Communication system

Abstract

A communication system comprises: an uncrewed aerial vehicle (UAV); a UAV controller (UAV-C) that controls the UAV; and a network including a network node. The UAV, the UAV-C, or the network node is configured to switch between command and control (C2) communication using a switching determination index.

Description

Communication system

[0001] This disclosure relates to wireless communication technology.

[0002] In the 3GPP (3rd Generation Partnership Project), a standardization body for mobile communication systems, the successor to Long Term Evolution (LTE), one of the 4th generation wireless access systems, Long Term Evolution Advanced (LTE-A) (see Non-Patent Document 1), the 5th generation (hereinafter sometimes referred to as "5G") wireless access system is being studied (for example, Non-Patent Document 2). The technology for the 5G radio section is called "New Radio Access Technology" ("New Radio" is abbreviated as "NR"). The NR system is being studied based on the LTE system and the LTE-A system.

[0003] For example, in Europe, the requirements for 5G have been summarized by a group called METIS (see Non-Patent Document 3). In the 5G wireless access system, compared with the LTE system, the system capacity is 1000 times, the data transmission speed is 100 times, the data processing delay is 1 / 5, and the number of simultaneously connected communication terminals is 100 times. Further reduction of power consumption and cost reduction of devices are listed as requirements (see Non-Patent Document 3).

[0004] In order to meet such requirements, 3GPP is conducting a standard study on 5G (see Non-Patent Documents 4 to 23).

[0005] As the access method of NR, OFDM (Orthogonal Frequency Division Multiplexing) is used in the downlink direction, and OFDM and DFT-s-OFDM (Discrete Fourier Transform-spread-OFDM) are used in the uplink direction. Also, like the LTE and LTE-A systems, the 5G system does not include circuit switching and is only a packet communication system.

[0006] NR allows for the use of higher frequencies compared to LTE, in order to improve transmission speed and reduce processing delay.

[0007] In noise reduction (NR), which sometimes uses higher frequencies than LTE, cell coverage is ensured by forming a narrow beam-shaped transmission and reception range (beamforming) and changing the direction of the beam (beam sweeping).

[0008] The decisions regarding the frame configuration in the NR system under 3GPP, as described in Non-Patent Document 1 (Chapter 5), will be explained using Figure 1. Figure 1 is an explanatory diagram showing the configuration of a radio frame used in an NR communication system. In Figure 1, one radio frame is 10 ms. The radio frame is divided into 10 subframes of equal size. In the NR frame configuration, one or more numerologies, i.e., one or more subcarrier spacings (SCS), are supported. In NR, regardless of the subcarrier spacing, one subframe is 1 ms, and one slot consists of 14 symbols. Furthermore, the number of slots contained in one subframe is one for a subcarrier spacing of 15 kHz, and the number of slots for other subcarrier spacings increases proportionally to the subcarrier spacing (see Non-Patent Document 11 (3GPP TS38.211)).

[0009] The decisions regarding the channel configuration in the NR system at 3GPP are described in Non-Patent Document 2 (Chapter 5) and Non-Patent Document 11.

[0010] A Physical Broadcast Channel (PBCH) is a channel used for downlink transmission from a base station (hereinafter sometimes simply referred to as "base station") to a communication terminal (hereinafter sometimes simply referred to as "communication terminal" or "terminal") such as a mobile terminal (hereinafter sometimes simply referred to as "mobile terminal"). The PBCH is transmitted together with a Downlink Synchronization Signal.

[0011] In NR, the downlink synchronization signal consists of a primary synchronization signal (P-SS) and a secondary synchronization signal (S-SS). The synchronization signal is transmitted from the base station as a synchronization signal burst (Synchronization Signal Burst; hereinafter sometimes referred to as SS burst) at a predetermined period and for a predetermined duration. The SS burst is composed of a synchronization signal block (Synchronization Signal Block; hereinafter sometimes referred to as SS block) for each beam of the base station.

[0012] The base station transmits SS blocks of each beam, switching beams, within the duration of the SS burst. The SS blocks consist of P-SS, S-SS, and PBCH.

[0013] The Physical Downlink Control Channel (PDCCH) is the channel used for downlink transmission from the base station to the communication terminal. The PDCCH carries Downlink Control Information (DCI). DCI includes resource allocation information for the Downlink Shared Channel (DL-SCH), one of the transport channels described later, resource allocation information for the Paging Channel (PCH), another transport channel described later, and HARQ (Hybrid Automatic Repeat reQuest) information related to the DL-SCH. In addition, DCI may include Uplink Scheduling Grant. DCI may also include Ack (Acknowledgement) / Nack (Negative Acknowledgement), which are response signals to uplink transmissions. Furthermore, to allow for flexible switching between DL / UL within a slot, DCI may include a Slot Format Indication (SFI). PDCCH, or DCI, is also called an L1 / L2 control signal.

[0014] In NR, a time and frequency range is defined as a candidate range for PDCCH. This range is called the Control Resource Set (CORESET). The communication terminal monitors the CORESET and acquires PDCCH.

[0015] The Physical Downlink Shared Channel (PDSCH) is a channel used for downlink transmission from a base station to a communication terminal. The PDSCH is mapped to the Downlink Shared Channel (DL-SCH), which is a transport channel, and the PCH, which is also a transport channel.

[0016] The Physical Uplink Control Channel (PUCCH) is the channel used for uplink transmission from the communication terminal to the base station. The PUCCH carries Uplink Control Information (UCI). UCI includes Ack / Nack, which are response signals to downlink transmissions, Channel State Information (CSI), and Scheduling Request (SR). CSI consists of the Rank Indicator (RI), Precoding Matrix Indicator (PMI), and Channel Quality Indicator (CQI) reports. RI is the rank information of the channel matrix in MIMO (Multiple Input Multiple Output). PMI is the information of the precoding weight matrix used in MIMO. CQI is quality information indicating the quality of the received data or the quality of the communication channel. UCI may be carried by the PUCCH, which will be described later. PUCCH, or UCI, is also called the L1 / L2 control signal.

[0017] The Physical Uplink Shared Channel (PUSCH) is a channel used for uplink transmission from a communication terminal to a base station. The Uplink Shared Channel (UL-SCH), which is one of the transport channels, is mapped to the PUSCH.

[0018] A Physical Random Access Channel (PRACH) is a channel used for uplink transmission from a communication terminal to a base station. The PRACH carries a random access preamble.

[0019] The downlink reference signal (RS) is a well-known symbol in NR (Noise Reduction) communication systems. The following four types of downlink reference signals are defined: UE-specific reference signals: Demodulation Reference Signal (DM-RS), Phase Tracking Reference Signal (PT-RS), Positioning Reference Signal (PRS), and Channel State Information Reference Signal (CSI-RS). Measurements at the physical layer of the communication terminal include Reference Signal Received Power (RSRP) measurement and Reference Signal Received Quality (RSRQ) measurement.

[0020] Similarly, the uplink reference signals are also known symbols in NR (Noise Reduction) communication systems. The following three types of uplink reference signals are defined: Data Demodulation Reference Signal (DM-RS), Phase Tracking Reference Signal (PT-RS), and Sounding Reference Signal (SRS).

[0021] This section explains the transport channel described in Non-Patent Document 2 (Chapter 5). Of the downlink transport channels, the broadcast channel (BCH) broadcasts to the entire coverage of the base station (cell). The BCH is mapped to the physical broadcast channel (PBCH).

[0022] Downlink Shared Channels (DL-SCH) are subject to HARQ-based retransmission control. DL-SCH can broadcast to the entire coverage of a base station (cell). DL-SCH supports dynamic or semi-static resource allocation. Semi-static resource allocation is also called semi-persistent scheduling. DL-SCH supports discontinuous reception (DRX) for communication terminals to reduce power consumption. DL-SCH is mapped to the physical downlink shared channel (PDSCH).

[0023] Paging Channels (PCHs) support DRX for communication terminals to enable low power consumption for those terminals. PCHs are required to broadcast across the entire coverage of a base station (cell). PCHs are mapped to physical resources, such as Physical Downlink Shared Channels (PDSCHs), which are dynamically available for traffic.

[0024] Among the uplink transport channels, the Uplink Shared Channel (UL-SCH) is subject to retransmission control by HARQ. UL-SCH supports dynamic or quasi-static resource allocation. Quasi-static resource allocation is also called configured grant. UL-SCH is mapped to the physical uplink shared channel (PUSCH).

[0025] Random Access Channels (RACHs) are limited to control information. RACHs carry a risk of collisions. RACHs are mapped to Physical Random Access Channels (PRACHs).

[0026] This section explains HARQ. HARQ is a technology that improves the communication quality of a transmission line by combining Automatic Repeat Request (ARQ) and Forward Error Correction. HARQ has the advantage that error correction through retransmission works effectively even for transmission lines where the communication quality changes. In particular, it is possible to further improve quality by combining the reception result of the initial transmission and the reception result of the retransmission during retransmission.

[0027] Here is an example of how to retransmit data. If the receiving side is unable to correctly decode the received data, in other words, if a CRC (Cyclic Redundancy Check) error occurs (CRC = NG), the receiving side sends "Nack" to the sending side. Upon receiving "Nack," the sending side retransmits the data. If the receiving side is able to correctly decode the received data, in other words, if no CRC error occurs (CRC = OK), the receiving side sends "Ack" to the sending side. Upon receiving "Ack," the sending side sends the next data.

[0028] Here are some other examples of retransmission methods. If a CRC error occurs at the receiving end, the receiving end requests retransmission from the sending end. This request is made by toggling the NDI (New Data Indicator). Upon receiving the retransmission request, the sending end retransmits the data. If no CRC error occurs at the receiving end, no retransmission request is made. If the sending end does not receive a retransmission request within a specified time, it is assumed that no CRC error occurred at the receiving end.

[0029] This section explains the logical channel described in Non-Patent Document 1 (Chapter 6). The Broadcast Control Channel (BCCH) is a downstream channel for broadcasting system control information. The BCCH, being a logical channel, is mapped to the broadcast channel (BCH), which is a transport channel, or to the downstream shared channel (DL-SCH).

[0030] The Paging Control Channel (PCCH) is a downstream channel for transmitting changes to paging information and system information. The PCCH, being a logical channel, is mapped to the Paging Channel (PCH), which is a transport channel.

[0031] The Common Control Channel (CCCH) is a channel used to transmit control information between a communication terminal and a base station. The CCCH is used when a communication terminal does not have an RRC connection with the network. In the downlink direction, the CCCH is mapped to the downlink common channel (DL-SCH), which is a transport channel. In the uplink direction, the CCCH is mapped to the uplink common channel (UL-SCH), which is a transport channel.

[0032] A Dedicated Control Channel (DCCH) is a channel that transmits individual control information between a communication terminal and the network on a one-to-one basis. DCCH is used when a communication terminal has an RRC connection with the network. DCCH is mapped to the Uplink Shared Channel (UL-SCH) for uplink traffic and to the Downlink Shared Channel (DL-SCH) for downlink traffic.

[0033] A Dedicated Traffic Channel (DTCH) is a one-to-one communication channel to a communication terminal for transmitting user information. DTCHs exist for both uplink and downlink traffic. Uplink DTCHs are mapped to the Uplink Shared Channel (UL-SCH), and downlink DTCHs are mapped to the Downlink Shared Channel (DL-SCH).

[0034] Location tracking of communication terminals is performed in units of areas consisting of one or more cells. Location tracking is performed to track the location of communication terminals even when they are in standby mode, and to enable them to be called, in other words, to enable them to receive calls. This area used for location tracking of communication terminals is called a Tracking Area (TA).

[0035] In NR, calling communication terminals within a range smaller than the tracking area is supported. This range is called the RAN Notification Area (RNA). Paging of communication terminals in the RRC_INACTIVE state, as described later, is performed within this range.

[0036] In NR (Noise Reduction), carrier aggregation (CA), which involves aggregating two or more component carriers (CCs), is being considered to support wide frequency bandwidths. CA is described in Non-Patent Document 1.

[0037] When a CA (Carrier Acquisition) is configured, the UE (User Equipment) which is a communication terminal has a single RRC (Rapid Relay Control) connection to the network (NW). In the RRC connection, one serving cell provides NAS (Non-Access Stratum) mobility information and security input. This cell is called the primary cell (PCell). Depending on the capabilities of the UE, secondary cells (SCells) are configured together with the PCell to form a set of serving cells. A set of serving cells consisting of one PCell and one or more SCells is configured for one UE.

[0038] Furthermore, in 3GPP, in order to further increase communication capacity, there is dual connectivity (DC), in which a UE connects to two base stations for communication. DC is described in Non-Patent Documents 1 and 22.

[0039] In dual connectivity (DC) base stations, one is sometimes called the "Master Node (MN)" and the other the "Secondary Node (SN)". The serving cells composed of the master base station are sometimes collectively called the Master Cell Group (MCG), and the serving cells composed of the secondary base station are sometimes collectively called the Secondary Cell Group (SCG). In a DC, the primary cell within the MCG or SCG is called a Special Cell (SpCell or SPCell). A Special Cell in an MCG is called a PCell, and a Special Cell in an SCG is called a Primary SCG Cell (PSCell).

[0040] Furthermore, in NR, the base station pre-configures a portion of the carrier frequency band (hereinafter sometimes referred to as the Bandwidth Part (BWP)) for the UE, and the UE performs transmission and reception with the base station in the BWP, thereby reducing power consumption in the UE.

[0041] Furthermore, 3GPP is considering supporting services (or applications) using side-link (SL) communication (also called PC5 communication) in both the Evolved Packet System (EPS) described later and the 5G core system (see Non-Patent Documents 1, 2, 26-28). SL communication takes place between terminals. Examples of services using SL communication include V2X (Vehicle-to-everything) services and proximity services. In SL communication, not only direct communication between terminals but also communication between the UE and NW via relay has been proposed (see Non-Patent Documents 26, 28).

[0042] The physical channels used for SL (see Non-Patent Documents 2 and 11) will be described. The physical sidelink broadcast channel (PSBCH: Physical sidelink broadcast channel) carries information related to system synchronization and is transmitted from the UE.

[0043] The physical sidelink control channel (PSCCH: Physical sidelink control channel) carries control information from the UE for sidelink communication and V2X sidelink communication.

[0044] The physical sidelink shared channel (PSSCH: Physical sidelink shared channel) carries data from the UE for sidelink communication and V2X sidelink communication.

[0045] The physical sidelink feedback channel (PSFCH: Physical sidelink feedback channel) carries HARQ feedback on the sidelink from the UE that has received the PSSCH transmission to the UE that has transmitted the PSSCH.

[0046] The transport channels used for SL (see Non-Patent Document 1) will be described. The sidelink broadcast channel (SL-BCH: Sidelink broadcast channel) has a predetermined transport format and is mapped to the PSBCH, which is a physical channel.

[0047] The sidelink shared channel (SL-SCH) supports notification transmission. The SL-SCH supports both UE autonomous resource selection and resource allocation scheduled by the base station. There is a risk of collision in UE autonomous resource selection, and there is no collision when the UE is allocated individual resources by the base station. Also, the SL-SCH supports dynamic link adaptation by changing the transmission power, modulation, and coding. The SL-SCH is mapped to the physical channel PSSCH.

[0048] The logical channels used for SL (see Non-Patent Document 2) will be described. The sidelink broadcast control channel (SBCCH) is a sidelink channel for notifying sidelink system information from one UE to other UEs. The SBCCH is mapped to the transport channel SL-BCH.

[0049] The sidelink traffic channel (STCH) is a one-to-many sidelink traffic channel for transmitting user information from one UE to other UEs. The STCH is used only by UEs with sidelink communication capabilities and UEs with V2X sidelink communication capabilities. One-to-one communication between two UEs with sidelink communication capabilities is also realized by the STCH. The STCH is mapped to the transport channel SL-SCH.

[0050] The sidelink control channel (SCCH) is a sidelink control channel for transmitting control information from one UE to other UEs. The SCCH is mapped to the transport channel SL-SCH.

[0051] In LTE, SL communication was limited to broadcast only. In NR, support for unicast and groupcast in addition to broadcast is being considered for SL communication (see Non-Patent Document 27 (3GPP TS23.287)).

[0052] In SL, unicast and groupcast communications support HARQ feedback (Ack / Nack), CSI reporting, and other features.

[0053] Furthermore, 3GPP is considering Integrated Access and Backhaul (IAB), which involves wirelessly conducting both the access link between the UE and the base station, and the backhaul link between base stations (see Non-Patent Documents 2, 20, and 29).

[0054] 3GPP is considering supporting uncrewed aerial systems (UAS) in its mobile communication systems (see Non-Patent Document 30). For example, methods for communicating with terminals mounted on uncrewed aerial vehicles (UAVs) are being considered.

[0055] 3GPP TS36.300 V18.3.03GPP TS38.300 V18.3.0“Scenarios, requirements and KPIs for 5G mobile and wireless system”、ICT-317669-METIS / D1.13GPP TR23.799 V14.0.03GPP TR38.801 V14.0.03GPP TR38.802 V14.2.03GPP TR38.804 V14.0.03GPP TR38.912 V16.0.03GPP RP-1721153GPP TS23.501 V19.1.03GPP TS38.211 V18.4.03GPP TS38.212 V18.4.03GPP TS38.213 V18.4.03GPP TS38.214 V18.4.03GPP TS38.321 V18.3.03GPP TS38.322 V18.1.03GPP TS38.323 V18.3.03GPP TS37.324 V18.0.03GPP TS38.331 V18.3.03GPP TS38.401 V18.3.03GPP TS38.413 V18.3.03GPP TS37.340 V18.3.03GPP TS38.423 V18.3.03GPP TS38.305 V18.3.03GPP TS23.273 V19.0.03GPP TR23.703 V12.0.03GPP TS23.287 V18.4.03GPP TS23.303 V18.0.03GPP TS38.340 V18.1.03GPP TS23.256 V19.1.03GPP TS23.586 V18.6.03GPP TS37.320 V18.3.03GPP TS23.304 V19.1.0

[0056] In the 3GPP mobile communication system, support for Uncrewed Aerial Systems (UAS) has been considered. For example, methods for establishing communication between UAVs and UAV-C (UAV Controllers) that control them, as well as methods for establishing communication between UAVs themselves, have been studied. However, unlike vehicles on the road, UAVs move through the air, making situation-dependent control crucial. Conventional technologies may not be able to adequately achieve such situation-dependent control of UAVs.

[0057] In view of the above issues, one of the objectives of this disclosure is to provide a communication system that enables control according to the status of the UAV.

[0058] The communication system of this disclosure comprises at least one uncrewed aerial vehicle (UAV), a UAV controller (UAV-C) that controls the at least one UAV, and a network including at least one network node that communicates with the at least one UAV and the UAV-C. The UAV and the UAV-C are configured to perform a first communication in which the UAV and the UAV-C are directly connected to each other to perform command and control (C2) communication, and a second communication in which the UAV and the UAV-C are connected via the network to perform C2 communication. The UAV, the UAV-C, or the network node is configured to determine whether to switch between the first communication and the second communication using a switching decision index.

[0059] According to the above configuration, a communication system capable of controlling the UAV according to its status can be provided.

[0060] The purpose, features, aspects, and advantages of this disclosure will become clearer from the following detailed description and accompanying drawings.

[0061] This is an explanatory diagram showing the configuration of a wireless frame used in an NR communication system. This is a block diagram showing the overall configuration of an NR communication system 210 as discussed in 3GPP. This is a configuration diagram of a DC by a base station connected to an NG core. This is a block diagram showing the configuration of a mobile terminal 202 shown in Figure 2. This is a block diagram showing the configuration of a base station 213 shown in Figure 2. This is a block diagram showing the configuration of the 5GC section. This is a flowchart outlining the process from cell search to standby operation performed by a communication terminal (UE) in an NR communication system. This is a diagram showing an example of a cell configuration in an NR system. This is a connection configuration diagram showing an example of a terminal connection configuration in SL communication. This is a connection configuration diagram showing an example of a base station connection configuration that supports access backhaul integration. This is a diagram showing an example of a C2 communication switching process from indirect C2 communication to direct C2 communication for C2 communication between a UAV and a UAV-C in Embodiment 1. This is a diagram showing another example of a C2 communication switching process from indirect C2 communication to direct C2 communication for C2 communication between a UAV and a UAV-C in Embodiment 1. This figure shows an example sequence of C2 communication switching processing from direct C2 communication to indirect C2 communication for C2 communication between a UAV and a UAV-C, according to Embodiment 1. This figure shows another example sequence of C2 communication switching processing from direct C2 communication to indirect C2 communication for C2 communication between a UAV and a UAV-C, according to Embodiment 1. This figure shows another example sequence of C2 communication switching processing from indirect C2 communication to direct C2 communication for C2 communication between a UAV and a UAV-C, according to Embodiment 1. This figure shows another example sequence of C2 communication switching processing from indirect C2 communication to direct C2 communication for C2 communication between a UAV and a UAV-C, according to Embodiment 1. This figure shows an example sequence of UAV-to-UAV distance notification processing for UAV-C, according to Embodiment 2. This figure shows an example sequence of UAV-to-UAV distance alarm notification processing for UAV-C, according to Embodiment 2. This figure shows another example sequence of UAV-to-UAV distance alarm notification processing for UAV-C, according to Embodiment 2. This figure shows another example sequence for the UAV-C inter-UAV distance alarm notification process in Embodiment 2. This figure shows an example sequence for the UAV-C UAV altitude alarm notification process in Embodiment 3.This figure shows an example sequence for notifying a UAV altitude alarm to a UE in Embodiment 4. This figure shows another example sequence for notifying a UAV altitude alarm to a UE in Embodiment 4. This figure shows another example sequence for notifying a UAV altitude alarm to a UE in Embodiment 4. This figure shows another example sequence for notifying a UAV altitude alarm to a UE in Embodiment 4. This figure shows another example sequence for notifying a UAV distance alarm to a UE in Embodiment 5. This figure shows another example sequence for notifying a UAV distance alarm to a UE in Embodiment 5. This figure shows an example sequence for collecting UAV-related data using Log MDT in Embodiment 6. This figure shows an example sequence for collecting UAV-related data using Immediate MDT in Embodiment 6. This is a conceptual diagram of what happens when a UAV performing C2 communication moves.

[0062] Embodiment 1. Figure 2 is a block diagram showing the overall configuration of the NR communication system 210 discussed in 3GPP. Figure 2 will be explained. The radio access network is called NG-RAN (Next Generation Radio Access Network) 211. A mobile terminal device (hereinafter referred to as "Mobile Terminal (User Equipment: UE)") 202, which is a communication terminal device, can communicate wirelessly with a base station device (hereinafter referred to as "NR base station (NG-RAN NodeB: gNB)") 213 and transmits and receives signals wirelessly. The NG-RAN 211 is composed of one or more NR base stations 213.

[0063] Here, "communication terminal equipment" includes not only mobile terminal equipment such as portable mobile phone terminals, but also stationary devices such as sensors. In the following explanation, "communication terminal equipment" may sometimes be simply referred to as "communication terminal."

[0064] The Access Stratum (AS) protocol is terminated between UE202 and NG-RAN211. Examples of AS protocols used include RRC (Radio Resource Control), SDAP (Service Data Adaptation Protocol), PDCP (Packet Data Convergence Protocol), RLC (Radio Link Control), MAC (Medium Access Control), and PHY (Physical layer). RRC is used in the control plane (hereinafter sometimes referred to as C-plane, C-Plane, or CP), SDAP is used in the user plane (hereinafter sometimes referred to as U-plane, U-Plane, or UP), and PDCP, MAC, RLC, and PHY are used in both the C-plane and U-plane.

[0065] The control protocol RRC (Radio Resource Control) between UE202 and NR base station 213 performs functions such as broadcasting, paging, and RRC connection management. The states of NR base station 213 and UE202 in RRC are RRC_IDLE, RRC_CONNECTED, and RRC_INACTIVE.

[0066] In RRC_IDLE mode, functions such as PLMN (Public Land Mobile Network) selection, System Information (SI) broadcasting, paging, cell re-selection, and mobility are performed. In RRC_CONNECTED mode, the mobile terminal has an RRC connection and can send and receive data with the network. In RRC_CONNECTED mode, functions such as handover (HO) and neighbor cell measurement are performed. In RRC_INACTIVE mode, while the connection between the 5G core unit 214 and the NR base station 213 is maintained, functions such as System Information (SI) broadcasting, paging, cell re-selection, and mobility are performed.

[0067] The gNB 213 is connected via an NG interface to a 5G core unit (hereinafter sometimes referred to as the "5GC unit") 214, which includes an Access and Mobility Management Function (AMF), a Session Management Function (SMF), or a User Plane Function (UPF). Control information and / or user data are communicated between the gNB 213 and the 5GC unit 214. The NG interface is a collective term for the N2 interface between the gNB 213 and the AMF 220, the N3 interface between the gNB 213 and the UPF 221, the N11 interface between the AMF 220 and the SMF 222, and the N4 interface between the UPF 221 and the SMF 222. Multiple 5GC units 214 may be connected to a single gNB 213. The gNB213 units are connected via an Xn interface, and control information and / or user data are communicated between them.

[0068] The 5GC unit 214 is a higher-level device, specifically a higher-level node, and controls the connection between the NR base station 213 and the mobile terminal (UE) 202, and distributes paging signals to one or more NR base stations (gNB) 213 and / or LTE base stations (E-UTRAN NodeB: eNB). The 5GC unit 214 also performs mobility control in the idle state. The 5GC unit 214 manages the tracking area list when the mobile terminal 202 is in the idle state, in the inactive state, and in the active state. The 5GC unit 214 initiates the paging protocol by sending a paging message to a cell belonging to the tracking area where the mobile terminal 202 is registered.

[0069] The gNB213 may constitute one or more cells. If one gNB213 constitutes multiple cells, each cell is configured to communicate with the UE202.

[0070] The gNB213 may be divided into a Central Unit (CU) 215 and a Distributed Unit (DU) 216. One CU 215 is configured within the gNB213. One or more DU 216 are configured within the gNB213. One DU 216 constitutes one or more cells. The CU 215 is connected to the DU 216 by an F1 interface, and control information and / or user data are communicated between the CU 215 and the DU 216. The F1 interface consists of an F1-C interface and an F1-U interface. The CU 215 is responsible for the functions of the RRC, SDAP, and PDCP protocols, and the DU 216 is responsible for the functions of the RLC, MAC, and PHY protocols. One or more TRPs (Transmission Reception Points) 219 may be connected to the DU 216. The TRP219 transmits and receives wireless signals to and from the UE.

[0071] CU215 may be divided into a C-plane CU (CU-C) 217 ​​and a U-plane CU (CU-U) 218. One CU-C 217 is configured within CU215. One or more CU-U 218s are configured within CU215. CU-C 217 is connected to CU-U 218 by an E1 interface, and control information is communicated between CU-C 217 and CU-U 218. CU-C 217 is connected to DU216 by an F1-C interface, and control information is communicated between CU-C 217 and DU216. CU-U 218 is connected to DU216 by an F1-U interface, and user data is communicated between CU-U 218 and DU216.

[0072] In a 5G communication system, the Unified Data Management (UDM) function and Policy Control Function (PCF) described in Non-Patent Document 10 (3GPP TS23.501) may be included. The UDM and / or PCF may be included in the 5GC unit 214 in Figure 2.

[0073] In a 5G communication system, a Location Management Function (LMF) as described in Non-Patent Document 24 (3GPP TS38.305) may be provided. The LMF may be connected to a base station via an AMF, as disclosed in Non-Patent Document 25 (3GPP TS23.273).

[0074] In a 5G communication system, the Non-3GPP Interworking Function (N3IWF) described in Non-Patent Document 10 (3GPP TS23.501) may be included. In non-3GPP access with a UE, the N3IWF may terminate the Access Network (AN) with the UE.

