Communication device, core network device, and communication method

Abstract

A communication device (100) according to an embodiment of the present invention comprises: a transmission unit (111) that transmits, to a core network device (300), an attach request message which includes information indicating having an ability to support a store-and-forward (S & F) mode; a reception unit (112) that receives, from the core network device (300), an attach approval message which includes a list including satellite identification information; and a control unit (120) that performs cell reselection on the basis of the list.

Description

Communication device, core network device, and communication method Cross-reference to related applications

[0001] This application is based on Patent Application No. 2025-017175 filed on February 4, 2025, claims the benefit of its priority, and all the contents of that patent application are incorporated herein by reference.

[0002] This disclosure relates to a communication device, a core network device, and a communication method.

[0003] In a mobile communication system compliant with the technical specifications of 3GPP (Registered Trademark. The same shall apply hereinafter) (Third Generation Partnership Project), which is a standardization project for mobile communication systems, in order to expand IoT (Internet of Things)-NTN (Non-Terrestrial Network) technology, consideration is being given to supporting store-and-forward (S&F) satellite operations.

[0004] A communication device communicates with a base station (hereinafter appropriately referred to as a satellite base station) mounted on a satellite or a high altitude platform station via a service link, which is a wireless link between the communication device and the satellite base station. Also, the satellite base station communicates with a base station installed on the surface of the earth (hereinafter appropriately referred to as a gateway base station) via a feeder link, which is a wireless link between the satellite base station and the gateway base station. Note that the gateway base station provides connectivity to the satellite base station using the feeder link.

[0005] In S&F satellite operations, even when one of the service link and the feeder link is unavailable, by the satellite base station storing information, the communication opportunity between the communication device and the satellite base station can be increased compared to the case where communication between the communication device and the satellite base station is performed only when both the service link and the feeder link are available.

[0006] Here, it is proposed that a list of satellite information, including satellite identification information (hereinafter referred to as a satellite ID list as appropriate), be set from the core network device (specifically, the Mobility Management Entity (MME)) to the communication device.

[0007] "R2-2411197" (LS on Satellite IDs for store-and-forward operation)

[0008] The communication device according to the first embodiment includes a transmitting unit that transmits an attach request message to a core network device that includes information indicating that it has the capability to support store-and-forward (S&F) mode; a receiving unit that receives an attach approval message from the core network device that includes a list including satellite identification information; and a control unit that performs cell reselection based on the list.

[0009] The core network device according to the second embodiment includes a control unit. The control unit performs the following processes: receiving an attach request message from a communication device that includes information indicating that it has the capability to support store-and-forward (S&F) mode; and sending an attach approval message to the communication device that includes satellite identification information and includes a list used to perform cell reselection.

[0010] A third communication method is performed by a communication device. The communication method comprises the steps of: sending an attach request message to a core network device that includes information indicating that it has the capability to support store-and-forward (S&F) mode; receiving an attach approval message from the core network device that includes a list including satellite identification information; and performing cell reselection based on the list.

[0011] The purpose, features, and advantages of this disclosure will become clearer with reference to the attached drawings and the detailed description below. Figure 1 is a diagram showing the configuration of a mobile communication system according to an embodiment. Figure 2 is a diagram showing an example of the configuration of a protocol stack according to an embodiment (part 1). Figure 3 is a diagram showing an example of the configuration of a protocol stack according to an embodiment (part 2). Figure 4 is a diagram illustrating an example of a scenario according to an embodiment. Figure 5 is a diagram showing the configuration of a UE according to an embodiment. Figure 6 is a diagram showing the configuration of a base station according to an embodiment. Figure 7 is a sequence diagram illustrating a first example of operation of the embodiment. Figure 8 is a sequence diagram illustrating a second example of operation of the embodiment. Figure 9 is a sequence diagram illustrating a third example of operation of the embodiment.

[0012] 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.

[0013] There are concerns that the operation of satellite identification lists may not be effectively utilized because the procedures for such lists are not defined. One of the objectives of this disclosure is to provide communication equipment, core network equipment, and communication methods that enable the effective utilization of satellite identification lists.

[0014] (System Configuration) First, the configuration of the mobile communication system 1 according to this embodiment will be described with reference to Figure 1. The mobile communication system 1 is, for example, a system that conforms to the 3GPP Technical Specifications (TS). In the following, the mobile communication system 1 will be described primarily as an example of a 5th Generation System (5G system) of the 3GPP standard, that is, a mobile communication system based on NR (New Radio) radio access.

[0015] The mobile communication system 1 includes a network 10 and a user equipment (UE) 100 that communicates with the network 10. The network 10 includes an NG-RAN (Next Generation Radio Access Network) 20, which is a 5G radio access network, and a 5GC (5G Core Network) 30, which is a 5G core network. Furthermore, the mobile communication system 1 may have, as the network 10 in the 4th Generation System (4G system) and / or LTE (Long Term Evolution) system of the 3GPP standard, an E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) and a core network called EPC (Evolved Packet Core).

[0016] UE100 is a communication device that communicates via base station 200. UE100 may be a device used by a user. UE100 may be a mobile device such as a smartphone, tablet, notebook PC, communication module, or communication card. UE100 may be a vehicle (e.g., car, train, etc.) or a device installed therein. UE100 may be a transport vehicle other than a vehicle (e.g., ship, airplane, etc.) or a device installed therein. UE100 may be a sensor or a device installed thereon. Note that UE100 may also be called by other names such as terminal, terminal device, mobile station, mobile terminal, mobile device, mobile unit, subscriber station, subscriber terminal, subscriber device, subscriber unit, wireless station, wireless terminal, wireless device, wireless unit, remote station, remote terminal, remote device, or remote unit. Furthermore, UE100 is just one example of a terminal, and terminals may include factory equipment, etc. Furthermore, UE100 may be a BL (Bandwidth reduced Low complexity) UE, an IoT UE, an IoT device, etc.

[0017] NG-RAN20 includes a plurality of base stations 200. Each base station 200 manages at least one cell. One or more base stations 200 may correspond to one or more cells. A base station 200 may be replaced by a cell, and a cell may be replaced by a base station 200. A cell constitutes the smallest unit of a communication area. One cell belongs to one frequency (carrier frequency). The term "cell" may represent a radio communication resource, or it may represent a communication target of UE100. Each base station 200 can perform radio communication with UE100 located within its own cell. Base stations 200 communicate with UE100 using the RAN protocol stack. Details of the protocol stack will be described later. Base stations 200 are also connected to other base stations 200 (which may be called adjacent base stations) via the Xn interface. Base stations 200 communicate with adjacent base stations via the Xn interface. Furthermore, base station 200 provides NR user plane and control plane protocol termination for UE100 and is connected to 5GC30 via NG interface. Such NR base station 200 is sometimes referred to as gNodeB (gNB). In E-UTRAN, base station 200 may be referred to as eNB (evolved Node-B). eNB communicates with neighboring eNBs via X2 interface. Base station 200 may include satellite base station 201 and gateway base station 202, which are described later.

[0018] 5GC30 includes a core network device 300. The core network device 300 includes, for example, an AMF (Access and Mobility Management Function) and / or a UPF (User Plane Function). The AMF manages the mobility of the UE 100. The UPF provides functions specialized for U-plane processing. The AMF and UPF are connected to the base station 200 via an NG interface. In EPC, the core network device 300 also includes, for example, an MME (Mobility Management Entity) and / or an S-GW (Serving Gateway). The MME manages the mobility of the UE 100. The S-GW controls data transfer. The MME / S-GW300 is connected to the eNB via the S1 interface.

[0019] (Example of protocol stack configuration) Next, an example of the protocol stack configuration according to this embodiment will be described with reference to Figures 2 and 3.

[0020] As shown in Figure 2, in the control plane, the protocol for the radio section between UE100 and base station 200 has 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 RRC (Radio Resource Control) layer. As shown in Figure 3, in the user plane, the protocol for the radio section between UE100 and base station 200 has a PHY layer, a MAC layer, an RLC layer, and a PDCP layer. As shown in Figure 3A, in 5G, an SDAP (Service Data Adaptation Protocol) layer is provided as a layer above the PDCP layer. As shown in Figure 3B, 4G does not have an SDAP layer.

[0021] The PHY layer performs encoding and decoding, modulation and demodulation, antenna mapping and demapping, and resource mapping and demapping. Data and control information are transmitted between the PHY layer of UE100 and the PHY layer of base station 200 via a physical channel.

[0022] The MAC layer performs data priority control, retransmission processing using Hybrid ARQ (HARQ), and random access procedures. Data and control information are transmitted between the MAC layer of UE100 and the MAC layer of base station 200 via the transport channel. The MAC layer of base station 200 includes a scheduler. The scheduler determines the transport format for the uplink and downlink (transport block size, modulation and coding scheme (MCS)) and the resources to be allocated to UE100.

