Base station device, terminal device, control method, and program for efficient location registration

Abstract

To improve the efficiency of location registration processing. [Solution] A base station device acquires a list of area identifiers belonging to the same location registration area as the cell formed by the device itself, and information on the area identifiers of neighboring cells adjacent to the cell, determines whether the area identifiers of the neighboring cells are included in the list, and notifies the terminal device of information relating the information on the neighboring cells and the result of the determination.

Description

[Technical field]

[0001] The present invention relates to a technique for improving the efficiency of location registration in a cellular communication system. [Background technology]

[0002] In a fifth-generation (5G) cellular communication system, a logical network optimized for each service is configured as a network slice. A network slice may be configured only for a specific frequency. In this case, the network slices that can be provided for each frequency may differ even in the same location. When the network slices that can be provided for each frequency in the same location are different, a different Tracking Area Code (TAC) may be assigned to each frequency. Summary of the Invention [Problem to be solved by the invention]

[0003] A terminal device holds a list of Tracking Area Identities (TAIs) corresponding to Tracking Area Codes (TACs), and executes location registration processing when moving to a cell with a TAI that is not included in the list. In contrast, as described above, when a TAC is assigned to each frequency, even if the terminal device does not move geographically, the location registration processing may be executed by moving to a frequency with a TAI that is not included in the held TAI list. As a result, the load on the network may increase.

[0004] The present invention provides a technique for improving the efficiency of location registration processing. [Means for solving the problem]

[0005] A base station device according to one aspect of the present invention is a base station device that, for a cell formed by the base station device, A tracking area identity (TAI) including a plurality of TAIs including a tracking area identity (TAI) assigned to the TAI list Information indicating a neighboring cell adjacent to the cell, and information indicating the TAI assigned to the neighboring cell. An acquisition means for acquiring the The above Adjacent Cells The TAI assigned to However, TAI A determination means for determining whether the neighboring cell is included in the list, Show Information and A method for determining whether a terminal device deviates from a plurality of tracking areas specified by the TAI list by changing to the neighboring cell indicated by the information indicating the neighboring cell. The result of the above judgment Information showing Associate with And, A notification means for notifying a terminal device. The TAI list is composed of a plurality of TAIs assigned to the tracking area that can provide a predetermined network slice to the terminal device, and the acquisition means acquires the TAI list from a core network. do.

[0006] According to another aspect of the present invention, a terminal device receives a call from a base station device that constitutes a serving cell in which the terminal device is waiting. Information indicating neighboring cells adjacent to the serving cell; The serving cell A tracking area identity (TAI) including a plurality of TAIs including a tracking area identity (TAI) assigned to the TAI On the list The TAI assigned to the neighboring cell is Included or not Identifiable information and ,of Associated Prescribed Information From the base station device A receiving means for receiving the signal; Prescribed A setting means for setting a priority of the selection of the neighboring cell based on the information. The TAI list is composed of a plurality of TAIs assigned to the tracking area that can provide a predetermined network slice to the terminal device, and the TAI list is acquired by the base station device from a core network. . Effect of the Invention

[0007] According to the present invention, the efficiency of location registration processing can be improved. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a wireless communication system. [Diagram 2] FIG. 2 is a diagram illustrating an example of the hardware configuration of a base station device and a terminal device. [Diagram 3] FIG. 2 is a diagram illustrating an example of a functional configuration of a base station device. [Figure 4] FIG. 2 is a diagram illustrating an example of a functional configuration of a terminal device. [Diagram 5] FIG. 4 is a diagram illustrating a first example of a flow of processing performed by a base station device. [Figure 6] FIG. 11 is a diagram illustrating a first example of a processing flow executed by a terminal device. [Figure 7] FIG. 11 is a diagram illustrating a second example of the flow of processing performed by the base station device. [Figure 8] FIG. 11 is a diagram illustrating a second example of the flow of processing executed by the terminal device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims, and not all combinations of features described in the embodiments are essential to the invention. Two or more features among the multiple features described in the embodiments may be arbitrarily combined. In addition, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0010] (System Configuration) FIG. 1 shows a configuration example of a wireless communication system according to the present embodiment. In one example, this wireless communication system is a cellular wireless communication system for the fifth generation (5G) or an earlier or later generation. The wireless communication system includes a base station device 101 and a terminal device 103. The base station device 101 can form, for example, a cell 111 and a cell 112 that use different frequency ranges, and communicate with a terminal device 103 that is staying within the range of one of these cells. Note that the cell 111 and the cell 112 may have a common geographical range as a coverage area. In a standby state, the terminal device 103 can select one of the cells 111 and 112 (or a corresponding frequency) and reside therein. In addition, during a connection, the terminal device 103 can communicate with the base station device 101 through at least one of the cells 111 and 112. In addition, the wireless communication system can include another base station device 102 that forms a cell 121 and a cell 122 adjacent to the cell formed by the base station device 101. In the example of FIG. 1, only two base station devices and one terminal device are shown, but it goes without saying that there may be many more base station devices and terminal devices.

