Communication method, aerial user device, and network node

Abstract

This communication method which is to be executed by an aerial user device in a mobile communication system involves: receiving access restriction information that was broadcasted from a restricted cell to which access by the aerial user device is restricted and that is used exclusively for the aerial user device; and, in a radio resource control (RRC) idle state or a RRC inactive state, refraining from accessing the restricted cell on the basis of the access restriction information.

Description

Communication Method, Aerial User Equipment, and Network Node

[0001] The present disclosure relates to a communication method, an aerial user equipment, and a network node used in a mobile communication system.

[0002] In 3GPP (3rd Generation Partnership Project) (registered trademark; the same shall apply hereinafter), the technical specifications of NR (New Radio), which is a 5th generation (5G) radio access technology, are defined. The 3GPP mobile communication system supports an aerial UE (Aerial User Equipment), which is a user equipment (UE) capable of aerial communication. The aerial user equipment may be an Unmanned Aircraft Vehicle (UAV) such as a drone.

[0003] 3GPP Technical Specification "3GPP TS 38.300 V18.2.0 (2024-06)"

[0004] The present disclosure provides a technology that enables appropriate handling of scenarios where, for example, a transmission prohibited area (NTZ: No-Transmit Zone) is provided.

[0005] The communication method according to the first aspect of the present disclosure is a communication method executed by an aerial user equipment in a mobile communication system, including receiving access restriction information broadcast from a restricted cell where access of the aerial user equipment is restricted and dedicated to the aerial user equipment, and refraining from accessing the restricted cell based on the access restriction information in a radio resource control (RRC) idle state or an RRC inactive state.

[0006] The aerial user equipment according to the second aspect of the present disclosure is an aerial user equipment used in a mobile communication system, including a receiving unit that receives access restriction information broadcast from a restricted cell where access of the aerial user equipment is restricted and dedicated to the aerial user equipment, and a control unit that refrains from accessing the restricted cell based on the access restriction information in a radio resource control (RRC) idle state or an RRC inactive state.

[0007] A network node according to a third aspect of the present disclosure is a network node used in a mobile communication system, which has a transmitting unit that transmits access restriction information used exclusively for the aviation user device in a restricted cell where access to the aviation user device is restricted, the access restriction information is information that prevents the aviation user device in a radio resource control (RRC) idle state or RRC inactive state from accessing the restricted cell.

[0008] This figure shows an example configuration of a mobile communication system according to the embodiment. This figure shows an example configuration of a UE (User Equipment) according to the embodiment. This figure shows an example configuration of a gNB (Network Node) according to the embodiment. This figure shows the configuration of the protocol stack of the wireless interface of the user plane that handles data. This figure shows the configuration of the protocol stack of the wireless interface of the control plane that handles signaling (control signals). This figure is for explaining the aviation UE according to the embodiment. This figure is for explaining an example of an operation scenario according to the embodiment. This figure shows a first example of notification operation by the aviation UE according to the embodiment. This figure shows a second example of notification operation by the aviation UE according to the embodiment. This figure shows a third example of notification operation by the aviation UE according to the embodiment. This figure is for explaining an example of an operation scenario according to the embodiment. This figure shows an example of a message (inter-node message) that each gNB transmits to other gNBs according to the embodiment. This figure shows an example of operation of a mobile communication system according to the embodiment. This figure is for explaining an example of an operation scenario according to the embodiment. This figure shows the operation of an aviation UE in an RRC idle state or RRC inactive state according to the embodiment.

[0009] A mobile communication system according to an embodiment will be described with reference to the drawings. In the drawings, identical or similar parts are denoted by the same or similar reference numerals.

[0010] (1) The mobile communication system configuration diagram 1 is a diagram showing an example of the configuration of the mobile communication system 1 according to this embodiment. The mobile communication system 1 conforms to the 5th generation system (5GS) of the 3GPP standard. In the following description, 5GS will be used as an example, but the mobile communication system may also have an LTE (Long Term Evolution) system applied to it at least partially, or a 6th generation (6G) system applied at least partially.

[0011] The mobile communication system 1 comprises a user equipment (UE) 100, a 5G radio access network (NG-RAN: Next Generation Radio Access Network) 10, and a 5G core network (5GC: 5G Core Network) 20. Hereinafter, NG-RAN 10 may be simply referred to as RAN 10, and 5GC 20 may be simply referred to as the core network (CN) 20. RAN 10 and CN 20 constitute the network 5 of the mobile communication system 1.

[0012] UE100 is a mobile wireless communication device. UE100 can be any device used by a user. For example, UE100 can be a mobile phone terminal (including a smartphone) and / or a tablet terminal, a notebook PC, a communication module (including a communication card or chipset), a sensor or a device attached to a sensor, a vehicle or a device attached to a vehicle (Vehicle UE), or an aircraft or a device attached to an aircraft (Aerial UE). The link from UE100 to network 5 in the transmission direction is called the uplink (UL), and the link from network 5 to UE100 in the transmission direction is called the downlink (DL).

[0013] NG-RAN10 includes a base station (referred to as "gNB" in the 5G system) 200, which is a type of network node. The gNBs 200 are interconnected via the Xn interface, which is an inter-base station interface. The gNBs 200 manage one or more cells. The gNBs 200 perform wireless communication with UEs 100 that have established a connection with their own cell. The gNBs 200 have radio resource management (RRM) functions, user data (hereinafter simply referred to as "data") routing functions, measurement and control functions for mobility control and scheduling, etc. "Cell" is used as a term to indicate the smallest unit of a wireless communication area. "Cell" is also used as a term to indicate a function or resource that performs wireless communication with a UE 100. One cell belongs to one carrier frequency (hereinafter simply referred to as "frequency").

[0014] Furthermore, gNBs can also connect to the EPC (Evolved Packet Core), which is the core network of LTE. LTE base stations can also connect to 5GC. LTE base stations and gNBs can also be connected via an inter-base station interface.

[0015] 5GC20 includes AMF (Access and Mobility Management Function) and UPF (User Plane Function) 300. The AMF performs various mobility controls for UE100. The AMF manages the mobility of UE100 by communicating with UE100 using NAS (Non-Access Stratum) signaling. The UPF controls data transfer. The AMF and UPF are connected to gNB200 via the NG interface, which is the base station-core network interface.

[0016] Figure 2 shows an example configuration of UE100 (user device) according to this embodiment. UE100 includes a receiving unit 110, a transmitting unit 120, and a control unit 130. The receiving unit 110 and the transmitting unit 120 constitute a wireless communication unit 140 that performs wireless communication with gNB200.

[0017] The receiving unit 110 performs various types of reception under the control of the control unit 130. The receiving unit 110 includes an antenna and a receiver. The receiver converts the radio signal received by the antenna into a baseband signal (received signal) and outputs it to the control unit 130.

[0018] The transmitting unit 120 performs various types of transmissions under the control of the control unit 130. The transmitting unit 120 includes an antenna and a transmitter. The transmitter converts the baseband signal (transmission signal) output by the control unit 130 into a wireless signal and transmits it from the antenna.

[0019] The control unit 130 performs various control and processing operations in the UE 100. Such processing includes processing in each layer described later. The operation of the UE 100 described above and later may be controlled by the control unit 130. The control unit 130 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used in processing by the processor. The processor may include a baseband processor and a CPU (Central Processing Unit). The baseband processor performs modulation, demodulation, encoding, and decoding of baseband signals. The CPU executes programs stored in memory and performs various processing operations.

[0020] Figure 3 shows an example configuration of a gNB200 (network node) according to this embodiment. The gNB200 includes a transmitting unit 210, a receiving unit 220, a control unit 230, and a network communication unit 240. The transmitting unit 210 and the receiving unit 220 constitute a wireless communication unit 250 that performs wireless communication with the UE100. The network communication unit 240 includes a transmitting unit 241 that performs transmission and a receiving unit 242 that performs reception.

