Terminal device, control method, and program for automatically configuring adjacent cell information in cellular communication system in which power saving control is implemented

Abstract

This terminal device: receives, from a connected first base station device, first configuration information relating to a Wake Up Signal (WUS) for causing a System Information Block Type 1 (SIB1) to be transmitted from a second cell that is different from a first cell provided by the first base station device and that is operating without the SIB1 being periodically transmitted; transmits the WUS to a second base station device that provides the second cell when a radio link failure is detected in the connection between the terminal device and the first base station device; acquires SIB1 information from the second base station device after the WUS has been transmitted; and executes reconnection to the second base station device.

Description

Terminal device, control method, and program for automatically configuring adjacent cell information in a cellular communication system with power-saving control implemented.

[0001] This invention relates to a technology for automatically configuring adjacent cell information in a cellular communication system with power-saving control implemented.

[0002] Cellular communication systems compliant with the cellular communication standards of the Third Generation Partnership Project (3GPP®) are widely deployed. In cellular communication systems, to enable smooth communication service even when terminal devices move, base station equipment provides terminal devices with adjacent cell information (called an adjacent cell list) about cells adjacent to the cell to which the terminal device is currently located or connected. Based on this adjacent cell information, the terminal device can switch the base station equipment it is connected to or located at as it moves by measuring the radio signals transmitted from the base station equipment of the surrounding cells. Such adjacent cell information is automatically created, for example, when the terminal device acquires the SIB1 transmitted by the surrounding base station equipment and reports it to the base station equipment. The terminal device acquires the cell identifier transmitted by the SIB1 (for example, NR-Cell Global Identifier in a fifth-generation (5G) network) and reports the acquired cell identifier to the serving base station equipment. This allows each base station device to recognize cells adjacent to the cell it provides, and if it receives an identifier for a cell that has not yet been identified as an adjacent cell, it updates the adjacent cell information to be provided to the terminal device. This automatic generation technology for adjacent cell information is called Automatic Neighbor Relations (ANR).

[0003] 3GPP contribution R2-2402859

[0004] In recent years, there has been a demand to reduce the power consumption on the network side in a cellular communication system. For this purpose, conventionally, a technology has been studied in which System Information Block Type 1 (SIB1), which has been regularly transmitted from a base station device, is transmitted in response to a request from a terminal device and is not transmitted regularly. This technology is called on-demand SIB1, and a cell in which power consumption is reduced by on-demand SIB1 is called a Network Energy Saving (NES) cell (see Non-Patent Document 1). A base station device that provides an NES cell transmits SIB1 when it receives a predetermined signal called a Wake Up Signal (WUS) from a terminal device. On the other hand, since the base station device stops transmitting SIB1 when it has not received the predetermined signal, it can suppress power consumption.

[0005] In an environment where such on-demand SIB1 is used, since SIB1 is not always transmitted periodically in an NES cell, a terminal device may not be able to obtain SIB1 for that NES cell, and there is a risk that ANR may not operate properly.

[0006] The present invention relates to a technique for automatically configuring adjacent cell information in a cellular communication system equipped with a power saving function.

[0007] A terminal device according to an aspect of the present invention includes: receiving means for receiving, from a first base station device with which the terminal device is connected, first setting information regarding a Wake Up Signal (WUS) for causing the first base station device to transmit System Information Block Type 1 (SIB1) in a second cell different from a first cell provided by the first base station device and in which SIB1 is not transmitted periodically; transmitting means for transmitting the WUS to a second base station device that provides the second cell when a radio link failure is detected in the connection with the first base station device; and reconnection processing means for obtaining the SIB1 information from the second base station device after transmitting the WUS and executing reconnection to the second base station device.

[0008] According to the present invention, in a cellular communication system with a power-saving function, it becomes possible to automatically configure adjacent cell information.

[0009] Other features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings. In the accompanying drawings, the same or similar components are given the same reference numeral.

[0010] The attached drawings are included in the specification and constitute a part thereof, illustrating embodiments of the present invention and are used to explain the principles of the present invention together with their description. Figure 1 is a diagram showing an example of a system configuration. Figure 2 is a diagram showing a first example of the processing flow executed in the system. Figure 3 is a diagram showing a variation of the first example of the processing flow executed in the system. Figure 4 is a diagram showing a variation of the first example of the processing flow executed in the system. Figure 5 is a diagram showing an example of the hardware configuration of each device according to this embodiment. Figure 6 is a diagram showing an example of the functional configuration of a terminal device. Figure 7 is a diagram showing an example of the functional configuration of a base station device for a non-NES cell. Figure 8 is a diagram showing an example of the functional configuration of a base station device for an NES cell. Figure 9 is a diagram showing a second example of the processing flow executed in the system. Figure 10 is a diagram showing an example of the functional configuration of a terminal device. Figure 11 is a diagram showing an example of the functional configuration of a base station device for a non-NES cell. Figure 12 is a diagram showing a third example of the processing flow executed in the system. Figure 13 is a diagram showing an example of the functional configuration of a terminal device.

[0011] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims, and not all combinations of features described in the embodiments are essential to the invention. Two or more of the features described in the embodiments may be combined in any way. Furthermore, identical or similar configurations will be given the same reference numeral, and redundant descriptions will be omitted.

[0012] (System Configuration) Figure 1 shows an example of the configuration of the wireless communication system of this embodiment. This wireless communication system is a cellular communication system compliant with a cellular communication standard compliant with the 4th generation (4G) or 5th generation (5G) or successor standards of the 3rd Generation Partnership Project (3GPP). The wireless communication system is composed of base station equipment 101, base station equipment 102, base station equipment 111, and terminal equipment 121. Note that Figure 1 is just an example, and of course, there may be more base station equipment and terminal equipment. Base station equipment 101, base station equipment 102, and base station equipment 111 are each associated with an Access and Mobility Management Function (AMF) and can be configured to communicate with Operation Administration and Maintenance (OAM) via the AMF, for example. Furthermore, base station devices 101, 102, and 111 may each be directly associated with an OAM without going through an AMF. While Figure 1 shows an example where base station devices 101, 102, and 111 are associated with a common AMF 131, at least some of these base station devices may be associated with different AMFs. Also, Figure 1 merely provides a simplified representation of the network functions relevant to this embodiment, and other network functions (and network nodes implementing those functions) may naturally exist. Additionally, AMFs and OAMs may be implemented as other functions with similar capabilities.

[0013] Here, the base station device 111 is configured not to periodically transmit System Information Block Type 1 (SIB1) for power saving control, but to transmit SIB1 only when it receives a request from the terminal device 121. Hereinafter, the cell provided by the base station device 111 will be referred to as a Network Energy Saving (NES) cell. In this embodiment, although SIB1 is not periodically transmitted in the NES cell, a synchronization signal (SS) is transmitted at a fixed interval (in one example, a longer interval than that of a normal cell may be set). The terminal device 121 can identify the physical cell identifier (PCI) of the NES cell based on the Primary SS (PSS) and Secondary SS (SSS) transmitted in the NES cell. The NES cell base station device 111 may be configured such that it cannot communicate with the terminal device 121 except when transmitting an SS. The NES cell base station device 111 terminates its power-saving operation when it receives a specific signal called a Wake Up Signal (WUS) from the terminal device 121, and operates to communicate with the terminal device 121, for example by transmitting an SIB1. When the SIB1 is transmitted, it may be broadcast, or it may be transmitted individually to the terminal device 121 that sent the WUS.

[0014] Base station devices 101 and 102 perform periodic transmission of SIB1 without power saving control. Hereinafter, the cell provided by base station device 101 will be referred to as cell A, and the cell provided by base station device 102 will be referred to as cell B. In this embodiment, cells that perform periodic transmission of SIB1 may be referred to as non-NES cells to distinguish them from NES cells. For cells A and B, terminal device 121 can identify not only PCI but also global cell identification information such as Cell Global Identifier (CGI) by decoding the periodic transmission of SIB1. In this embodiment, CGI is New Radio (NR)-CGI (NCGI) in 5G, and NCGI includes a network identifier (Public Land Mobile Network (PLMN) ID).