[0023] 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 base station 200 via a logical channel.

[0024] The PDCP layer performs header compression / decompression, encryption / decryption.

[0025] The SDAP (Service Data Adaptation Protocol) layer maps IP flows, which are the units in which the core network performs QoS (Quality of Service) control, to wireless bearers, which are the units in which the AS (Access Stratum) performs QoS control.

[0026] 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. RRC signaling for various settings is transmitted between the RRC layer of UE100 and the RRC layer of base station 200. If there is an RRC connection between the RRC layer of UE100 and the RRC layer of base station 200, UE100 is in the RRC connected state. If there is no RRC connection between the RRC layer of UE100 and the RRC layer of base station 200, UE100 is in the RRC idle state. If the RRC connection between the RRC layer of UE100 and the RRC layer of base station 200 is suspended, UE100 is in the RRC inactive state.

[0027] In the control plane, the NAS layer, located above the RRC layer in UE100, performs session management and mobility management for UE100. NAS signaling is transmitted between the NAS layer of UE100 and the NAS layer of the core network device 300.

[0028] Furthermore, the UE100 has an application layer and other components in addition to the wireless interface protocol.

[0029] (Wireless Frame Configuration) In a 5G system, downlink and uplink transmissions are composed within wireless frames with a duration of 10ms. For example, a wireless frame is represented by a System Frame Number (SFN) from 0 to 1023. For example, a wireless frame consists of 10 subframes. For example, one subframe may be 1ms long. Also, one subframe may consist of one or more slots. For example, the number of symbols that make up one slot is usually 14 for a Cyclic Prefix (CP) and 12 for an extended CP. Also, the number of slots that make up one subframe changes according to the set subcarrier interval. For example, for a normal CP, if the subcarrier interval is set to 15 kHz, the number of slots per subframe is 1 (i.e., 14 symbols); if the subcarrier interval is set to 30 kHz, the number of slots per subframe is 2 (i.e., 28 symbols); if the subcarrier interval is set to 60 kHz, the number of slots per subframe is 4 (i.e., 56 symbols); and if the subcarrier interval is set to 120 kHz, the number of slots per subframe is 8 (i.e., 112 symbols). Also, for an extended CP, if the subcarrier interval is set to 60 kHz, the number of slots per subframe is 4 (i.e., 48 symbols). In other words, the number of slots constituting one subframe is determined based on the subcarrier interval set by the base station 200. Also, the number of symbols constituting one subframe is determined based on the subcarrier interval set by the base station 200. In other words, the number of symbols constituting a 1 ms subframe is determined based on the subcarrier interval set by the base station 200, and the length (length in the time direction) of each symbol changes. In a 4G system, each subframe consists of two slots aligned in the time direction. Each subframe has a length of 1 ms. Each slot has a length of 0.5 ms. Each subframe contains multiple symbols in the time direction.

[0030] (Assumed Scenario) The assumed scenario will be explained with reference to Figure 4. In the mobile communication system 1, network 10 supports wireless access via a non-terrestrial network (NTN). As shown in Figure 4, the NTN provides non-terrestrial access through satellite base station 201 and gateway base station 202.

[0031] UE100 and satellite base station 201 communicate via a service link. The service link is a wireless link between UE100 and satellite base station 201. Satellite base station 201 and gateway base station 202 communicate via a feeder link. The feeder link is a wireless link between satellite base station 201 and gateway base station 202. Note that satellite base station 201 and gateway base station 202 may function as a single base station 200. As a single base station 200, it may communicate with UE100 via the Uu interface, or with the core network device 300 via a predetermined interface (for example, the S1 interface).

[0032] The satellite base station 201 may be referred to as the NTN payload. The NTN payload may be a network node that provides connectivity between the service link and the feeder link. The NTN payload may be a network node mounted on a satellite or high-altitude platform station. The NTN payload may be a transport network layer (TNL) node. The satellite may be a space-born vehicle that carries the NTN payload and orbits the Earth.

[0033] The gateway base station 202 may be referred to as an NTN gateway. The NTN gateway may be a node that provides connectivity to NTN payloads using a feeder link. The NTN gateway may be a ground station located on the Earth's surface. The NTN gateway may be a TNL node.

[0034] Incidentally, in mobile communication systems that comply with the technical specifications of 3GPP, a standardization project for mobile communication systems, support for store-and-forward (S&F) satellite operation is being considered to extend IoT-NTN technology. In S&F satellite operation, even if one of the service link between UE100 and base station 200 (specifically, satellite base station 201) or the feeder link between satellite base station 201 and core network (e.g., core network equipment 300) is unavailable, the satellite base station 201 can store information, thereby increasing communication opportunities compared to the case where communication only occurs when both the service link and feeder link are available.

[0035] Here, it has been proposed that a list of satellite information, including satellite identification information (hereinafter referred to as the satellite ID list), be set from the core network device (specifically, the Mobility Management Entity (MME)) to the communication device. However, the operation of the satellite ID list is not specified, raising concerns that the satellite ID list may not be effectively utilized.

[0036] (Configuration of User Device) Referring to Figure 5, the configuration of the UE100 according to this embodiment will be described. The UE100 includes a communication unit 110 and a control unit 120.

[0037] The communication unit 110 performs wireless communication with the base station 200 by transmitting and receiving radio signals to and from the base station 200. The communication unit 110 has at least one transmitting unit 111 and at least one receiving unit 112. The transmitting unit 111 and the receiving unit 112 may be configured to include a plurality of antennas and an RF (Radio Frequency) circuit. The antenna converts a signal into radio waves and radiates the radio waves into space. The antenna also receives radio waves in space and converts the radio waves into signals. The RF circuit performs analog processing of the signals transmitted and received via the antenna. The RF circuit may include a high-frequency filter, an amplifier, a modulator, and a low-pass filter, etc.

[0038] The control unit 120 performs various controls on the UE 100. The control unit 120 controls communication with the base station 200 via the communication unit 110. The operations of the UE 100 described above and below may be operations controlled by the control unit 120. The control unit 120 may include at least one processor capable of executing a program and a memory for storing the program. The processor may execute the program to perform the operations of the control unit 120. The control unit 120 may include a digital signal processor that performs digital processing of signals transmitted and received via the antenna and RF circuit. This digital processing includes processing of the RAN protocol stack. The memory stores the program executed by the processor, parameters related to the program, and data related to the program. Memory may include at least one of ROM (Read Only Memory), EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory), RAM (Random Access Memory), and flash memory. All or part of the memory may be contained within the processor.

[0039] The control unit 120 may include, for example, an RRC processing unit 121 that performs processing in the RRC layer and a NAS processing unit 122 that performs processing in the NAS layer. Therefore, the operation of the RRC processing unit 121 and the NAS processing unit 122 may be the operation of the control unit 120. Furthermore, the operation of the control unit 120 in the RRC layer may be the operation of the RRC processing unit 121, and the operation of the control unit 120 in the NAS layer may be the operation of the NAS processing unit 122.

[0040] (Base station configuration) Referring to Figure 6, the configuration of the base station 200 according to this embodiment will be described. The base station 200 has a communication unit 210, a network communication unit 220, and a control unit 230.

[0041] The communication unit 210, for example, receives a radio signal from the UE 100 and transmits a radio signal to the UE 100. The communication unit 210 has at least one transmitting unit 211 and at least one receiving unit 212. The transmitting unit 211 and the receiving unit 212 may include an RF circuit. The RF circuit performs analog processing of the signals transmitted and received via the antenna. The RF circuit may include a high-frequency filter, an amplifier, a modulator, a low-pass filter, etc.

[0042] The network communication unit 220 transmits and receives signals to and from the network. For example, the network communication unit 220 receives signals from an adjacent base station connected via the Xn interface (or X2 interface), which is an inter-base station interface, and transmits signals to the adjacent base station. The network communication unit 220 also receives signals from the core network device 300 connected via the NG interface (or S1 interface), and transmits signals to the core network device 300.

[0043] The control unit 230 performs various controls on the base station 200. For example, the control unit 230 controls communication with the UE 100 via the communication unit 210. The control unit 230 also controls communication with nodes (e.g., adjacent base stations, core network devices 300) via the network communication unit 220. The operations of the base station 200 described above and below may be operations controlled by the control unit 230. The control unit 230 may include at least one processor capable of executing programs and a memory for storing programs. The processor may execute programs to perform the operations of the control unit 230. The control unit 230 may include a digital signal processor that performs digital processing of signals transmitted and received via the antenna and RF circuit. This digital processing includes processing of the RAN protocol stack. The memory stores programs executed by the processor, parameters related to the programs, and data related to the programs. All or part of the memory may be contained within the processor.

[0044] The configurations of the satellite base station 201 and the gateway base station 202 may be the same as those of the base station 200 described above.

[0045] (First Operation Example) Referring to FIG. 7, the first operation example will be described. Some of the previous explanations may be omitted.