[0021] The transmitting unit 210 performs various types of transmissions under the control of the control unit 230. The transmitting unit 210 includes an antenna and a transmitter. The transmitter converts the baseband signal (transmission signal) output by the control unit 230 into a wireless signal and transmits it from the antenna.

[0022] The receiving unit 220 performs various types of reception under the control of the control unit 230. The receiving unit 220 includes an antenna and a receiver. The receiver converts the radio signal received by the antenna into a baseband signal (received signal) and outputs it to the control unit 230.

[0023] The control unit 230 performs various control and processing operations on the gNB 200. Such processing includes processing of each layer described later. The operation of the gNB 200 described above and later may also be controlled by the control unit 230. The control unit 230 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used for processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation, demodulation, encoding, decoding, etc., of the baseband signal. The CPU executes programs stored in memory and performs various processing operations.

[0024] The network communication unit 240 is connected to an adjacent base station via the Xn interface, which is an inter-base station interface. The network communication unit 240 is connected to the AMF / UPF 300 via the NG interface, which is an inter-base station-core network interface. The gNB 200 may consist of a CU (Central Unit) and a DU (Distributed Unit) (i.e., functionally separated), and the two units may be connected by the F1 interface, which is a front-haul interface.

[0025] Figure 4 shows the configuration of the protocol stack for the user plane's wireless interface that handles data.

[0026] The user plane radio interface protocol comprises a physical (PHY) layer, a MAC (Medium Access Control) layer, an RLC (Radio Link Control) layer, a PDCP (Packet Data Convergence Protocol) layer, and an SDAP (Service Data Adaptation Protocol) layer.

[0027] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the PHY layer of UE100 and the PHY layer of gNB200 via a physical channel. The PHY layer of UE100 receives downlink control information (DCI) transmitted from gNB200 on the physical downlink control channel (PDCCH). Specifically, UE100 performs blind decoding of the PDCCH using a Radio Network Temporary Identifier (RNTI) and acquires the successfully decoded DCI as the DCI addressed to its own UE. The DCI transmitted from gNB200 has a CRC (Cyclic Redundancy Code) parity bit added, which is scrambled by the RNTI.

[0028] The MAC layer performs data priority control, retransmission processing using Hybrid ARQ (HARQ: Hybrid Automatic Repeat reQuest), and random access procedures. Data and control information are transmitted between the MAC layer of UE100 and the MAC layer of gNB200 via the transport channel. The MAC layer of gNB200 includes a scheduler. The scheduler determines the transport format for the up and down links (transport block size, modulation and coding scheme (MCS)) and the resource blocks to be allocated to UE100.

[0029] The RLC layer transmits data to the receiving RLC layer using the functions of the MAC layer and PHY layer. Data and control information are transmitted between the RLC layer of UE100 and the RLC layer of gNB200 via a logical channel.

[0030] The PDCP layer performs header compression / decompression, encryption / decryption, etc.

[0031] The SDAP layer maps IP flows, which are the units under which the core network performs QoS (Quality of Service) control, to wireless bearers, which are the units under which the AS (Access Stratum) performs QoS control. Note that if the RAN is connected to the EPC, the SDAP is not required.

[0032] Figure 5 shows the configuration of the protocol stack of the wireless interface of the control plane that handles signaling (control signals).

[0033] The protocol stack of the control plane's wireless interface includes an RRC (Radio Resource Control) layer and a NAS (Non-Access Stratum) layer, instead of the SDAP layer shown in Figure 4.

[0034] RRC signaling for various settings is transmitted between the RRC layer of the UE100 and the RRC layer of the gNB200. The RRC layer controls the logical channel, transport channel, and physical channel in response to the establishment, re-establishment, and release of the radio bearer. If there is a connection (RRC connection) between the RRC of the UE100 and the RRC of the gNB200, the UE100 is in the RRC connected state. If there is no connection (RRC connection) between the RRC of the UE100 and the RRC of the gNB200, the UE100 is in the RRC idle state. If the connection between the RRC of the UE100 and the RRC of the gNB200 is suspended, the UE100 is in the RRC inactive state.

[0035] The NAS layer (also simply referred to as "NAS"), located above the RRC layer, handles session management and mobility management, among other things. NAS signaling is transmitted between the NAS layer of the UE100 and the NAS layer of the AMF300. The UE100 also has an application layer in addition to the wireless interface protocol. Furthermore, the layer below the NAS layer is called the AS layer (also simply referred to as "AS").

[0036] (2) Aerial User Equipment The mobile communication system 1 according to this embodiment supports Aerial UE. Figure 6 is a diagram illustrating Aerial UE 100 according to this embodiment. Aerial UE 100 is a UE capable of aerial communication. Aerial UE 100 may be an Unmanned Aircraft Vehicle (UAV) such as a drone.

[0037] In the illustrated example, gNB200a manages cell a, and gNB200b manages cell b. Cell a is a serving cell of UE100, and cell b is a non-serving cell of UE100. gNB200a forms cell a facing upwards to provide upper-air coverage. gNB200b forms cell b facing downwards to provide ground coverage. However, cells a and b may be managed and formed by a single gNB200.

[0038] In the mobile communication system 1, cells for upper-air coverage and cells for ground coverage may be mixed. In cells for upper-air coverage, one or more beams for upper-air coverage are formed. In beams for upper-air coverage, the main lobe may be pointed upwards while the side lobes are pointed towards the ground. In cells for ground coverage, one or more beams for ground coverage are formed. In beams for ground coverage, the main lobe may be pointed towards the ground while the side lobes are pointed upwards. Each beam may be identified by a synchronization signal block (SSB: SS / PBCH block).

[0039] The Aerial UE100 can communicate wirelessly with the gNB200 in the airspace while flying. However, it is assumed that the Aerial UE100 will not perform continuous high-capacity data transmission. Under these assumptions, the Aerial UE100 does not necessarily need to maintain the RRC connected state; it may transition to the RRC idle state after data transmission is complete, or to the RRC inactive state for small data transmission.

[0040] (3) Notification operation by the aviation user device The notification operation by the aviation UE 100 according to this embodiment will be described.

[0041] FIG. 7 is a diagram for explaining an example of an operation scenario according to this embodiment. FIG. 7 is a view of the aviation UE 100 and the gNB 200 from above. In the illustrated example, it is assumed that the aviation UE 100 moves in the horizontal direction, but the aviation UE 100 may move in the horizontal and vertical directions.

[0042] In this embodiment, a scenario is assumed in which a transmission prohibited area (NTZ: No-Transmit Zone) is provided within the coverage of the gNB 200. The NTZ is a geographical area where transmission by the aviation UE 100 (specifically, transmission of a radio signal) is prohibited. For example, the NTZ is an area where the occurrence of interference should be avoided due to the transmission of a radio signal by the aviation UE 100, and may be provided, for example, at an airport and / or its adjacent area.

[0043] The NTZ may be a geographical area where transmission by the aviation UE 100 is prohibited for a specific frequency band. The aviation UE 100 located within the NTZ may be prohibited from transmitting a radio signal in a specific frequency band. The aviation UE 100 located within the NTZ may be able to transmit a radio signal as long as it is in a frequency band other than the specific frequency band.

[0044] In the illustrated example, the NTZ is a two-dimensional area provided in the horizontal direction and is defined, for example, by a latitude range and a longitude range. The NTZ may be a three-dimensional area provided in the horizontal and vertical directions and may be defined by a latitude range, a longitude range, and an altitude range. Note that the NTZ may be a rectangular or cuboid area. The NTZ may be an area with a complex shape including a circle.