[0015] In this embodiment, the base station device 101 is configured to perform Automatic Neighbor Relations (ANR) functions. The base station device 101 can recognize, based on the measurement results of a radio signal transmitted by the terminal device 121 from a surrounding base station device, that the base station device that transmitted the radio signal forms an adjacent cell of cell A. The base station device 101 can then establish an Xn interface with the base station device providing that adjacent cell, enabling subsequent direct communication between the base station devices.

[0016] When the base station device 101 performs the ANR function, it needs to receive a report from the terminal device 121 containing information that identifies the global identifier of the cell. Therefore, for the ANR function by the base station device 101 to function effectively, it is important that the terminal device 121 can decode the SIB1 of surrounding cells. However, as mentioned above, NES cells do not periodically transmit SIB1, so the terminal device 121 cannot recognize and report the global identifier of the NES cell. In this embodiment, in view of these circumstances, a mechanism is provided to enable the ANR function to function appropriately in an environment where NES cells exist.

[0017] (Embodiment 1) Figure 2 shows a first example of the processing flow performed in the wireless communication system. Here, it is assumed that the terminal device 121 (User Equipment (UE)) has established a radio resource control (RRC) connection with the base station device 101 of cell A, and that the base station device 111 of the NES cell is not transmitting SIB1. Note that an Xn interface has not been established between the base station device 101 of cell A and the base station device 111 of the NES cell, and it is not possible to notify the terminal device 121 of the setting information to cause the NES cell to transmit SIB1. Furthermore, it is assumed that the OAM 132 manages whether each base station device is performing an SIB1 transmission stop operation (SIB1-less operation) (i.e., whether or not it is providing an NES cell).

[0018] The terminal device 121 transmits a Measurement Report (MR) to the base station device 101, relating the measurement result of the radio quality to the PCI of a cell provided by another base station device (e.g., base station device 111) different from the serving base station (base station device 101) (S201). The terminal device 121 may transmit the MR at a pre-set interval, for example, or in response to the measurement result meeting the conditions of a predetermined event. The PCI is identified by a combination of sequences used in the PSS and SSS. Therefore, the terminal device 121 can measure the radio quality based on the SS not only for non-NES cells but also for NES cells and notify the base station device 101 of the measurement result.

[0019] When the base station device 101 of a non-NES cell receives an MR, it determines whether or not it has obtained measurement results for PCI, which it does not recognize as an adjacent cell. If the base station device 101 receives a radio quality report from the terminal device 121 regarding PCI, which it does not recognize as an adjacent cell, it sends a message to the OAM 132 instructing it to stop the SIB1-less operation (S202). This message could be sent to the base station device of an NES cell, but since it is assumed that the base station device 101 does not hold any NES cell information other than PCI at this point, it sends the message to the OAM 132, which is capable of forwarding messages to that NES cell.

[0020] OAM 132 forwards the SIB1-less operation stop instruction message received from base station device 101 to base station device 111, which is currently performing the SIB1-less operation (S203). OAM 132 may, for example, forward the message to the base station devices of all NES cells under its management. This is just one example; if the received SIB1-less operation stop instruction message includes information about the PCI of an NES cell, OAM 132 may forward the message to the base station device of the NES cell using that PCI. In this case, OAM 132 manages the PCI of each NES cell, identifies the NES cell corresponding to the PCI included in the received message, forwards the message to the base station device of the identified NES cell, and operates in a manner that does not send the message to the base station devices of other NES cells. Alternatively, for example, OAM 132 may forward the message only to the base station devices of NES cells surrounding cell A. In this case, OAM 132 can manage the installation location of each base station device in order to identify the base station device of the NES cell located near each base station device. If a base station device whose location cannot be determined, such as a temporarily installed base station device, is providing an NES cell, the message may be forwarded to all base station devices whose location cannot be determined. Also, if the location of the base station device providing cell A cannot be determined, the message may be forwarded to all NES cells. In this case, the message may also be forwarded to the base station devices of NES cells surrounding a non-NES cell with which cell A has an established relationship with an adjacent cell. OAM 132 may forward the SIB1-less operation stop instruction message received from base station device 101 to the NES cell base station device 111 transparently without processing it, or it may process it by adding predetermined information before forwarding it to base station device 111. Furthermore, if the OAM132 includes PCI information in the stop instruction message for SIB1-less operation, and there is no NES cell corresponding to that PCI (i.e., the cell corresponding to that PCI is a non-NES cell), it may send a response message to the base station device 101 rejecting the stop instruction.In this case, the base station device 101 may either move the processing to S206 described later, or it may terminate the processing at this point.

[0021] When the NES cell base station device 111 receives a message instructing it to stop SIB1-less operation, it sends a response message to that message via the OAM 132 to the base station device 101 that sent the SIB1-less operation stop instruction message (S204). The SIB1-less operation stop instruction message may include location information of the base station device 101, and the NES cell base station device may accept the stop instruction and send an acknowledgment to the stop instruction message only if its own location is within a certain range from the base station device 101. This acknowledgment indicates that the SIB1-less operation in the NES cell will be stopped. On the other hand, if the NES cell base station device 111 is not within a certain range from the base station device 101, it may ignore the stop instruction and send a rejection response. In this case, the location information of the base station device 101 may be included in the SIB1-less operation stop instruction message by the base station device 101, or it may be included by the OAM 132. Also, the SIB1-less operation stop instruction message may include information on the geographical range set by the OAM 132, and the base station device of the NES cell may accept the stop instruction if its own location is within that geographical range, and reject (or ignore) the stop instruction if its own location is outside that geographical range. In this case, a negative response indicating rejection of the stop instruction may be sent back to the OAM 132. Furthermore, the base station device 111 of the NES cell may be configured to always comply with the SIB1-less operation stop instruction in an environment where SIB1 transmission is possible.

[0022] OAM 132 forwards the response message from the NES cell base station device 111 to the base station device 101 that sent the SIB1-less operation stop instruction message (S205). The SIB1-less operation stop instruction message may include the address information of the base station device 101 that sent the message, in which case the NES cell base station device 111 can send a response message specifying that address information. When OAM 132 receives the response message, it can forward the message according to that address information. Also, when OAM 132 receives the SIB1-less operation stop instruction message, it can add identification information to the message and forward it, and the NES cell base station device 111 can send a response message including that identification information to OAM 132. In this case, OAM132 may store the identification information in association with the base station device that sent the SIB1-less operation stop instruction message, and identify the base station device 101 to which the response message is forwarded based on the identification information contained in the response message.

[0023] The method for sending and receiving the stop instruction message and response message for SIB1-less operation via OAM is not limited to the method described above, and other methods may be used.

[0024] When the base station device 101 of cell A receives a response message indicating that it accepts the termination of SIB1-less operation, it sends an RRC reconfiguration message to the terminal device 121 that includes a reporting instruction for a globally identifiable identifier (e.g., CGI) for the NES cell (S206). The base station device 101 sends an RRC reconfiguration message to the terminal device 121 in which the reporttype in reportconfig, which is part of the Measurement configuration information, is set to reportCGI. This reporting instruction may include, for example, information specifying a PCI. That is, configuration information instructing the terminal device 121 to report a CGI for a specific PCI (e.g., the PCI reported in S201) may be notified to the terminal device 121 by the RRC reconfiguration message. Furthermore, when the NES cell base station device 111 receives a command to stop the SIB1-less operation, it stops that operation and performs SIB1 transmission (S207). Note that, for example, the base station device 111 may start broadcast transmission of SIB1 after a certain period of time has elapsed since sending a response message to the SIB1-less operation stop command message.