[0046] Note that, for UE100, communication with the satellite base station 201 (specifically, satellite base station 201A / satellite base station 201B) may be communication with a cell (specifically, the cell of satellite base station 201A / the cell of satellite base station 201B). Therefore, for UE100, reception of information / messages, etc. from the satellite base station 201 may be reception of information / messages, etc. from a cell, and transmission of information / messages, etc. to the satellite base station 201 may be transmission of information / messages, etc. to a cell.

[0047] Step S101: UE100 may execute, for example, an attach procedure. The transmission unit 111 of UE100 may transmit an attach request message to the core network device 300 via the satellite base station 201A. The network communication unit of the core network device 300 may receive the attach request message from UE100 via the satellite base station 201A. Note that, before transmitting to the core network device 300, UE100 may execute a process of establishing an RRC connection with the satellite base station 201A.

[0048] The NAS processing unit 122 may execute control to transmit an attach request message to the core network device 300 via the satellite base station 201. The NAS processing unit 122 may include, in the attach request message, capability information indicating that UE100 has the ability to support a satellite identification list. Thereby, the NAS processing unit 122 can execute a process of transmitting the capability information to the core network device 300 in the NAS layer. Also, the NAS processing unit 122 may include, in the attach request message, capability information indicating that UE100 has the ability to support S&F.

[0049] The control unit of the core network device 300 may receive capability information based on the receipt of an attach request message. If the capability information indicates that UE 100 has the capability to support a satellite identification list, the control unit of the core network device 300 may include the satellite identification list in the attach approval message. If the capability information indicates that UE 100 has the capability to support S&F, the control unit may include the satellite identification list in the attach approval message. Therefore, capability information indicating that UE 100 has the capability to support S&F may also indicate that UE 100 supports a satellite identification list.

[0050] Step S102: The core network device 300 may send an attach authorization message, including a satellite identification list, to the UE 100 via the satellite base station 201A. Accordingly, the transmitting unit 211 of the satellite base station 201 may send the satellite identification list to the UE 100. The receiving unit 112 of the UE 100 may receive the attach authorization message, including the satellite identification list, from the UE 100 via the satellite base station 201A. As a result, the NAS processing unit 122 receives the satellite base station list from the core network device 300. The control unit 120 of the UE 100 may perform processing at the NAS layer to receive from the core network device 300.

[0051] The satellite identification list may be, for example, a list of information for identifying a satellite (hereinafter referred to as satellite identification information). Accordingly, the satellite identification list may contain one or more satellite identification information. The satellite identification information may contain at least one of the following: (a) The satellite identification information may contain an identifier for the satellite base station 201 and / or an identifier for a cell managed by the satellite base station 201 (e.g., a physical cell identifier). (b) The satellite identification information may contain a satellite identifier applicable to a specific cell used to associate with satellite auxiliary information for adjacent cell measurements (e.g., satelliteID). (c) The satellite identification information may contain information about when the satellite provides cover (e.g., serviceInfo). (d) The satellite identification information may contain a specific identifier for identifying information in relation to information in a specific system information message (or a specific type of system information block) as described below.

[0052] The satellite identification list may also include other information relating to the satellite base station 201. The satellite identification information may include, for example, information associated with the satellite identification information, such as information indicating the frequency, information indicating the location of the satellite base station, and / or information indicating the speed of the satellite base station.

[0053] The control unit of the core network device 300 may include information indicating the expiration date of the satellite identification list (hereinafter referred to as "expiration date information") along with the satellite identification list in the attach approval message. Alternatively, the control unit of the core network device 300 may include the expiration date information in the satellite identification list. The expiration date information may also be information indicating the expiration date of each satellite identification information. In this case, each satellite identification information may be associated with the expiration date information.

[0054] Expiry information may include, for example, at least one of the following: information indicating the start of the expiration period, information indicating the end of the expiration period, and information indicating the duration of the expiration period. Expiry information may also indicate the expiration period in terms of time. Expiry information may also include a timer value for measuring the expiration period.

[0055] The control unit 120 of UE100 may recognize the state of UE100 as recognized by the satellite base station 201 and / or the background core network device 300, based on the satellite identification list. For example, the control unit 120 may consider the state of UE100 at the satellite base station 201 and / or the core network device 300, as indicated by the satellite identification list (and the satellite identification information contained therein), to be (a1) that it maintains the context (UE context) of UE100, (a2) that it is in the EMM-REGISTERED state and the ECM-IDLE state, or (a3) ​​that, if an RRC connection is established, it is in the EMM-REGISTERED state and the ECM-CONNECTED state. On the other hand, the control unit 120 may consider the state of UE 100 at the satellite base station 201 and / or core network device 300 that is not indicated by the satellite identification list to be (b1) not retaining the context of UE 100 (specifically, the UE context), (b2) being in the EMM-DEREGISTERED state, or (b3) being in the EMM-REGISTERED state but outside the logical area (e.g., tracking area, RAN paging area, etc.) that manages the communication targets of UE 100.

[0056] The EMM state (EPS (Evolved Packet System) mobility management state) has two states: EMM-DEREGISTERED and EMM-REGISTERED. In the EMM-DEREGISTERED state, the EMM context of the core network device 300 (e.g., MME) does not need to hold valid location or routing information for UE100. Since the location of UE100 is unknown, the core network device 300 does not need to be able to reach UE100. Some UE contexts may remain stored in UE100 and the core network device 300, for example, to avoid the execution of the AKA procedure for each attach procedure. On the other hand, in the EMM-REGISTERED state, the EMM context of the core network device 300 may hold valid location or routing information for UE100. In this state, the UE context may be stored in the UE 100 and the core network device 300.

[0057] The ECM state (EPS connection management state) has two states: ECM-IDLE and ECM-CONNECTED. The ECM-IDLE state is when there is no NAS signaling connection between UE100 and the network. In the ECM-IDLE state, a UE context does not need to exist in the wireless access network (e.g., E-UTRAN), except for UE100 where the RRC connection is suspended. The ECM-CONNECTED state is when a NAS signaling connection is established between UE100 and the network. In the ECM-CONNECTED state, a UE context may exist in the wireless access network.

[0058] The states of UE100 described above may be replaced with corresponding states of other generations (e.g., 5G systems). For example, the EMM-DEREGISTERED state may be the RM (Registration Management)-DEREGISTERED state, and the EMM-REGISTERED state may be the RM-REGISTERED state. The ECM-IDLE state may be the CM (Connection Management)-IDLE state, and the ECM-CONNECTED state may be the CM-CONNECTED state.

[0059] Furthermore, the satellite identification information included in the satellite identification list may only indicate satellite base stations 201 performing S&F satellite operations (hereinafter referred to as satellite base stations 201 in S&F mode).

[0060] Step S103: The control unit 120 may perform a process to notify the RRC layer of the satellite identification list from the NAS layer. The NAS processing unit 122 may notify the RRC processing unit 121 of the satellite identification list.

[0061] The NAS processing unit 122 may notify the RRC processing unit 121 of the satellite identification list based on the timing of its receipt. This allows the RRC processing unit 121 to obtain the latest satellite identification list. The NAS processing unit 122 may also notify the RRC processing unit 121 of the satellite identification list at any time. The NAS processing unit 122 may also notify the RRC processing unit 121 of the satellite identification information. Furthermore, the NAS processing unit 122 may also notify the RRC processing unit 121 of the expiration date information.

[0062] Step S104: The control unit 120 may determine whether or not to perform monitoring of a specific system information (SI) message (for example, also referred to as a specific system information block (SIB)). The control unit 120 may determine whether or not to perform monitoring of a specific SI message based, for example, on a satellite identification list.

[0063] The RRC processing unit 121 may, for example, determine whether the satellite identification list is valid or not. The RRC processing unit 121 may determine whether the satellite identification list is valid or not based on the expiration date information.

[0064] The RRC processing unit 121 may determine that the satellite identification list is valid if, for example, the expiration date indicated by the expiration date information has not expired. On the other hand, the RRC processing unit 121 may determine that the satellite identification list is not valid if, for example, the expiration date indicated by the expiration date information has expired.

[0065] Furthermore, if the expiration date information indicates a timer value, the RRC processing unit 121 may set a timer for measuring the expiration date. The RRC processing unit 121 may, for example, start the timer based on the reception of the satellite identification list. The RRC processing unit 121 may determine that the satellite identification list is valid if the timer is running or stopped. On the other hand, the RRC processing unit 121 may determine that the satellite identification list is not valid if the timer has expired.

[0066] The RRC processing unit 121 may perform a process to monitor specific SI messages containing satellite identification information if the satellite identification list is valid. Therefore, the control unit 120 may perform a process to monitor specific SI messages based on the satellite identification list at the RRC layer. In this example, assuming the satellite identification list is valid, the control unit 120 (RRC processing unit 121) may perform the following operations.