[0045] The aviation UE100 has in advance NTZ information (also referred to as "NTZ information"), in particular, NTZ geographical information. NTZ geographical information is information indicating the geographical area where the NTZ is established, and may include latitude and longitude (and altitude) information. The aviation UE100 may also have in advance NTZ frequency information. NTZ frequency information is information indicating the frequency bands (specific frequency bands) on which transmission is prohibited in the said NTZ.

[0046] In Figure 7(a), the aviation UE100 is in an RRC connected state in the gNB200 cell and is communicating data with the gNB200. In Figure 7(b), the aviation UE100 enters the NTZ and stops transmitting to the gNB200 (uplink transmission). However, if the aviation UE100 suddenly stops uplink transmission when it enters the NTZ, there is a concern that an unexpected error may occur on the gNB200 side.

[0047] The following embodiments describe techniques that enable appropriate handling of scenarios in which an NTZ is provided. The aerial UE 100 is assumed to have a GNSS (Global Navigation Satellite System) receiver and be able to determine its own geographical location (latitude, longitude, and altitude). However, it is not limited to positioning using GNSS, and the aerial UE 100 may perform positioning using, for example, a positioning reference signal (PRS).

[0048] In this embodiment, in FIG. 7(a), the aerial UE 100 acquires information on a transmission prohibited area (NTZ), which is a geographical area where transmission by the aerial UE 100 is prohibited. In FIG. 7(b), in response to determining that the geographical location of the aerial UE 100 belongs to the NTZ in the RRC connected state, the aerial UE 100 transmits a notification indicating that the geographical location of the aerial UE 100 belongs to the NTZ to the gNB 200. The notification may be a notification indicating that the aerial UE 100 stops transmission (uplink transmission) due to the NTZ. Such a notification can avoid the occurrence of unexpected errors in the gNB 200. The notification may be an RRC message (for example, a new message dedicated to the aerial UE). The aerial UE 100 may transmit the notification as an information element (IE) included in, for example, a "UE Assistance Information message". The notification may be a MAC control element (MAC CE) or UCI (Uplink Control Information), but in the following embodiments, an example where the notification is an RRC message will be mainly described.

[0049] The aerial UE 100 that performs such an operation includes a control unit 130 that acquires information on the NTZ, which is a geographical area where transmission by the aerial UE 100 is prohibited, and a transmission unit 120 that transmits a notification indicating that its geographical location belongs to the NTZ to the gNB 200 in response to determining that its geographical location belongs to the NTZ in the RRC connected state (see FIG. 2). On the other hand, the gNB 200 includes a reception unit 220 that receives a notification indicating that the geographical location of the aerial UE 100 in the RRC connected state belongs to the NTZ (see FIG. 3).

[0050] Airborne UE 100 may send a notification to gNB 200 only if it determines that the geographical location of Airborne UE 100 belongs to the NTZ while in the RRC connected state, and also determines that Airborne UE 100 is using a frequency band (specific frequency band) that is prohibited from transmission in the said NTZ. In other words, even if Airborne UE 100 determines that the geographical location of Airborne UE 100 belongs to the NTZ while in the RRC connected state, it does not need to send a notification to gNB 200 if Airborne UE 100 is not using a frequency band (specific frequency band) that is prohibited from transmission in the said NTZ.

[0051] Furthermore, the geographical location of Air UE100 being within the NTZ means that the geographical location of Air UE100 falls within the geographical range of the NTZ, and in the following, this will also be simply referred to as "Air UE100 entering the NTZ." Since transmission by Air UE100 is prohibited in the NTZ, it is preferable for Air UE100 to send a notification to gNB200 immediately before entering the NTZ. Alternatively, Air UE100 may send a notification to gNB200 at the time it enters the NTZ or immediately after entering the NTZ.

[0052] In Figure 7(b), the aviation UE 100 may transition from the RRC connected state to the RRC idle state or the RRC inactive state depending on whether it has determined that its geographical location belongs to the NTZ. In this case, the aviation UE 100 may autonomously transition from the RRC connected state to the RRC idle state or the RRC inactive state. Since transmission by the aviation UE 100 is prohibited in the NTZ, the power consumption of the aviation UE 100 can be reduced by transitioning to the RRC idle state or the RRC inactive state.

[0053] If the aviation UE 100's geographical location belongs to the NTZ and the aviation UE 100 is using a frequency band (specific frequency band) that is prohibited from transmission in the NTZ, the aviation UE 100 may autonomously transition from the RRC connected state to the RRC idle state or the RRC inactive state. If the aviation UE 100's geographical location belongs to the NTZ and the aviation UE 100 is using a frequency band (specific frequency band) that is prohibited from transmission in the NTZ, and the aviation UE 100 determines that it cannot use another frequency band, the aviation UE 100 may autonomously transition from the RRC connected state to the RRC idle state or the RRC inactive state.

[0054] Alternatively, if the aircraft UE 100 determines that its geographical location belongs to the NTZ, it may send information to the gNB 200 prompting the aircraft UE 100 to transition its RRC state to the RRC idle state or the RRC inactive state. This information may be referred to as "Release Assistance Information." This information may also be an information element indicating the recommended RRC state for the UE 100. This information may also be an information element (IE) included in an RRC message, for example, a "UE Assistance Information message." This allows the gNB 200 to send an RRC Release message to the aircraft UE 100 to transition its RRC state to the RRC idle state or the RRC inactive state.

[0055] Assuming that the NTZ is a geographical area where transmission by the Aeronautical UE 100 is prohibited for a specific frequency band, the Aeronautical UE 100 may, upon determining that its geographical location belongs to the NTZ, transmit information (frequency information) to the gNB 200 to identify frequency bands that do not belong to the specific frequency band. This frequency information may be information indicating frequency bands that do not belong to the specific frequency band, or information indicating the specific frequency band. The Aeronautical UE 100 may transmit this frequency information as an information element (IE) included in an RRC message, for example, a "UE Assistance Information message".

[0056] This allows the gNB 200 to control the UE 100 to use a frequency band that does not belong to the specific frequency band, based on the frequency information. This allows the UE 100 to maintain the RRC connected state and continue data communication with the target cell. For example, the gNB 200 may instruct the UE 100 to switch to a cell belonging to a frequency band that does not belong to the specific frequency band (i.e., switch the serving cell). The cell switch may be a handover or an LTM (L1 / L2-triggered mobility) cell switch, but in the following, we will mainly assume a handover as the cell switch.

[0057] In Figure 7(c), after determining that its geographical location belongs to the NTZ, the aviation UE 100 may, upon determining that its geographical location no longer belongs to the NTZ, send a notification to the gNB 200 indicating that its geographical location no longer belongs to the NTZ.

[0058] Note that the geographical location of the aerial UE 100 no longer belonging to the NTZ means that the geographical location of the aerial UE 100 leaves the geographical range of the NTZ, and in the following, this will also be simply referred to as "the aerial UE 100 leaving the NTZ." Since transmission by the aerial UE 100 is prohibited in the NTZ, it is preferable for the aerial UE 100 to send a notification to the gNB 200 immediately before leaving the NTZ. Alternatively, the aerial UE 100 may send a notification to the gNB 200 at the time it leaves the NTZ or immediately before it leaves the NTZ. The notification may indicate that the aerial UE 100 is resuming transmission (uplink transmission). The notification may also be an RRC message (for example, a new message specifically for the aerial UE). The aerial UE 100 may send the notification as an information element (IE) included in, for example, a "UE Assistance Information message." The notification may be a MAC control element (MAC CE) or UCI (Uplink Control Information), but the following embodiments will primarily describe an example where the notification is an RRC message.

[0059] Figure 8 shows a first example of notification operation by the airborne UE 100 according to this embodiment. In the first example of operation, it is assumed that the airborne UE 100 stops (cancels) uplink transmission while maintaining the RRC connected state, based on the fact that it has entered the NTZ.