[0025] After receiving the RRC reconfiguration message, terminal device 121 decodes the SIB1 transmitted from the cell corresponding to the specified PCI according to the configuration information in the message and identifies the global identification information of that cell (e.g., PLMN ID, NCGI, etc.). Then, terminal device 121 notifies the serving base station (base station device 101) of the identified identification information (S208). Terminal device 121 sends an MR to base station device 101, for example, which includes information associating the PCI of the NES cell with the global identification information. Note that PLMN ID and NCGI are examples of information necessary for base station device 101 to process the relationship between the NES cell and neighboring cells (Neighbor Cell Relation (NCR)), and may be replaced with other information that enables the execution of that process. For example, instead of or in addition to PLMN ID or NCGI, E-UTRAN CGI (ECGI), Tracking Area Code (TAC), RAN-based Notification Area Code (RANAC), NR frequency, gNB ID Length, etc., may be used.

[0026] When base station device 101 receives an MR from terminal device 121, it sends an Uplink RAN ​​Configuration Transfer message to AMF 131 to request the NES cell's Transport Network Layer (TNL) address (S209). When AMF 131 receives this message, it sends a Downlink RAN ​​Configuration Transfer message containing the received information to base station device 111 of the NES cell (S210). Then, the NES cell base station device 111 includes the TNL address of the NES cell in an Uplink RAN ​​Configuration Transfer message and sends it to the AMF 131 (S211). The AMF 131 then sends this information to the base station device 101 using a Downlink RAN ​​Configuration Transfer message (S212). The base station device 101 uses the received information (the TNL address of the NES cell) to send an Xn SETUP REQUEST to the base station device 111 (S213). The base station device 111 then sends an Xn SETUP RESPONSE to the base station device 101 (S214). As a result, an Xn interface is established between base station device 101 and base station device 111, and the relationship between cell A and NES cell as adjacent cells is recognized.

[0027] In the example described above, the base station device 101 sends a message to the OAM 132 instructing it to stop SIB1-less operation when it receives an MR related to a PCI that it does not recognize as an adjacent cell, but it is not limited to this. For example, the base station device 101 may send the above message to the OAM 132 instructing it to stop SIB1 operation when the terminal device 121 does not recognize a cell from which it cannot receive SIB1 as an adjacent cell. For example, as shown in Figure 3, when the base station device 101 receives an MR related to a PCI that it does not recognize as an adjacent cell from the terminal device 121, it sends an RRC reconfiguration message to the terminal device 121 (S301) to have the terminal device 121 report the information necessary for processing to build an NCR such as a CGI for the cell corresponding to that PCI. When the terminal device 121 receives this message, it attempts to obtain an SIB1 for the NES cell, but at this point, no SIB1 has been transmitted for the NES cell. Therefore, the terminal device 121 transmits an MR to the base station device 101 that includes information indicating that SIB1 was not received (for example, "noSIB1" which can be set in the CGI-InfoNR field as defined in the 3GPP standard) (S302). When the base station device 101 receives this MR that includes information indicating that SIB1 was not received, it executes the processing from S202 onwards in Figure 2.

[0028] Furthermore, as shown in Figure 4, the terminal device 121 may also transmit to the base station device 101 an MR in S401 that is transmitted in place of the MR in S201, which includes information indicating that SIB1 was not received. The terminal device 121 searches for an SS / Physical Broadcast Channel (PBCH) block (SSB) in order to transmit an MR. A Master Information Block (MIB) is transmitted in the PBCH of the SSB. The MIB contains information indicating whether or not SIB1 is broadcast transmitted. When an SSB is transmitted in an NES cell (not only the SS but also the PBCH is transmitted), the terminal device 121 can obtain information indicating whether or not SIB1 is broadcast transmitted in the NES cell. As a result, if SIB1 is not broadcast in the NES cell, the terminal device 121 can include the above-mentioned noSIB1 and other information in the MR and transmit it as shown in S401. When the base station device 101 receives an MR containing information indicating that SIB1 was not received, it executes the processing from S202 onwards in Figure 2.

[0029] Furthermore, after the Xn interface is established between base station device 101 and base station device 111 and it is recognized that cell A and the NES cell are adjacent cells (for example, when base station device 101 begins to manage the NES cell provided by base station device 111 as an adjacent cell), base station device 111 may stop transmitting SIB1 again. For example, base station device 101 may send a message to base station device 111, either directly or via OAM 132, instructing base station device 111 to resume SIB1-less operation. Upon receiving this message, OAM 132 may send a message to the base station device of the NES cell from which the instruction to stop SIB1-less operation was sent, instructing it to resume SIB1-less operation. Upon receiving this message, the base station device of the NES cell resumes SIB1-less operation and stops transmitting SIB1. Furthermore, the base station equipment of the NES cell may transmit SIB1 only for a predetermined period or a predetermined number of times, and then resume SIB1-less operation. The base station equipment 111 may then send a message to the base station equipment 101 or OAM 132 declaring the cessation of SIB1-less operation. The predetermined period or predetermined number of times may be instructed by the base station equipment 101 or OAM 132.

[0030] Figure 5 shows an example of the hardware configuration of a base station device (base station device 101, base station device 111) and a terminal device 121 according to this embodiment. In one example, the base station device and terminal device are configured to include a processor 501, ROM 502, RAM 503, storage device 504, and communication circuit 505. The processor 501 is a computer configured to include one or more processing circuits, such as a general-purpose CPU (central processing unit) or ASIC (application-specific integrated circuit), and executes the overall processing of the device and the above-mentioned processing by reading and executing programs stored in the ROM 502 and storage device 504. The ROM 502 is a read-only memory that stores information such as programs and various parameters related to the processing executed by the base station device and terminal device. The RAM 503 functions as a workspace when the processor 501 executes programs and is a random access memory that stores temporary information. The storage device 504 is configured to include, for example, a removable external storage device. The communication circuit 505 is configured to include, for example, a circuit for wireless communication of 5G or its successor standards. Although Figure 5 shows one communication circuit 505, the base station equipment and terminal equipment may have multiple communication circuits. For example, the base station equipment and terminal equipment may have wireless communication circuits for 5G and its successor standards, respectively, and an antenna common to those circuits. The base station equipment and terminal equipment may also have separate antennas suitable for each standard. Furthermore, the base station equipment may also have a wired communication circuit used when communicating with other base station equipment or nodes in the core network. Furthermore, the terminal equipment may also have communication circuits compliant with wireless communication standards other than cellular communication standards, such as wireless local area networks (LANs) and Bluetooth®. The base station equipment and terminal equipment may have separate communication circuits 505 for each of the multiple usable frequency bands, or they may have a common communication circuit 505 for at least a portion of those frequency bands.

[0031] Figure 6 shows an example of the functional configuration of the terminal device 121 according to this embodiment. The terminal device 121 has a measurement unit 601 and a reporting unit 602 as its functions. These functions may be implemented, for example, by the processor 501 executing a program stored in the ROM 502 or storage device 504, or they may be implemented as functions of the communication circuit 505. The terminal device 121 also naturally has other functions that a normal terminal device (UE) in a cellular communication system has.

[0032] The measurement unit 601 measures the radio quality based on signals such as SSB transmitted in surrounding cells. The reporting unit 602 reports the radio quality measurement results obtained by the measurement unit 601 to the serving base station. For example, if the measurement unit 601 receives an RRC reconfiguration message containing reportCGI, it observes the SIB1 corresponding to the specified PCI, and the reporting unit 602 reports the results of that observation (such as PLMN ID and NCGI) to the serving base station.

[0033] Figure 7 shows an example of the functional configuration of the base station device 101 according to this embodiment. The base station device 101 has the functions of a report receiving unit 701, an instruction transmission unit 702, and an ANR processing unit 703. These functions may be implemented, for example, by a processor 501 executing a program stored in ROM 502 or a storage device 504, or they may be implemented as functions of a communication circuit 505. The base station device 101 also naturally has other functions that a normal base station device (such as a gNB) in a cellular communication system has. The base station device 102 may also have similar functions.