[0067] When the RRC processing unit 121 performs monitoring of a specific SI message, it may determine whether it has stored valid scheduling information for that specific SI message (specific SIB). If the RRC processing unit 121 has stored valid scheduling information, it may skip the process in step S105.

[0068] If the RRC processing unit 121 has stored valid scheduling information and the information included in the valid scheduling information (for example, information indicating whether an SI message is being broadcast (for example, si-BroadcastStatus)) indicates a broadcast (for example, "broadcasting"), the RRC processing unit 121 may execute the process in step S107. On the other hand, if the information included in the valid scheduling information does not indicate a broadcast (for example, "notBroadcasting"), the RRC processing unit 121 may execute the process in step S106.

[0069] The control unit 120 may also perform the determination in this step if it becomes impossible to communicate with the cells of the satellite base station 201A. The control unit 120 may also perform the determination in this step if it changes the connection destination depending on the situation, for example, the communication quality (e.g., received power, radio wave quality, etc.) in communication with the satellite base station 201A (or its cells). The change of connection destination may be, for example, an operation based on cell (re)selection, handover, or an operation based on switching modes related to S&F satellite operation. Specifically, the control unit 120 may perform the processing in step S104 in at least one of the following cases: (i) when cell (re)selection is performed and / or when cell (re)selection is completed; (ii) when a handover becomes necessary and / or when a handover is completed; (iii) when satellite base station 201A switches from the real-time mode described later to the mode in which S&F satellite operation is performed and / or when an adjacent satellite base station 201B (or adjacent cell) switches from the mode in which S&F satellite operation is performed to the real-time mode. After performing the determination in step S104, the control unit 120 may trigger the execution of any of the processes in steps S105 to S107 if any of the cases (i) to (iii) above are met.

[0070] Step S105: The transmitting unit 211 of the satellite base station 201A may transmit a system information block type 1 (SIB1) message by broadcast. The control unit 120 (RRC processing unit 121) of the UE 100 may perform the process of receiving the SIB1. The receiving unit 112 of the UE 100 may receive the SIB1 from the satellite base station 201A.

[0071] SIB1 may contain scheduling information for a specific SI message (a specific SIB). If SIB1 contains scheduling information for a specific SI message (a specific SIB), the RRC processing unit 121 may execute the process in step S107. On the other hand, if SIB1 does not contain scheduling information for a specific SIB, the RRC processing unit 121 may execute the following process.

[0072] A specific SI message (specific SIB) may be a message containing one or more satellite identification information. A specific SIB may be a specific type of SIB (referred to as SIBX as appropriate). A specific SIB may be at least one of the following: an SIB containing satellite auxiliary information for a serving cell (e.g., SIB31), an SIB containing satellite auxiliary information for predicting discontinuous coverage (e.g., SIB32), or an SIB containing satellite auxiliary information for an adjacent cell (e.g., SIB33). One or more satellite identification information may be included in the satellite auxiliary information.

[0073] Step S106: The RRC processing unit 121 may execute a process to send an SI request to the satellite base station 201A in order to request the transmission (broadcast) of a specific SI message. The transmission unit 111 may send the SI request to the satellite base station 201A. The receiving unit 212 of the satellite base station 201A may receive the SI request from the UE 100. In response to receiving the SI request, the satellite base station 201A may start transmitting a specific SIB. The satellite base station 201A may also transmit a specific SIB in response to SI requests from other UE 100s.

[0074] Step S107: The transmitting unit 211 of the satellite base station 201A may transmit a specific SIB by broadcast. The receiving unit 112 of the UE 100 may receive a specific SIB from the satellite base station 201A. The RRC processing unit 121 may perform the process of receiving a specific SIB from the satellite base station 201A.

[0075] Step S108: The control unit 120 may perform a determination of satellite identification information between the satellite identification list and a specific SI message. The control unit 120 may perform a process at the RRC layer to determine whether one or more satellite identification information included in the satellite identification list is included in the specific SI message. Accordingly, the RRC processing unit 121 may determine whether at least one of the one or more satellite identification information included in the satellite identification list matches. The RRC processing unit 121 may compare the satellite identification information included in the satellite identification list with the satellite identification information included in the specific SIB. The RRC processing unit 121 may, for example, perform the process in step S109 based on the comparison result. The control unit 120 may perform the determination process in step S108 triggered by the reception of a specific SI message, and perform the process in step S109 triggered by the execution of the determination process.

[0076] Furthermore, the control unit 120 may perform the process in step S109 from the RRC layer to the NAS layer when changing the connection destination. The control unit 120 may perform the process in step S109 when changing the connection destination, for example, depending on the communication quality (e.g., received power, radio wave quality, etc.) in communication with the satellite base station 201A (or its cell). Specifically, the control unit 120 may perform the process in step S109 in at least one of the following cases: (i) when cell (re)selection is performed and / or when cell (re)selection is completed; (ii) when a handover becomes necessary and / or when a handover is completed; (iii) when a switch occurs in which the satellite base station 201A switches from the real-time mode described later to the mode in which S&F satellite operation is performed and / or when a switch occurs in which the adjacent satellite base station 201B (or adjacent cell) switches from the mode in which S&F satellite operation is performed to the real-time mode.

[0077] Step S109: The control unit 120 may perform a process to notify the NAS layer of the determination result from the RRC layer. The control unit 120 may perform a process to notify the determination result by any of the following methods.

[0078] Firstly, the control unit 120 may, for example, execute a process to notify the determination result only if one or more satellite identification information included in the satellite identification list is not included in (or is included in) a specific SI message. The RRC processing unit 121 may, for example, notify the NAS processing unit 122 of the determination result if at least one of the satellite identification information included in the satellite identification list is not included in (or is included in) a specific SIB. In this case, the RRC processing unit 121 does not need to notify the NAS processing unit 122 of the determination result if all of the satellite identification information included in the satellite identification list is included in (or not included in) a specific SIB.

[0079] Alternatively, the RRC processing unit 121 may notify the NAS processing unit 122 of the determination result only if all of the satellite identification information included in the satellite identification list is not included in (or is included in) a specific SIB. In this case, the RRC processing unit 121 does not need to notify the NAS processing unit 122 of the determination result if at least one of the satellite identification information included in the satellite identification list is included in (or is not included in) a specific SIB.

[0080] Alternatively, the RRC processing unit 121 may notify the NAS processing unit 122 of the determination result only if a predetermined number of satellite identification information included in the satellite identification list is not included in (or is included in) a specific SIB. In this case, the RRC processing unit 121 does not need to notify the NAS processing unit 122 of the determination result if less than a predetermined number of satellite identification information included in the satellite identification list is included in (or is not included in) a specific SIB. The control unit 120 may receive information for setting the predetermined number from the satellite base station 201A or from the core network device 300. The information for setting the predetermined number may be included in a specific SIB, in the satellite identification list, or in a message that includes the satellite identification list.

[0081] Secondly, the control unit 120 may perform a process to notify the determination result regardless of the determination result. If the RRC processing unit 121 has a satellite identification list, it may notify the NAS processing unit 122 of the determination result based on the reception of a specific SIB.

[0082] Thirdly, the control unit 120 may perform a process to notify the determination result based on the priority of the satellite base station 201 and / or the cells of the satellite base station 201. The RRC processing unit 121 may perform a process to notify the determination result based on information indicating the priority of the satellite base station 201 and / or the cells of the satellite base station 201 (hereinafter referred to as priority information).

[0083] The RRC processing unit 121 may, for example, perform a process to notify the determination results for high-priority satellite base stations 201 and / or cells of satellite base stations 201. The RRC processing unit 121 may also perform a process to not notify the determination results for low-priority satellite base stations 201 and / or cells of satellite base stations 201. Therefore, the priority information may indicate satellite base stations 201 (or cells) that are subject to (or are not subject to) notification of the determination results.

[0084] The RRC processing unit 121 may receive priority information from the satellite base station 201A. The priority information may be included in a specific SIB. The priority information may be associated with each satellite identification information included in a specific SIB. The NAS processing unit 122 may also receive priority information from the core network device 300. The priority information may be included in a satellite identification list. The priority information may be associated with each satellite identification information included in a specific SIB. The NAS processing unit 122 may notify the RRC processing unit 121 of the priority information along with the satellite identification information.

[0085] The determination result may, for example, indicate that the satellite identification information included in the satellite identification list is included in a particular SIB, or it may indicate that the satellite identification information included in the satellite identification list is not included in a particular SIB.

[0086] The determination result may include satellite identification information that is included in both the satellite identification list and the specific SIB. The determination result may also include information associated with the satellite identification information. The RRC processing unit 121 may notify the NAS processing unit 122 of only the satellite identification information (and the information associated with the satellite identification information) as the determination result. In this case, the NAS processing unit 122 may recognize that the notified satellite identification information is included in both the satellite identification list and the specific SIB.