[0060] In step S101, the aircraft UE100 is in an RRC connected state in the cell (serving cell) of the gNB200. The aircraft UE100 is assumed to be in flight.

[0061] In step S102, the aviation UE 100 acquires NTZ information. The AS layer of the aviation UE 100 (e.g., the RRC layer) may acquire NTZ information from a higher layer (such as the application layer). The NTZ information may also be notified from a higher layer. The NTZ information may also be notified from the gNB 200 to the aviation UE 100. Notification from the gNB 200 to the aviation UE 100 may be performed using UE-specific signaling (dedicated signaling), for example, by including the NTZ information in an RRC Reconfiguration message. Notification from the gNB 200 to the aviation UE 100 may also be performed using broadcast signaling, for example, by including the NTZ information in an SIB.

[0062] In step S103, the aircraft UE100 begins positioning to determine its geographical location (latitude, longitude, and altitude). Note that the order of steps S101 to S103 is not limited to the illustrated example.

[0063] In step S104, the aircraft UE100 determines whether it has entered (or is in) the NTZ. For example, the aircraft UE100 determines whether its position is within the latitude and longitude (altitude) area of ​​the NTZ.

[0064] If it is determined that it is entering (or has entered) the NTZ (step S104: YES), in step S105, the aviation UE 100 notifies the gNB 200 of its entry into (or entry into) the NTZ using an RRC message. For example, the aviation UE 100 may also notify using a "UE Assistance Information message".

[0065] In step S106, the aviation UE 100 stops uplink transmission within the NTZ. The aviation UE 100 may stop uplink transmission only in a specific frequency band within the NTZ.

[0066] In step S107, the gNB200 maintains the aviation UE100 in an RRC connected state, but does not allocate (schedule) resources (particularly uplink radio resources in a specific frequency band) to the aviation UE100.

[0067] In step S108, the aircraft UE100 determines whether it has left (or is leaving) the NTZ. For example, the aircraft UE100 determines whether its position has moved outside the latitude and longitude (altitude) area of ​​the NTZ.

[0068] If it is determined that it has left the NTZ (step S108: YES), in step S109, the aviation UE 100 notifies the gNB 200 of the departure from the NTZ via an RRC message. The aviation UE 100 may send a scheduling request (SR) and / or a buffer status report (BSR) to the gNB 200, and after receiving an allocation of uplink radio resources from the gNB 200, it may send a notification (RRC message) using those uplink radio resources. Alternatively, the gNB 200 may consider the SR and / or BSR as a notification indicating that it has left the NTZ.

[0069] In step S110, gNB200 resumes data communication with aviation UE100. Aviation UE100 resumes uplink data transmission to gNB200 (in particular uplink transmission in a specific frequency band).

[0070] Figure 9 shows a second example of notification operation by the aviation UE 100 according to this embodiment. In the second example, it is assumed that the aviation UE 100 transitions from the RRC connected state to the RRC idle state or the RRC inactive state based on entering the NTZ. In the following description of the second example, redundant explanations of operations similar to the first example will be omitted.

[0071] The operations in steps S201 to S204 are the same as in the first operation example described above.

[0072] If it is determined that it is entering (or has entered) the NTZ (step S204: YES), in step S205, the aviation UE 100 notifies the gNB 200 of its entry into (or entry into) the NTZ using an RRC message. For example, the aviation UE 100 may also notify using a "UE Assistance Information message".

[0073] In step S205, the aviation UE 100 may notify the gNB 200 that it will autonomously transition to the RRC idle state / RRC inactive state. This allows the gNB 200 to recognize that the aviation UE 100 will transition to the RRC idle state / RRC inactive state. In this case, after sending the notification, the aviation UE 100 will autonomously transition to the RRC idle state / RRC inactive state (step S207).

[0074] In step S205, the aviation UE 100 may send a "RAI (Release Assistance Information)" to the gNB 200. The RAI may be the same as or different from the RRC message in step S105. In this case, the gNB 200, upon receiving the RAI, may send an RRC Release message to the aviation UE 100 in step S206 to transition the aviation UE 100 to the RRC idle state / RRC inactive state.

[0075] In step S207, the aircraft UE100 transitions from the RRC connected state to the RRC idle state / RRC inactive state.

[0076] In step S208, the aircraft UE100 determines whether it has left (or is leaving) the NTZ. For example, the aircraft UE100 determines whether its position has moved outside the latitude and longitude (altitude) area of ​​the NTZ.

[0077] If it is determined that the aircraft has left (or is leaving) the NTZ (step S208: YES), in step S209, the aircraft UE 100 transitions from the RRC idle state / RRC inactive state to the RRC connected state. Specifically, the aircraft UE 100 transitions to the RRC connected state by performing an RRC establishment procedure or an RRC resume procedure with a random access procedure.

[0078] If it is determined that aircraft UE100 has left (or is leaving) the NTZ (step S208: YES), in step S210, aircraft UE100 may notify gNB200 of its departure from the NTZ via an RRC message.

[0079] In step S211, gNB200 resumes data communication with aviation UE100. Aviation UE100 resumes uplink data transmission to gNB200 (in particular uplink transmission in a specific frequency band).

[0080] Figure 10 shows a third example of notification operation by the aviation UE 100 according to this embodiment. In the third example of operation, it is assumed that the aviation UE 100, based on entering the NTZ, performs cell switching processing to a frequency band that does not belong to a specific frequency band while maintaining the RRC connected state.

[0081] The operations in steps S301 to S304 are the same as in the first operation example described above.

[0082] If it is determined that it is entering (or has entered) the NTZ (step S304: YES), in step S305, the aviation UE 100 notifies the gNB 200 of its entry into (or entry into) the NTZ using an RRC message. For example, the aviation UE 100 may also notify using a "UE Assistance Information message".

[0083] In step S305, if there are any frequency bands that do not belong to a specific frequency band, i.e., frequencies that are not subject to NTZ regulations, the aviation UE 100 may notify the gNB 200 of such frequencies (frequency bands).

[0084] In step S306, gNB200 decides to switch the serving cell of aviation UE100 to a cell on a frequency outside the NTZ (for example, to hand over).

[0085] In step S307, gNB200 sends a command to UE100 to switch the serving cell of aviation UE100 to a cell on a frequency outside the NTZ (for example, to hand over).

[0086] In step S308, the aviation UE100, in response to receiving the command in step S307, accesses a cell with a frequency outside the NTZ target as the target cell and performs cell switching.

[0087] (4) Operation related to inter-node signaling The inter-node signaling (gNB200 inter-signaling) according to this embodiment will be described below. The operation related to gNB200 inter-signaling described below may be performed in combination with the third example of the notification operation by the aviation UE100 described above.

[0088] Figure 11 is a diagram illustrating an example of an operation scenario according to this embodiment. Figure 11 is a view of the aircraft UE 100 and each gNB 200 from above. In the illustrated example, the aircraft UE 100 is assumed to move horizontally, but the aircraft UE 100 may move both horizontally and vertically. Each cell C shown in Figure 11 is assumed to provide overhead coverage.

[0089] In the illustrated example, gNB200a manages cells Ca1 to Ca4, gNB200b manages cells Cb1 to Cb4, and gNB200c manages cells Cc1 to Cc3. Of cells Cb1 to Cb4 of gNB200b, cells Ca1 and Ca4 partially overlap with NTZ. Cells that partially overlap with NTZ are referred to as "cells belonging to NTZ". Also, of cells Cc1 to Cc3 of gNB200c, cells Cc1 and Cc3 are cells belonging to NTZ.