[0034] The report receiving unit 701 receives a report from the terminal device 121 that associates the PCI and radio quality of surrounding cells. The instruction transmitting unit 702, for example, based on the fact that the PCI in the report received by the report receiving unit 701 does not match any of the PCIs of cells recognized as adjacent cells, transmits a stop instruction to the OAM 132 to stop the SIB1-less operation of the base station equipment of the NES cell in which the base station equipment 101 has not constructed an NCR. This stop instruction is then forwarded to the base station equipment 111 via the OAM 132. The instruction transmitting unit 702 may also transmit a stop instruction in response to receiving information from the terminal device 121 indicating that SIB1 is not being received. Based on the fact that the instruction transmission unit 702 has transmitted an instruction (or has received a response to that instruction), the report receiving unit 701 sends an RRC reconfiguration message to the terminal device 121 instructing it to report identification information (such as PLMN ID and NCGI) required to construct an NCR for cells that are not recognized as adjacent cells, and receives the report. Based on the received report, the ANR processing unit 703 constructs an NCR with the NES cell. The ANR processing unit 703 then manages information about adjacent cells of the cell provided by the base station device 101 and can provide the terminal device with a list of those adjacent cells.

[0035] Figure 8 shows an example of the functional configuration of the base station device 111 according to this embodiment. The base station device 111 has an SIB1-less processing unit 801 and an instruction receiving unit 802 as its functions. These functions may be implemented, for example, by the processor 501 executing a program stored in the ROM 502 or storage device 504, or they may be implemented as functions of the communication circuit 505. The base station device 111 also naturally has other functions that a normal base station device (such as a gNB) in a cellular communication system has.

[0036] The SIB1-less processing unit 801 performs processes such as executing and stopping the SIB1-less operation. The instruction receiving unit 802 receives an instruction to stop the SIB1-less operation from the base station device 101, for example, via the OAM 132. The SIB1-less processing unit 801 transmits SIB1 according to the instruction, and may restart the SIB1-less operation and stop transmitting SIB1, for example, in response to the establishment of an NCR with the base station device 101. The SIB1-less processing unit 801 also controls the system to transmit at least SS (or SSB) even while the SIB1-less operation is in progress.

[0037] By using the above configuration, the base station device 101 can properly perform the ANR function in an environment where an NES cell exists, as shown in Figures 2 to 4 above.

[0038] (Embodiment 2) Figure 9 shows a second example of the processing flow executed in the wireless communication system. Here again, it is assumed that the base station device 101 of cell A has not established an Xn interface with base station device 111 and does not recognize the NES cell provided by base station device 111 as an adjacent cell. Also, it is assumed that the base station device 111 of the NES cell is not transmitting SIB1. Furthermore, it is assumed that base station device 102 has established an Xn interface with base station device 111 and recognizes that the NES cell provided by base station device 111 and cell B are adjacent cells. In this case, base station device 102 can obtain Wake Up Signal (WUS) configuration information (WUS configuration) transmitted by terminal device 121 to cause base station device 111 to transmit the SIB1 of the NES cell from base station device 111 via the Xn interface. The base station device 102 can then provide its WUS configuration to the terminal device 121. The WUS configuration here may include information indicating that the terminal device 121 should retain (not delete) its configuration information even after disconnecting from the base station device 102. The WUS configuration may separately include information indicating whether or not to retain the configuration during a handover and information indicating whether or not to retain the configuration during cell re-selection, or it may include a single piece of information indicating whether or not to retain the configuration information when either a handover or cell re-selection is performed. The terminal device 121 may delete the WUS configuration at a corresponding timing (at least one of the following: disconnection from the base station device 102, cell re-selection, or handover) if the information indicates that the configuration information should be deleted or if the information is not included in the WUS configuration.

[0039] If terminal device 121 is connected to base station device 102 of cell B (S901), it receives a WUS configuration for the NES cell provided by base station device 111 from base station device 102 (S902). Terminal device 121 then retains the received WUS configuration. Subsequently, in response to receiving an RRC connection release message from base station device 102, terminal device 121 disconnects from base station device 102, and assumes, for example, enters an RRC idle state (S903). At this time, terminal device 121 retains the WUS configuration received in S902 even after the connection with base station device 102 is disconnected (after receiving the RRC release message) (S904). In one example, the base station device 102 may transmit the WUS configuration in the system information (SIB). However, it is not limited to this, and the base station device 102 may, for example, include the WUS configuration in the RRC connection release and transmit it. Also, the base station device 102 may, for example, provide the terminal device 121 with the WUS configuration for the NES cell when it receives an MR with PCI for the NES cell from the terminal device 121. Furthermore, when idle reselection occurs between a cell provided by the device or another base station device (for example, base station device 101), if the terminal device 121 is holding a WUS configuration, the device may notify the terminal device 121 (for example, via SIB) of information indicating whether or not to maintain that WUS configuration.

[0040] Subsequently, the terminal device 121 selects cell A provided by the base station device 101 as the cell to connect to through cell reselection processing due to movement (S905), and establishes a connection with the base station device 101 (S906). Then, the terminal device 121 moves further to a position where, for example, a handover to an NES cell can be performed. Note that this is just an example, and the terminal device 121 may switch its current cell from cell B provided by the base station device 102 to cell A provided by the base station device 101 by handover instead of cell reselection. In this case, the terminal device 121 may maintain the WUS configuration without deleting it during the handover. For example, if the terminal device 121 determines that the radio quality of the NES cell is higher by a predetermined level than the radio quality of cell A, it transmits an MR to the base station device 101 that reports the relationship between the PCI and radio quality of the NES cell (S907). When base station device 101 receives this MR, it identifies that the cell corresponding to that PCI is not recognized as an adjacent cell. Then, base station device 101 sends an RRC reconfiguration message to terminal device 121, which contains a reportCGI to cause terminal device 121 to report the information necessary to establish an NCR with the base station device providing that cell (S908).

[0041] The terminal device 121, in accordance with the message, checks, for example, the MIB of the NES cell to determine whether or not SIB1 is being transmitted. Here, it is assumed that the terminal device 121 has determined that SIB1 is not being transmitted in the NES cell. Then, the terminal device 121 transmits a WUS (S909) to cause the NES cell to transmit SIB1. The WUS can be, for example, a Random Access Preamble (RAP). That is, the terminal device 121 transmits a RAP in the frequency and time resources in the NES cell where transmission of a RAP is permitted. Note that other signals may be used as the WUS. When the base station device 111 of the NES cell receives the WUS, it transmits a Random Access Response (RAR) accordingly. Here, since RAR is transmitted on a physical downlink shared channel (PDSCH), the base station device 111 transmits a physical downlink control channel (PDCCH) that includes downlink control information (DCI) indicating the schedule information of this PDSCH (frequency and time resources on which the PDSCH is transmitted) (S910). For example, the base station device 111 transmits the PDCCH (DCI) to the terminal device 121 in CORESET0 (Type0 PDCCH Common Search Space). CORESET0 (frequency and time resources) can be specified in the MIB. That is, the terminal device 121 can check in the MIB whether SIB1 is being broadcast and check the frequency and time resources corresponding to CORESET0.

[0042] The base station device 111 transmits the RAR according to the schedule specified in the PDCCH (DCI) (S911). After transmitting the RAR, the base station device 111 transmits a PDCCH (DCI) that specifies the schedule of SIB1 transmitted on the PDSCH (the frequency and time resources at which SIB1 is transmitted) (S912), and transmits SIB1 according to that schedule (S207). The SIB1 transmitted here is the same as that described in relation to S207 in FIG. 2. After transmitting the RAP, the terminal device 121 provides a RAR window for receiving the RAR based on the PDCCH (DCI), and waits for the reception of the RAR within that window. When the terminal device 121 can receive the RAR, it receives CORESET0, and receives SIB1 according to the schedule specified in that CORESET0. Since the processing after S207 is the same as that described in FIG. 2, the description thereof is omitted.