[0075] Figure 3 shows the configuration of a DC (Dual Connectivity) connected to the NG core. In Figure 3, solid lines indicate U-Plane connections, and dashed lines indicate C-Plane connections. In Figure 3, the master base station 240-1 may be a gNB or an eNB. Similarly, the secondary base station 240-2 may be a gNB or an eNB. For example, in Figure 3, a DC configuration in which the master base station 240-1 is a gNB and the secondary base station 240-2 is an eNB may be called NG-EN-DC. Figure 3 shows an example in which the U-Plane connection between the 5GC unit 214 and the secondary base station 240-2 is performed via the master base station 240-1, but it may also be performed directly between the 5GC unit 214 and the secondary base station 240-2. Furthermore, in Figure 3, instead of the 5GC unit 214, an EPC (Evolved Packet Core), which is a core network connected to the LTE system and the LTE-A system, may be connected to the master base station 240-1. A U-Plane connection may also be directly established between the EPC and the secondary base station 240-2.

[0076] Figure 4 is a block diagram showing the configuration of the mobile terminal 202 shown in Figure 2. The transmission process of the mobile terminal 202 shown in Figure 4 will now be explained. First, control data from the control unit 310 and user data from the application unit 302 are sent to the protocol processing unit 301. Buffering of the control data and user data may be performed. The buffers for the control data and user data may be provided in the control unit 310, the application unit 302, or the protocol processing unit 301. The protocol processing unit 301 performs protocol processing such as SDAP, PDCP, RLC, MAC, etc., for example, determining the destination base station in DC, etc., and adding headers in each protocol. The data that has undergone protocol processing is passed to the encoder unit 304, where encoding processing such as error correction is performed. There may be data that is output directly from the protocol processing unit 301 to the modulation unit 305 without undergoing encoding processing. The data encoded by the encoder unit 304 is then modulated by the modulation unit 305. Precoding in MIMO may be performed in the modulation unit 305. The modulated data is converted into a baseband signal, then output to the frequency conversion unit 306, where it is converted to a wireless transmission frequency. The transmission signal is then sent from antennas 307-1 to 307-4 to the base station 213. Figure 4 illustrates the case with four antennas, but the number of antennas is not limited to four.

[0077] Furthermore, the reception processing of the mobile terminal 202 is performed as follows: A radio signal from the base station 213 is received by antennas 307-1 to 307-4. The received signal is converted from the radio reception frequency to a baseband signal by the frequency conversion unit 306, and demodulation processing is performed by the demodulation unit 308. Weight calculation and multiplication processing may also be performed in the demodulation unit 308. The demodulated data is passed to the decoder unit 309, where decoding processing such as error correction is performed. The decoded data is passed to the protocol processing unit 301, where protocol processing such as MAC, RLC, PDCP, and SDAP is performed, for example, operations such as header removal in each protocol. Of the data that has undergone protocol processing, control data is passed to the control unit 310, and user data is passed to the application unit 302.

[0078] The series of processes performed by the mobile terminal 202 are controlled by the control unit 310. Therefore, although the control unit 310 is omitted in Figure 4, it is connected to each of the units 302, 304 to 309.

[0079] Each part of the mobile terminal 202, for example, the control unit 310, the protocol processing unit 301, the encoder unit 304, and the decoder unit 309, are implemented by a processing circuit that includes, for example, a processor and memory. For example, the control unit 310 is implemented by the processor executing a program that describes a series of processes for the mobile terminal 202. The program that describes a series of processes for the mobile terminal 202 is stored in memory. Examples of memory include non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), and flash memory. Each part of the mobile terminal 202, for example, the control unit 310, the protocol processing unit 301, the encoder unit 304, and the decoder unit 309, may also be implemented by a dedicated processing circuit such as an FPGA (Field Programmable Gate Array), ASIC (Application Specific Integrated Circuit), or DSP (Digital Signal Processor). In Figure 4, the number of antennas used by the mobile terminal 202 for transmission and the number of antennas used for reception may be the same or different.

[0080] Figure 5 is a block diagram showing the configuration of the base station 213 shown in Figure 2. The transmission process of the base station 213 shown in Figure 5 will now be explained. The EPC communication unit 401 transmits and receives data between the base station 213 and the EPC. The 5GC communication unit 412 transmits and receives data between the base station 213 and the 5GC (5GC unit 214, etc.). The other base station communication unit 402 transmits and receives data with other base stations. The EPC communication unit 401, the 5GC communication unit 412, and the other base station communication unit 402 each exchange information with the protocol processing unit 403. Control data from the control unit 411, as well as user data and control data from the EPC communication unit 401, the 5GC communication unit 412, and the other base station communication unit 402, are sent to the protocol processing unit 403. Buffering of control data and user data may be performed. A buffer for control data and user data may be provided in the control unit 411, the EPC communication unit 401, the 5GC communication unit 412, or the other base station communication unit 402.

[0081] The protocol processing unit 403 performs protocol processing such as SDAP, PDCP, RLC, and MAC, for example, routing of transmission data in DCs, and adding headers for each protocol. The processed data is passed to the encoder unit 405, where it undergoes encoding processing such as error correction. There may be data that is output directly from the protocol processing unit 403 to the modulation unit 406 without undergoing encoding processing. Data may also be sent from the protocol processing unit 403 to the other base station communication unit 402. For example, in a DC, data sent from the 5GC communication unit 412 or the EPC communication unit 401 may be sent to another base station, such as a secondary base station, via the other base station communication unit 402. The encoded data is then modulated in the modulation unit 406. Precoding in MIMO may be performed in the modulation unit 406. The modulated data is converted into a baseband signal and then output to the frequency conversion unit 407, where it is converted to a wireless transmission frequency. Subsequently, a transmission signal is sent from antennas 408-1 to 408-4 to one or more mobile terminals 202. Figure 5 illustrates the case where there are four antennas, but the number of antennas is not limited to four.

[0082] Furthermore, the reception processing at base station 213 is performed as follows: A radio signal from one or more mobile terminals 202 is received by antennas 408-1 to 408-4. The received signal is converted from the radio reception frequency to a baseband signal by the frequency conversion unit 407, and demodulation processing is performed by the demodulation unit 409. The demodulated data is passed to the decoder unit 410, where decoding processing such as error correction is performed. The decoded data is passed to the protocol processing unit 403, where protocol processing such as MAC, RLC, PDCP, and SDAP is performed, for example, operations such as header removal in each protocol. Of the data that has undergone protocol processing, control data is passed to the control unit 411, the 5GC communication unit 412, the EPC communication unit 401, or the other base station communication unit 402, and user data is passed to the 5GC communication unit 412, the EPC communication unit 401, or the other base station communication unit 402. Data sent from another base station communication unit 402 may be sent to the 5GC communication unit 412 or the EPC communication unit 401. This data may be, for example, uplink data sent to the 5GC communication unit 412 or the EPC communication unit 401 via another base station in a DC.

[0083] The series of processes performed by the base station 213 are controlled by the control unit 411. Therefore, although the control unit 411 is omitted in Figure 5, it is connected to each of the units 401, 402, 405-410, and 412.

[0084] Each part of the base station 213, for example, the control unit 411, the protocol processing unit 403, the 5GC communication unit 412, the EPC communication unit 401, the other base station communication unit 402, the encoder unit 405, and the decoder unit 410, are implemented as processing circuits including a processor and memory, similar to the mobile terminal 202 described above, or as dedicated processing circuits such as FPGA, ASIC, and DSP. In Figure 5, the number of antennas used by the base station 213 for transmission and the number of antennas used for reception may be the same or different.

[0085] As an example of the configuration of the CU215 shown in Figure 2, a configuration may be used in which a DU communication unit is added, excluding the encoder unit 405, modulation unit 406, frequency conversion unit 407, antennas 408-1 to 408-4, demodulation unit 409, and decoder unit 410 shown in Figure 5. The DU communication unit is connected to the protocol processing unit 403. The protocol processing unit 403 in the CU215 performs protocol processing such as PDCP and SDAP.

[0086] As an example of the DU216 configuration shown in Figure 2, a configuration may be used in which a CU communication unit is provided, excluding the EPC communication unit 401, other base station communication unit 402, and 5GC communication unit 412 shown in Figure 5. The CU communication unit is connected to the protocol processing unit 403. The protocol processing unit 403 in the DU216 performs protocol processing such as PHY, MAC, and RLC.

[0087] Figure 6 is a block diagram showing the configuration of the 5GC unit. Figure 6 shows the configuration of the 5GC unit 214 shown in Figure 2. Figure 6 shows the case where the 5GC unit 214 shown in Figure 2 includes the configuration of the AMF, SMF, and UPF. In the example shown in Figure 6, the AMF may have the function of the control plane control unit 525, the SMF may have the function of the session management unit 527, and the UPF may have the functions of the user plane communication unit 523 and the Data Network communication unit 521. The Data Network communication unit 521 transmits and receives data between the 5GC unit 214 and the Data Network. The base station communication unit 522 transmits and receives data between the 5GC unit 214 and the base station 213 via the NG interface. User data sent from the Data Network is passed from the Data Network communication unit 521 to the base station communication unit 522 via the user-plane communication unit 523, and then transmitted to one or more base stations 213. User data sent from the base station 213 is passed from the base station communication unit 522 to the Data Network communication unit 521 via the user-plane communication unit 523, and then transmitted to the Data Network.

[0088] Control data sent from base station 213 is passed from base station communication unit 522 to control plane control unit 525. The control plane control unit 525 may pass the control data to session management unit 527. Control data may also be sent from Data Network. Control data sent from Data Network may be sent from Data Network communication unit 521 to session management unit 527 via user plane communication unit 523. The session management unit 527 may also send the control data to control plane control unit 525.

[0089] The user-plane communication unit 523 includes the PDU processing unit 523-1 and the mobility anchoring unit 523-2, and performs all processing for the user-plane (hereinafter sometimes referred to as U-Plane). The PDU processing unit 523-1 processes data packets, for example, sending and receiving packets with the Data Network communication unit 521 and sending and receiving packets with the base station communication unit 522. The mobility anchoring unit 523-2 is responsible for maintaining the data path when the UE is in mobility.

[0090] The session management unit 527 manages the PDU session established between the UE and the UPF. The session management unit 527 includes the PDU session control unit 527-1 and the UE IP address assignment unit 527-2. The PDU session control unit 527-1 manages the PDU session between the mobile terminal 202 and the 5GC unit 214. The UE IP address assignment unit 527-2 assigns an IP address to the mobile terminal 202.

[0091] The control plane control unit 525 includes the NAS security unit 525-1 and the idle state mobility management unit 525-2, and performs all processing for the control plane (hereinafter sometimes referred to as C-Plane). The NAS security unit 525-1 performs security for NAS (Non-Access Stratum) messages, etc. The idle state mobility management unit 525-2 performs mobility management in the standby state (also referred to as RRC_IDLE state or simply idle), generation and control of paging signals in the standby state, addition, deletion, updating, searching, and tracking area management for one or more mobile terminals 202 under its umbrella.

[0092] The series of processes in the 5GC unit 214 are controlled by the control unit 526. Therefore, although the control unit 526 is omitted in Figure 6, it is connected to each of the units 521 to 523, 525, and 527. Each of the units in the 5GC unit 214 is implemented by a processing circuit consisting of, for example, a processor and memory, or by a dedicated processing circuit such as an FPGA, ASIC, or DSP, similar to the control unit 310 of the mobile terminal 202 described above.

[0093] Next, an example of a cell search method in a communication system is shown. Figure 7 is a flowchart illustrating the process from cell search to standby operation performed by a communication terminal (UE) in an NR-type communication system. When the communication terminal starts a cell search, in step ST601, it synchronizes the slot timing and frame timing using the first synchronization signal (P-SS) and the second synchronization signal (S-SS) transmitted from the surrounding base station.

[0094] P-SS and S-SS together are called the Synchronization Signal (SS). Each cell is assigned a synchronization code that corresponds one-to-one with its assigned PCI (Physical Cell Identifier). 1008 different PCI combinations are being considered. The communication terminal uses these 1008 PCI combinations to synchronize and also detects (identifies) the PCI of the synchronized cell.

[0095] The communication terminal then receives the PBCH in step ST602 for the next synchronized cell. The BCCH on the PBCH is mapped to the MIB (Master Information Block), which contains cell configuration information. Therefore, by receiving the PBCH and obtaining the BCCH, the MIB can be obtained. The information in the MIB includes, for example, the SFN (System Frame Number), scheduling information for SIB (System Information Block) 1, subcarrier spacing for SIB1 etc., and DM-RS position information.

[0096] Furthermore, the communication terminal obtains the SS block identifier from the PBCH. Part of the bit sequence of the SS block identifier is included in the MIB. The remaining bit sequence is included in the identifier used for sequence generation of the DM-RS associated with the PBCH. The communication terminal obtains the SS block identifier using the MIB included in the PBCH and the sequence of the DM-RS associated with the PBCH.

[0097] Next, in step ST603, the communication terminal measures the received power of the SS block.

[0098] Next, in step ST604, the communication terminal selects the cell with the best reception quality from among the one or more cells detected up to step ST603, for example, the cell with the highest received power, i.e., the best cell. The communication terminal also selects the beam with the best reception quality, for example, the beam with the highest received power of the SS block, i.e., the best beam. For example, the received power of the SS block for each SS block identifier is used to select the best beam.

[0099] Next, in step ST605, the communication terminal receives DL-SCH based on the scheduling information of SIB1 included in MIB and obtains SIB (System Information Block) 1 in the broadcast information BCCH. SIB1 contains information regarding access to the cell, cell configuration information, and scheduling information for other SIBs (SIBk: an integer k ≥ 2). SIB1 also contains the Tracking Area Code (TAC).

[0100] Next, in step ST606, the communication terminal compares the TAC of SIB1 received in step ST605 with the TAC portion of the Tracking Area Identity (TAI) in the Tracking Area List already held by the communication terminal. The Tracking Area List is also called the TAI list. TAI is identification information for identifying a tracking area and consists of MCC (Mobile Country Code), MNC (Mobile Network Code), and TAC (Tracking Area Code). MCC is the country code. MNC is the network code. TAC is the code number of the tracking area.

[0101] If, as a result of the comparison in step ST606, the TAC received in step ST605 is the same as a TAC included in the tracking area list, the communication terminal enters standby mode in that cell. If, after comparison, the TAC received in step ST605 is not included in the tracking area list, the communication terminal requests a change in the tracking area through that cell to the Core Network (EPC), which includes the MME, etc., in order to perform a Tracking Area Update (TAU).

[0102] The devices constituting the core network (hereinafter sometimes referred to as "core network devices") update the tracking area list based on the identification number (UE-ID, etc.) of the communication terminal sent from the communication terminal along with the TAU request signal. The core network devices transmit the updated tracking area list to the communication terminal. The communication terminal rewrites (updates) its TAC list based on the received tracking area list. After that, the communication terminal enters a waiting state in that cell.

[0103] Next, we will show examples of random access methods in communication systems. In random access, four-step random access and two-step random access are used. Furthermore, for both four-step and two-step random access, there are contention-based random access, that is, random access where timing collisions with other mobile terminals may occur, and contention-free random access.

[0104] An example of a collision-based four-step random access method is shown. In the first step, the mobile terminal transmits a random access preamble to the base station. The random access preamble may be selected by the mobile terminal from a predetermined range, or it may be individually assigned to the mobile terminal and notified by the base station.

[0105] In the second step, the base station sends a random access response to the mobile terminal. The random access response includes uplink scheduling information used in the third step, and a terminal identifier used in the uplink transmission of the third step.

[0106] In the third step, the mobile terminal transmits data uplink to the base station. The mobile terminal uses the information obtained in the second step for the uplink transmission. In the fourth step, the base station notifies the mobile terminal whether or not a collision has been resolved. If the mobile terminal is notified that there is no collision, it terminates the random access process. If the mobile terminal is notified that there is a collision, it restarts the process from the first step.

[0107] The collision-free four-step random access method differs from the collision-based four-step random access method in the following ways: Prior to the first step, the base station pre-assigns a random access preamble and uplink scheduling to the mobile terminal. Furthermore, notification of collision resolution status is unnecessary in the fourth step.

[0108] An example of a collision-based two-step random access method is shown below. In the first step, the mobile terminal sends a random access preamble and an uplink transmission to the base station. In the second step, the base station notifies the mobile terminal whether a collision occurred. If the mobile terminal is notified that there was no collision, it terminates the random access process. If the mobile terminal is notified that there was a collision, it restarts the process from the first step.

[0109] The collision-free two-step random access method differs from the collision-based two-step random access method in the following ways: Prior to the first step, the base station pre-assigns a random access preamble and uplink scheduling to the mobile terminal. In the second step, the base station transmits a random access response to the mobile terminal.

[0110] Figure 8 shows an example of a cell configuration in NR. In an NR cell, a narrow beam is formed and transmitted by changing its direction. In the example shown in Figure 8, the base station 750 uses beam 751-1 to transmit and receive data with a mobile terminal at a certain time. At other times, the base station 750 uses beam 751-2 to transmit and receive data with a mobile terminal. Similarly, the base station 750 uses one or more of beams 751-3 to 751-8 to transmit and receive data with a mobile terminal. In this way, the base station 750 configures a wide-area cell 752.

[0111] Figure 8 shows an example where the base station 750 uses eight beams, but the number of beams may be different from eight. Also, in the example shown in Figure 8, the base station 750 uses one beam simultaneously, but it may use multiple beams.

[0112] The concept of Quasi-Colocation (QCL) is used for beam identification (see Non-Patent Document 14 (3GPP TS38.214)). That is, the beam is identified by information indicating which reference signal (e.g., SS block, CSI-RS) beam it can be considered identical to. This information may include information about the aspects of the beams that can be considered identical, such as Doppler shift, Doppler shift diffusion, mean delay, mean delay diffusion, and spatial Rx parameters (see Non-Patent Document 14 (3GPP TS38.214)).

[0113] In 3GPP, Side Link (SL) is supported for D2D (Device to Device) and V2V (Vehicle to Vehicle) communication (see Non-Patent Documents 1 and 16). SL is defined by the PC5 interface.

[0114] In SL communication, in addition to broadcast, support for unicast and groupcast is being considered, and therefore support for PC5-S signaling is being explored (see Non-Patent Document 27 (3GPP TS23.287)). For example, PC5-S signaling is implemented to establish a link for SL, i.e., PC5 communication. This link is implemented at the V2X layer and is also referred to as a Layer 2 link.

[0115] Furthermore, support for RRC signaling in SL communication is being considered (see Non-Patent Document 27 (3GPP TS23.287)). RRC signaling in SL communication is also referred to as PC5 RRC signaling. For example, it has been proposed to notify UEs of their capabilities between UEs performing PC5 communication, and to notify AS layer settings for performing V2X communication using PC5 communication.

[0116] Figure 9 shows an example of a mobile terminal connection configuration in SL communication. In the example shown in Figure 9, UE805 and UE806 are located within the coverage 803 of base station 801. UL / DL communication 807 is performed between base station 801 and UE805. UL / DL communication 808 is performed between base station 801 and UE806. SL communication 810 is performed between UE805 and UE806. UE811 and UE812 are located outside the coverage 803. SL communication 814 is performed between UE805 and UE811. Additionally, SL communication 816 is performed between UE811 and UE812.

[0117] As an example of communication between a UE and a NW via a relay in SL communication, UE805, shown in Figure 9, relays communication between UE811 and base station 801.

[0118] A UE performing relay may use a configuration similar to that shown in Figure 4. The relay processing in the UE will be explained using Figure 4. The relay processing by UE 805 in communication from UE 811 to base station 801 will be explained. The radio signal from UE 811 is received by antennas 307-1 to 307-4. The received signal is converted from the radio reception frequency to a baseband signal by the frequency conversion unit 306, and demodulation processing is performed in the demodulation unit 308. Weight calculation and multiplication processing may also be performed in the demodulation unit 308. The demodulated data is passed to the decoder unit 309, where decoding processing such as error correction is performed. The decoded data is passed to the protocol processing unit 301, where protocol processing such as MAC and RLC used for communication with UE 811 is performed, for example, operations such as header removal in each protocol. Protocol processing such as RLC and MAC used for communication with base station 801 is also performed, for example, operations such as header addition in each protocol. In the protocol processing unit 301 of the UE811, PDCP and SDAP protocol processing may also be performed. The processed data is passed to the encoder unit 304, where encoding processing such as error correction is performed. There may also be data that is output directly from the protocol processing unit 301 to the modulation unit 305 without encoding processing. The data encoded by the encoder unit 304 is then modulated by the modulation unit 305. Precoding in MIMO may be performed in the modulation unit 305. The modulated data is converted into a baseband signal and then output to the frequency conversion unit 306, where it is converted to a wireless transmission frequency. After that, the transmission signal is sent from antennas 307-1 to 307-4 to the base station 801.

[0119] As described above, an example of relaying by UE805 in communication from UE811 to base station 801 was shown, but the same process is used in relaying communication from base station 801 to UE811.

[0120] 5G base stations can support Integrated Access and Backhaul (IAB) (see Non-Patent Documents 2 and 20). A base station that supports IAB (hereinafter sometimes referred to as an IAB base station) consists of an IAB donor CU, which is a CU of the base station that operates as an IAB donor providing IAB functionality; an IAB donor DU, which is a DU of the base station that operates as an IAB donor; and an IAB node that is connected to the IAB donor DU and to the UE using a wireless interface. An F1 interface is provided between the IAB node and the IAB donor CU (see Non-Patent Document 2).

[0121] Figure 10 shows an example of IAB base station connections. IAB donor CU901 is connected to IAB donor DU902. IAB node 903 is connected to IAB donor DU902 using a wireless interface. IAB node 903 is connected to IAB node 904 using a wireless interface. In other words, multi-stage connections of IAB nodes may occur. UE905 is connected to IAB node 904 using a wireless interface. UE906 may be connected to IAB node 903 using a wireless interface, and UE907 may be connected to IAB donor DU902 using a wireless interface. Multiple IAB donor DU902 may be connected to IAB donor CU901, multiple IAB node 903 may be connected to IAB donor DU902, and multiple IAB node 904 may be connected to IAB node 903.

[0122] A BAP (Backhaul Adaptation Protocol) layer is provided in the connection between IAB donor DUs and IAB nodes, and in the connection between IAB nodes (see Non-Patent Document 29). The BAP layer performs operations such as routing received data to IAB donor DUs and / or IAB nodes, and mapping to RLC channels (see Non-Patent Document 29).

[0123] As an example of the configuration of an IAB donor CU, a configuration similar to that of CU215 is used.

[0124] As an example of the IAB donor DU configuration, a configuration similar to that of DU216 is used. In the protocol processing section of the IAB donor DU, BAP layer processing is performed, such as adding a BAP header to downlink data, routing to IAB nodes, and removing the BAP header from uplink data.

[0125] As an example of an IAB node configuration, a configuration excluding the EPC communication unit 401, other base station communication unit 402, and 5GC communication unit 412 shown in Figure 5 may be used.

[0126] The transmission and reception processing at the IAB node will be explained using Figures 5 and 10. The transmission and reception processing of the IAB node 903 in communication between the IAB donor CU 901 and UE 905 will be explained. In uplink communication from UE 905 to IAB donor CU 901, the radio signal from the IAB node 904 is received by the antenna 408 (part or all of antennas 408-1 to 408-4). The received signal is converted from the radio reception frequency to a baseband signal by the frequency conversion unit 407, and demodulation processing is performed by the demodulation unit 409. The demodulated data is passed to the decoder unit 410, where decoding processing such as error correction is performed. The decoded data is passed to the protocol processing unit 403, where protocol processing such as MAC and RLC used for communication with the IAB node 904 is performed, for example, operations such as header removal in each protocol. Furthermore, routing to the IAB donor DU902 is performed using a BAP header, and protocol processing such as RLC and MAC used for communication with the IAB donor DU902 is performed, such as adding headers for each protocol. The processed data is passed to the encoder unit 405, where encoding processing such as error correction is performed. There may be data that is output directly from the protocol processing unit 403 to the modulation unit 406 without encoding processing. The encoded data is then modulated in the modulation unit 406. Precoding in MIMO may be performed in the modulation unit 406. The modulated data is converted into a baseband signal, then output to the frequency conversion unit 407, where it is converted to a wireless transmission frequency. After that, a transmission signal is sent from antennas 408-1 to 408-4 to the IAB donor DU902. Similar processing is performed in downlink communication from the IAB donor CU901 to UE905.

[0127] The same transmission and reception processing is performed at IAB node 904 as at IAB node 903. In the protocol processing unit 403 of IAB node 903, as part of the BAP layer processing, for example, the addition of a BAP header and routing to IAB node 904 in uplink communication, and the removal of a BAP header in downlink communication are performed.

[0128] Hereafter, expressions using the slash symbol ( / ) will mean that the expression includes at least one of the two elements before and after the slash.

[0129] In the 3GPP mobile communication system, support for Uncrewed Aerial Systems (UAS) has been considered. For example, 3GPP UAS supports C2 (Command and Control) communication (see Non-Patent Document 30). C2 communication is for command and control between a UAV and a UAV-C, and there are two types: communication via Uu and communication via PC5. In C2 communication via Uu, the UAV and UAV-C are each connected to a USS (UAS Service Supplier) / UTM (UAS Traffic Management), and C2 communication is performed via the USS / UTM. In C2 communication via PC5, C2 communication is performed directly between the UAV and the UAV-C. In this specification, C2 communication via PC5 may be referred to as Direct C2 Communication. C2 communication via Uu is sometimes referred to as indirect C2 communication.

[0130] 3GPP discloses separate communication establishment methods for indirect C2 communication and direct C2 communication. However, in actual operation, the following problems may arise. Figure 30 is a conceptual diagram of a UAV performing C2 communication that is moving. At a certain point in time, UAV 3001 is performing indirect C2 communication with UAV-C 3002 at location A via base stations 3011 and 3012. At the next point in time, UAV 3001 moves from location A to location B. For example, if there is an obstacle such as a mountain or building between UAV 3001 and base station 3011, the indirect C2 communication may be interrupted and C2 communication may become impossible. In another example, at a certain point in time, UAV 3001 is performing direct C2 communication with UAV-C 3002 at location B. At the next point in time, UAV 3001 moves from location B to location A. For example, if the above-mentioned obstacle exists between UAV3001 and UAV-C3002, direct C2 communication may be interrupted, making C2 communication impossible. Even in such situations, it is required that C2 communication between UAV3001 and UAV-C3002 be maintained continuously.

[0131] This embodiment discloses a method for solving these problems.

[0132] Switch between indirect C2 communication and direct C2 communication between the UAV and UAV-C. Indirect C2 communication may be switched to direct C2 communication, or direct C2 communication may be switched to indirect C2 communication. A UAV and UAV-C currently using indirect C2 communication will switch to direct C2 communication before the indirect C2 communication is interrupted. A UAV and UAV-C currently using direct C2 communication will switch to indirect C2 communication before the direct C2 communication is interrupted.

[0133] While 3GPP discloses separate communication establishment methods for indirect C2 communication and direct C2 communication, it does not disclose any method for switching between indirect and direct C2 communication. Furthermore, 3GPP discloses a path switching method for PC5 communication and Uu communication in ProSe (Proximity Service) (Non-Patent Document 33), but it does not consider UAS at all, and therefore cannot be simply applied to UAS. For this reason, a method for switching between indirect C2 communication and direct C2 communication between UAV and UAV-C in a UAS is required. This specification discloses a method for switching between indirect C2 communication and direct C2 communication in a UAS. In this specification, the switching between indirect C2 communication and direct C2 communication may be referred to as C2 communication switching.

[0134] A node that determines C2 communication switching is disclosed. A UAV may also determine C2 communication switching. For example, if a UAV measures the switching decision indicator described later, the UAV does not need to obtain the measurement results of the indicator from other nodes. Therefore, the signaling load can be reduced.

[0135] A RAN node may determine C2 communication switching. In this embodiment and other embodiments described later, a RAN node may be, for example, a base station. A base station may be a CU, a DU, or a TRP. A base station may be an MN or an SN. A RAN node may be a relay or a repeater. A RAN node may be an IAB donor, an IAB node, an IAB-DU, or an IAB-MT. Notification to the MN may be made via the SN. Notification to the SN may be made via the MN. For example, a RAN node may set measurement settings for a decision metric for C2 communication switching for a UAV and obtain measurement results from the UAV. In such a case, the RAN node does not need to obtain measurement results of the switching decision metric from other nodes. Therefore, the signaling load can be reduced.

