize all available spectrum resources, from low-frequency bands below 1 GHz, mid-frequency bands between 1 GHz and 10 GHz, and high-frequency (millimeter wave) bands above 24 GHz.

[0062] For clarity, the description will focus on LTE-A or 5G NR, but the technical ideas of the embodiment(s) are not limited thereto.

[0063] Figure 2 illustrates the architecture of an applicable LTE system. This may be referred to as an Evolved-UMTS Terrestrial Radio Access Network (E-UTRAN) or a Long Term Evolution (LTE) / LTE-A system.

[0064] 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 referred to 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 referred to by other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), an access point, etc.

[0065] Base stations (20) can be connected to each other via the X2 interface. The base station (20) is connected to an EPC (Evolved Packet Core, 30) via the S1 interface, more specifically, to an MME (Mobility Management Entity) via the S1-MME, and to an S-GW (Serving Gateway) via the S1-U.

[0066] The EPC (30) consists of an MME, an S-GW, and a P-GW (Packet Data Network-Gateway). The MME holds information about terminal access and capabilities, and this information is primarily used for terminal mobility management. The S-GW is a gateway with the E-UTRAN as its endpoint, and the P-GW is a gateway with the PDN as its endpoint.

[0067] The layers of the radio interface protocol between the terminal and the network can be divided into L1 (Layer 1), L2 (Layer 2), and L3 (Layer 3) 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 Layer 1 provides an information transfer service using a physical channel, and the RRC (Radio Resource Control) layer located in Layer 3 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.

[0068] Figure 3 shows the structure of the NR system.

[0069] 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 eNB are connected to each other via an Xn interface. The gNB and eNB are connected to the 5th generation core network (5G Core Network: 5GC) via the NG interface. More specifically, the gNB is connected to the access and mobility management function (AMF) via the NG-C interface, and the gNB is connected to the user plane function (UPF) via the NG-U interface.

[0070] Figure 4 shows the structure of a radio frame of NR.

[0071] Referring to FIG. 4, radio frames can be used for 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 sub-frames (Subframes, SF). A sub-frame can be divided into one or more slots, and the number of slots within a sub-frame can be determined by the Subcarrier Spacing (SCS). Each slot can include 12 or 14 OFDM (A) symbols depending on the cyclic prefix (CP).

[0072] When normal CP is used, each slot can contain 14 symbols. When extended CP is used, each slot can contain 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).

[0073] Table 1 below shows the number of symbols per slot ((N)) depending on the SCS setting (u) when normal CP is used. slot symb ), number of slots per frame ((N frame,u slot ) and the number of slots per subframe ((N subframe,u slot ) is an example.

[0074] SCS (15*2 u )N slot symb N frame,u slot N subframe,u slot 15KHz (u=0)1410130KHz (u=1)1420260KHz (u=2)14404120KHz (u=3)14808240KHz (u=4)1416016

[0075] 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.

[0076] SCS (15*2 u )N slot symb N frame,u slot N subframe,u slot 60KHz (u=2)12404

[0077] In an NR system, OFDM(A) numerology (e.g., SCS, CP length, etc.) may be set differently between multiple cells that are merged into a single terminal. Accordingly, the (absolute time) interval 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.

[0078] In NR, multiple numerologies, or SCSs, can be supported to support various 5G services. For example, a 15 kHz SCS can support wide areas in traditional cellular bands, while a 30 kHz / 60 kHz SCS can support dense urban areas, lower latency, and wider carrier bandwidth. A 60 kHz or higher SCS can support bandwidths greater than 24.25 GHz to overcome phase noise.

[0079] 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 values ​​of the frequency ranges 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 the "sub 6 GHz range", and FR2 can mean the "above 6 GHz range" and can be called millimeter wave (mmW).

[0080] Frequency Range designationCorresponding frequency rangeSubcarrier Spacing (SCS)FR1450MHz - 6000MHz15, 30, 60kHzFR224250MHz - 52600MHz60, 120, 240kHz

[0081] As described above, the numerical value of the frequency range of the NR system can be changed. For example, FR1 may include a band from 410 MHz to 7125 MHz, as shown in Table 4 below. That is, FR1 may include a frequency band above 6 GHz (or 5850, 5900, 5925 MHz, etc.). For example, the frequency band above 6 GHz (or 5850, 5900, 5925 MHz, etc.) included within FR1 may include an unlicensed band. The unlicensed band may be used for various purposes, such as for vehicular communications (e.g., autonomous driving).

[0082] Frequency Range designationCorresponding frequency rangeSubcarrier Spacing (SCS)FR1410MHz - 7125MHz15, 30, 60kHzFR224250MHz - 52600MHz60, 120, 240kHz

[0083] Figure 5 shows the slot structure of an NR frame.

[0084] Referring to Figure 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. Alternatively, 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.

[0085] A carrier includes multiple subcarriers in the frequency domain. An RB (Resource Block) can be defined as multiple (e.g., 12) consecutive subcarriers in the frequency domain. A BWP (Bandwidth Part) can be defined as multiple consecutive (P)RBs ((Physical) Resource Blocks) in the frequency domain, and can correspond to one numerology (e.g., SCS, CP length, etc.). A carrier can include up to N (e.g., 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 to it.

[0086] 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 refer to a physical layer. Furthermore, for example, the L2 layer may refer to at least one of a MAC layer, an RLC layer, a PDCP layer, and an SDAP layer. Furthermore, for example, the L3 layer may refer to an RRC layer.

[0087] 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.

[0088] New network characteristics in 6G may include:

[0089] - Satellite integrated network

[0090] - Connected Intelligence: Unlike previous generations of wireless communication systems, 6G is revolutionary, upgrading the wireless evolution from "connected objects" to "connected intelligence." AI can be applied at every stage of the communication process (or at every signal processing step, as described below).

[0091] - Seamless integration of wireless information and energy transfer

[0092] - Ubiquitous super 3D connectivity: Access to networks and core network functions of drones and very low Earth orbit satellites will create super 3D connectivity in 6G ubiquitous.

[0093] Some general requirements for the new network characteristics of 6G, such as the above, may be as follows:

[0094] - small cell networks

[0095] - Ultra-dense heterogeneous network

[0096] - High-capacity backhaul

[0097] - Radar technology integrated with mobile technology: High-precision localization (or location-based services) through communications is a key feature of 6G wireless communication systems. Therefore, radar systems will be integrated with 6G networks.

[0098] - Softwarization and virtualization

[0099] Below, the core implementation technologies of the 6G system are described.

[0100] - Artificial Intelligence: Incorporating AI into communications can streamline and improve real-time data transmission. AI can use numerous analytics to determine how complex target tasks should be performed. This means AI can increase efficiency and reduce processing delays. Time-consuming tasks such as handovers, network selection, and resource scheduling can be performed instantly using AI. AI can also play a crucial role in machine-to-machine (M2M), machine-to-human, and human-to-machine communications. Furthermore, AI can facilitate rapid communication in brain-computer interfaces (BCIs). 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.

[0101] - THz communication (terahertz communication): Data rates can be increased by increasing the bandwidth. This can be achieved by using sub-THz communication with wide bandwidths and applying advanced massive MIMO technology. THz waves, also known as sub-millimeter waves, typically refer to the frequency range between 0.1 THz and 10 THz, with corresponding wavelengths ranging from 0.03 mm to 3 mm. The 100 GHz to 300 GHz band (sub-THz band) is considered a key part of the THz spectrum for cellular communications. Adding the sub-THz band to the mmWave band will increase the capacity of 6G cellular communications. Among the defined THz bands, 300 GHz to 3 THz lies in the far infrared (IR) frequency band. While part of the optical band, the 300 GHz to 3 THz band lies at the boundary of the optical band, immediately following the RF band. Therefore, this 300 GHz to 3 THz band exhibits similarities to RF.

[0102] Figure 7 illustrates the electromagnetic spectrum according to one embodiment of the present disclosure. The embodiment of Figure 7 can be combined with various embodiments of the present disclosure. Key characteristics of THz communications include (i) a widely available bandwidth to support very high data rates, and (ii) high path loss at high frequencies (highly directional antennas are essential). The narrow beamwidth generated by the highly directional antenna reduces interference. The small wavelength of THz signals allows for a much larger number of antenna elements to be integrated into devices and base stations operating in this band. This enables the use of advanced adaptive array techniques to overcome range limitations.

[0103] - Large-scale MIMO technology

[0104] - Hologram beamforming (HBF)

[0105] - Optical wireless technology

[0106] - Free-space optical transmission backhaul network (FSO backhaul network)

[0107] - Quantum communication

[0108] - Cell-free communication

[0109] - Integration of wireless information and power transmission

[0110] - Integration of wireless communication and sensing

[0111] - Integrated access and backhaul network

[0112] - Big data analysis

[0113] - Reconfigurable intelligent surface

[0114] - metaverse

[0115] - Blockchain

[0116] Unmanned aerial vehicles (UAVs): UAVs, or drones, will be a key element in 6G wireless communications. In most cases, high-speed data wireless connectivity can be provided using UAV technology. Base stations (BSs) can be installed on UAVs to provide cellular connectivity. UAVs may offer specific capabilities not found in fixed BS infrastructure, such as easy deployment, robust line-of-sight links, and controlled mobility. During emergencies such as natural disasters, deploying terrestrial communications infrastructure is not economically feasible and sometimes cannot provide services in volatile environments. UAVs can easily handle these situations. UAVs will become a new paradigm in wireless communications. This technology facilitates three fundamental requirements for wireless networks: enhanced mobile broadband (eMBB), URLLC, and mMTC. UAVs can also support various 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.

[0117] - Autonomous driving (self-driving): V2X (vehicle to everything), a key element in 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) and vehicle-to-infrastructure (V2I) wireless communication. Fast transmission speeds and low-latency technologies are essential to maximize autonomous driving performance and ensure high safety. Furthermore, in the future, autonomous driving will go beyond simply providing warnings or guidance messages to drivers and may require active intervention in vehicle operation and direct control of 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.

[0118] Figure 8 illustrates a radio protocol architecture for SL communication. Specifically, Figure 8 (a) illustrates the user plane protocol stack of NR, and Figure 8 (b) illustrates the control plane protocol stack of NR.