[0043] Note that before transmitting the WUS in S909, the terminal device 121 can check the MIB of the NES cell and check the cell Barred information indicating access restriction (restriction of connection of the terminal device to that cell) in that cell. Then, the terminal device 121 can determine whether to transmit the WUS based on the cell Barred information. That is, when access to the NES cell is restricted, the terminal device 121 can determine whether transmission of the WUS is permitted according to the content of the restriction. The terminal device 121 can transmit the WUS only when it determines that transmission of the WUS is permitted. Thereby, when there is a NES cell under access restriction, it is possible to prevent the WUS from being transmitted to that NES cell.

[0044] Also, in the above example, an example was shown in which the terminal device 121 transmits an MR including the PCI of a cell not managed as an adjacent cell in the base station device 101 in S907, but it is not limited to this. For example, the terminal device 121 may transmit information (such as noSIB1) indicating that SIB1 has not been transmitted to the base station device 101 in S907.

[0045] Furthermore, the above example described a case where the base station device 101 cannot provide the WUS configuration to the terminal device 121 because it has not established an Xn interface with the base station device 111 of the NES cell. However, this is just one example, and if the base station device 101 cannot obtain the WUS configuration from the NES cell, it may provide the terminal device 121 with a WUS configuration set with default parameter values ​​(NES cell common parameters). This allows the base station device 101 to provide the terminal device 121 with at least the minimum WUS configuration information when it is necessary to have the terminal device 121, which does not have the WUS configuration, perform a handover to the NES cell, etc. The terminal device 121 does not have parameters specific to the NES cell, but by using default parameter values, it becomes possible to transmit WUS to that NES cell, even if it means tolerating a certain decrease in efficiency.

[0046] Furthermore, after receiving a WUS configuration specific to the NES cell in cell B, terminal device 121 may move to cell A by cell reselection and receive a WUS configuration with default values. In this case, terminal device 121 may, for example, overwrite the NES cell-specific WUS configuration with the WUS configuration with default values ​​that it receives later. In contrast, terminal device 121 may, for example, store the WUS configuration it holds internally in association with identification information that uniquely identifies settings such as PCI, and if it subsequently receives a WUS configuration with the same identification information, it may prevent the later-received WUS configuration from being overwritten. According to this, the terminal device 121 can maintain the WUS configuration specific to the NES cell that was first received. The WUS configuration may also include information indicating whether it is configuration information specific to a particular NES cell or configuration information for a default value. For example, a default value may be assigned WUS configuration id = 0, and if it is NES cell specific, WUS configuration id = 1 (or a non-zero integer) may be assigned. Furthermore, if the terminal device 121 receives a WUS configuration with a default value (WUS configuration id = 0) while it is holding a WUS configuration specific to the NES cell (assigned WUS configuration id = 1 (or a non-zero integer)), it may discard the received WUS configuration with a default value without updating the configuration information. Furthermore, when the terminal device 121 receives a WUS configuration specific to an NES cell (where WUS configuration id = 1 (or a non-zero integer)) while it is holding a default WUS configuration (where WUS configuration id = 0), it overwrites the held configuration information with the setting value of the received NES cell-specific WUS configuration.As a result, the terminal device 121 can retain information when it receives a WUS configuration specific to the NES cell.

[0047] Furthermore, the base station device 101 can acquire information about the NES cell and establish an Xn interface with the base station device 111 by having the terminal device 121 use the default WUS configuration. After establishing the Xn interface, the base station device 101 can acquire the NES cell-specific WUS configuration. Then, by providing the terminal device 121 with the NES cell-specific WUS configuration, the base station device 101 can enable the terminal device 121 to retain the WUS configuration specific to that NES cell.

[0048] Further, when the terminal device 121 conventionally received an RRC reconfiguration including a report CGI, it started a timer called T321 and attempted to receive SIB1 until the timer expired. On the other hand, when on-demand SIB1 (SIB1 based on WUS) is used, after receiving an RRC reconfiguration including a report CGI, it may take a longer time for the transmission of WUS, the reception of RAR, the reception of SIB1, compared to the reception of conventional SIB1. Therefore, a new timer (for example, T321-A) for on-demand SIB1 may be set. Generally, a longer value than T321 is set for T321-A. After receiving an RRC reconfiguration including a report CGI, the terminal device 121 starts T321 and T321-A, checks the MIB of the cell corresponding to the PCI to be reported, stops and resets T321 if SIB1 is not broadcast transmitted, and may stop and reset T321-A if SIB1 is broadcast transmitted. Then, the terminal device 121 can attempt to receive SIB1 until the timer that has not been stopped and reset expires. Thereby, while the terminal device 121 can improve the probability of receiving SIB1 from the base station device 111 that is executing SIB1-less operation, it can prevent the reception operation of SIB1 from being unnecessarily continued for a long time when receiving SIB1 from a base station device that is not executing SIB1-less operation.

[0049] Next, the configurations of the terminal device 121 and the base station device 101 will be described. Note that the hardware configuration examples of these devices are as described above with reference to FIG. 5, and the description will not be repeated here. Also, since the hardware configuration and functional configuration of the base station device 111 are the same as those in the first embodiment, the description will not be repeated.

[0050] Figure 10 shows an example of the functional configuration of the terminal device 121 according to this embodiment. In addition to the measurement unit 601 and the reporting unit 602, the terminal device 121 has a setting retention unit 1001 as its functions. These functions may be implemented, for example, by the processor 501 executing a program stored in the ROM 502 or the storage device 504, or they may be implemented as functions of the communication circuit 505. The terminal device 121 also naturally has other functions that a normal terminal device (UE) in a cellular communication system has.

[0051] The configuration holding unit 1001 holds the WUS configuration. The configuration holding unit 1001 is configured to continue holding the WUS configuration received from the base station device 102 not only while connected to the base station device 102, but also after the connection to the base station device 102 is disconnected. For NES cells where SIB1 has not been transmitted, the measurement unit 601 can receive SIB1 by transmitting a WUS based on the WUS configuration held in the configuration holding unit 1001. The measurement unit 601 may, for example, transmit a WUS when it receives instructions from the serving base station (base station device 101) (an RRC reconfiguration message including reportCGI), or it may transmit a WUS (regardless of instructions from the serving base station) when it confirms that SIB1 has not been transmitted (for example, noSIB is indicated in the MIB). The reporting unit 602 is the same as in Embodiment 1.

[0052] Figure 11 shows an example of the functional configuration of base station devices 101 and 102 according to this embodiment. In addition to a report receiving unit 701 and an ANR processing unit 703, base station devices 101 and 102 have a setting notification unit 1101 as their functions. These functions may be implemented, for example, by a processor 501 executing a program stored in ROM 502 or storage device 504, or they may be implemented as functions of a communication circuit 505. Of course, base station device 101 also has other functions that a normal base station device (such as a gNB) in a cellular communication system has. The report receiving unit 701 and the ANR processing unit 703 are the same as in Embodiment 1.

[0053] The configuration notification unit 1101, when an NES cell and NCR are established, obtains WUS configuration information from the base station equipment of the NES cell and notifies the connected terminal device or a terminal device located in a cell provided by its own device of the WUS configuration. In the example in Figure 9, the configuration notification unit 1101 of the base station equipment 102 transmits the WUS configuration to the terminal device 121, and the configuration notification unit 1101 of the base station equipment 101 does not notify such information. The terminal device 121 maintains the WUS configuration even after disconnecting from the base station equipment 102, and when it connects to the base station equipment 101, it uses the WUS configuration to collect information about the NES cell and notifies the base station equipment 101 of the collected information. The report receiving unit 701 of the base station device 101 receives the information, and the ANR processing unit 703 uses the information to perform ANR processing and establish an NCR with the NES cell provided by the base station device 111.

[0054] By using the above configuration, the base station device 101 can properly perform the ANR function in an environment where an NES cell exists, as shown in Figure 9 above.