[0090] In the illustrated example, the aircraft UE 100 is in an RRC connected state in cell Ca1 of gNB 200a and is communicating data with gNB 200a (cell Ca1). As the aircraft UE 100 moves, it becomes necessary to perform mobility control to switch the serving cell of the aircraft UE 100 from cell Ca1 to another cell. Mobility control of the aircraft UE 100 in the RRC connected state is a handover triggered by the RRC layer, which is layer 3, or an LTM cell switch triggered by layer 1 / layer 2. Mobility control of the aircraft UE 100 in the RRC connected state may also be a conditional handover or a conditional LTM cell switch. In a conditional handover or conditional LTM cell switch, the execution conditions for cell switching to a candidate cell are set for the aircraft UE 100, and when the execution conditions for cell switching are met, the aircraft UE 100 performs a serving cell switch to the candidate cell.

[0091] Here, if a cell belonging to the NTZ is designated by gNB200a to the Aerial UE100 as a target cell or candidate cell for serving cell switching, the Aerial UE100 may switch its serving cell to a cell belonging to the NTZ. However, since transmission by the Aerial UE100 is prohibited in the NTZ, if a cell belonging to the NTZ becomes the serving cell of the Aerial UE100 due to serving cell switching, there is a risk that the Aerial UE100 will be unable to transmit radio signals. For this reason, it is desirable for gNB200a to determine a cell that does not belong to the NTZ as a target cell or candidate cell for serving cell switching.

[0092] The following embodiments describe a technique for realizing gNB200 signaling that enables appropriate handling of scenarios in which an NTZ is provided.

[0093] In this embodiment, gNB200b sends a message to gNB200a containing information about each cell Cb of gNB200b. The message includes information indicating whether each cell Cb belongs to the NTZ. This allows gNB200a to determine whether each cell Cb not under its control belongs to the NTZ. Therefore, gNB200a can determine which cells Cb do not belong to the NTZ (for example, cell Cb2 or cell Cb3) among the cells Cb to be used as target cells or candidate cells for serving cell switching of the air UE100.

[0094] Similarly, gNB200c sends a message to gNB200a containing information about each cell Cc of gNB200c. This message includes information indicating whether each cell Cc belongs to the NTZ. This allows gNB200a to determine whether each cell Cc not under its control belongs to the NTZ. Therefore, gNB200a can determine a cell Cc that does not belong to the NTZ (for example, cell Cc2) among the cells Cc as a target cell or candidate cell for serving cell switching of the aviation UE100.

[0095] A gNB200a performing such operations includes a receiving unit 242 that receives a message from another gNB200 (gNB200b, gNB200c in the illustrated example) containing information about the cell of that other gNB200, and a control unit 230 that performs mobility control of the RRC-connected aircraft UE100 in the cell of gNB200a (cell Ca1 in the illustrated example) based on the information contained in the message.

[0096] The messages sent and received between such gNB200s may be internode messages for setting up the Xn interface, which is an internode interface. These internode messages may be the "Xn Setup Request message" or "Xn Setup Response message" used in the Xn Setup procedure. That is, information on whether or not each cell belongs to the NTZ is exchanged between gNB200s using the "Xn Setup Request message" or "Xn Setup Response message". Assuming that the NTZ is a fixed area, it is preferable, for example, to be able to exchange the NTZ status of each cell when setting up the Xn interface during the installation of the gNB200.

[0097] Alternatively, the messages sent and received between gNB200s may be inter-node messages for updating the configuration on the gNB200s. These inter-node messages may be the "gNB Configuration Update message" or "gNB Configuration Update Acknowledge message" used in the gNB Configuration Update procedure. In other words, information on whether each cell belongs to the NTZ is exchanged between gNB200s using the "gNB Configuration Update message" or "gNB Configuration Update Acknowledge message". Given that the NTZ may change, it is preferable to be able to appropriately exchange the NTZ status of each cell in the gNB Configuration Update procedure.

[0098] Each gNB200 may send a message to other gNB200s that includes a list of its own cells belonging to the NTZ.

[0099] As described above, the NTZ is a geographical area where transmission by aerial UE100 is prohibited in certain frequency bands (also referred to as "prohibited frequency bands"). Under these circumstances, each gNB200 may transmit a message to other gNB200s that includes information indicating the specific frequency band of the NTZ to which its cell belongs.

[0100] Figure 12 shows an example of a message (internode message) that each gNB200 transmits to other gNB200 according to this embodiment. In the illustrated example, the message that each gNB200 transmits to other gNB200 includes the cell ID of its own cell, information indicating whether or not its own cell provides airspace coverage, information indicating whether or not its own cell belongs to an NTZ, and information indicating the prohibited frequency band of the NTZ.

[0101] Figure 13 shows an example of the operation of the mobile communication system 1 according to this embodiment. Here, we will explain the operation assuming the operation scenario shown in Figure 11.

[0102] In step S401, gNB200b transmits the above-described internode message to gNB200a. gNB200a receives the internode message and stores the information contained in the internode message. The internode message includes information about each cell Cb of gNB200b, indicating whether or not the cell Cb belongs to the NTZ. The information about each cell Cb of gNB200b may also include information indicating whether or not the cell Cb provides upper-air coverage. If the cell Cb belongs to the NTZ, the information about each cell Cb of gNB200b may also include information indicating the prohibited frequency of the NTZ.

[0103] In step S402, gNB200a transmits the above-described internode message to gNB200b. gNB200b receives the internode message and stores the information contained in the internode message. The internode message includes information about each cell Ca of gNB200a, indicating whether or not the cell Ca belongs to the NTZ. The information about each cell Ca of gNB200a may also include information indicating whether or not the cell Ca provides upper-air coverage. If the cell Ca belongs to the NTZ, the information about each cell Ca of gNB200a may also include information indicating the prohibited frequency of the NTZ.

[0104] Subsequently, in step S403, the aircraft UE100 is in an RRC connected state in the cell of gNB200a. That is, the cell of gNB200a is the serving cell of the aircraft UE100.

[0105] In step S404, gNB200a transmits measurement settings to the aerial UE100 for setting up radio quality measurements and reporting for each cell by the aerial UE100. The aerial UE100 receives the measurement settings. gNB200a may also transmit an RRC Reconfiguration message containing the measurement settings to the aerial UE100. The measurement settings include setting information that specifies the measurement targets and setting information that specifies the trigger for transmitting the measurement report. gNB200a may determine the content of the measurement settings based on the message received in step S401. For example, gNB200a may exclude cells belonging to the NTZ from the measurement targets. It may also exclude prohibited frequency bands included in the message received in step S401 from the measurement targets. gNB200a may also exclude cells that do not provide airspace coverage from the measurement targets.

[0106] In step S405, the aviation UE 100 performs radio quality measurements of each cell based on the measurement settings received in step S404 and obtains the measurement results for each cell.

[0107] In step S406, the aerial UE100 transmits a measurement report, including the measurement results for each cell, to the gNB200a. The gNB200a receives the measurement report.

[0108] In step S407, gNB200a decides whether or not to perform a handover of the airborne UE100 based on the measurement report received from UE100. If gNB200a decides to perform a handover of the airborne UE100, it may determine the target cell for the handover. Here, gNB200a may determine the target cell based on the message received in step S401. For example, gNB200a may exclude cells belonging to the NTZ from the target cells. It may also exclude cells belonging to prohibited frequency bands included in the message received in step S401 from the target cells. gNB200a may also exclude cells that do not provide airborne coverage from the target cells. Here, it is assumed that gNB200a has determined the cells of gNB200b that do not belong to the NTZ as the target cells.

[0109] In step S408, gNB200a sends a handover request message to gNB200b requesting a handover of UE100 to the target cell. gNB200b receives the handover request message.

[0110] In step S409, gNB200b sends a handover response message to gNB200a in response to the handover request message in step S408. gNB200a receives the handover response message.

[0111] In step S410, gNB200a transmits a handover command (i.e., an instruction to switch the serving cell to the target cell) to aviation UE100 based on the handover response message in step S409. Aviation UE100 receives the handover command.