[0136] The USS / UTM may decide on a C2 communication switchover. The USS / UTM provides UAS services and policies, and manages the operation of UAVs. For example, the USS / UTM may decide on a C2 communication switchover as part of UAV operation management.

[0137] The UAV-C may determine whether to switch to C2 communication. The UAV-C controls the UAV. For example, the UAV-C may perform C2 communication switching control.

[0138] Other network nodes may determine the C2 communication switchover. For example, a network node that measures the switchover decision indicator described later may determine the C2 communication switchover. The network node may also be a CN node. The network node may be an AMF, SMF, UPF, PCF, LMF, NWDAF (Network Data Analytics Function), or UAS NF (Uncrewed Aerial System Network Function) / NEF (Network Exposure Function). Since the network node does not need to obtain the measurement results of the switchover decision indicator from other nodes, the signaling load can be reduced.

[0139] In the following text, the aforementioned RAN nodes, CN nodes, and USS / UTM and other network elements may be collectively referred to as NW nodes. The term "network (NW)" in this specification may be interpreted as encompassing a broader network than a mobile communication network.

[0140] An indicator for determining C2 communication switching is disclosed. Hereafter, this indicator may be referred to as a switching decision indicator. The switching decision indicator may also be referred to as switching decision information, switching decision parameters, or switching decision data. The switching decision indicator may include at least one of the following (a1) to (a17). Multiple indicators may also be used in combination.

[0141] (a1) Communication quality (a2) QoS (Quality of Service) (a3) ​​QoS (Quality of Experience) (a4) PRACH information (a5) Location (a6) Area (a7) Altitude (a8) Distance (a9) Power consumption (a10) Remaining battery capacity (a11) Energy used (a12) Time (a13) Cell (a14) Beam (a15) Sensing data (a16) Number of UAVs (a17) UAV speed, acceleration, and direction of movement

[0142] The aforementioned (a1) communication quality may include, for example, the communication quality of Uu, or the communication quality of SL. The communication quality of Uu may include, for example, the communication quality of DL, or the communication quality of UL. The communication quality of Uu may include, for example, at least one of RSRP, RSRQ, and SIR (Signal to Interference power Ratio). The communication quality of SL may include, for example, at least one of SL-RSRP, SL-RSRQ, and SL's SIR. The (a1) communication quality may include information indicating which communication quality is included as a switching decision indicator. This information may indicate that at least one of the above-mentioned communication quality is included as a switching decision indicator. For example, the communication quality between the UAV and the base station (i.e., the communication quality of Uu) and the communication quality between the UAV and UAV-C (i.e., the communication quality of SL) may be used as switching decision indicators. This makes it possible to determine C2 communication with better communication quality.

[0143] The aforementioned (a2) QoS may include, for example, the QoS of Uu or the QoS of PC5. With respect to Uu, (a2) QoS may include, for example, the QoS for each QoS flow. In this configuration, (a2) QoS may include at least one of the following: a QoS flow identifier (e.g., QFI (QoS Flow Identifier)) and an identifier representing the QoS characteristics of the QoS flow (e.g., 5QI (5G QoS Identifier)). Similarly, with respect to PC5, (a2) QoS may include at least one of the following: PC5 QFI and PQI (PC5 5QI). QoS may include at least one of the following: bitrate, latency, packet loss rate, throughput, data volume, and reliability. (a2) QoS may include information indicating which QoS is included as a switching decision metric. This information may indicate that at least one of the above-mentioned QoS-related information is included as a switching decision criterion. For example, QoS between the UAV and the NW node using Uu and QoS between the UAV and the UAV-C using PC5 may be used as switching decision criteria. This makes it possible to determine C2 communication with better QoS.

[0144] The aforementioned (a3) ​​QoE may include, for example, the QoE of Uu or the QoE of PC5. The (a3) ​​QoE may include information indicating which QoE is included as a switching decision indicator. This information may indicate that at least one of the above-mentioned QoE information is included as a switching decision indicator. The (a3) ​​QoE may be a QoE where the UAV and the base station or UAV-C are connected, or a QoE where the UAV and the base station or UAV-C are not connected. For example, the QoE between the UAV and the NW node using Uu and the QoE between the UAV and the UAV-C using PC5 may be used as switching decision indicators. This makes it possible to determine C2 communication with a better QoE.

[0145] The aforementioned (a4) PRACH information may include, for example, the number of PRACH retransmissions in the Uu, or it may include PRACH resource information. The (a4) PRACH information may also include information indicating which PRACH information is included as a switching decision indicator. This information may indicate that at least one of the above-mentioned PRACH information is included as a switching decision indicator. For example, information about PRACH transmitted from the UAV to the base station may be used as a switching decision indicator. This makes it possible to determine a more suitable C2 communication for the access.

[0146] The aforementioned (a5) location may include, for example, two-dimensional location information or three-dimensional location information. The (a5) location may include, for example, location information obtained by GNSS or location information obtained by the 3GPP location information acquisition function. The (a5) location may include information indicating which location information is included as a switching decision index. This information may indicate that at least one of the above-mentioned location information is included as a switching decision index. For example, the UAV's location may be used as a switching decision index. At least one of the following may be used as a switching decision index: information indicating the relative positional relationship between the UAV and the UAV-C, information indicating the relative positional relationship between the UAV and the base station, and information indicating the relative positional relationship between the UAV and a predetermined reference position. For example, the (a5) location may be used in combination with other switching decision indexes. For example, other switching decision indexes may be selected based on the location. The values ​​of other switching decision indexes may be changed based on the location. The UAV's location enables the switching of C2 communication.

[0147] The aforementioned (a6) area may include, for example, a region, a zone, a geographical area, an exclusion zone, a No Transgression Zone (NTZ) (see Non-Patent Document 30), or a flight path (see Non-Patent Document 2). An exclusion zone is a zone outside the flight area. The (a6) area may include information indicating which area information is included as a switching decision indicator. This information may indicate that at least one of the above-mentioned areas is included as a switching decision indicator. For example, the area where the UAV is located may be used as a switching decision indicator. The area to which the UAV will reach in the future (for example, after a predetermined period) may be used as a switching decision indicator. For example, the (a6) area may be used in combination with other switching decision indicators. For example, other switching decision indicators may be selected based on the area where the UAV is located. The value of other switching decision indicators may be changed based on the area where the UAV is located. The area where the UAV is located enables a C2 communication switching decision.

[0148] The aforementioned (a7) altitude may include, for example, sea level altitude or ground level altitude. Also, (a7) altitude may include, for example, reference plane information. (a7) altitude may indicate at least one range of the altitudes described above. (a7) altitude may include information indicating which altitudes are included as switching indicators. This information may indicate that at least one of the altitude-related pieces of information described above is included as a switching indicator. For example, the altitude of the UAV may be used as a switching indicator. For example, (a7) altitude may be used in combination with other switching indicators. For example, other switching indicators may be selected based on altitude or a range of altitudes. The values ​​of other switching indicators may be changed based on altitude or a range of altitudes. The altitude of the UAV enables the switching of C2 communication.

[0149] The aforementioned (a8) distance may include, for example, two-dimensional distance information or three-dimensional distance information. The (a8) distance may also include, for example, information combining planar distance and altitude. The (a8) distance may include, for example, at least one of (b1) to (b7) disclosed below. The (a8) distance may include information indicating which distances are included as switching decision indicators. For example, the information may indicate that at least one of (b1) to (b7) is included as a switching decision indicator.

[0150] (b1) Distance between the UAV and UAV-C. (b2) Distance between UAVs. (b3) Distance between the UAV and a non-aircraft-mounted UE. (b4) Distance between the UAV and a non-aircraft-mounted UE whose location is known. (b5) Distance between the UAV and other objects. (b6) Distance between the UAV and other objects whose location is known. (b7) Distance between the UAV and a reference UAV.

[0151] A reference UAV may be provided. The reference UAV may be a UAV that supports the positioning of the target UAV. The reference UAV may be, for example, a UAV whose location is known. The aforementioned (a8) distance may include, for example, information indicating what the distance is between the UAV and. For example, this information may include information about the opposing UAV-C, the opposing UAV, the opposing UE, the reference UAV, information about a UE whose location is known, or information about another object whose location is known.

[0152] For example, distance may be used as a switching decision criterion. Alternatively, at least one range of distances from (b1) to (b7) may be used as a switching decision criterion. For example, (a8) distance may be used in combination with other switching decision criterions. For example, other switching decision criterions may be selected based on distance or a range of distances. The value of other switching decision criterions may be changed based on distance or a range of distances. The distance to the UAV enables the switching of C2 communication.

[0153] The aforementioned (a9) power consumption may include, for example, the power consumption of the UAV, the power consumption of the UE mounted on the UAV, or the power consumption of each component mounted on the UAV. The (a9) power consumption may include, for example, information indicating which power consumption is included as a switching decision indicator. This information may indicate that at least one of the power consumption-related information described above is included as a switching decision indicator. For example, power consumption may be used as a switching decision indicator. For example, a range of power consumption may be used as a switching decision indicator. For example, (a9) power consumption may be used in combination with other switching decision indicators. For example, other switching decision indicators may be selected based on power consumption or a range of power consumption. The value of other switching decision indicators may be changed based on power consumption or a range of power consumption. The power consumption of the UAV enables the switching of C2 communication.

[0154] The (a10) remaining battery capacity mentioned above may include, for example, the remaining battery capacity of the UAV, or the remaining battery capacity of the UE mounted on the UAV. The UAV may include multiple batteries. The batteries may be, for example, a battery for communication, a battery for a fan, a battery for control, or a battery for sensing. The (a10) remaining battery capacity may be, for example, the remaining battery capacity of each battery. The (a10) remaining battery capacity may include, for example, information indicating which remaining battery capacity is included as a switching decision indicator. This information may indicate that at least one of the information regarding the remaining battery capacity mentioned above is included as a switching decision indicator. For example, the remaining battery capacity may be used as a switching decision indicator. For example, the range of the remaining battery capacity may be used as a switching decision indicator. For example, the (a10) remaining battery capacity may be used in combination with other switching decision indicators. For example, other switching decision indicators may be selected based on the remaining battery capacity or the range of the remaining battery capacity. The value of other switching decision indicators may be changed based on the remaining battery capacity or the range of the remaining battery capacity. The remaining battery capacity of the UAV allows for the determination of whether to switch to C2 communication.

[0155] The switching decision indicator may include remaining flight range or remaining flight time. Along with, or instead of, remaining battery capacity, the switching decision indicator may include remaining flight range or remaining flight time. For example, remaining flight range or remaining flight time may be used as the switching decision indicator. For example, a range of remaining flight range or remaining flight time may be used as the switching decision indicator. For example, remaining flight range or remaining flight time may be used in combination with other switching decision indicators. For example, other switching decision indicators may be selected based on remaining flight range or remaining flight time, or a range of remaining flight range or remaining flight time. The value of other switching decision indicators may be changed based on remaining flight range or remaining flight time, or a range of remaining flight range or remaining flight time. The remaining flight range or remaining flight time of the UAV enables the switching decision for C2 communication.

[0156] The aforementioned (a11) power consumption may include, for example, the power consumption of the UAV, the power consumption of the UE mounted on the UAV, or the power consumption of each predetermined component. The (a10) power consumption may include, for example, information indicating which power consumption is included as a switching decision indicator. This information may indicate that at least one of the above-mentioned power consumptions is included as a switching decision indicator. For example, the power consumption may be used as a switching decision indicator. For example, the range of power consumption may be used as a switching decision indicator. For example, the (a10) power consumption may be used in combination with other switching decision indicators. For example, other switching decision indicators may be selected based on the power consumption or the range of power consumption. The value of other switching decision indicators may be changed based on the power consumption or the range of power consumption. The power consumption of the UAV enables the switching of C2 communication.

[0157] The aforementioned (a12) time may include, for example, time information used for C2 communication switching decisions. The (a12) time may include, for example, time information for performing C2 communication switching decisions, time information for obtaining switching decision indicators, information regarding the UAV's flight time, or information regarding the UE's usage time. The (a12) time may include, for example, information indicating what time information is included as a switching decision indicator. This information may indicate that at least one of the above-mentioned time information is included as a switching decision indicator. For example, time may be used as a switching decision indicator. For example, a time range (e.g., period) may be used as a switching decision indicator. For example, the (a12) time may be used in combination with other switching decision indicators. For example, other switching decision indicators may be selected based on time or a time range. The value of other switching decision indicators may be changed based on time or a time range. Time enables C2 communication switching decisions.

[0158] The aforementioned (a13) cell may include, for example, information about the serving cell of the UAV, or information about adjacent cells (which may be peripheral cells or cells capable of measuring communication quality). The (a13) cell may include, for example, information indicating which cells' information is included as a switching decision metric. This information may indicate that at least one of the above-mentioned cells is included as a switching decision metric. For example, a cell may be used as a switching decision metric. For example, the (a13) cell may be used in combination with other switching decision metrics. For example, a cell may select other switching decision metrics. A cell may change the values ​​of other switching decision metrics. The cell enables switching decisions for C2 communication.

[0159] The aforementioned (a14) beam may include, for example, information about the beam on which the UAV communicates, or it may include information about multiple beams. The (a14) beam may include at least one of the following: information about the UAV-C beam and information about the base station beam. The (a14) beam may include, for example, information indicating which beam information is included as a switching decision index. This information may indicate that at least one of the beams described above is included as a switching decision index. For example, a beam may be used as a switching decision index. For example, the (a14) beam may be used in combination with other switching decision indexes. For example, a beam may select other switching decision indexes. A beam may change the value of other switching decision indexes. The beam enables switching decisions for C2 communication.

[0160] The sensing data (a15) mentioned above may be, for example, sensing data measured by a UAV or RAN node. The sensing data may also be sensing results derived from measurement results by a node having a sensing processing function. The sensing data is not limited to sensing data measured in a 3GPP system, but may also be sensing data measured in a non-3GPP system. Sensing data measured in a non-3GPP system may be provided to a 3GPP UE or NW node.

[0161] The aforementioned (a16) number of UAVs may be, for example, the number of UAVs connected to a base station or the number of UAVs not connected to a base station, or it may be, for example, the number of UAVs present in a predetermined area or altitude range. For example, the above number of UAVs can be used to make decisions that take into account congestion and the load on the base station.

[0162] The aforementioned (a17) velocity, acceleration, and direction of motion of the UAV may include, for example, at least one of the velocity, acceleration, and direction of motion when the UAV is moving. If the UAV is not moving, the velocity information, acceleration information, and direction of motion information may each be set to 0.

[0163] A method for obtaining a switching decision index is disclosed. The switching decision index may be obtained by measurement. The measurement may include not only the measurement of the index but also the derivation of the index using the measurement results. Hereafter, a node that measures the switching decision index may be referred to as an index measurement node. An index measurement node may be, for example, a UAV, a RAN node, a CN node, or a UAV-C. For example, a UAV may measure communication quality. A RAN node may obtain communication quality from a UAV. For example, a UAV, a RAN node, or a CN node (e.g., UPF) may measure QoS. A USS / UTM may obtain QoS from the index measurement node. For example, a UAV or UAV-C may measure QoE. A USS / UTM may obtain QoE from the index measurement node. For example, a UAV, a RAN node, an AMF, an LMF, or a GMLC may perform UAV positioning. USS / UTM may obtain UAV location information from the index measurement node.

[0164] A method for measuring switching decision indicators is disclosed. Settings for measuring switching decision indicators may be provided. Hereafter, these settings may be referred to as indicator measurement settings. An indicator measurement setting may include, for example, at least one of the following: measurement target, measurement method, and method for notifying measurement results. For example, the measurement target for Uu communication quality may include at least one of SSB, RS, and CSI-RS. For example, the measurement target for SL communication quality may include at least one of RS, CSI-RS, and SL SSB. For example, the measurement target for QoS may be C2 communication packet data. For example, the measurement target for position and distance may include at least one of PRS and SL PRS. For example, the measurement target for current consumption and power consumption may include at least one of the following: current flowing from the battery and the time during which the current is flowing. For example, the measurement target for remaining battery capacity may include at least one of the following: battery voltage, current flowing from the battery, and the time during which the current is flowing. Furthermore, conventional measurement targets may be applied to each indicator as appropriate.

[0165] The measurement method may include, for example, at least one of periodic measurements, non-periodic measurements, and measurements when certain conditions are met. Non-periodic measurements may include, for example, measurements taken when a measurement instruction or request is received. The certain conditions may include, for example, at least one of a predetermined time, a predetermined location, a predetermined altitude, a predetermined area, a predetermined cell, a predetermined beam, and a predetermined connection state.

[0166] The method of notifying (or reporting) the measurement results may include, for example, at least one of periodic notifications, aperiodic notifications, and notifications when a predetermined condition is met. Aperiodic notifications may be, for example, notifications when a notification instruction or notification request is received. The predetermined condition may be, for example, an event trigger. It is desirable that an event be set.

[0167] Hereafter, the node that sets the measurement of the switching decision index may be referred to as the first setting node to distinguish it from other nodes. The first setting node transmits the index measurement settings to the index measurement node. The first setting node may transmit the index measurement settings to the index measurement node via other nodes. The first setting node may transmit some or all of the index measurement settings. For example, the first setting node may be, for example, a RAN node, PCF, LMF, UAS NF / NEF, or USS / UTM. For example, a base station may transmit the index measurement settings to a UAV. For example, a PCF may transmit the index measurement settings to an AMF, SMF, UPF, RAN node, and UAV. For example, an LMF may transmit the index measurement settings to an AMF, RAN node, and UAV. For example, a USS / UTM may transmit the index measurement settings to a UAS NF / NEF.

[0168] An indicator measurement node that receives an indicator measurement setting should use that setting to measure the switching decision indicator.

[0169] The indicator measurement node transmits the measurement results to the node that determines C2 communication switching. Hereafter, the node that determines C2 communication switching may be referred to as the switching decision node. The switching decision node may be a UAV, UAV-C, RAN node, CN node, or USS / UTM. The conditions for determining C2 communication switching may also be referred to as switching conditions or switching policies. The setting of the conditions for determining C2 communication may be referred to as switching condition settings. Switching condition settings may include policies, parameters, or information used for C2 communication switching.

[0170] The indicator measurement node may transmit the measurement results to the switching decision node via other nodes. The indicator measurement node may transmit the measurement results using the indicator measurement settings. A CP may be used to transmit the measurement results. For example, signaling may be used. This makes it possible to transmit the measurement results without establishing UP communication. This makes it possible to transmit the measurement results early. Alternatively, a UP may be used to transmit the measurement results. For example, a PDU session may be used to transmit the measurement results. This makes it possible to transmit the measurement results along with the data. It becomes possible to set the desired QoS (i.e., QoS flow) for transmitting the measurement results. The PDU session may be, for example, a PDU session for C2 communication.

[0171] CP may be used not only for transmitting measurement results, but also for communication between the UAV or UAV-C and the NW node, such as setting indicator measurement settings and switching conditions, or UP may be used. Similar effects can be obtained.

[0172] A node that receives measurement results may record them. For example, a switching decision node may record the measurement results. A node that receives new measurement results may update the measurement results. For example, a switching decision node may update the measurement results. Updating with newer data enables a more appropriate decision for switching to C2 communication.

[0173] Specific examples of the event triggers disclosed above are now disclosed. An event trigger based on the communication quality of PC5 may be provided. For example, an event trigger based on the communication quality between the UAV and UAV-C may be provided. For example, an event may be provided when the communication quality between the UAV and UAV-C is less than a predetermined value (it may be less than or equal to a predetermined value). For example, an event may be provided when the communication quality between the UAV and UAV-C is greater than a predetermined value (it may be greater than or equal to a predetermined value).

[0174] An event trigger may be provided that combines the communication quality of PC5 and the communication quality of Uu. For example, an event trigger may be provided based on the communication quality between the UAV and UAV-C, and the communication quality between the UAV and the RAN node. For example, an event may be provided when the communication quality between the UAV and UAV-C falls below a predetermined value, and the communication quality between the UAV and the base station falls above a predetermined value. An event may be provided when the communication quality between the UAV and UAV-C falls above a predetermined value, and the communication quality between the UAV and the base station falls below a predetermined value.

[0175] For example, an event may be set up in which the communication quality between the UAV and UAV-C is greater than the communication quality between the UAV and the base station. For example, an event may be set up in which the communication quality between the UAV and UAV-C is less than the communication quality between the UAV and the base station.

[0176] For example, an event trigger may be provided that combines communication quality and altitude. An event may be provided when the communication quality between the UAV and UAV-C falls below a predetermined value and the altitude of the UAV is greater than a predetermined value. For example, an event may be provided when the communication quality between the UAV and UAV-C falls below a predetermined value, the communication quality between the UAV and the base station is greater than a predetermined value, and the altitude of the UAV is greater than a predetermined value.

[0177] For example, an offset may be applied. A value obtained by adding an offset to the measured value or a predetermined value may be used, or a value obtained by subtracting the offset from the measured value or a predetermined value may be used.

[0178] The aforementioned base station may be a serving cell, an adjacent cell, or a candidate cell. This allows for flexible configuration of the indicator measurement settings.

[0179] Altitude may be combined with the indicator measurement settings. For example, the indicator measurement settings may include restrictions based on altitude or altitude range. For example, the indicator measurement settings may be changed depending on altitude or altitude range. For example, indicator measurement settings may be provided for multiple altitudes or multiple altitude ranges. For example, the measurement target of the switching decision indicator may be changed, the measurement method may be changed, or the notification method of the measurement results may be changed depending on altitude or altitude range. For example, an event trigger may be set using multiple altitudes or multiple altitude ranges. By combining the indicator measurement settings with altitude in this way, it becomes possible to make more flexible and appropriate C2 communication switching decisions based on the altitude of the UAV.

[0180] This document discloses a method for obtaining location information disclosed as a switching decision indicator. The LMF or GMLC obtains location information of the UAV using the 3GPP positioning function (see Non-Patent Documents 24 and 25). A node requesting the setting of switching conditions may obtain location information of the UAV from the LMF or GMLC. For example, a switching decision node may obtain location information of the UAV from the LMF or GMLC. A node requesting the setting of switching conditions or a switching decision node may obtain location information of the UAV from the LMF or GMLC via the USS / UTM. In this way, the location of the UAV can be obtained by using the positioning function.

[0181] Information regarding the location of the UAV-C may be obtained. The method for obtaining the location information of the UAV disclosed above may be applied as appropriate. The USS / UTM may track the UAV-C. The USS / UTM may track the UAV-C using the location information of the UAV-C. In this way, the USS / UTM can obtain information regarding the location of the UAV-C.

[0182] For determining whether to switch C2 communication, data collected by the data collection method disclosed in Embodiment 6, described later, may be used. For example, a switching decision node or a node requesting the setting of switching conditions may obtain the above data from a node that possesses it. The switching decision node or the node requesting the setting of switching conditions may request the node possessing the above data to provide the data. The node provides the requested data to the requesting node. In this way, for example, data collected using the MDT function can be used to determine whether to switch C2 communication.

[0183] This document discloses a method for obtaining distance information disclosed as a switching decision indicator. The distance between the UAV and UAV-C is derived using SL. For example, the UAV and / or UAV-C derive the RTT (Round Trip Time) between the UAV and UAV-C using SL-PRS. A node requesting switching condition setting may obtain information regarding the distance between the UAV and UAV-C from the UAV or UAV-C. For example, a switching decision node may obtain information regarding the distance between the UAV and UAV-C from the UAV or UAV-C. In this way, distance measurement between the UAV and UAV-C can be performed without going through a network node, and distance information can be obtained at an early stage.

[0184] A node requesting the setting of switching conditions or a switching decision node may obtain information regarding the UAV's position from the LMF or GMLC. Alternatively, the LMF or GMLC may position the UAV and the UAV-C and derive the distance between the UAV and the UAV-C from their positions. The method for positioning the UAV and the UAV-C may appropriately apply, for example, the positioning functions of 3GPP (see Non-Patent Documents 24 and 25).

[0185] Information regarding the parameters and / or policies required for position measurement processing (which may include position derivation processing) and / or distance measurement processing (which may include distance derivation processing) may be provided to the UAV and UAV-C in advance. Details of the position measurement processing, position derivation processing, distance measurement processing and distance derivation processing will be described later. For example, the above-mentioned information regarding parameters and / or policies may be provided from the NW node for the position measurement processing and / or distance measurement processing. Alternatively, the above-mentioned information regarding parameters and policies may be provided, for example, during the authorization processing for C2 communication. For example, the above-mentioned information regarding parameters and / or policies may be provided when establishing or modifying a PDU session for C2 communication. For example, providing it in the processing for C2 communication when C2 communication is required makes the provision process of the parameters and / or policies easier.

[0186] A node requesting the setting of switching conditions may obtain information regarding the distance between the UAV and the UAV-C from the LMF or GMLC. For example, a switching decision node may obtain information regarding the distance between the UAV and the UAV-C from the LMF or GMLC. A node requesting the setting of switching conditions or a switching decision node may obtain information regarding the distance between the UAV and the UAV-C from the LMF or GMLC via the USS / UTM. In this way, the distance between the UAV and the UAV-C can be obtained by using the positioning function.

[0187] The USS / UTM may derive the distance between the UAV and UAV-C. The USS / UTM requests information about the locations of the UAV and UAV-C from the LMF or GMLC. The LMF or GMLC transmits information about the locations of the UAV and UAV-C to the USS / UTM. The USS / UTM may use this location information to derive the distance between the UAV and UAV-C. A node requesting switching condition settings or a switching decision node may obtain information about the distance between the UAV and UAV-C from the USS / UTM. In this way, the USS / UTM can handle information about the UAV and UAV-C performing C2 communication and the distance between them together.

[0188] The USS / UTM may record pairing information for C2 communication between the UAV and UAV-C, and information regarding the distance between the UAV and UAV-C, in association with each other. This allows for easy handling of information regarding the UAV and UAV-C performing C2 communication, and the distance between them.

[0189] The switching decision node uses the acquired switching decision index to make a decision on C2 communication switching. As described above, switching conditions may be set for deciding on C2 communication switching. For example, a predetermined value, such as a threshold, may be set as a switching condition for deciding on C2 communication switching based on the switching decision index. For example, if the switching decision index falls below a predetermined value, the switching decision node decides on C2 communication switching. C2 communication switching may be switching from direct C2 communication to indirect C2 communication, or switching from indirect C2 communication to direct C2 communication. The switching conditions for switching from direct C2 communication to indirect C2 communication and the switching conditions for switching from indirect C2 communication to direct C2 communication may be the same or different. As switching conditions, the event triggers of the index measurement settings disclosed above may be applied as appropriate. Switching conditions may be set using one or more switching decision indexes. One or more switching conditions may be set for deciding on C2 communication switching. These switching conditions may be set for each service. In this way, flexible C2 communication switching suitable for the surrounding environment and circumstances of C2 communication can be performed.

[0190] Switching conditions may include priority information. Switching condition settings may include setting switching conditions associated with priority information. Priority information may be, for example, priority levels. Priority information may be, for example, information indicating whether to prioritize direct C2 communication or indirect C2 communication. For example, priority information may be information indicating that direct C2 communication is prioritized, or information indicating that indirect C2 communication is prioritized. Priority information may include information about which C2 communication to prioritize. Priority information may be, for example, information indicating which cell to prioritize switching to in indirect C2 communication. Priority information may be, for example, information indicating which beam to prioritize switching to in indirect C2 communication. Priority information may be set in combination with switching judgment indicators. For example, priority levels may be changed depending on altitude or altitude range. For example, priority levels may be changed depending on remaining battery capacity or range of remaining battery capacity. In this way, it becomes possible to control the switching of C2 communication to suit the surrounding environment and surrounding conditions in which C2 communication is performed.

[0191] The node that sets the switching conditions may be called the second setting node to distinguish it from the first setting node. The second setting node may be a USS / UTM, a UAS NF / NEF, a RAN node, a CN node, a UAV-C, a MnS (Management Service), or any other node. The second setting node transmits the switching condition settings to the switching decision node. The second setting node may transmit the switching condition settings to the switching decision node via other nodes. The switching condition settings may be transmitted, for example, during C2 authorization processing. For example, when a base station transmits switching condition settings to a UAV, the base station may transmit the switching condition settings using RRC signaling. This allows for the transmission of more configuration information. Alternatively, MAC signaling may be used. This allows for the transmission of configuration information earlier. Alternatively, L1 / L2 signaling may be used. This allows for the transmission of configuration information even earlier.