[0087] The determination result may include satellite identification information that is included in at least one of the satellite identification list and the specific SIB. The determination result may include satellite identification information that is included only in the satellite identification list. The determination result may include satellite identification information that is included only in the specific SIB. The determination result may include information associated with the satellite identification information. The RRC processing unit 121 may notify the NAS processing unit 122 of only the satellite identification information (and the information associated with the satellite identification information) as the determination result. In this case, the NAS processing unit 122 may recognize that the notified satellite identification information is (i) included in at least one of the satellite identification list and the specific SIB, (ii) included only in the satellite identification list, or (iii) included only in the specific SIB.

[0088] The control unit 120 may, for example, determine whether one or more satellite identification information contained in a particular SI message is included in the satellite identification list. Therefore, the satellite identification list and the particular SI message (specific SIB) may be interchangeable.

[0089] Step S110: The NAS processing unit 122 may notify the RRC processing unit 121 of an RRC connection instruction based on the determination result. For example, if the NAS processing unit 122 determines, based on the determination result, that the satellite identification information included in the satellite identification list is included in a specific SIB, it may notify an RRC connection instruction to establish an RRC connection. The RRC connection instruction may include information indicating the satellite base station 201 (or its cell) to which the connection is to be made.

[0090] Step S111: The RRC processing unit 121 may perform processing to establish an RRC connection with another satellite base station 201 or another cell. The RRC processing unit 121 may perform this processing based on an RRC connection instruction from the NAS processing unit 122. The RRC processing unit 121 may perform this processing after receiving an RRC connection instruction, for example, in response to a handover being triggered. The RRC processing unit 121 may also perform this processing without receiving an RRC connection instruction. The RRC processing unit 121 may prioritize a satellite base station 201 (or its cell) indicated by the satellite identification list over the RRC connection destination (e.g., the handover destination).

[0091] Furthermore, the RRC processing unit 121 may, for example, prioritize (re)selecting a cell of the satellite base station 201 indicated by the satellite identification list when cell (re)selection is triggered.

[0092] As described above, the transmission unit 211 of the satellite base station 201 transmits the satellite identification list to the UE 100. The control unit 120 of the UE 100 may perform the following processes at the NAS layer: receiving the satellite identification list from the core network device 300, notifying the RRC layer of the satellite identification list from the NAS layer, and monitoring specific system information messages containing satellite identification information at the RRC layer based on the satellite identification list. The satellite identification list may be used in the process at the UE 100 where it is notified from the NAS layer to the RRC layer and the RRC layer monitors specific SI messages containing satellite identification information. Because the satellite identification list is received at the NAS layer, even if satellite identification information is received at the RRC layer, the RRC processing unit 121 cannot grasp the satellite identification list. Therefore, by notifying the RRC layer of the satellite identification list from the NAS layer, the satellite identification list can be effectively utilized. In this example, the RRC processing unit 121 can recognize the satellite base station 201 (or its cell) notified by the core network device 300 based on the satellite identification list. When the control unit 120 can recognize the satellite base station 201 notified by the core network device 300, it can perform monitoring of specific SI messages, thus enabling effective use of the satellite identification list.

[0093] Furthermore, the control unit 120 may perform a process to monitor specific system information messages when the satellite identification list is valid. This allows the control unit 120 to avoid performing monitoring based on a satellite identification list that may contain incorrect satellite identification information.

[0094] Furthermore, the control unit 120 may perform the following processes at the RRC layer: determine whether one or more satellite identification information included in the satellite identification list is included in a specific SI message, and notify the NAS layer of the result of the determination. This allows the NAS processing unit 122 to determine whether the satellite base station 201 indicated by the satellite identification list is actually discoverable, and to determine whether the satellite identification list can be utilized.

[0095] Furthermore, if one or more satellite identification information is not included in a specific SI message, the control unit 120 may perform a process to notify the NAS layer of the determination result from the RRC layer. This allows the NAS processing unit 122 to understand that the satellite base station 201 indicated by the satellite identification list is actually undetectable, and to determine whether the satellite identification list can be utilized.

[0096] Furthermore, the control unit 120 may perform a process to notify the result of the determination based on the priority of the satellite base station 201. This allows the NAS processing unit 122 to know the determination result for the satellite base station 201 that should be prioritized.

[0097] Furthermore, the control unit 120 may execute a process to notify the NAS layer of the determination result from the RRC layer when changing the connection destination. For example, if the satellite identification information included in the satellite identification list indicates a satellite base station 201 under the control of the core network device 300 that holds the UE context of UE 100, the UE context can be shared among the satellite base stations 201, and therefore, when the satellite base station 201 is selected as the connection destination, a reduction in signaling can be expected. When changing the connection destination, the communication environment of UE 100 changes, so by notifying the determination result at that time, the NAS processing unit 122 can determine whether the satellite identification list can be utilized at the time the communication environment of UE 100 changes.

[0098] Furthermore, the control unit 120 may perform a process at the NAS layer to transmit capability information to the core network device 300 indicating that the UE 100 has the capability to support satellite identification lists. This allows the core network device 300 to determine whether or not the UE 100 supports satellite identification lists and to appropriately determine the targets for transmission of satellite identification lists.

[0099] (Second Operation Example) The second operation example will be explained using Figure 8. Previously explained explanations may be omitted. In the operation example described above, the case in which UE100 monitors a specific SI message containing satellite identification information from satellite base station 201A (its cell). In this operation example, the case in which UE100 monitors a specific SI message (specific SIB) containing satellite identification information from satellite base station 201B (its cell), which is an adjacent satellite base station 201. In addition, this operation example describes a case in which UE100 determines priority based on the satellite identification list.

[0100] Steps S201 to S203: Same as steps S101 to S103.

[0101] Step S204: The transmitting unit 211 of the satellite base station 201A may transmit a specific SIB by broadcast, similar to step S107. Here, the specific SIB may transmit a specific SIB (e.g., SIB33) that includes satellite identification information of an adjacent satellite base station, which is a satellite base station adjacent to the satellite base station 201A.

[0102] The control unit 120 (RRC processing unit 121) may receive a specific SIB from the cell of the satellite base station 201A, similar to step S107. The control unit 120 may also perform the operations of step S105 and / or step S106 in order to acquire the specific SIB.

[0103] Step S205: The control unit 120 (RRC processing unit 121) may determine, similar to step S104, whether to monitor a specific SI message (specific SIB) based on the satellite identification list. In this example, the control unit 120 may determine whether to monitor a specific SIB from a cell of an adjacent satellite base station 201 adjacent to satellite base station 201A (and / or an adjacent cell adjacent to the cell of satellite base station 201A).

[0104] Furthermore, the control unit 120 may determine whether or not to perform monitoring of a specific SIB from satellite base station 201B (or its cell) based on the result of determining whether or not to perform monitoring of a specific SIB from the cell where UE 100 is camped or from the cell of satellite base station 201A, which is the serving cell of UE 100. The control unit 120 may determine to perform monitoring of a specific SIB from satellite base station 201B (or its cell) if satellite base station 201B is indicated by the satellite identification information included in the satellite identification list. On the other hand, the control unit 120 may determine not to perform monitoring of a specific SIB from satellite base station 201B (or its cell) if satellite base station 201B is not indicated by the satellite identification information included in the satellite identification list. Alternatively, the control unit 120 may determine that it will monitor the specific SIB from the satellite base station 201B (or its cells) if the number of satellite base stations 201 (or their cells) indicated by the specific SIB and satellite identification list is small (i.e., less than a predetermined number), that is, if a predetermined number or more of the satellite identification information included in the satellite identification list is not included in the specific SIB.

[0105] Step S206: Similar to step S105, the transmitting unit 211 of the satellite base station 201B may transmit the SIB1 message by broadcast. The control unit 120 (RRC processing unit 121) of the UE 100 may perform the process of receiving the SIB1. The receiving unit 112 of the UE 100 may receive the SIB1 from the satellite base station 201B.

[0106] Step S207: Similar to step S106, the control unit 120 may perform the process of transmitting the SI request to the satellite base station 201B. The transmission unit 111 may transmit the SI request to the satellite base station 201B. The receiving unit 212 of the satellite base station 201B may receive the SI request from the UE 100.

[0107] Step S208: Similar to step S107, the transmitting unit 211 of the satellite base station 201B may transmit a specific SIB by broadcast. The receiving unit 112 of the UE 100 may receive a specific SIB from the satellite base station 201B.

[0108] Here, the control unit 120 may control the system to receive an SIB (e.g., SIB 31) containing satellite auxiliary information for a serving cell if the satellite identification information included in the satellite identification list indicates a satellite base station 201B. The control unit 120 may also control the system to receive an SIB (e.g., SIB 33) containing satellite auxiliary information for an adjacent cell if the satellite identification information included in the satellite identification list does not indicate a satellite base station 201B. Furthermore, the control unit 120 may control the system to receive an SIB (e.g., SIB 33) containing satellite auxiliary information for an adjacent cell if the number of specific SIBs from satellite base station 201B and satellite base station 201 (or its cells) indicated by the satellite identification list is small (i.e., less than a predetermined number). Therefore, the control unit 120 may control the system to acquire a specific SIB containing satellite identification information for an adjacent satellite base station 201 in order to find (many) satellite base stations indicated by the satellite identification list.