[0112] In step S411, the aviation UE 100 accesses the target cell of gNB 200b specified by the handover command and switches the serving cell of the aviation UE 100 to that target cell.

[0113] (5) Operation of the aircraft user device in the RRC idle state or RRC inactive state The above-described operation mainly assumed that the aircraft UE 100 was in the RRC connected state. In contrast, the operation of the following embodiment assumes that the aircraft UE 100 is in the RRC idle state or RRC inactive state. This operation may be performed in combination with the operation according to the above-described embodiment.

[0114] This section provides an overview of cell reselection. When an aircraft UE100 is in an RRC idle or RRC inactive state, it performs a cell reselection procedure to move from its current serving cell to an adjacent cell (non-serving cell) as it moves. Specifically, the aircraft UE100 identifies the adjacent cell to which it should camp on using the cell reselection procedure and reselects the identified adjacent cell. When the current serving cell and the adjacent cell have the same frequency (carrier frequency), it is called intra-frequency, and when the current serving cell and the adjacent cell have different frequencies (carrier frequencies), it is called inter-frequency. There are two types of cell reselection procedures: intra-frequency cell reselection and inter-frequency cell reselection.

[0115] The intra-frequency cell reselection procedure reselects cells based on their ranking. For example, the intra-frequency cell reselection procedure performs the following processes:

[0116] Firstly, the Aerial UE100 performs a measurement process to measure the radio quality for each serving cell and adjacent cell. Specifically, the Aerial UE100 measures the RSRP and RSRQ of the CD-SSB (Cell Defining-Synchronization Signal and PBCH block) for each serving cell and adjacent cell.

[0117] Secondly, for all cells that satisfy the cell selection criterion S, the aviation UE100 calculates a ranking criterion (Rs) for the serving cell and a ranking criterion (Rn) for adjacent cells. The cell selection criterion S is the criterion for selecting cells in which the RSRP exceeds the minimum RSRP requirement level and the RSRQ exceeds the minimum RSRQ requirement level. In the aviation UE100, the highest-ranked cell is basically re-selected from the two ranking criteria Rs and Rn.

[0118] On the other hand, the inter-frequency cell reselection procedure performs cell reselection based on absolute frequency priority. Frequency priority is provided from gNB200 to aviation UE100 via broadcast signaling (e.g., system information block) or dedicated signaling (e.g., RRC release message). The inter-frequency cell reselection procedure performs the following processes, for example:

[0119] Firstly, the Aerial UE 100 performs a measurement process to measure the radio quality of the serving cell and adjacent cells. Specifically, the Aerial UE 100 always measures the radio quality of frequencies that have a higher priority than the current serving cell's frequency priority. Furthermore, for frequencies with the same or lower priority as the current serving cell's frequency priority, the Aerial UE 100 measures the radio quality of frequencies with the same or lower priority if the current serving cell's radio quality falls below a predetermined quality.

[0120] Secondly, the aerial UE 100 performs a cell reselection process to reselect a cell (serving cell) to which it will camp on, based on the measurement results. Specifically, the aerial UE 100 may reselect a cell to an adjacent cell if the frequency priority of the adjacent cell is higher than the priority of the current serving cell, and the adjacent cell meets predetermined quality standards (i.e., minimum required quality standards) for a predetermined period. If the frequency priority of the adjacent cell is the same as the priority of the current serving cell, the aerial UE 100 may rank the radio quality of the adjacent cell and reselect a cell to an adjacent cell that has a higher rank than the current serving cell for a predetermined period. If the frequency priority of the adjacent cell is lower than the priority of the current serving cell, and the radio quality of the current serving cell is lower than a radio quality threshold, and the radio quality of the adjacent cell remains higher than another radio quality threshold for a predetermined period, the aerial UE 100 may reselect a cell to an adjacent cell.

[0121] Figure 14 is a diagram illustrating an example of an operation scenario according to this embodiment. The operation scenario shown in Figure 14 differs from the operation scenario shown in Figure 11 in that the aircraft UE 100 is in an RRC idle state or an RRC inactive state, rather than an RRC connected state. In other respects, it is the same as the operation scenario shown in Figure 11.

[0122] In the illustrated example, aircraft UE100 is in an RRC idle or RRC inactive state in cell Ca1 of gNB200a, and is performing paging monitoring from gNB200a (cell Ca1). As aircraft UE100 moves, it becomes necessary to perform mobility control to switch the serving cell of aircraft UE100 from cell Ca1 to another cell. Mobility control of aircraft UE100 in the RRC idle or RRC inactive state is achieved by cell reselection as described above.

[0123] Here, the aviation UE100 may re-select a cell belonging to the NTZ. However, since transmission by the aviation UE100 is prohibited in the NTZ, if a cell belonging to the NTZ becomes the serving cell of the aviation UE100, there is a risk that the aviation UE100 will be unable to transmit radio signals. Therefore, when a cell belonging to the NTZ becomes the serving cell of the aviation UE100, there is a problem in that the aviation UE100 cannot transition from the RRC idle state or RRC inactive state to the RRC connected state. For this reason, it is desirable that the aviation UE100 in the RRC idle state or RRC inactive state does not camp on to a cell belonging to the NTZ.

[0124] The following embodiments describe operations that enable appropriate handling of scenarios in which an NTZ is provided.

[0125] Figure 15 shows the operation of the aircraft UE100 in the RRC idle state or RRC inactive state according to this embodiment.

[0126] In step S501, an aviation UE 100 in an RRC idle or RRC inactive state receives access restriction information broadcast from a restricted cell that restricts access to the aviation UE 100 and is used exclusively for the aviation UE 100. Such access restriction information may be referred to as aviation UE-specific Cell Barring information.

[0127] In step S502, the aircraft UE 100, which is in an RRC idle or RRC inactive state, refrains from accessing the restricted cell based on the received access restriction information. Refraining from access may also mean refraining from re-selecting a cell to the restricted cell. Refraining from access may also mean not camping on to the restricted cell.

[0128] As a result, aircraft UE100 in an RRC idle or RRC inactive state will not camp on to a cell belonging to the NTZ, thus enabling appropriate handling of scenarios in which an NTZ is provided.

[0129] The aerial UE 100 performing this operation has a receiving unit 110 that receives access restriction information broadcast from a restricted cell where access to the aerial UE 100 is restricted and which is used exclusively for the aerial UE 100, and a control unit 130 that refrains from accessing the restricted cell based on the access restriction information when the RRC is idle or inactive (see Figure 2). On the other hand, the gNB 200 has a transmitting unit 210 that transmits access restriction information used exclusively for the aerial UE 100 in a restricted cell where access to the aerial UE 100 is restricted (see Figure 3).

[0130] In this embodiment, the limiting cell is a cell belonging to the NTZ. The limiting cell may also be referred to as an NTZ cell.

[0131] In this embodiment, access restriction information is included in a system information block (SIB) or master information block (MIB) broadcast in the restricted cell. The SIB and MIB are information that can be received by an aviation UE 100 in an RRC idle state or RRC inactive state. Therefore, an aviation UE 100 in an RRC idle state or RRC inactive state can refrain from accessing the restricted cell based on the access restriction information included in the SIB or MIB.

[0132] The aerial UE 100 may determine whether it is above a predetermined altitude. Being above a predetermined altitude may mean that the aerial UE 100 is in flight. That is, the aerial UE 100 may check its flight status and apply access restriction information if it is in flight. If the aerial UE 100 is above a predetermined altitude, the aerial UE 100 may refrain from accessing restricted cells based on the access restriction information. In cases where the aerial UE 100 is on the ground, transmission by the aerial UE 100 may be permitted even to restricted cells (NTZ cells). Therefore, the aerial UE 100 may refrain from accessing restricted cells based on the access restriction information only if it is above a predetermined altitude.