[0011] When the terminal device 103 moves to a cell having a TAI that is not included in the currently held Tracking Area Identity (TAI) list, it is necessary to perform a location registration process. Note that the TAI is identification information that can be specified based on a Tracking Area Code (TAC), and the TAI below may be read as a TAC. Note that the TAI in the following description may be read as a more general area identifier. That is, the TAI is merely one aspect of an area identifier, and the following discussion can be applied to any system in which location registration similar to that of a cellular communication system is performed. By the terminal device 103 performing the location registration process, the core network can specify the location of the terminal device 103 in tracking area units and call the terminal device 103 by transmitting a paging message to the entire range of the tracking area in which the terminal device 103 exists. Note that the terminal device 103 does not need to perform a location registration process while moving between cells having a TAI included in the currently held TAI list.

[0012] In this embodiment, as described above, it is assumed that the network slice that can be provided to the terminal device 103 may differ for each frequency. In this case, even in the same location, different TACs (TAIs) are assigned to different frequencies (different cells). For example, different TACs (TAIs) are assigned to the cells 111 and 112, and different TACs (TAIs) are assigned to the cells 121 and 122. Here, it is assumed that the terminal device 103 holds a TAI list that includes the TAIs of the cells 111 and 121 and does not include the TAIs of the cells 112 and 122 while residing in the cell 111, for example. Even if the terminal device 103 is not moving, it may move a frequency based on wireless quality or the like and change the residing cell from the cell 111 to the cell 112. In this case, the terminal device 103 determines that it has moved to the cell 112 corresponding to a TAI that is not included in the TAI list held by the terminal device itself, and executes a location registration process. Furthermore, when the terminal device 103 shifts the frequency again and enters the cell 111, it may be necessary to execute the location registration process again. Therefore, many location registration processes may be executed, which may unnecessarily waste many radio resources and increase the power consumption of the terminal device 103. In view of such circumstances, the present embodiment provides a mechanism for suppressing the number of location registration processes of the terminal device 103 and for efficiently executing the location registration process.

[0013] In one example, the base station device 101 and the base station device 102 acquire, for a cell formed by the own device, a list of area identifiers (e.g., a TAI list) belonging to the same location registration area as the cell, and area identifier information (e.g., a TAC or TAI) of adjacent cells adjacent to the cell. The base station device 101 acquires, for example, a first list of area identifiers belonging to the same location registration area as the cell 111 formed by the own device, a second list of area identifiers belonging to the same location registration area as the cell 112 formed by the own device, and area identifiers of the cells 121 and 122 formed by the base station device 102. In addition, the base station device 102 acquires, for example, a third list of area identifiers belonging to the same location registration area as the cell 121 formed by the own device, a fourth list of area identifiers belonging to the same location registration area as the cell 122 formed by the own device, and area identifiers of the cells 111 and 112 formed by the base station device 101. Then, the base station device 101 and the base station device 102 determine whether or not the area identifiers of the neighboring cells adjacent to the cell formed by the base station device 101 and the base station device 102 are included in the list corresponding to the cell. For example, the base station device 101 determines whether or not the area identifiers of the cells 121 and 122, and further the cell 112 are included in the first list corresponding to the cell 111.

[0014] When notifying the terminal device of the information indicating the neighboring cells, the base station device 101 and the base station device 102 transmit the information by adding information indicating the result of the determination as to whether or not each of the neighboring cells is included in the list corresponding to the cell formed by the base station device 101. For example, the base station device 101 notifies the terminal device 103 of information indicating that the cells 112, 121, and 122 exist as neighboring cells in the cell 111, and at that time, notifies the terminal device 103 of information indicating whether or not the area identifiers of those cells are included in the list of area identifiers belonging to the same location registration area as the cell 111. Note that, in the cell 112, the base station device 101 notifies the terminal device 103 of information indicating that the cells 111, 121, and 122 exist as neighboring cells and information indicating whether or not the area identifiers of those cells are included in the list of area identifiers belonging to the same location registration area as the cell 112. For example, information indicating whether the list of area identifiers belonging to the same location registration area as the cell (e.g., cell 111) to which information is transmitted includes the area identifiers of adjacent cells (e.g., cell 112, cell 121, cell 122) is indicated by 1-bit information. In one example, if the list of area identifiers belonging to the same location registration area as the cell to which information is transmitted includes the area identifiers of adjacent cells, "0" is included in the notified information, and if not, "1" is included.