[0109] Furthermore, the control unit 120 may determine whether or not to perform monitoring of a specific SIB from a cell of an adjacent satellite base station 201 adjacent to satellite base station 201B (and / or an adjacent cell adjacent to the cell of satellite base station 201B).

[0110] Step S209: The control unit 120 (RRC processing unit 121) may perform priority determination. The control unit 120 may, for example, determine the priority of the cells to be (re)selected. The control unit 120 may determine the priority of cells when performing cell selection or cell re-selection. The control unit 120 may also determine the priority of the cells to be measured that are candidates for the cell to be handed over. The control unit 120 may determine the priority of cells by the following method.

[0111] Firstly, the control unit 120 may determine at least one of the priority of the cell to be (re)selected and the priority of the cell to be measured, based on the satellite identification list. Therefore, for cells that meet the criteria such as radio wave quality in cell (re)selection and / or handover, the control unit 120 may use the satellite identification list as one of the factors for determining priority, in addition to the conventional selection priority.

[0112] The control unit 120 may determine the priority of a cell based, for example, on whether or not it is a cell associated with satellite identification information included in the satellite identification list. Therefore, the control unit 120 may determine the priority of a cell based on whether or not it is a cell of a satellite base station 201 indicated by satellite identification information included in the satellite identification list.

[0113] The control unit 120 may, for example, set the priority of a cell of the satellite base station 201 indicated by the satellite identification information included in the satellite identification list to be higher than the priority of other cells (i.e., cells of the satellite base station 201 not indicated by the satellite identification information included in the satellite identification list).

[0114] On the other hand, if the satellite base station 201 indicated by the satellite identification information included in the satellite identification list is performing S&F satellite operation, the control unit 120 may set the priority of the cell of the satellite base station 201 lower than the priority of other cells. For example, if the satellite identification information included in the satellite identification list indicates only the satellite base station 201 performing S&F satellite operation, the control unit 120 may set the priority of the cell of the satellite base station 201 lower than the priority of other cells.

[0115] Secondly, the control unit 120 may determine the priority of a cell based on whether or not it is a cell of satellite base station 201 in a mode in which both the service link and the feeder link are available (hereinafter referred to as real-time mode). For example, the control unit 120 may set the priority of a cell of satellite base station 201 in real-time mode higher than the priority of a cell of satellite base station 201 indicated by the satellite identification information included in the satellite identification list. Note that real-time mode may be a mode in which satellite base station 201 is not performing S&F satellite operation. Real-time mode may also be referred to by other names, such as normal mode.

[0116] The control unit 120 may, based on authorization information that permits priority for the cells of the satellite base station 201 in real time mode, set the priority of the cells of the satellite base station 201 in real time mode higher than the priority of the cells of the satellite base station 201 indicated by the satellite identification information included in the satellite identification list.

[0117] The receiving unit 112 may receive authorization information from the network. For example, the receiving unit 112 may receive a satellite identification list containing authorization information from the core network device 300, or it may receive a specific SIB containing authorization information from the satellite base station 201B.

[0118] Furthermore, the control unit 120 may determine, for example, whether a satellite base station 201 (or its cell) is in real-time mode based on a specific SI message (specific SIB). The specific SI message (specific SIB) may include information indicating whether a satellite base station 201 (or its cell) is in real-time mode. The specific SIB may include information indicating whether the satellite base station 201 transmitting the specific SIB is in real-time mode, or it may include information indicating whether an adjacent satellite base station 201 is in real-time mode.

[0119] Furthermore, the control unit 120 may determine whether a satellite base station 201 (or its cell) is in real-time mode based on the satellite identification list. For example, if the satellite identification information included in the satellite identification list indicates only satellite base stations 201 performing S&F satellite operations, the control unit 120 may determine that satellite base stations 201 not indicated by the satellite identification list are in real-time mode.

[0120] The control unit 120 may determine the priority of a cell by at least one of the following methods: a first method (whether or not it is a cell of the satellite base station 201 indicated by the satellite identification list (satellite identification information)) and a second method (i.e., whether or not it is a cell of the satellite base station 201 in real-time mode). The control unit 120 may, for example, determine the priority of a cell by both the first and second methods. Alternatively, the control unit 120 may determine the priority of a cell by the first method regardless of whether or not it is a cell of the satellite base station 201 in real-time mode, or it may determine the priority of a cell by the second method regardless of whether or not it is a cell of the satellite base station 201 indicated by the satellite identification list (satellite identification information).

[0121] The control unit 120 may be configured from the network to determine whether to use the first method or the second method to determine the cell priority. The receiving unit 112 may receive information indicating whether to use the first method or the second method to determine the cell priority. Based on this information, the control unit 120 may determine the method to use to determine the cell priority. The receiving unit 112 may receive a satellite identification list containing this information from the core network device 300, or it may receive a specific SIB containing this information from the satellite base station 201B.

[0122] Step S210: The control unit 120 may perform an action based on the determined priority. The control unit 120 may perform processing on the cells based on the determined priority. The control unit 120 may, for example, select or re-select a cell with a higher priority. The control unit 120 may camp on the (re)selected cell.

[0123] The control unit 120 may also determine a cell with a higher priority as the cell to be measured. The control unit 120 may report the measurement results to the satellite base station 201. The control unit 120 may perform a handover based on the measurement results. The control unit 120 may also determine a cell with a higher priority as the connection destination. The control unit 120 may perform a process to establish an RRC connection with the cell as the connection destination.

[0124] Furthermore, if the control unit 120 cannot find a cell of the satellite base station 201 indicated by the satellite identification information included in the satellite identification list, it may select or determine as the connection destination a cell of the satellite base station 201 that is not indicated in the satellite identification list.

[0125] The receiving unit 112 may receive information that sets the monitoring period for a specific SI message. The receiving unit 112 may receive a satellite identification list containing such information from the core network device 300, or it may receive a specific SIB containing such information from the satellite base station 201B. If the control unit 120 cannot find a cell of satellite base station 201 indicated by the satellite identification information included in the satellite identification list even after the monitoring period has elapsed, it may select or determine as the connection destination a cell of satellite base station 201 that is not indicated by the satellite identification list.

[0126] As described above, the receiving unit 112 of the UE 100 may receive the satellite identification list from the core network device 300. The control unit 120 may determine the priority of the cells based on the satellite identification list. The satellite identification list may be used in the UE 100 to determine the priority of the cells. As a result, the control unit 120 uses the satellite identification list to determine the priority of the cells, making effective use of the satellite identification list.

[0127] Furthermore, the control unit 120 may monitor specific SI messages containing satellite identification information of adjacent satellite base stations 201B based on the satellite identification list. This allows the UE 100 to acquire information on adjacent satellite base stations 201B that may be included in the satellite identification list, thereby enabling effective use of the satellite identification list.

[0128] Furthermore, the control unit 120 may determine the priority of a cell based on whether or not the cell is a cell of a satellite base station indicated by satellite identification information included in the satellite identification list. Since the priority of cells of satellite base stations indicated by the satellite identification list can be changed, the network can control which cells can communicate with the UE 100.

[0129] Furthermore, the control unit 120 may set the priority of a satellite base station cell indicated by the satellite identification information included in the satellite identification list higher than the priority of other cells. For example, if the satellite identification information included in the satellite identification list indicates a satellite base station 201 under the control of the core network device 300 that holds the UE context of UE 100, a reduction in signaling can be expected. As a result, power consumption and wireless resources can be saved.

[0130] Furthermore, the control unit 120 may lower the priority of the satellite base station 201 cell than the priority of other cells when the satellite base station indicated by the satellite identification information included in the satellite identification list is performing S&F satellite operation. This makes it more difficult for the control unit 120 to select a satellite base station 201 that may experience delays, and allows it to preferentially select a satellite base station 201 that can communicate in real time.

[0131] Furthermore, the control unit 120 may determine the priority of the cells to be selected and the priority of the cells to be measured. This allows the control unit 120 to select cells and determine the cells to be measured while taking into account the satellite identification list.

[0132] Furthermore, the control unit 120 may determine the priority of a cell based on whether or not it is a cell of a satellite base station 201 that is in real-time mode with both service links and feeder links available. This allows the control unit 120 to determine the priority of a cell while taking into account satellite base stations 201 that can communicate in real time.

[0133] Furthermore, the control unit 120 may set the priority of satellite base station cells in real-time mode higher than the priority of satellite base station cells indicated by the satellite identification information included in the satellite identification list. This makes it difficult for the control unit 120 to select satellite base station 201 where delays may occur, and allows it to preferentially select satellite base station 201 that can communicate in real time.