[0119] Below, the SL synchronization signal (Sidelink Synchronization Signal, SLSS) and synchronization information are described.

[0120] 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 and acquire synchronization using the S-PSS. For example, a terminal may acquire detailed synchronization and detect a synchronization signal ID using the S-PSS and the S-SSS.

[0121] PSBCH (Physical Sidelink Broadcast Channel) may be a (broadcast) channel that transmits basic (system) information that a terminal must know first before transmitting or receiving an SL signal. 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 NR V2X, for evaluating PSBCH performance, the payload size of PSBCH may be 56 bits, including a 24-bit CRC.

[0122] 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 the carrier, and the transmission bandwidth may be within a (pre-)configured SL BWP (Sidelink BWP). For example, the bandwidth of the S-SSB may be 11 RBs (Resource Blocks). 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 the frequency to discover the S-SSB in the carrier.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] Meanwhile, when the SCS is 60 kHz, two types of CP may 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 within 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 within the S-SSB transmitted by the transmitting terminal may be 7 or 6. For example, the PSBCH may be mapped to the first symbol within the S-SSB transmitted by the transmitting terminal. For example, the receiving terminal receiving the S-SSB may perform an Automatic Gain Control (AGC) operation in the first symbol section of the S-SSB.

[0127] Figure 9 shows a terminal performing V2X or SL communication.

[0128] Referring to FIG. 9, the term "terminal" in V2X or SL communication may primarily refer to a user's terminal. However, if a network device such as a base station transmits and receives signals 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).

[0129] For example, terminal 1 can select a resource unit corresponding to a specific resource within a resource pool, which represents a set 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 from terminal 1 within the resource pool.

[0130] 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.

[0131] 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.

[0132] Figure 10 shows resource units for V2X or SL communication.

[0133] Referring to Figure 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. Therefore, a total of NF * NT resource units can be defined within the resource pool. Figure 10 illustrates an example where the resource pool repeats with a cycle of NT subframes.

[0134] As shown in Figure 10, a single resource unit (e.g., Unit #0) may appear periodically and repeatedly. Alternatively, to achieve diversity effects in the time or frequency dimensions, the index of the physical resource unit to which a single logical resource unit is mapped may change in a predetermined pattern over time. In this resource unit structure, a resource pool may refer to a set of resource units that a terminal wishing to transmit an SL signal can use for transmission.

[0135] Resource pools can be subdivided into several categories. For example, based on the content of the SL signal transmitted from each resource pool, resource pools can be categorized as follows:

[0136] (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, in which 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.

[0137] (2) The 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 the SL data channel excluding SA information may be transmitted from the resource pool for the SL data channel. In other words, the REs (Resource Elements) that were 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, the transmitting terminal may transmit the PSSCH by mapping it to consecutive PRBs.

[0138] (3) A discovery channel may be a resource pool for transmitting terminals to transmit information such as their IDs. Through this, transmitting terminals can enable neighboring terminals to discover them.

[0139] Even if the content of the SL signal described above is the same, different resource pools may be used depending on the transmission and reception properties of the SL signal. For example, even if 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 for individual signals to individual transmitting terminals or whether individual transmitting terminals independently select individual signal transmission resources within the resource pool), the signal format (for example, the number of symbols 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.

[0140] 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.

[0141] Referring to Figure 11, a common resource block (CRB) may be a carrier resource block numbered from one end of a carrier band to the other. Furthermore, a PRB may be a numbered resource block within each BWP. Point A may indicate a common reference point for the resource block grid.

[0142] The BWP can be set by Point A, an offset from Point A (NstartBWP), and a bandwidth (NsizeBWP). For example, Point A can be an outer reference point of a PRB of a carrier where subcarrier 0 of all numerologies (e.g., all numerologies supported by the network on that carrier) are aligned. For example, the offset can be the PRB spacing between the lowest subcarrier in a given numerology and Point A. For example, the bandwidth can be the number of PRBs in a given numerology.

[0143] 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.

[0144] PSBCH (Physical Sidelink Broadcast Channel) may be a (broadcast) channel that transmits basic (system) information that a terminal must know first before transmitting or receiving an SL signal. 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).

[0145] 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 the carrier, and the transmission bandwidth may be within a (pre-)configured SL BWP (Sidelink BWP). For example, the bandwidth of the S-SSB may be 11 RBs (Resource Blocks). 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 the frequency to discover the S-SSB in the carrier.

[0146] 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 may be combined with various embodiments of the present disclosure.

[0147] Referring to (a) of FIG. 12, in resource allocation mode 1, the base station may schedule SL resources to be used by the terminal for SL transmission. For example, in step S1200, the base station may transmit information related to SL resources and / or information related to UL resources to the first terminal. For example, the UL resources may include PUCCH resources and / or PUSCH resources. For example, the UL resources may be resources for reporting SL HARQ feedback to the base station.

[0148] For example, a first terminal may receive information related to a dynamic grant (DG) resource and / or information related to a configured grant (CG) resource from a base station. For example, a CG resource may include a CG type 1 resource or a CG type 2 resource. In this specification, a DG resource may be a resource that a base station configures / allocates to the first terminal via downlink control information (DCI). In this specification, a CG resource may be a (periodic) resource that a base station configures / allocates to the first terminal via DCI and / or an RRC message. For example, in the 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 the 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 a DCI related to activation or release of the CG resource to the first terminal.

[0149] 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 SL.

[0150] Referring to (b) of FIG. 12, in resource allocation mode 2, a terminal can determine an SL transmission resource within the SL resources set by the base station / network or within the preset SL resources. For example, the set SL resources or the preset SL resources 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 the resource pool can transmit a PSCCH (e.g., Sidelink Control Information (SCI) or 1st-stage SCI) to a second terminal using the resource. 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.

[0151] Referring to (a) or (b) of FIG. 12, for example, a first terminal may transmit an SCI to a second terminal on a 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, an SCI transmitted on a PSCCH may be referred to as a 1st SCI, a 1st SCI, a 1st-stage SCI, or a 1st-stage SCI format, and an SCI transmitted on a PSSCH may be referred to as a 2nd SCI, a 2nd SCI, a 2nd-stage SCI, or a 2nd-stage SCI format.

[0152] Referring to (a) or (b) of FIG. 12, in step S1530, the first terminal may receive a PSFCH. For example, the first terminal and the second terminal may determine PSFCH resources, and the second terminal may use the PSFCH resources to transmit HARQ feedback to the first terminal.

[0153] Referring to (a) of FIG. 12, in step S1540, the first terminal may transmit SL HARQ feedback to the base station via PUCCH and / or PUSCH.

[0154] Figure 13 is a diagram for explaining the control plane procedure of L2 U2N relay (UE-to-Network Relay).

[0155] The PC5-RRC aspect PC5 unicast link establishment procedure of Rel-16 NR V2X can be reused to establish a secure unicast link for L2 U2N relay (layer 2 UE-to-Network relaying) between the remote UE and the relay UE before the remote UE establishes a Uu RRC connection with the network via the relay UE.

[0156] For both in-coverage and out-of-coverage scenarios, when a remote UE initiates the first RRC message to establish a connection with a gNB, the PC5 L2 configuration for transmissions 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 the L2 U2N relay.

[0157] A given scenario (TS 38.300) describes the control plane procedures of an L2 U2N relay as follows:

[0158] 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.

[0159] At step S1302, the remote UE can transmit the first RRC message (i.e., RRCSetupRequest) to establish a 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 initiated in RRC_CONNECTED, it must perform its own connection establishment upon receiving the message for the default L2 configuration of PC5.

[0160] 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 establishes an RLC channel for relaying SRB1 to the remote UE via PC5. This step prepares the relay channel for SRB1.

[0161] In step S1305, a remote UE SRB1 message (e.g., an RRCSetupComplete message) is transmitted to the gNB via the relay UE using the SRB1 relay channel over PC5. The remote UE is then RRC connected over Uu.

[0162] In steps S1306 and S1307, the remote UE and the gNB establish security according to legacy procedures, and the security message is transmitted through the Relay UE.

[0163] In steps S1308 and S1309, the gNB transmits RRCReconfiguration to the remote UE via the relay UE to set up the relay SRB2 / DRB. The remote UE responds by transmitting RRCReconfigurationComplete to the gNB via the relay UE.

[0164] In step S1310, the gNB establishes 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 establishes an additional RLC channel between the remote UE and the relay UE for traffic relay.

[0165] In the above scenario, in addition to the connection setup procedure, for L2 UE-to-Network relay:

[0166] - RRC reconfiguration and RRC disconnection procedures can reuse legacy RRC procedures with message content / configuration design left in the WI phase.

[0167] - The RRC connection re-establishment and RRC connection resumption procedures can be reused as a baseline by considering the connection establishment procedure of the L2 U2N relay above to handle relay-specific parts along with the message content / structure design. The message content / structure can be defined later.

[0168] Unmanned Aerial Vehicle (UAV)-to-everything (U2X)

[0169] Figures 14 to 18 are drawings for explaining the U2X system.

[0170] The key points of the proposed U2X solution in the given scenario (TR 23.700-58) are as follows:

[0171] - 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.

[0172] - Communication mode: BRID (Broadcasting UAV identification) can use Broadcast communication mode. DAA can use Broadcast communication mode to advertise UAV information. Broadcast via PC5 or unicast via PC5 can be used between two or more UAVs for DAA de-collision. Unicast via Uu via U2X AS may not be supported in the above-mentioned U2X solution. Groupcast mode for NR-based PC5 may not be supported in the above-mentioned 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 requirements.

[0173] - U2X can be supported by a U2X Application Server that interfaces with the operator network via NEF, as in the case of a V2X Application Server.

[0174] Meanwhile, the above given scenario / solution needs to allow for multiple deployment scenarios where a dedicated service set can be defined and the U2X AS and USS providing the UAV are the same or different entities.