[0055] (Embodiment 3) Figure 12 shows a third example of the processing flow performed in the wireless communication system. This example has the same assumptions as the second example. That is, the base station device 101 of cell A has not established an Xn interface with base station device 111 and does not recognize the NES cell provided by base station device 111 as an adjacent cell. Also, it is assumed that the base station device 111 of the NES cell is not transmitting SIB1. Furthermore, base station device 102 has established an Xn interface with base station device 111, recognizes that the NES cell provided by base station device 111 and cell B are adjacent cells, and can obtain the WUS configuration for the NES cell provided by base station device 111 and provide that WUS configuration to terminal device 121. Note that the WUS configuration here may include information indicating that the terminal device 121 should retain its configuration information (not delete it) even after disconnecting from the base station device 102. In Figure 12, the same reference numbers are used for processes similar to those in Figures 2 and 9.

[0056] In this process, as in Figure 9, the terminal device 121 is connected to the base station device 102 of cell B (S901), and it is assumed that the terminal device 121 has received the WUS configuration for the NES cell provided by the base station device 111 from the base station device 102 (S902). The terminal device 121 holds the received WUS configuration. Subsequently, in response to receiving an RRC connection release message from the base station device 102, the terminal device 121 disconnects from the base station device 102 and enters, for example, an RRC idle state (S903). At this time, even after the connection with the base station device 102 is disconnected (after receiving the RRC release message), the terminal device 121 maintains the WUS configuration received in S902 (S904). As in the second example, the transmission of the WUS configuration from the base station device 102 may be performed by SIB in cell B or by an RRC connection release message. The base station device 102 may also notify the terminal device 121 of the WUS configuration by SIB or an RRC connection release message.

[0057] After transitioning to the RRC idle state, terminal device 121 checks the MIB of the NES cell to determine whether or not SIB1 has been transmitted. Here, it is assumed that terminal device 121 has determined that SIB1 has not been transmitted in the NES cell. Then, terminal device 121 sends a WUS (S1201) to cause the NES cell to transmit SIB1, receives a PDCCH (DCI) containing information for receiving RAR (S1202), and receives RAR based on that information (S1203). Subsequently, terminal device 121 receives a PDCCH (DCI) containing information for receiving SIB1 (S1204), and receives SIB1 based on that information (S1205). The details of the processes from S1201 to S1205 are as described above with respect to the processes from S909 to S912 and S207 in Figure 9, so the explanation will not be repeated here. The terminal device 121 retains the information of the NES cell's SIB1 received in S1205 (S1206). The terminal device 121 may obtain information from the SIB1 that the base station device needs to establish an NCR with the NES cell's base station device 111, such as the PLMN ID and NCGI, and retain that information.

[0058] Furthermore, the terminal device 121 may transmit a WUS if, for example, it satisfies the conditions related to the measurement results of wireless quality for cell reselection from cell B to cell A, or if it periodically measures the electric field conditions while cell B is in the area and the measurement results satisfy predetermined conditions.

[0059] For example, when terminal device 121 transitions to the RRC idle state while located in cell B, it executes the Cell selection evaluation process specified in the 3GPP standard. First, terminal device 121 receives an SIB or RRC release message and obtains priority information used for measurement conditions to perform measurement of the electric field conditions at each frequency and for conditional expressions to perform cell reselection. Next, terminal device 121 determines whether the conditions for measurement are met, for example, by comparing the frequency priority of cell B with the frequency priority of the adjacent cell (cell A), and by using the parameters included in the SIB1 received from cell B (e.g., SnonIntraSearchP) and the measured electric field information. If terminal device 121 determines that the conditions for measurement are met, it starts searching for adjacent cells. Subsequently, if the electric field threshold has been notified in advance in the WUS configuration, the terminal device 121 transmits a WUS to the NES cell in accordance with the conditions based on that electric field threshold being met. Alternatively, the conditions under which measurements should be performed may be used as the conditions for transmitting a WUS to the NES cell, without setting a new electric field threshold. Furthermore, the terminal device 121 may periodically measure the electric field of adjacent cells, for example, every 20 milliseconds, during RRC idle transitions, and transmit a WUS to the NES cell according to the electric field conditions. In other words, the terminal device 121 may periodically perform measurements on adjacent cells not only when the above-mentioned conditions for measurement are met, but also regardless of the conditions. The base station device 102 of cell B may transmit periodic information and parameter information for transmitting a WUS according to the electric field conditions to the terminal device 121 in the WUS configuration. The electric field conditions may include, for example, a condition where the offset between the electric field of the own cell (RSRP) and the electric field of the adjacent cell (RSRP) is at or above a predetermined level (e.g., 5 dB). The terminal device 121 periodically measures the electric field of the adjacent cell according to the periodic information and may transmit a WUS to the NES cell if the electric field conditions are met.

[0060] Subsequently, the terminal device 121 selects cell A provided by the base station device 101 as the cell to connect to through a cell reselection process accompanying movement (S905), and establishes a connection with the base station device 101 (S906). Then, the terminal device 121 moves further to a position where, for example, a handover to an NES cell can be performed. Note that this is just an example, and the terminal device 121 may switch the cell it is located in from cell B provided by the base station device 102 to cell A provided by the base station device 101 by a handover instead of cell reselection. For example, if the terminal device 121 determines that the radio quality of the NES cell is higher by a predetermined level than the radio quality of cell A, it transmits an MR to the base station device 101 that reports the relationship between the PCI and radio quality of that NES cell (S907). When the base station device 101 receives this MR, it identifies that the cell corresponding to that PCI is not recognized as an adjacent cell. Then, the base station device 101 sends an RRC reconfiguration message to the terminal device 121, which includes a reportCGI script to cause the terminal device 121 to report the information necessary to establish an NCR with the base station device providing the cell (S908). Upon receiving this message, the terminal device 121 reports to the base station device 101 the information obtained by the SIB1 of the NES cell that it held in S1206 (S208).

[0061] Furthermore, after receiving the WUS configuration, terminal device 121 may transmit a WUS at any time (for example, even while connected to base station device 102) to hold the SIB1 information in advance, and then, after establishing a connection with base station device 101 through handover or cell reselection and connection processing after disconnection, provide the SIB1 information to base station device 101. Alternatively, base station device 102 may notify terminal device 121, via an RRC connection release message or the like, that it should transmit a WUS to obtain the SIB1 information in response to the disconnection of the connection with base station device 102. In this case, terminal device 121 can transmit a WUS after the disconnection of the connection with base station device 102 to obtain the SIB1 information of the NES cell and obtain predetermined information necessary for other base station devices (for example, base station device 101) to construct an NCR with that NES cell. Furthermore, the terminal device 121 can maintain its predetermined information even when moving beyond cell B provided by the base station device 102.

[0062] Furthermore, the above example described an example where the terminal device 121 is located in a non-NES cell, but it is not limited to this. For example, the terminal device 121 may receive SIB1 while located in an NES cell and retain the information of that SIB1. In this case, the terminal device 121 may receive the SIB1 of the NES cell by transmitting a WUS based on configuration information notified by, for example, the base station equipment of another cell that has already established an NCR with that NES cell, while located in the NES cell. The terminal device 121 may then continue to retain the information of that SIB1 when it moves from that NES cell to another cell. The terminal device 121 then moves to another cell that has not established an NCR with that NES cell (for example, cell A), and when it is instructed by, for example, the base station equipment of that cell to report the information of SIB1, it may notify the base station equipment of the SIB1 it has stored. Furthermore, if the SIB1 contains information indicating that the information of the SIB1 should be retained, the terminal device 121 may continue to retain the information of the SIB1 even after the cell has moved. Even if the SIB1 does not contain information indicating that the information of the SIB1 should be retained, the terminal device 121 may continue to maintain the information of the SIB1 until a predetermined period of time has elapsed or until the number of cell transitions (cell re-selection or handover) reaches a predetermined number.