[0192] Upon receiving the switching condition settings, the switching decision node uses these settings to initiate a decision on switching to C2 communication.

[0193] A release of the switching condition settings may be performed. Information regarding the release of the switching condition settings may be provided. The second setting node transmits information regarding the release of the switching condition settings to the switching decision node. The switching decision node may release one or more of the configured switching condition settings. The information regarding the release of the switching condition settings may include information about the settings to be released. Upon receiving the release information, the switching decision node releases the switching condition settings corresponding to the information. If the switching decision node receives information indicating the release of all switching condition settings, it may terminate its decision on C2 communication switching.

[0194] The C2 communication switching decision may be activated and deactivated. The C2 communication switching decision may be activated or deactivated for one or more switching condition settings. The C2 communication switching decision may be activated or deactivated for each switching condition setting. The second setting node transmits information to the switching decision node indicating the activation or deactivation of the C2 communication switching decision. This information may include information regarding the setting to be activated or deactivated. The switching decision node uses the received activation or deactivation information to activate or deactivate the C2 communication switching decision.

[0195] The switching decision node may choose not to make a C2 communication switching decision simply by receiving a switching condition setting. The switching decision node may start a C2 communication switching decision upon receiving information indicating the start of execution of the C2 communication switching decision. The switching decision node may choose not to release the switching condition setting simply by receiving information indicating the stop of execution of the C2 communication switching decision. The switching decision node may release the switching condition setting upon receiving information indicating the release of the switching condition setting. In this way, for example, it becomes possible to notify the switching decision node of the switching condition setting in advance, and the switching decision node can use this setting to dynamically start or stop execution of the C2 communication switching decision depending on the situation.

[0196] A request for setting switching conditions may be provided. Hereafter, this request may be referred to as a condition setting request. The switching decision node may send a condition setting request to a second setting node. The switching decision node may be a node capable of determining C2 communication switching. A node other than the switching decision node may send a condition setting request to the second setting node. The sending of a condition setting request may occur during C2 authorization processing. The second setting node that receives the condition setting request may decide on the switching condition setting. The second setting node may send the switching condition setting to the switching decision node or the node that sent the condition setting request. In this way, for example, the switching decision node can decide to perform a C2 communication switching decision and request the switching condition setting.

[0197] A request for updating the switching condition settings may be provided. Hereafter, such request may be referred to as a condition update request. The method for setting conditions as disclosed above may be applied to the condition update request as appropriate. A condition update request may include information indicating which switching condition setting is to be updated, or it may include information about the desired switching condition setting. A condition update request may include at least one of these pieces of information. For example, if the switching condition settings are no longer suitable for the flight conditions of the UAV, the switching decision node can change to a more suitable setting by sending a condition update request.

[0198] The switching decision node may determine whether to switch to C2 communication using the configured switching conditions. The switching condition settings may be applied not only for switching to C2 communication, but also to determine whether to perform direct C2 communication or indirect C2 communication first.

[0199] A C2 communication switching request may be provided. Hereafter, this request may simply be referred to as a switching request. The switching decision node sends a switching request to the UAV. The switching decision node may send the switching request via the USS / UTM or UAV-C. The UAV that receives the switching request performs the switching between indirect C2 communication and direct C2 communication. The switching decision node may send a switching request to the UAV-C. The switching decision node may send a switching request via the USS / UTM or UAV. The UAV-C that receives the switching request performs the switching between indirect C2 communication and direct C2 communication. The switching decision node may send a switching request to the USS / UTM. The UAV or UAV-C may send a switching request. The USS / UTM that receives the switching request performs the switching between indirect C2 communication and direct C2 communication. The node that actually performs the C2 communication switching can perform the C2 communication switching.

[0200] A switching response may be provided for C2 communication. Hereafter, this response may simply be referred to as a switching response. A node that receives a switching request may send a switching response to the source of the request. The source node of the request will then be able to recognize that the destination node has received the switching request. This reduces malfunctions in the C2 communication switching process.

[0201] A rejection process for switching requests may be provided. A node that receives a switching request may send information indicating the rejection to the sender of the switching request if it rejects the request. The node that made the switching request and receives information indicating the rejection will not perform the switching. For example, a node that receives a switching request may include information indicating the rejection in its switching response. For example, a UAV-C that receives a switching request from indirect C2 communication to direct C2 communication may include information indicating the rejection in its switching response if its own communication load is high and direct C2 communication with the UAV is difficult. For example, a base station that receives a switching request from direct C2 communication to indirect C2 communication may include information indicating the rejection in its switching response if its own communication load is high and indirect C2 communication with the UAV is difficult.

[0202] The information indicating rejection may include information about the cause, such as high communication load. The information indicating rejection may also include information about the expected processing after the rejection. This information may include, for example, information for requesting a change in the indirect C2 communication cell. By doing so, flexible C2 communication switching processing becomes possible, enabling C2 communication using a more appropriate node.

[0203] The switchover request may include information indicating whether or not it can be rejected. The node receiving the switchover request can determine whether or not it can be rejected. Rejectable switchover requests and non-rejectable switchover requests may be sent in separate messages. For example, rejectable switchover requests may be sent as switchover requests, and non-rejectable switchover requests as switchover instructions. The node receiving the switchover request or switchover instruction can distinguish whether or not it can be rejected.

[0204] A notification of completion of C2 communication switching may be provided. Hereafter, this notification may be referred to as a switching completion notification. A node that receives a switching request may send a switching completion notification to the sender of the request. The switching completion notification may be sent when the C2 communication switching is completed. The node that sent the switching request will be able to recognize that the destination node of the request has completed the C2 communication switching. This reduces malfunctions in the C2 communication switching process. The C2 communication switching completion notification and the switching response may be sent using the same message. For example, the switching response may be used as the switching completion notification. This makes it easier to control the C2 communication switching process.

[0205] A notification regarding C2 communication switching may be provided. Hereafter, this notification may be referred to as a switching notification. The switching notification may include at least one of the following: information about the UAS service (for example, information indicating the C2 communication service), information indicating whether the C2 communication was switched to direct or indirect, information indicating whether the switch was made from direct or indirect C2 communication, information about the UAV whose C2 communication was switched, information about the UAV-C controlling the UAV, pairing information, information indicating which cell was used for indirect C2 communication before the switch, information indicating which cell will be used for indirect C2 communication after the switch, switching condition settings, and measurement results of the switching decision index at the time of C2 communication switching. A switching decision node, a node that receives a switching response, or a node that receives a switching completion notification may send the above switching notification to other nodes. Other nodes will then be able to recognize that the C2 communication switching is complete. For example, other nodes will be able to perform post-C2 communication switching processing.

[0206] A PC5 L2 link may be established between the UAV and the UAV-C. After establishing the PC5 L2 link between the UAV and the UAV-C, the UAV and the UAV-C may communicate directly in C2 mode. After establishing the PC5 L2 link between the UAV and the UAV-C, the UAV and the UAV-C may also establish a PC5 RRC connection. The UAV and the UAV-C may also communicate directly in C2 mode using the PC5 RRC connection between the UAV and the UAV-C. This makes direct C2 communication possible.

[0207] After performing a C2 communication switchover, the C2 communication from before the switchover may be released. A request for releasing the C2 communication may be provided. Hereafter, this request may be referred to as a release request. A switchover completion notification or switchover notification may include a release request. A node that receives the request may initiate the release of the C2 communication from before the switchover. The release of direct C2 communication may be the release of the PC5 L2 link. The release of indirect C2 communication may be the release of the PDU session, the release of the CM connection, or the release of the RRC connection. In this way, unnecessary connections can be released. The release process of the C2 communication from before the switchover may be initiated after the C2 communication data from before the switchover has been delivered to the UAV or UAV-C. Data loss can be avoided.

[0208] Figure 11 shows an example sequence of C2 communication switching processing from indirect C2 communication to direct C2 communication for C2 communication between a UAV and a UAV-C. In the example in Figure 11, the UAV is the switching decision node and decides whether to switch C2 communication. ST1101, the UAV-C performs PDU session establishment processing for C2 communication between nodes such as base stations, AMF, SMF, UPF, and PCF. During the PDU session establishment processing, the UAV-C may also perform C2 authorization processing for C2 communication with nodes such as USS / UTM and UAS NF / NEF in addition to the above nodes. The UAV-C may not establish a PDU session via a base station and may perform C2 authorization processing for C2 communication with USS / UTM by other means without using a 3GPP network. The base station connected to the UAV and the base station connected to the UAV-C may be different.

[0209] In ST1103, the UAV decides to perform indirect C2 communication. In ST1105, the UAV performs PDU session establishment processing for indirect C2 communication. During the PDU session establishment processing, the UAV may also perform C2 authorization processing for indirect C2 communication. Alternatively, the NW node may perform PDU session establishment processing with the UAV. For example, after UAV-C establishes a PDU session for indirect C2 communication, the USS / UTM requests the NW node to establish a PDU session for indirect C2 communication with the UAV. The NW node that receives this request may establish a PDU session with the UAV. A PDU session for indirect C2 communication with the UAV can be established depending on the status of the USS / UTM or the NW node. In ST1107, the UAV communicates C2 data with the USS / UTM via the base station. The USS / UTM communicates C2 data with UAV-C. The UAV and USS / UTM may communicate bidirectionally. The UAV-C and USS / UTM may communicate bidirectionally. In ST1109, the UAV measures the communication quality of the Uu. The indicator measurement settings may be notified to the UAV from, for example, the base station. In the example in Figure 11, communication quality is set as the switching decision indicator. The UAV measures the communication quality using the received indicator measurement settings. For example, the UAV may measure the communication quality periodically. In ST1111, the UAV decides to send a condition setting request for switching to direct C2 communication. For example, the UAV may use an event trigger for this decision. For example, if the communication quality of the serving cell falls below a predetermined value, the UAV may send a condition setting request for switching to direct C2 communication. Event settings such as predetermined values ​​may be included in the indicator measurement settings.

[0210] In ST1113, the UAV performs PDU session modification processing for direct C2 communication and performs C2 authorization processing for direct C2 communication at the same time. In the C2 authorization processing for direct C2 communication, the UAV may send a condition setting request to the USS / UTM. The USS / UTM may notify the UAV of the switching condition setting. The switching condition setting may include, for example, the C2 communication switching condition setting or switching policy or parameters or information used for C2 communication switching as described above. The switching condition setting may also include the priority information described above. In the example in Figure 11, the switching condition setting may be a setting for determining a switch from indirect C2 communication to direct C2 communication. The UAV may use the acquired switching condition setting to determine the switching of C2 communication. In the C2 authorization processing for direct C2 communication, the USS / UTM may provide the UAV with information about the UAV, pairing information, and application information for direct C2 communication. The pairing information may also be information related to the UAV-C performing C2 communication.

[0211] The USS / UTM may notify a base station of a request for indicator measurement settings. Hereafter, this request may be referred to as the first measurement setting request. Upon receiving the first measurement setting request, the base station performs the indicator measurement settings. The USS / UTM may notify a base station of a condition setting request. Upon receiving the condition setting request, the base station performs the switching condition settings.

[0212] Some or all of the processing related to the C2 communication switching of ST1113 may be performed separately from the C2 authorization processing for C2 communication. In the example in Figure 11, these processes are performed in the C2 authorization processing for C2 communication.

[0213] In ST1115, the base station notifies the UAV of the indicator measurement settings. The base station may also notify the UAV of the switching condition settings. The base station may also notify the USS / UTM of the switching condition settings. The USS / UTM may also notify the UAV of the switching condition settings. Upon receiving the switching condition settings, the UAV can determine whether to switch to C2 communication using the indicator measurement settings and the switching condition settings.

[0214] In the example in Figure 11, the switching decision metric is communication quality, so the measurement setting request was notified to the base station. However, the measurement setting request may also be notified to other nodes based on the switching decision metric. Similarly, the condition setting request may also be notified to other nodes based on the switching decision metric. Also, in the example in Figure 11, the switching decision metric is communication quality, so the metric measurement setting was notified to the UAV. However, the metric measurement setting may also be notified to other nodes based on the switching decision metric. Similarly, the switching condition setting may also be notified to other nodes based on the switching decision metric.

[0215] In ST1117, UAV-C determines the destination Layer-2 ID (default) corresponding to the application information. In ST1119, UAV sets the application information to the destination Layer-2 ID. In ST1120 to ST1122, UAV performs PC5 L2 link establishment processing with UAV-C. UAV may use the information obtained in the C2 authorization processing for direct C2 communication for this link establishment processing. In ST1120, UAV sends a Direct Communication Request to UAV-C. UAV-C receives the Direct Communication Request sent from UAV. In ST1121, security establishment processing is performed between UAV and UAV-C. In ST1122, UAV-C sends a Direct Communication Accept to UAV. In this way, a PC5 L2 link is established between UAV and UAV-C.

[0216] After establishing a PC5 L2 link between the UAV and UAV-C, RRC connection processing may be performed between the UAV and UAV-C. This enables communication using RRC in SL.

[0217] In ST1125, the UAV measures the communication quality of Uu. In ST1127, the UAV measures the communication quality of PC5. The UAV may measure the communication quality of Uu and PC5 using an index measurement setting. The communication quality of Uu may be, for example, the communication quality of the UAV's serving cell. The communication quality of PC5 may be the communication quality of UAV-C. The communication quality may be, for example, RSRP.

[0218] In ST1129, the UAV determines whether to switch to C2 communication. The UAV may determine whether to switch to C2 communication using switching condition settings. If the switching condition is met, the UAV starts the C2 communication switching process. For example, the switching condition may be that the communication quality of Uu is less than a predetermined value and the communication quality of PC5 is greater than a predetermined value. The UAV may start the C2 communication switching process when the measured communication quality of Uu and the communication quality of PC5 meet this condition.

[0219] In ST1131, the UAV notifies UAV-C of a switching request indicating a switch from indirect C2 communication to direct C2 communication. In ST1133, UAV-C, having received the switching request, notifies the UAV of a switching response. In ST1135, the UAV and UAV-C switch from indirect C2 communication to direct C2 communication. In ST1139, C2 data is communicated between the UAV and UAV-C.

[0220] In ST1141, the UAV sends a switching notification to the USS / UTM indicating that it has switched from indirect C2 communication to direct C2 communication. The UAV may also notify the USS / UTM of a release request. This release request is a request to release the indirect C2 communication. The USS / UTM can recognize that the C2 communication between the UAV and the UAV-C has been switched to direct C2 communication. In ST1143, the USS / UTM performs the release process for the PDU session for C2 communication with the UAV.

[0221] The UAV may initiate the release process. The UAV initiates the release process for the PDU session used for communication with the USS / UTM. This allows the release process to be initiated earlier.

[0222] A USS / UTM that receives a switching request from a UAV indicating a switch from indirect C2 communication to direct C2 communication may transmit information indicating the switch from indirect C2 communication to direct C2 communication to a base station or other NW node. Alternatively, the UAV may transmit information indicating the switch from indirect C2 communication to direct C2 communication to a base station or other NW node. This information may include at least one of the following: information about the UAV and information about the CAV-C performing direct C2 communication. A switching request indicating a switch from indirect C2 communication to direct C2 communication may be used to transmit this information. The base station and other NW nodes can recognize the switch from indirect C2 communication to direct C2 communication.

[0223] By doing this, the C2 communication between the UAV and the UAV-C is switched from indirect C2 communication to direct C2 communication.

[0224] Figure 12 shows another example sequence of the C2 communication switching process from indirect C2 communication to direct C2 communication for C2 communication between the UAV and UAV-C. Steps common to Figure 11 are given the same step numbers, and common explanations are omitted. The UAV may perform a C2 authorization process that integrates the C2 authorization process for indirect C2 communication and the C2 authorization process for direct C2 communication in advance. Figure 12 discloses an example sequence of such a C2 authorization process. In ST1203, the UAV decides to perform either indirect C2 communication or direct C2 communication, or both. In ST1205, the UAV performs a combined C2 authorization process that includes the C2 authorization process for indirect C2 communication and the C2 authorization process for direct C2 communication. The USS / UTM sends both the settings for indirect C2 communication and the settings for direct C2 communication to the UAV via the NW node. The UAV obtains the settings for indirect C2 communication and the settings for direct C2 communication. The UAV can perform either indirect C2 communication or direct C2 communication, or both. In the C2 authorization process for C2 communication, the USS / UTM may provide the UAV with information about the UAV, pairing information, and application information for direct C2 communication. The pairing information may also be information about the UAV-C performing the C2 communication.

[0225] In ST1205, the UAV may request the USS / UTM to set conditions. The USS / UTM may notify the UAV of the switching conditions. The switching conditions may be the same as in the example in Figure 11. The switching conditions may include, for example, switching conditions, switching policies, or parameters or information used for C2 communication switching. In the example in Figure 12, the switching conditions may include settings for determining a switch from indirect C2 communication to direct C2 communication, and settings for determining a switch from direct C2 communication to indirect C2 communication. The UAV may use the acquired switching conditions to determine whether to switch C2 communication.

[0226] In ST1205, the USS / UTM may notify the UAV of the C2 communication to be prioritized. This information may be transmitted from the USS / UTM during the C2 authorization process. This information may also be transmitted as part of the switching condition setting. The UAV can then determine whether to prioritize indirect C2 communication or direct C2 communication. In the example in Figure 12, the UAV prioritizes indirect C2 communication.

[0227] The USS / UTM may notify the base station of a first measurement setting request. The first measurement setting request may indicate a request for indicator measurement settings for switching from indirect C2 communication to direct C2 communication, and for switching from direct C2 communication to indirect C2 communication. Upon receiving the first measurement setting request, the base station transmits the above indicator measurement settings to the UAV. The USS / UTM may notify the base station of a condition setting request. The condition setting request may include a request for switching conditions from indirect C2 communication to direct C2 communication, and a request for switching conditions from direct C2 communication to indirect C2 communication. Upon receiving the condition setting request, the base station sets the switching conditions.

[0228] Some or all of the processing related to the C2 communication switching of ST1205 may be performed separately from the C2 authorization processing for C2 communication. In the example in Figure 12, these processes are performed in the C2 authorization processing for C2 communication.

[0229] In ST1115, the base station notifies the UAV of the indicator measurement settings. The base station may also notify the UAV of the switching condition settings. These settings may include settings for switching from indirect C2 communication to direct C2 communication and settings for switching from direct C2 communication to indirect C2 communication. The base station may also notify the USS / UTM of the switching condition settings. The USS / UTM may notify the UAV of the switching condition settings. Upon receiving the switching condition settings, the UAV can determine whether to switch to C2 communication using the indicator measurement settings and the switching condition settings. In this way, the UAV can obtain settings for switching from indirect C2 communication to direct C2 communication and settings for switching from direct C2 communication to indirect C2 communication.

[0230] In ST1207, the UAV and UAV-C perform discovery processing to establish a PC5 L2 link connection. In the discovery processing, the UAV-C should use the destination set using application information in ST1117, and the UAV should use the destination set using application information in ST1119. By performing the discovery processing, in ST1127, the UAV can measure the communication quality of PC5 with the UAV-C. In ST1129, the UAV can determine whether to switch to C2 communication using the PC5 communication quality with the UAV-C.

[0231] After the switching conditions are met, in ST1120, the UAV sends a switching request to UAV-C. Upon receiving the switching request, UAV-C sends a switching response to the UAV in ST1122. These processes may also be performed in the PC5 L2 link establishment process from ST1120 to ST1122. For example, in ST1120, the UAV may send a direct communication request including a switching request to UAV-C. In ST1122, UAV-C may send a direct communication response including a switching response to the UAV. In ST1135, the UAV and UAV-C perform the C2 communication switching process.

[0232] In this way, the C2 communication between the UAV and UAV-C is switched from indirect C2 communication to direct C2 communication. ST1205 pre-performs C2 authorization processing for both indirect and direct C2 communication, and notifies the UAV of settings for determining whether to switch from indirect to direct C2 communication and settings for determining whether to switch from direct to indirect C2 communication. This enables early C2 communication switching.

[0233] Figure 13 shows an example sequence of C2 communication switching processing from direct C2 communication to indirect C2 communication between a UAV and a UAV-C. Steps common to Figure 11 are given the same step numbers, and common explanations are omitted. In ST1303, the UAV decides to perform direct C2 communication. In ST1305, the UAV performs PDU session establishment processing for C2 communication. During PDU session establishment processing, the UAV may also perform C2 authorization processing for direct C2 communication. In C2 authorization processing for direct C2 communication, the USS / UTM may provide the UAV with information about the UAV, pairing information, and application information for direct C2 communication. The pairing information may be information about the UAV-C that will perform C2 communication. In ST1117 to ST1122, the UAV and UAV-C perform PC5 L2 link establishment processing. ST1123 enables direct C2 communication between the UAV and the UAV-C.

[0234] In ST1307, the UAV measures the communication quality of PC5. The indicator measurement settings may be notified, for example, from the USS / UTM or from the base station. In the example in Figure 13, communication quality is set as the switching decision indicator. The UAV measures the communication quality using the received indicator measurement settings. For example, the UAV may measure the communication quality periodically. In ST1309, the UAV decides to send a condition setting request for switching to indirect C2 communication. For example, the UAV may use an event trigger for this decision. For example, if the communication quality of PC5 falls below a predetermined value, the UAV may send a condition setting request for switching to indirect C2 communication. Event settings such as predetermined values ​​may be included in the indicator measurement settings.

[0235] In ST1311, the UAV performs PDU session modification processing for indirect C2 communication and performs C2 authorization processing for indirect C2 communication at the same time. In the C2 authorization processing for indirect C2 communication, the UAV may send a condition setting request to the USS / UTM. The USS / UTM may notify the UAV of the switching condition setting. The switching condition setting may include, for example, the switching condition setting or switching policy or parameters or information used for C2 communication switching as described above. In the example in Figure 13, the switching condition setting may be a setting for determining whether to switch from direct C2 communication to indirect C2 communication. The UAV may use the acquired switching condition setting to determine whether to switch C2 communication.

[0236] The USS / UTM may notify the base station of a first measurement setting request. Upon receiving the first measurement setting request, the base station transmits the indicator measurement setting to the UAV. The USS / UTM may notify the base station of a condition setting request. Upon receiving the condition setting request, the base station may transmit the switching condition setting to the UAV.

[0237] Some or all of the processing related to the C2 communication switching of ST1311 may be performed separately from the C2 authorization processing for C2 communication. In the example in Figure 13, these processes are performed in the C2 authorization processing for C2 communication.

[0238] In ST1115, the base station notifies the UAV of the indicator measurement settings. The base station may also notify the UAV of the switching condition settings. These settings are for switching from direct C2 communication to indirect C2 communication. The base station may also notify the USS / UTM of the switching condition settings. The USS / UTM may notify the UAV of the switching condition settings. Upon receiving the switching condition settings, the UAV can use the indicator measurement settings and the switching condition settings to determine whether to switch to C2 communication.

[0239] In ST1125 to ST1129, the UAV measures a switching decision index using the index measurement settings and determines a C2 communication switch using the switching condition settings. If the switching conditions are met, the UAV starts the C2 communication switching process. In ST1131 to ST1135, a C2 communication switch from direct C2 communication to indirect C2 communication takes place. In ST1341, the UAV sends a switching notification to the USS / UTM indicating the switch from direct C2 communication to indirect C2 communication. The USS / UTM can recognize that the C2 communication between the UAV and UAV-C has been switched to indirect C2 communication. In ST1107, the UAV communicates indirect C2 with UAV-C via the base station and the USS / UTM.

[0240] A USS / UTM that receives a switching request from a UAV indicating a switch from direct C2 communication to indirect C2 communication may transmit information indicating the switch from direct C2 communication to indirect C2 communication to a base station or other NW node. Alternatively, the UAV may transmit information indicating the switch from direct C2 communication to indirect C2 communication to a base station or other NW node. This information may include at least one of the following: information about the UAV and information about the UAV-C that was performing direct C2 communication. A switching request indicating a switch from direct C2 communication to indirect C2 communication may be used to transmit this information. The base station and other NW nodes can recognize the switch from direct C2 communication to indirect C2 communication.

[0241] ST1343 may perform a PC5 connection release process between the UAV and the UAV-C. The PC5 L2 link between the UAV and the UAV-C is released. This avoids the unnecessary use of PC5 resources by the UAV and the UAV-C.

[0242] By doing this, the C2 communication between the UAV and the UAV-C is switched from direct C2 communication to indirect C2 communication.

[0243] Figure 14 shows another example sequence of C2 communication switching processing from direct C2 communication to indirect C2 communication for C2 communication between a UAV and a UAV-C. Steps common to Figures 11, 12, and 13 are given the same step numbers, and common explanations are omitted. Figure 14 discloses an example sequence of C2 authorization processing that integrates the C2 authorization processing for indirect C2 communication and the C2 authorization processing for direct C2 communication. Figure 14 also discloses an example in which direct C2 communication is prioritized.

[0244] In this way, the C2 communication between the UAV and UAV-C is switched from direct C2 communication to indirect C2 communication. ST1205 pre-performs C2 authorization processing for both indirect and direct C2 communication, and notifies the UAV of settings for determining whether to switch from indirect to direct C2 communication and settings for determining whether to switch from direct to indirect C2 communication. This enables early C2 communication switching.

[0245] In the example above, the UAV measures the switching indicator and makes the decision to switch to C2 communication, but the UAV-C may also measure the switching indicator and / or make the decision to switch to C2 communication. The method disclosed above may be applied as appropriate. When the UAV-C measures the switching indicator and / or makes the decision to switch to C2 communication, the base station that communicates with the UAV-C should be the base station to which the UAV-C is connected.

[0246] Figure 15 shows another example sequence of the C2 communication switching process from indirect C2 communication to direct C2 communication for C2 communication between a UAV and a UAV-C. It discloses an example sequence in which the base station determines the C2 communication switching. Steps common to Figures 11 and 12 are given the same step numbers, and common explanations are omitted.

[0247] In ST1125, the UAV measures the communication quality of Uu. In ST1507, the UAV transmits the measurement result of the communication quality to the base station. In ST1127, the UAV measures the communication quality of PC5. In ST1509, the UAV transmits the measurement result of the communication quality to the base station. The UAV may transmit the measurement result of Uu and the measurement result of PC5 together to the base station. The measurement of Uu and the measurement of PC5 may be performed at close intervals. The measurement of Uu and the measurement of PC5 may be performed within a predetermined time. The predetermined time may be set in advance. For example, the predetermined time may be included in the indicator measurement setting. The base station receives the measurement result of the communication quality of Uu and the measurement result of the communication quality of PC5. In ST1529, the base station uses the received measurement results of the communication quality of Uu and PC5 to determine whether to switch to C2 communication. The base station may determine C2 communication switching using the switching condition settings received from the USS / UTM, or it may determine C2 communication switching using switching conditions set by the base station itself. If the switching conditions are met, in ST1531, the base station sends a switching request to the UAV. In ST1533, the UAV sends a replacement response to the base station. In ST1120 to ST1122, the UAV establishes a PC5 L2 link with the UAV-C. For example, in ST1120, the UAV may send a direct communication request including the switching request to the UAV-C. In ST1122, the UAV-C may send a direct communication response including the switching response to the UAV. In ST1135, the UAV and UAV-C switch to C2 communication. That is, the UAV and UAV-C switch to direct C2 communication. In ST1139, C2 communication takes place between the UAV and the UAV-C.

[0248] In ST1541, the UAV may send a switchover completion notification to the base station. The switchover completion notification may include information indicating that the UAV and UAV-C have completed switching from indirect C2 communication to direct C2 communication. The base station can recognize that the C2 communication switchover between the UAV and UAV-C has been completed. In ST1543, the base station may send a switchover notification to the USS / UTM. The switchover notification may include information indicating that the switchover between the UAV and UAV-C has been completed from indirect C2 communication to direct C2 communication. The USS / UTM can recognize that the C2 communication switchover between the UAV and UAV-C has been completed.