[0175] - A U2X policy (U2XP) can be defined to provide configuration parameters to a UE for U2X communication via a PC5 reference point or a Uu reference point. The configuration parameters can be preset in a Mobile Equipment (ME), set in a universal IC card (UICC), pre-set in the ME and set in the UICC, provided / updated by a U2X application server via a policy control function (PCF) and / or a V1 reference point, or provided / updated to the UE by the PCF. Here, the UE needs to consider the U2X policies in the following order of priority: those provided / updated by the PCF, those provided / updated by the U2X application server via the V1 reference point, those configured in the UICC, and those pre-configured in the ME. A de-conflicting policy can be a policy indicating a communication mode for de-conflicting (unicast or broadcast), a communication frequency for de-conflicting, etc.

[0176] - As with V2X, the Tx profile or NR Tx profile can be determined based on the U2XP mapping of the U2X service type.

[0177] - Both UAVs with UICC and UAVs without UICC (i.e. not subscribed to an 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.”

[0178] - U2X communication parameters of the U2X application server or PCF can be transmitted via the UAV-C UE.

[0179] - In addition to the existing parameters for V2X, PC5 RAT-specific radio parameters (e.g., LTE PC5, NR PC5) may be configured, including geographic area, altitude restrictions, and validity timers. Such additional information / parameters may be required to policy-specifically control PC5 usage based on the specific location of the UAV.

[0180] - The definition of DAA / UAV service types may go beyond the scope of the given scenarios described above.

[0181] - For UAVs with UICC to use PC5-based communications for BRID and DAA, successful UUAA authentication / authorization as defined in TS 23.256 and authorization via U2XP are required. 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 following values ​​specifically defined for aviation applications: ITS Application Identifier (ITS-AID), Provider Service Identifier (PSID), or Application Identifier (AID).

[0182] - 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.

[0183] Referring to FIG. 14, a non-roaming 5G system architecture for U2X communication via PC5 can be configured as illustrated in FIG. 14. Here, the non-roaming 5G system architecture for U2X communication via PC5 can be applied with the reference point of TS 23.287, and the following differences may exist.

[0184] - U2X1: As a reference point between the UE and the UAV-C and the U2X application of the U2X application server, this reference point may be outside the scope of the above-mentioned scenario.

[0185] - 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.

[0186] - N1: In addition to the relevant functions defined in TS 23.501 for N1, it can also be used to transfer U2X policies and parameters (including service authorization) from AMF to UE for U2X services, and PC5 functions for U2X capabilities and U2X information of UE to AMF.

[0187] - 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.

[0188] - The above-described solution can support UAV UEs utilizing Uu connections and UAV UEs that do not utilize Uu connections (i.e., UAV UEs that are either Uu capable or Uu non-capable). UAVs that do not utilize Uu capabilities can use U2X for BRID and DAA and can be configured via U2X1 for transmissions outside the scope of 3GPP. On the other hand, UAV UEs that do not utilize Uu capabilities can be part of the 3GPP ecosystem as they use U2X1 for configuration by U2X application servers and implement PC5 connections as specified by 3GPP.

[0189] A roaming 5G system architecture for U2X communication over PC5 can be configured as illustrated in FIGS. 15 and 16. Specifically, FIG. 15 illustrates a roaming 5G system architecture for U2X communication over PC5 in a local breakout scenario, and FIG. 16 illustrates a roaming 5G system architecture for U2X communication over PC5 in a home routing scenario.

[0190] A 5G system architecture between Public Land Mobile Networks (PLMNs) for U2X communication over PC5 reference points could be as follows.

[0191] - For U2X communication between PLMNs via PC5 reference point, PC5 parameters need to be set in a consistent manner between UEs within a specific area.

[0192] - 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. 14.

[0193] AF-based service parameter provisioning for U2X communication can be defined as follows.

[0194] - 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 in FIG. 17. Service parameters may also be pre-configured in the UAV using methods outside the scope of 3GPP (e.g., when not utilizing Uu functionality).

[0195] In a U2X scenario, the following may be considered:

[0196] - 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.

[0197] - 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.

[0198] The procedures and mechanisms of TS 23.287 can be applied to U2X scenarios. Specifically, the procedure for broadcasting via PC5 for DAA collision resolution can be performed as shown in Fig. 18. Meanwhile, the procedure for broadcasting via PC5 for DAA collision resolution can be assumed that the UAV is provisioned with a U2X policy that includes a DAA collision resolution policy (e.g., unicast or broadcast communication for collision resolution, communication frequency).

[0199] Specifically, the procedure for broadcasting through PC5 for DAA collision resolution according to FIG. 18 can be performed as follows.

[0200] 1. UAV1 may receive a broadcast message from UAV2 that may include an application layer DAA payload (e.g., CAA level UAV ID, USS address of UAV2, speed, heading, position, etc.).

[0201] - Note 1: A USS address (Unmanned aerial system Traffic Management (UTM) Service Supplier address) is not required if UAV-to-UAV conflicts are resolved locally, but may be required if USS coordination of the UAVs involved in the conflict is required.

[0202] 2. UAV1 can transmit the DAA payload to the upper layer. The application layer can detect collisions by comparing the broadcast message received from UAV2 with its own trajectory and position. If UAV1's application layer detects a collision, it can initiate collision avoidance / resolution procedures with UAV2.

[0203] 3. Optionally, UAV1 can notify its USS (UTM Service Supplier) about the detected collision, including the ID of peer UAV 2.

[0204] 4. UAV1 can select a communication mode (broadcast or unicast) for DAA deconfliction based on input received from the application layer and DAA policy. If the broadcast deconfliction method is selected, the following messages can be exchanged between UAVs.

[0205] 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 with its CAA level UAV ID, and certain parameters (e.g., de-collision information) (e.g., trajectory correction information to avoid collision). (UAV1 broadcasts a message (eg PC5-S message), eg 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 (eg trajectory correction information to avoid collision))

[0206] 6. UAV2 may broadcast a message (e.g., a PC5-S message) to provide the agreed-upon DAA collision resolution policy, updated trajectory, and other information (e.g., a message collision resolution status response, a collision resolution warning, and the CAA-level UAV ID of the participating UAV from the receiving UAV). Subsequent broadcast messages may be exchanged between UAVs at an agreed-upon message frequency until a traffic collision resolution (e.g., mutual position / trajectory monitoring) is reached.

[0207] The impact on services, entities and interfaces related to the above-described U2X may be as shown in Tables 5 and 6 below.

[0208] 1. UE: In addition to the capabilities defined in TS 23.501, the UE supports the following capabilities:- Reporting U2X capabilities (including DAA capabilities) and PC5 based U2X capabilities to the 5GC via the N1 reference point.- Indicating UE based U2X policy provisioning requests via the UE Policy Container.- Receiving U2X parameters from the 5GC via the N1 reference point.- Executing U2X communication procedures via the PC5 reference point.- Configuring parameters for U2X communication. These parameters can be pre-configured in the UE or provisioned or updated by signaling via the U2X1 reference point of the PCF or the U2X Application Server in the HPLMN, if in coverage. 2. AMF: In addition to the functions defined in TS 23.501, the AMF performs the following functions:- Obtains U2X related subscriber information from the UDM and stores it as part of the UE context data.- Selects a PCF that supports U2X policy / parameter provisioning and reports the PC5 capabilities of U2X to the selected PCF.- Obtains U2X related PC5 QoS information from the PCF and stores it as part of the UE context data.- Provides the communication authorization status of the UE to the NG-RAN for U2X communications over the PC5 reference point.- Provides PC5 QoS parameters related to U2X communications to the NG-RAN. 3. PCF: In addition to the functions defined in TS 23.501, it provisions parameters required for U2X communications to the UE and the AMF, including the functions specified in TS 23.287. 4. UDM: Performs subscriber management functions for U2X communications over the PC5 reference point. 5. U2X Application Server: TS 23.Implements a subset of the V2X AS capabilities defined in TS 23.501:- Includes AF capabilities and can support the following minimum capabilities:- For U2X service parameter provisioning, the U2X AS provides U2X communication parameters via PC5 and Uu reference points to the 5GC and UAV UE (via UAVC if required). 6. UDR: In addition to the capabilities defined in TS 23.501, includes the capability to store U2X service parameters. 7. NRF: In addition to the capabilities defined in TS 23.501, discovers PCFs taking U2X capabilities into account. 8. NEF: Performs U2X service parameter support functions for the U2X AS.

[0209] U2X Subscription dataNR U2X Services AuthorizationIndicates whether the UE is authorized to use the NR sidelink for U2X services as UAV UE, UAV-C UE, or Authority UE.LTE sidelink (ie PC5) communication for U2X services.LTE UE-PC5-AMBRAMBR of UE's LTE sidelink (ie PC5) communication for U2X services.

[0210] Additionally, the most recent discussions regarding the above-described scenarios are as shown in Table 7 below.