[0133] The access restriction information may include a threshold indicating a predetermined altitude. That is, gNB200 may be able to specify a predetermined altitude. If the altitude of aviation UE100 is above the threshold, aviation UE100 may refrain from accessing the restricted cell based on the access restriction information.

[0134] If an aviation UE 100 is in an RRC idle or RRC inactive state and refrains from accessing a restricted cell based on access restriction information, it may perform a cell search and / or cell reselection on a frequency different from the frequency to which the restricted cell belongs (prohibited frequency band). This makes it easier for the aviation UE 100 to camp on a cell that is not a restricted cell (NTZ cell).

[0135] Assuming that NTZ is a geographical area where transmission by aerial UE 100 is prohibited in a specific frequency band (prohibited frequency band), aerial UE 100 may receive frequency information broadcast from gNB 200 and relating to that specific frequency band (prohibited frequency band). The frequency information may be information included in an SIB (for example, an SIB for cell reselection). The frequency information may also be information used exclusively by aerial UE 100 (aerial UE-specific frequency information).

[0136] The frequency information may indicate a specific frequency band (prohibited frequency band). The frequency information may also indicate a frequency band different from the specific frequency band (prohibited frequency band) (permitted frequency band). An aviation UE 100 in an RRC idle or RRC inactive state may prioritize a frequency band different from the specific frequency band (prohibited frequency band) (permitted frequency band) in cell re-selection. For example, the aviation UE 100 may set the permitted frequency band (permitted frequency) as the highest priority for frequency priority in cell re-selection.

[0137] Furthermore, frequency information may be broadcast by restricted cells (NTZ cells). Frequency information may be broadcast by serving cells of the aviation UE 100. The frequency information may also be broadcast by non-serving cells of the aviation UE 100. In other words, any cell (any gNB 200) may broadcast frequency information. Each gNB 200 may identify a specific frequency band (prohibited frequency band) in the manner described in the embodiments above. Based on the frequency information, the aviation UE 100 may perform a cell search and / or cell reselection for frequencies that do not belong to a specific frequency band (prohibited frequency band). This makes it easier for the aviation UE 100 to camp on to cells that are not restricted cells (NTZ cells).

[0138] Alternatively, the aviation UE 100 may receive a list of restricted cells (NTZ cells), also referred to as the "exclusion list," transmitted from the gNB 200. The exclusion list may be information contained in an SIB (for example, an SIB for cell re-selection). The exclusion list may be a list used exclusively by the aviation UE 100 (an aviation UE-specific exclusion list). The exclusion list may include the cell ID of each restricted cell (NTZ cell).

[0139] The exclusion list may be broadcast by the serving cell of the aviation UE 100. The exclusion list may also be broadcast by the non-serving cell of the aviation UE 100. That is, any cell (any gNB 200) may broadcast the exclusion list. Each gNB 200 may identify restricted cells (NTZ cells) in the manner described in the embodiments above. The aviation UE 100 may perform cell searches and / or cell re-selections while excluding restricted cells (NTZ cells) based on the exclusion list. This makes it easier for the aviation UE 100 to camp on to cells that are not restricted cells (NTZ cells).

[0140] Alternatively, the aviation UE100 may receive a list of cells (also called the "allowed list") transmitted from the gNB200 that are not restricted cells (NTZ cells). The allowed list may be information contained in an SIB (for example, an SIB for cell reselection). The allowed list may be a list used exclusively by the aviation UE100 (an aviation UE-specific allowed list). The allowed list may include the cell IDs of each restricted cell (NTZ cell).

[0141] The allow list may be broadcast by the serving cell of Aerial UE 100. The allow list may also be broadcast by a non-serving cell of Aerial UE 100. That is, any cell (any gNB 200) may broadcast the allow list. Aerial UE 100 may perform a cell search and / or cell reselection based on the allow list, targeting cells that are not restricted cells (NTZ cells). This makes it easier for Aerial UE 100 to camp on to cells that are not restricted cells (NTZ cells).

[0142] Although the operation in cell re-selection has been described here, similar operations may be applied to cell selection in general, not just cell re-selection. The aviation UE 100 may perform cell selection when entering coverage from outside the coverage of network 5. The aviation UE 100 may also perform cell selection when transitioning from the RM-DEREGISTERED state to the RM-REGISTERED state, when transitioning from the CM-IDLE state to the CM-CONNECTED state, or when transitioning from the CM-CONNECTED state to the CM-IDLE state. In cell selection, the aviation UE 100 camps on to a cell that is not a restricted cell (NTZ cell), similar to the operation described above.

[0143] (6) Other Embodiments The operation according to the above embodiment may be applied to a normal UE 100 that is not an aerial UE 100. That is, the operation according to the above embodiment is not limited to an aerial UE 100, but may be applied to a normal UE 100.

[0144] Even if cell re-selection or cell selection is performed according to the above embodiment, the aerial UE 100 may still camp on to a cell (or frequency) belonging to the NTZ. If the aerial UE 100 is camped on a cell (or frequency) belonging to the NTZ, it may refrain from performing the RRC connection establishment process. Specifically, the aerial UE 100 may refrain from accessing a cell (or frequency) belonging to the NTZ by performing one of the following actions: not starting a random access procedure, not sending an RRC connection request message, not sending an RRC recovery request message, or not transferring the call information (UE identifier, etc.) to the upper layer when called by paging.

[0145] A way to facilitate the camp-on of an aerial UE 100 to a cell that is not a restricted cell (NTZ cell) may be for the aerial UE 100 to change the cell selection priority. Specifically, the aerial UE 100 may perform cell selection by considering frequencies belonging to the NTZ or frequencies of cells belonging to the NTZ as the lowest priority. Alternatively, the aerial UE 100 may perform cell selection by considering frequencies not belonging to the NTZ or frequencies of cells not belonging to the NTZ as the highest priority.

[0146] Each of the above-described operation flows (for example, the first to third operation examples) can be performed not only independently but also in combination of two or more operation flows. For example, some steps of one operation flow may be added to another operation flow, or some steps of one operation flow may be replaced with some steps of another operation flow. It is not necessary to execute all steps in each flow; only some steps may be executed. Furthermore, the order of steps in each flow may be changed as appropriate.

[0147] In the embodiments and examples described above, an example in which the base station is an NR base station (gNB) was described, but the base station may also be an LTE base station (eNB) or a 6G base station. Furthermore, the base station may also be a relay node such as an IAB (Integrated Access and Backhaul) node. The base station may also be a DU of an IAB node. Furthermore, UE100 may be an MT (Mobile Termination) of an IAB node. That is, UE100 may be a terminal function unit (a type of communication module) for the base station to control a relay device that performs signal relay. Such a terminal function unit is referred to as an MT. Examples of multi-transmission architectures (MTs) include IAB-MT, NCR (Network Controlled Repeater)-MT, and RIS (Reconfigurable Intelligent Surface)-MT.

[0148] Furthermore, the term "network node" primarily refers to a base station, but may also refer to a core network device or a part of a base station (CU, DU, or RU). Additionally, a network node may consist of a combination of at least a part of the core network device and at least a part of a base station.

[0149] A program may be provided that causes a computer to execute each process performed by the UE100 or gNB200. The program may be recorded on a computer-readable medium. Using a computer-readable medium, it is possible to install the program on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transient recording medium. The non-transient recording medium is not particularly limited, but may be a recording medium such as a CD-ROM and / or DVD-ROM. Alternatively, the circuits that execute each process performed by the UE100 or gNB200 may be integrated, and at least a part of the UE100 or gNB200 may be configured as a semiconductor integrated circuit (chipset, SoC: System on a chip).