[0249] In this way, the base station can determine when to switch to C2 communication. The base station can determine whether to switch the C2 communication between the UAV and the UAV-C from indirect C2 communication to direct C2 communication. The base station can determine the C2 communication switch by considering the surrounding radio wave propagation conditions and the communication status with other UAVs.

[0250] Figure 16 shows another example sequence of the C2 communication switching process from indirect C2 communication to direct C2 communication between the UAV and the UAV-C. It discloses an example sequence in which the USS / UTM determines the C2 communication switching. Steps common to Figures 11 and 12 are given the same step numbers, and common explanations are omitted.

[0251] In ST1205, the USS / UTM may send a condition setting request to the base station. The base station can recognize that the USS / UTM is making a C2 communication switching decision.

[0252] In ST1115, the base station notifies the UAV of the indicator measurement settings. These indicator measurement settings may include settings for switching from indirect C2 communication to direct C2 communication and settings for switching from direct C2 communication to indirect C2 communication. In ST1601, the base station may notify the USS / UTM of the switching condition settings. Upon receiving these switching condition settings, the USS / UTM can determine whether to switch C2 communication using the measurement results and the switching condition settings. The USS / UTM may also notify the UAV of the switching condition settings. The UAV can obtain the switching condition settings for switching from indirect C2 communication to direct C2 communication and the switching condition settings for switching from direct C2 communication to indirect C2 communication.

[0253] In ST1125, the UAV measures the communication quality of Uu. In ST1607, the UAV transmits the measurement result of the communication quality to the USS / UTM. In ST1127, the UAV measures the communication quality of PC5. In ST1609, the UAV transmits the measurement result of the communication quality to the USS / UTM. The UAV may transmit the measurement result of Uu and the measurement result of PC5 together to the USS / UTM. The measurement of Uu and the measurement of PC5 may be performed at close intervals. The measurement of Uu and the measurement of PC5 may be performed within a predetermined time. The predetermined time may be set in advance. For example, the predetermined time may be included in the indicator measurement setting. The USS / UTM receives the measurement result of the communication quality of Uu and the measurement result of PC5. In ST1629, the USS / UTM uses the received measurement results of the communication quality of Uu and PC5 to determine C2 communication switching. The USS / UTM may determine C2 communication switching using switching conditions set by the USS / UTM itself, or it may determine C2 communication switching using switching conditions received from the base station. If the switching conditions are met, in ST1631, the USS / UTM sends a switching request to the UAV. In ST1633, the UAV sends a switching response to the USS / UTM. Communication between the UAV and the USS / UTM may be conducted via the base station and CN node. The UAV establishes a PC5 L2 link with UAV-C using ST1120 to ST1122. For example, in ST1120, the UAV may send a direct communication request including a switching request to UAV-C. In ST1122, UAV-C may send a direct communication response including a switching response to the UAV. At ST1135, the UAV and UAV-C switch to C2 communication. That is, the UAV and UAV-C directly switch to C2 communication. At ST1139, C2 communication takes place between the UAV and UAV-C.

[0254] In ST1641, the UAV may send a switchover completion notification to the USS / UTM. This switchover completion notification may include information indicating that the UAV and UAV-C have completed the switchover from indirect C2 communication to direct C2 communication. The USS / UTM can then recognize that the C2 communication switchover between the UAV and UAV-C has been completed.

[0255] In this way, the USS / UTM can determine when to switch C2 communication. The USS / UTM can determine when to switch the C2 communication between the UAV and UAV-C from indirect C2 communication to direct C2 communication. The USS / UTM can determine the C2 communication switch by considering the communication status of UAV-C and other UAVs.

[0256] The method disclosed in this embodiment enables switching between indirect C2 communication and direct C2 communication between the UAV and UAV-C. For example, even if there are obstacles between the UAV and UAV-C or between the UAV and the base station due to the surrounding environment, communication between the UAV and UAV-C can continue without interruption. The UAV-C can continue to control the UAV. This avoids the risk of the UAV becoming uncontrollable and colliding with other objects.

[0257] When initiating C2 communication, the UAV may decide whether to perform direct or indirect C2 communication. The method disclosed above may be applied as appropriate to this decision. When initiating C2 communication, even if there are obstacles between the UAV and the UAV-C or between the UAV and the base station due to the surrounding environment, the UAV-C can control the UAV using a more suitable C2 communication method.

[0258] This document discloses Radio Link Failure (RLF) for a UAV. The UAV may transmit information regarding RLF between the UAV and a cell to the UAV-C using a PC5 connection. The UAV may also notify the UAV-C of information regarding RLF between cells in indirect C2 communication using direct PC5 communication. Information regarding RLF between the UAV and a cell may include, for example, at least one of the following: information regarding RLF, information regarding the UAV, pairing information, information regarding the UAV-C, information regarding the PDU session, information regarding the PC5 L2 link, information regarding the application (which may also be information regarding UAS services), information regarding the cell where the RLF occurred, information regarding the altitude where the RLF occurred, and information regarding the location or area where the RLF occurred. The UAV-C may transmit the received information regarding RLF between the UAV and a cell to a RAN node, CN node, or USS / UTM. A RAN node may be a base station to which the UAV-C is connected.

[0259] A UAV that detects an inter-cell RLF may establish a PC5 L2 link with the UAV-C and transmit information about the RLF between the UAV and the cell to the UAV-C before switching the C2 communication to direct C2 communication. Alternatively, a UAV that detects an inter-cell RLF may switch the C2 communication from indirect C2 communication to direct C2 communication. The UAV may then transmit information about the RLF between the UAV and the cell to the UAV-C using direct C2 communication.

[0260] UAV-C, upon receiving information regarding the RLF between the UAV and the cell, may switch from indirect C2 communication to direct C2 communication. USS / UTM, upon receiving information regarding the RLF between the UAV and the cell, may also switch from indirect C2 communication to direct C2 communication.

[0261] This allows C2 communication to continue even if an RLF (Rapid Field Failure) occurs between the UAV and the cell.

[0262] A base station that has received information regarding a UAV and inter-cell RLF may transmit information regarding the UAV and inter-cell RLF to the base station to which the UAV is connected. For example, a base station that has received information regarding a UAV and inter-cell RLF may use the information regarding the cell that caused the RLF, which is included in the information regarding the UAV and inter-cell RLF, to transmit information regarding the UAV and inter-cell RLF to the base station to which the UAV is connected. A base station that has experienced an RLF with a UAV can receive this information via UAV-C and recognize the RLF of the UAV early. For example, it can release the connection with the UAV that caused the RLF.

[0263] The UAV may transmit information regarding the RLF of the SL between the UAV and UAV-C to the base station using an inter-cell connection. The UAV directly notifies the base station of information regarding the SL RLF of C2 communication using an RRC connection with the cell. The information regarding the RLF between the UAV and UAV-C may include, for example, at least one of the following: information regarding the RLF, information regarding the UAV, pairing information, information regarding the UAV-C, information regarding the PDU session, information regarding the PC5 L2 link, information regarding the application (which may also be information regarding the UAS service), information regarding the altitude at which the RLF occurred, and information regarding the location or area at which the RLF occurred. The base station may transmit the received information regarding the RLF between the UAV and UAV-C to a RAN node, CN node, or USS / UTM. The RAN node may be the base station to which the UAV-C is connected.

[0264] A UAV that detects an RLF between the UAV and UAV-C may establish an RRC connection with the cell and transmit information about the RLF between the UAV and UAV-C to the base station before switching C2 communication to indirect C2 communication. Alternatively, a UAV that detects an RLF between the UAV and UAV-C may switch C2 communication from direct C2 communication to indirect C2 communication. The UAV may then transmit information about the RLF between the UAV and UAV-C to the base station using indirect C2 communication.

[0265] A base station that receives information regarding the RLF between the UAV and UAV-C may switch from direct C2 communication to indirect C2 communication. A USS / UTM that receives information regarding the RLF between the UAV and UAV-C may switch from direct C2 communication to indirect C2 communication.

[0266] This allows C2 communication to continue even if an RLF (Rapid Field Failure) occurs between the UAV and the UAV-C.

[0267] Although RLF has been disclosed, it may be applied as appropriate to the release of RRC connections. It may be applied to the release of RRC connections in Uu, or to the release of SL RRC connections in PC5. C2 communication can continue even if an RRC connection is released between the UAV and the cell, or if an SL RRC connection is released between the UAV and the UAV-C.

[0268] The UAV may transmit information regarding the inter-cell RLF to the cell whose RRC connection has been re-established. The cell may transmit the received information regarding the inter-cell RLF to a RAN node, CN node, or USS / UTM. The RAN node may be a base station to which the UAV-C is connected. The UAV may perform indirect C2 communication using the cell whose RRC connection has been re-established.

[0269] The UAV may transmit information regarding the RLF between the UAV and UAV-C to the UAV-C after the RRC connection of the SL has been re-established. The UAV-C may transmit the received information regarding the RLF between the UAV and UAV-C to a RAN node, CN node, or USS / UTM. The RAN node may be a base station to which the UAV-C is connected. The UAV may perform indirect C2 communication after the RRC connection between the UAV-C and the SL has been re-established.

[0270] In this way, even if an RLF occurs, the UAV can continue C2 communication while maintaining an RRC connection or SL RRC connection.

[0271] The method for notifying RLF information disclosed above may be appropriately applied to communication between UAVs. The relationship between UAV and UAV-C may be replaced with the relationship between UAV and UAV and applied as appropriate. For example, in communication between UAV1 and UAV2, if UAV1 experiences RLF in indirect communication via a base station, UAV1 transmits information regarding inter-cell RLF using direct communication with UAV1 and UAV2 via a PC5 connection. If UAV1 experiences RLF in direct communication with UAV2 via a PC5 connection, UAV1 transmits information regarding inter-UAV RLF using indirect communication via a base station. The same applies to UAV2. In this way, even if RLF occurs, the UAVs can continue inter-UAV communication while maintaining an RRC connection or SL RRC connection.

[0272] Candidate UAV-Cs may be provided. Candidate UAV-Cs are UAV-Cs that can control the same UAV. Candidate UAV-Cs may also be UAV-Cs that can perform C2 communication with the same UAV. There may be one candidate UAV-C, or there may be multiple candidate UAV-Cs. When one of the candidate UAV-Cs is controlling a UAV, the other UAV-Cs of the candidate UAV-Cs do not control that UAV.

[0273] The USS / UTM transmits information about candidate UAV-C to the UAV. The USS / UTM may transmit this information via a network node. For example, it may transmit this information during C2 authorization processing. For example, pairing information may include this information. For example, it may include this information in switching condition settings or indicator measurement settings. For example, candidate UAV-C may be set as the UAV-C to be measured for the switching decision indicator. The USS / UTM may transmit this information to the base station in a first measurement setting request. The base station may transmit this information to the UAV in an indicator measurement setting. The base station may determine the candidate UAV-C. For example, a base station that has received information about candidate UAV-C from the USS / UTM may determine some or all of the UAV-Cs among the candidate UAV-Cs to be candidate UAV-C. The base station may transmit information about the determined candidate UAV-C to the USS / UTM or the UAV.

[0274] Candidate UAV-C may be a UAV-C capable of direct C2 communication with the UAV. The UAV may use candidate UAV-C as the target for PC5 communication quality measurement. The UAV may establish a PC5 L2 link with candidate UAV-C. For example, the UAV may establish a PC5 L2 link using the PC5 L2 link to measure the PC5 communication quality between candidate UAV-Cs. The UAV may perform discovery processing on candidate UAV-C. The UAV may measure the PC5 communication quality between candidate UAV-Cs using discovery processing. The UAV can obtain the PC5 communication quality between candidate UAV-Cs.

[0275] A UAV-C that performs direct C2 communication may be selected from among candidate UAV-Cs. The PC5 communication quality between candidate UAV-Cs may be used in the C2 communication switching decision. For example, the UAV-C with the best PC5 communication quality between the UAV and the candidate UAV-C may be determined as the UAV-C that performs direct C2 communication. For example, when a UAV performs a C2 communication switching decision, the UAV will determine the UAV-C with the best PC5 communication quality between it and the set candidate UAV-C as the UAV-C that performs direct C2 communication. In this way, it becomes possible to perform direct C2 communication with a more appropriate UAV-C. The UAV-C within the candidate UAV-C and the base station may be used in the C2 communication switching process. For example, the UAV may measure the communication quality of the UAV-C within the candidate UAV-C and the communication quality of the base station, and determine the UAV-C or base station with the best measurement result to switch C2 communication to. This enables a more appropriate C2 communication switching process.

[0276] C2 communication with a UAV may be switched between UAV-Cs within the candidate UAV-C. The method disclosed above may be applied as appropriate. Switching of UAV-Cs becomes possible in C2 communication. The UAV can communicate with a more appropriate UAV-C in C2 communication.

[0277] The UAV may detect one or more UAV-Cs capable of direct C2 communication during the discovery process. For example, the same application information may be set on the UAV and one or more UAV-Cs capable of C2 communication. One or more UAV-Cs may be detected using this application information. For example, pairing information between the UAV and one or more UAV-Cs capable of C2 communication may be transmitted during the discovery process. One or more UAV-Cs may be detected using this pairing information. The UAV becomes capable of detecting one or more UAV-Cs capable of direct C2 communication. The UAV may transmit information about the detected one or more UAV-Cs capable of direct C2 communication to the USS / UTM. The UAV may transmit this information together with the communication quality between the UAV and each UAV-C. The USS / UTM can recognize the UAV and one or more UAV-Cs capable of direct C2 communication. For example, the USS / UTM may select a UAV-C from among the UAV-Cs for C2 communication with the UAV. The USS / UTM may transmit information about the selected UAV-C to the UAV. The USS / UTM may also transmit information to the selected UAV-C indicating that it is for C2 communication with the UAV. The selected UAV-C can then recognize that it is for C2 communication with the UAV.

[0278] When one UAV-C controls a UAV, the UAV-C or the UAV may transmit information to other candidate UAV-Cs indicating that the UAV-C is controlling the UAV. This information may include information about the UAV-C that is controlling the UAV. This transmission may be performed, for example, via USS / UTM. This transmission may be performed, for example, via PC5 communication between UAV-Cs or between UAVs and UAV-Cs. In this way, for example, other candidate UAV-Cs can clearly recognize that they are not controlling the UAV, thereby reducing malfunctions.

[0279] By providing candidate UAV-C, the C2 communication switching process becomes more flexible and allows for switching to the appropriate node. This enables a more robust C2 communication switching process and improves the continuity of C2 communication.

[0280] A method for switching C2 communication in C2 communication between a UAV and a UAV-C has been disclosed above. The method disclosed above may be appropriately applied to switching between direct and indirect communication in communication between UAVs. For example, in communication between UAV1 and UAV2, UAV1 performs indirect communication via a base station. UAV1 establishes an RRC connection with the base station. UAV1 may establish a PDU session with an NW node via the base station. UAV1 transmits information about the opposing UAV2 to the NW node. UAV2 does the same. UAV1 performs indirect communication with UAV2 via the base station and the NW node. For example, the NW node may perform routing using the information about the opposing UAVs received from UAV1 and UAV2 and the information about each PDU session. Indirect communication takes place between UAV1 and UAV2. UAV1 may perform indirect communication with UAV2 via USS / UTM.

[0281] UAV1 switches between indirect and direct communication by appropriately applying the method disclosed above. UAV1 should establish a PC5 L2 link with UAV2 by appropriately applying the method disclosed above. Direct communication using the PC5 connection becomes possible between UAV1 and UAV2. The same applies to UAV2. Switching from direct to indirect communication should also be done by appropriately applying the method disclosed above. In this way, switching between indirect and direct communication becomes possible in communication between UAVs. It becomes possible to continue communication between UAVs.

[0282] In addition, the order of steps in each sequence of Figures 11 to 16 may be changed as long as there is no inconsistency. Furthermore, each sequence of Figures 11 to 16 may be modified as appropriate based on the switching decision indicator used. In each sequence of Figures 11 to 16, one or more NW nodes may be added, and one or more steps may be added. For example, an LMF or GMLC may be added, and a step may be added in which the switching decision node obtains the position of the UAV from the LMF or GMLC as a switching decision indicator.

[0283] Embodiment 2. Distance information between UAVs may be required. For example, when multiple UAVs are traveling in a convoy and it is desired to maintain the distance between UAVs within a predetermined range, or when it is desired to maintain a distance greater than a predetermined value from a specific UAV. Support for UAS is being considered in the mobile communication system under 3GPP. 3GPP supports UAV tracking and DAA (Detect and Avoid) functions (see Non-Patent Document 30). The UAV tracking function determines the position of the UAV and notifies the USS / UTM of the UAV's location information. The DAA function is a function that detects nearby UAVs and enables avoidance processing. In Network-Based / Assisted DAA, the UAV's location information (absolute position and relative position) is derived using the LCS function (see Non-Patent Document 25). Relative Proximity Analytics is performed on the derived location information together with NWDAF.

[0284] However, in the disclosed DAA, the CN node, either the LMF or GMLC, derives the location information. Therefore, the UAV needs to be connected to a base station. However, the UAV may be in a state where it is not connected to a base station. In such a state, the disclosed DAA cannot be used, which presents a problem.

[0285] This embodiment discloses a method for solving these problems.

[0286] The system performs a process to measure the distance between UAVs when the UAVs are not connected to a base station. Hereafter, this process may be referred to as the distance measurement process. Distance measurement may be performed between multiple UAVs using RTT measurement in the SL. An SL-PRS may be provided for measuring the distance between UAVs. A frequency may be set for measuring the distance between UAVs. The frequency may be, for example, one or more bands, one or more CCs, one or more BWPs, one or more RBs, one or more subcarriers, or a combination thereof. A time may be set for measuring the distance between UAVs. The time may be, for example, one or more radio frames, one or more subframes, one or more slots, one or more symbols, one or more TTIs (Transmission Time Intervals), or a combination thereof. The time for measuring the distance between UAVs may be set as a measurement gap. In this way, flexible settings for measuring the distance between UAVs in terms of time and frequency are possible.

[0287] A reference UAV may be set to support the distance measurement process. The reference UAV may be a UAV whose location is known. The reference UAV may be a UAV located in a predetermined area. The location of the reference UAV or the predetermined area may be determined statically. This configuration is suitable, for example, when the reference UAV does not move. The location of the reference UAV or the predetermined area may be changed quasi-statically or dynamically. This configuration is suitable, for example, when the reference UAV moves. The reference UAV may be used in the distance measurement process. This makes it easier to measure the distance between UAVs.

[0288] The distance between UAVs may be, for example, a planar distance or a 3D distance. The distance may also be, for example, a combination of planar distance and altitude information. As information related to the distance between UAVs, the position of the UAV being measured may be measured. The position of the UAV may be, for example, an absolute position or a relative position. For example, the position of the UAV may be a relative position to a reference UAV. The altitude of the UAV being measured may also be measured.

[0289] UAV groups may be established. UAV groups may be established in response to UAS services. UAV groups may include one or more standard UAVs.

[0290] A request may be made to cause a specific node to measure the distance between UAVs. Hereafter, this request may be referred to as a distance measurement request. UAV-C sends a distance measurement request to a UAV. USS / UTM may send a distance measurement request to UAV-C. UAV-C, having received a distance measurement request from USS / UTM, may send a distance measurement request to the UAV. USS / UTM can notify a UAV of a distance measurement request. A UAV may send a distance measurement request to another UAV. For example, a certain UAV in a UAV group may send a distance measurement request to another UAV in the UAV group. For example, a UAV that has received a distance measurement request from UAV-C may send a distance measurement request to another UAV. A distance measurement request may include at least one of the following: information about the UAS service, information about the UAV to be measured, information about the requesting UAV, and settings for measuring the distance between UAVs. Hereafter, the settings for measuring the distance between UAVs may be referred to as distance measurement settings. Information about the UAVs that are the target of distance measurement may, for example, be information about one or more UAV pairs. A UAV that receives a distance measurement request measures the distance between the target UAV pair. Information about the UAVs that are the target of distance measurement may, for example, be information about a UAV group. A UAV that receives a distance measurement request may measure the distance between different UAVs within the target UAV group. Measuring the distance between UAVs may be done using distance measurement settings.

[0291] The base station may send a distance measurement request to the UAV. The transmission of the distance measurement request may occur when the UAV is connected to a cell. For example, the transmission of the distance measurement request may occur during C2 authorization processing. For example, the transmission of the distance measurement request may occur during PDU session establishment processing for C2 communication. The UAV records the information contained in the distance measurement request. When the UAV is not connected to a cell, the UAV may perform distance measurement processing using the recorded information. Although the base station is disclosed as the source node for the distance measurement request, other nodes may also send distance measurement requests. For example, a USS / UTM may send a distance measurement request to the UAV. Similarly, the transmission of the distance measurement request may occur when the UAV is connected to a cell.

[0292] Regarding the distance measurement settings, the method for setting the index measurement settings disclosed in Embodiment 1 may be applied as appropriate. Furthermore, the distance measurement settings may include at least one of the frequency setting and time setting for measuring the distance between UAVs.

[0293] A request for setting distance measurement settings may be provided. Hereafter, this request may be referred to as a second measurement setting request to distinguish it from the first measurement setting request disclosed in Embodiment 1. The node that sets the distance measurement settings may also be referred to as a third setting node. For example, a base station may set the distance measurement settings as a third setting node. The source node of the distance measurement request may send a second measurement setting request to the third setting node. For example, a USS / UTM may send a second measurement setting request to a base station. The node that receives the second measurement setting request sets the distance measurement settings. The third setting node may send the distance measurement settings to the source node of the second measurement setting request. For example, a base station may send the set distance measurement settings to a USS / UTM. The second measurement setting request may include at least one of the following: information about the source node of the second measurement setting request, information about the destination node of the second measurement setting request, and information about the destination node of the distance measurement request.

[0294] A UAV measures the distance between itself and another UAV. A UAV may also measure the distance between itself and a reference UAV. A UAV may also measure the distance between another UAV and a reference UAV, and the distance between itself and a reference UAV. A UAV that receives a distance measurement request may use the information contained in the request to measure the distance between itself or the reference UAV and a predetermined UAV. In this way, a UAV can obtain distance measurements between UAVs. A UAV may also obtain the time taken to measure the distance between UAVs. Hereafter, this time may be referred to as the measurement time. The distance measurement result may include the measurement time corresponding to the distance measurement.

[0295] A request may be made to a specific node to derive the distance between UAVs. Hereafter, this request may be referred to as a distance derivation request. A node that derives the distance between UAVs may be provided. Hereafter, this node may be referred to as a distance derivation node. The process of deriving the distance between UAVs using the measurements obtained by the distance measurement process may be referred to as the distance derivation process. In addition, a node that measures the distance between UAVs may be provided separately from the distance derivation node. Hereafter, this node may be referred to as a distance measurement node. For example, UAV-C sends a distance derivation request to the distance derivation node. USS / UTM may send a distance derivation request to UAV-C. UAV-C, having received a distance derivation request from USS / UTM, may send a distance derivation request to the distance derivation node. A distance derivation request may include at least one of the following: information about the UAS service, information about the target UAV from which to derive the distance between UAVs, information about the UAV to which the distance derivation request is sent, and information about the UAV (or UAV-C) from which the distance derivation request is sent. The distance derivation node may request a distance measurement node to provide a measurement of the distance between UAVs. In response to the request, the distance measurement node may send the measurement to the distance derivation node. The distance derivation node uses the measurement to derive the distance between the target UAVs. The distance derivation node may be a UAV. The distance derivation node may be the UAV that performed the distance measurement between UAVs (i.e., the distance measurement node).

[0296] A response regarding the distance between UAVs may be provided. Hereafter, this response may be referred to as a distance response. The distance response may include at least one of the following: information about the UAS service, information about the target UAV from which the distance between UAVs is derived, information about the distance between the target UAVs from which the distance between UAVs is derived, a distance measurement, information about the measurement time corresponding to the distance measurement, information about the destination node to which the distance response is sent, and information about the source node to which the distance response is sent. For example, the distance derivation node sends the distance response to the source node of the distance derivation request. For example, UAV-C may send a distance derivation request to a UAV, the UAV may derive the distance between the target UAVs, and then the UAV may send a distance response to UAV-C. In this way, the source node of the distance derivation request can recognize the distance between UAVs.

[0297] The information notified by the UAV's tracking function (see Non-Patent Document 30) may include at least one of the following: distance information between the UAV and UAV-C, distance information between UAVs, and distance information between the UAV and UE. For example, the USS / UTM may acquire this information using its tracking function.

[0298] Figure 17 shows an example sequence of the process for notifying UAV-C of the distance between UAVs. In the example in Figure 17, there are n UAVs, from UAV1 to UAVn. UAV1 to UAVn may be configured as a UAV group. UAV1 is both a distance measurement node and a distance derivation node. At ST1701, UAV-C sends a distance measurement request (or distance derivation request) to UAV1. Communication between UAV-C and UAV1 may be performed using PC5. UAV-C and UAV1 may also communicate directly using C2. Upon receiving the distance measurement request, UAV1 performs a distance measurement process at ST1703 to measure the distance between UAV1 and each UAV (UAV2, ..., UAVn). For example, the RTT may be measured between each UAV using PC5. The distance measurement process may appropriately apply, for example, the method described in Non-Patent Document 31 (Chapter 6.8). In ST1705, UAV1 performs a distance derivation process to derive the distance between UAV1 and each UAV (UAV2, ..., UAVn). For example, UAV1 may derive the distance between each UAV using the RTT measurement results measured between each UAV. In ST1707, UAV1 transmits the derived distance between UAVs to UAV-C. UAV1 may transmit a distance response to UAV-C that includes information about the distance between UAVs. In this way, UAV-C can obtain the distance between UAVs without requiring an NW node. UAV-C can obtain the distance between UAVs of UAVs that are not connected to a base station.

[0299] In ST1709, UAV-C may notify the USS / UTM of the distance between UAVs. Hereafter, this notification may be referred to as a distance notification. The USS / UTM can obtain the distance between UAVs that are not connected to the base station. UAV-C may also send the distance notification to other network nodes (for example, RAN nodes or CN nodes). Alternatively, UAV1 may send the distance notification to network nodes (for example, RAN nodes, CN nodes, or USS / UTM) without going through UAV-C.

[0300] An alarm related to the distance between UAVs may be provided. Hereafter, this alarm may be referred to as a distance alarm. The distance alarm is used to notify information indicating a situation when the distance between UAVs meets a predetermined condition. The predetermined condition may include, for example, at least one of the following: the distance between UAVs has fallen outside a predetermined range, and the distance between UAVs has fallen below a predetermined value. Hereafter, the predetermined condition may be referred to as a distance alarm condition. For the process of notifying a distance alarm, the methods for measuring the distance between UAVs and deriving the distance between UAVs disclosed above may be used. Information regarding the distance between UAVs becomes available for notifying a distance alarm.

[0301] A request may be made to notify a specific node of a distance alarm. Hereafter, this request may be referred to as a distance alarm request. For example, UAV-C may send a distance alarm request to a node that determines the distance alarm conditions. The distance alarm request may include at least one of the following: information about the UAS service, information about the node from which the distance alarm request was sent, information about the node to which the distance alarm request was sent, information about the UAV that is the target of the distance alarm, settings related to the distance alarm, information included in the distance measurement request disclosed above, and information included in the distance derivation request disclosed above. Hereafter, settings related to the distance alarm may be referred to as distance alarm settings. The node that determines the distance alarm conditions can use the information included in the distance measurement request or distance derivation request to perform a distance measurement process or a distance derivation process, and use the acquired distance between the UAVs to notify a distance alarm.

[0302] The source node of the distance alarm request, the destination node of the distance alarm request, and the notification method for the distance alarm request may be appropriately applied to the notification method for distance measurement requests or distance derivation requests disclosed above.

[0303] A response to distance alarm requests may be provided. Hereafter, this response may be referred to as a distance alarm response. A node that receives a distance alarm request may send a distance alarm response to the source node of the distance alarm request. The source node can then recognize that the destination node of the distance alarm request has received the request. This can reduce malfunctions in the inter-UAV distance alarm processing.