[0063] Next, the configuration of the terminal device 121 will be described. Note that the hardware configuration example of the terminal device 121 is as described above with reference to Figure 5, and will not be repeated here. Furthermore, the hardware and functional configurations of the base station device 101 and base station device 111 are the same as in Embodiment 2, and will not be repeated here.

[0064] Figure 13 shows an example of the functional configuration of the terminal device 121 according to this embodiment. In addition to the measurement unit 601 and the reporting unit 602, the terminal device 121 has an SIB1 acquisition and holding unit 1301 as its functions. These functions may be implemented, for example, by the processor 501 executing a program stored in the ROM 502 or the storage device 504, or they may be implemented as functions of the communication circuit 505. The terminal device 121 also naturally has other functions that a normal terminal device (UE) in a cellular communication system has.

[0065] The SIB1 acquisition and storage unit 1301 receives the WUS configuration from the base station device 102 and uses the WUS configuration to acquire and store the SIB1 of the NES cell. The SIB1 acquisition and storage unit 1301 then stores the information of the acquired SIB1 (information contained in the SIB1 that is necessary for constructing the NCR). The reporting unit 602 reports the information of the stored SIB1, for example, after establishing a connection with the base station device 101.

[0066] By performing the processing shown in Figure 12 using the above configuration, the base station device 101 can properly operate the ANR function in an environment where NES cells exist.

[0067] (Modification) The terminal device 121 may delete the SIB1 information and WUS configuration in response to a move to the connected cell (handover or cell reselection). For example, if the WUS configuration is managed in predetermined area units, such as an area common to TACs, the terminal device 121 may continue to retain the WUS configuration and SIB1 information without discarding it when moving within that area. On the other hand, if the terminal device 121 moves beyond that area, it may discard (delete) the WUS configuration and SIB1 information. Information indicating the area in which the WUS configuration should continue to be retained may be included in the WUS configuration, or it may be notified to the terminal device 121 together with the WUS configuration. Furthermore, the terminal device 121 may decide whether to retain or delete the WUS configuration and SIB1 information based on the timer, the number of cell re-selections, the value of valuetag, etc. Also, in order to simplify the implementation of the base station device, the WUS configuration may be managed on a cell-by-cell basis, and the SIB1 information and WUS configuration may be deleted when a cell re-selection occurs.

[0068] For example, when the base station device 102 notifies WUS Configuration information, it may transmit a first timer value indicating the retention period of the WUS Configuration and a second timer value indicating the retention period of SIB1. Alternatively, instead of timer values, time information specifying the timing of the retention period's expiration may be transmitted. When timers are used, the terminal device 121 starts the timers using the respective timer values ​​notified when acquiring the WUS Configuration, deletes the retained WUS Configuration when the first timer expires, and deletes the retained SIB1 information when the second timer expires. Note that the above example shows a distinction between the first and second timer values, but this is not limited to this example. In other words, when the base station device 102 notifies the WUS Configuration information, it may also transmit one piece of information (e.g., a timer value) indicating the retention period for the WUS Configuration and SIB1 information. For example, the terminal device starts a timer using the timer value notified when acquiring the WUS Configuration, and deletes both the retained WUS Configuration and SIB1 when the timer expires. If the terminal device 121 deletes the WUS Configuration due to the timer's expiration, it may reacquire the WUS Configuration if necessary. Furthermore, the terminal device 121 may continue to retain the retained WUS Configuration and SIB1 information even if it performs cell reselection or handover to another cell, as long as it is after the timer has started but before it has expired.

[0069] Furthermore, the base station device 102 may notify the terminal device 121 of the number of cell re-selection or handovers in the WUS configuration. The terminal device 121 may retain the WUS configuration and SIB1 information until the threshold for the number of cell re-selection or handovers is exceeded, and delete that information when the threshold is exceeded. Separate values ​​may be provided for the WUS configuration and SIB1 information as the threshold for the number of cell re-selection or handovers, or the same value may be used. Also, after the terminal device 121 has transitioned from the cell that received the WUS configuration or SIB1 information to another cell by cell re-selection or handover, it may unconditionally delete at least one of the WUS configuration and SIB1 information received before the transition. Furthermore, after a handover, the terminal device 121 may delete at least one of the WUS configuration and SIB1 information in response to receiving a deletion instruction from the connected base station device.

[0070] Furthermore, the terminal device 121 can use the Value Tag included in the WUS configuration to determine whether the setting value is the same as the previous setting value when the WUS configuration is received multiple times. For example, if the terminal device 121 receives a WUS configuration (config id = 0x01, value tag = 0x01) and then receives another WUS configuration (config id = 0x01, value tag = 0x01), it can determine that the setting value of the WUS configuration is the same and that there is no need to update the WUS configuration it holds. On the other hand, if terminal device 121 receives WUS configuration (config id = 0x01, value tag = 0x01) and then receives WUS configuration (config id = 0x01, value tag = 0x02), it determines that the setting value of WUS configuration has been updated and updates the setting value in the WUS configuration it holds to the setting value indicated by value tag = 0x02. In this case, terminal device 121 may also start the expiration timer for WUS configuration triggered by the update of the setting value of the WUS configuration it holds. The above-mentioned config id (WUS configuration id) may be a value that at least distinguishes whether the WUS configuration is configuration information specific to the NES cell or a default value. For example, when two non-NES cell base station devices separately transmit a WUS configuration for one NES cell, these WUS configuration ids may match. The two non-NES cell base station devices may each set different value tags in the WUS configuration. In this case, the terminal device 121 will retain the WUS configuration that was received later by updating the WUS configuration.

[0071] On the other hand, the 3GPP standard does not specify a value tag for SIB1. In contrast, in this embodiment, with the introduction of on-demand SIB1, an SIB1 with a newly defined value tag can be transmitted from the NES cell. This allows the terminal device 121 to determine, based on its value tag, whether the information of the SIB1 it holds and the information of the SIB1 transmitted in the NES cell are the same. If the value tag of the SIB1 it holds and the value tag of the SIB1 it receives match, the terminal device 121 can determine that it is not necessary to transmit the WUS and receive the SIB1. In one example, the value tag of SIB1 may be included in the MIB. For example, terminal device 121 receives an SIB1 in a cell and stores the SIB1's information along with its value tag. Then, after leaving that cell or moving to another cell, terminal device 121 returns to the cell from which the SIB1 was acquired. At this time, terminal device 121 checks the value tag of the SIB1 included in the MIB in that cell and determines whether that value matches the value tag of the SIB1 it has stored. If the value of the value tag acquired from the MIB matches the value of the value tag it has stored, terminal device 121 can determine that the SIB1 information has not been updated from the stored information. For this reason, terminal device 121 can determine that it does not need to send a WUS to acquire the SIB1. On the other hand, if the value of the value tag obtained from the MIB does not match the value of the value tag it holds, the terminal device 121 may determine that the information in SIB1 has been updated from the information it holds and may send a WUS to obtain SIB1. Note that the value tag of SIB1 may be included in something other than the MIB. For example, the value tag of SIB1 may be included in the WUS configuration. The terminal device 121 may compare the value tag of SIB1 received in the WUS configuration with the value tag of SIB1 it holds and decide whether or not to send a WUS.Note that `value tag` is just an example, and any name of value used to determine the identity of SIB1 and WUS configuration may be used (i.e., any parameter where the same value is set if the settings are the same, and a different value is set if at least part of the settings are different).