[0211] Measurement reporting: Based on LTE principles, similar events H1 (height of aerial UE becomes higher than a threshold) and H2 (height of aerial UE becomes lower than a threshold) are introduced. Further improvements to NR are a subject of future study (FFS). Research is needed on the scaling of RRM parameters (e.g., which parameters, what is the purpose / benefit of scaling, and how it can be achieved). - Research is needed on how to limit excessive measurements and measurement reporting (FFS). - Research is needed on whether user consent is required for position reporting in CONNECTED state (FFS). - Research is needed on vertical movement of UAV UEs and their accompanying mobility (FFS). - Rel-18 NR supports reporting of altitude, position, and velocity of UAV UEs. The required accuracy and reporting mechanism, and whether further improvements are needed, are a subject of future study. - Flight path planning reporting, like LTE, will be introduced, with position lists (3D position information) and timestamps adopted as the basic contents of flight path reporting. In NR, whether timestamps are mandatory or optional is FFS. Further enhancements are also needed FFS. - Similar functionality (numberofTriggeringCells) is introduced as in LTE. In NR, whether numberoftriggerbeams is required is FFS. Research is needed on how to prevent measurement reports from being transmitted primarily when the reporting entity is reportOnLeave (FFS). - A waypoint is a planned position of a UE along a flight path, described via the existing parameter type LocationCoordinates defined in TS 37.355. - The timestamp provides the UTC time corresponding to the expected time of arrival at the waypoint and is used as a baseline. Granularity is FFS. - There are no requirements on the spatial distribution of waypoints.- The UE indicates that flight path information is available via a RRCReconfigurationComplete, RRCReestablishmentComplete, RRCResumeComplete or RRCSetupComplete message. Flight path reporting is based on the UE information request / response procedure. - The UE indicates to the network that a new flight path is available (whether initial or updated), reusing the normal request / response procedure for flight path reporting. - The UAI message can also be used by the UE to indicate that flight path information is available. - The trigger condition for a flight path update is specified by the FFS. The maximum number of waypoints in the flight path plan is left to the FFS. - When an event H1 or H2 is triggered, the content of the measurement report is configurable by the network (i.e. it can contain altitude, position information and / or RSRP / RSRQ measurements of the UAV UE). Whether the altitude of the UAV UE must be reported mandatory and what parameters / IEs are used for altitude reporting are FFS.- In NR Rel-18 UAV, the combined use of altitude dependent conditions and RSRP / RSRQ / SINR based conditions is supported for measurement reporting triggering. A combination of existing events is used. Altitude based parameter scaling is not supported as part of Rel-18 NR.- The Number of triggering cells mechanism is not applicable to inter-RAT scenarios, i.e. event B1 and B2 triggering.- The Number of triggering cells mechanism is not restricted to FR1 only, i.e. the Number of triggering cells mechanism is applicable to both FR1 and FR2 (depending on network configuration).- The UE shall not ignore or bypass the Number of triggering cells mechanism when it is configured.- The NumberOfTriggeringBeams mechanism is not introduced.- No replacement mechanism for the Number of triggering cells mechanism is introduced. - No additional mechanism based on the changed number of cells is introduced. - No prohibit timer mechanism is introduced for interference control purposes (e.g. Number of triggering cells). - ReportOnLeave is not triggered by cells that were not previously included in the measurement report for Number of triggering cells. - Support for altitude dependent multiple configurations for improved measurements and measurement reporting. The UE applies its configuration (config) according to altitude. The proposed solution aims to avoid RAN4 impact. How this is configured (e.g. different MO configurations or different parameters, etc.) is described in the FFS. Specific parameters and details are in the FFS. - Altitude dependent multiple configurations are supported at parameter / field level (i.e. different fields / values ​​within the same MO), where different values ​​(or ranges of values) of a parameter / field are applied according to altitude or altitude range. - For MO configuration parameters, at least the following items can be configured to have altitude dependent multiple configurations / values ​​for specific altitude zones: SSB-ToMeasure. The method is specified in the FFS. For L1 and L3 measurement behavior of the UE, FFS.- For MR configuration parameters, at least the following can be configured to have altitude-dependent multiple configurations / values ​​for specific altitude regions: Event A4 threshold and numberoftriggeringcells. This can be specified using FFS (e.g., through event combinations).- If altitude-dependent multiple configurations are provided, the UE applies new values ​​when moving to a new altitude (or altitude range) (similar to RRC reconfiguration). Codes, field descriptions, etc., as per existing specifications apply.- If an altitude-specific value is not explicitly configured for a particular altitude, whether to continue using the previous value or to consider the parameter as disabled should be reviewed on a case-by-case basis and can be clarified through code, field descriptions, or procedure text, as needed. Details are provided in the FFS.

[0212] Satellite gNB-related UAV handover

[0213] Figures 19 to 27 are diagrams illustrating how a UAV performs handover with respect to a satellite gNB.

[0214] In the following, it is assumed that the UAV UE must always be in a CONNECTED state. It can be connected to the ground-gNB within the ground-gNB coverage, but when it goes out of the ground-gNB coverage (e.g., in a desert, sea, or mountainous area), the UAV can connect to the ground-gNB via a satellite or maintain the connection via the satellite-gNB.

[0215] Here, connecting to a ground-gNB via a satellite may mean that the satellite gNB acts as a relay, enabling an indirect connection between the UAV UE and the ground-gNB. On the other hand, satellite-gNB may mean that a gNB (or a device that functions as a gNB) is installed on the satellite itself, enabling a direct connection with the UAV UE.

[0216] Previously, connectivity via satellite was discussed in 3GPP through the NTN WI (work item). The following triggering conditions were added for cases where a terrestrial UE performs HO from a terrestrial gNB (A) to another terrestrial gNB (B) via a satellite relay.

[0217] - 이벤트 D1: Distance between UE and a reference locationreferenceLocation1becomes larger than configured thresholddistanceThreshFromReference1and distance between UE and a reference locationreferenceLocation2becomes shorter than configured thresholddistanceThreshFromReference2;

[0218] - 이벤트 D2: Distance between UE and a moving reference location based onmovingReferenceLocationand its corresponding satellite ephemeris and epoch time broadcast inSIB19for the serving cell becomes larger than configured thresholddistanceThreshFromReference1and distance between UE and a moving reference location determined based onreferenceLocation2becomes shorter than configured thresholddistanceThreshFromReference2;

[0219] - 조건 이벤트 D1 (CondEvent D1): Distance between UE and a reference locationreferenceLocation1becomes larger than configured thresholddistanceThreshFromReference1and distance between UE and a reference locationreferenceLocation2of conditional reconfiguration candidate becomes shorter than configured thresholddistanceThreshFromReference2;

[0220] - 조건 이벤트 D2 (CondEvent D2): Distance between UE and a moving reference location determined based onmovingReferenceLocationand its corresponding satellite ephemeris and epoch time broadcast inSIB19for the serving cell becomes larger than configured thresholddistanceThreshFromReference1and distance between UE and a moving reference location determined based onreferenceLocation2of conditional reconfiguration candidate becomes shorter than configured thresholddistanceThreshFromReference2;

[0221] The reason why the location-based triggering condition as above was added in NTN is that since the signal received through the satellite is a signal transmitted from a very long distance, it may be difficult for the UE to measure the change in signal strength and trigger the measurement report at an appropriate time.

[0222] For example, referring to FIG. 19, a UE on the ground may go out of coverage without being aware of the difference in signal changes between receiving a signal at the edge of satellite_A and receiving a signal at the center of satellite_B. In this case, the existing HO triggering method cannot maintain service continuity. Considering this problem, when the UE moves away from a predetermined (or set) reference location (A) by a certain distance and / or moves closer to another predetermined (or set) reference location (B) by a certain distance, a measurement event may be triggered, thereby satisfying service continuity. This location-based measurement triggering operation may be applied to the existing basic HO procedure or the conditional HO procedure.

[0223] In this way, when a UE communicates using a satellite, the role of the satellite can be distinguished into Scenario 1 and Scenario 2 below.

[0224] - Scenario 1: The satellite can simply receive messages transmitted by the ground gNB and transparently transmit them to the ground UE (transparency mode). Alternatively, it can receive messages from the ground UE and transparently transmit them to the ground gNB.

[0225] - Scenario 2: A method in which a satellite directly performs the functions of a communication gNB. For example, a communication unit capable of performing the same (or similar) functions as a gNB is attached to the satellite, which receives messages transmitted by a ground-based gNB, interprets them, generates messages, and transmits the generated messages to a ground-based UE (regenerative mode). Alternatively, a method may be used in which a message is received from a ground-based UE, interprets them, generates messages, and transmits the generated messages to a ground-based gNB.

[0226] 1. Scenario 1

[0227] (1) Case 1-1

[0228] Referring to FIG. 20, a ground UE connected to gNB(A) can perform a HO procedure to gNB(B) via a transparency satellite (Case 1-1).

[0229] - 1. When a measurement report is triggered for a UE connected to a ground-gNB(A), the UE can measure the signal strength of the current serving cell and neighboring cells and report the same to the ground-gNB(A). In this case, the measurement report on the signal strength can be transmitted to the source gNB, ground-gNB(A), via a satellite (or satellite relay).

[0230] - 2. Ground-gNB (A) can determine HO and transmit a message requesting HO to the target ground-gNB (B).

[0231] - 3. Ground-gNB (A) can receive permission or HO request ACK for the HO request from the target ground-gNB (B).

[0232] - 4. Ground-gNB (A) can transmit an RRC message (e.g., RRCReconfiguration message) containing an HO related command (HO command) to the UE.

[0233] - 5. At this time, the ground-gNB (A) may transmit an SN (Sequence Number) status Transfer message to the target ground-gNB (B). Here, the SN status Transfer message may be a message for transmitting an uplink PDCP SN receiver status and a downlink PDCP SN transmitter status for a data radio bearer (DRB).

[0234] - 6. When the UE receives the RRCReconfiguration message, it can perform RACH to the target ground-gNB (B) and complete the HO procedure by transmitting an RRCReconfigurationComplete message to the target ground-gNB (B).

[0235] - 7. The UE is connected to the target ground-gNB (B), and 8. The target ground-gNB (B) can send a UE context release message to the source ground-gNB (A).

[0236] (2) Case 1-2

[0237] Referring to FIG. 21, a ground UE connected to gNB(B) via a Transparency satellite can perform a HO procedure to ground-gNB(A) (Case 1-2).

[0238] - 1. When a measurement report is triggered for a UE connected to the ground-gNB(B) via a transparency satellite, the UE can report the measurement value to the ground-gNB(B) via the transparency satellite.

[0239] - 2. (source) Ground-gNB (B) can decide on HO and transmit a request for HO to the target ground-gNB (A).

[0240] - 3. (source) Ground-gNB (B) can receive a response to the HO request from the target ground-gNB (A).

[0241] - 4. (Source) Ground-gNB(B) can send an RRCReconfiguration message to the UE to command HO via transparency satellite.

[0242] - 5. At this time, the ground-gNB (B) can transmit SN status Transfer to the target ground-gNB (A).

[0243] - 6. The UE can complete HO by transmitting an RRCReconfigurationComplete message to the target ground-gNB(A) after performing the RACH procedure to the target ground-gNB(A) based on the RRCReconfiguration message.

[0244] - 7. The UE is connected to the target ground-gNB (A), and 8. The target ground-gNB (A) can send a UE context release message to the source ground-gNB (A).