[0304] As described above, distance alarm settings are provided. The source node of a distance alarm request may set the distance alarm settings. The distance alarm settings may include information on how to notify distance alarms and may include information on who the distance alarms should be notified to (e.g., UAVs, UAV-Cs, and NW nodes). The distance alarm settings may include setting decision conditions for notifying distance alarms, i.e., setting the distance alarm conditions described above. A node that uses the distance alarm settings to decide whether to notify a distance alarm may be called an alarm decision node. An alarm decision node may send a distance alarm if the distance alarm conditions are met. The distance alarm settings may include, for example, a predetermined value, such as a threshold, for deciding whether to send a distance alarm for the distance between UAVs. For example, an alarm decision node may decide to send a distance alarm if the distance between UAVs falls below a predetermined value (i.e., a threshold). For example, an alarm decision node may decide to send a distance alarm if the distance between UAVs falls outside a predetermined range. For example, an alarm decision node may decide to send a distance alarm if the distance between UAVs falls within a predetermined range. The predetermined value for determining whether to send an alarm may be, for example, a function of velocity, or for example, a function of acceleration. For example, predetermined values ​​may be set for determining whether to send an alarm for each velocity range. The distance between UAVs may be a three-dimensional distance, as described above, or a planar distance. The distance may be, for example, a combination of planar distance and altitude information. The distance alarm condition may further include conditions relating to altitude or altitude range. For example, the distance alarm condition may include a condition relating to the planar distance between UAVs and a condition relating to the altitude of those UAVs. Because altitude information can be incorporated into the decision to notify a distance alarm, it becomes possible to set flexible distance alarm conditions for UAVs.

[0305] In distance alarm conditions, a predetermined value may be set for each service. This makes it possible to set distance alarm settings corresponding to each service. In distance alarm conditions, a predetermined value may be set for each altitude or altitude range. This makes it possible to set alarms by altitude. In distance alarm conditions, a predetermined value (for example, a threshold) may be set for each UAV or for each UAV group. This makes it possible to notify alarms between UAV groups.

[0306] One or more distance alarm conditions may be set. One or more alarm conditions may be set to determine whether to notify a distance alarm. This allows for alarm settings that are appropriate to the surrounding environment and conditions of the UAV.

[0307] Regarding alarm condition settings, the switching condition settings and indicator measurement settings disclosed in Embodiment 1, as well as the distance measurement settings disclosed above, may be applied as appropriate. Distance alarm settings may be set separately from distance measurement settings. This allows for more flexible settings.

[0308] A RAN node may configure distance alarm settings. A RAN node may send distance alarm settings to a UAV. The source node of a distance alarm request may also send a request for distance alarm settings to a RAN node. Hereafter, this request may be referred to as a distance alarm setting request. A node that has configured distance alarm settings may send the distance alarm settings to the source node of the distance alarm setting request. For example, a USS / UTM sends a distance alarm setting request to a base station. The base station configures the distance alarm settings and sends the distance alarm settings to the USS / UTM. By having a RAN node configure distance alarm settings, it becomes possible to configure distance alarm settings that take into account, for example, radio conditions.

[0309] The transmission of distance alarm settings is preferable when the UAV is connected to a cell. For example, the transmission of distance alarm settings may occur during C2 authorization processing. For example, the transmission of distance alarm settings may occur during PDU session establishment processing for C2 communication. The UAV records the information contained in the distance alarm settings. When the UAV is not connected to a cell, it is preferable for the UAV to perform distance alarm processing using the recorded information. For example, when the UAV is connected to a cell, the USS / UTM sets distance alarm settings and notifies the UAV of these settings in advance. Subsequently, the UAV becomes disconnected from the cell. The UAV can then perform distance alarm processing using the distance alarm settings even when not connected to a cell.

[0310] The UAV determines the distance alarm conditions. The UAV may use distance alarm settings to determine if the distance alarm conditions are met. As mentioned above, distance alarms may be set up. The UAV sends a distance alarm to the source node of the distance alarm request. For example, if UAV-C is the source node of the distance alarm request, the UAV will send a distance alarm to UAV-C if the alarm conditions are met.

[0311] UAV-C may send distance alarms to the USS / UTM. UAV-C may send distance alarms received from UAVs to the USS / UTM. For example, if the USS / UTM is the source node of a distance alarm request, the UAV may send distance alarms to the USS / UTM via UAV-C. The USS / UTM can recognize that the distance alarm conditions have been met in the UAV. UAV-C or the USS / UTM may send distance alarms to UAVs that are notified of the distance alarm. The notified UAVs can recognize that the alarm conditions have been met in other UAVs, i.e., that a distance alarm has occurred.

[0312] If the distance alarm conditions are met, the UAV may send a distance alarm to the UAVs that are subject to the distance alarm notification. The UAVs subject to the notification can then recognize that a distance alarm has occurred.

[0313] UAV-C may determine whether the distance alarm conditions are met. If the distance alarm conditions are met, UAV-C may notify the UAV of the distance alarm. If the distance alarm conditions are met, UAV-C may send a distance alarm to the USS / UTM. UAV-C may send the distance alarm to the UAV that is the target of the distance alarm notification. The target UAV can recognize that a distance alarm has occurred.

[0314] A distance alarm may include, for example, at least one of the following: information about the UAV to which the distance alarm is to be notified; distance alarm conditions; information indicating that the distance alarm conditions have been met; the distance between UAVs that cause the distance alarm to be notified (i.e., the distance between UAVs that satisfy the distance alarm conditions); the location and altitude of the UAV that is the source of the distance alarm; the location and altitude of other UAVs that cause the distance alarm to be notified (e.g., UAVs approaching the UAV that is the source of the distance alarm); information about the UAV group; information about the source node of the distance alarm; and information about the destination node of the distance alarm.

[0315] Figure 18 shows an example sequence of the distance alarm notification process to the UAV-C. Steps common to Figure 17 are given the same step numbers, and common explanations are omitted. In ST1801, UAV1 performs PDU session establishment processing and C2 authorization processing for C2 communication between USS / UTM. In the C2 authorization processing for C2 communication, USS / UTM may send distance measurement settings and distance alarm settings to UAV1. The distance alarm settings may include setting distance alarm conditions. USS / UTM may notify UAV1 of a distance alarm request.

[0316] Some or all of the processing related to distance alarm notification in ST1801 may be performed separately from the C2 authorization processing for C2 communication. In the example in Figure 18, these processes are performed in the C2 authorization processing for C2 communication.

[0317] In ST1803, ST1805, and ST1807, a PC5 L2 link is established between UAV1 and UAV-C for direct C2 communication. For example, in ST1803, UAV-C determines the destination L2 ID. In ST1805, UAV1 determines the destination L2 ID. In ST1807, UAV1 and UAV-C perform the PC5 L2 link establishment process. In ST1809, UAV1 moves outside the coverage of the base station's cell. This may release the connection to the cell. UAV1 is directly connected to UAV-C using PC5. In STS1811, UAV-C sends a distance alarm request to UAV1. Upon receiving the distance alarm request, UAV1 performs a distance measurement process in ST1703 to measure the distance between UAV1 and each UAV. In ST1705, UAV1 performs a distance derivation process to derive the distance between UAV1 and each UAV. In ST1813, UAV1 determines whether or not to notify a distance alarm. UAV1 may use the distance alarm conditions obtained from USS / UTM for this determination. In ST1813, the distance alarm conditions are met. In this case, in ST1815, UAV1 notifies UAV-C of a distance alarm.

[0318] In this way, UAV-C can receive distance alarms from UAV1, which is not connected to the base station. UAV-C may use the distance alarms from UAV1 to perform control, for example, to avoid inter-UAV collisions. Inter-UAV collisions can be avoided. UAV-C may also transmit distance alarms to network nodes (for example, RAN nodes, CN nodes, or USS / UTM).

[0319] The nodes that perform distance alarm processing are not limited to UAV1 and UAV-C, as described above. The nodes that perform distance alarm processing may include network nodes or USS / UTM. For example, the alarm decision node may be an NEF / UAS NF or a USS / UTM. The source node of a distance alarm request may notify the alarm decision node of the distance alarm request. The node that sets the distance alarm settings may notify the alarm decision node of the distance alarm settings. The alarm decision node may send a distance alarm to the source node of the distance alarm request. By incorporating network nodes, more flexible distance alarm processing becomes possible.

[0320] Distance alarm processing may be performed when the UAV is connected to a cell. A UAV-to-UAV distance measurement function including the network disclosed in 3GPP (Non-Patent Document 25 (Chapter 6.20)) may be used. The LMF or GMLC may derive the distance between UAVs using the UAV-to-UAV distance measurement function including the network. The alarm decision node may be the LMF or GMLC. Distance alarm processing in cooperation with the LMF or GMLC becomes possible.

[0321] Figure 19 shows another example sequence of distance alarm notification processing to the UAV-C. It discloses a method of including a network node and a USS / UTM in the nodes that perform distance alarm processing. The USS / UTM is the source node of the distance alarm request. The UAS NF / NEF is the node that determines the distance alarm condition (i.e., the alarm determination node). In ST1901, the USS / UTM sends a distance alarm request to the UAS NF / NEF. The UAV-C may have previously sent a distance alarm request to the USS / UTM. The USS / UTM, having received the distance alarm request, may send a distance alarm request to the UAS NF / NEF. The UAS NF / NEF, having received the distance alarm request, may send a distance measurement request to the GMLC. The GMLC may send a distance measurement request to the LMF. In ST1905, the GMLC / LMF initiates a distance measurement process to measure the distance between UAV1 and each UAV (UAV2, ..., UAVn) between the GMLC, LMF, UAV1, each UAV, and other network nodes. The GMLC / LMF then performs a distance derivation process to derive the distance between UAV1 and each UAV. If the LMF derives the distance, it may send the derivation result to the GMLC. In ST1907, the GMLC sends a distance response to the UAS NF / NEF. Upon receiving the distance response, the UAS NF / NEF can obtain information regarding the distance between UAV1 and each UAV.

[0322] In ST1909, the UAS NF / NEF determines whether to notify a distance alarm. For example, the UAS NF / NEF may use the distance alarm settings (including distance alarm conditions) included in the distance alarm request received from the USS / UTM to determine whether to notify a distance alarm. If the distance alarm conditions are met, in ST1911, the UAS NF / NEF sends a distance alarm to the USS / UTM. In this way, the USS / UTM becomes able to receive distance alarms. In ST1913, the USS / UTM may send a distance alarm to the UAV-C. The UAV-C becomes able to receive distance alarms.

[0323] By including the NW node and USS / UTM in the nodes that perform distance alarm processing, the processing load on UAV1 can be reduced. Furthermore, even if the PC5 connection between the UAV and UAV-C is not established, the USS / UTM can notify UAV-C of the distance alarm. UAV-C may use the distance alarm of UAV1 to perform control, for example, to avoid inter-UAV collisions. This makes it possible to avoid inter-UAV collisions.

[0324] Figure 20 shows another example sequence of the distance alarm notification process to UAV-C. It discloses a method of including an NW node and a USS / UTM in the nodes that perform the distance alarm processing. The USS / UTM is the source node of the distance alarm request. UAV1 is the node that determines the distance alarm condition (i.e., the alarm determination node). In ST2001, the USS / UTM sends a distance alarm request to UAV1. UAV-C may have previously sent a distance alarm request to the USS / UTM. Upon receiving the distance alarm request, the USS / UTM may send a distance alarm request to UAV1. Upon receiving the distance alarm request, UAV1, in ST1905, initiates a distance measurement process to measure the distance between UAV1 and each UAV (UAV2, ..., UAVn) between the GMLC, LMF, UAV1, each UAV, and other NW nodes. The LMF / GMLC performs a distance derivation process to derive the distance between UAV1 and each other UAV. The LMF / GMLC sends the derivation result to UAV1. UAV1 can then obtain the distance between UAV1 and each other UAV.

[0325] In ST2003, UAV1 determines whether to send a distance alarm. For example, UAV1 may use the distance alarm settings included in the distance alarm request received from USS / UTM to determine whether to send a distance alarm. If the distance alarm conditions are met, in ST2005, UAV1 sends a distance alarm to USS / UTM. In this way, USS / UTM becomes able to receive distance alarms. In ST1913, USS / UTM may send a distance alarm to UAV-C. UAV-C becomes able to receive distance alarms.

[0326] UAV1 acquires information regarding the distance between UAV1 and each UAV and determines whether to notify a distance alarm. This allows UAV1 to recognize the distance between UAVs. It also allows UAV1 to recognize whether or not a distance alarm is in effect. For example, UAV1, having determined that a distance alarm should be notified, may perform collision avoidance processing with the target UAV itself. For example, UAV1 may directly connect to PC5 with the target UAV and send a collision avoidance request to the target UAV. The target UAV that receives the collision avoidance request can then perform collision avoidance processing.

[0327] Information indicating that a collision avoidance function is present may be provided. This information may be information indicating whether or not a collision avoidance function is present. For example, this information may be included in the UE capabilities. This information may be transmitted from the UAV to other UAVs, UAV-Cs, USS / UTMs, or NW nodes. For example, UAV1 may transmit this information to other UAVs that have connected to PC5. Other UAVs may transmit this information to UAV1. UAV1 can recognize whether or not other UAVs have a collision avoidance function. Other UAVs can also recognize whether or not UAV1 has a collision avoidance function. For example, UAV1 can determine whether or not to perform collision avoidance processing or to send a collision avoidance request to the alarm target UAV based on whether or not the alarm target UAV has a collision avoidance function.

[0328] A UAV-equipped UE that determines that a distance alarm notification has been received may notify the UAV or its application of the alarm. The UAV or its application can recognize the distance alarm. A UAV-equipped UE or UAV that determines that a distance alarm notification has been received may also notify an external party of the alarm. For example, the alarm may be notified by sound, vibration, and light, or a combination of two or more of these. For example, a person or object present externally can recognize the distance alarm.

[0329] A UAV-C-equipped UE that receives a distance alarm may notify the UAV-C or the application on the UAV-C of the alarm. The UAV-C or the application on the UAV-C can recognize the distance alarm. A UAV-C-equipped UE or UAV-C that receives a distance alarm may also notify an external party of the alarm. For example, the alarm may be notified by sound, vibration, and light, or a combination of two or more of these. For example, a person or object present externally can recognize the distance alarm.

[0330] Distance alarms may be notified by linguistic display and / or audio. When notified by linguistic display and / or audio, the notification may be in a pre-set language. As another example, the UE or UE application may acquire location information of the UAV or UAV-C carrying the UE, use that location information to derive the country or region where the UAV or UAV-C is located, translate it into the language used in that country or region, and notify the distance alarm. This is effective when the UAS operates across countries or regions.

[0331] According to the method disclosed in this embodiment, a node requesting information about the distance between UAVs can obtain this information even when the UAVs are not connected to a base station. For example, a UAV-C or USS / UTM can obtain distance information between UAVs even when the UAVs are not connected to a base station, and can use this distance information to control the UAVs.

[0332] According to the method disclosed in this embodiment, a UAV, UAV-C, or NW node can have an alarm function based on the distance between UAVs, and the UAV, UAV-C, or NW node can notify other nodes of the distance alarm. For example, in response to receiving a distance alarm, the UAV-C may take control to avoid collisions. This makes it possible to avoid UAV collisions.

[0333] Embodiment 3. There are cases where the altitude of the UAV is required. For example, when information about the UAV's altitude is used to notify of the risk of falling. Support for UAS is being considered in the 3GPP mobile communication system. 3GPP supports a UAV altitude notification function (see Non-Patent Document 30 (Chapter 5.16)). In the UAV altitude notification function, the altitude of the UAV is measured and information about the altitude is notified to the USS / UTM.

[0334] The disclosed UAV altitude notification function allows the UAV to notify the USS / UTM of altitude information via a CN node. Therefore, the UAV needs to be connected to a base station. However, a UAV may be disconnected from a base station. In such a state, the disclosed UAV altitude notification function cannot be used, which presents a problem.

[0335] This embodiment discloses a method for solving these problems.

[0336] When the UAV is not connected to a base station, a process is performed to measure the altitude of the UAV (hereinafter referred to as the altitude measurement process). For the altitude measurement process, the method for measuring the switching decision index disclosed in Embodiment 1 may be applied as appropriate. For the altitude notification process, the method for notifying the distance between UAVs disclosed in Embodiment 3 may be applied as appropriate. For example, in the method disclosed in Figure 17, the distance between UAVs may be replaced with the altitude of the UAVs. Alternatively, the distance measurement process may be replaced with the altitude measurement process. In this way, UAV-C can obtain information regarding the altitude of the UAV.

[0337] An alarm related to the altitude of the UAV may be provided. Hereafter, this alarm may be referred to as an altitude alarm. The altitude alarm is used to notify information indicating a situation when the altitude of the UAV meets a predetermined condition. The predetermined condition may include at least one of the following: the altitude of the UAV has fallen outside a predetermined range; the altitude of the UAV has fallen below a predetermined value; and the change in the altitude of the UAV has exceeded a predetermined value. The change in the altitude of the UAV may be an altitude decrease or an altitude increase. The change in the altitude of the UAV may be an altitude change over a predetermined time interval. Hereafter, the predetermined condition may be referred to as an altitude alarm condition. For the process of notifying an altitude alarm, the method for measuring the altitude of the UAV disclosed above may be used. Information regarding the altitude of the UAV becomes available for notifying an altitude alarm.

[0338] Regarding the process of notifying altitude alarms, the distance alarm notification method disclosed above should be applied as appropriate. For example, with respect to (c1) a node that determines whether to notify an altitude alarm using altitude alarm conditions, (c2) a method for notifying a request to notify an altitude alarm to a specific node (hereinafter referred to as an altitude alarm request), (c3) a method for setting altitude alarm settings, (c4) a method for setting altitude alarm conditions, (c5) a method for determining whether to notify an altitude alarm using altitude alarm conditions, and (c6) an altitude alarm notification method, it is appropriate to apply, respectively, (d1) the alarm determination node mentioned above, (d2) the method for notifying a distance alarm request mentioned above, (d3) the method for setting distance alarm settings mentioned above, (d4) the method for setting distance alarm conditions mentioned above, (d5) a method for determining whether to notify a distance alarm using the distance alarm conditions mentioned above, and (d6) the method for notifying a distance alarm mentioned above.

[0339] Figure 21 shows an example sequence of the altitude alarm notification process to the UAV-C. Steps common to Figure 18 are given the same step numbers, and common explanations are omitted. In ST2101, the UAV1 performs PDU session establishment processing and C2 authorization processing for C2 communication between the USS / UTM. In the C2 authorization processing for C2 communication, the USS / UTM may send altitude measurement settings and altitude alarm settings to the UAV1. The altitude measurement settings are settings for measuring the altitude of the UAV. Regarding the altitude measurement settings, the index measurement settings disclosed in Embodiment 1 may be applied as appropriate. The altitude alarm settings may include the setting of the altitude alarm notification method and altitude alarm conditions. The USS / UTM may notify the UAV1 of an altitude alarm request.

[0340] Some or all of the processing related to the ST2101's advanced alarm notification may be performed separately from the C2 authorization processing for C2 communication. In the example in Figure 21, these processes are performed in the C2 authorization processing for C2 communication.

[0341] In ST2111, UAV-C sends an altitude alarm request to UAV1. Upon receiving the altitude alarm request, UAV1 performs altitude measurement processing in ST2112. In ST2113, UAV1 decides whether or not to notify an altitude alarm. UAV1 may use the altitude alarm conditions obtained from the USS / UTM for this decision. In ST2113, the altitude alarm conditions are met. In this case, in ST2115, UAV1 notifies UAV-C of the altitude alarm.

[0342] In this way, UAV-C can receive an altitude alarm from UAV1, which is not connected to the base station. UAV-C may use the altitude alarm from UAV1 to perform control, for example, to prevent the UAV from falling. The UAV can be prevented from falling. UAV-C may also transmit an altitude alarm to a network node (for example, a RAN node, CN node, or USS / UTM). Alternatively, UAV1 may transmit an altitude alarm to a network node (for example, a RAN node, CN node, or USS / UTM) without going through UAV-C.

[0343] A UAV-mounted UE that determines that an altitude alarm has been detected may notify the UAV or its application of the alarm. The UAV or its application can recognize the altitude alarm. A UAV-mounted UE or UAV that determines that an altitude alarm has been detected may also notify an external party of the alarm. For example, the alarm may be notified by sound, vibration, and light, or a combination of two or more of these. For example, a person or object present externally can recognize the altitude alarm.

[0344] A UAV-C-equipped UE that receives an altitude alarm may notify the UAV-C or its application of the alarm. The UAV-C or its application can recognize the altitude alarm. A UAV-C-equipped UE or UAV-C that receives an altitude alarm may also notify an external party of the alarm. For example, the alarm may be notified by sound, vibration, and / or a combination of two or more of these. For example, a person or object present externally can recognize the altitude alarm.

[0345] Altitude alarms may be notified by linguistic display and / or audio. When notified by linguistic display and / or audio, the notification may be in a pre-set language. As another example, the UE or its application may acquire location information of the UAV or UAV-C carrying the UE, use that location information to derive the country or region where the UAV or UAV-C is located, translate it into the language used in that country or region, and notify the altitude alarm. This is effective when the UAS operates across countries or regions.

[0346] According to the method disclosed in this embodiment, a node requesting UAV altitude information can obtain this information even when the UAV is not connected to a base station. For example, a UAV-C or USS / UTM can obtain UAV altitude information even when the UAV is not connected to a base station, and can use this altitude information to control the UAV.

[0347] According to the method disclosed in this embodiment, the UAV can have an alarm function based on its altitude, and the UAV can notify other nodes of the altitude alarm. For example, UAV-C may take control measures to prevent the UAV from falling in response to the reception of the altitude alarm. The UAV can avoid falling. In the example in Figure 21, the UAV makes a decision on whether or not to notify the altitude alarm, but the configuration is not limited to this. Similar to the distance alarm in Embodiment 2, the node that makes the decision on whether or not to notify the altitude alarm may be a node other than the UAV. For example, UAV-C may make the decision on whether or not to notify the altitude alarm. Also, if the altitude alarm condition is met, UAV-C may send an altitude alarm to the USS / UTM.

[0348] Embodiment 4. In the operation of a UAS, situations may arise in which a ground-based UE may be endangered. For example, if a UAV is present in the vicinity of a ground-based UE, changes in the surrounding environment may cause the UAV's altitude to drop rapidly, potentially causing the UAV to fall towards the UE and inflict damage on the UE, the person operating the UE, or the equipment on board the UE. A method is required to avoid such dangers to the UE.

[0349] The UAV may notify the UE of at least one of the UAV's altitude and altitude alarms.

[0350] In Embodiment 3, the UAV's altitude and altitude alarm are notified to the UAV-C or USS / UTM. In contrast, in this embodiment, the UAV notifies the UE on the ground of at least one of the UAV's altitude and altitude alarm.

[0351] The UAV transmits information about its altitude to the UE. Hereafter, this information may be referred to as altitude information. The UAV may transmit an altitude alarm to the UE. The UAV may transmit altitude information or an altitude alarm directly to the UE. PC5 may be used for transmission from the UAV to the UE. For example, the UAV may transmit altitude information or an altitude alarm to the UE using broadcast communication via PC5. The UAV may transmit altitude information or an altitude alarm to the UE using MBS (Multicast Broadcast Service) via PC5. The UE may be a UE in the vicinity of the UAV.

[0352] A UE may be one that supports a service related to the notification of altitude information or altitude alarms. A UAV may include information about the service in the altitude information or altitude alarm when broadcasting via PC5. For example, application information may include information about the service. The destination may be an L2 identifier (destination Layer-2 ID). The UAV broadcasts to the destination using the L2 identifier. The UE may receive the broadcast transmission from the UAV using the L2 identifier. The UAV may transmit information about altitude information or altitude alarms to the UE using broadcast communication. The UE receives altitude information or altitude alarms from the UAV. In this way, the UAV can directly notify the UE of altitude information or altitude alarms.

[0353] The UAV may transmit altitude information or altitude alarms to the UE via a RAN node. The RAN node may be, for example, a base station to which the UAV is connected. The UAV may transmit altitude information or altitude alarms to the UE via a CN node. The CN node may be, for example, an AMF or a UPF. If the UAV is not connected to a base station, it is advisable for the UAV to establish a connection with a base station before transmitting altitude information or altitude alarms. If the UAV transmits altitude information or altitude alarms via a CN node, it is advisable for the UAV to establish a connection with the CN node. Transmission of altitude information or altitude alarms may be performed using a CP or using a UP. If a UP is used, it is advisable for the UAV to establish a PDU session with the CN node.

[0354] As a method for a UAV to send altitude information or altitude alarms to a RAN node, for example, RRC signaling may be used. The RRC message may contain information about altitude information or altitude alarms. By using RRC messages, more information can be notified. For example, altitude information or altitude alarms may be sent using MAC signaling. For example, MAC CE may contain information about altitude information or altitude alarms. By using MAC signaling, altitude information or altitude alarms can be notified earlier. For example, UCI may contain information about altitude information or altitude alarms. The UCI may be sent via PUCCH. For example, altitude information or altitude alarms may be sent using SR. For example, altitude information or altitude alarms may be sent using RA (Random Access) processing. Altitude information or altitude alarms can be notified even earlier.

[0355] Alternatively, a measurement may be used as another method for a UAV to send altitude information or altitude alarms to a RAN node. For example, the RAN node sends a measurement configuration to the UAV. This configuration may include altitude measurement settings, altitude alarm settings, and altitude alarm condition settings. The UAV uses this configuration to decide whether to notify altitude information or an altitude alarm. The UAV sends a measurement report to the RAN node containing information about the altitude information or altitude alarm. The RAN node can then receive altitude information or an altitude alarm from the UAV. Using measurement can reduce the amount of signaling.

[0356] The UAV may transmit altitude information or altitude alarms to the RAN node in a manner separate from the measurement report. The RAN node may transmit altitude measurement settings and altitude alarm settings to the UAV. The UAV uses these settings to determine whether or not to notify altitude information and altitude alarms. The UAV transmits information regarding altitude information or altitude alarms to the RAN node. The RAN node can receive altitude information or altitude alarms from the UAV. By configuring this separately from the measurement, the altitude measurement or altitude alarm function can be flexibly configured to suit the surrounding environment.

[0357] The RAN node transmits altitude information or altitude alarms to the UE. The RAN node may notify the UE of altitude information or altitude alarms. The SIB may contain information regarding altitude information or altitude alarms. A new SIB may be established, and the SIB may contain information regarding altitude information or altitude alarms. The RAN node notifies the SIB. In this way, altitude information or altitude alarms can be notified to the UEs under the RAN node.

[0358] Paging may be used to transmit altitude information or altitude alarms. A RAN node may include information regarding altitude information or altitude alarms in the paging and transmit the paging to a UE. The UE receiving the paging can receive information regarding altitude information or altitude alarms. For example, a RAN node includes information indicating an altitude alarm in the paging and transmits the paging to a UE. The UE can receive the altitude alarm by receiving the paging.

[0359] A Public Warning System (PWS) function may be used to transmit altitude information or altitude alarms. The PWS paging may include information indicating that it is altitude information or an altitude alarm. This information may also include information indicating that information regarding altitude information or altitude alarms is transmitted in an SIB. The PWS SIB transmitted by a RAN node may include information regarding altitude information or altitude alarms. The UE receives the PWS paging using the PWS function. If the paging includes information indicating altitude information or an altitude alarm, the UE may receive the PWS SIB. The UE receives the SIB and receives information regarding altitude information or an altitude alarm. Although it has been disclosed that information regarding altitude information or an altitude alarm may be included in the PWS SIB, information regarding altitude information or an altitude alarm may also be included in another SIB. An SIB for altitude information or an altitude alarm may be provided. The UE may receive the SIB if the paging from a RAN node includes information indicating altitude information or an altitude alarm.

[0360] A RAN node may be a DU or a TRP. Altitude information or altitude alarms may be broadcast only from a specific DU or TRP. A CU may configure which DU or TRP broadcasts the information. In this way, altitude information or altitude alarms can be transmitted to UEs located around the broadcasting DU or TRP.