[0072] Furthermore, when the terminal device 121 transmits a WUS to a base station device of an NES cell operating in a different frequency band while connected to any cell (while in the RRC connected state), it may transmit the WUS after setting a period of no communication, such as a Measurement gap. For example, the terminal device 121 may receive information from the connected base station device specifying a period during which it will not communicate with that base station device, and during that period, it may measure the SSB in the other frequency band. Then, the terminal device 121 may transmit the WUS using the resources specified in that SSB. However, even if the terminal device 121 transmits a WUS, if the WUS is not properly received by the base station device 111 of the NES cell, SIB1 will not be transmitted in the NES cell. It is also conceivable that even if a signal such as RAR is transmitted in the NES cell, the terminal device 121 may not be able to receive that signal. In such cases, terminal device 121 may retransmit the WUS until it successfully receives the SIB1. However, if the terminal device 121 stops communication in the connected cell as described above in order to retransmit the WUS, the efficiency of communication may decrease if the number of retransmissions increases. For this reason, for example, separate upper limits may be provided for the number of retransmissions in the RRC connected state and the number of retransmissions in the RRC idle state. In this case, these upper limits may be included in the WUS configuration and notified to terminal device 121. For example, parameters such as preambleTransMax_Connected, which indicates the upper limit of the number of WUS retransmissions during the RRC Connected state, and preambleTransMax_idle, which indicates the upper limit of the number of WUS retransmissions during the RRC idle state, may be set. Furthermore, the maximum number of retransmissions for each method may be defined as a number corresponding to RSRP. For example, in WUS configuration, information indicating the number of retransmissions (si-RequestResourcesRepetitionNum8) and threshold information determining whether or not to retransmit (rsrp-ThresholdMsg1-RepetitionNum8) may be transmitted to the terminal device 121.Subsequently, the terminal device 121 compares the measured RSRP value with a threshold value for determining whether or not to retransmit. If the RSRP value is less than the threshold value, it may determine the number of retransmissions using the value indicated by the information indicating the number of retransmissions. Here, the information regarding the threshold value for determining whether or not to retransmit may be notified to the terminal device 121 in an RRC reconfiguration message.

[0073] The terminal device 121 searches for a cell to reconnect to, for example, when it detects a radio link failure (RLF). At this time, if the terminal device 121 according to this embodiment finds a NES cell as the cell to reconnect to, holds a WUS configuration for that NES cell, and has obtained information from the base station device (for example, the one it was connected to before the RLF occurred) indicating permission to transmit the WUS at the time of reconnection, it can transmit the WUS as part of the reconnection process. After transmitting the WUS, the terminal device 121 receives the SIB1 and stores the information of the SIB1. Then, after storing the information of the SIB1, the terminal device 121 can perform conventional reconnection processing such as transmitting a RAP, receiving a RAR, and transmitting an RRCRReestablymentRequest. Furthermore, when the terminal device 121 transmits a WUS (RAP) during reconnection, it may notify the base station device of information indicating that an RRC message will be transmitted following the transmission of the WUS, thereby speeding up the reconnection process. In this case, the base station device that receives the WUS may transmit information regarding the PUSCH resource block to be used for transmitting the RRCReestableRequest to the RAR received after the transmission of the RAP corresponding to the WUS. Also, if the terminal device 121 has obtained information from the base station device (for example, the one it was connected to before the RLF occurred) indicating that the transmission of the WUS during reconnection is not permitted, it may exclude NES cells from the search target when searching for the cell to reconnect to.

[0074] Although an example of performing a reconnection operation using the WUS configuration stored by the terminal device 121 has been described, if the SIB1 information for that cell has been stored in advance, the terminal device 121 may perform conventional reconnection processing such as sending RAP, receiving RAR, and sending RRCReesteadRequest based on the stored SIB1 information. Furthermore, if the terminal device 121 receives an RRC reconfiguration message including reportCGI from the base station equipment of the cell to be reconnected after completing the reconnection process to a non-NES cell, it may create the report content to that base station equipment from the SIB1 information it holds. In addition, if the terminal device 121 detects an RLF, it may delete the stored WUS configuration information and SIB1 information. If the terminal device 121 has obtained information from the base station device indicating that WUS transmission is not permitted upon reconnection, it may delete this information. Alternatively, the terminal device 121 may delete this information unconditionally when RLF occurs. After that, the terminal device 121 may re-acquire the WUS configuration after reconnecting to a non-NES cell.

[0075] Furthermore, the terminal device 121 may be configured to perform the saving of the NES cell's SIB1 as described above as part of the Logged MDT (Minimization of Drive Test) function for optimizing the network. For example, in Figure 12, after the terminal device 121 receives the WUS configuration in S902, it may receive a log acquisition instruction for the Logged MDT function from the base station device 102. In that case, the terminal device 121 sends a WUS to the base station device 111 to receive the SIB1 and stores the information of the SIB1 associated with the PCI of the NES cell (for example, in the memory of the terminal device 121). Subsequently, the terminal device 121 moves within the range of cell A provided by the base station device 101, and when requested by the base station device 101 to report acquired logs, it reports the NES cell's SIB1 information, including the stored PLMN ID and NCGI, to the base station device 101. If there are multiple NES cells, the terminal device 121 may acquire and store the SIB1 information of those multiple NES cells and report it to the base station device all at once. In addition, when a log acquisition instruction is given, the base station device may notify the terminal device of the conditions for receiving the NES cell's SIB1. For example, the wireless quality of the NES cell, a list of PCIs of NES cells to be acquired, and a list of PCIs of NES cells to be excluded from acquisition may be notified from the base station device to the terminal device. Note that the log acquisition operation for NES cells can be performed using the procedure of the conventional Logged MDT function. In other words, log acquisition instructions, log reporting instructions, and log reporting can be performed using the LoggedMeasurementConfiguration, UEInformationRequest, and UEInformationResponse RRC messages, respectively. The base station device can use the SIB1 information of the NES cell obtained from the terminal device using the method described above to identify the PLMN ID and NCGI of the NES cell corresponding to PCI that is not recognized as an adjacent cell by the device itself, without sending an RRC reconfiguration message containing reportCGI to the terminal device, and can properly construct the NCR.

[0076] The embodiments described above may be used in any combination.

[0077] As described above, in this embodiment, in an environment where NES cells do not periodically transmit SIB1, base station equipment of a non-NES cell can appropriately construct an NCR using ANR. Therefore, it becomes possible to contribute to Goal 9 of the United Nations Sustainable Development Goals (SDGs), "Build resilient infrastructure, promote sustainable industrialization and foster innovation."

[0078] The invention is not limited to the embodiments described above, and various modifications and changes are possible within the scope of the gist of the invention.

[0079] This application claims priority based on Japanese Patent Application No. 2025-018510, filed on February 6, 2025, and all of its contents are incorporated herein by reference.

Claims

1. A terminal device comprising: receiving means for receiving first configuration information relating to a Wake Up Signal (WUS) for transmitting a System Information Block Type 1 (SIB1) in a second cell different from a first cell provided by the first base station device, which is connected to the terminal device and is in operation not to periodically transmit the SIB1; transmitting means for transmitting the WUS to a second base station device providing the second cell when a radio link failure is detected in the connection with the first base station device; and reconnection processing means for obtaining information on the SIB1 from the second base station device after the transmission of the WUS and performing a reconnection to the second base station device.

2. The terminal device according to claim 1, further comprising a holding means for holding the first setting information received by the receiving means and for continuing to hold the first setting information even after moving to a third cell provided by the third base station device.

3. The terminal device according to claim 2, wherein the holding means deletes the first setting information when a predetermined period of time has elapsed since it was held.

4. The terminal device according to claim 1, wherein the transmitting means transmits a random access preamble (RAP) as a Wake Up Signal (WUS) to the second base station device.

5. A control method performed by a terminal device, comprising: receiving first configuration information relating to a Wake Up Signal (WUS) for transmitting a System Information Block Type 1 (SIB1) in a second cell different from a first cell provided by the first base station device, which is operating in a manner in which a System Information Block Type 1 (SIB1) is not transmitted periodically, from a first base station device with which it is connected; transmitting the WUS to a second base station device providing the second cell when a radio link failure is detected in the connection with the first base station device; obtaining information about the SIB1 from the second base station device after transmitting the WUS; and performing a reconnection to the second base station device after obtaining the information about the SIB1.

6. A program for causing a computer installed in a terminal device to execute the control method described in claim 5.

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