[0245] When a UE performs HO operation as in Case 1-1 and / or Case 1-2, the process in which the UE performs a measurement report via a transparency satellite and the (Source) ground-gNB transmits an RRCReconfiguration message related to the measurement report to the UE (and / or the UE transmits an RRCReconfigurationComplete message to the target ground-gNB) may take significantly longer than the HO between a general ground-gNB and the UE. In this case, the reported measurement values ​​may be out-of-date values, which may be disadvantageous in selecting an appropriate target-gNB. Therefore, it may be more appropriate to apply a conditional HO (CHO) scheme to operations related to HO from a ground UE connected to gNB (A) to gNB (B) via a transparency satellite. This will be described in detail in Case 1-3 and Case 1-4 below.

[0246] (3) Case 1-3

[0247] Referring to FIG. 22, a ground UE connected to ground-gNB (A) can perform a CHO procedure to ground-gNB (B) via a transparency satellite (Case 1-3).

[0248] - 1. A ground UE connected to a ground-gNB (A) can report a measurement value when a measurement report is triggered. For example, the ground UE can report the measurement value to the ground-gNB (A) via a transparency satellite (or satellite relay).

[0249] - 2. (source) Ground-gNB(A) can determine HO based on the above reported measurement values ​​and transmit a HO request message to candidate target gNB(s).

[0250] - 3. The candidate target gNB(s) that accepted the above HO request can send a response allowing HO to the (source) ground-gNB(A).

[0251] - 4. (source) Ground-gNB(A) can transmit CHO-related configuration to ground UE. For example, ground-gNB(A) can provide CHO-related configuration to ground UE through RRCReconfiguration message.

[0252] - 5. The ground UE can transmit RRCReconfigurationComplete to the ground-gNB (A) when it has received the settings related to CHO.

[0253] - 6. The ground-gNB(A) may provide an Early status transfer message to the candidate target gNB(s). Here, the Early status transfer message may include information about the RLC and PDCP layer states of the ground UE.

[0254] - 7. The ground UE can perform RACH to the target ground-gNB(B) through the transparency satellite and complete HO with the target ground-gNB(B) when the HO condition is satisfied based on the CHO condition according to the above CHO setting.

[0255] - 8. The target ground-gNB (B) can provide a message related to the success of HO with the ground UE to the source ground-gNB (A).

[0256] - 9. The source ground-gNB (A) can provide an SN status transfer message to the target ground-gNB (B).

[0257] - 10. The source ground-gNB (A) can transmit a message related to HO cancellation to the remaining candidate target gNBs except the target ground-gNB (B) among the candidate target gNB (s).

[0258] (4) Case 1-4

[0259] Referring to FIG. 23, a ground UE connected to ground-gNB(B) via a Transparency satellite can perform CHO to ground-gNB(A) (Case 1-4).

[0260] - 1. When a measurement report is triggered, the ground UE performs a measurement report to the (source) ground-gNB (B) via the transparency satellite.

[0261] - 2. (Source) The ground-gNB can determine the CHO and transmit a HO request message to the candidate target ground-gNB(s) selected based on the measurement results.

[0262] - 3. The candidate target ground-gNB(s) can transmit a response to the (source) ground-gNB(B) if the HO is allowed.

[0263] - 4. (source) Ground-gNB(B) can perform CHO-related configuration to the ground UE. For example, (source) Ground-gNB(B) can provide the ground UE with an RRCReconfiguration message including CHO configuration for CHO trigger conditions, etc.

[0264] - 5. The ground UE that received the configuration for CHO can send an RRCReconfigurationComplete message to the (source) ground-gNB (B).

[0265] - 6. Ground-gNB(B) can provide an Early status transfer message to candidate target gNB(s).

[0266] - 7. The ground UE can complete the CHO handover procedure by performing RACH to the target gNB (A) when the set specific HO triggering conditions are satisfied.

[0267] - 8. The target ground-gNB (A) can provide a message related to the success of HO with the ground UE to the source ground-gNB (B).

[0268] - 9. The source ground-gNB (B) can provide an SN status transfer message to the target ground-gNB (A).

[0269] - 10. The source ground-gNB (B) can transmit a message related to HO cancellation to the remaining candidate target gNBs except the target ground-gNB (A) among the candidate target gNB (s).

[0270] The CHO procedure according to Cases 1-3 and / or 1-4 can receive HO-related settings for multiple candidate target ground-gNBs in advance and trigger HO based on measurements taken by the ground UE. This has the advantage over the typical HO procedure in that HO can be determined based on currently measured measurements.

[0271] 2. Scenario 2

[0272] (1) Case 2-1

[0273] Referring to FIG. 24, a ground UE connected to gNB (A) can perform HO to satellite-gNB (B).

[0274] - 1. (source) A ground UE connected to ground-gNB(A) can perform measurement reporting to (source) ground-gNB(A).

[0275] - 2. (source) Ground-gNB (A) can determine HO based on the measurement report value and transmit an HO request message to (target) satellite-gNB (B).

[0276] - 3. The ground-gNB (A) can receive a response message from the satellite-gNB (B) that HO is allowed.

[0277] - 4. Ground-gNB (A) can transmit an RRCReconfiguration message including an HO command to the ground UE.

[0278] - 5. Ground-gNB (A) can transmit an SN status transfer message to satellite-gNB (B).

[0279] - 6. After receiving the RRCReconfiguration message including the HO command, the ground UE can perform HO to the target satellite-gNB (B) and complete the HO procedure by transmitting the RCReconfigurationComplete message to the ground-gNB (A).

[0280] - 7. The UE is connected to the target satellite-gNB (B), and 8. The target satellite-gNB (B) can send a UE context release message to the source ground-gNB (A).

[0281] (1) Case 2-2

[0282] Referring to FIG. 25, a ground UE connected to a satellite-gNB (B) can perform HO to a ground-gNB (A).

[0283] - 1. A ground UE connected to a satellite-gNB(B) can perform a measurement report to the satellite-gNB(B) when a measurement report is triggered.

[0284] - 2. Satellite-gNB (B) can determine HO based on the above measurement report, determine target ground-gNB (A), and transmit an HO request message to target ground-gNB (A).

[0285] - 3. Satellite-gNB (B) can receive a response from Target Ground-gNB (A) that HO is allowed.

[0286] - 4. (source) Satellite-gNB(B) can send an RRCReconfiguration message containing a HO command to the ground UE.

[0287] - 5. (source) Satellite-gNB (B) can transmit an SN status transfer message to Target ground-gNB (A).

[0288] - 6. After receiving the RRCReconfiguration message including the HO command, the ground UE can perform HO to the target ground-gNB (A) and complete the HO procedure by transmitting the RRCReconfigurationComplete message to the satellite-gNB (B).

[0289] - 7. The UE is connected to the target ground-gNB (A), and 8. The target ground-gNB (A) can send a UE context release message to the source satellite-gNB (B).

[0290] In Cases 2-1 and 2-2, as in the HO case of Scenario 1 described above, the time required for transmitting the measured value from the ground UE to the satellite-gNB, for the satellite-gNB to make a HO request to the ground-gNB, and for receiving admission (and / or for transmitting the measured value from the ground UE to the ground-gNB, but for the ground-gNB to request HO to the satellite-gNB, and for receiving admission) may be much longer than in the case of a general HO. In this case, the measured value measured by the ground UE may be an out-of-date value, and determining HO based on this may not be suitable for achieving good performance. Therefore, conditional HO (CHO) may be a more appropriate operation for HO used in satellite communication. This will be described in detail in Cases 2-3 and 2-4 below.

[0291] (3) Case 2-3

[0292] Referring to FIG. 26, a ground UE connected to a ground-gNB (A) can perform a CHO procedure with a satellite-gNB (B).

[0293] - 1. When measurement reporting is triggered, the ground UE can report measurement values ​​to the (source) ground-gNB(A).

[0294] - 2. (source) Ground-gNB(A) can transmit an HO request message to candidate satellite-gNB(s) based on the above measurement report.

[0295] - 3. (source) Ground-gNB(A) can receive admission for HO ( / HO Request ACK) from candidate satellite-gNB(s).

[0296] - 4. The (source) ground-gNB (A) receiving this can transmit an RRCReconfiguration message to the ground UE for CHO-related settings for multiple candidate satellite-gNB (s).

[0297] - 5. The ground UE may send RRCReconfigurationComplete to the (source) ground-gNB(A) when it has received the settings related to CHO.

[0298] - 6. The ground-gNB(A) may provide an Early status transfer message to the candidate target satellite-gNB(s). Here, the Early status transfer message may include information about the RLC and PDCP layer states of the ground UE.

[0299] - 7. The UE can perform HO by selecting one target satellite-gNB among candidate target satellite-gNB(s) and performing RACH procedure when conditional HO (CHO) is triggered based on the set value.

[0300] - 8. The target satellite-gNB (B) can provide a message related to the success of HO with the ground UE to the ground-gNB (A).

[0301] - 9. Ground-gNB (A) can provide an SN status transfer message to the target satellite-gNB (B).

[0302] - 10. Ground-gNB(A) can transmit a message related to HO cancellation to the remaining candidate target satellite-gNB(s) except for target satellite-gNB(B).

[0303] (4) Case 2-4

[0304] Referring to FIG. 27, a ground UE connected to a satellite-gNB (B) can perform a CHO procedure with a ground-gNB (A).

[0305] - 1. When a measurement report is triggered, the ground UE performs a measurement report to the satellite-gNB(B).

[0306] - 2. Satellite-gNB(B) can determine CHO and transmit HO request message to candidate target ground-gNB(s) selected based on measurement results.

[0307] - 3. If the candidate target ground-gNB(s) allows HO, it can transmit a response to it to the satellite-gNB(B).

[0308] - 4. Satellite-gNB(B) can perform CHO-related configuration to ground UE. For example, satellite-gNB(B) can provide RRCReconfiguration message including CHO configuration for CHO trigger conditions, etc. to ground UE.

[0309] - 5. The ground UE that has received the configuration for CHO can send an RRCReconfigurationComplete message to the satellite-gNB(B).

[0310] - 6. Satellite-gNB(B) can provide an Early status transfer message to candidate target ground-gNB(s).

[0311] - 7. When a ground UE satisfies a specific HO triggering condition that has been set, the ground UE performs a RACH procedure to a target ground-gNB(A) selected from among candidate target ground-gNB(s), and completes a CHO procedure with the target ground-gNB(A) through the RACH procedure.