[0015] The information indicating the neighboring cell may include, for example, a cell identifier. In this case, for example, the cell identifier is notified in association with a bit indicating whether the area identifier of the cell is included in a list of area identifiers belonging to the same location registration area as the cell to which the information is transmitted. This allows a serving terminal device to identify a neighboring cell for which location registration processing is required (i.e., a cell that deviates from the location registration area in which the serving cell is included). As a result, for example, when the terminal device reselects a cell, frequent location registration processing can be prevented by preventing the terminal device from transitioning to a cell that requires location registration processing.

[0016] Furthermore, the information indicating the neighboring cell may include information on the frequency used in the neighboring cell. That is, the base station device 101 and the base station device 102 may notify the terminal device of information indicating the frequency used in one or more cells formed by other base station devices and information associating the area identifier of the cell corresponding to the frequency. This allows a currently serving terminal device to identify a frequency of a moving destination where location registration processing is required (i.e., the moving destination is a location registration area including the currently serving cell). As a result, for example, when the terminal device reselects a cell, frequent location registration processing can be prevented by preventing the terminal device from transitioning to a cell of a frequency that requires location registration processing.

[0017] In addition, the base station device 101 and the base station device 102 may notify information associating a frequency with whether or not location registration is required for movement to the frequency, without identifying each of the neighboring cells, based on, for example, the relationship between the frequency used in each of the neighboring cells relative to the cell formed by the own device and whether the area identifier of the neighboring cell is included in the list of area identifiers corresponding to the location registration area including the cell formed by the own device. For example, in a first frequency, when all of the neighboring cells have area identifiers belonging to the location registration area of ​​the cell transmitting information, the frequency is associated with information indicating that location registration is not required for movement to the first frequency. Also, for example, in a second frequency, when all of the neighboring cells have area identifiers that do not belong to the location registration area of ​​the cell transmitting information, the frequency is associated with information indicating that location registration is required for movement to the second frequency. Also, for example, in a third frequency, when a predetermined ratio or more of the neighboring cells have area identifiers belonging to the location registration area of ​​the cell transmitting information, the frequency is associated with information indicating that location registration is not required or is highly likely not to be required for movement to the third frequency. Also, for example, in the fourth frequency, when only a predetermined ratio of adjacent cells have area identifiers belonging to the location registration area of ​​the cell transmitting information, the movement to the fourth frequency is associated with information indicating that location registration is required or is highly likely to be required. In this case, the base station device 101 or the base station device 102 notifies the currently located terminal device of information associated with information indicating the frequency and information indicating whether or not the movement to that frequency requires location registration processing (i.e., whether or not the movement will depart from the location registration area to which the cell transmitting information belongs) or information indicating whether or not the movement is highly likely to require location registration processing. In this case, the information regarding the necessity of location registration processing can be expressed by multiple bits.

[0018] In addition, the base station device 101 and the base station device 102 may acquire, for example, from the core network, a list of area identifiers belonging to the same location registration area as the cell formed by the base station device. In this way, the base station device can notify the terminal device of appropriate information by acquiring the latest information from the core network. For example, the base station device 101 and the base station device 102 transmit an NG SETUP REQUEST message to establish an interface for connection with the core network, and may acquire the list information by an NG SETUP RESPONSE message that is a response to the message. In addition, the base station device 101 and the base station device 102 may acquire the list information by an AMF CONFIGURATION UPDATE message used for updating settings related to service slices, etc. In addition, the base station device 101 and the base station device 102 may acquire the list information via a message other than these. In addition, the list information may be manually set when the base station device 101 and the base station device 102 are installed, and the list information does not necessarily have to be acquired from the core network.

[0019] The base station device 101 and the base station device 102 may obtain area identifier information of adjacent cells from other base station devices that form the adjacent cells. By obtaining area identifier information from adjacent base station devices, when the area identifier is changed due to an update of the network slice provided by the adjacent base station device, the base station device can notify appropriate information in accordance with the change. For example, the base station device 101 may obtain area identifier information for each of the cells 121 and 122 from the base station device 102. The base station device 101 and the base station device 102 may establish an Xn interface for communication with the adjacent base station device, and may obtain area identifier information of the cell formed by the adjacent base station device from the adjacent base station device by an XN SETUP REQUEST message or an XN SETUP RESPONSE message transmitted and received at that time. Furthermore, the base station device 101 and the base station device 102 may obtain area identifier information of the cell formed by the other base station device by an NG-RAN NODE CONFIGURATION UPDATE message or an NG-RAN NODE CONFIGURATION UPDATE ACKNOWLEDGE message transmitted and received to update application level configuration data required for cooperative operation between the two base station devices via the Xn interface. Note that these are only examples, and area identifier information of the cell formed by the adjacent base station device may be obtained by other messages. Furthermore, the base station device 101 and the base station device 102 may obtain area identifier information of the adjacent cell from the core network.