[0150] The functions realized by UE100 or gNB200 may be implemented in a circuit or processing circuit, including a general-purpose processor, application processor, integrated circuit, ASICs (Application Specific Integrated Circuits), CPU (a Central Processing Unit), conventional circuitry, and / or a combination thereof, programmed to realize the described functions. A processor, including transistors and / or other circuitry, is considered a circuit or processing circuit. A processor may be a programmed processor that executes a program stored in memory. In this specification, circuitry, unit, and means are hardware programmed to realize or execute the described functions. The hardware may be any hardware disclosed herein, or any hardware known to be programmed to perform or execute the functions described herein. If the hardware is a processor that is considered to be of the type of circuit, the circuit, means, or unit is a combination of hardware and software used to constitute the hardware and / or processor.

[0151] The phrases “based on” and “depending on / in response to” as used in this disclosure do not mean “based solely on” or “in response solely” unless otherwise specified. “Based on” means both “based solely on” and “at least partially on.” Similarly, “depending” means both “at least partially on” and “at least partially on.” The terms “include,” “comprise,” and variations thereof do not mean that they include only the listed items, but may include only the listed items or may include additional items in addition to the listed items. Furthermore, the term “or” as used in this disclosure is not intended to mean exclusive OR. Additionally, any reference to elements using designations such as “first,” “second,” etc., as used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used herein as a convenient way to distinguish between two or more elements. Therefore, references to the first and second elements do not imply that only two elements may be adopted therein, or that the first element must precede the second element in any way. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles shall be plural unless it is clearly indicated from the context that they are not.

[0152] Although the embodiments have been described in detail above with reference to the drawings, the specific configuration is not limited to those described above, and various design changes can be made without departing from the gist of the invention.

[0153] This application claims priority to Japanese Patent Application No. 2024-172546 (filed on October 1, 2024), the entirety of which is incorporated into the specification of this application.

[0154] (7) Additional notes: Features of the above-described embodiments are noted below.

[0155] - Appendix 1 A communication method performed by an aviation user device in a mobile communication system, comprising: receiving access restriction information broadcast from a restricted cell on which access to the aviation user device is restricted and which is used exclusively for the aviation user device; and refraining from accessing the restricted cell based on the access restriction information when the Radio Resource Control (RRC) is idle or inactive.

[0156] - Appendix 2 The communication method described in Appendix 1, wherein the restricted cell is a cell belonging to a transmission prohibited area, which is a geographical area where transmission by the aerial user device is prohibited.

[0157] - Appendix 3 The access restriction information is included in the system information block (SIB) or master information block (MIB) broadcast in the restriction cell, and is communicated using the method described in Appendix 1 or 2.

[0158] - Appendix 4 The communication method described in any of Appendix 1 to 3, which includes refraining from accessing the cell based on the access restriction information.

[0159] - Appendix 5 The communication method according to any one of Appendix 1 to 4, further comprising determining whether the aircraft user device is at or above a predetermined altitude, wherein if the aircraft user device is at or above the predetermined altitude, the aircraft user device refrains from accessing the restricted cell based on the access restriction information.

[0160] - Appendix 6 The communication method described in Appendix 5, wherein the state above the predetermined altitude is the state in which the aircraft user device is in flight.

[0161] - Appendix 7 The communication method according to Appendix 5 or 6 wherein the access restriction information includes a threshold indicating the predetermined altitude, and the aircraft user device refrains from accessing the restricted cell based on the access restriction information when the altitude of the aircraft user device is equal to or greater than the threshold.

[0162] - Appendix 8 The transmission prohibited area is a geographical area in which transmission by the aviation user device is prohibited for a specific frequency band, and the aviation user device receives frequency information broadcast from a network node and relating to the specific frequency band, and performs cell search and / or cell reselection for frequencies not belonging to the specific frequency band based on the frequency information, according to any one of the communications methods described in Appendix 2 to 7.

[0163] - Appendix 9 The communication method according to any one of Appendix 1 to 8, wherein the aviation user device in the RRC idle state or the RRC inactive state refrains from accessing the restricted cell based on the access restriction information, and performs a cell search and / or cell reselection for a frequency different from the frequency to which the restricted cell belongs.

[0164] - Appendix 10 An aviation user device for use in a mobile communication system, comprising: a receiving unit that receives access restriction information broadcast from a restricted cell to which access to the aviation user device is restricted and which is used exclusively for the aviation user device; and a control unit that refrains from accessing the restricted cell based on the access restriction information when the Radio Resource Control (RRC) is idle or inactive.

[0165] - Appendix 11 A network node used in a mobile communication system, having a transmitting unit that transmits access restriction information exclusively for the aviation user device in a restricted cell where access to the aviation user device is restricted, wherein the access restriction information is information that prevents the aviation user device in a radio resource control (RRC) idle state or RRC inactive state from accessing the restricted cell.

[0166] 1: Mobile communication system 5: Network 10: RAN 20: CN 100: UE (Aerial UE) 110: Receiving unit 120: Transmitting unit 130: Control unit 140: Wireless communication unit 200a, 200b, 200c: gNB 210: Transmitting unit 220: Receiving unit 230: Control unit 240: Network communication unit 241: Transmitting unit 242: Receiving unit 250: Wireless communication unit 300: AMF / UPF C, Ca1-Ca4, Cb1-Cb4, Cc1-Cc3: Cell

Claims

1. A communication method performed by an aviation user device in a mobile communication system, comprising: receiving access restriction information broadcast from a restricted cell on which access to the aviation user device is restricted and which is used exclusively for the aviation user device; and refraining from accessing the restricted cell based on the access restriction information when the Radio Resource Control (RRC) is idle or inactive.

2. The communication method according to claim 1, wherein the restricted cell is a cell belonging to a transmission prohibited area, which is a geographical area where transmission by the aviation user device is prohibited.

3. The communication method according to claim 1, wherein the access restriction information is included in a system information block (SIB) or master information block (MIB) broadcast in the restriction cell.

4. The communication method according to claim 1, wherein refraining from access includes refraining from re-selecting a cell to the restricted cell based on the access restriction information.

5. The communication method according to claim 1, further comprising determining whether the aircraft user device is at or above a predetermined altitude, wherein if the aircraft user device is at or above the predetermined altitude, it refrains from accessing the restricted cell based on the access restriction information.

6. The communication method according to claim 5, wherein the state above a predetermined altitude is the state in which the aircraft user device is in flight.

7. The communication method according to claim 5, wherein the access restriction information includes a threshold indicating a predetermined altitude, and the aircraft user device refrains from accessing the restricted cell based on the access restriction information when the altitude of the aircraft user device is equal to or greater than the threshold.

8. The communication method according to claim 2, wherein the transmission prohibited area is a geographical area in which transmission by the aviation user device is prohibited for a specific frequency band, the aviation user device receives frequency information broadcast from a network node and relating to the specific frequency band, and performs cell search and / or cell reselection for frequencies not belonging to the specific frequency band based on the frequency information.

9. The communication method according to any one of claims 1 to 8, wherein the aviation user device, in the RRC idle state or the RRC inactive state, refrains from accessing the restricted cell based on the access restriction information, performs a cell search and / or cell reselection for a frequency different from the frequency to which the restricted cell belongs.

10. Air user device for use in a mobile communication system, comprising: a receiving unit that receives access restriction information broadcast from a restricted cell to which access to the air user device is restricted and which is used exclusively for the air user device; and a control unit that refrains from accessing the restricted cell based on the access restriction information when the Radio Resource Control (RRC) is idle or inactive.

11. A network node used in a mobile communication system, having a transmitting unit that transmits access restriction information exclusively for the aviation user device in a restricted cell where access to the aviation user device is restricted, wherein the access restriction information is information that prevents the aviation user device, which is in a radio resource control (RRC) idle state or RRC inactive state, from accessing the restricted cell.

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