[0312] - 8. The target ground-gNB (A) can provide a message related to the success of HO with the ground UE to the satellite-gNB (B).

[0313] - 9. Satellite-gNB (B) can provide an SN status transfer message to the target ground-gNB (A).

[0314] - 10. Satellite-gNB(B) can transmit a message related to HO cancellation to the remaining candidate target ground-gNB(s) except for target ground-gNB(A).

[0315] Below, we propose a method to minimize service interruption during long demonstration times due to the above-described TN-NTN handover.

[0316] Method for maintaining service continuity during handover between TN and NTN

[0317] FIG. 28 and FIG. 29 are drawings for explaining a method for maintaining service continuity during handover between a TN and an NTN.

[0318] The proposed method can be applied in general handover operations as follows.

[0319] In the above-described scenario 1, 1-1 (or 2-1 in the case of scenario 2) represents a case where a handover is performed from a TN (or terrestrial gNB) to an NTN (or NTN gNB). In a typical handover operation, when the UE receives an RRC message (e.g., an RRCReconfiguration message) containing a HO command from a serving gNB (e.g., a source terrestrial-gNB (A)), no further communication (e.g., transmission and reception of data) may be performed with the source gNB (A). Meanwhile, performing a handover to the NTN may include performing a handover to an NTN cell that can be directly connected as described above, and performing a handover to a terrestrial base station / terrestrial cell connected via the NTN (e.g., via a satellite relay). In the following, for convenience of explanation, the description assumes that a handover is performed to a ground base station connected via NTN or satellite relay, but the following description can also be applied to a case where the handover is directly connected to an NTN cell.

[0320] Specifically, referring to FIG. 28, a UE may perform direct communication with a source ground-gNB, but may perform a HO procedure for a target (ground)-gNB connected via a satellite relay UE through a HO decision. At this time, the UE may perform the RACH procedure with the target gNB (e.g., the ground target gNB) based on the relay of the satellite relay, such as steps 6.1, 6.2, and 6.3, as a RACH procedure for handover. This may be a contention-free RACH procedure. Specifically, the preamble given in Step 6.1 may be transmitted to the target gNB (B) via the satellite relay. In Step 6.2, the target-gNB (B) receiving the preamble may transmit an RAR message / RAR to the UE via the satellite relay to allocate a TA value and resources for PUCCH transmission. In Step 6.3, the UE can transmit an RRC message (e.g., an RRCReconfigurationComplete message) to the target gNB(B) via the satellite relay, indicating the completion of the handover. Meanwhile, Steps 6.1, 6.2, and 6.3 described above may take longer than transmission via the existing TN. For example, the higher the satellite relay is, the longer the propagation delay may be. Furthermore, during the RACH procedure described above, the UE may not be able to transmit or receive any data / messages other than those for the RACH procedure, which may cause service continuity issues. Typically, a round trip to LEO via a satellite relay can take 50 ms, and a round trip to MEO via a satellite relay can take 250 to 300 ms. The time it takes for the UE to perform a (contention-free) RACH to the target terrestrial gNB(B) via the satellite relay may cause service continuity issues due to the additional round trip time.

[0321] Meanwhile, the proposed method below proposes a method to resolve the above-described problem by assuming that the time taken for a round trip of a handover-related message via a satellite relay may be much longer than the time taken for a UE to tune from a TN frequency band to an NTN frequency band (or vice versa).

[0322] The proposed method aims to minimize the loss of service continuity of the UE by providing a time gap for RACH operation when handing over from a TN to an NTN. Here, the handover from a TN to an NTN includes both a handover from a terrestrial gNB to an NTN gNB (e.g., Scenario 1) and a handover from a terrestrial gNB to another terrestrial gNB connected via an NTN (Scenario 2), and it is obvious that the proposed method can be applied to both of these cases.

[0323] Referring to FIG. 29, a time gap for RACH operation can be set when performing a handover from a TN to an NTN of a UE. Meanwhile, a dotted line in FIG. 29 indicates data transmission / reception between the UE and the source gNB. Specifically, in Step 4 of FIG. 29 (a step of receiving a message (e.g., an RRCReconfiguration message) for a handover command), unlike the conventional method, the UE can continue to perform data transmission / reception with the source gNB (A) even after receiving the handover command. Meanwhile, the source gNB (A) can separately indicate in the message (e.g., the RRCReconfiguration message) for a handover command whether to perform a handover using the conventional method (e.g., terminating communication with the source gNB upon receipt of the message) or using the proposed method (e.g., maintaining communication with the source gNB for a certain period of time after receipt of the message). For example, if the distance between the satellite relay and the UE / height of the satellite relay is absolutely less than a certain threshold, or if the distance between the satellite relay and the UE / height of the satellite relay does not differ by more than a certain threshold compared to the distance between the UE and the TN, the source gNB may transmit an RRCReconfiguration message including instruction information to handover using the existing method. This is because the proposed method is a method to resolve the problem that occurs due to the large distance between the satellite relay and the UE.

[0324] Meanwhile, the frequency bands used for TN and NTN are different. Therefore, a frequency tuning time may be required for the UE to transmit / receive data through NTN after transmitting / receiving data through TN. In order to transmit an RA / PRACH preamble, the UE may transmit gap information about the RACH gap or RACH time gap to the source gNB using MAC CE, etc. prior to transmitting the RA / PRACH preamble (step 6.1'). The value of the RACH gap or RACH time gap may be set based on the sum of the time it is expected to take for the UE to tune from the TN frequency band to the NTN frequency band, the time it is expected to take for the UE to tune from the NTN frequency band to the TN frequency band, and the time it takes to transmit the preamble for RA to the target gNB (Ground-gNB(B)). Based on the above gap information, the source gNB may assume / determine that transmission / reception of data / messages with the UE is impossible or temporarily suspended during the RACH gap. Here, the transmission time of the MAC CE used to report the gap information may be determined to be the start time of the RACH GAP, and thus the gap information included in the MAC CE may only include information about the length of the time interval during which the RACH GAP is maintained.

[0325] When the MAC CE for reporting gap information for the above-described RACH gap is transmitted to the source gNB, the UE can tune to the frequency band used for the NTN and transmit a preamble (e.g., a RACH preamble) for the RA operation in step 6.1 to the target gNB. Thereafter, the UE can tune back to the TN frequency band and perform data transmission / reception with the source gNB. For example, the RACH gap of the gap information is set to a time corresponding to the total time required for the UE to transmit the MAC CE, then tune to the frequency band of the NTN, transmit a PRACH / RA preamble, and then tune back to the frequency band of the TN. Therefore, when the above-described operations are completed, the time of the RACH gap reported to the source gNB will have elapsed, and thus the UE can resume communication with the source gNB.

[0326] Meanwhile, the time (or waiting time) taken from when the UE transmits the PRACH / RA preamble until it receives the RAR / RAR message from the target gNB may be predicted based on the location / height information of the satellite relay. For example, a method for predicting the waiting time may be formulated based on the height of the satellite relay, and the waiting time may be predicted between the UE and the source gNB using the same formula. In this case, even if the UE does not separately report to the source gNB, the UE and / or the source gNB can effectively predict a time period during which data transmission and reception between them is valid based on the predicted waiting time (and / or the gap information). However, if it is difficult or impossible to predict the waiting time, the UE needs to report to the source gNB the time when the connection with the source gNB is completely terminated through step 6.1' (Report RACH GAP MAC CE) or a separate step not shown in FIG. 29.

[0327] Next, at the time when the RAR is expected to be transmitted, the UE can tune to the NTN frequency band to receive the RAR / RAR message from the target gNB (step 6.2). Next, the UE can transmit a message indicating the completion of the handover (e.g., an RRCReconfigurationComplete message) in the NTN frequency band (step 6.3) and transmit / receive data with the target gNB.

[0328] The source gNB may transmit additional SN status information to the target gNB when it determines that the handover for the UE is complete (step 5-2). The point in time at which the source gNB determines that the handover for the UE is complete may be either a point explicitly indicated by the UE, such as through a MAC CE, or an implicit point in time calculated based on the round trip time calculated using the RACH GAP reported by the UE and the satellite relay height.

[0329] The proposed scheme can be applied not only to cases where the signal quality with respect to the current serving cell is poor, as in a typical handover, but also to cases where the handover occurs due to the UE's preference for a specific cell (e.g., preferring an NTN cell over a TN cell to reduce frequent handovers) even though the signal strength / quality with respect to the current serving cell is not poor. In this case, the UE can report its preferred network (e.g., TN or NTN) in the measurement reporting, or can report its preferred network (e.g., TN or NTN) in advance as assistance information. In this case, the condition for triggering the measurement reporting can include a case where the UE's preferred network (e.g., NTN or TN) is monitored. Alternatively, the proposed scheme can be applied to cases where the source gNB commands a handover to the NTN even though the signal strength with respect to the current serving TN is good due to the UE's moving direction / speed, etc.

[0330] Alternatively, the proposed scheme can also be used to reduce power consumption. For example, during a handover, the UE may be powered off during the RACH GAP, and the proposed scheme can be applied to save power consumption. In this case, the UE may not need to report gap information about the RACH gap to the source gNB. Furthermore, the proposed scheme can be similarly applied to NTN-NTN handovers as well as TN-NTN handovers, when the distance difference between the source NTN and the target NTN is large.

[0331] In this way, the proposed method can guarantee service continuity to the maximum extent possible when a UE connected to a TN cell performs a handover to an NTN cell.

[0332] Figure 30 is a diagram for explaining how a UE performs operations related to handover.

[0333] Referring to FIG. 30, a UE may transmit measurement information to a first base station (S301). Here, the first base station may be a serving base station / serving cell (or source base station) connected to the UE. The UE may trigger reporting / transmission of the measurement information based on the signal strength with the first base station and / or the signal strength of a neighboring base station / neighboring cell. Alternatively, as described above, the UE may trigger reporting of the measurement information when its preferred base station is detected / detected. For example, the measurement information / measurement report may be triggered in relation to a handover when the signal strength with the first base station is below / below a certain threshold or when the preferred base station is detected / detected. Alternatively, the measurement information may include signal strength with the first base station, signal strength for at least one neighboring cell, and neighboring cell list information. Alternatively, the measurement information may further include information on a preferred base station / cell (e.g., a base station / cell associated with an NTN) as described above.