[0020] The information may be transmitted using, for example, a system information block (SIB). That is, the base station device 101 and the base station device 102 may transmit the above-mentioned information by a broadcast signal so that terminal devices present in the cell formed by the base station device can obtain the information. The base station device 101 and the base station device 102 may transmit the above-mentioned information by a message (for example, a radio resource control (RRC) message such as RRCReconfiguration, RRCResume, or RRCRelease) to a terminal device that is to become connected or to a terminal device that is to become disconnected from a connected state.

[0021] For example, when the terminal device 103 receives the above-mentioned information from the base station device 101 that forms the serving cell, the terminal device 103 sets a cell having an area identifier that belongs to the same location registration area as the currently serving cell as a cell with a high selection priority. The selection priority is an index that indicates that the higher the value, the more likely the cell is to be selected by the terminal device 103. For example, when the terminal device 103 is serving the cell 111, if the list of area identifiers that belong to the same location registration area as the cell 111 includes the area identifier of the cell 121 but does not include the area identifiers of the cells 112 and 122, the terminal device 103 increases the priority of the cell 121 and / or decreases the priority of the cells 112 and 122. Note that, for example, when the terminal device 103 acquires information indicating the cell identifier of each cell and whether or not a movement to that cell requires a location registration process (i.e., whether or not the movement deviates from the location registration area including the area identifier of the serving cell), the terminal device 103 may set a priority for each cell. Furthermore, when the terminal device 103 acquires information indicating, for example, a frequency and whether or not movement to that frequency requires location registration processing (i.e., whether or not it deviates from a location registration area including an area identifier of a serving cell), the terminal device 103 may set a priority for each frequency. For example, when location registration processing is not required as long as the first frequency is used, the terminal device 103 sets the priority of the first frequency high. Furthermore, when location registration processing is definitely required when the second frequency is used, the terminal device 103 sets the priority of the second frequency low. Furthermore, when location registration processing is required with a predetermined probability when the third frequency is used, the terminal device 103 may set the priority of the third frequency to medium.

[0022] The terminal device 103 may receive broadcast information (for example, a master information block (MIB) or SIB1) by giving priority to a neighboring cell with a high priority, for example. The terminal device may receive broadcast information transmitted by a neighboring cell without receiving the above-mentioned information, and determine that a location registration process is necessary by checking the broadcast information (for example, SIB1), and as a result, select another cell. However, in this case, it is necessary to check the broadcast information of the neighboring cell each time, so that the time until the cell selection is completed is extended. On the other hand, according to the method of the present embodiment, the terminal device can recognize which neighboring cell requires location registration process when moving based on information transmitted by the serving cell, without receiving the broadcast information of the neighboring cell. Therefore, the frequency of location registration process can be reduced by a short process. Note that the terminal device 103 may further perform the prioritization according to the present embodiment on the existing prioritization. For example, the terminal device 103 may lower the priority set by the conventional method by a predetermined step for a cell requiring location registration process, or set the priority level to the lowest value. On the other hand, for cells that do not require location registration processing, the terminal device 103 can use the priorities set by the conventional method as they are. This allows the terminal device 103 to preferentially select cells that do not require location registration processing while using the priorities set by the conventional method.

[0023] Also, the terminal device 103 may start searching for a cell with high priority based on the wireless quality of the serving cell becoming equal to or lower than a first level, and may start searching for a cell with intermediate priority based on the wireless quality becoming equal to or lower than a second level lower than the first level. Also, the terminal device 103 may execute a process of searching for a cell with low priority when the wireless quality of the serving cell becomes equal to or lower than a second level and a cell with intermediate priority is not found. That is, the terminal device 103 may set a condition for starting a search for a cell corresponding to the priority based on the set priority. Also, the terminal device 103 may set a condition for moving to a found cell, for example. That is, the terminal device 103 may execute a setting such that the terminal device 103 moves to a cell with high priority when its wireless quality exceeds a third level, and does not move to a cell with low priority unless its wireless quality exceeds a fourth level higher than the third level.