[0134] Furthermore, the receiving unit 112 may receive authorization information that grants priority to cells of satellite base stations 201 in real-time mode. Based on the authorization information, the control unit 120 may set the priority of cells of satellite base stations in real-time mode higher than the priority of cells of satellite base stations indicated by satellite identification information included in the satellite identification list. This allows the network to flexibly control satellite base stations 201 communicating with UE 100.

[0135] Furthermore, certain SI messages may include information indicating whether or not the satellite base station 201 is in real-time mode. This allows the UE 100 to explicitly determine whether or not the satellite base station 201 is in real-time mode.

[0136] Furthermore, if the control unit 120 cannot find a cell of the satellite base station 201 indicated by the satellite identification information included in the satellite identification list, it may select or decide to connect to a cell of the satellite base station 201 that is not indicated in the satellite identification list. This allows the control unit 120 to communicate with a satellite base station 201 that is not indicated in the satellite identification list when the satellite identification list is unavailable, thus enabling effective use of the satellite identification list.

[0137] The receiving unit 112 may also receive information that sets the monitoring period for a specific SI message. If the control unit 120 cannot find a cell of the satellite base station 201 indicated by the satellite identification information included in the satellite identification list even after the monitoring period has elapsed, it may select or decide to connect to a cell of the satellite base station 201 that is not indicated in the satellite identification list. This allows the network to flexibly control the possibility of communicating with the satellite base station 201 indicated in the satellite identification list, depending on the length of the monitoring period.

[0138] (Third Operation Example) The third operation example will be explained using Figure 9. Previously explained details may be omitted. This operation example describes the case in which UE100 requests an update to the satellite identification list.

[0139] Step S301: Similar to step S102, the core network device 300 may transmit the satellite identification list to the UE 100 via the satellite base station 201A. The receiving unit 112 of the UE 100 may receive the satellite identification list via the satellite base station 201A. The satellite identification list may be included in the attach approval message or in another message. Accordingly, the network communication unit 220 of the satellite base station 201 receives the satellite identification list from the core network device 300, and the transmitting unit 211 of the satellite base station 201A transmits the satellite identification list to the UE 100.

[0140] Furthermore, as described in Operation Example 1, the core network device 300 may send a message to the UE 100 that includes a satellite identification list and expiration date information for the satellite identification list. The receiving unit 112 of the UE 100 may receive the expiration date information from the core network device 300.

[0141] Step S302: This is the same as step S103.

[0142] Step S303: The transmitting unit 211 of the satellite base station 201A may transmit the expiration date information to the UE 100. The receiving unit 112 of the UE 100 may receive the expiration date information from the satellite base station 201A.

[0143] Step S304: The control unit 120 of the UE100 may determine whether or not to transmit update information for updating the satellite identification list. The control unit 120 may make this determination, for example, by the following method.

[0144] Firstly, the control unit 120 may determine whether or not to transmit update information based on whether or not it can find the satellite base station 201 indicated by the satellite identification information included in the satellite identification list. If the control unit 120 can find the satellite base station 201 indicated by the satellite identification information included in the satellite identification list, it may determine not to transmit update information. On the other hand, if the control unit 120 cannot find the satellite base station 201 indicated by the satellite identification information included in the satellite identification list, it may determine to transmit update information.

[0145] The control unit 120 may, for example, consider that it has found a satellite base station 201 indicated by the satellite identification information if the satellite identification information included in the satellite identification list is included in the satellite identification information included in a particular SIB.

[0146] Secondly, the control unit 120 may determine whether or not to transmit update information based on whether or not the satellite identification list is valid. If the satellite identification list is valid, the control unit 120 may determine not to transmit update information. On the other hand, if the satellite identification list is not valid, the control unit 120 may determine to transmit update information. As explained in the first example of operation, the control unit 120 may determine that the satellite identification list is valid if the expiration date of the satellite identification list has not yet passed. On the other hand, if the expiration date of the satellite identification list has passed, the control unit 120 may determine that the satellite identification list is not valid.

[0147] Furthermore, the control unit 120 may start a timer for measuring the expiration date based on the reception of the satellite identification list. Based on the expiration of the timer, the control unit 120 may determine that the satellite identification list is no longer valid.

[0148] Furthermore, if the control unit 120 cannot find the aforementioned satellite base station 201, it may consider the satellite identification list to be ineffective, on the grounds that the list is not optimal.

[0149] Step S305: The transmitting unit 111 of UE 100 may transmit update information for updating the satellite identification list to the core network device 300 via the satellite base station 201. The core network device 300 receives the update information from UE 100 via the satellite base station 201. Therefore, the receiving unit 212 of the satellite base station 201 receives the update information from UE 100, and the network communication unit 220 of the satellite base station 201 transmits the update information to the core network device 300.

[0150] The transmission unit 111 may, for example, send a NAS message containing update information to the core network device 300. The message containing update information may be, for example, a registration request message, a tracking area update (TAU) request message, or a service request message. Alternatively, the transmission unit 111 may send an existing TAU message that does not contain update information as update information.

[0151] The core network device 300 may generate an updated satellite identification list when it receives update information. The core network device 300 may execute the process in step S306 when it receives update information. Furthermore, if the core network device 300 receives an existing TAU message that does not contain update information, and has sent a satellite identification list to the UE 100 that sent the TAU message, it may consider that TAU ​​message to be update information.

[0152] Step S306: The core network device 300 transmits the updated satellite identification list to the UE 100. The receiving unit 112 of the UE 100 receives the satellite identification list. The control unit 120 of the UE 100 may perform the operations described above based on the updated satellite identification list.

[0153] As described above, the receiving unit 112 of UE 100 may receive the satellite identification list from the core network device. The transmitting unit 111 may transmit update information to the core network device to update the satellite identification list. This allows UE 100 to request the updated satellite identification list. When UE 100 receives the updated satellite identification list from the core network device 300, it can use the latest satellite identification list and effectively utilize the satellite identification list.

[0154] Furthermore, the transmission unit 111 may transmit a TAU message containing update information to the core network device. This reduces the impact on the mobile communication system compared to defining a new message.

[0155] Furthermore, if the transmitting unit 111 cannot find the satellite base station 201 indicated by the satellite identification information included in the satellite identification list, it may transmit update information to the core network device 300. This allows the UE 100 to transmit update information and obtain the latest satellite identification list if the satellite identification list it holds is not optimal for it. The UE 100 can then use the latest satellite identification list to perform mobility control, thus enabling effective utilization of the satellite identification list.

[0156] Furthermore, the transmission unit 111 may transmit update information to the core network device if the satellite identification list is invalid. This allows the UE 100 to transmit update information and obtain the latest satellite identification list if it has an invalid satellite identification list. The UE 100 can then perform mobility control using the latest satellite identification list, thus enabling effective utilization of the satellite identification list.

[0157] Furthermore, the receiving unit 112 may receive a message from the core network device 300 that includes a satellite identification list and information indicating the expiration date of the satellite identification list. The control unit 120 may determine whether or not the satellite identification list is valid based on the information indicating the expiration date. This allows the network to flexibly control the expiration date.

[0158] Furthermore, the control unit 120 may start a timer based on the reception of the satellite identification list. The transmission unit 111 may transmit update information to the core network device based on the timer's expiration. This allows the UE 100 to determine whether or not the satellite identification list is valid.

[0159] (Other Embodiments) In each of the above-described operational examples, the satellite identification list may be transmitted from the core network device 300 to the UE 100 by a message other than the attach approval message. The other message may be, for example, at least one of a tracking area update approval message, a NAS notification message, a paging message, or a registration approval message. Also, in the above-described operational examples, the attach request message may be replaced with a tracking area update request message, a registration request message, and / or a service request message.

[0160] The steps in the operation of each embodiment described above do not necessarily have to be executed chronologically in the order shown in the flowchart or sequence diagram. For example, the steps in the operation may be executed in a different order than that shown in the flowchart or sequence diagram, or they may be executed in parallel. Also, some steps in the operation may be deleted, or further steps may be added to the process. Furthermore, each operation flow described above is not limited to being implemented separately and independently, but can be implemented by combining 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.

[0161] In the embodiments described above, a mobile communication system based on NR was used as an example for the mobile communication system 1. However, the mobile communication system 1 is not limited to this example. The mobile communication system 1 may be a system compliant with LTE or another generation system of the 3GPP standard (e.g., 6th generation). The base station 200 may be an eNB that provides E-UTRA user plane and control plane protocol terminations directed to UE100 in LTE. The mobile communication system 1 may be a system compliant with a TS of a standard other than the 3GPP standard. The base station 200 may be an IAB (Integrated Access and Backhaul) donor or IAB node. The base station 200 may be functionally divided into a CU (Central Unit) and a DU (Distributed Unit).