[0334] Next, the UE can receive a HO (Handover) command from the first base station (S303). For example, the first base station can determine whether to perform HO for the UE based on the measurement information, and if HO is determined, transmit a HO request message to a target cell / target base station selected based on the measurement information, and if an HO approval message is received from the target cell / target base station, transmit the HO command to the target cell / target base station to the UE. For example, the UE can receive the HO command via an RRCReconfiguration message.

[0335] Next, if the HO command sets a base station related to the NTN as a target base station, the UE can transmit information about a time gap (e.g., RA gap, RACH gap) related to transmission of a RACH preamble (Random Access Channel preamble) to the target base station to the first base station (S305). The base station related to the NTN may be a base station / cell connected via the NTN as described above (e.g., scenario 1) or an NTN cell. For example, the UE can transmit information about the time gap to the first base station if an HO command is received that sets a NTN cell or a terrestrial base station / cell connected via the NTN (or satellite relay) as a target base station / cell.

[0336] The information about the time gap may be information about the RACH gap described with reference to FIG. 29, and may be a time interval / time gap required for the UE to transmit a RACH preamble to the target base station and then resume communication with the first base station, which is the source base station. For example, the UE may determine the time gap based on a first frequency switching time required for RF tuning / frequency switching from the frequency band of the first base station to the frequency band for the target base station, a time required for transmitting the RACH preamble in the frequency band for the switched target base station, and a second frequency switching time required for switching from the frequency band for the target base station to the frequency band of the first base station after transmitting the RACH preamble. For example, the UE may determine the time gap as a sum or a value greater than the sum of the first switching time, the time required for transmitting the RACH preamble, and the second frequency switching time. Information about the above time gap can be transmitted to the first base station via MAC-CE (Medium Access Control-Control Element).

[0337] The information about the time gap may be information about the start time and the end time of the time gap, or information about a specific duration. In the latter case, the start point of the time gap may be the time at which the information about the time gap is transmitted, or may be determined based on the time at which the information about the time gap is transmitted. For example, the start point of the time gap may be the time at which the MAC-CE is transmitted. In this case, the time gap may be a time gap section that lasts for the duration from the time at which the MAC-CE is transmitted.

[0338] Next, the UE may transmit the RACH preamble to the target base station (S307). For example, if the target base station is associated with an NTN, the UE may first transmit information about the time gap to the first base station and then transmit the RACH preamble to the target base station.

[0339] Meanwhile, as described above, the UE may be allowed to transmit and receive data with the first base station for a specific time period even after transmitting the RACH preamble. For example, if the target base station is a cell / base station not related to NTN, the UE may terminate data transmission and reception with the first base station before transmitting the RACH preamble (e.g., terminate after receiving an RRCReconfiguration message or an RRCReconfiguration message including the HO command). Conversely, if the target base station is a cell / base station related to NTN, the UE may perform data transmission and reception with the first base station for a specific time period even after transmitting the RACH preamble. This is because, if the target base station is related to NTN, a significantly long RTT may be required to perform the RACH procedure, which may not guarantee service continuity of the UE. Therefore, the proposed invention allows data transmission and reception with the first base station for a certain period of time even during the RACH procedure to ensure service continuity of the UE even when the RACH procedure with the target base station related to the NTN is performed.

[0340] The specific time interval may be determined based on the end time of the time gap and the predicted reception time (or waiting time) at which the reception of a random access response (RAR) responding to the RACH preamble is predicted. For example, the UE may determine the predicted reception time from the end time of the time gap as the specific time interval. Alternatively, the UE may consider the time required to switch from the frequency band of the first base station to the frequency band of the target base station and determine the end time of the specific time interval (hereinafter, the end time) prior to the predicted reception time by the switching time. In this case, data transmission and reception between the UE and the first base station may be temporarily suspended during the time interval corresponding to the time gap and then resumed when the specific time interval begins. When the specific time interval ends, the connection between the UE and the first base station may be completely terminated. Alternatively, the UE may provide the first base station with information on the end time of the specific time interval so that the base station can recognize the time when communication continues and / or when communication ends.

[0341] Figure 31 is a diagram for explaining how a first base station performs operations related to handover.

[0342] Referring to FIG. 31, the first base station may receive measurement information from the UE (S311). The measurement information may include signal strength with the first base station, signal strength for at least one neighboring cell, and neighboring cell list information. Alternatively, the measurement information may further include information about a preferred base station / cell (e.g., a base station / cell associated with an NTN), as described above.

[0343] Next, the first base station can transmit a HO (Handover) command determined based on the measurement information to the UE (S313). For example, the first base station can determine whether to perform HO for the UE based on the measurement information, and if HO is determined, transmit a HO request message to a target cell / target base station selected based on the measurement information, and when an HO approval message is received from the target cell / target base station, transmit the HO command to the target cell / target base station to the UE. Here, the target cell / target base station can be a base station / cell connected via NTN as described above, or the NTN cell.

[0344] Next, when the HO command sets a base station related to NTN as a target base station, the first base station can receive information about a time gap related to transmission of a RACH preamble to the target base station from the UE (S315). The base station related to NTN may be a base station / cell connected via NTN as described above (e.g., scenario 1) or an NTN cell. For example, when the first base station transmits an HO command to the UE that sets an NTN cell or a terrestrial base station / cell connected via NTN (or satellite relay) as a target base station / cell, the first base station can receive information about the time gap from the UE. The information about the time gap can be transmitted to the first base station via a MAC-CE (Medium Access Control-Control Element). The information about the time gap may be information about a start time point and an end time point of the time gap, or information about a specific duration. In the latter case, the starting point of the time gap may be the time at which the information of the time gap is transmitted, or may be determined based on the time at which the information of the time gap is transmitted. For example, the starting point of the time gap may be the time at which the MAC-CE is transmitted. In this case, the time gap may be a time interval that lasts for the duration from the time at which the MAC-CE is transmitted.

[0345] Meanwhile, as described above, even if the first base station transmits the HO command to the UE, data transmission and reception from the UE can be maintained. For example, if the target base station is a cell / base station not related to NTN, the first base station can terminate data transmission and reception with the UE from the time point at which the RRCReconfiguration message or the RRCReconfiguration message including the HO command is transmitted to the UE. In contrast, if the target base station is a cell / base station related to NTN, even if the first base station transmits the HO command to the UE, data transmission and reception from the UE can be maintained during the specific time interval described above. Here, the specific time interval can be determined based on the end time point of the time gap and the reception prediction time point at which the UE is expected to receive a random access response (RAR) in response to the RACH preamble. As described above, the first base station can receive information about the end point of the specific time interval from the UE, determine the specific time interval as the time interval between the end point of the time gap and the end point of the provided specific time interval, and perform data transmission and reception with the UE.

[0346] In this way, the proposed invention can maximize service continuity for the UE by ensuring communication with the source base station for a certain period of time even when performing HO to a target base station associated with an NTN cell with a long RTT. Furthermore, the proposed invention can prevent the source base station from transmitting data during the RACH operation period of the UE, where data transmission and reception are impossible, by providing the source base station with time gap information related to the transmission operation of the RACH preamble with the target base station for HO in advance.

[0347] Examples of communication systems to which the invention applies

[0348] 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 / connection (e.g., 5G) between devices.

[0349] Hereinafter, more specific examples will be provided with reference to the drawings. In the drawings / descriptions below, the same drawing reference numerals may represent identical or corresponding hardware blocks, software blocks, or functional blocks, unless otherwise described.

[0350] Figure 32 illustrates a communication system applied to the present invention.

[0351] Referring to FIG. 32, a communication system (1) applied to the present invention includes a wireless device, a base station, and a network. Here, the wireless device refers to 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 Things) 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 an Unmanned Aerial Vehicle (UAV) (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. Mobile devices can include smartphone, smart pad, wearable device (e.g., smart watch, smart glass), computer (e.g., laptop, etc.), 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.

[0352] 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). In addition, IoT devices (e.g., sensors) can communicate directly with other IoT devices (e.g., sensors) or other wireless devices (100a to 100f).

[0353] Wireless communication / connection (150a, 150b, 150c) can be established between wireless devices (100a~100f) / base stations (200), and base stations (200) / base stations (200). Here, 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 wireless communication / connection (150a, 150b, 150c), wireless devices and base stations / wireless devices, and base stations and base stations can transmit / receive wireless signals to each other. For example, 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.

[0354] Examples of wireless devices to which the present invention is applied

[0355] Figure 33 illustrates a wireless device applicable to the present invention.

[0356] Referring to FIG. 33, the first wireless device (100) and the second wireless device (200) can transmit and receive wireless signals via 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. 32.

[0357] A first wireless device (100) includes one or more processors (102) and one or more memories (104), and may further include one or more transceivers (106) and / or one or more antennas (108). The processor (102) controls the memories (104) and / or the transceivers (106), and may be configured to implement the descriptions, functions, procedures, proposals, 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). In addition, 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 code including commands for performing the descriptions, functions, procedures, proposals, methods, and / or operation 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.

[0358] Specifically, a first wireless device or UE (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. 19 to 31. The operations may include reporting measurement information to a first base station; receiving a HO (Handover) command from the first base station; transmitting information about a time gap related to transmission of a RACH preamble (Random Access Channel preamble) to the first base station based on the HO command setting a base station associated with a Non-Terrestrial Network (NTN) as a target base station; and transmitting a RACH preamble to the target base station.

[0359] Alternatively, a processing device may be configured, including a processor (102) and a memory (104) for controlling a first base station. In this case, the processing device may include at least one processor; and at least one memory connected to the at least one processor and storing instructions that perform operations when executed by the at least one processor. The operations may include reporting measurement information to the first base station; receiving a HO (Handover) command from the first base station; transmitting information about a time gap associated with transmission of a RACH preamble (Random Access Channel preamble) to the first base station based on the HO command setting a base station associated with a Non-Terrestrial Network (NTN) as a target base station; and transmitting a RACH preamble to the target base station. Alternatively, at least one non-transitory computer-readable medium storing programs / instructions for performing the above-described operations may be configured.