[0024] The terminal device 103 may receive the above-mentioned information from the core network, for example, while operating in a connected state. That is, the above-mentioned information may be generated in the core network, not by the base station device.

[0025] In the above embodiment, the base station device (or core network) determines whether the location registration process is necessary when the neighboring cell moves from the cell to which information is transmitted, and notifies the neighboring cell, but the present invention is not limited to this. For example, when notifying the terminal device of the list of neighboring cells, the base station device (or core network) may notify the TAC (or TAI) of the neighboring cell. That is, the base station device may obtain information on the area identifier of the neighboring cell adjacent to the cell formed by the base station device, and may notify the terminal device of the area identifier of the neighboring cell in association with information indicating the neighboring cell. Then, when the terminal device receives the information, the terminal device may determine whether the area identifier of the neighboring cell is included in a list of area identifiers (e.g., a TAI list) belonging to the same location registration area as the serving cell, which is held by the base station device. Then, the terminal device may set a selection priority for each of the neighboring cells based on the result of the determination. That is, the terminal device may perform the determination performed by the base station device in the above example. Note that the features other than the entity that performs the determination may be the same as those of the above example.

[0026] In this way, the terminal device is notified of information indicating whether a location registration process is required for each adjacent cell when the terminal device moves to the adjacent cell, and the terminal device preferentially selects a cell that does not require a location registration process, thereby preventing frequent location registration processes and enabling efficient location registration to be performed. In addition, according to this, the terminal device can continuously select a cell with an area identifier corresponding to the network slice to be executed. Note that, for example, when the number of terminal devices belonging to a certain location registration area is greater than the number of terminal devices belonging to another location registration area, the information notified by the base station device may be set so that a cell requiring a location registration process is preferentially selected in order to encourage the terminal device to move to the other location registration area.

[0027] In the above example, the process while the terminal device is in standby has been described, but the selection of the handover destination cell may be performed according to the same criteria even when the terminal device is connected. For example, the terminal device may set a handover threshold value so that a handover to a cell that requires a location registration process is less likely to occur than a handover to a cell that does not require a location registration process. That is, when a handover to a first neighboring cell that does not require a location registration process is performed in response to the wireless quality of the first neighboring cell being higher than the wireless quality of the connected cell by a first level, a handover to a second neighboring cell that requires a location registration process may not be performed unless the wireless quality of the second neighboring cell is higher than the wireless quality of the connected cell by a second level that is higher than the first level. In addition, for example, even if a cell requires a location registration process, if a cell exists that supports the network slice with which the terminal device is communicating, the terminal device may be handed over to that cell. On the other hand, when there is no candidate cell for the handover destination that supports the network slice in which the terminal device is communicating, the base station device may execute a handover involving a change to another network slice for the terminal device. Also, when there is no candidate cell for the handover destination that supports the network slice in which the terminal device is communicating, the base station device may notify the terminal device that communication will be terminated without handover. As described above, the base station device may notify the terminal device of the handover threshold, and the terminal device may determine the threshold, or the base station device may notify the terminal device of the handover threshold, and the radio quality of the candidate cell reported by the terminal device may be compared with the handover threshold held by the base station device to determine the candidate cell.

[0028] (Device Configuration) Next, a hardware configuration example of a communication device (for example, the base station device 101, the base station device 102, and the terminal device 103) that executes the above-mentioned processing will be described with reference to FIG. 2. In one example, the communication device includes a processor 201, a ROM 202, a RAM 203, a storage device 204, and a communication circuit 205. The processor 201 is a computer that includes one or more processing circuits such as a general-purpose CPU (Central Processing Unit) or an ASIC (Application Specific Integrated Circuit), and executes the overall processing of the communication device and each of the above-mentioned processing by reading and executing a program stored in the ROM 202 or the storage device 204. The ROM 202 is a read-only memory that stores information such as a program related to the processing executed by the communication device and various parameters. The RAM 203 functions as a workspace when the processor 201 executes a program, and is a random access memory that stores temporary information. The storage device 204 is, for example, configured by a removable external storage device. The communication circuit 205 is, for example, configured by a circuit for 5G wireless communication. 2 illustrates one communication circuit 205, the communication device may have multiple communication circuits. For example, the communication device may have separate communication circuits 205 for each of multiple available frequency bands. The communication device may also have a common communication circuit 205 for at least some of the multiple frequency bands. For example, the terminal device 103 may have not only the communication circuit 205 for cellular communication, but also a communication circuit 205 compatible with other wireless communication standards such as wireless LAN.