[0162] A program may be provided that causes a computer to execute each process performed by the UE 100 or base station 200. 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 (Compact Disk Read Only Memory) or a DVD-ROM (Digital Versatile Disc Read Only Memory). Alternatively, the circuits that execute each process performed by the UE 100 or base station 200 may be integrated, and at least a part of the UE 100 or base station 200 may be configured as a semiconductor integrated circuit (chipset, SoC (System On Chip)).

[0163] The core network device 300 may have a control unit and a network communication unit, similar to the base station 200. The control unit may be configured similarly to the control unit 230 of the base station 200. The network communication unit may be configured similarly to the network communication unit 220 of the base station 200.

[0164] In the embodiments described above, "transmit" may mean processing at least one layer in the protocol stack used for transmission, or it may mean physically transmitting a signal wirelessly or via a wire. Alternatively, "transmit" may mean a combination of processing at least one layer and physically transmitting a signal wirelessly or via a wire. Similarly, "receive" may mean processing at least one layer in the protocol stack used for reception, or it may mean physically receiving a signal wirelessly or via a wire. Alternatively, "receive" may mean a combination of processing at least one layer and physically receiving a signal wirelessly or via a wire. Similarly, "obtain / acquire" may mean obtaining information from stored information, obtaining information from information received from another node, or obtaining information by generating it. Similarly, the phrases “based on” and “depending on / in response to” do not mean “based solely on” or “in response to” unless otherwise specified. The phrase “based on” means both “based solely on” and “at least partially on.” Similarly, the phrase “in response” means both “at least partially on” and “in at least partially on.” Similarly, “include” and “comprise” do not mean “include only the listed items,” but rather “may include only the listed items,” or “may include additional items in addition to the listed items.” Similarly, in this disclosure, “or” does not mean exclusive OR, but rather logical OR. Furthermore, any reference to elements using designations such as “first,” “second,” etc., as used in this disclosure does not limit the quantity or order of those elements in general. These designations may be used in this disclosure 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.

[0165] This disclosure is described in accordance with the embodiments, but it is understood that this disclosure is not limited to such embodiments or structures. This disclosure also includes various modifications and variations within the equivalence. In addition, various combinations and forms, as well as other combinations and forms that include only one, more, or fewer of those elements, fall within the scope and concept of this disclosure.

[0166] (Note) The features of the above-described embodiment are noted below.

[0167] (Note 1) A communication device (100) comprising: a transmitting unit (111) that transmits an attach request message to a core network device (300) that includes information indicating that it has the capability to support store-and-forward (S&F) mode; a receiving unit (112) that receives an attach approval message from the core network device (300) that includes a list including satellite identification information; and a control unit (120) that performs cell reselection based on the list.

[0168] (Note 2) The communication device according to Note 1, wherein the control unit performs reselection of the cell based on whether or not it is a cell corresponding to the satellite identification information included in the list.

[0169] (Note 3) The communication device according to Note 1 or 2, wherein the control unit performs reselection of the cell based on whether or not it is a store-and-forward (S&F) satellite cell.

[0170] (Note 4) The communication device according to any one of Notes 1 to 3, wherein the control unit performs reselection of the cell based on whether or not it is a satellite cell in a mode in which both a service link and a feeder link are available.

[0171] (Note 5) The receiving unit receives a system information message, and the system information message includes information indicating whether the satellite is in a mode in which both a service link and a feeder link are available, according to any one of Notes 1 to 4.

[0172] (Note 6) The communication device according to any one of Notes 1 to 5, wherein the control unit cannot find a satellite cell indicated by the satellite identification information included in the list, and selects or determines a satellite cell not indicated in the list as the connection destination.

[0173] (Note 7) A core network device (300) comprising a control unit, the control unit performing the following processes: receiving an attach request message from a communication device (100) that includes information indicating that it has the capability to support store-and-forward (S&F) mode; and sending an attach approval message to the communication device that includes satellite identification information and includes a list used to perform cell reselection.

[0174] (Note 8) A communication method performed by a communication device, comprising the steps of: sending an attach request message to a core network device (300) that includes information indicating that it has the capability to support store-and-forward (S&F) mode; receiving an attach approval message from the core network device (300) that includes a list that includes satellite identification information; and performing cell reselection based on the list.

[0175] (Note 9) A communication device comprising: a receiving unit that receives a satellite identification list from a core network device; and a control unit that determines the priority of a cell based on the satellite identification list.

[0176] (Note 10) The control unit is the communication device described in Note 9, which monitors specific system information messages, including satellite identification information of adjacent satellite base stations, based on the satellite identification list.

[0177] (Note 11) The communication device according to Note 9 or 10, wherein the control unit determines the priority of the cell based on whether or not the cell is a cell of a satellite base station indicated by satellite identification information included in the satellite identification list.

[0178] (Note 12) The communication device according to Note 11, wherein the control unit sets the priority of the satellite base station cell indicated by the satellite identification information included in the satellite identification list higher than the priority of other cells.

[0179] (Note 13) The communication device according to any one of Notes 9 to 12, wherein the control unit lowers the priority of the satellite base station cell to that of other cells when the satellite base station indicated by the satellite identification information included in the satellite identification list performs store-and-forward (S&F) satellite operation.

[0180] (Note 14) The communication device according to any one of Notes 9 to 13, wherein the control unit determines the priority of the cell to be selected and the priority of the cell to be measured, and the control unit determines the priority of the cell based on whether or not it is a cell of a satellite base station in a mode in which both the service link and the feeder link are available.

[0181] (Note 15) The communication device according to Note 14, wherein the control unit sets the priority of the satellite base station cell in the mode higher than the priority of the satellite base station cell indicated by the satellite identification information included in the satellite identification list.

[0182] (Note 16) The communication device according to Note 14 or 15, wherein the receiving unit receives permission information that grants priority to a satellite base station cell in the mode, and the control unit, based on the permission information, sets the priority of the satellite base station cell in the mode higher than the priority of the satellite base station cell indicated by the satellite identification information included in the satellite identification list.

[0183] (Note 17) The communication device according to any one of Notes 14 to 16, wherein the specific system information message includes information indicating whether or not the satellite base station is in the mode.

[0184] (Note 18) The communication device according to any one of Notes 9 to 17, wherein the control unit cannot find a cell of a satellite base station indicated by the satellite identification information included in the satellite identification list, and selects or determines as the connection destination a cell of a satellite base station not indicated by the satellite identification list.

[0185] (Note 19) The communication device according to Note 18, wherein the receiving unit receives information that sets a monitoring period for a specific system information message including satellite identification information of the adjacent satellite base station, and the control unit, if it cannot find a cell of the satellite base station indicated by the satellite identification information included in the satellite identification list even after the monitoring period has elapsed, selects or determines as the connection destination a cell of a satellite base station not indicated by the satellite identification list.

[0186] (Note 20) A base station comprising a transmitting unit for transmitting a satellite identification list to a communication device, wherein the satellite identification list is used by the communication device to determine the priority of cells.

[0187] (Note 21) A communication method performed by a communication device, comprising the steps of: receiving a satellite identification list from a core network device; and determining the priority of a cell based on the satellite identification list.

Claims

1. A communication device (100) comprising: a transmitting unit (111) that transmits an attach request message to a core network device (300) that includes information indicating that it has the capability to support store-and-forward (S&F) mode; a receiving unit (112) that receives an attach approval message from the core network device (300) that includes a list including satellite identification information; and a control unit (120) that performs cell reselection based on the list.

2. The communication device according to claim 1, wherein the control unit performs reselection of the cell based on whether or not it is a cell corresponding to the satellite identification information included in the list.

3. The communication device according to claim 1 or 2, wherein the control unit performs reselection of the cell based on whether or not it is a store-and-forward (S&F) operating satellite cell.

4. The communication device according to claim 1 or 2, wherein the control unit performs a reselection of the satellite cell based on whether or not the cell is in a mode in which both a service link and a feeder link are available.

5. The communication device according to claim 1 or 2, wherein the receiving unit receives a system information message, and the system information message includes information indicating whether the satellite is in a mode in which both a service link and a feeder link are available.

6. The communication device according to claim 1 or 2, wherein the control unit, if it cannot find a satellite cell indicated by the satellite identification information included in the list, selects or determines a satellite cell not indicated in the list as the connection destination.

7. A core network device (300) comprising a control unit, the control unit performing the following processes: receiving an attach request message from a communication device (100) that includes information indicating that it has the capability to support store-and-forward (S&F) mode; and sending an attach approval message to the communication device that includes satellite identification information and includes a list used to perform cell reselection.

8. A communication method performed by a communication device, comprising the steps of: sending an attach request message to a core network device (300) that includes information indicating that it has the capability to support store-and-forward (S&F) mode; receiving an attach approval message from the core network device (300) that includes a list including satellite identification information; and performing cell reselection based on the list.

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