[0361] Figure 22 shows an example sequence of the process for notifying a UE of an altitude alarm. Steps common to Figure 21 are given the same step numbers, and common explanations are omitted. At ST2201, UAV1 performs PDU session establishment processing and C2 authorization processing for C2 communication between USS / UTM. In the C2 authorization processing for C2 communication, USS / UTM may send altitude measurement settings, altitude alarm requests, and altitude alarm settings to UAV1. The altitude alarm settings include setting altitude alarm conditions. USS / UTM may send an altitude alarm setting request to the RAN node. The altitude alarm setting request is a request for altitude alarm settings. In response to receiving the altitude alarm setting request, the RAN node may send the altitude alarm settings to UAV1. In the example in Figure 22, the RAN node is a base station. Some or all of the processing related to altitude alarm settings may be performed separately from the C2 authorization processing for C2 communication. In the example shown in Figure 22, these processes are performed in the C2 authorization process for C2 communication.

[0362] Upon receiving an altitude alarm setting request, the base station determines the altitude alarm setting in ST2203. The altitude alarm setting includes setting the altitude alarm conditions, as described above. In ST2205, the base station transmits the altitude alarm setting to the UAV1. In ST2112, the UAV1 performs altitude measurement processing. The altitude measurement may appropriately apply the method disclosed in Embodiment 3. In ST2113, the UAV1 determines whether or not to notify an altitude alarm. The UAV1 may use the altitude alarm setting obtained from the USS / UTM for this determination. In ST2113, the altitude alarm conditions are met. In this case, in ST2211, the UAV1 determines the destination L2 ID for PC5 broadcast communication. Application information may be used for the destination L2 ID. In ST2207, the UE1 determines the destination L2 ID for PC5 broadcast communication. Application information may be used for the destination L2 ID. Similarly, in ST2209, UE2 determines the destination L2 ID for PC5 broadcast communication. In ST2213, UAV1 transmits an altitude alarm using PC5 broadcast communication. UE1 and UE2 receive the altitude alarm transmitted using the broadcast communication. In ST2215, UAV1 may transmit an altitude alarm notification to the USS / UTM. The USS / UTM can receive the altitude alarm from UAV1.

[0363] In this way, UE1 and UE2 can receive altitude alarms from UAV1. By using PC5 broadcast communication, the UAV can directly notify the UEs of the altitude alarm. UEs located near the UAV can receive the altitude alarm early. For example, a UE that receives an altitude alarm due to a UAV falling may take action to avoid a collision with the falling UAV. This allows for avoidance of a collision with the falling UAV.

[0364] Figure 23 shows another example sequence of the process for notifying UEs of an altitude alarm. Steps common to Figures 21 and 22 are given the same step numbers, and common explanations are omitted. At ST2113, the altitude alarm condition is met. In this case, at ST2313, UAV1 transmits an altitude alarm to the base station. Upon receiving the altitude alarm, the base station, at ST2315, includes some or all of the information contained in the altitude alarm in an SIB for the altitude alarm and broadcasts the SIB. In this way, the base station can notify UEs under its control of the altitude alarm of UAV1.

[0365] In this way, the UE can receive UAV altitude alarms from the base station. For example, even a UE that does not support UAS services can receive UAV altitude alarms. The UE can, for example, avoid collisions with a falling UAV.

[0366] The UAV may transmit altitude information or altitude alarms to individual UEs. The UAV may transmit altitude information or altitude alarms to individual UEs via unicast communication using the PC 5. The UAV may perform discovery processing to detect predetermined UEs before performing unicast communication. In the unicast communication request message or discovery processing, the UAV may transmit service information relating to the notification of altitude information or altitude alarms. As disclosed above, the application information may include service information relating to the notification of altitude information or altitude alarms. In the unicast communication request message or discovery processing by the PC 5, the application information set in the service information may be set as the destination. UEs that support the service may communicate with the UAV via unicast using the destination included in the unicast communication request message or discovery processing. The UAV can transmit information relating to altitude information or altitude alarms to UEs that support the service individually using unicast communication.

[0367] The UAV may transmit altitude information or altitude alarms to a UE group. A UE group includes one or more UEs. The UAV may receive settings from a network node regarding the UE group to which it will notify altitude information or altitude alarms. The transmission methods to individual UEs disclosed above may be applied as appropriate. For example, the UAV may transmit altitude information or altitude alarms individually to UEs within a UE group. UEs within a UE group are configured with the same application information. The UAV may use the application information to identify UEs within a UE group. Transmission from the UAV to the UE group may be performed using PC5's groupcast communication. In this way, the UAV can transmit altitude information or altitude alarm information to UEs within a UE group.

[0368] The UAV may transmit altitude information or altitude alarms to individual UEs via RAN nodes. A method for deriving UEs near the UAV is disclosed. The NW node obtains information about the UAV's location. For example, a positioning function supported by 3GPP (see Non-Patent Document 25) may be used. For example, a UAV tracking function supported by 3GPP (see Non-Patent Document 30) may be used. The LMF or GMLC may obtain the UAV's location information. The UAV's positioning may be performed periodically, for example, and the UAV's location information may be updated.

[0369] The LMF or GMLC derives UEs located near the UAV using the UAV location information. The method for deriving UEs located near the UAV may be pre-configured. For example, the LMF or GMLC may consider UEs within a predetermined distance range from the UAV's location as UEs located near the UAV. Conditions for deriving UEs located near the UAV may be pre-configured. These conditions may be a predetermined distance range from the UAV. These conditions may be set by the source node of the altitude notification request or altitude alarm request. Alternatively, a RAN node may set these conditions. The node that has set these conditions should transmit the settings to the LMF or GMLC.

[0370] A request may be provided to notify a specific node of the location information of a UAV. Hereafter, this request may be referred to as a UAV location request. For example, a node sends a UAV location request to an LMF or GMLC. The node may send the UAV location request via other network nodes. The UAV location request may include, for example, information about a service, information about the UAV whose location information is to be acquired, information about the source node of the UAV location request, and information about the destination node of the UAV location request. For example, the LMF or GMLC that receives the UAV location request derives information about the location of the UAV. A response to a UAV location request may be provided. Hereafter, this response may be referred to as a UAV location application. For example, the LMF or GMLC sends a UAV location response to the source node of the UAV location request. The LMF or GMLC may send the UAV location response via other network nodes. The UAV location response may include, for example, at least one of the following: information about the service, information about the location of the requested UAV, information about the source node of the UAV location request, and information about the destination node of the UAV location request. The source node of the UAV location request can obtain the UAV's location information.

[0371] A request may be provided to notify a specific node of information about UEs located in the vicinity of the UAV. Hereafter, this request may be referred to as a neighboring UE information request. For example, a node sends a neighboring UE information request to an LMF or GMLC. The neighboring UE information request may include at least one of the following: information about the service, information about the UAV, information about the location of the UAV, a method for deriving UEs located in the vicinity of the UAV, the maximum number of UEs, information about the source node of the neighboring UE information request, and information about the destination node of the neighboring UE information request. The LMF or GMLC that receives the neighboring UE information request derives information about UEs located in the vicinity of the UAV. A response to the neighboring UE information request may be provided. Hereafter, this response may be referred to as a neighboring UE information response. For example, the LMF or GMLC sends a neighboring UE information response to the source node of the neighboring UE information request. The nearby UE information response may include, for example, at least one of the following: information about the service, information about the UAV, information about the location of the UAV, information about UEs located near the UAV, information about the locations of UEs located near the UAV, a method for deriving UEs located near the UAV, the number of UEs, information about the source node of the nearby UE information request, and information about the destination node of the nearby UE information request. The source node of the nearby UE information request can obtain information about UEs located near the UAV.

[0372] A UAV location request and a neighboring UE information request may be sent together. A request containing both types of information may be provided. A UAV location response and a neighboring UE information response may be sent together. A response containing both types of information may be provided.

[0373] For example, the UAV transmits altitude information or altitude alarm information to a base station. The base station obtains the UAV's location information and information about UEs located near the UAV in the manner disclosed above. Using the information about UEs located near the UAV, the base station transmits the UAV's altitude information or altitude alarm information individually to the UEs identified by that information. In this way, UEs located near the UAV can receive the UAV's altitude information or altitude alarm.

[0374] The method for transmitting altitude information or altitude alarm information from a UAV to a RAN node may be the method disclosed above, as appropriate. A RAN node may use RRC signaling as a method for transmitting altitude information or altitude alarms to individual UEs. RRC messages may include altitude information or altitude alarm information. Using RRC messages allows for the notification of more information. For example, MAC signaling may be used to transmit altitude information or altitude alarms. For example, a MAC CE may include altitude information or altitude alarm information. Using MAC signaling allows for earlier notification of altitude information or altitude alarms. For example, a DCI may include altitude information or altitude alarm information. The DCI may be transmitted via PDCCH. Altitude information or altitude alarms can be notified even earlier.

[0375] The LMF or GMLC may notify the AMF of information about UEs located near the UAV. The AMF derives one or more serving base stations for the UEs identified by the information. The AMF then notifies one or more of the derived base stations of information about UEs located near the UAVs served by those base stations. Each base station may use the information received from the AMF to individually transmit UAV altitude information or altitude alarms to the UEs identified by the information. This makes it possible to transmit UAV altitude information or altitude alarms to UEs connected to serving base stations different from the UAV.

[0376] Information regarding the altitude or altitude alarm of a UAV may be communicated between base stations. A base station may communicate this information to other base stations using an inter-base station interface (e.g., Xn). For example, the AMF transmits to one base station at least one of the following: information about a UE that is communicating the altitude or altitude alarm of a UAV, and information about the serving base station of that UE. The base station that receives this information may transmit it to the serving base station of the UE that is communicating the altitude or altitude alarm of a UAV. By communicating alarm information between base stations, the communication system can perform more flexible processing.

[0377] Figure 24 shows another example sequence of the altitude alarm notification process to the UE. Steps common to Figures 21 and 22 are given the same step numbers, and common explanations are omitted. In ST2401, UAV1 performs PDU session establishment processing and C2 authorization processing for C2 communication between USS / UTM. In the C2 authorization processing for C2 communication, USS / UTM may send altitude measurement settings, altitude alarm requests, and altitude alarm settings to UAV1. USS / UTM may send an altitude alarm setting request to the RAN node. The RAN node may send altitude alarm settings to the UAV in response to receiving the altitude alarm setting request. For example, the processing of ST2201 may be applied as appropriate. Also in ST2401, processing is performed to measure the position of UAV1. Hereafter, this processing may be referred to as the position measurement processing. For example, the method for acquiring the position of the UAV using the positioning function disclosed in Embodiment 1 may be applied as appropriate. For example, the processing in ST1905 (i.e., distance measurement processing and distance derivation processing) may be appropriately applied to measure the position of UAV1. For example, the distance derivation processing in ST1905 may be omitted, and the position may be derived by the positioning processing of UAV1. These processes may be performed separately.

[0378] At ST2113, the altitude alarm condition is met. In this case, at ST2313, UAV1 transmits an altitude alarm to the base station. Upon receiving the altitude alarm, the base station transmits a UAV position request regarding UAV1 and a nearby UE information request regarding UEs located near UAV1 to the AMF at ST2403. Upon receiving the request, the AMF may transmit the request to the LMF at ST2405. At ST2407, the LMF transmits the request to the GMLC. If the LMF has the position information of UAV1 and information regarding UEs located near UAV1, the LMF may derive this information and may not transmit the request to the GMLC. Processing from ST2407 to ST2411 can be omitted.

[0379] Upon receiving the request from the LMF, the GMLC uses ST2409 to derive information regarding the location of UAV1 and information regarding UEs located near UAV1. Having derived this information, the GMLC uses ST2411 to transmit a UAV location response and a nearby UE information response to the LMF. The UAV location response includes information regarding the location of UAV1. The nearby UE information response includes information regarding UEs located near UAV1. Using ST2413, the LMF transmits the UAV location response and the nearby UE information response to the AMF. Using ST2415, the AMF transmits the UAV location response and the nearby UE information response to the base station. The AMF may use the information regarding each UE to select a base station to connect to each UE. Using ST2415, the AMF transmits to the selected base station information regarding the UE to connect to that base station. In ST2417 and ST2419, the base station transmits altitude alarms individually to UEs (UE1 and UE2 in Figure 24) located near UAV1. UE1 and UE2, located near UAV1, are able to receive the altitude alarm for UAV1 from the base station.

[0380] In this way, a UE located near the UAV that issued the altitude alarm can receive the UAV's altitude alarm from the base station. The UE can, for example, avoid a collision with a falling UAV. Because the UEs that issue altitude alarms can be limited, the system can reduce the amount of signaling, the amount of radio resources used, and the noise.

[0381] The LMF or GMLC may, in advance, send the UAV's location information or information about UEs located near the UAV to the source node of the UAV location request or nearby UE information request. For example, the above information may be sent periodically. The above information may also be sent when the UAV's location information is updated. For example, the above information may be sent when the UAV is located in a predetermined location or area. The source node of the UAV location request or nearby UE information request can obtain the UAV's location information or information about UEs located near the UAV in advance. There is no need to perform the process of obtaining information about UEs near the UAV after a notification of UAV altitude information or an altitude alarm notification occurs. Therefore, it becomes possible to notify altitude information or altitude alarms at an earlier stage.

[0382] Figure 25 shows another example sequence of the altitude alarm notification process to the UE. Steps common to Figures 21, 22, and 24 are given the same step numbers, and common explanations are omitted. ST2401 performs the position measurement process for UAV1. The LMF / GMLC may update the position information of UAV1 and information about UEs located near UAV1 as appropriate. For example, the update of this information may be set during the position measurement process of UAV1. For example, UAV1 may set the above information update, or the USS / UTM may set the above information update and set it via the UAS NF / NEF. If the update setting is set during the position measurement process of UAV1, the LMF / GMLC updates the position information of UAV1 and information about UEs located near UAV1. This update may be performed periodically, for example, or when the information changes.

[0383] In ST2409, the GMLC may use the updated information to derive information about the location of UAV1 and information about UEs located near UAV1. In ST2411, the GMLC transmits the information about the location of UAV1 and information about UEs located near UAV1 to the LMF. In ST2413, the LMF transmits the above information to the AMF. In ST2415, the AMF transmits the above information to the base station. The processing from ST2409 to ST2415 may be performed when the location information of UAV1 or the information about UEs located near UAV1 is updated. In this way, the base station can obtain the updated information. The base station may record the updated information.

[0384] The processing of ST2409 to ST2415 may be carried out in parallel with the processing of ST2203, ST2205, ST2112, and ST2113.

[0385] The base station receives an altitude alarm notification from UAV1 using ST2313. In this case, the base station can immediately recognize information about UEs located near UAV1. ST2417 and ST2419 enable the base station to transmit an altitude alarm for UAV1 to UEs located near UAV1 (UE1 and UE2 in Figure 25) as early as possible.

[0386] In this way, a UE located near the UAV can receive an altitude alarm from the base station earlier, enabling the UE to respond more quickly.

[0387] A UE that receives an altitude alarm may notify its applications of the alarm. The applications of the UE can recognize the altitude alarm. A UE that receives an altitude alarm may also notify external parties of the alarm. For example, the alarm may be notified by sound, vibration, and / or a combination of two or more of these. For example, a person or object present externally can recognize the altitude alarm.

[0388] Altitude alarms may be notified by linguistic display and / or audio. When notified by linguistic display and / or audio, the notification may be in a pre-set language. As another example, the UE may acquire its own location information, use that location information to derive the country or region in which the UE is located, translate the altitude alarm into the language used in that country or region, and notify it. This is effective when the UAS operates across countries or regions.

[0389] According to the method disclosed in this embodiment, the UAV can notify the UE of the UAV's altitude information or altitude alarm. The UE, upon receiving altitude information or altitude alarm from the UAV, may notify the UE's onboard equipment or UE operator of the UAV's altitude information or altitude alarm. The UE may also notify the UE's onboard equipment or UE operator of location information. The UE's onboard equipment or UE operator can then take action to avoid a collision caused by the UAV falling. The UE's onboard equipment or UE operator can avoid the danger caused by the UAV falling. In the above example, the UAV or base station transmitted the altitude information or altitude alarm to the UE, but the system is not limited to this configuration. In the above-described embodiment 3, a configuration is also disclosed in which the UAV-C determines whether to notify an altitude alarm. Therefore, the UAV-C may transmit altitude information or altitude alarm to the UE.

[0390] Embodiments 3 and 4 disclose altitude alarms. Alternatively, an alarm using the switching judgment index disclosed in Embodiment 1 may be provided. For example, a remaining battery capacity alarm may be provided. The remaining battery capacity alarm is used to notify information indicating the situation when the remaining battery capacity of the UAV meets a predetermined condition. The predetermined condition may be, for example, the condition that the remaining battery capacity of the UAV falls below a predetermined value. The UAV measures the remaining battery capacity and notifies a remaining battery capacity alarm when the remaining battery capacity meets the alarm condition. The processing of the remaining battery capacity alarm may be appropriately applied using the method disclosed above. In this way, for example, UAV-C can recognize that the remaining battery capacity of the alarm target UAV is low. Control can be performed in accordance with the remaining battery capacity of the alarm target UAV.

[0391] Embodiment 5. Another situation in which a ground-based UE is endangered is, for example, when two UAVs collide in the airspace near the UE. The colliding UAV may fall and damage the UE. A method is required to avoid such dangers to the UE.

[0392] The UAV may notify the UE of distance information or distance alarms between UAVs.

[0393] The method disclosed in Embodiment 4 may be applied as appropriate. Embodiment 4 disclosed a method for notifying UAV altitude information or altitude alarms. The UAV altitude information or altitude alarms may be replaced with distance information or distance alarms between UAVs, and the method disclosed in Embodiment 4 may be applied as appropriate to the method for notifying the UE of the distance information or distance alarms between UAVs. The method for acquiring distance information between UAVs and the method for notifying distance alarms may be applied as appropriate to the method disclosed in Embodiment 2.

[0394] Figure 26 shows an example sequence of the distance alarm notification process to the UE. Steps common to Figures 19 and 22 are given the same step numbers, and common explanations are omitted. In ST2601, the USS / UTM sends a distance alarm request to UAV1. In ST1905, UAV1 performs a distance measurement process to measure the distance between UAV1 and each UAV (UAV2, ..., UAVn) and obtains the distance between UAV1 and each UAV. In ST2613, UAV1 decides whether to notify a distance alarm. In ST2613, the distance alarm condition is met. In this case, in ST2614, UAV1 sends a distance alarm to the UE (UE1 and UE2 in Figure 26) using PC5 broadcast communication. UE1 and UE2 receive the distance alarm sent using the broadcast communication. In ST2615, UAV1 may transmit a distance alarm to the USS / UTM. The USS / UTM can receive distance alarms regarding the distance between UAV1 and each UAV.

[0395] In this way, the UE can receive distance alarms regarding the distance between UAV1 and each other UAV. By using PC5 broadcast communication, distance alarms can be directly notified from the UAV to the UE. UEs located near the UAVs can receive distance alarms early. For example, when the distance between UAVs falls below a predetermined value, the UE receives a distance alarm. Upon receiving the distance alarm, the UE can recognize the possibility of a UAV collision. The UE may take evasive action. It can avoid collisions with UAVs that are falling due to collisions with other UAVs.

[0396] Figure 27 shows another example sequence of the distance alarm notification process to the UE. Steps common to Figures 19, 24, and 26 are given the same step numbers, and common explanations are omitted. ST1905 performs a distance measurement process to measure the distance between UAV1 and each UAV (UAV2, ..., UAVn). This distance measurement process may derive information about the position of UAV1 and information about UEs located near UAV1. This information is updated as appropriate. The processes from ST2409 to ST2415 are performed in response to updates to the position information of UAV1 or the information about UEs located near UAV1. ST2409 derives information about the position of UAV1 and information about UEs located near UAV1. ST2411 derives information about the position of UAV1 and information about UEs located near UAV1 to the LMF. In ST2413, the LMF transmits the above information to the AMF. In ST2415, the AMF transmits the above information to the base station. The processing of ST2409 to ST2415 may be performed in parallel with the processing of ST1905 and ST2613.

[0397] The base station receives a distance alarm notification from UAV1 using ST2701. In this case, the base station uses the information about UEs located near UAV1 obtained with ST2415 to transmit distance alarms to UEs located near UAV1 (UE1 and UE2 in Figure 27) using ST2703 and ST2705.

[0398] This allows UEs located near UAVs to receive distance alarms from base stations earlier, enabling them to respond more quickly.

[0399] A UE that receives a distance alarm may notify its application of the alarm. The application of the UE can recognize the distance alarm. A UE that receives a distance alarm may also notify an external party of the alarm. For example, the alarm may be notified by sound, vibration, and light, or a combination of two or more of these. For example, a person or object present externally can recognize the distance alarm.

[0400] Distance alarms may be notified by linguistic display and / or voice. When notified by linguistic display and / or voice, the notification may be in a pre-set language. As another example, a UE may acquire its own location information, use that location information to derive the country or region in which the UE is located, translate the distance alarm into the language used in that country or region, and notify it. This is effective when the UAS operates across countries or regions.

[0401] According to the method disclosed in this embodiment, a UAV can notify a UE of the distance between UAVs or a distance alarm. A UE that receives the distance or distance alarm from a UAV may notify its onboard equipment or UE operator of the distance or distance alarm between UAVs. The UE may also notify its onboard equipment or UE operator of location information. The onboard equipment or UE operator can recognize that a UAV is falling due to a collision between UAVs and take action to avoid a collision with the falling UAV. The onboard equipment or UE operator can avoid the danger caused by a falling UAV. In the above example, the UAV or base station transmitted the distance information or distance alarm to the UE, but the configuration is not limited to this. In the above-described embodiment 2, a configuration is also disclosed in which UAV-C determines whether to notify a distance alarm. Therefore, UAV-C may transmit the distance information or distance alarm to the UE.

[0402] Embodiments 2 and 5 disclose methods for notifying the distance between UAVs and distance alarms. Alternatively, the distance between a UAV and a UE and distance alarms may be notified. For example, the location of the UE or the distance between the UAV and the UE may be measured. The UE may be a reference UE. The UE may be a predetermined UE. The UE may be a fixed UE. For example, the UE may be a UE installed on a building (e.g., on the roof or wall), a UE installed on a mountain (e.g., on the mountaintop or mountainside), or a UE installed on a bridge. The method for notifying the distance between a UAV and a UE and distance alarms may be appropriately applied, for example, by applying the methods disclosed in Embodiments 2 and 5. For example, if a UAV-C receives a distance alarm between a UAV and a UE installed on a building, it can control the UAV to avoid the building. This can prevent a collision between the UAV and the building.

[0403] Embodiment 6. Support for UAS in mobile communication systems under 3GPP is being considered. Mobile communication systems that support UAS require the collection of data related to UAVs. For example, by using UAV data in SON (Self Organizing Network) or NW orchestration, it is possible to improve the resource utilization efficiency of the NW, including UAVs, or the robustness of mobility. On the other hand, MDT is a method for collecting measurement data of UEs (see Non-Patent Document 32). In 3GPP, it has been proposed to use MDT to record UAV direction, vibration, motion, and altitude-related events. However, current MDTs do not take UAVs into consideration. Furthermore, no specific method for collecting data from UAVs has been disclosed. This results in the problem that data related to UAVs cannot be collected.

[0404] This embodiment discloses a method for solving these problems.

[0405] A data collection function for UAVs is provided in the mobile communication system. The collected data may be data relating to a UAV that is connected to a base station, or data relating to a UAV that is not connected to a base station. A network node may measure data relating to a UAV, or a UAV or UAV-C may measure data relating to the UAV. A network node may collect data relating to a UAV, or a UAV or UAV-C may collect data relating to the UAV. A network node may be a RAN node, a CN node, a USS / UTM, a node with a management service or management function (management node), or another entity. For example, a network node may be a RAN node, a UAS NF / NEF, a NWDAF, or a TCE (Trace Control Entity).

[0406] Regarding the data to be collected, for example, the switching decision indicator disclosed in Embodiment 1 may be applied as appropriate.

[0407] The data to be collected may be changed based on the value of the switching decision index disclosed in Embodiment 1. For example, the data to be collected may be changed depending on the area where the UAV is located. In Area 1, communication quality and altitude may be collected, and in Area 2, QoS and altitude may be collected. As another example, the data to be collected may be changed depending on the altitude of the UAV. In altitude range A, communication quality and QoS may be collected, and in altitude range B, the distance between UAVs and remaining battery capacity may be collected.

[0408] The data collected may vary depending on the UAV's status. For example, if the UAV is in the RRC_Connected state, the serving cell's communication quality, QoS, and altitude may be collected. If the UAV is in the RRC_Inactive or RRC_Idle state, the neighboring cell's communication quality and altitude may be collected.

[0409] The data to be collected may be collected by measurement (which may be monitoring or sensing). Regarding the method of measuring the data, for example, the method for measuring the switching decision index disclosed in Embodiment 1 may be applied as appropriate. Hereafter, a node that measures the data to be collected may be referred to as a data measurement node. A node that collects the measured data may be referred to as a data collection node. A node that derives the data to be collected from the measurement results may be referred to as a data derivation node. The data measurement node may record the measured data. The data measurement node transmits the measured data to the data collection node. The data collection node may record the collected data. Alternatively, the data measurement node may perform the measurements necessary to derive the data to be collected and transmit the measurement results to the data derivation node. The data derivation node may use the measurement results to derive the data to be collected. The data derivation node may transmit the derived data to the data collection node. In this specification, the collected data and the measurement data obtained by the measurements necessary to derive the collected data may be collectively referred to as collected data. The data collection node may be, for example, a network node, USS / UTM, UAV-C, or management node. The data collection node may also be, for example, a node that performs data analysis. The data collection node may also be, for example, a node that has AI / ML functionality. The collected UAV-related data can be used to improve, for example, the resource utilization efficiency of the network including the UAV and the robustness of mobility.

[0410] A request may be made to cause a specific node to collect data. This request may be called a data collection request. The data collection request may include, for example, at least one of the following: information indicating the request for data to be collected, information about the data to be collected, settings for measuring the data to be collected, information about the node from which the data collection request is sent, and information about the node to which the data collection request is sent. The NW node sends a data collection request to a data measurement node. The data collection request may be sent before the data measurement node performs the measurement, or after the data measurement node performs the measurement. The data measurement node that receives the data collection request measures the requested data. The data measurement node sends the measured data to the data collection node. The data measurement node that receives a data collection request after measuring the data may send the measured data to the data collection node. The data collection node may make a data collection request. The data collection node may also be the node that makes the data collection request.

[0411] Settings for measuring data may be provided. Hereafter, these settings may be referred to as data measurement settings. A data measurement setting may include, for example, at least one of the following: data measurement target, data measurement method, method for recording data measurement results, and method for reporting data measurement results. The method for recording data measurement results may include at least one of periodic recording, non-periodic recording, and recording when a predetermined condition is met. It is preferable to record the data measurement results using this method. Multiple data measurement settings may be set. In another example, one data measurement setting may include at least one of multiple data measurement targets, multiple data measurement methods, multiple methods for recording data measurement results, and multiple methods for reporting data measurement results. A data measurement setting may appropriately apply, for example, the measurement settings for the switching decision indicator disclosed in Embodiment 1 (i.e., indicator measurement settings).

[0412] The number of data points to record measurement results may be limited. For example, a maximum number of cells to record measurement results may be set. This avoids an increase in recording capacity. The data to be recorded may be ranked. For example, data with good communication quality may be ranked first. In this specification, ranking may be rephrased as prioritization. For example, each collected data may be ranked. For example, if the data to be collected is changed based on the value of the switching judgment index disclosed in Embodiment 1, each such data may be ranked. For example, if data is measured for each altitude, the data may be ranked for each altitude. For example, if data is measured for each altitude range, the data may be ranked for each altitude range. It is advisable to record the measurement results starting with the highest-ranked data. For example, applying ranking when the number of data points is limited allows important measurement data to be recorded.

[0413] The methods for limiting or ranking the number of data points disclosed above may be applied as appropriate to the reporting of measurement results. Important measurement data can be reported.

[0414] A data collection response may be provided. The data collection response may include, for example, at least one of the following: information indicating a response to a data collection request, information about the corresponding data collection request, measurement data, data measurement settings, information about the source node of the data collection response, and information about the destination node of the data collection response. The data measurement node may include the measured data in the data collection response and send the data collection response to the data collection node.