[0029] FIG. 3 is a diagram showing an example of the functional configuration of a base station device (base station device 101 and base station device 102). The base station device includes, for example, an information acquisition unit 301, a determination unit 302, and an information notification unit 303. Note that FIG. 3 shows only functions particularly related to this embodiment, and other various functions that the base station device may have are omitted from the illustration. For example, the base station device naturally has other functions that a base station device in a cellular communication system generally has. Also, the functional blocks in FIG. 3 are shown in a schematic manner, and each functional block may be integrated and realized, or may be further subdivided. Also, each function in FIG. 3 may be realized, for example, by the processor 201 executing a program stored in the ROM 202 or the storage device 204, or may be realized, for example, by a processor present in the communication circuit 205 executing a predetermined software. Note that the details of the processing performed by each functional unit will not be described here in detail, and only the rough functions will be outlined.

[0030] The information acquisition unit 301 acquires a list of area identifiers (for example, a TAI list) belonging to the same location registration area as the cell formed by the base station device itself, and information on the area identifiers of neighboring cells adjacent to the cell. Note that the information on the area identifiers of the neighboring cells may acquire, for example, information associating the cell identifiers and area identifiers of the neighboring cells. The information acquisition unit 301 may also acquire, for example, information associating the frequency used in the neighboring cell with the area identifier at that frequency, as the information on the area identifiers of the neighboring cells. The determination unit 302 determines whether or not the area identifier of the neighboring cell is included in the acquired list for each of the neighboring cells. The information notification unit 303 notifies the terminal device of information that associates information indicating the neighboring cell (for example, the cell identifier of the neighboring cell and the frequency used in the neighboring cell) with the determination result in the determination unit 302. Note that the information notification unit 303 may also notify the terminal device of the list of neighboring cells and the area identifiers of the neighboring cells. In this case, the determination that was described above as being performed by the determining unit 302 is performed by the terminal device, so that the base station device does not need to have the determining unit 302.

[0031] FIG. 4 is a diagram showing an example of the functional configuration of a terminal device (terminal device 103). The terminal device includes, for example, an information receiving unit 401, a specifying unit 402, and a priority setting unit 403. Note that FIG. 4 shows only functions particularly related to this embodiment, and other various functions that the terminal device may have are omitted from the illustration. For example, the terminal device naturally has other functions that a terminal device in a cellular communication system generally has. Also, the functional blocks in FIG. 4 are shown in a schematic manner, and each functional block may be integrated and realized, or may be further subdivided. Also, each function in FIG. 4 may be realized, for example, by the processor 201 executing a program stored in the ROM 202 or the storage device 204, or may be realized, for example, by a processor present in the communication circuit 205 executing a predetermined software. Note that the details of the processes executed by each functional unit will not be described in detail here, and only the rough functions will be outlined.

[0032] The information receiving unit 401 receives information notified by the information notifying unit 303 of the base station device. The information receiving unit 401 receives, for example, information indicating whether an area identifier of a neighboring cell adjacent to a serving cell is included in a list of area identifiers belonging to the same location registration area as the serving cell, and information indicating the neighboring cell, which are associated with each other. The information receiving unit 401 may also receive, for example, information indicating a neighboring cell adjacent to a serving cell, and information on the area identifier of the neighboring cell, which are associated with each other. The identifying unit 402 identifies, based on the received information, whether an area identifier of the neighboring cell is included in a list of area identifiers belonging to the same location registration area as the serving cell. For example, when the determination of whether an area identifier of the neighboring cell is included in a list of area identifiers belonging to the same location registration area as the serving cell is performed by the base station device, the identifying unit 402 may perform this identification by checking the received information. Furthermore, for example, when the device itself determines whether the area identifier of the neighboring cell is included in a list of area identifiers belonging to the same location registration area as the serving cell, the identifying unit 402 performs this identification by determining whether the received area identifier is included in a list (e.g., a TAI list) held by the device itself. The setting unit 403 sets a selection priority for each neighboring cell based on the identification result of the identifying unit 402. For example, when the area identifier of the neighboring cell is not included in the list of area identifiers belonging to the same location registration area as the serving cell, the setting unit 403 can lower the priority so that the neighboring cell is less likely to be selected.

[0033] (Processing flow) Next, the flow of the processing executed by the base station device and the terminal device will be outlined. Note that the following description is merely an example, and the detailed operations etc. described above will not be described again here.

[0034] Figures 5 and 6 show examples of the flow of processing when a base station device (or a core network) determines whether or not an area identifier of a neighboring cell adjacent to a cell formed by the base station device is included in a list of area identifiers belonging to the same location registration area as the cell formed by the base station device. Note that Figure 5 shows an example of the flow of processing performed by the base station device, and Figure 6 shows an example of the flow of processing performed by the terminal device.