[0360] The second wireless device (200) includes one or more processors (202), one or more memories (204), and may further include one or more transceivers (206) and / or one or more antennas (208). The processor (202) controls the memories (204) and / or the transceivers (206), and may be configured to implement the descriptions, functions, procedures, proposals, 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). Furthermore, 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 code including commands for performing the descriptions, functions, procedures, proposals, methods, and / or operation 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.

[0361] Specifically, the second wireless device or base station (200) may include a processor (202) and a memory (204) connected 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. 19 to 31. The operations may include receiving measurement information from a UE (User Equipment), transmitting a HO (Handover) command determined based on the measurement information to the UE, and receiving information about a time gap related to transmission of a RACH preamble (Random Access Channel preamble) from the UE based on the HO command setting a base station associated with a NTN (Non-Terrestrial Network) as a target base station.

[0362] Hereinafter, the 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 operation 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 operation 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, proposals and / or methods 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, proposals, methods and / or operational flowcharts disclosed herein.

[0363] One or more processors (102, 202) may be referred to as a controller, a microcontroller, a microprocessor, or a microcomputer. 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 one or more processors (102, 202). The descriptions, functions, procedures, proposals, 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 operation flowcharts disclosed in this document may be implemented using firmware or software configured to perform one or more processors (102, 202) or stored in one or more memories (104, 204) and executed by one or more processors (102, 202). The descriptions, functions, procedures, suggestions, methods and / or operation flowcharts disclosed in this document may be implemented using firmware or software in the form of codes, instructions and / or sets of instructions.

[0364] 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 configured as 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.

[0365] One or more transceivers (106, 206) can transmit user data, control information, wireless signals / channels, etc., as mentioned 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 mentioned in the descriptions, functions, procedures, proposals, methods and / or flowcharts of this document, from one or more other devices. For example, one or more transceivers (106, 206) can be connected 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, or the like, as referred to 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) can 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 user data, control information, wireless signals / channels, etc. processed by one or more processors (102, 202) from baseband signals to RF band signals. For this purpose, one or more transceivers (106, 206) may include an (analog) oscillator and / or filter.

[0366] Examples of wireless devices to which the present invention is applied

[0367] Figure 34 illustrates another example of a wireless device applicable to the present invention. The wireless device may be implemented in various forms depending on the use case / service (see Figure 32).

[0368] Referring to FIG. 34, the wireless device (100, 200) corresponds to the wireless device (100, 200) of FIG. 33 and may be composed of various elements, components, 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 additional elements (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. 34. For example, the transceiver(s) (114) may include one or more transceivers (106, 206) and / or one or more antennas (108, 208) of FIG. 33. The control unit (120) is electrically connected to the communication unit (110), the memory unit (130), and the additional elements (140) and controls the overall operation of the wireless device. For example, the control unit (120) may control the electrical / mechanical operation of the wireless device based on the program / code / command / 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 store information received from an external device (e.g., another communication device) via a wireless / wired interface in the memory unit (130).

[0369] 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. 32, 100a), a vehicle (Fig. 32, 100b-1, 100b-2), an XR device (Fig. 32, 100c), a portable device (Fig. 32, 100d), a home appliance (Fig. 32, 100e), an IoT device (Fig. 32, 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. 32, 400), a base station (Fig. 32, 200), a network node, etc. Wireless devices may be mobile or stationary depending on the use / service.

[0370] In FIG. 34, 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 a 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 graphics 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.

[0371] Examples of vehicles or autonomous vehicles to which the present invention is applied

[0372] Figure 35 illustrates a vehicle or autonomous vehicle applicable to the present invention. The vehicle or autonomous vehicle may be implemented as a mobile robot, car, train, manned / unmanned aerial vehicle (AV), ship, etc.

[0373] Referring to FIG. 35, 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. 34, respectively.

[0374] 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.), and servers. 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, an illuminance 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.

[0375] 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 driving plan based on the acquired data. The control unit (120) can control the drive 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, during autonomous driving, the sensor unit (140c) can acquire vehicle status and surrounding environment information. The autonomous driving unit (140d) can update the autonomous driving route and driving plan based on newly acquired data / information. The communication unit (110) can transmit information regarding the vehicle location, autonomous driving route, driving plan, etc. to the external server. External servers can predict traffic information data in advance using AI technology or other technologies based on information collected from vehicles or autonomous vehicles, and provide the predicted traffic information data to the vehicles or autonomous vehicles.

[0376] Here, the wireless communication technology implemented in the wireless device (XXX, YYY) of the present specification may include not only LTE, NR, and 6G, but also 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, 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, 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.

[0377] 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 without being combined with other components or features. Furthermore, 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 self-evident that claims that do not have an explicit citation relationship in the patent claims may be combined to form an embodiment or may be incorporated as a new claim through a post-application amendment.

[0378] In this document, embodiments of the present invention have been described primarily focusing on the signal transmission and reception relationship between a terminal and a base station. This transmission and reception relationship is equally / similarly extended to signal transmission and reception between a terminal and a relay or a base station and a relay. Certain operations 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 multiple 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 by terms such as fixed station, Node B, eNode B (eNB), and access point. In addition, the terminal may be replaced by terms such as UE (User Equipment), MS (Mobile Station), MSS (Mobile Subscriber Station).

[0379] Embodiments of the present invention may be implemented by various means, for example, hardware, firmware, software, or a combination thereof. In the case of hardware implementation, an embodiment of the present invention may be implemented by one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, etc.

[0380] When implemented via firmware or software, an embodiment of the present invention may be implemented in the form of modules, procedures, functions, etc. that perform the functions or operations described above. The software code may be stored in a memory unit and executed by a processor. The memory unit may be located within or outside the processor and may exchange data with the processor via various known means.

[0381] 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 invention. Therefore, the above detailed description should not be construed as limiting in any respect, but rather as illustrative. The scope of the present invention should be determined by a reasonable interpretation of the appended claims, and all modifications within the scope of equivalents of the present invention are intended to be included within the scope of the present invention.

[0382] The embodiments of the present invention as described above can be applied to various mobile communication systems.

Claims

In a method using UE (User Equipment), A step of reporting measurement information to the first base station; A step of receiving a HO (Handover) command from the first base station; A step of transmitting information about a time gap related to transmission of a RACH preamble (Random Access Channel preamble) to the first base station based on the above HO command setting a base station related to a Non-Terrestrial Network (NTN) as a target base station; and A method comprising the step of transmitting the RACH preamble to the target base station. In the first paragraph, A method in which the UE is allowed to transmit and receive data with the first base station for a specific time period even after transmission of the RACH preamble. In the second paragraph, A method wherein the specific time interval is determined based on an end point of the time gap and a reception prediction point in time at which reception of a random access response (RAR) responding to the RACH preamble is predicted. In the second paragraph, A method in which the UE reports information about the time at which the connection with the first base station is terminated to the first base station, and terminates the connection with the first base station after the elapse of the specific time period. In the first paragraph, A method wherein the time gap is determined based on the time required to transmit the RACH preamble by frequency switching from a first frequency band for the first base station to a second frequency band for the target base station and to frequency switch from the second frequency band to the first frequency band. In the first paragraph, A method in which information about the above time gap is transmitted to the first base station via MAC-CE (Medium Access Control-Control Element). In paragraph 6, Information about the above time gap includes information about the duration, The method wherein the above time gap is a time interval lasting for the duration from the transmission time of the MAC-CE. In the first paragraph, A method wherein the RACH preamble is transmitted to the target base station based on information about the time gap transmitted to the first base station. In the first paragraph, A method wherein the target base station is an NTN cell or a TN (Terrestrial Network) cell connected through the NTN cell. In at least one non-transitory computer-readable recording medium, Contains instructions that perform operations when executed by at least one processor, The above actions are, Report measurement information to the first base station; Receive a HO (Handover) command from the first base station; Based on the above HO command setting a base station related to a Non-Terrestrial Network (NTN) as a target base station, transmitting information about a time gap related to transmission of a RACH preamble (Random Access Channel preamble) to the first base station; and At least one non-transitory computer-readable recording medium comprising transmitting the RACH preamble to the target base station. In UE (User Equipment), RF (Radio Frequency) transmitter and receiver; and A processor connected to the RF transceiver, A UE in which the processor controls the RF transceiver to report measurement information to a first base station, receives a HO (Handover) command from the first base station, and transmits information about a time gap related to transmission of a RACH preamble (Random Access Channel preamble) to the first base station based on the HO command setting a base station related to a Non-Terrestrial Network (NTN) as a target base station, and transmits the RACH preamble to the target base station. In a processing device that controls UE (User Equipment), at least one processor; and At least one memory connected to said at least one processor and storing instructions that perform operations when executed by said at least one processor, The above actions are, Report measurement information to the first base station; Receive a HO (Handover) command from the first base station; Based on the above HO command setting a base station related to a Non-Terrestrial Network (NTN) as a target base station, transmitting information about a time gap related to transmission of a RACH preamble (Random Access Channel preamble) to the first base station; and A processing device comprising transmitting the RACH preamble to the target base station. In the method by the first base station, A step of receiving measurement information from UE (User Equipment); A step of transmitting a HO (Handover) command determined based on the above measurement information to the UE; and A method comprising the step of receiving information about a time gap related to transmission of a RACH preamble (Random Access Channel preamble) from the UE based on the above HO command setting a base station related to a Non-Terrestrial Network (NTN) as a target base station. In Article 13, A method in which the first base station specifies a time period during which data transmission and reception with the UE is temporarily suspended based on the time gap. At the base station, RF (Radio Frequency) transmitter and receiver; and A processor connected to the RF transceiver, A base station, wherein the processor controls the RF transceiver to receive measurement information from a UE (User Equipment), transmits a HO (Handover) command determined based on the measurement information to the UE, and receives information about a time gap related to transmission of a RACH preamble (Random Access Channel preamble) from the UE based on the HO command setting a base station related to a NTN (Non-Terrestrial Network) as a target base station.

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