[0415] In this way, the data collection node can collect measurement data from the data measurement node.

[0416] A method for collecting data from a UAV that is not connected to a base station is disclosed. In this example, the UAV is a data measurement node. The UAV measures data when it is not connected to a base station. The UAV records the measured data. After transitioning to a connected state, the UAV transmits the measured data to the data collection node. The UAV may perform a connection establishment process in order to transmit the measured data to the data collection node. The UAV transmits the measured data to the data collection node after establishing a connection. The UAV may transmit the measured data to the data collection node during the connection establishment process. The UAV may transmit the measured data to the data collection node when it transitions to a connected state through any process other than the connection establishment process.

[0417] The data collection node may send a data collection request when the UAV is connected. Upon receiving the data collection request, the UAV measures the data. The UAV may also measure the data when the connection is released. The data collection request may include information about the connection status at the time the UAV measures the data. In this way, a UAV that is not connected to a base station can collect data.

[0418] UAVs may support Logged MDT. Data about the UAV may be collected using Logged MDT. It is preferable for the UAV to support Logged MDT. The base station sends a data measurement configuration to the UAV. This transmission occurs when the UAV is connected. RRC signaling may be used to send the data measurement configuration. The RRC signaling may be a LoggedMeasurementConfiguration message. The Logged Measurement Configuration may be used as a data collection request. Upon receiving the Logged Measurement Configuration, the UAV uses the Logged Measurement Configuration to measure and collect data.

[0419] Regarding log measurement settings, the data measurement setting method disclosed above should be applied as appropriate. The log measurement settings may include at least one of the following: information about the data to be measured, information about the measurement method, information about the method of recording the measurement results, and information about the method of reporting the measurement results. The data to be measured may include at least one of the following, for example, measurement time, communication quality for each cell at the time of measurement, UAV location, UAV altitude, power consumption, and remaining battery capacity. Information about the measurement method may indicate, for example, that measurements are taken periodically. Information about the method of recording the measurement results may indicate, for example, that recording occurs when the UAV altitude is within a predetermined range and the cell communication quality is greater than a predetermined value. Information about the method of reporting the measurement results may indicate, for example, that reporting occurs when the UAV becomes connected. In this way, flexible log measurement suitable for UAVs becomes possible.

[0420] The base station sends a data collection request to the UAV. This data collection request is sent when the UAV is connected. RRC signaling may be used to send the data collection request. The RRC signaling may be a UE Information Request message. Upon receiving the request, the UAV sends the data measurement results to the base station. RRC signaling may be used to send the data measurement results. The RRC signaling may be a UE Information Response message. Upon receiving this message from the UAV, the base station can obtain the data measurement results from the UAV.

[0421] Figure 28 shows an example sequence for collecting UAV-related data using Log MDT. The UAV collects UAV-related data while the UAV is not connected to the base station. Figure 28 discloses an example in which a UAV in the RRC_Idle or RRC_Inactive state collects UAV-related data. At ST2801, the UAV is in the RRC_Connected state. At ST2803, the UAS NF / NEF sends an MDT activation message to the base station. The UAS NF / NEF sends a data collection request to the base station. These transmissions may be made via other nodes. The information included in the data collection request may be included in the MDT activation message. At ST2805, the base station sends an MDT setup message to the UAV. The base station sends a data collection request to the UAV. The data collection request includes data measurement settings. The information included in the data collection request may also be included in the MDT configuration message. RRC signaling for MDT configuration may be used for transmission from the base station to the UAV. This eliminates the need to set up new signaling and avoids an increase in the amount of signaling.

[0422] In ST2807, the RRC connection release process is performed between the UAV and the base station. As a result, in ST2811, the UAV enters the RRC_Idle or RRC_Inactive state. In ST2813, the UAV measures UAV-related data. The UAV may measure UAV-related data using, for example, the data measurement settings included in the MDT settings received in ST2805. In ST2815, the UAV records the measured data. The UAV may repeatedly measure UAV-related data. The UAV records the measurement results.

[0423] In ST2817, the RRC connection establishment process is performed between the UAV and the base station. As a result, in ST2819, the UAV enters the RRC_Connected state. In ST2821, the UAV sends an MDT report message to the base station. The UAV sends a data collection response to the base station. The information contained in the data collection response may also be included in the MDT report message. RRC signaling for MDT reporting may be used for transmission from the UAV to the base station. This eliminates the need to set up new signaling and avoids an increase in the amount of signaling.

[0424] In this way, the base station can collect UAV-related data measured by the UAV. ST2823 allows the base station to record the collected data.

[0425] In ST2825, the base station sends a data collection response to the UAS NF / NEF. In this way, the UAS NF / NEF can collect UAV-related data. In ST2827, the base station may send the collected UAV-related data to the TCE. The TCE receives the UAV-related data. The TCE can then use the UAV-related data in its tracing function.

[0426] In this way, the base station, UAS NF / NEF, and TCE can collect UAV-related data measured by UAVs that are not connected to the base station.

[0427] This document discloses a method for collecting data from a connected UAV. The UAV measures data while connected. The UAV records the measured data. The UAV transmits the measured data to a data acquisition node while connected.

[0428] A data acquisition node may send a data acquisition request when a UAV is connected. Upon receiving the data acquisition request, the UAV measures the data. The data acquisition request may include information about the connection status of the UAV when it measures the data. In this way, a connected UAV can collect data.

[0429] UAVs may support Immediate MDT. Data about the UAV may be collected using Immediate MDT. The UAV may support Immediate MDT. The base station transmits data measurement settings to the UAV. This transmission occurs when the UAV is connected. RRC signaling may be used to transmit the data measurement settings. RRC signaling may be an RRC Reconfiguration message. The data measurement settings may be included in the measurement settings of the message. The data measurement settings may be used as a data collection request. Upon receiving the data measurement settings, the UAV uses the settings to measure and collect data.

[0430] Regarding data measurement settings, the data measurement setting method disclosed above should be applied as appropriate. The data measurement settings may include at least one of the following: information about the data to be measured, information about the measurement method, information about the method of recording the measurement results, and information about the method of reporting the measurement results. The data to be measured may include at least one of the following, for example, measurement time, communication quality for each cell at the time of measurement, UAV location, UAV altitude, power consumption, and remaining battery capacity. Information about the measurement method may indicate, for example, that measurements are taken periodically. Information about the method of recording the measurement results may indicate, for example, that recording is performed when the UAV altitude is within a predetermined range and the cell communication quality is greater than a predetermined value. Information about the method of reporting the measurement results may indicate, for example, periodic reporting or trigger-based reporting. In this way, flexible data measurement suitable for UAVs becomes possible.

[0431] Existing measurement settings may be used as trigger-based settings. For example, trigger conditions of existing measurement settings may be used. For example, trigger conditions including communication quality and altitude may be used. For example, trigger conditions may be Ax, Hy and AxHy, as disclosed in Non-Patent Literature 19. Here, x and y correspond to the numbers disclosed in Non-Patent Literature 19, respectively. By using trigger conditions of existing measurement settings, the complexity of the measurement setting process can be avoided.

[0432] The UAV transmits measurement data to the base station using a configured measurement result reporting method. RRC signaling may be used for this transmission. The RRC signaling may be a MeasurementReport message. Upon receiving this message from the UAV, the base station can obtain the data measurement results from the UAV.

[0433] The base station may send a data collection request to the UAV. This transmission occurs when the UAV is connected. RRC signaling may be used to send the data collection request. The RRC signaling may be a UE Information Request message. Upon receiving the request, the UAV sends the data measurement results to the base station. RRC signaling may be used to send the data measurement results. The RRC signaling may be a UE Information Response message. Upon receiving this message from the UAV, the base station can obtain the data measurement results from the UAV.

[0434] Figure 29 shows an example sequence for collecting UAV-related data using immediate MDT. Steps common to Figure 28 are given the same step numbers, and common explanations are omitted. UAV-related data is collected while the UAV is connected. Figure 29 discloses an example in which a UAV in the RRC_Connected state collects UAV-related data. In ST2901, the UAV in the RRC_Connected state measures the UAV-related data. The UAV may measure the UAV-related data using, for example, the data measurement settings included in the MDT settings received in ST2805. The data measurement settings may be included in existing measurement settings. For example, the data measurement settings may be included in MeasConfig, which is existing RRC information. Existing measurement settings may be used for the data measurement settings. For example, MeasConfig, which is existing RRC information, may be used as settings for measuring UAV-related data.

[0435] In ST2903, the UAV sends an MDT report message to the base station. The UAV sends a data acquisition response to the base station. For example, the UAV may include the data acquisition response in an existing RRC information, such as a MeasurementReport, and send the MeasurementReport. This simplifies the process of collecting UAV-related data using immediate MDT. In this way, the base station can collect UAV-related data measured by the UAV. In ST2823, the base station may record the collected data.

[0436] In this way, the base station, UAS NF / NEF, and TCE can collect UAV-related data measured by the connected UAV.

[0437] As disclosed above, the indicator measurement settings disclosed in Embodiment 1 may be applied as appropriate to the data measurement settings. For example, data collection may be performed at a predetermined location, a predetermined area, or a predetermined altitude. Data measurement may be performed at a predetermined location, a predetermined area, or a predetermined altitude. Conditions for measuring data (hereinafter referred to as data measurement conditions) may be set. As data measurement conditions, any one of the predetermined location, a predetermined area, and a predetermined altitude, or a combination of two or more of these, may be set. The measurement data may be recorded in association with at least one of the location information, area information, altitude information, and measurement time information at the time of measurement.

[0438] For example, a predetermined flight path may be set. For example, a UAV may have its flight path set during the C2 authorization process. For example, a flight path may be set for a UAV in the data measurement settings. For example, data measurement may be performed along a predetermined flight path. For example, data measurement may be performed at waypoints along the flight path. The measurement data may be recorded in association with at least one of the following: location information, area information, altitude information, and measurement time information. The source node of the data collection request or the node that sets up the data measurement may set the flight path or waypoints on which data measurement will be performed. For example, the source node of the data collection request or the node that sets up the data measurement can collect measurement data for the waypoints on which data collection is desired.

[0439] Flight path information used in a UAS system may be used. For example, a UAV may perform measurements using waypoint information from flight path information used in a UAS system.

[0440] Alternatively, data may be measured at predetermined intervals along the flight path. The measurement data may be recorded in association with at least one of the following: location information, area information, altitude information, and measurement time information.

[0441] A predetermined flight path may be used as the data measurement condition for MDT. This allows for setting data measurement along the flight path in MDT. For example, it becomes possible to collect data along the flight path required for UAV operation.

[0442] 3GPP supports a reporting function for UAVs along their flight paths (see Non-Patent Document 2). The base station transmits measurement settings along the flight path to the UAV, and the UAV transmits location and time information of waypoints to the base station. RRC signaling is used for this transmission. Data collection may be performed using the UAV's reporting function along its flight path. For example, data measurement settings may be set using the measurement settings along the flight path. For example, the measurement settings along the flight path may include the data information to be measured as disclosed above. For example, this data may be measured at waypoints. For example, the UAV may transmit measurement data using the reporting function along its flight path. In this way, the data collection process can be simplified.

[0443] Information may be provided indicating that the UAV has data collection capabilities. Information may also be provided indicating that the UAV has MDT capabilities. The UAV's MDT capabilities may be log MDT or real-time MDT. The information may also be information indicating whether the UAV has the above capabilities (i.e., data collection capabilities and / or MDT capabilities). For example, the data collection capabilities may include at least one of the following regarding the UAV: ​​what data it has the capability to measure, the maximum number of data points, the maximum altitude at which data is measured, the minimum altitude at which data is measured, and the altitude range at which data is measured. The information may be included in the UE capabilities. The information may be transmitted from the UAV to a network node, a USS / UTM, a node that sends a data collection request, or a node that sets the data measurement settings. For example, the information may be transmitted from the UAV to a base station. The base station can recognize the capabilities that the UAV has. For example, a base station that sets data measurement settings for a UAV can set data measurement settings that can be measured by the UAV.

[0444] Other examples of data collected on UAVs are disclosed. Such data may include at least one of (e1) to (e9) below. These data may be used in combination with the data collected on UAVs disclosed above.

[0445] (e1) Information about RLF. (e2) Information about RA processing failure. (e3) Information about successful RA processing. (e4) Information about HO processing failure. (e5) Information about successful HO processing. (e6) Information about RRC connection establishment processing failure. (e7) Information about successful RRC connection establishment processing. (e8) Information about DC-related processing failure. (e9) Information about successful DC-related processing.

[0446] The aforementioned (e1) information about RLF may include, for example, at least one of the number, frequency, probability of RLF, information about the link where RLF occurred, information about the cell where RLF occurred, and information about the opposing UAV where RLF occurred (for example, when the link is PC5).

[0447] The aforementioned (e2) information about RA processing failure may include, for example, at least one of the number, frequency, probability of RA processing failure / success, information about the cell where RA processing was performed, information about the resources used in RA processing, and information about the SSB received for RA processing.

[0448] The (e3) information about successful RA processing may include, for example, at least one of the number, frequency, probability of RA processing failure / success, information about the cell where RA processing was performed, information about the resources used in RA processing, and information about the SSB received for RA processing.

[0449] The aforementioned (e4) information about HO processing failure may include, for example, at least one of the number, frequency, probability of HO processing failure / success, information about the HO source cell, information about the HO target cell, information about the candidate cells for CHO (Conditional Handover), information about the communication quality with the cell, and information about the measurement event.

[0450] Information regarding the success of the HO process may include, for example, at least one of the number of HO process failures / successes, the frequency of HO process failures / successes, the probability of HO process failures / successes, information regarding the source cell of the HO, information regarding the target cell of the HO, information regarding candidate cells for CHO, information regarding the communication quality with cells, and information regarding measurement events.

[0451] The aforementioned information regarding the failure of the (e6) RRC connection establishment process may include, for example, at least one of the number of failures / successes of the RRC connection establishment process, the frequency of failures / successes of the RRC connection establishment process, the probability of failures / successes of the RRC connection establishment process, information regarding the cell where the RRC connection establishment was performed, information regarding the frequency, and information regarding the communication quality with cells.

[0452] Information regarding the success of the (e7) RRC connection establishment process may be, for example, the number of failures / successes of the RRC connection establishment process, the frequency of failures / successes of the RRC connection establishment process, the probability of failures / successes of the RRC connection establishment process, information regarding the cell where the RRC connection establishment was performed, information regarding the frequency, information regarding the communication quality with cells, etc.

[0453] The information regarding DC in the aforementioned (e8) and (e9) may be, for example, information regarding the process related to multi-connectivity (see Non-Patent Document 22). For example, the process related to multi-connectivity may be a process related to EN-DC or a process related to MR-DC. The process may be, for example, Secondary Node Addition, PSCell change, etc.

[0454] Information regarding the failure of the process related to (e8) DC may include, for example, at least one of the number of DC process failures / successes, the frequency of DC process failures / successes, the probability of DC process failures / successes, information regarding the target base station for addition, information regarding the source base station for change, information regarding the target base station for change, information regarding candidate cells for CPC (Conditional PScell Change) / CPA (Conditional PScell Addition), information regarding the communication quality with cells, and information regarding measurement events.

[0455] (e9) Information relating to DC processing success may include, for example, at least one of the following: the number of DC processing failures / successes, the frequency of DC processing failures / successes, the probability of DC processing failures / successes, information relating to the base station to be added, information relating to the source base station, information relating to the destination base station, information relating to candidate cells for CPC (Conditional PScell ​​Change) / CPA (Conditional PScell ​​Addition), information relating to the quality of communication with the cell, and information relating to measurement events.

[0456] Information about what data to derive, or what information to derive, may be included in the data measurement settings. Examples of data combined with the aforementioned data include the number of RLFs in a given altitude range, the number of RA processing failures, the HO processing failure probability, and the RRC connection establishment processing failure probability.

[0457] These data may be derived by a UAV or by a RAN node. The UAV or RAN node that derived these data may then transmit the derived results to the data collection node.

[0458] In this way, data on RLF, RA processing, HO processing, RRC connection establishment processing, or multi-connectivity processing generated by the UAV can be collected. This makes it possible to use a wider variety of data, enabling the provision of a higher-performance system as a mobile communication system supporting UAS.

[0459] An AI (Artificial Intelligence) / ML (Machine Learning) that performs predictive processing related to UAS may be configured in the mobile communication system. The input information to the AI / ML may be, for example, the collected data related to UAV disclosed above. For example, a source node of a data collection request that has collected data related to UAV may transmit the data to a node that has the function of performing learning or prediction by AI / ML. The node with the AI / ML function may perform learning or prediction using the data.

[0460] The AI / ML output information may be prediction results. For example, the AI / ML output information may be prediction results of the aforementioned UAV-related collected data, including the switching decision index disclosed in Embodiment 1. For example, the AI / ML output information may be the communication quality of a predetermined area. For example, the AI / ML output information may be prediction results of QoS or QoS for a predetermined area. For example, the AI / ML output information may be the RLF probability for a predetermined altitude range. For example, the AI / ML output information may be at least one of the prediction results of the communication quality with a cell in a predetermined altitude range and the prediction results of the RLF probability in that cell. For example, the selected or re-selected cell at a predetermined altitude and the success probability of the RRC connection establishment process to that cell may be predicted. For example, the HO destination cell at a predetermined altitude and the success probability of the HO process to that cell may be predicted. For example, the CHO destination candidate cell at a predetermined altitude and the success probability of the HO process to that candidate cell may be predicted.

[0461] The output information from AI / ML may be the prediction result of an alarm. For example, the output information from AI / ML may be the prediction result of a distance alarm as disclosed in Embodiments 2 to 5, or it may be the prediction result of an altitude alarm. The alarm prediction result may include, for example, at least one of the following: alarm type, alarm altitude, alarm time, alarm location, information about the UAV that triggered the alarm, and information about the UE that triggered the alarm. In this way, the occurrence of an alarm can be predicted early, before the alarm notification conditions are actually met.

[0462] Other output information from AI / ML may include, for example, a prediction result of a UAV entering an exclusion zone, or a prediction result of a UAV entering a NTZ. An alarm for entering an exclusion zone or an alarm for entering an NTZ may be provided. The alarm processing disclosed in Embodiments 2 to 5 may be applied as appropriate. The alarm notification determination condition may be that the prediction result satisfies a predetermined condition. For example, an alarm notification may be determined when the prediction result indicates that the UAV will enter an exclusion zone within a predetermined time, or that the UAV will enter an NTZ within a predetermined time. For example, a UAV-C that receives an exclusion zone entry alarm or an NTZ entry alarm can perform control to prevent the UAV from entering an exclusion zone or entering an NTZ.

[0463] A node with AI / ML functionality transmits output information to a node that will use the information. The node with AI / ML functionality may also transmit output information to a node that requested the information. A node that requests the information may request it from a node with AI / ML functionality. A node that uses the information may be, for example, a USS / UTM, a network node, a RAN node, a UAV, or a UAV-C. The information may also be transmitted to an application, or to an AF via the NEF.

[0464] For example, if a node with AI / ML functionality predicts an alarm, it may notify the UAV of the alarm prediction result. The UAV may then notify UAV-C or a nearby UAV of the alarm prediction result using the method disclosed above. This allows UAV-C or UE to take evasive action earlier.

[0465] Multiple flight paths may be configured. Some or all of these flight paths may be different. The UAV may be notified of information indicating which flight path will be used. Other output information from AI / ML may include, for example, information about the flight path. This output information may include, for example, the expected communication quality, QoS, or QoS for the flight path. This output information may also include a more suitable flight path derived from the expected communication quality, QoS, or QoS for the flight path. One more suitable flight path may be provided, or multiple more suitable flight paths may be provided. This output information may also include a request to change to a more suitable flight path. A node with AI / ML functionality transmits this output information to a node that will use the information. For example, a node with AI / ML functionality transmits a flight path change request to a USS / UTM, UAV, or UAV-C. The USS / UTM, upon receiving the request, may transmit the request to the UAV or UAV-C. The request may include at least one of the following: information indicating which flight path to take, the location of the flight path change, the time of the flight path change, the communication quality, QoS or QoS before the flight path change, and the communication quality, QoS or QoS after the flight path change. The USS / UTM, UAV, or UAV-C may change its flight path using the information on the more suitable flight path included in the request. In this way, the UAV can appropriately adopt a more suitable flight path depending on the surrounding environment and radio wave propagation environment.

[0466] The method disclosed in this embodiment enables the collection of data related to UAVs in a mobile communication system. For example, data can be collected from UAVs using the MDT function. By collecting data related to UAVs, it becomes possible to perform, for example, SON or NW orchestration including UAVs. This improves the resource utilization efficiency of the NW including UAVs and the robustness of mobility.

[0467] In this specification, a UE mounted on a UAV may be referred to as a UAV. Similarly, a UE mounted on a UAV-C may be referred to as a UAV-C.

[0468] Although UAVs have been disclosed in this specification, the embodiments described above are not limited to UAVs; they may also apply to UEs mounted on manned aircraft or to UEs existing in the air.

[0469] In this specification, UE, UAV, and UAV-C may be referred to as nodes. Furthermore, network elements that communicate with UE, UAV, and UAV-C may also be referred to as nodes. For example, a base station that communicates with UE, UAV, and UAV-C may be referred to as a node (RAN node, NW node, etc.). Furthermore, in this specification, a node may also be a function.

[0470] In this specification, elements in a UAS system may be referred to as nodes. For example, elements such as USS / UTM may be referred to as nodes.

[0471] In the communication system relating to this disclosure, one or more cells are configured in a single gNB. In this disclosure, the terms gNB and cell are used, but unless otherwise specified, they may refer to either a gNB or a cell.

[0472] In this disclosure, gNB may be MCG or SCG.

[0473] In the above embodiment, an expression using the symbol slash ( / ) may be interpreted as an expression that includes at least one of the two elements before and after the slash.

[0474] The embodiments and their variations described above are merely illustrative, and these embodiments and their variations can be freely combined. Furthermore, any component of each embodiment and its variations can be modified or omitted as appropriate.

[0475] For example, in the embodiments and their modifications described above, a slot is an example of a time unit for communication in a fifth-generation communication system. A slot may also be a scheduling unit. The scheduling units described in the embodiments and their modifications described above may be TTI units, subframe units, slot units, subslot units, minislot units, or symbol units.

[0476] For example, the methods disclosed in each of the embodiments and their modifications described above may be applied to an IAB. They may be applied to communication between an IAB donor and an IAB node. They may be applied to processing that uses Uu in an IAB.

[0477] 202 Communication terminal equipment (mobile terminal), 210 Communication system, 213, 240-1, 240-2, 750 Base station equipment (NR base station, base station), 214 5G core unit, 215 Central unit, 216 Distributed unit, 217 Central unit for control plane, 218 Central unit for user plane, 219 TRP, 301, 403 Protocol processing unit, 302 Application unit, 304, 405 Encoder unit, 305, 406 Modulation unit, 306, 407 Frequency conversion unit, 307-1 to 307-4, 408-1 to 408-4 Antenna, 308, 409 Demodulation unit, 309, 410 Decoder unit, 310, 411, 526 Control unit, 401 EPC communication unit, 402 Other base station communication unit, 412 5GC communication unit, 521 Data Network communication unit, 522 Base station communication unit, 523 User plane communication unit, 523-1 PDU processing unit, 523-2 Mobility anchoring unit, 525 Control plane control unit, 525-1 NAS security unit, 525-2 Idle state mobility management unit, 527 Session management unit, 527-1 PDU session control unit, 527-2 UE IP address assignment unit, 751-1 to 751-8 Beams, 752 Cells.

Claims

1. A communication system comprising: at least one uncrewed aerial vehicle (UAV); a UAV controller (UAV-C) that controls the at least one UAV; and a network including at least one network node that communicates with the at least one UAV and the UAV-C, wherein the UAV and the UAV-C are configured to perform a first communication in which the UAV and the UAV-C are directly connected to each other to perform command and control (C2) communication; and a second communication in which the UAV and the UAV-C are connected via the network to perform C2 communication; and the UAV, the UAV-C, or the network node is configured to determine whether to switch between the first communication and the second communication using a switching decision index.

2. The communication system according to claim 1, wherein the UAV measures the switching decision index, determines whether to switch between the first communication and the second communication using the measured switching decision index, and the UAV transmits a switching request to the UAV-C and the network node.

3. The communication system according to claim 2, wherein the UAV is configured to perform an authorization process that combines the C2 authorization process for the first communication and the C2 authorization process for the second communication before deciding to switch between the first communication and the second communication.

4. The communication system according to claim 2, wherein the UAV is configured to perform C2 authorization processing for the first communication and C2 authorization processing for the second communication separately before determining whether to switch between the first communication and the second communication.

5. The communication system according to claim 1, wherein the UAV is configured to measure the switching decision index and transmit the measurement result of the switching decision index to the network node, and the network node is configured to use the switching decision index to determine whether to switch between the first communication and the second communication and to transmit a switching request to the UAV.

6. The communication system according to any one of claims 1 to 5, wherein the switching decision indicator includes at least one of the following: communication quality, QoS (Quality of Service), QoS (Quality of Experience), PRACH (Physical Random Access Channel) information, location, area, altitude, distance, power consumption, remaining battery capacity, power consumption, time, cell, beam, sensing data, number of UAVs, speed of the UAVs, acceleration of the UAVs, and direction of movement of the UAVs.

7. The communication system according to any one of claims 1 to 6, wherein the at least one UAV includes at least a first UAV and a second UAV, and the first UAV is configured to measure the distance between the first UAV and the second UAV and to transmit information relating to the distance to the UAV-C or the network node.

8. The communication system according to claim 7, wherein the first UAV is configured to use the distance information to determine whether the conditions for a distance alarm are met, and if the conditions are met, transmit the distance alarm to the UAV-C or the network node.

9. The communication system according to any one of claims 1 to 6, wherein the at least one UAV includes at least a first UAV and a second UAV, the at least one network node includes a first network node and a second network node, the first network node is configured to acquire information relating to the distance between the first UAV and the second UAV, to use the distance information to determine whether conditions relating to a distance alarm are met, and, if the conditions are met, to transmit the distance alarm to the second network node.

10. The communication system according to any one of claims 1 to 9, wherein the UAV is configured to measure altitude, use the information relating to altitude to determine whether conditions relating to an altitude alarm are met, and, if the conditions are met, transmit the altitude alarm to the UAV-C or the network node.

11. The communication system according to claim 10, further comprising a communication terminal device, wherein the UAV is configured to transmit the altitude alarm to the communication terminal device located near the UAV.

12. The communication system according to claim 11, wherein the UAV is configured to transmit the altitude alarm to the communication terminal device located near the UAV via the network node.

13. The communication system according to claim 10, further comprising a communication terminal device, wherein the at least one network node comprises a first network node and a second network node, the first network node being a base station, the UAV transmitting the altitude alarm to the base station, and the base station being configured to receive from the second network node information relating to the location of the UAV and information relating to the communication terminal device located near the UAV, and to transmit the altitude alarm to the communication terminal device located near the UAV.

14. The communication system according to any one of claims 1 to 13, further comprising a communication terminal device, wherein the at least one UAV comprises at least a first UAV and a second UAV, the first UAV is configured to measure the distance between the first UAV and the second UAV, to use the information relating to the distance to determine whether conditions relating to a distance alarm are met, and, if the conditions are met, to transmit the distance alarm to the communication terminal device located near the first UAV.

15. The communication system according to claim 14, wherein the first UAV is configured to transmit the distance alarm to the communication terminal device located near the first UAV via the network node.

16. The communication system according to any one of claims 1 to 15, wherein the at least one network node includes a base station, and the UAV is configured to measure information related to the UAV when the UAV is in the RRC (Radio Resource Control)_Idle or RRC_Inactive state with respect to the base station, and transmit the information related to the UAV to the base station after the UAV has transitioned to the RRC_Connected state with respect to the base station.

17. The communication system according to claim 16, wherein when the UAV is in the RRC_Connected state with respect to the base station, the system is configured to measure information related to the UAV and to transmit the information related to the UAV to the base station.

Images