[0035] First, the base station device acquires a list of area identifiers belonging to the same location registration area as the cell formed by the own device, and area identifiers of adjacent cells (S501). The base station device may acquire the list from, for example, a core network, and may acquire the area identifiers of the adjacent cells from other base station devices forming the adjacent cells. Note that, when the base station device forms multiple cells and the cells have different area identifiers, it may acquire lists for each of the multiple cells. The base station device determines whether or not the area identifier of each adjacent cell is included in the acquired list (S502). Then, for each adjacent cell, the base station device generates information that associates information indicating the adjacent cell (for example, a cell identifier or a frequency) with the determination result of S502, and notifies the terminal device by, for example, an SIB (S503). Note that, when the base station device forms multiple cells, the base station device executes notification of the information of S503 in each of the multiple cells. Note that the multiple cells may correspond to different area identifiers, and therefore the information notified in each cell may differ from each other.

[0036] When the terminal device receives the information transmitted by the base station device in S503 (S601), the terminal device refers to the information and identifies whether the list of area identifiers belonging to the same location registration area as the serving cell includes the area identifier of the neighboring cell adjacent to the serving cell (S602). Then, the terminal device sets the selection priority of each neighboring cell based on the result of the identification (S603). For example, if the area identifier of the neighboring cell is included in the list, the terminal device may set the selection priority of the neighboring cell relatively high, and if the area identifier of the neighboring cell is not included in the list, the terminal device may set the selection priority of the neighboring cell relatively low. Note that the neighboring cell here includes a cell formed by the same base station device as the serving cell but different from the serving cell. Note that the information indicating the neighboring cell may indicate a frequency, and the terminal device may set the selection priority for each frequency.

[0037] Figures 7 and 8 show examples of the flow of processing when a terminal device determines whether or not the list of area identifiers belonging to the same location registration area as the serving cell includes the area identifier of a neighboring cell adjacent to the serving cell. Note that Figure 7 shows an example of the flow of processing executed by a base station device, and Figure 8 shows an example of the flow of processing executed by a terminal device.

[0038] In this process, the base station device acquires information indicating the area identifier of the neighboring cell from another base station device corresponding to the neighboring cell adjacent to the cell formed by the base station device (S701). Then, the base station device transmits information indicating the neighboring cell and information associating the area identifier of the neighboring cell to the terminal device (S702). When the terminal device receives this information in the serving cell (S801), the terminal device refers to a list of area identifiers belonging to the same location registration area as the serving cell, which is acquired and held at the time of the previous location registration, for example, and identifies whether the area identifier of the neighboring cell is included in the list (S802). Then, the terminal device sets the selection priority of each neighboring cell based on the identification result, similar to S603 (S803). Note that the neighboring cell here includes a cell formed by the same base station device as the serving cell and different from the serving cell. Note that the information indicating the neighboring cell may indicate a frequency, and the terminal device may set the selection priority for each frequency.

[0039] As described above, the priority of whether or not the neighboring cell should be selected is determined based on whether or not the area identifier of the neighboring cell is included in the list of area identifiers belonging to the same location registration area as the serving cell. This allows the terminal device to recognize whether or not location registration processing is required by moving to each neighboring cell without having to obtain notification information from the neighboring cell. This allows the terminal device to quickly select, for example, a cell that does not require location registration, preventing frequent location registration processing and improving the efficiency of location registration processing in the entire system.

[0040] Furthermore, the present invention will make it possible, for example, to improve the efficiency of communications infrastructure, thereby contributing to Goal 9 of the Sustainable Development Goals (SDGs) led by the United Nations, which is to "build resilient infrastructure, promote industry, innovation and infrastructure."

[0041] The invention is not limited to the above-described embodiment, and various modifications and variations are possible within the scope of the gist of the invention.

Claims

1. A base station device, An acquisition means for acquiring a TAI list including a plurality of Tracking Area Identities (TAIs) including a TAI assigned to a cell formed by the base station device, information indicating neighboring cells adjacent to the cell, and information indicating the TAI assigned to the neighboring cells; A determination means for determining whether the TAI assigned to the neighboring cell is included in the TAI list; a notification means for associating information indicating the neighboring cell with information indicating a result of the determination by which the terminal device can determine whether or not the terminal device will depart from a plurality of tracking areas identified by the TAI list by changing to the neighboring cell indicated by the information indicating the neighboring cell, and notifying the terminal device of the association; having The TAI list is composed of a plurality of TAIs assigned to the tracking area capable of providing a predetermined network slice to the terminal device, The acquiring means acquires the TAI list from a core network. A base station device comprising:

2. 2. The base station device according to claim 1, wherein the acquisition means acquires the TAI list by a NG SETUP RESPONSE message or an AMF CONFIGURATION UPDATE message.

3. The base station device according to claim 1 or 2, wherein the information indicating the neighboring cell and the information indicating the result of the determination are associated with each other by a bit indicating the result of the determination for each piece of information indicating the neighboring cell.

4. The base station device according to claim 1 , wherein the information indicating the neighboring cell includes a cell identifier of the neighboring cell.

5. The base station device according to claim 1 , wherein the information indicating the neighboring cell includes information indicating a frequency used in the neighboring cell.

6. The base station device according to claim 1 , wherein the acquisition means acquires information indicating the TAI assigned to the neighboring cell from another base station device that forms the neighboring cell.

7. The base station device according to claim 6, characterized in that the acquisition means acquires information indicating the TAI assigned to the neighboring cell by an XN SETUP REQUEST message, an XN SETUP RESPONSE message, an NG-RAN NODE CONFIGURATION UPDATE message, or an NG-RAN NODE CONFIGURATION UPDATE ACKNOWLEDGE message.

8. The base station apparatus according to claim 1 , wherein the notification unit performs the notification by a system information block (SIB).

9. A terminal device, a receiving means for receiving, from a base station device which constitutes a serving cell in which the terminal device is waiting, information indicating a neighboring cell adjacent to the serving cell, and information capable of identifying whether a Tracking Area Identity (TAI) assigned to the serving cell is included in a TAI list including a plurality of TAIs including the TAI assigned to the serving cell; and A setting means for setting a priority of the selection of the neighboring cell based on the predetermined information, The TAI list is composed of a plurality of TAIs assigned to the tracking area capable of providing a predetermined network slice to the terminal device, The TAI list is obtained by the base station device from a core network. A terminal device comprising:

10. The terminal device according to claim 9 , wherein the predetermined information includes, for each piece of information indicating a neighboring cell, a bit indicating whether the TAI assigned to the neighboring cell is included in the TAI list.

11. The terminal device according to claim 9 or 10, characterized in that the information indicating the neighboring cell includes a cell identifier of the neighboring cell.

12. The terminal device according to claim 9 , wherein the information indicating the neighboring cell includes information indicating a frequency used in the neighboring cell.

13. 13. The terminal device according to claim 9, wherein the receiving means receives the predetermined information by a system information block (SIB).

14. The terminal device according to any one of claims 9 to 13, characterized in that the setting means sets a priority when the TAI list includes the TAI assigned to the neighboring cell higher than a priority when the TAI list does not include the TAI assigned to the neighboring cell.

15. The terminal device according to any one of claims 9 to 14, characterized in that the setting means sets a condition for starting a search for a cell corresponding to the priority or a condition for moving to a cell corresponding to the priority based on the set priority.

16. A control method executed by a base station device, comprising: Acquiring a Tracking Area Identity (TAI) list including a plurality of TAIs including a TAI assigned to a cell formed by the base station device, information indicating neighboring cells adjacent to the cell, and information indicating the TAI assigned to the neighboring cells; determining whether the TAI assigned to the neighboring cell is included in the TAI list; and notifying the terminal device of the result of the determination by which the terminal device can determine whether or not the terminal device will depart from a plurality of tracking areas specified by the TAI list by changing to the neighboring cell indicated by the information indicating the neighboring cell, the result of the determination being associated with the information indicating the neighboring cell, The TAI list is composed of a plurality of TAIs assigned to the tracking area capable of providing a predetermined network slice to the terminal device, The TAI list is obtained from a core network. A control method comprising:

17. A control method executed by a terminal device, comprising: receiving, from a base station device which constitutes a serving cell in which the terminal device is waiting, information indicating a neighboring cell adjacent to the serving cell and information capable of identifying whether a Tracking Area Identity (TAI) assigned to the serving cell is included in a TAI list including a plurality of TAIs including the TAI assigned to the serving cell; and setting a priority of the selection of the neighboring cell based on the predetermined information; The TAI list is composed of a plurality of TAIs assigned to the tracking area capable of providing a predetermined network slice to the terminal device, The TAI list is obtained by the base station device from a core network. A control method comprising:

18. A program for causing a computer to operate as the base station device according to any one of claims 1 to 8.

19. A program for causing a computer to operate as the terminal device according to any one of claims 9 to 15.

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